Article Library

Articles contributed by the members for publication in the Runner Tracks - The Newsletter of the IDNIYRA.

History of the DN

Early history of the DN (Blue Streak 60) Iceboat

by: Paul Goodwin

I was lucky enough to befriend one of the original builders of the DN iceboat, Don Daller. Don was a great guy, always cheerful, and came to every swap meet with a box full of early pictures and articles about iceboating. When he finally got to where he could no longer carry his iceboat to the ice, he sold me his boat and transferred the sail number to me. I'm proud to sail with number 46, and will always remember Don.

Later, as Don's health started failing, he asked me to take posession of his collection of iceboat articles. For several years I brought the binders to swap meets, but the pages were getting old and some of the articles ended up missing. I always wanted to preserve some of those articles, and this is a start.

What we call the DN Iceboat started out with humble beginnings at the Detroit News hobby shop in the mid 1930's. The original design was a collaboration between master woodworker Archie Arrol and iceboaters Joseph Lodge and Norman Jarrait. Times were tough, with the US in a deep depression, and most iceboats were expensive toys of the rich and famous.

Joe Lodge and Norm Jarrait saw a need for an inexpensive, home-buildable iceboat that could be built out of common lumber and simple hardware. They designed the new iceboat so one person could load it on the roof of a car, or fit it in the bed of a pickup truck. It was Joe Lodge's idea to make the new iceboat a front-steerer. They called their boat the Blue Streak 60.

Archie, who was the head of the Detroit News hobby shop and had been building model yachts for years, worked with Joe and Norm in 1936 to build the first Blue Streak 60.

Archie Arrol at work in the Detroit News hobby shop

The first Blue Streak performed very well, especially in light wind. On the first day out on Lake St. Clair in the winter of '36, while the big boats like Deuce, Bernida, and Flying Dutchman couldn't move, the Blue Streak surprised the other iceboaters the way she could sail with hardly any wind.

A Blue Streak 60 on Lake St. Clair

In 1937 a group of about 50 wanna-be iceboaters got together at the Detroit News hobby shop, and for the sum of $32 were supplied with all the materials needed to build a Blue Streak 60, including a sail built by Howard Boston. In those days, $32 was a lot of money, at the time Don Daller was working for $0.50 an hour, three days a week. They scrounged parts where they could - the steering was accomplished with '34 Ford brake rods, rigging was galvanized steel wire from the local hardware store, no swaged fittings here - the wires were twisted into loops and soldered for security. The mast didn't have a halyard, you simply cleated the sail at the top and bottom of the mast and stood the whole rig up on the boat. The mast had a cut-off lag bolt in the bottom which fit into a hole in the deck - no ball and socket needed. Runners were angle iron on white oak bodies.

Unfortunately most of the boats built in 1937 broke up in the first season due to some design deficiencies. Joe and Norm redesigned the Blue Streak 60, and the same group of builders got together to build a second set of iceboats in 1938. Some of the '38 boats are still around, and at least one still gets out on the lake occasionally. As seen in the picture below, sailors in the early days didn't even take off the plank for transport! Also note the front runner, the second set of runners the group built (the first set were angles) were T-irons.

Some interesting things to note on the original "DN" (see the picture below):

  • There was originally only one sheet block on the rear deck of the Blue Streak - a 2:1 mainsheet purchase. Later another block was added to the boom to make a 3:1 puchase, and then eventually a second block on the deck for 4:1 - the same as on todays DN.
  • The mainsheet went through a single turning block on the mast, not on the boom or tiller post, and no ratchet block!
  • The mainsheet didn't provide any downhaul on the luff of the sail, instead the luff rope went through a hole in the boom jaw and was tied to a cleat.

Over the years the design was modified at the whim of the builders, and the name was changed to the DN 60. A group of DN sailors got together in 1953 at Clifford Cartwright's house on Cass Lake and outined a Constitution. The first Specifications were drawn up on the wall of Cartwright's basement shop, where many of the original specs are still evident today.

Note this winning Blue Streak 60 with curved deck, and enclosed cockpit

Bill Sarns drew up the first set of "modern" plans and the DN class adopted them as the Official Plans. Other design changes slowly made their way into the DN. Some changes stood the test of time, while others faded into history, like Chuck Cartwright's mini runner on the tail block - a solution to a problem caused by the ultra-flexible planks favored at the time.

The next big change was inspired by Jan Gougeon - which moved the widest point of the hull from the middle (just behind the mast step) to the plank. The Gougeon "wedge" design has been the basis for all other DN designs since it's introduction. Actually Jan's design was preceded by Chuck Cartwright's "Banjo Boat", which was narrow all the way to the front of the cockpit, then flaired out around the skipper. Chuck won the Annual Regatta (now the North American Championship) with the Banjo Boat, but was disqualified because the design was too radical.

Here is a partial list of the first builders of the Blue Streak. The list is not complete, but it's the only record I could find...

Boat # Boat Name Builder/Skipper
9 Skram Joe Schermack
11 Defensor Jack Moran
21 Blue Hue Walter Katz
32 Venus Maurice Robinson
38   Warren Dowling
46 Dawn Don Daller
65   Ralph Soden / Leo Kerwin
    Al Pochelon
  Scotty Howard MacDougall
    Merle (Herb) Chandler
    Norman J Nicholl
    Art Neffy
  Hody Howard Ternes
    Russ Johnson
    George Armstrong

I managed to locate a vintage set of blueprints for the original Blue Streak 60 and scanned them. With much labor, I was able to restore the scans to near perfect condition. For an insight into how the original DN was built, check out the scans below...

Original Blue Streak 60 blueprints - circa 1938

Note: These blueprints are reproduced to provide an historic perspective to the modern DN. Under no circumstances should a person build an iceboat using these plans in the 21st century.

Click on the image to see a LARGE version (over 2 MB each)
Blue Streak - sheet 1

Blue Streak - sheet 2

A Brief History of the DN Ice Boat

by Don Daller (the original DN 46)

The March 1996 edition of Runner Tracks took me back to 1937. (Please tell Richard Saltonstall it wasn’t 1939!)

I have not seen anything like a history of the DN published in Runner Tracks, or a library book published of DN history. Several books have been published about the big Rear Steerers racing the trains along the Hudson River a hundred years ago, and I read them over to experience the thrills of sailing on ice. Now I will try to compose a short history of the DN as I remember it.

In 1934, I had my first iceboat ride in a homemade Rear Steerer in Minneapolis. I almost froze to death because I was not dressed for it, but the "bug bit me." In the fall of 1937, the Detroit News published an article in the Sports Section asking for volunteers to attend a workshop for several nights. Each volunteer was to build an iceboat called a DN-60, a one-person boat with 60 square feet of sail. About 50 men and teen-aged boys signed up and agreed to attend and use the Detroit News carpentry shop above the garage to cut wood, bend iron, glue sections of fir, build jigs and fixtures, help each other and listen to Archie Arroll, the teacher, etc. The cost would be about $50 (a lot of money in those depression days since we were working for about $0.50 an hour only three days a week.) In a few months, we would be iceboating four days a week.....HOORAY!!!

The $50 would include all the wood, sail, foundry-poured castings for runner chocks, steering posts, etc. 1934 Ford steering rods could be salvaged at auto junk yards. We learned a lot from Archie, Art Jarrett and Joe Lodge, as sponsors and helpers. They carefully purchased supplies and helped guide us in building the fleet of 1937 DN’s.

The boats were ready to sail by the time the winter ice had formed, and we all took off for Lake St. Clair by tying the boats to the top of the cars. (Oodles of Fun!) Races were held each weekend at the foot of Crocker Boulevard. But, our first winter found most every boat incapacitated -- hull sideboards cracked, guy wires snapped, masts broken, runners split, runner planks split, etc. Basically, there was a mess of broken lumber. Arroll, Jarrett and Lodge went back to the drawing boards to re-design and strengthen each part in order to start another class the following year. Needless to say, we all went back for more!! 

The new boats were much sturdier and survived the punishment we gave them. In fact, my boat which is 58 years old still sails on an inland lake every winter. Some features have been adjusted due to age, turn overs, spills, falling masts, etc. But it sails! And gives rides to kids! Since my boat is stored under a porch and exposed to weather damage, it is not in excellent shape. A large crack developed in the runner plank, but Tom Hamill of White Lake, Michigan, skillfully repaired it.

Archie Arroll assigned numbers to each of the first 50 boats and I got #46. I guess I didn’t have much money that week to buy numbers and DN letters, and pay a sailmaker to sew them on my sail. So I cut out the numbers in plywood, painted them black and tacked them onto the hull sides, where they are now. Now I see that the IDNIYRA, which did not know I had #46, has given my number to Ken Devisser of Matawa, Michigan. I can truly say that Mike Griffith, DN US 859, would have a fit if he saw another boat fly by with his boat number, as he states in his article about Viewpoints on page 12 of the March 1996 Runner Tracks regarding retiring boat numbers.

Thrills of iceboating days: first ride...first ride on your own boat....first rides of your three sons....first ride for your wife alone....seeing some iceboat videos on TV unexpectedly. I have cut out pictures from newspapers and magazines for 59 years and have ten albums of pictures and articles which give me more thrills every time I read them. At 85, my feet and hands get too cold to be out long. Guess my circulation is slowing down.

Hope this is interesting to you if you have gotten this far. See you on the ice someday.

The DN Iceboat

by Don Daller - DN 46

Iceboating is without question the fastest way to sail and iceboat racing is a very exciting way to race. If you live where the lakes or ocean near you freezes, you can sail all year round. For many of us winter becomes the season we look forward to most.

There are a few common misconceptions about the sport. Many people think sailable ice only occurs once in a while. When the lake you see every day still has ducks on it or is under a foot or snow, you can often find another pond, lake or bay in your area that has sailable ice. In many areas you can sail on half to three quarters of the winter weekends. Portability of the boat is important.

People often wonder if it is possible to be warm on a windy, 20 degree day. We sail in temperatures down to about zero degrees Fahrenheit. Being warm at these temperatures in apparent winds as high as 60 mph is just a matter of dressing for it.

The sport is safe if you know what you are doing and are careful. There are lots of ways to get hurt in any craft that is capable of 60+ mph. When people get in trouble, it is usually because they don't follow the safety rules.

Ice comes in many forms, some if which are very safe and some very dangerous. Iceboating safely requires understanding of ice conditions, sailing skill and good judgment. Sailing with experienced sailors is usually the best way to learn.

There are a few commercially produced boats and several types you can build yourself. For most people, the best answer is to build or buy a DN. It is by far the most popular and widely raced boat world wide.

Some people think they need a two man boat. If you are primarily interested in taking friends for rides, a two man boat may be a good choice. If you are more interested in sailing, build a side car for your DN for those times you want to give someone a ride.

If you are thinking of sharing a two man boat, consider building two DNs instead. It will cost about the same. In anything other than heavy wind, a two man boat is faster with only one person in it and will tend to get sailed solo.

The DN was designed in 1936 to be easy to build, light enough to be easily transported, iceworthy and inexpensive. The modern DN still meets these tenants although it has evolved considerably over the last 50 years. The cost to build one has evolved to, from about $25 in 1937 to about $1800 now. It takes most home builders a month of part time work to build a DN. (See supplier list)

The DN gets its name from the Detroit News newspaper. In 1937 the newspaper donated their wood shop to build the first fleet of 15 DNs. Some of them are still sailing today.

