C-Forum

so there is a fresh looking hairline crack in the side of my new (to me) Zealots' hull, about 3 inches behind the wing, and it goes for about 8-11 inches, (boats not here, and so its hard to give a good estimate). so my plan of attack was to just lay up some new epoxy and glass, i have done some glass work before, so i dont feel to uncomfortable doing it, but i would love some tips from all you more experienced glass workers out there.

by the way its really fast
cheers
-isaac

The first thing to determine is whether the damage is confined to the outside skin, inside layers, or is all the way through. If the damage is severe, I like to do as much of the repair from the inside as possible. I will grind out the fractured section, tapering out about 2" from the centerline. It's a really messy and unpleasant job, especially when you've got to stick your head inside the boat.

Once ground out, use a layer or two of glass next to the surface and finish up with 3 or 4 layers of Kevlar. Cover the wet layup with plastic film to keep it smooth.

Someone once told me to use ducktape until you decide to fix the crack. If you are going to glassing, then get the respirator, gloves, etc and work in a well ventilated area. Use the type of resin that does not set up quickly, 2-4 minutes.

TO be honest, if this is an older boat and you do care if its pretty, just put some glass cloth over the area and use only Saran Wrap to get a slick finsihed product.

Chuck

Bob P is suggesting a lot of layers for what may be only an exterior break in the S-glass. If you can get more S-glass for the repair (from John Sweet), that's good. A surface break might need only 3 layers, of which the first laid down is the largest, the next concentrically smaller, and so on.

My Zealot has never cracked. I can't clearly visualize where yours cracked, but it sounds like something may have squuz (sic) the deck and hull on that side, so that the laminate bulged outward and the S-glass split. S-glass does much better when pushed inward, in compression, but it is also strong in tension up to a point. The inner layers of most Zealots are Kevlar (mine is carbon inside), and that Kevlar is unlikely to tear, though it may "crimp" a bit in the kind of stress I think caused your break.

If the Kevlar is markedly crimped inside, perhaps a single added layer of Kevlar inside would be worthwhile. I would not try to dish out the Kevlar inside unless it is split. Just roughen, clean, add one or two layers, put food wrap over it, and lay something heavy over that to compress the Kevlar against the original hull.

Other composite boaters please note: When you contemplate a repair, consider how the hull was distorted when the break occurred. A typical Hahn stern split would be right down the center, caused by compression. Using S-glass outside for such a split is good. Kevlar would have less stiffness, less compression strength, and will fuzz.

My Millbrook Wide Ride has lateral splits near the tail, below the seams. These splits must have occurred when the stern was compressed so hard in the center that the sides were put in tension and the S-glass split at the chines. These splits were only through the S-glass. I will probably fix them with Kevlar because Kevlar will resist re-splitting better than S-glass.

My old glass Hahn center-split often at the stern and at that time I did not have Kevlar to reinforce the patch. The boat did not have walls (!) and so I put a piece of ethafoam on a broomstick and cemented 80 grit sandpaper to it so I could reach in and sand the broken area smooth. Then I laid out three concentric layers of Nylon on a sheet of wax paper, basting them the long way and crossways with thread so they would stay together. I then mixed up epoxy, wet the concentric patch, got the broomstick under it, reached in and dumped it over the split. After that the Hahn would crack but not through the Nylon, so it would not leak, and I could get by with exterior glass patches.

With a racing boat, I believe fewer layers are often better, because you want the patched area to be only a little stiffer than the rest of the laminate. And no point adding a bunch of weight. Also you should be conservative about dishing out or feathering a split. Often it is enough to just get the edges of the break smooth and dished down through the outer layer.