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One Design Fix

This information is from Windsurfer International repair kit instruction paper(1983) on how to repair the Windsurfer One - Design. The author of this information is Lional Brodrick . The repair kit listed below does not exist any more but you can buy the components at fiberglass suppliers and marine supply shops.  In 1983, West System was the bonding system that Windsurfer International recommended, you can probably use another manufacturer in place of West System. You use this information at your own risk (In other words, I am not responsible if you screw up your repair).


I Repair Kit

II. Preparing the Hull

III. Moisture caused curing problem and solutions 

IV. Split daggerboard well repairs

V. Split mast step or mast step cracks and delaminations

VI. Mast step replacement

VII. How to install footstaps inserts

VIII. Board bending

IX. Hot air welding / polyethylene




1. Split daggerboard wells

2. Split mast tee slots

3. Footstrap insert installation

This repair kit was specially designed by Windsurfing International for the repair and modification of Windsurfer sailboard. Please refer to the following list of materials and instructions, which must be followed to insure a good repair.

We have chosen WEST SYSTEM TM brand epoxy for our repair kit for a number of reasons. WEST SYSTEM was originally developed for wooden boat construction with the primary idea of creating a 100% water barrier. The formulation of WEST SYSTEM epoxy has given us a 100% water barrier, an unbelievable adhesion quality, and is not brittle. 

The use of WEST SYSTEM epoxy is quite simple, provided the following instructions are followed carefully. Included in the kit are: 

  • 105 Resin, 2 lbs. and 205 Hardener, lb., Measuring cups

(I have had the epoxy over heat and delaminate the board.  You might want to use a slower setting harder, like the 206.)

The 105 Resin and 205 Hardener MUST be mixed at a 5:1 ratio -FIVE parts resin (by weight or volume) to ONE part hardener (by weight or volume). Two measuring cups, calibrated in both milliliters and ounces, are included in the kit for ease and accuracy in measuring. [CAUTION: You CANNOT make a hot or cold batch with WEST SYSTEM epoxy. The ratio must be exactly 5:1 or you will have an uncured mess!] 

After measuring, mix the resin and hardener in one of the mixing cups provided for approximately 20 seconds to ensure a proper blending.

The mix of resin and hardener will give you a pot life (or working time) of approximately 5 to 20 minutes, depending on the air temperature. We recommend mixing in small quantities (approximately 4 ounces) to minimize waste. 

2. 406 Colloidal Silica, 3 oz.

The 406 Colloidal Silica is thickener which can be added to the resin and hardener mixture. Varying the amount added will change the density of the mixture. (Promotes impact resistance but is difficult to sand).

3. 409 Microspheres, 3 oz. (4O9 has been replaced 407 Low-Density Filler, check with West System for equivalent) 

The 4O9 Microspheres are also used as a thickening agent and are recommended for use when sanding is required as they produce a compound less dense (and hence easier to sand) than that produced by the addition of Colloidal Silica. 

4. 10 Mixing Sticks

 The mixing sticks are used to mix the resin/hardener and fillers together. 

5. 501 White Pigment, 1 oz

The white pigment is added to the resin/hardener mix at approximately 2% by volume. [CAUTION: Do NOT use any other type of pigment with WEST SYSTEM epoxy. It will NOT work.] 

6. Two 16 oz. Mixing Pots 

These pots are reusable, and may be easily cleaned by breaking the epoxy out of the bottom of the pot once the mixture has cured. 

7. 3 Pairs Disposable Gloves 

Use these gloves whenever working with the epoxy. 

8. Curved Tip Syringe 

The curved tip syringe is used to inject the epoxy mix into small areas. The tip may be cut to custom fit the area needing repair. The syringe is reusable providing the resin has been pumped out prior to curing. The same procedure used with the mixing cups may be followed to reuse the syringe. 

NOTE: Please refer to individual instructions and precautions on labels of epoxy, hardener and fillers. 