The DN is light (portable) and quick to set up. It is a high performance boat but isn't so fast that it needs a huge piece of ice. You do not need to be a 20 year old Olympic athlete to be competitive. Many of the fastest sailors are in their 50's and 60's. The DN is a reasonably strict one design boat so this years winner will not be next years barge.

Most sailors find racing offers the most challenging and exciting aspect of the sport. The International DN Ice Yacht Racing Association (IDNIYRA) was formed in 1953 to promote DN racing. The IDNIYRA sponsors the DN North American and World Championship regattas. The class has approximately 1000 members in North American and another 1000 members in Europe. Annual dues are US$25.00.

The Association publishes several newsletters and a yearbook each year. The IDNIYRA Yearbook contains the Official Specifications, membership lists and a local club listing among other things. The current newsletter and yearbook will be sent with membership.

If there is a club in your area, contact them. They can offer ice condition information, racing programs and building advice. If you do not have a club near by, call iceboaters that are in your area. You can find their phone numbers in the yearbook.

IDNIYRA offers a great iceboating publication. "Think Ice Millenium Edition" is a 100 page book on all aspects of DN sailing and iceboating in general.

Sail numbers are issued through IDNIYRA for US$10.00. Sail numbers are not required unless you plan to race. Many people get their own sail number when they buy their first new sail.

DN building plans are available through the IDNIYRA treasurer's office in either metric or US measurements. The cost is US$15.00.

Editor: updated August 1, 2002 to reflect current prices for IDNIYRA services


The State of DN Racing

by Jane Pegel - US805 - April 1986

I'm pleased to make public the fact that I'm completing my 31st season of DN racing. My first DN was #305. This number still remains in the family and is registered to my husband Bob. I race under DN 805 and my daughter, Susie, races under DN 905. I have a record of all official class publications dating back to 1956, and I'm the only person whose name appears in the race results of that vintage who is still racing DNs. With any luck I'll be racing hard for a good many more years, in fact Bob is going to build me a new hull.

The point is I've seen a lot of sailors and boats come and go. The Class has weathered good seasons and bad and experienced some growing pains. The 1986 North Americans was not the largest ever held, but I think the level of racing was perhaps the best we've had. Seldom have we seen the Champion come away without winning a race. What does this mean? I think it indicates that a lot of sailors have learned how to set up their rigs, align and sharpen their runners, and sharpen their sailing skills to a level required by the world's most competitive iceboat racing class.

Through the ingenuity of its sailors, most of whom build their own boats, the DN has evolved into a boat that is faster, lighter, stronger, easier to sail, and more fun to sail than it was when I started in the Class. Original DNs hiked a lot, were heavy to carry, and broke down. These factors made them hard to sail. In fact, I bet that I'd be hard pressed to physically handle one of those boats and race it hard all day. I'm thankful the rules for the Class have enabled it to become such a fine boat to sail and that these rules have encouraged innovative sailors to join the class, for they're fun to race against.

Ultimately, I guess it's the people in the DN Class that have made it so much fun. Sure, we sometimes have disagreements concerning the proper approach to governing the Class, but we are unanimous that DN racing is a "high".


As with sailboat racing, one of the things that makes iceboat racing so satisfying is the "honor Code" that is required on the race course in order to make the game a fair one. The officials do not blow a whistle, stop the action, deal out a penalty, and award a bonus tack to the fouled boat. The sailors police themselves, give way to the right-of-way boat, and when an honest error in Judgement is made, Justice is served through the protest procedure.

To the credit of the racers at the North Americans, there were no serious collisions. But there were a number of fouls. A few of these were carefully resolved by the protest committee, and one sailor voluntarily acknowledged his error and withdrew from a race. In these few instances the game was fairly played. Unfortunately, these instances were outnumbered by foul situations that were not fairly resolved. In conversations following the racing, many of the sailors expressed the opinion that not everyone is fully aware of his responsibility in various close quarter racing situations. I have been asked to explain the proper application of the rules and the appropriate boat handling for a couple of the most common situations:


"When two yachts are sailing on-the-wind, the yacht on the port tack shall keep clear" of the yacht on the STARBOARD TACK. "When two yachts are sailing OFF-THE-WIND, the yacht on the PORT TACK shall keep clear of the yacht on the STARBOARD TACK." When boats to which the above rule applies are converging, it is the responsibility of the boat on the port tack to give way to the boat on the starboard tack. However, BOTH BOATS are obligated to prevent a collision, so if the starboard tack boat believes that the port tack boat is not going to give way, then the starboard tack boat is entitled, indeed is obligated, to take evasive action.

In a port-starboard situation, the proper steps to comply with the rules are as follows.

  1. The port tack boat should let the starboard tack boat know she sees her. The helmsman of the port tack boat should markedly turn his head toward the starboard tack boat, signal with his hand or perhaps by nodding his head, so the starboard tack boat is assured the port tacker sees her.
  2. The port tack boat should alter her course (tack, jibe, bear away, or freshen, as is appropriate) A COMFORTABLE DISTANCE FROM THE STARBOARD TACK BOAT.
  3. If the port tack boat does not take evasive action, then the starboard tack boat should tack, jibe, bear away, or freshen, as is appropriate. Because evasive action taken by the starboard tack boat is usually at the last possible moment, she should maneuver in a direction that will reduce the closing speeds of the two boats so if a collision does occur at least damage will be minimal. For example: Port and starboard boats sailing on-the-wind are converging. Only these two boats are in the area. The port tack boat takes no evasive action. The starboard tack skipper estimates he'll hit the port tack boat at the mast. The starboard tack boat should head up, ease sail, and even may tack. This action will slow the starboard boat and put her motion more parallel with the port tacker. If the starboard boat bears away to go behind the port tacker, the chances of a harder, and perhaps head-on collision are more likely.

NOTE, this evasive action of the starboard tack boat is not a Violation of the rule: "a right-of-way yacht shall not alter her course so as to mislead or prevent a non-right-of-way yacht from keeping clear." In the above example, the non-right-of-way yacht had not taken any "evasive action" and Fair Sailing requiring common sense, safety and good sportsmanship required the starboard tack boat to alter course. If the port tack boat had begun to lay off to go behind the starboard tack boat, and then the starboard tack boat had altered course so the port tack boat could not avoid her, the burden would be on the starboard tack boat. THIS SELDOM OCCURS.


The primary difference between sailboat rules and iceboat rules is in those that apply when sailing off-the-wind and when rounding the leeward mark. The iceboat rules are designed to make it as safe as possible to get around the leeward mark without running into another boat.

The highest speeds are attained when sailing off-the-wind. The most difficult maneuver in racing is making a good turn at the leeward mark. The convergence of multiple boats complicates the maneuver. The rules are designed so the same boat has right-of-way while rounding the mark that had the right-of-way all the way down the leg. Think about it this way:

  1. Marks are rounded to port.
  2. Boats are on the port tack as they round the mark.
  3. As the boats make their approach to the mark and are close enough to each other so that there might be a collision, the rules provide the boat that is inside of the other has right-of-way, even 100 yards from the mark. For example:

    a)  If two boats are side-by-side and on port tack sailing off-the-wind, the windward boat has right-of-way. Because the windward boat already has right-of-way, there is no transfer of responsibilities as the two boats get closer to the mark, the windward boat is inside, and must be given room to round the mark.

    b)  If two boats are approaching the leeward mark on opposite tacks, the starboard tack boat has right-of-way. The port tack boat must bear off to leeward to honor the starboard boat. In bearing off, the port tacker automatically gives the starboard boat room to jibe inside and to windward of the port tacker, which then puts them in the same relative position as the two boats in example 3a. Of course, the starboard tacker has the option of actually forcing the port tacker to jibe onto starboard tack too.

The danger of a collision, and a foul, exists when boats are side-by-side (as in 3-A) or aiming at each other (as in 3-B). A collision may also exist when a faster moving boat approaches from the rear. Whether approaching a mark, or out in the middle of the course, a boat coming up from behind cannot run into the boat ahead. If the boat ahead is moving at the same speed, the chasing boat can't catch her to hit her, so there isn't a problem. In the final approach to the mark, the faster moving boat approaching from the rear must not pull alongside on the inside if the boat that was ahead has started her rounding maneuver.

EVERYONE MUST CONSIDER THE POINT WHERE THE ROUNDING MANEUVER BEGINS IS INFLUENCED BY THE WIND AND ICE AND ALL OTHER BOATS IN THE AREA. Because the speeds of the boater involved may be very much different (one guy might be pushing, another guy in a screaming hike), common sense and safety ARE SUPREME. There is not a specified number of boat lengths, as in sailboat racing, to tell us where the rounding maneuver begins.

Quick and Dirty Ice Claws

ice_claws.gif16.58 KB
by Bob Dill
September 1989 (Revised January 1991)

Most people who iceboat for a number of years find themselves in the water sooner or later. If you ever find yourself in the drink one thing you will really WANT to have is a pair of Ice Claws. They are also called Bear claws, ice awe, ice picks and other things. Being able to get out quickly is key to surviving immersion in 32 degree water.

Ice Claws make getting out a very easy. Many of the people who die on ice do so because they don't have ice claws and can't figure out how to get out without them. Getting out without ice claws is possible if you know how, but it is much less reliable (see Self Rescue Technique). Anyone who is on the ice should ALWAYS have a pair of ice claws with them.

In Vermont we have had two problems with them. First, they tend to reside in tool boxes rather than with sailors. We have had more than one solo sailor go for a swim with their ice claws launch site. So far they have been able to extricate themselves.

The other problem we used to have is that many sailors didn't take the little time it takes to make themselves a pair. To address that we mass produced about 50 pair of crude ones. These have been given to everybody and anybody. No one seems to object to their rough finish when they are given a pair.

The basic materials are 3/4" by 1 " hardwood strips, 20 penny common nails, Velcro and 3/16"" nylon rope. The drawing shows one of many designs and a minimum investment construction method. Make a lot of them. A batch of 50 won't last very long if you are reasonably diligent about giving them away. One person can make about 10 in an hour of working time.

Once you have made plenty of them, give a pair to everyone you know who spends time on the ice. A brief account of the difficulty of getting out without them will help assure that they don't get left at home. Put a couple in your pockets and a few more in your tool box to give to people on the ice. Sooner or later you will save somebody's life.

There are several styles and ways of making them. The method shown and described here is for making a bunch with a minimum investment of time and money.

  • Prepare the nails by cutting them off with a bolt cutter (or hack saw). The length from the pointed end should be 7/16" shorter than the amount your 13/64 drill sticks out from your" drill chuck. Make a nail nipper gauge by drilling a hole(s) in a board the right depth to bolt cut the nails to the correct length. 20 penny common nails were chosen because they are plenty strong enough but they are much easier to cut than cement nails.
  • Velcro: Velcro Hook is glued to the bodies. Use 2" wide hook. if you can get it, use #800 (or" equivalent). It has 0.008" monofilament in the hook and is stronger than #650. your sail" maker may be a good source. Store the hook tape flat and unwrinkled. It will be much easier to glue on that way. Cut it into 1 1/2" lengths to be glued across the bodies before they are cut" apart.
  • Use 1" wide pile (loop) tape to hold the halves together. cut it into about 5" lengths.
  • Note for step 6: The 13/64" hole for the nail should be about 7/16" longer than the nail. Assemble one pair far enough to check that the hole depth and nail length are proper.
  • Note for step 7: Putting a flat weight on the VELCRO hook will hold it down while the epoxy cures. This may not be necessary if you have kept it flat and wrinkle free.
  • Note For Step 11: Wet the hole and nail with epoxy before pushing the nail in. You often have to push the nail fairly hard to get it all they way in because of excess epoxy in the hole.
  • Note for step 13: Prepare lanyards by cutting the nylon rope into 48" lengths and fusing the" ends. Both ends of the lanyard are pushed in from the side opposite from the VELCRO. An overhand stop knot keeps them in.

