Carbon Trailing Edge Repairs

I think most have gone away from the gybing boards by fairing in the daggerboard trunks.

You've pretty much got the repair down.

Don't worry about the gelcoat over epoxy - it's not really an issue in small patches like that. Just rough sand (150 grit) the epoxy patches before gelcoating so it can get a decent mechanical grip (same goes for the rest of the recoat). Some of that gelcoat over epoxy is blown out of proportion based on the fact that there will not be a chemical bond between gelcoat and epoxy (which is true)...but you're not going to get a chemical bond between cured 5 year old gelcoat and new gelcoat either.

Check the bottom of your trunks. Where the trailing edge touches the trunk that needs to be a nice smooth surface. Sometimes when the boats are new, whatever glue they use when they are putting everything together isn't properly removed. I didn't check this on a new Viper I had, and it mauled a set of boards in basically a day. I'm sure it's something that Dan would've taken care of, but easier things have been missed, or the board has worn a notch into the glass.

A small file is all you need to fix it. If the board has worn into the hull, just fill it in with epoxy, and file that to shape.

That's essentially what I'm doing. I did it with carbon laminate and that broke out quickly, simply not enough material. I'll probably add some milled fibers along with graphite and do a straight 2-part epoxy, either Resin Research or Pro-Set. The hobby grade epoxies aren't great and resin research is very inexpensive per quart (though it takes a week or 2 to ship usually).

My boards have gelcoat all the way to the TE, but I'm not going for looks more for hydrodynamics. Might suggest spraying a clear lacquer post repair, just to keep the epoxy from yellowing.

Any tips for fixing dinged tips? Looks like a lot of epoxy+milled fibers in that area and much more difficult to shape. It'd be easy if Nacra just sent me the molds...

When you just fill in a small gap on the edge, there is not enough contact area between the repair and the board. It is not as strong as the original so it is going to pop out or crush when it gets hit. If you want to do this I suggest Loctite(Hysol) or 3M premixed epoxy (http://www.scottsales.com/structural_adhesives.html, Look at the table or call the company to see which one is best) This is a lot easier than mixing it yourself. You can also try filled poly carbonate or urethane. They are more flexible and deform rather than pop out or crush.

The ugly truth is if you want a small repair like this to hold up, you have to use techniques you would use for a big hole in your hull. Grind a ~8 to 1 taper back from the damage (This area is so thin, you can probably only taper one side) Clean the area thoroughly with isopropyl alcohol. Apply a thin coat of epoxy directly to the repair. When that epoxy starts to kick, apply fabric or fibers with more epoxy to fill the damage and the taper(You want 70% fiber/30% epoxy by volume). Then use peel ply and plastic film and apply pressure (vacuum bag preferably or wood blocks and clamps). When it hardens, sand it smooth and apply a thin coat of epoxy to fill in any hole/gaps/etc. Finally the final sanding.

If you have room, bonding some very very thin nylon webbing to the back of the dagger board trunk with 3M 5200, helps a lot.

Totally agree on this point. Just did some 2nd-gen repairs with better tapering. Hope they hold up better.

Will check out the materials. Really appreciate the detailed procedure. Will also check on the room at the back of the trunk. Putting the boat together tonight for some sailing over the weekend!

Thank you for the details! Looking at that list we should be using Hysol 9433 me thinks, but that isn't very available, at least I have to go through a sales rep to get it.

I'll try a higher taper ratio using my

normal

methods, this time I'll stick the board in a vacuum bag.