It is important that the hull be thoroughly dried prior to epoxy repair. If water is left inside the hull during repairs, it will boil and steam during the chemical reaction period. 

A. How to Dry the Hull

  • Most repairs require drilling " holes. After drilling boles, stick your finger inside and feel the foam. If it feels wet you must dry the hull. This is a simple, but time consuming procedure.
  • Roll up sheets of paper towel so they fit snugly into the " boles (The sheets should resemble cigars).
  • Press the paper towels into the hull, being sure that the exposed 1" - 2" "wick" is pointing down. Capillary action will draw moisture into the paper towel. The outside air will constantly dry the towel. If a lot of moisture is in the hull, it might take up to three weeks to dry.
  • One way to speed up the process is to dry the paper towel "wick" occasionally with a blow dryer.

A. Epoxy overheats and bubbles--

    1. Allow epoxy to overflow freely.

    2. After epoxy turns rubbery, scrape and clean epoxy from void.

    3. Follow Section A., steps 1 - 4, before attempting repair. 

B. Plastic distorts--

  • If heat and steam begin to distort the plastic, immediately apply cool towels or "compresses" to the affected area. 


Most splits in the daggerboard well area usually occur along the trailing radius and the bottom of the hull. (Figure 1) 

Additional materials required

1/8" drill bit                                                  Acetone
" drill                                                         2" wide masking tape
Sandpaper - 80, 120, 220, & 320 grit          razor knife 


A. Drilling: (Figure 2)

1. Drill a " hole, about 1/4" deeper than the split, directly  behind the daggerboard well on the bottom of the hull. 

B. Inside Tear:

1. Scrape foam from behind aluminum support on either side of the tear.

2. If the aluminum support is torn, reshape with screwdriver and pliers. 

C. Bottom Tear: (Figure 2)

1. On the bottom of the hull the most frequent tear is 2" - 3" in length. Drill a 1/8" hole at the end of this tear.

2. Use a razor knife to remove approximately 1/16" - 1/18" of polyethylene plastic from either side of the tear.

3. Remove " of foam on either side of the tear approximately " thick.

4. Turn the board right-side up to knock out the loose foam. 

D. Sanding 1:

1. Rough the area, approximately 2" - 3" , around the bottom split using the 80 grit sandpaper. The plastic must be roughed   well for the epoxy to satisfactorily adhere. 

E. Cleaning:

1. Using Acetone, clean the area inside the daggerboard well and along the bottom of the hull. 

F. Sealing: (Figure 2)

1. Using the 2" masking tape, seal off the inside of the daggerboard well to prevent the epoxy from leaking out. 

C. Batch 1:

1. Mix the epoxy and hardener at a ratio of 5 parts epoxy to 1 part hardener (by volume or weight).

2. Add COLLOIDAL SILICA until the mixture resembles pancake batter.

3. Add a dab of concentrated white pigment.

4. Pour the epoxy, filling no more than 1/3 of the void. to set and cool, approximately 25-30 minutes. 

H. Batch 2

1. Mix the second batch according to the same formula as the first.

2. Pour in the epoxy, filling no more than 2/3 of the void.

3. Allow this to set and cool


1. Construct a small overflow reservoir 1" - 2" around the tear using masking tape. (Figure 2)

2. Add MICROSPHERES to mixture to promote thickening (should attain pancake batter consistency).

3. Allow this batch to overflow into the reservoir area. 

J. Sanding 2: (Figure 3)

1. Allow the epoxy to harden and cool completely.

2. Using a variety of sandpaper grits, sand the hull bottom down to not less than a 1/8" thickness.

3. The inside of the daggerboard well can be filed with a round file or a piece of " dowel wrapped with sandpaper.

4. To complete the repair, it is suggested that you round off the trailing corner of the daggerboard well.


Additional Materials Required:

Same as for split daggerboard wells, plus: Silicone or petroleum jelly, 20 lb. weight.