The safest way to wear them is to put the lanyard over your head and under one arm. The lanyard is designed to be short enough so they won't flop around. It's length can be adjusted with a slip knot stopper knot.

If you have questions or suggestions give me a call.

Quick Ice Claws drawing

Self Rescue Technique

by Bob Dill

Occasionally people find themselves in the water with wet, slippery black ice all around them. We had a near fatality in Vermont a few years ago when a skater tried to cross a pressure ridge. He stepped on a small loose plate and fell in. He had no ice picks and was unable to get out. His cries for help were heard by nearby iceboaters after he had been in the water for about 10 minutes. He was fairly hypothermic by the time we got him to shore.

To assess what is required to get out in this situation, we cut a hole in the ice and jumped in with rope and a dry suit on. By far the easiest way to get out is with ice picks, ice awls, bear claws or whatever you call them. If you don't have them, don't panic and act fast. Swim to the edge of the good ice, put your forearms on the ice, get your body near horizontal and with powerful frog kicks you can push yourself out. You should lift with your arms, but only straight up. This will help you get over the ice edge as you kick. Don't try to pull yourself out with your arms, they will only slip off. The idea is to keep yourself low and use the frog kick to push yourself onto the ice. Once out, get to shore or help quickly and out of your wet clothing as soon as possible.

A warm shower is almost always in order after a 32 degree swim. If a victim is having difficulty walking, talking or has a noticeable pallor or weak pulse in his extremities, call a rescue squad. Try to rewarm the victim in a shower or bath or at least with other people and warm drinks until the rescue squad arrives. Concentrate on warming the torso, not the extremities. The rescue squad should be called as soon as things even begin to look like significant hypothermia might be involved so they can be ready and waiting when the victim gets to shore.

I often wear a thin farmer John wet suit when sailing on questionable or unknown ice. They are comfortable, give good back padding for bumpy ice sailing and make being in the water much less dangerous and uncomfortable. The wet suit will also make getting to shore much less urgent. If you get wet a long distance off shore, this could be a crucial consideration.

Ice Grain Structure

by Bob Dill - March 1990 - Revised January 1991

How ice forms in the Fall has a lot to do with how it behaves in an advanced thaw condition in the Spring. The following article reviews how water ice forms into one of two types of ice that are very different from each other.

There are two basic types of ice: water ice and snow ice. Water ice is ice that forms under the surface of the ice sheet by water solidifying into the crystal structure of the bottom of the ice sheet. It has a grain structure that is uniform through the ice thickness. It contains relatively little dissolved air.

Snow ice is any ice that forms from snow or slush freezing on the top surface. It has a grain structure comprised of the ice granules from the original slush. It contains a lot of air trapped between the ice gains.

This article primarily concerns water ice. In most cases the snow ice will melt off the underlying water ice after an extended thaw because it strongly absorbs sunlight.

Melting Factors

Ice melts in two ways, on the surface and internally. Surface melting is caused by warm air, especially with wind and to a lesser extent, rain. In December 1990 we had 4" plate of ice on a" pond near Burlington. 24 hours of 47-50 degree temperatures, 15-30 mph wind and less than an inch of rain melted 2 inches of the 4" plate and completely melted 2 + inches of ice on several" warm water holes. In Syracuse, Indiana at about the same time, they had similar ice exposed to the same temperatures with 4 inches of rain. They had very little ice loss.

Puddles of water on the ice, whether from warm wind or rain. They drain through any crack or hole in the ice. The water erodes little holes into a runner sized one. There are some excellent pictures of this in Think Ice. The size of the holes is dependent on how much water drains through them and how warm the water is. They can form to runner size in less than 24 hours in 12 inch thick ice. This often happens in mid-season thaws.

Internal melting of thick ice is usually a more gradual process, requiring several days of sunny, above freezing days and warm nights. Of course, if the ice is only a few inches thick and it is 50+ degrees and sunny, things can happen fast!

Ice Grain Types

Water ice freezes into crystal families called grains. The melting takes place between the grain boundaries of the ice. The melting point of water is slightly lower at the grain boundary because the crystal structure is less perfect there.

This first shows up in black ice as sheets and strings of bubbles in the ice along the grain boundaries. The ice becomes gray from the bubbles after a while. After an extended period of heating by the sun the grain boundaries will melt all the way to the bottom of the ice, forming many tiny drain holes. This is evident when all the puddles disappear from the ice surface of thawing ice.

When water ice is exposed to prolonged sun at above freezing temperatures it thaws into either honeycombed ice or, if the ice grains are larger, into interlocked grains. In the latter stages of the thawing process there is a big difference in the weight bearing ability of these two grain structures.

Well over a foot of honeycombed ice may not support a man or a DN. A piece of large grain ice only three inches thick with the same thaw history will support a man. It can sag as much as 6 inches before breaking.

The grain structure of the ice is determined by the conditions of the ice when it freezes. When ice freezes an ice crystal starts growing at a nucleation site on the surface.

Large Grain Ice

A nucleation site is something the cold water molecules will accept as a seed crystal. It can be a small ice crystal, a snow flake, or a piece of dirt the water accepts for an ice crystal. If the surface freezes in still conditions with no snow falling. relatively few nucleation sites are available. The ice crystals will form long, flat spears (they are dendrites, look like Christmas trees and can be seen in any still water in the process of freezing). The spears grow until they run into one another. They then fill in the intervening surface with dentritic branches.

If it is not disturbed, the first thin skin of ice determines the grain structure for the ice that forms as the sheet thickens. Some of the spears grow rotated in the water surface. The ice grains that develop from the rotated spears will grow at an angle the surface. The grains mechanically lock together because the grain boundaries are relatively large planes which have a lot of interlocking between the grains.

Small Grain Ice

Small Grain ice (Honeycomb ice) starts with a lot more nucleation sites. They can be snow or frazzle. Even a very light snow provides plenty of nucleation sites to form a small grain structure. If you look closely at ice forming in still conditions with a little snow falling on its surface, you can see the small grain structure developing. Frazzle is broken ice spear slush that forms in water disturbed by waves. In cold, wavy conditions frazzle can form a thick slush on the surface.

The ice that forms with a lot of nucleation sites has grain boundaries typically less than an inch apart. In this case the grains constrain each other so much they grow almost Straight down. This results in the long narrow grain structure typical of honeycombed ice. The relative weakness of small grain ice is a result of the grain boundaries being interlocked on a much smaller scale. This small scale interlocking melts out quickly when the ice melts.

Ice forming on still water with no snow falling will have the largest grain size. As the water is more disturbed the grain size will become smaller. If even a very light snow is falling, small grain ice is almost certain.

Safety on Thawed Ice

If you find yourself walking across well thawed spring ice, looking at the surface of the ice may tell you which ice is strongest. Using a probe (ice chisel or the like) to test the ice before you walk on it is always a good idea on weak or unknown ice.

Small Grain ice is typically dark with a small grain structure made up mostly of 3 to 6 sided polygons. The average dimension of these polygons is generally less than 1 1/4 inches. It chips out into small columnar pieces then hit with the probe. It may be possible to drive the probe through a foot or more if this ice. If the ice feels like it is settling a little when you walk on it, it is!. If you stomp on it you can sometime punch a hole through it. A good time for a dry suit and a belay rope.

A Large Grain Ice surface distinctly shows a much larger and more irregular grain structure. The typical grain dimensions range from 3 inches to as much as 2 feet. This ice tends to have a grayer color in advanced thaw condition. It chips into chunks when poked hard. In an advanced thaw condition, it is much stronger than small grain ice.

It is common to have areas of different grain types mixed together. The size of the sheets of one ice type vary from entire lakes or bays to a patchwork of mixed pieces a few feet in size. Broken up plates of one type often fill in with the other type.

Cobblestone Ice

When a thick ice is thawed enough to melt the grain boundaries all the way through the sheet, an unusual and very rough ice surface can result. The ice melts more at the grain boundaries than on the grains between the boundaries, After refreezing, this can result in a regular but very rough, polished surface. The dimension of the roughness is proportional to the grain size. In large grain ice the result is much like a cobble stone surface. This probably accounted for the extremely rough conditions at World Championship in Arsunda Sweden last year.


The Basics = Sailing Smart

by Jane Pegel - US 805

The experienced sailor has developed skills that enable him to have a great day of sailing and racing in a variety of conditions. This sailor (I am avoiding using "he") has the ability to select an appropriate ice site, appropriate ice site, properly rig the boat for the conditions of the day, and then properly handle the boat under sail. Past newsletter articles have addressed ice conditions, others have addressed tuning, but few have addressed the basic principles involved in becoming a good iceboater. Good iceboaters sail smart. My goal here is to discuss some of the factors to be considered if you want to sail smart.

One would think that just plain common sense would cause a sailor to sail his boat in a manner appropriate for the conditions. But my mother was correct when she used to say, "People can find more ways to try to kill themselves."

In Parking Areas

Hardly a day on the ice goes by that I do not see someone looking for trouble. First of all, don't bring your pre-school age child down to the ice without a crash helmet on his head. A toddler has difficulty walking on bare ground, don't put him on slippery ice. Likewise with your family dog. A child old enough to use ice skates should be brain washed about being around iceboats. He should understand that the iceboat cannot stop quickly. Designate a safe area for skating and stress the importance of his staying in that area. And I'm not pleased when an ice-skate creases the side of my boat when its wearer crashes and bums.

Whenever your boat is left unattended, be sure she is parked into the wind and the parking brake is on. It is also a good idea to pull the mainsheet line out of the aft blocks in case the wind shifts. DN rules require use of the parking brake.

Care must be taken when maneuvering in a crowded parking area. Whatever you do, DO IT SLOWLY. Pushing or pulling the boat should only be done in a direction straight into the wind. If you must head across or down wind, GET INTO THE BOAT so you have maximum control and visibility. Don't ride on the runner plank, sitting or standing. If a pedestrian, skater, or boat unexpectedly crosses your path, your maneuverability is limited when you're tiding on the runner plank. Don't park your boat in a high traffic area. As provided in the racing rules, a good race committee will establish a safety zone down wind of the finish line. This provides for a clear "sail out" zone after boats cross the finish line. Boats and gear parked in the safety zone may be disqualified.

Finally, when there is a good breeze blowing, hoist your sail after you have pushed the boat clear of a crowded parking area, and lower it prior to returning.

Turning and Stopping

Rocketing down the ice is the ultimate iceboating thrill. But how do you stop the darn thing? Or how do you turn the race mark when you're approaching it at warp speed? Let's take a look at the boat handling skills involved:

Stopping: Almost everyone knows you have to arm into the wind to stop. But not everyone knows the steps in the transition from rocketing to stop. The ultimate stopping challenge is on hard ice with a strong wind. If you're sailing on-the-wind, merely head into the wind and allow enough space for your speed to, "bleed out". If you're sailing off-the-wind at top speed, head straight down wind with your sail trimmed hard, this will allow you to slow down as the wind passes by your sail. The next step will be to turn across the wind (onto a reach) and then into the wind. As you start to turn onto the reach, ease the sail well out so you won't be thrown into a hike. Keep your weight forward in the boat so there is adequate pressure on the steering runner. Quickly turn toward the wind. If you're having trouble getting the boat to turn toward the wind, trimming the main slightly will help pivot the boat into the wind. Then as you get into the wind, trim the sail to reduce the flogging of the sail, battens and boom. As you coast to a stop, resist the temptation to drag your feet on the ice. In a DN it's easy to swing your feet out of the boat, but if your spikes catch a flaw on the ice, you may break your leg.

