Patching Hole in Kevlar

So a friend of mine says to me last night that he has this nice kevlar canoe that he got as a wedding present. Seems a tree limb fell in the backyard and went through the hull. He wants to know how to make the repair.

Well, you folks probably know that if it ain’t wood and canvas, I ain’t got much use for it. I don’t even know if Kevlar trees grow around here!

So, I plead to the all knowing forum. What is the best way to make this repair? I dunno the diameter of the hole, but if a limb went through kevlar, I suspect it was a substantial limb, leaving a substantial hole.

Thanks in advance.


On Randys boat
we had a limb sorta go through it, except we were in it and the limb was underwater…

We cleaned sanded the Gel coat and put layers of 2/4 oz Glass over it. filled in the hole with epoxy and micro balls. sanded and re gel coated. If your freinds boat is a skin coat teh the sanding is more problematic. Teh little skin coat repair I have done mostly was confined to cleaning up the kevlar, shaving down the fibers that were too high, glassing over it, worked great, looked loosy.

Wenonah has a video on composite repair I recommend highly.

laminate repair
Find what resin was used to laminate the hull and if it has gel coat. Acquire appropriate resin, kevlar, peel ply and gel coat.

  1. Debreed the tear with a very sharp implement.
  2. Force the hull back into shape with external saran wrap, cardboard or shaped wooden forms if necessary.
  3. Sand a rectangular area 2" larger in each dimension than the tear area in the hull interior; clean w/ acetone.
  4. Wet the interior out with resin and apply a small Kevlar patch, then two more successively larger patches.
  5. Cover the edges of the largest patch with peel ply and wet it out.
  6. When the patch has gone through exotherm, turn the hull over, remove any forms used, debreed again, apply resin to open edges if needed.
  7. After any external resin has “kicked”, sand, 80 grit, clean w/ acetone and apply gel coat.

    8… Sand gel out 80, 120, grit dry, 320, 600, 1000, 1200 wet, then apply rubbing compound.

    send an email to info@placidboatworks for more completye info.

Even though the exterior of the boat

– Last Updated: Apr-12-08 6:40 PM EST –

in question probably isn't Kevlar, but is E-glass or S-glass?

First, come on, CE, for repairs epoxy will work as well as vinylester, and epoxy will still be viable for next year's repair, while vinylester will set up, even in a clean glass container. (Personal experience, vinylester provided by Vladimir Vanha.)

Second, even if there were such a thing as a pure Kevlar boat, is there any reason to use Kevlar as an exterior patching material? Well, yes, there is one reason. On whitewater boats, if the stern is whomped in the center by a ledge, the S-glass may split not a the point of impact, but laterally, at the chines. And that is one place where using Kevlar for the repair (or CAP if one is perversely using vinylester resin) will produce a better result. Usually, however, S-glass, or even E-glass, will be better for exterior repairs.

Inside the boat, that's where Kevlar usually will "shine." But I have seen internal Kevlar layers fail at the chines of "chiney" boats, and in that case, other cloths with more compression strength may be better for repairs. Even E-glass.

As for layered patches, I stick to classic Charlie Wallbridge/Boatbuilders Manual advice. The largest patch goes on first. Always. Then concentrically, on down to the smallest. This always applies, inside or outside the boat. It is sometimes hard for people-in-general to understand why the opposite approach should not be used, that is, to apply the smallest patch first, and then so on up to the largest. The reason is that smallest-to-largest leaves transition zones inside the laminate where they may provide a location for future breakage. If the transition zones from layer to layer are kept on the outside of the laminate, then they can be mitigated by sanding, so that transition does not lead to dissolution.

Another reason is that, if the largest patch goes on first, the fibers of that patch bridge the dished-out layers of the original laminate, and hold them together. Subsequent smaller patches contribute to this effect. If one tries to put the smallest patch in first, then subsequent patches do not bridge the layers of the original laminate.

But I digress/transgress/regress. Your mileage may vary, but it will be higher than mine.