Mast-step delaminations, although rare, are generally caused by two things:  Applying too much duct tape to the mast-tee, or railriding or ever-rolling your Windsurfer. The two usually go hand-in-hand - excessive use of duct tape breaks down the foam on either side of the mast-step and starts compressing the foam outward; railriding causes the delamination. Repairs to the mast-step area can be made by following these simple procedures: 

A. Drilling: (Figure 4) 

1. Using a " drill bit, drill 4 holes
--one in front, one behind, and one on either side of the mast-step.


B. Sanding 1:

1. If there is a crack inside the mast-step, roughen it well with 80 grit sandpaper.

2. Sand the area around the " holes. 

C. Cleaning:

1. Clean the entire area with Acetone. 

D. Sealing:

1. Using 1" or 2" masking tape or duct tape, seal off the area inside the tee-slot. 

E. Universal-Tee: (Figure 5)

1. Protect the Tee with either petroleum jelly or silicone.


F. Batch 1:

1. Mix the epoxy and hardener in a ratio of 5 parts epoxy to 1 part hardener (by volume or weight).

2. Add COLLOIDAL SILICA until the mixture resembles pancake batter.

3. Add a dab of concentrated white pigment.

4. Pour the epoxy filling no more than 1/3 of the void.

5. Insert the Tee into the mast-slot and apply pressure with the 20 lb. weight. (Figure 6)


6. Allow mixture to cool, approximately 25-30 minutes.

G. Batch 2

1. Mix the second batch according to the same formula as the first.

2. Pour in the epoxy filling no more than 2/3 of the void.

3. Allow this to set and cool. 

H. Batch 3:

1. Form a reservoir with 2" masking tape around each hole.

2. Add MICROSPHERES to mixture to promote thickening (should attain pancake batter consistency). 

I. Sanding 2:

1. Allow the epoxy to harden and cool completely.

2. Using a variety of sandpaper grits, sand the hull deck down to not less than 1/8" thickness. (Figure 7)


3. The inside of the Tee-slot can be sanded with a " dowel wrapped with sandpaper. The repair is now complete.



The new Windsurfer Competition is supplied with a replacing plastic mast-step. This same mast-step can be used to repair the original one-design Windsurfer.

A) Cutting

1. Use a razor knife to cut an opening through the plastic of the hull that corresponds with the new mast -step. The safety leash bar should be closest to the bow (pointed end).

2. Cut an opening into the foam 1" deeper than the mast-step. A router can be used since the closer the fit the better.

3. Cut a piece of scrap wood, 3/4" X 1" X 6". Use two stainless steel screws to attach this to the bottom of the mast-step.

B) Preparing the Deck

1. Test fit the mast-step.  It should fit snug, and the flange will overlap onto the deck.  Remove the mast -step. Sand the area that will be overlapped using 80-grit sandpaper.

2. Wipe the deck with acetone or MEK.  Place masking tape on the deck excluding the overlapped area.

3. Place masking tape over the top of the mast-step. Cut an opening for a mast-tee. Press a mast-tee into place and seal the gap with masking tape.

4. There are two empty spaces beneath the safety leash.  These should be filled with foam or wood.

C) Mixing the Epoxy

1. Mix the epoxy and COLODIAL SILICA so that it is like pancake batter.

2. Pour the epoxy into the opening.  Work the mixture up along the sides.  Spread some onto the mast -step.

3. Press the mast-step into place. Some epoxy should ooze up. This can be scraped away.

D) Applying Weight - It is very important that the mast-slot be kept inplace by force.  This can be done with weights or clamps.

E) Finishing

1. After the epoxy is no longer tacky, but before it hardens, it is a good idea to remove the masking tape.  Leave the tee in place.