Turning the Leeward Mark: You can apply some of the techniques described for stopping, but as you get headed on-the-wind after rounding the mark, just trim in and keep going. Because you're likely to be rounding with other boats, it is very important to remember the two key things of trimming the sail is to pivot the boat in the turn and keeping your weight forward to hold the front runner on the ice. The Gold Fleet sailor approaches the leeward mark at high speed, heads for a pivot point about 50 feet from the mark toward the side where the race committee stands. He (this is a generic term) momentarily heads down wind to bleed off some speed, then turns for the mark into a, "transition zone", with the sail eased enough so that the boat does not hike. In this final approach he is headed toward a point about 15 feet down wind of the mark. When he gets about 20 feet from this point, he starts the turn, and as he comes close to the mark he is already headed on-the-wind with the sail trimmed hard. This is the perfect turn. The exact ice and wind conditions and the presence of other boats always require instantaneous adjustments. As the Bronze Fleet sailor comes down to the leeward mark, his initial heading is usually too close to the mark, he has not provided for a "transition zone" and instead of being headed on-the-wind as he passes close to the mark, his boat may be in an uncontrolled hike, careening off to starboard, a hazard to himseft and to others.

sail_smart_1.jpg (26381 bytes)

Port tack layline?  Not likely!  Sail smart - think ahead!!

Photo by Lou Loenneke

Rounding the Windward Mark: This can be hazardous when it's windy and a number of boats are approaching the mark together. The goal is to round the mark and head off-the-wind at top speed without colliding with other boats. As you make the approach to the mark lean way back with the mainsheet in your right hand and your hand close to your chest. If the boat starts to hike, you can extend your arm and this will case the sail some. Try to keep your body aft to hold the boat down. Peel off around the mark, heading off-the-wind until the boat comes out of the hike. If you're strong enough, you can trim the mainsheet as the boat comes out of the hike. Keep a firm grip on the tiller. Stay in sync with other boats making the turn. When all runners are on the ice and the boat is tracking a straight line, then you might be able to put the tiller between your knees and trim with both hands, but please don't try this when you're sailing close to me.

The Right of Way Rules

We race under the rules of the National Iceboat Authority. These rules were developed in 1963 by representatives of each of the iceboat class associations. Prior to that time we encountered different rules in different regattas. You can imagine the confusion. The basic philosophy of the rules:

  1. gives the boat sailing on-the-wind right of way over a boat sailing off-the-wind;
  2. gives starboard tack right of way over the port tack when boats are sailing on-the-wind or both are sailing off-the-wind;
  3. gives each boat the right to slow down or maneuver out of a hike (leeward boat when sailing on-the-wind, windward boat when sailing off-the-wind);
  4. gives the inside boat the right of way when approaching and turning a mark (leeward boat when approaching the windward mark on starboard tack, windward boat when sailing off-the-wind, inside boat at the marks, the starboard tack boats at the leeward mark);
  5. requires a boat altering course to stay clear (tacking, jibing).

The "inside" exception is the port tack boat approaching the windward mark, who must give way to the starboard tack boat. A sailor who keeps in mind the basic premises will find it easy to make safe and smart moves on the race course.

The 1992-1993 season will be Jane's 46th season of iceboating and her 37th season in DN's. A quick scan through results of past years show Jane winning the North Americans twice has been runner up seven times. She has also won the Northwest Annual Regatta 10 times. As you might have guessed, Jane is just as fast on soft water. In fact, she has been awarded the Yachts Woman of the Year Award three times & Jane has served the DN Class as Commodore sail_smart_2.jpg (15050 bytes)

This article was originally printed in the December 1992 newsletter

The Racing Tack

by Ron Sherry - US 44
December 1998

Over the last few years, advancements in ice boat technology have radically changed the face of DN racing. For instance, the new bendy rigs have ushered in a new era of speed. However, they have also presented us with a new challenge in tacking…mast rotation problems. The following article details several techniques that have been developed by the masters of the sport in answer to this challenge, as well as some strategies for completing a smooth racing tack while maintaining speed.

The ultimate goal of a racing tack is to complete the maneuver as smoothly and safely as possible without losing speed. Before you tack, make sure there are no other boats in the area and that you have a smooth and snow free area in which to tack. To begin the tack, start turning the boat up toward the wind. Start the turn slowly with the main sheet all the way in. Keep the sail in tight and start to slide your body forward in the cockpit. When the sail tacks, lower your helmet to the cockpit floor in front of the seat back. To accomplish this, anchor your heels in the hiking rack and bend your knees to pull yourself forward. Having your helmet on the cockpit floor means you do not have to ease the sail as much to get your head under the boom and you can maintain greater speed through the turn. This trick also equalizes your weight over all three runners and gives you better steering, making for a smoother tack.

When the sail tacks, ease the sheet just enough to get your head under the boom. Continue to lay the boat off and push the boom forward and to leeward with your leeward hand. As you do this, ease the sheet and use your knees and your weather hand to steer. Usually the mast will rotate at just about the same time the boat goes up on a hike. Let the boat hike, slide your body back into position and ease the sheet slightly. The boat will then begin to come down from the hike. As it does, sheet the sail in hard. This will cause the boat to hike once more. Ease the sheet slightly and before the boat comes all the way down from the second hike, sheet it in hard again. This second hike will help you to accelerate back to top speed. Smoothly completing a tack using this technique will send you off toward the next mark with very little loss of speed.

If the mast does not rotate using these techniques, do not lay off and pump the sheet. Laying off assures you to lose distance to weather, as well as putting more pressure on the leech of the sail and less pressure on the front of the sail. This allows the front of the sail to luff and the luff curve ill keep the mast from rotating. If you try tacking the boat and the mast does not rotate, Jan Gougeon recommends that you head the boat up toward the wind and allow it to slow down a little. This Reduces the apparent wind pressure on the leach of the sail and will maximize distance to weather and minimize your losses. No matter which technique you use to rotate the mast, this first step is the most important.

After the boat slows down a little, lay the boat off slowly and push the boom forward and to leeward, while adjusting the sheet. There are many techniques for this maneuver, no one better than another; simply try each one and decide which works best for you. Chip Cartwright slides forward and uses his toes to rotate the mast. Mike O’Brien uses his shoulder. Some people kick the boom. I have had the most success by sliding my leeward foot back so I can press my knee against the weather side of the boom. I then use my leeward elbow against my leeward knee to leverage the boom over. The boom is connected to the sail, which is connected to the mast by the luff rope that is in the back of the mast. A mast that has not rotated has the luff grove to windward. By pushing the boom to leeward, it pulls the luff groove to leeward where it belongs.

The Europeans have developed a solid hound that is about four inches wide. The side stays are connected at the outside of this four-inch bar. When tension is placed on the weather shroud, the solid hound rotates the mast. Perhaps a Sarns’ triangle and U-strap put on backward with the bent wings toward the front would have the same effect.

Once you understand the dynamics of this issue, it is easy to come up with a solution that works for you. If you have any questions or comments, feel free to contact me at Composite Concepts. The phone number is 586-790-5557, the fax number is 586-792-3374, and the email address is

Boat Speeds

by Bob Dill - US 3904 - February 1993

All sail boats have performance characteristics associated with their design, sailing conditions and the amount of wind. Like most of us I have been curious about how fast we are truly going on the ice. Last fall I bought a radar gun. It can accurately measure the speed of a DN about 500 feet away. Wind speed was measured with a Davis Turbometer. The following are some measurements we have made so far this year, mostly from the Gold Cup.

Making measurements of wind speed or boat speed is easy. What is more difficult is measuring the wind the boat experienced to attain a given boat speed and sailing angle. For the purposes of this discussion I estimated the wind speed the boat saw based on the range of winds I measured on my anemometer over an extended period of time.

At the low end of the wind range the boats will sail in winds as light as about 2-1/2 MPH. The down wind boat speed is about 10 MPH and the up wind boat speed is about 12 MPH. Peak running speed is about 14 MPH so when boat speeds get slower than 10 MPH the races degenerate into running races. Races sailed in the North Americans on Wednesday in 2.5 to 3.6 MPH wind had peak boat speeds of 15 MPH and relatively little running. Races sailed on Monday in slightly less wind had too much running.

By 5 MPH wind the peak down wind boat speeds are in the low 20's. By 15 MPH wind the down wind boat speeds are in the mid to high 40's. The peak speed we saw at the Worlds was 56 MPH in wind that was 15 to 18 with gusts into the low '20s. Peak up wind boat speeds in this wind were in the low 30's Even in 25 to 30+ winds a few weeks ago Peter Hill and Bob Schumacher were sailing in the high '50s on a deep down wind angle.

On a broad reach with the sail sheeted as much as the boat would handle Bob got up to 68 MPH. A limiting factor is that the balance of the helm is very dependent on how much of the sail is luffing. This resulted in the need for rapid and radical corrections with the tiller. When Bob let out the sheet at the end of his run the runner lifted completely and he dragged the stern of boat for 150 feet or so. The drag of the sail exceeded the weight on the front runner.

We measured a couple of high wind indicators that will be handy when you do not have an anemometer in your hand. At about 22 MPH the sails on a parked boat will start to flog (modern racing sails). At about 32 MPH the boat will start to hop backwards on a rear mounted break.

Suggestions for racing winds on good ice: Wind that dips below 2.5 will result in excessive running. 3 MPH should eliminate running by skilled sailors. Of course, on sticky/snowy ice higher minimum wind speeds are appropriate. On the high wind end, 25 MPH in regular gusts seems like a reasonable top speed for racing. The Europeans set 12 meters per second (26.8 MPH) as their upper limit.

In terms of performance on a race course, it looks like the best boat speed to wind speed performance is at low wind speeds. A 4 or 5 to l ratio is possible at 3 to 5 MPH wind. At 15 MPH wind the ratio is probably closer to 3 or 3.5 to 1. By 30 MPH wind the ratio is only about 2:1.

I am also trying to get some data on other types of iceboats. If you would like to help with this project please get in touch with me.

Putting Numbers on Iceboat Sailing Performance

by: Bob Dill
February 2004

While there has been no shortage of speculation on top speeds, ice boating has been a hard sport to put valid performance numbers on. My effort to get a proper perspective started in earnest with the purchase of a good quality radar gun in the early 1990s. That did a pretty good job at sorting out the velocity picture but did not say much about angles (see 1993 article: "Boat Speeds" on the DN website).

In our speed project with the Wood and Iron Ducks on dirt we have evolved from using timing traps to radar and are now using a sophisticated GPS.  The GPS method has the significant advantages of allowing the freedom to sail wherever the wind takes us the fastest and avoiding the risk of having to sail fast at a measurement station.  There is more information on speed measurement on (particularly the Speed Record pages and the 11/99 newsletter).

