hull repair gel/kevlar/foamcore

-- Last Updated: Sep-16-07 3:44 PM EST --

We had an interesting meeting with a cypress knob today. We gashed RedCrossRandys BigBlueMinnesota2 . About 5 inches long at the 2" water line. We are through to the foamcore. My thought is to tape off the area,sand off the gell coat, build up the gash with microballs and epoxy. Then top it with either glass or kevlar. Finally throw some gel coat over all.
My question is should I use the Microballs and thickened epoxy or should I try to use a spray foam to build up the gash?


– Last Updated: Sep-15-07 9:31 PM EST –

Microballoons, I would consider it as a fairing compound, very light but very brittle.

Microspheres is heavier but much stronger for a structural repair.
edit: I guess West now calls it 404 High-Density Filler, showing my age.

Just me..

Call Wenonah for advice. Once the
gash is filled, glass is the best material for an outside repair. When you are removing gelcoat, plan enough room so you can get three concentric cloth layers in place, the largest first, down to the smallest. You can plan the number and thickness of layers by the thickness of the original laminate.

How about an inside repair ?
Same race - different boat - A different hole.

-Comp Cruiser - full steam into a partially submerged log. Punched a small hole dead center in the bottom of the bow right where it curves at the bottom.

Thinking of putting a kevlar patch on the inside, and then just smoothing off the outside and using some Epoxy.



Epoxy Putty
I’d fill the gash with epoxy putty. The stuff I use I buy at my local hardware store. It is a two-part. You get two containers that look like 35mm film canisters. One has black paste; the other white. Mix equal parts to get grey.

Fill the gash and smooth the best you can. You can glass/kevlar over it if you like. I just paint it. It won’t be a seemless match, but it will be ok and functionally it’s great.

“If you like” ?!?
Not putting cloth in an exterior gash repair means a much weaker repair than is achieved with glass.

Mix up, say, four ounces of any epoxy you choose, and spread it evenly over a circular area on a piece of waxed paper. Let it harden.

Now mix maybe two ounces of West epoxy and pour it out over a piece of glass and a piece of Kevlar. You want to end up with about the same weight of patch for resin only and for the cloth patch.

When both have hardened for 24 hours, peel the epoxy only patch loose and bend it with your hands. Note how little effort it takes to get it to crack.

Now pick up and bend the cloth patch. Those cloth layers will make a big difference, both in the stiffness and in the amount of force needed to split the laminate.

I have seen composite laminates that would crease but still not split. You won’t get that result with any epoxy used without cloth.

JackL, I would still put at least
a couple of layers of glass over the outside hole. If you dish out around the hole, the glass layers will lay very low, and you will be able to sand them virtually flush.

repair in foam cored hulls
The best repair is pretty time consuming.

Open up a larger area in the foam cover, the inside fabric covering the foam, directly over the exterior gash. Hog out the foam with a scraper, then sand down to the bare, broken, outer hull.

Debread the gash, sand, acetone, then duct tape HD plastic over the oputside to hold hull shape. Then cover the inner with three progressively larger patches. In a perfect world, match original resin and material to maintain similar flex. If using kevlar, peel ply the edges down. [The reason folks suggest glass patches is that the edges are sandable.] Remove the peel ply when the patch has set up.

Then replace the foam with a new, sanded to fit piece bedded in microspheres, replace the foam cover layers and, sanding wide, cleaning w/ acetone using peel ply, throw a larger patch over the replaced cover. Remove the peel ply when the last patch has set up.

You’re not done. Roll the hull over and sand. If the hull has a hole - fill it with a cut to shape patch; if just a gash, sand and dribble resin, or resin and microspheres to smoothness.

Then reapply gel coat; sand flat w/ 80/120 dry, 320, 600,100, 1200 wet, buff and forget about it, trying to miss stobs in future.

It is important to match resins. Epoxy works on everything but few VEs and Polys stick to epoxy. In the past Wenonah used a CoRes VE. Best to get a quart from them.

The above is, of course, the downside of a foam cored boat.

My mistake …
I didn’t read closely enough. I saw foam core and was thinking it was a royalex repair, so never mind. Since it is kevlar (or any composite hull) I wouldn’t use the putty.