2. After the epoxy is hard, small spills can be popped loose with a knife or sanded flush.

3. Mix an extremely thick batch of epoxy adding microspheres.  Use this as a caulk between the flange and the hull.

4. After this hardens, it can be sanded to form a smooth transition.



Additional materials required: 

2 Aluminum (Rocket) inserts for each strap         razor knife
(3" insert - P.N. 10625)                                     1 can Acetone
(1 " insert - P.N. 10626)                                 1 roll of 3" masking tape
1 footstrap for each strap installation                    paper towels, grease pencil
11/16" drill bit

Take your Windsurfer for a sail in about 20 knots of wind. Look down at your feet to see where you are standing. Take a grease pencil and mark off the approximate foot locations. (Note: Adding footstraps to a stock Windsurfer will not convert it to a Rocket board. The addition of straps to the Windsurfer board will, however, improve your ability to perform in heavy air and high seas.)

A. Footstrap Insert Locations: (Figure 8)


1. On a stock Windsurfer, your front foot will be somewhere between the back of the mast tee and the front of the daggerboard slot.

2. The angle for the front straps should be somewhere between parallel to about 45 degrees from parallel to the length of the board.

3. Back straps usually run behind the daggerboard well, either down the center or in pairs.

4. The distance between inserts per strap should be 6 1/2".

B. Drilling: (Figure 9)

1. Carefully mark where the holes will be.

2. For the 1 " insert, drill the hole 1 3/4" deep.

3. For the 3" insert, drill the hole 1 3/4" deep. Install footstrap screw into one 3" insert. Press hollow portion of insert into foam until insert is flush with deck. Use screw to remove insert before pouring epoxy.

4. Remove a small amount of foam from around and beneath the lip of the hole.

5. Using screwdriver poke three small holes into the foam.
 C. Masking: (Figure 10)

1. Cover each hole with 3" masking tape.

2. Use a razor knife to cut around the holes.

3. Take a strip of masking tape and place it face up on a table. Take each aluminum insert and place it face down on the table.

4. Use razor knife to cut the masking tape around the inserts. This prevents the epoxy from ruining the threads. 

D. Mixing Epoxy:

1. Carefully mix the epoxy and hardener in the same 5:1 ratio (by volume or weight)

2. Add COLLOIDAL SILICA until the mixture resembles pancake batter.

3. Add a dab of concentrated white pigment.

E. Pouring the Epoxy:

1. Pour the epoxy about halfway up each hole.

2. Wait a minute or two, then check the first hole. If epoxy has saturated into the foam, refill hole to the halfway mark. 

F. Placing Inserts:

1. Carefully press inserts into the holes until they are just flush with the deck. DO NOT PRESS TOO FAR.

2. Wipe away any epoxy that has overflowed.

3. If no epoxy overflows, you have not placed enough in the holes. Remove using thin knife or screwdriver, then add more epoxy. 

G. Clean-up:

1. When the epoxy becomes rubbery, you may start to clean the area.

2. Peel off the masking tape and clean the area with Acetone.

3. Be careful not to touch the aluminum inserts themselves, as they will stay quite hot for some time. 

H. Curing:

1. The epoxy should cure overnight, and in the morning you'll be able to install footstraps. Then only one step remains - cruising on your new footstrap board!

NOTE: The addition of inserts to the Windsurfer sailboard is considered a modification and voids the one year hull warranty (regardless of who installs the inserts). Although it is legal to install footstrap inserts into the standard Windsurfer hull, you may not race with the footstraps attached in an IWCA sanctioned event . 

Additional Insert Uses: Skeg Box -The following repair procedure should be used if your skeg box insert breaks beyond repair: Knock the original insert out of the way using a screwdriver. Do not try to remove it from the inside of the hull. Replace the insert using the same method recommended for installing the footstrap inserts. NOTE: New insert will have to be cut to fit. 

Towing/Safety Leash -

A safety tow leash may be installed in the bow of the board using the same installation technique as for footstraps. This may double as a safety leash hole for the universal as well.