The GPS we are using is a Trimble AG 132 with a Trimble data logger borrowed from a friend who works for the company.  This system is by far the most accurate and comprehensive system for velocity we have found.  The fixed position measurement uncertainty of the AG 132 (with the filtering turned off) is only 0.03 mph!  I also have done careful time over distance tests and found the GPS accuracy is at least as good as my test methods.  It's main liability is that it is expensive (it is a $4,000 GPS) and it is relatively bulky.

For projects other than setting speed records an inexpensive GPS with a data logging system is a good solution.  These units are surprisingly accurate.  The 0.1 mph accuracy claimed by most units seems to be valid most of the time based on comparisons of logs recorded simultaneously on the AG 132 and several Garmin hand-helds (see discussion of spurious data below).

Finding a good logging system was a problem until I found Kjeld Jensen's Cetus GPS logging software for Palm OS PDAs (  It is free, easy to use and very well thought out.  Cetus collects the following data every one or two seconds (depending on the GPS).

  • Position
  • Time
  • Velocity
  • Bearing
  • Satellites in view
  • HDOP (the quality of the view)

Using a conversion utility from the Cetus site you can convert the Palm database format to a text file that can be loaded into a spreadsheet.  The simplest and one of the most informative things to do is to graph the velocity.  With a little effort you can identify the various maneuvers associated with velocity changes.  It is an eye opener to see how much ground is lost in a tack.

You can also do the trigonometry of the positions and do an XY graph of position to show the track of the yacht.  This gives a nice perspective on the angles, speeds and distances.

You can go through the numbers in the spreadsheet and find the tacks, jibes and roundings by changes in bearing.  From this you can calculate the cost of the maneuver in time and distance.  You can also calculate the true wind angle by averaging the bearing on each leg.  With that and a reasonable estimate of the true wind velocity you can calculate the whole velocity triangle (I do it on a cadd program and avoid the trig).  Beta (β) is the angle between the apparent wind and the yacht vector.  It is a good estimate of the efficiency of the yacht.

You can compare the results from yourself and your tuning partner or the whole fleet... there is just no end to how much time you can spend winnowing out information from this data.  However, no GPS data is necessary to know if you are going slower or not pointing as well or, most of all, not getting to the finish line first.  What the data does do is put numbers on what is otherwise obvious.  I doubt this data analysis will offer any shortcuts to the NA championship.

From the DN data in medium winds strengths, the speed loss in the tacks is about 7 mph (out of 32). This results in distance losses averaging 130 feet involving about 30 seconds between when the boat starts to slow and when it is back up to the pre-tack speed.  For a jibe in these conditions the distance loss is about half as much.  On a big race course in a big fleet there are lots of other factors to consider as evidenced by the tactics of the best sailors who often demonstrate the benefits of a couple extra tacks.

The apparent wind/yacht angle (β) is where iceboats, and particularly Skeeters, are King. The apparent wind angle (β) is surprisingly low for very efficient boats like Skeeters (6 to 7 degrees).  This is equivalent to sailing at 8 to 10 times the wind speed and they are, in fact, capable of this feat in light winds on good ice.  In DN's and fast dirt boats β is more like 10 to 12 degrees.  

Data Quality and Accuracy

When everything is working right, GPS's are very accurate relative to most other measurement methods.  The larger issue is that they can give spurious data when things are not working properly.  Usually spurious readings are outside the believable range, but not always.  The two most common reasons I have encountered are weak batteries or a poor and/or rapidly shifting view of the sky.  Filtering can also be an issue. Particularly at lower speeds or when there are abrupt changes in direction or speed.

A fresh set of batteries is well worth the minor cost involved.  Lithium batteries have long life, do well in the cold and are a bit more expensive.  For a reliable sky view, I have had mixed success with carrying the GPS in a pocket on top of my chest.  Side pockets are often not good enough.  The best place is securely taped to the deck in front of the mast.

The "Max Speed" function is convenient and generally accurate but it is a single point with no supporting data.  If you log the data you have a better basis for confidence in the top speed values.  As a point of perspective for a DN: speeds a little over 70 mph are possible but not likely.

Filtering helps a GPS make the best guess in a tricky situation.  It is also used to keep the unit from being confusing  For example manufactures don't want you to think that your GPS is moving when it is standing still so they filter out low speed readings.  This is called 'Show Room Mode'.  'Tunnel Mode' tells the GPS to hold a reading for a few seconds when the signal goes away.  'As you were mode' tells the GPS to keep doing what you were doing.  This shows up sometimes when there is an abrupt change in velocity or direction.  While filtering causes some velocity errors these units do a remarkable job of telling you where you are and how you got there.  When these errors do occur they are generally obvious when you look at logged velocity data.  

Unlike inexpensive units the Ag 132 can be configured to turn the filtering off.  This allows measuring the fixed position 'speed' which is really the measurement error.  This is valid for both a static or moving GPS because the satellites are moving at several thousand mph relative to the GPS.  From their standpoint the GPS is moving very quickly at either 0 or 100 mph.  

Spotting Errors In Logged Data

Most of the times I have found bogus data it is related to a poor view of the sky.  The following are several things to look for:

  • If the number of satellites is below about 6 or the HDOP is over 3, the view of the sky may be a problem.
  • Calculate the accelerations and if they are more than -15% or +8% of gravity the data may be bogus (more simply if the speed decreases by more than 6 mph or increases by 4 mph in a two second interval you may have bogus data or the boat did something memorable like spun out).  The biggest speed changes occur during tacks or rounding the leeward mark.
  • Look for unchanging speed values.  More than two identical values is suspect.
  • Look for unrealistic speeds, time gaps, etc.  All of this can be done with simple spreadsheet functions.
  • The velocity = f(time) plot is a quick way to spot dubious data.


You need a GPS, a Palm Operating System PDA (you do not need much memory as the Cetus track.pdb files are very efficient), GPS data and PDA hotsynch cables, a null modem connector and a gender changer (Radio Shack).  Duck tape, packaging tape and/or a velcro covered cloth bag are helpful for mounting the GPS in a convenient place with a good view of the sky.

I have used several GPSs.  I like Garmins but they all have a 2 second time interval for NEMA sentences (data output).  I recently got a Magellan Meridian Gold mapping GPS at Costco that will output at one hertz.  Two seconds, however, is fast enough to get a good understanding of most of what is happens on an iceboat.  I keep hoping that the GPS makers will combine a Cetus like logging program into their vast computational capacity and memory.  Several requests for this have, so far, gone unheeded.  The track log on my Magellan will put in data points every second or so at speeds above 40 mph but the speed data is inaccurate.  There is a one second swing in the velocity averaging about 2 mph (ranging up to 7 mph) when the boat was going at nearly constant speed.


You need to know your way around your GPS setup, the PDA and the Cetus software.  Cetus has an excellent guidebook on their site.  It may take a little trial and error but it is pretty straightforward.

As you get data that you feel are representative of different circumstances I would love to see it.  In spite of logging data for three seasons I have yet to get good data for racing in winds over 20 mph or reasonably pure light wind sailing.  My email address is rdill at verizon (dot) net (spaces and spelling are an attempt to dodge email address crawlers should this newsletter find its way onto a website).

Happy Data Logging,


How To: Insert Runners

by: Paul Goodwin- DN 4061

This information is provided for the use of sailors who wish to build their own insert runners. Over the last few seasons a lot has been learned about what it takes to assemble an insert runner which can stand up to all ice and wind conditions. The construction described here is not the only acceptable design, but is easy to build and will give good results. The basic design is for a 36" long runner with a 1/4" thick blade. The changes required to accommodate thinner steel and/or shorter runners should be obvious.


Many materials are available to the builder for this type of runner. Recommendations for specific blade materials will not be made, since this information has been covered in other newsletters.

Blade shape

In order to determine what shape the blade should have, make a full-scale drawing of the complete runner (fig. l). A good starting point is to use the same nose and tail contour as used on the Sarns bull-nose runner. I prefer the appearance of a runner body which drops in height from the

inserts_1c.gif (16372 bytes) fig.1 COMPLETE RUNNER

chock to the nose (about 1"), and from the chock to the tail (about 2"). Don't forget about the 5/8" minimum radius on the front of the runner (see fig.2). Once the overall shape is drawn, add two lines to the drawing, one at 1-1/2" from the bottom and the other at the same height as the width of the blade material (2-1/2" to 3"). This drawing now shows the outline of the steel blade and the wood body. This is important since once the steel is hardened it will be difficult to change its shape.

Using this drawing as a guide, cut and shape the steel so it matches your desired outline. Drill six 1/4" holes through the steel 1/2" above the lower edge of the wood body for reinforcing screws (see fig. 1). Sharpen the bottom of the runner to a 90° edge. The blade is now ready to harden. 

inserts_2c.gif (8020 bytes) fig. 2 RUNNER NOSE


Spring steels are often purchased hot-rolled, which bas a rough surface. If the hot-rolled steel also has scale on it, sand blasting is required before it can be heat-treated. Most other types of steel are usually purchased either precision ground or cold-rolled, both of which have a smooth clean surface.

Steel that is already ground to the final thickness must be heat treated in a controlled environment so that no scale is formed on the surface. Steel that is thicker than desired should be ground to thickness after hardening. This final grind will help remove any warping.

Blades can be flame hardened which allows holes to be drilled and modifications to be made in the unhardened areas. Most other types of heat treating harden the entire blade, so be sure to complete all of the desired machining before hardening.



The type of wood used for making runner bodies must have several properties in order to be successful. The wood must be hard in order to keep it from being dented by the chocks (this will make the runners loose), it must glue well with epoxy, and it must be resistant to splitting. If a chart of wood properties is available, look for wood that has high hardness perpendicular to the grain, and high tensile strength perpendicular to the grain. White ash and hard rock maple are good choices. The issue of gluing is more difficult. Two woods that I know of which can be difficult to glue are oak and teak, and I'm sure there are others. The body may be one piece of wood, or may be laminated butcher-block fashion. The laminated body will be less likely to warp.

Body shape

Start with a piece of wood (for each runner) which is 36" long, 7/8" thick, and 3-1/2" high. Cut a slot in the bottom edge for the steel insert. The dimensions for the slot will be determined by the size of the steel. The depth of the slot should allow 1-1/2" of tile blade to be exposed. Cutting the slot is best done on a table saw, adjusting the rip fence by trial and error to get the right width. Place three thicknesses of 8 oz. or 10 oz. glass cloth over the blade and try to insert it into the body. The perfect fit will allow the glass cloth and steel to slide in snugly without putting too much strain on the wood.

Using the steel blade as a template, mark the location of the reinforcing screw holes on the side of the body. Drill these holes out to 5/16" diameter.

Using the runner drawing cut the body to the desired outline. Trial fit the blade into the body to insure that everything lines up properly. The runner is now ready for final assembly.


If the slot in the body is the correct width, the steel insert will be self-aligning when it is glued in. If the fit is too loose, consider adding another layer of glass cloth to adjust the fit.

Support the body with the slot facing up. On a flat surface, spread out a sheet of plastic to wet the glass cloth on (a garbage bag works well for this). Cut three pieces of glass cloth (for each runner) 38" long and 5" wide.

Coat the inside of the slot with epoxy. Wet out a layer of glass cloth on the plastic. Add another layer of glass on top of the first, wet it out, and repeat for the third layer. Coat the steel insert with epoxy (where it will be glued into the wood) and sand with 80 grit sandpaper. This is similar to wet sanding, but with epoxy instead of water.

