Sunday, November 30, 2008

Windsurfing Mast Kevlar Wrap Protection

For the last 10 years I have been applying a wrap of light weight Kevlar bi-directional cloth to my carbon windsurfing masts to protect them for wear and abrasion where the boom attaches to the mast. I have found this to be a very effective method to prevent mast damage over time. It is also interesting to note that the famous American windsurfing wave mast maker “POWEREX” has also been using a Kevlar wrap around the boom area of their RDM wave masts for the last few years to give them added protection from boom to mast wear.
I am now also going to experiment with doing the same thing in the area where my race sail cambers mate with the mast and cause wear from the constant back and forth rotation over time on the masts.

The materials you need for this are:

1. Lightweight (1.7 – 2.5 ounce/square yard) bi-directional weave Kevlar cloth

2.5 Ounce/Sq.yd bi-directional Kevlar cloth

2. Kevlar cutting scissors or shears

Kevlar Cutting Scissors

3. Quality 2 part Epoxy resin and hardener system
4. Roll of 2-3” wide “Peel Ply” Dacron cloth (

Peel Ply

5. 60, 100,120 -150 grit dry sand paper
6. 220 grit wet/dry sand paper
7. Black enamel spray paint
8. Epoxy mixing cups, protective latex gloves, safety glasses,
9. Acetone for cleaning up wet epoxy resin and mix spills etc.
10. Plastic “Squeeges” and small disposable paint brushes

Plastic squeegees and disposable epoxy brush

11. Light weight epoxy filler. I use West System Microlight 410. See: or

12. Epoxy scraper

The process to apply the Kevlar is as follows:

Identify the high and low boom attachment points on your mast and determine distance between the two. Then add about 4” (10cm) to the overall measurement. This is to allow some of the Kevlar wrap to extend a little about and below the boom attachment area on the mast. I typically cover about a 16”(40.5cm) section of my mast.

Measure the circumference of the mast by wrapping a piece of paper around it in the area where the Kevlar wrap will be applied. Allow for about a ½” (1.5cm) overlap.

Lay out Kevlar wrap on clean paper or cloth to prevent dirt or other contaminants to touch it. (Keep in clean). Using a felt tipped pen and ruler, mark out a section of the cloth (Length x width) based on your measurements. Then using your Kevlar scissors*, cut the cloth carefully. Once cut handle carefully and don’t stretch the cloth out of shape. Set is aside for later use. (Note: Kevlar is very tough and will quickly dull a pair of regular scissors)

Using plastic tape wrap tape around mast about 1 cm above and below the upper and lower measurement marks you will use to determine where the Kevlar cloth will be applied on the mast. Then wrap newspaper around the mast for about 40 cm above and below the tape. Use more tape to keep the newspaper on and seal the edges of the paper. This is to prevent accidentally getting wet epoxy etc. on the mast in places you don’t want it.

Take 120 grit sandpaper and lightly sand the entire surface of the mast all around where the Kevlar wrap will be applied. Only sand enough to just rough up the surface. Don’t cut into the carbon fibers themselves. The purpose of this process is to create more surface area for the epoxy resin to bond to the surface of the mast.

After sanding brush off all sanding dust and then use a damp cloth to wipe off remaining sanding dust. Finally use cloth dampened with acetone to wipe off the area again. This will get rid of any skin oil, or other substances that may inhibit getting a good bond between the epoxy resin and the mast.

Support the mast up on blocks so that you can rotate it around and easily reach underneath it as you apply the Kevlar wrap.

Using small pieces of tape, tape the long edge of the Kevlar cloth to the mast area you are going to cover.

Mix your epoxy resin and hardner according to instructions. Then using your small brush begin painting on a thin layer of epoxy onto the Kevlar cloth. As it saturates the cloth use your squeegee to spread it out evenly and ensure it is pressed down and has completely wetted out the cloth.

Continue this process as you rotate the mast around wetting out the Kevlar wrap more and more until you are almost at the edge that has been taped. Then carefully remove the tape holding the edge of the cloth and continue wetting out the Kevlar wrap. Let the edges overlap and again use your squeegee to smooth out the overlap.

Once you are finished applying the epoxy resin to the cloth and have smoothed and straightened it all out the best you can then you are ready for peel ply.

Using your plastic tape, apply a wrap of tape around each end of the Kevlar wrap. You only want the tape to overlap the Kevlar by about .75 -1cm max. This is to ensure that the edge threads of the Kevlar cloth will be epoxied down flat against the mast and will reduce the need to add more filler and sanding later.

Cut lengths of “peel ply” 10 cm’s or so longer than the Kevlar wrap. Lay one along the wrap and use your squeegee to wet it out with the epoxy resin mix already applied to the Kevlar. Also use your brush to apply a little more epoxy to the outside of the peel ply in areas where there is not enough resin underneath to fully wet it out. You may need three lengths of peel ply to cover the entire circumference of the mast.

Wait 24 hours for the epoxy to fully harden. Pull the “peel ply” off. The peel ply will smooth out and help evenly fill the weave of the Kevlar cloth resulting in less filling and sanding later.
Pull or cut off tape and newspaper.

Now use an epoxy scraper to carefully scrape down any hardened epoxy bubbles. Ridges, bumps etc. Use caution not to scrape into the Kevlar cloth.
Wipe dust and wipe again with acetone. Reapply newspaper and tape about 1 cm higher and lower than before.

Mix epoxy resin and hardener according to instructions. Add lightweight epoxy filler and stir mix until it is a smooth, tooth paste consistency type mix. Use squeegee to spread the paste all over the Kevlar wrap area. Ensure all low areas and weave of cloth are filled. Smooth off as best as possible and remove excess to avoid more sanding that you need to do.

Filler applied and hardened. Ready for sanding
Let harden 24 hours. Then starting with 60 grit sand paper and sanding block, sand down thick high areas. Use caution not to sand too deeply or into Kevlar. After this, use 100 grit, then 120 or 150 grit to continue to sand down most of the filler all around the wrap. Again, use caution not to sand into the Kevlar cloth.

Try to sand the top and bottom sections so that you “taper” the filler from the edge of the Kevlar wrap down to the mast carbon surface. Note: You cannot sand Kevlar so be careful. If you see a “fuzzy” texture appear you have sanded into the Kevlar.

Once satisfied with above sanding and smoothing. Wipe off all dust and again wipe with acetone. Let dry thoroughly then use your black spray paint to cover entire surface area of the wrap.
Once dry use 220 wet sandpaper with water, to lightly sand again the painted area. This will additionally smooth out remaining rough or high spots. After drying repaint additional time.

Once paint has thoroughly dried and hardened, go sailing and enjoy the knowledge that your mast is now protected from boom wear for many years to come.


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