A unique feature of the Windsurfer is its versatility in a variety of sailing conditions and its many possibilities for individual modification. For example, the way you adjust your sail, flat or full, depends upon whether it's windy or not. Similarly, the amount that you rocker or scoop your board reflects where and how you do your sailing. A sail that couldn't be adjusted wouldn't be very versatile; in the same way, if we couldn't apply a little heat, some heavy weights and a bucket of water to transform it from a flat water freestyle board to a banana-shaped wave board, the Windsurfer wouldn't be as versatile as it is.

Below is a chart showing the various possible and what they're good for.



The most popular way of scooping a board is the "solar oven" method. Buy yourself a solar oven (a large "hefty" trash bag), tape it to the deck of your board, and leave it in the sun and out of the wind for one to two hours on a hot sunny day.  (Note:  Cooking time varies with latitude and weather.) When it's well done, support each end on a chair, remove plastic, and stand on the deck just aft of the Windsurfer logo.  Baste with water until thoroughly cooled. The hotter you get it, the more you bend it and the better you cool it, the bigger your board scoop will be.


Taking the rocker out of a board was a problem which went unsolved for years, even after people were scooping boards successfully.  The big breakthrough came in Hawaii during the Great World Cup Calm.  Mark Robinson and Ken Winner left his board "on a rack" for a whole day in the tropical sun. The resulting reverse rocker Rocket turned out to be the fastest board in Hawaii.  It's not certain, however, that making an "S" board out of a standard Windsurfer would make it faster.  To reduce or eliminate the rocker in your board, put it on a rack as shown in the rough diagram, leave for a few hours, cool it off thoroughly, stand it on end, and measure the results with a straight edge. Check the rocker again in a day's time to be sure that the board is retaining the desired shape. It's unlikely that you will have the nerve to bend your board enough to give it zero rocker on the first try, so expect to do it again.


Board bending is an art, not a science.  Since boards are used in different environments and differ slightly in the amount of curve built into them, more or less extreme methods are required to achieve a desired shape. While you do your own experiments, keep in mind the following points:

1.You'll need to over bend the board two to four times the amount of curve that you want it to retain.

2. Polyethylene shrinks up to five percent when it is heated and cooled.

3. Polyethylene can be stretched by heating and applying stress.

4. Too much heat (as can occur with heat lamps) can cause delamination from foam and bubbles in plastic.

5. Too much force applied over too small an area (tight radius bend) can break foam or badly wrinkle polyethylene.


We use the hot air welding gun manufactured by Leister Co. and distributed in the United States by the Robert R. White Co.  The gun costs $385.00(1981 price).  Special tips are required; these cost approximately $80.00 each. The most often used tip is ______ . This tip uses 3/16" extruded high density polyethylene.  Also needed are scrapers for cleaning the polyethylene.

The cross-linked polyethylene that we use is known as a thermo-set plastic.  This means that once the plastic is heated and melted, it cannot be melted without burning it. You need to use a material that is the same as the skin. ( Therefore, the kind of weld a hot air gun produces is not a true fusion of the plastic (as in metal welding, brazing or aluminum helearcing).

Experience bond and controlling the three variables are needed to produce a successful bond. Three variables are:

1. Cleaning both the polyethylene board and rod with a scraping tool.

2. Controlling the temperature of the tip of the gun at 3OOC.

3. Drawing the gun across the weld at a steady controlled rate.


1. Do not try and melt the extrusion into the board.

2. Do not hold the gun for too long in one spot. It may bubble and delaminate the hull.

3. Allow the weld to cool completely before testing the repair.

The repair can be finished by shaving the weld flush with the hull with a sure form or sanding.

The hot air welder can be used to repair daggerboard wells, mast-steps, skeg boxes, and replace large hull sections that have been damaged.  When replacing hull sections, mast-steps, and daggerboard wells, it is best to cut out the sections with 2-3" deep of foam attached.  Bond this to the hull with the epoxy and then seal the perimeter with the hot air welder.

The hot air welder has other shop functions:

1. Can help promote epoxy curing time.

2. Can help install and remove hull decals.

3. Can dry out moisture in hulls.

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