Lay the three layers of glass cloth on top of the body, centered over the slot. Set the top edge of the blade on the glass cloth and push it down into the body. Epoxy should squeeze out as the blade is inserted into the body, guaranteeing that the joint is not glue starved. Make sure that the blade is properly aligned with the body, and leave it positioned vertically to cure.

After the epoxy has partially cured, use a razor blade to cut off the excess glass cloth at the bottom of the body.

inserts_3c.gif (9109 bytes) Fig. 3. SECTION

Once the assembly has reached a full cure, drill out the reinforcing screw holes with a 1/4" drill. Cut pieces of 1/4" threaded rod to the width of the body. Put tape over the holes on one side of the runner body and fill the holes with epoxy. Coat the pieces of rod with epoxy and drop them into the holes. Wipe off any excess epoxy and allow to cure.


Sand the body to its final shape and round off all edges except the bottom. The body should be reinforced by adding layers of fiberglass to the sides. If the top edge of the body is rounded, then the glass cloth can he wrapped over the top and down both sides, laminate the layers of cloth one at a time, being careful to squeegee the cloth well in between layers. Allow each layer to cure and sand lightly to remove any bumps and irregularities. Measure the overall thickness and add more layers of cloth to build up the thickness to 1". A layer of carbon fiber can he added with the fiberglass for additional strength and stiffness, but is not required.

Drill the 3/8" pivot hole 15" from the back of the runner and 1" from the top. Coat the inside of the pivot hole with epoxy. After curing, carefully drill out the hole to 3/8' again.

Sand the runner smooth with 80 grit sandpaper and apply a final coat of epoxy.

Many sailors add stiffeners to their insert runners. This can be done several different ways. Stiffeners can be made of aluminum angle, but they must be bolted very tightly to the runner to be effective. A wooden "wing" with carbon fiber glued to the outside edge also makes a good stiffener. A stiffener might make the runner faster by keeping it from bending under load, and also adds strength.

The runner is now complete except for sharpening the edge. Henry Bossett's article in the last newsletter outlined a good method for measuring the crown on runners. The epoxy coat will hold up fine for several years, but an additional coat of varnish or paint will give a more durable finish.

Many people have had problems with runner bodies breaking (usually just above the top of the blade). The reinforcing screws and the layers of glass cloth should provide adequate strengthening of the body. I have a set of runners built as described in these plans and have sailed them hard for three seasons. So far there are no signs of any problems. Other sailors in my region have runners of similar construction, and I’m not aware of any failures.

Most people that have made insert runners were surprised at how easy they are to assemble. I hope this has provided some useful information and the inspiration to start building.

Iceboat Runner Blades - 3 steps to help you get the most out of yours this season

By Jan C Gougeon

Iceboat nuts agree: when you increase the speed of your DN Iceboat, there is a snowball effect on the amount of fun to be had during the chilly winter season. If you want a faster, more enjoyable sail out of your DN, it is very important to get the runner blades parallel to each other. Proper alignment requires a little extra work, but can mean the difference between first and second place in this season's DN iceboat races. Here's how we do it in the icy Saginaw Valley.

Step 1

Mounting the Chocks

First, create a bend in the runner plank that simulates being on the starting line in light wind. With the plank upright and the ends supported by small wooden blocks, stand on your plank with 30 to 50 pounds of weight in your arms. Note the amount of deflection in the plank by measuring the height above the floor at the center and the ends of the plank. The runner chocks will be mounted on the plank so that the runners will be perpendicular to the ice in this position. Duplicate the bend by clamping the plank upside down to a 7 ft long 4" x 4" beam with "C" or bar clamps placed 6" from each end of the plank. Draw the ends of the plank down until the bend is duplicated. Sight across the ends of the plank to measure the amount of deflection and assure that the ends are parallel to each other.

Measuring plank deflection

There are different methods of lining up the chocks to make them parallel. We use the triangle method. A jig, made of three pieces of 1" square steel or aluminum tubing, is welded together in the shape of an equilateral triangle. The base of the triangle (about 4' long), bolts into the runner chock. (A 1" section will fit into the runner chock, just like a runner.) The two equal length sides of the triangle (a little over 8’ long) should come to a sharp point at the peak and almost touch the chock on the opposite end of the plank. The point should fall on a centerline that bisects the triangle equally, and is exactly perpendicular to the base. Drill a hole through the middle of the base tube in line with the perpendicular centerline for attachment to the chock. (Lay it out on the floor to get it perfect.)

Dry-fit the chocks in position. One through-bolt holds the tang for the shroud on top of the plank, passes through the plank, and then threads into the middle outer hole of the chock. One-inch Allen head set screws are threaded into the other five holes in the chock. The through-bolt hole in the runner plank is drilled to size. The holes for the set screws are drilled slightly deeper than the screw length, and oversized to allow for adjustment and better bonding. A 7/16" hole will do. The chock should be able to pivot slightly around the through-bolt.

After the plank, jig and chocks have been prepared, wet out the holes and the surface of the plank under the area of one of the chocks with WEST SYSTEM epoxy. Follow with a generous amount of epoxy/406 Colloidal Silica mixture. Carefully place the chock on the plank end with the triangle-jig bolted firmly in place. Align the triangle point with the center of the runner bolt hole in the opposite chock. Shim the triangle point so that it rests with the center of the 1" tubing even with the center of the hole.

Alignment Jig

Epoxy should squeeze out everywhere. With the chock tightened down on the triangle, and the triangle end centered in both front and top view on the opposite runner bolt hole, the chock will be correctly positioned from both front and top views. Note that the inner edge of the chock may be slightly raised. Clean off excess epoxy, and allow the epoxy to cure thoroughly with the chock in this position.

Thixo wedge

After the epoxy cures, mount the other chock in the same manner and allow to cure thoroughly before proceeding.

NOTE: Do not turn the aluminum triangle over. Mark the surface that is up and always keep it up. This way, even if there is an error in the triangle, the chocks will still be parallel to each other.

Step 2

Tuning the Runners

Now that you have the chocks on the plank, the next step is to fine-tune the runners. With the runner plank still clamped to the 4x4 with the same deflection used to mount the chocks, bolt the runners firmly in the chocks so their edges are parallel to the bottom of the chock. The runners should also be parallel to each other. Put two marks on each runner, 6" fore and aft of the runner bolt. Use a stick about 9' long and about 3/4" square to measure the runner alignment. Lay the stick across both runners on the aft mark. Press the stick against the edge of one runner to make a V-shaped indentation in the wood. With the indent resting on the runner edge, squeeze the stick against the other runner edge at the aft mark to make a second V-shaped indentation. Slide the stick to the marks on the forward end of the runners to check the difference in distance between the fore and aft edges of the runners.

NOTE: It is important not to push down on the stick, but to squeeze the stick against the runner with your hand. An inaccurate reading can result if the runner and plank are even slightly deflected when marking the stick.

According to Murphy's law, the runners probably won't be perfectly lined up. There are two ways to get them into line. The usual method is to grind the running edges to the correct alignment when you sharpen the runners. If the runner edges are sharpened so they are in the middle of the steel that makes the runner body, and there is still considerable error, the runner stiffener can be modified to correct the problem. One method is to sand the appropriate areas of the stiffener where it contacts the chock. Remove enough material to allow the stiffener to move to the desired alignment when the runner bolt is tightened.

If you have a little clearance between the runner and the chock, there is an easy way to remedy the situation. Remove the runners and coat the inside surface of the chocks with an automotive paste wax. Remove grease from the runner and sand the runner stiffener in the area that goes into the chock. Mix up a small batch of WEST SYSTEM epoxy and coat the runner stiffener on both sides where it fits into the chock. While the epoxy is wet, wet-sand it into the metal. Add some 406 Colloidal Silica to the batch of epoxy and apply the thickened mixture to the runner stiffeners in the same area. Place the runners in the chocks, with the runner bolts in place, but not tight.

Use thin wedges of wood between the side of the runner and the chock to get the correct alignment, tighten the runner bolt a little to squeeze out some excess epoxy, and then check the alignment one more time.

When the epoxy cures, trim off the excess and you'll have a well-fitted and correctly aligned surface that, when greased, will last a very long time.

Step 3

Mounting the Runners

The last step is to mount the runner plank on the iceboat. You want the plank to be centered and at 90deg to the centerline. The plank should also be mounted so that (from the side view) the bottom edge of the runner chocks are parallel to the ice when the boat is in powered-up sailing trim. To simulate this powered-up sailing trim, place about 400 pounds of weight in the cockpit in the area of the runner plank. With the three runners installed (place 1/4"-thick plywood under each runner), measure the bottom edge of the chock to see if it is parallel to the floor from the side view. Shim the front edge between the hull-to-plank fitting and the runner plank as necessary to get the chock parallel. Bond the shim to the hull-to-plank fitting when you are satisfied with its position.

Shimming the plank

These steps will help you to get the most out of your runners under the widest range of sailing conditions.

Note: This article is from the Fall 1989 edition of The Boatbuilder (Number 27).
The Boatbuilder is published by Gougeon Brothers Inc.

updated August 22, 1999

Runner Alignment

by: Henry Bossett - Decmeber 10, 1984

Speed in a DN is produced by a combination of the following factors: Runner Alignment, Runner type, Plank type, Mast/Sail/Boom type, Hull type, Tuning factors and Sailing technique. An adjustment to anyone of these areas.will have an affect on the performance of the boat and your final position. Each of these areas is important and large enough in scope that you must study and understand them individually, before you can hope to improve your results.

My discussion is going to be about Runner Alignment. Even if you have achieved perfection in all the other areas, improper alignment can actually keep you from sailing around a course, let alone trying to win a race. Everyone seems to have his own idea of how best to align their runners. To discuss them all would fill a book, so 1 will just relate the various areas that I check to be sure of my alignment.

The first step is to get your chocks set up on your plank so that they are parallel and capable of moving enough to align your runners. Thus, although it would be nice to just drill exact size holes for your bolts, it is better to drill oversize holes. You do not need a fancy set up to do this. Simply drawing a line across the plank end at the bolt hole locations with a carpenters square placed along the front or back aide of the plank will do. If the mounting surface on the plank is uneven you will have to smooth it with an additional layer of wood or epoxy with filler. The point here is to be sure that both the left and right surfaces are parallel to each other. If not, then your runners will change alignment as the plank bends, check for this with an adjustable level. Look at both the fore and aft direction and sideways.

Next you need to take a good look at the actual edge of your most reliable set of runners. Use these to align your chocks since they will be from front to back. It may be straight for a short distance under the pin, but most that I have checked will then wander to one side or another at the front and back. Usually the edge will also not be aligned perfectly with the stiffener. This is why you have to shim each set of runners individually on a given plank (unless you machine your own runners and have built them to perfection). I started using a small rifle scope three years ago, and was amazed at how far the edge wandered. I am not convinced that this degree of perfection is needed, but it is just one more tool that I use to be sure of proper alignment.

Once I am sure of a good edge on my all around runners, and have drilled the holes in the plank for the chocks, I drill a lot of small holes into the flat surface of the chock to help it glue to the plank. These are randomly spaced, and I also rough up the surface with harsh sandpaper. Now when you glue your chocks on (the only way to be sure of continued alignment throughout the season), they will have a very difficult time breaking free. When I finally mount the chocks, I fill all the holes with a mixture of "Gougeon" and filler, plus spread a small amount on the entire surface. This mixture will bold your cbocks in place until YOU. decide you want to change them.

I align my runners using triangle plates. The plank is mounted on the boat, and weight is put in boat to approximate my weight, the rig weight, and a small amount of downthrust such as a sma11 puff would generate. This all makes sure that I am in the most perfect alignment when the boat is coasting. It is at this point that both runners are firmly planted in the ice and thus need to track together. Any more wind and your windward runner starts to get light and alignment becomes less important.

The triangle plates that the runners sit on have their runner supports only 10" apart so that any bend in the front or back of the runner will not result in bad alignment. After all, that is the portion of the runner' that is most deeply imbedded in the ice. Plates seem at first to need machine sighting thru string set up as a large "T" on the floor, using the easy method of swinging two arcs to get the right angle "T". I then glued the supports in place and after they dried, screwed them in place for added safety. It worked perfectly, since anyone who uses my plates seems to glide quite well.

The fina1 step is to check it all on the ice. On those no wind days when most everyone is sitting around the bar waiting for the wind to come up, you will find me out on the ice "Test Gliding" my boat. You need near perfect ice to do this, but that is what we usually have at the beginning of the season anyway. Push your boat up to speed, then hop in and listen to it, as well as watching the runners. If you are out of alignment, the runners will be pulled further out of alignment and then spring back with a scratching noise severa1 times during your Glide. In springing back, they will throw ice chips, and this will tell you if you are toed in or out. Use thin shims to finally align them to the point that the boat glides further and is quiet. Now you are finally ready to beat the pants off of your buddies when they finally get back on the ice after all their Elbow exercise.

The one thing that bas become apparent in all the work that I have done to make my boat fast is that if you use your own senses and do not worry too much about Space Age Technology, you WILL. be fast. Don't get me wrong, you do have to investigate everything that promises to be a breakthrough, but the biggest breakthroughs in your own performance will come from straight forward practice, and keeping your eyes and ears open to what's right there in front of you. Good Luck this Season!


A Wood Mast Made Easy

by Paul Goodwin - US4061 - March 1990

Many people have not built a wood mast because of the apparent difficulty. There are many ways to build a DN mast from wood, but Jan Gougeon introduced one of the simplest designs yet. This new design uses pieces which can be cut easily on a table saw and requires no jigs, molds, or fixtures.

After discussing this new design with Jan, I went to work developing full size drawings. The simplicity of the design was very apparent and I was able to work out the dimensions of the pieces in a way that also made the setup easy. As soon as I had the basic drawing of the mast complete I started building the first one in my area (Detroit). The mast was assembled within a week, and I was able to sail it 2 weeks after the first discussion with Jan. One week after that, my new mast propelled me to a 7th place finish in the North American Championship. This has got to be the best hollow mast design ever!

My mast was so successful that a building/sailing partner of mine (Chip Cartwright) decided to make one. He arrived from school at 9:30 on a Friday night with a bundle of lumber under his arm, and when he went back to school on Sunday night, his mast was complete (except for the hardware). Plus, he had built a runner plank and a set of insert runners at the same time. He actually glued the two halves of his mast together, complete with aluminum luff tube, within 24 hours of arriving at my house! Understand, Chip is an extraordinary builder, but this still indicates the simplicity of the overall design.

The Basic Design

Now back to the real story--the mast construction. The basic idea is to glue a narrow strip of wood along the edge of a wider strip to produce an "L" shaped section. Then a small triangular strip is glued into the corner of the "L". This basic section is used for each mast half. Two of these sections are glued side by side, with a groove to hold an aluminum luff tube. After some final shaping, and possibly some tuning of the stiffness, an excellent mast can be produced. Fig 1 shows a cross section of the completed mast in the section below the hound.

Start by selecting some wood. The side wall (the large part of the "L") should be made from a wood which is light and not too stiff. Jan Gougeon has used Sitka spruce for most of his masts, but after studying a number of failures, he thinks that Sitka does not have adequate fatigue life in compression. One of my favorite woods for this type of application is redwood. Redwood can be purchased in clear, straight sections at most lumber yards (it is used for building decks), and has the additional benefit of being relatively inexpensive. After building my mast, I found that it was too limber from side to side. This was corrected by applying 2 tows of carbon fiber on each side wall below the hounds. Choosing a wood which is stiffer than redwood for the side walls would probably eliminate the need for any carbon fiber. You will need a 1" x 4" x 16' for each half.

The nose piece (narrow side of the "L") and the triangular corner strips should be made of a hardwood with lots of stiffness. A good choice would be ash, birch, or possibly hickory, depending on what is available locally. If 16' long pieces are hard to find, short pieces can be scarfed together (use 12:1 scarfs on any pieces going into the mast). A 1" x 6" x 16' will be adequate for the nose pieces, corner strips, and the small strips ahead of the luff tube.

Fig 2 shows an exploded view of a mast half with dimensions on all of the pieces. Note that all pieces are 1/2" thick except for the triangular corner blocks. Cut the corner blocks from the ash (3/4" thick), then have all the remaining wood planed to 1/2". It is important to cut the pieces to the exact dimensions shown. These are not rough dimensions. Use a table saw with a sharp blade, and double check your setup before making every cut. Make sure the edges to be glued are square. Cut the small strips (1/4" x 1/2") from the same wood as the nose piece.


Building the mast halves

Glue the nose and side wall together as shown in fig 2. Keep the edges aligned while applying clamps (large spring clamps work great here), and remove any glue that squeezes into the comer of the joint. Be sure to keep the pieces perfectly straight while the glue hardens. Repeat the glue-up for the other half.

If there is any glue led in the corner of the "L" from the previous glue-up, remove as much glue as possible and/or put a small chamfer on the comer of the triangular strip. Glue the triangular corner pieces into place. Draw a line 0.43" from the rear edge of the glued-up sections. Glue the small (1/4" x 1/2") strip along this line (see fig 2).

This completes the build-up of the basic mast halves. If you have been careful with the cutting and gluing, then the rest of the work should go easily.

The next step is to machine the face of the halves where they glue together. If you have access to a jointer, this step goes very fast. Simply set the halves face down on the jointer and remove enough stock to just get to the comer of the small strip in the rear, and the corner of the nose block in front (see fig 3).




If you don't have access to a jointer, then use a hand plane to accomplish the same thing. A simple (but effective) trick makes this task much easier. Clamp a block of wood to the side of a hand plane so it is flush with the bottom. This block of wood should ride on one side of the mast while the other side is being cut. Remove a small amount at a time, alternating from side to side, until the desired amount of wood has been removed. The block of wood insures that both edges are true with each other.

Once both halves are planed, the they should fit together tightly for the full length of the mast. Make a drawing of the mast cross section, cut it out, and use this template to check your assembly for accuracy.

The next step is to make a groove to accept the aluminum luff tube. Using an aluminum luff tube is important since it gives the final mast adequate fore and aft stiffness, and prevents shear web failures. The tube that I have been using has an outside diameter of 5/8" and is extruded with a slot the full length. The tube is available from Sailing Specialties in Wisconsin. An alternative is to use a 5/8" diameter aluminum tube and put the slot in it with a table saw.

One way to put in the luff tube groove is with a router. Use a 5/8" core box bit to produce the groove. A router table with a fence is useful for this step. set the fence so that you can run the edge of the mast half along the fence, cutting the groove in the correct location (see fig 4). Make several cuts with the router, increasing the depth of the cut with each pass, to produce a groove which is exactly half the depth of the tube (5/16").

An alternative method is to make the groove on a table saw. This is the way that I make grooves, and is actually very simple. Clamp a fence to the table saw at an angle to the blade. Set the blade depth to half the diameter of the luff tube (5/16"). Run a scrap piece of wood through to check the setup. Change the angle of the fence until the groove is the correct width. This produces a roughly semi-circular cut, and is fast and accurate.

After cutting the luff tube groove, put the halves together to be sure of a good fit. It is acceptable to have a slight amount of clearance around the tube, but excessive slop be avoided.

The next step is to decide if tapering of the mast is desired. Most people building wood masts have been taking advantage of the rule which allows tapering above the hounds. Tapering adds a significant amount of complexity to the construction of the mast, but I think most people should be able to accomplish it without too much difficulty. Start by deciding how much taper is desired. The basic mast is about 2-1/8" thick. A good place to start is with a taper that starts at the hounds, and drops to a thickness of 1-3/4" at the tip. This is done by planing down the edges of the halves before gluing them together.

Place a pencil mark 3/8" away from the front edge of the mast wall at the tip (do this on each half). Put a pencil mark at the location of the hound. Now draw a line which runs from the 3/8" mark at the tip to a point on the edge just above the hound. This wedge shaped section must be removed from the edge. use a hand plane with a block of wood clamped to the side as previously described, and carefully plane the edge down to the pencil line. The small strips in the rear will also have to be planed down (almost to the comer of the side wall) for a good fit on the luff tube.

The next step is to cut a 45° chamfer on the front edges of the mast. Draw a line on the nose and side wall to mark the edges of the chamfer (see fig 3). Also a draw a reference line on the side wall at the point where it is tangent with the final curved surface (see fig 5). This line will help with the final fairing. A table saw can be used to perform the chamber, but a hand plane does the best job of cleaning up down to the line. If the mast is tapered, then the size of this chamfer will be reduced where it is tapered, and you might not be able to use the table saw for the full length of the mast.


Final assembly

Blocks of wood should be used to close the base and the tip, and the tip block also contains the halyard. William B. Sarns Co. sells a halyard with a tube which works well. A better alternative is to use a sheave or small exit block at the tip for the halyard, since it makes hoisting the sail easier. Some people glue the blocks into the base and tip and install the halyard at the same time as the halves are glued together. I prefer to leave these out until after the mast has been glued up.

The hounds can either be mounted internally, or can be mounted on the outside of the mast External hounds are recommended for the first time builder, since it simplifies the building procedure.

So far so good? Then glue it together!

Prepare the luff tube for gluing. Here are two methods which seem to work:

1. Use an etching system to prepare the surface of the tube for gluing. Coat with epoxy.

2. Sand the outside of the tube with coarse sandpaper to remove any oxidation and dirt. Brush a coat of epoxy on the outside of the tube, and sand the epoxy into the tube (sort of like wet sanding).

Mix up a batch of epoxy (using slow hardener can give you a few extra minutes for the critical alignment). Brush a coat of epoxy on all glue surfaces. Also coat the inside of the mast with epoxy to seal out moisture. Mix up another batch of epoxy, and thicken with microfibers. Coat all glue surfaces with this mixture.

Place the luff tube in the groove with the slot towards the back of the mast. Place the other mast half on top and put several spring clamps along the mast. put the clamps on the mast with the pressure applied in the middle of the side walls.

Set the mast with the tube up, and make sure that the tube is in the correct position (the slot in the tube must be centered at the back of the mast). Once you are satisfied that the tube is aligned properly, add additional spring clamps to the mast. A clamp every 12" should be adequate.

If enough glue has been used, there will be a bead of excess glue along the entire length of the mast. If it appears that the joints are glue-starved, it would be a good idea to open the mast back up and apply more glue.

Sight along the slot in the tube, and make sure that the mast is perfectly straight. A string pulled tight above the slot can help with the alignment, but you can usually get it straight by eye. This step is very critical. A slight curve in the mast will make the mast favor one tack, and can cause the mast to counter-rotate (rotate onto the wrong tack) in gusty winds.

If any excess glue has gotten into the luff tube, remove it before it hardens. An easy way to do this is to tie a piece of rag to a string and pull it down the tube from one end to the other.


The final touches

The mast must be shaped to generate the final curved surface. Using a hand plane, remove material from each corner until you get close to the final shape. Look carefully at fig 5 to determine where wood must be removed. Once the corners have been planed down the mast should have a fair shape. Continue to remove material from the high spots and the curve win start to develop. Use a sanding block for the final fairing. It is helpful to make a template of the final shape from the drawing, and use the template to check the mast while you are shaping.

Cut an opening for the halyard exit in the front of the mast. The location for this should be as low as practical in order to avoid a stress concentration in the critical area of the mast (about 5' up from the base). A good location is 2' from the base, but the location is frequently determined by the length of the halyard. The exit hole should be at an angle towards the tip of the mast so the halyard can exit easily.

Cut an opening in the luff tube for the sail entry. I think the easiest entry (both easy to make and easy to get the sail into) is the angled entry shown in fig 6. The opening should be close to the base so the boom jaws are above the opening while sailing. Be sure to file or sand all sharp edges after cutting the tube.


Depending on the type of wood used for the mast, it may be desirable to cover the entire mast in fiberglass cloth. In any case, I recommend putting one or two layers of 10oz glass cloth at the hounds, and in the area where the boom jaws hit.

There are many ways of mounting the hounds, installing the halyard, and for putting a socket on the bottom of the mast. I won't go into any detail on these steps, but looking at other wood masts can give you some ideas.

If there are any questions about this mast construction, feel free to call, or write a letter if time permits. While the mast drawing can be generated from the dimensions provided in this article, I can supply full scale drawings of the mast, just send a self-addressed, stamped envelope.

Measuring Mast Stiffness

by Paul Goodwin - US4061 - September 1990
Revised February 2010 - Paul Goodwin

This article will explain how to measure mast stiffness, how to plot the stiffness, and provides the stiffness of several different masts that the author has tested. In addition, a target stiffness is recommended for people that are not sure how to tune their wood mast.

The critical area of stiffness is below the hounds, since most bending occurs midway between the hounds and base. When the mainsheet is first pulled in (on the starting line), the mast has a smooth bend along its full length. This bend is primarily caused by leech tension in the sail. As the boat picks up speed, increasing pressure on the sail causes the tension in the sidestay and forestay to increase. The rigging tension pulls down on the hounds, forcing the mast to bend be- cause of the increased compression. As the mast bend increases, the distance between the tip of the mast and the back of the boom decreases, which reduces the leech tension. As the boat approaches top speed, the tip of the mast actually straightens out, and almost all of the bend is below the hounds. Look carefully at a picture of a DN under sail to see this effect (the May, 1990 Newsletter has some good examples).

Since the mast is bending due to compression, small changes in stiffness can have a large effect on how easily the mast bends in puffs. This is similar to measuring batten stiffness by pushing the batten down on a bathroom scale. Once the batten is out of column, it continues to bend with very little increase in load.

The article by John R. Jombock on plank bend measurements (Demystifying Plank Stiffness - January 1990 Newsletter) suggests using a single weight to determine the stiffness of a plank. While this is technically correct, use at least three weights. This gives four data points, allowing a plot of load vs. deflection. Calculating stiffness from this plot provides greater accuracy than a single point measurement.

You will need three calibrated (accurately measured) weights of approximately 40 lb each, and a dial indicator for measuring deflection. Barbell weights work well, and are available at most sporting goods stores. A dial indicator has the precision required for accurate results, and tool stores sell them for a reasonable price (frequently less than $20). A dial indicator which has a range of 1" can make measurements of over 1" by resetting it after each 1" of travel. many" different styles of base are available for holding the dial indicator.

Make both side to side measurements and fore/aft measurements. Use 11' between supports to find the stiffness in the critical area below the hounds. You should also make measurements with 15' between supports, which will help determine how limber the tip is. This gives four stiffness curves for each mast, and allows for reasonable accuracy when comparing masts.

The supports for the mast must be very strong so there is no movement when adding weights. Sawhorses make good supports, but be sure they do not rock or shift when the weights are added. Putting a roller under one end to eliminate any friction will help in getting consistent, accurate results.

To measure the stiffness below the hounds, set the inside edges of the supports 11 ' apart (see figure 1).

Set the mast on the supports, about 2" from the base of the mast, clamp the mast to one of the" supports so it does not rotate when the weights are added (see figure 2).

Hang the weights halfway between the supports. Set the dial indicator over the middle of the mast, with the tip close to the point where the weights are applied. Be sure to put any clamps or fixtures used for hanging the weights on the mast before setting the dial indicator.


Making the measurements

Set the dial indicator to "0". (This is the first data point to lbs, 0 inches). Add one weight to the mast. Write down the weight and the reading from the dial indicator. Add another weight and write down the new reading. If you run out of travel on the dial indicator, reset it to "0" before adding more weight. Keep making measurements until all of the weights have been added. It should not be necessary to use more than 120 Lbs if your measurements are accurate.

Plot the results on graph paper as shown in figure 3a. If your measurements have been perfect, then a straight line will pass through all of the points. If the points are not on a straight line, then check your measurements. If the points fall above and below a straight line, then check the weights for accuracy, and use extra care when reading the dial indicator. If the points are on a curve, then check the supports for movement or bending when adding the weights.

Figure 3a - Measurements at 11 feet

Once the accuracy of your measurements are satisfactory, repeat in the fore/aft direction. Then move the supports to 15', and run another set of deflection measurements (see figure 3b). Keep two charts, one with the 11' measurements, and the other with the 15' measurements. Make comparisons by adding the plots from different masts.

Figure 3b - Measurements at 15 feet

Figures 3a and 3b show plots of the mast deflection taken on a Kenyon 2040 wing mast, a Norton wing, and on a wood mast. The Norton is one of the softer masts (from 1986). Table 1 shows the spring rate derived from these.curves (as suggested by John Jombock).

The measurements in figures 3a and 3b were made with 20 lb weights. Notice how close all of the measurement points are to a straight line. No mast starts out limber and becomes stiff, or vice versa (except in the case of a mast with a wood stick inside for support). So look for measurement errors if you plot your results and the points do not fall on a straight line.


Comparing different masts

When looking at figurea 3a and 3b, the lower a line is on the graph, the stiffer the mast is. This rule shows that the Kenyon mast is stiffer than the Norton on all curves. Also, all of the masts are stiffer fore and aft than side to side.

Looking at the plots more carefully, the side to side curves show the effect of tapering above the hound. In the top graph (measured below the hounds), the increase in stiffness between the wood mast, the Norton, and the Kenyon is almost equal. In the bottom graph (measured from tip to base), the difference between the wood mast and the Norton is much greater than the difference between the Norton and the Kenyon. This is because the tip of the wood mast is very soft.

People building wood masts can use these methods to compare the stiffness of their own masts. The wood mast in figure 3 is a mast which has been very fast, but is quite limber. A mast this flexible can be difficult to sail in light wind, and requires sheeting out in heavy air to prevent over bending.

If you have never sailed a wood mast before, then try using a stiffness close to the Norton wing below the hounds. If you're comfortable with a softer mast, then try a stiffness similar to the wood mast in figures 3a and 3b.

Many wood masts which have been going fast are stiff fore and aft (stiffer than a Norton wing), and limber side to side (5 - 10% more limber than a Norton wing). The stiffness in the tapered section above the hounds has been hard to understand, with masts going fast with either a stiff or flexible tip.

One problem with a soft, tapered mast tip is that it reduces leech tension. This flattens the head of the sail and reduces power, particularly at low speeds- to compensate for this, many people use sails with more luff curve above the hounds . A wood mast could have no taper and the same stiffness as the Norton wing. This mast should sail like a Norton, but not break so easily.

Notice that all of the masts are at least 3 times as stiff fore and aft as they are side to side. If a mast is not stiff enough fore and aft, then it will not rotate very well when tacking. This can be demonstrated by sheeting the sail in (not to tight) and rotating the mast. A good mast will snap back and forth from tack to tack. A mast without enough fore and aft stiffness will not snap across, and will be more likely to rotate to the wrong tack in puffs.

One note of caution when tuning wood masts. Adding carbon fiber tows on the outside of a mast provides a fast, easy, and inexpensive way to increase stiffness. However, the stiffness will increase for several days after applying the carbon fiber. Therefore, add enough carbon fiber to bring the stiffness to a level slightly less than desired. Then make the final stiffness measurements after allowing a week or more for full curing of the epoxy.

This article answers some of the questions that sailors have asked about measuring mast stiffness. It should also encourage more people to make accurate measurements of mast stiffness. The techniques described here may sound too technical and complex, but the results are worth the effort. After completing the initial setup, stiffness can be measured in about 1/2 hour per mast. Transferring the urements onto a graph requires about 15 minutes, and provides a permanent record of mast stiffness.


Plank Design Calculations

Plank Design Spreadsheet (plank.xls)38.5 KB

by: Paul Goodwin

I hope to (soon) find the time to write an article descibing how to design and build an iceboat plank.

In the meantime I felt it was a good idea to pass along a plank design spreadsheet that was put together by John Bushey. This spreadsheet calculates the stresses on a plank and estimates the bend properties based on a three-piece plank design (core with top and bottom skins). You enter all the design parameters such as core and skin thickness, wood modulus (stiffness), plank width and length, etc.

The only parameter that can be hard to find is the wood modulus, so a few have been added to the spreadsheet to get you started. This is the only real gray area, and actual wood modulus can vary widely from the published numbers.

To use the spreadsheet, you enter the parameters in blue, and it calculates the numbers in red (deflection and stress). To use the spreadsheet you will need to have Microsoft Excel (or another spreadhseet that can import Excel files).

Repair and Construction

Broken Screw Extraction

by: Bob Dill - December 1987

Do you use a stud and plate to hold your plank on?  Do feel like a frustrated dentist trying to dig broken screws out of your plank and hull with a hand drill?  If so, Chuck Bond from Westford, VT (US 4031) has found the answer to one of your least enjoyable tasks.

Chuck figured out that he could make something like a miniature hole saw with a short piece of thin walled metal tubing with the right internal diameter.  The ID should be slightly larger than the screw shank.  Chuck has used various things as tube: broken radio aerials, thin brass tube, copper pipe, or what ever was handy at the time.  He felt radio aerials tube worked best.  Another alternative is to machine a drill especially for the task as shown below.

Small teeth or slots are filed into the bottom edge to help it cut.  This hollow drill is pulled out of the hole frequently to remove the sawdust.  The center hole should also be kept clear.  The teeth can be set up for left hand (counter clockwise) drilling.  The screw will usually back out more quickly when drilled this way (with the drill in reverse).

After the screw is out, there is usually a little bit of its original hole at the bottom of the new hole to center the new screw. Fill the hole with epoxy, put in the new screw and make sure the plate is in its proper position.  If the screw breaks again the process works just as well with an epoxy potted screw as a screw in wood.

The following drawing gives approximate dimensions for one of these drills made on a lathe from 3/8 drill rod.  Drill rod can be hardened easily although being hard isn't all that important.  This drill is designed for the #8 stainless screw Sarns sends with stud and plate sets.

Screws usually won't break unless they get loose first or unless you hit something (when they should break).  When they are tight they share the load.  When they are loose they all get to share the load; a couple at a time until they all break and you get dumped very abruptly on the ice (usually just past the windward mark).  Put them in with epoxy and check them periodically to make sure they stay tight.

screw extractor