repairing damaged section of hull

[old man]

I posted this on the fiberglass board but did not get any responses and figured I would post it here also.

I just bought a powerboat that has some damage on the bottom. I was told the boat broke loose from a dock and bounced up and down near the shore on rocky bottom. Not sure if this was the case or they hit someting underway. Either way I have the boat and I am trying to fix it.

Attached is a picture of the damaged section. The boat has a keel (skeg) with a srtaight inboard. The damage starts where the skeg (keel) begins and goes back about 4'. No other part of the bottom has any damage, just on the skeg. Below is procedures how i was going to fix it please let me know if you have any suggestions on how i plan to fix it. I have done glass work on old wood work boats but that is it (new decks, building cabins). Any advice is greatly appreciated.

1. Remove botom paint about 10" past each side of the damaged areas. Sand the gelcoat off to get to raw fiberglass material. Do I have to sand the gelcoat off to get new fiberglass to adhere correctly or will it adhere to gelcoat?

2. I am going to use US composite 635 med epoxy (I have some left over from another job). I was going to wet out the area, then use thickened epoxy (consistency of peanut butter) to fill in all the damaged areas. What is the best filler to use (west system brand is what I have acess to)? is epoxy Ok that is all I have ever worked with, never used poly even though the boat is polyester.

3. Sand area to re-shape damaged sections back to normal.

4. Lay 7 oz cloth over damaged area with 3 coats of epoxy over the cloth. The last coat of epoxy I was going to add west system 410 filler to help the ease of sanding.

5. Re gelcoat damaged areas. Do I have to re-gelcoat it since bottom paint is going over top of it? I figured if i ever sold the boat and they wanted to strip off the bottom paint it might look funny if this was no re-gelcoated.

[pungolee]

From what I could tell from your picture you need some new wood in that hole.Epoxy thickened with Cabosil( fumed colloidal silica) works wonders but has no inherent strength, and 7 oz cloth wont add much.
First, I would clean the gouge well and flow unthickened epoxy into all joints/cracks.Then,,while the first coat is still tacky(2hours)install a custom cut pc. of mahogany or white oak and epoxy it into the slit,being generous with the epoxy thickened just enough with colloidal silica to keep it from running.
You may need to install stainless screws into the pattern/patch to hold it straight while gluing.Any glue squeezing out should be filleted or smoothed/removed before hardening.
After 3 days when the patch is good and hard it needs to be worked down flush to the shape of the boats hull.Hand plane would be best, one you dont mind getting gummed up, with a sharp blade. Sanding would be the last thing I would attempt, but a respirator and a good belt sander can do it.
After that mess is pretty smooth following the original lines then install one coat unthickened epoxy,then another,cloth,finish coat of epoxy,then Interlux Interprime, then bottom paint.
Fun, huh? Thats just how I would do it, anyway.
Oh, by the way, after you are finished you may want to install a worm board.

[gonzo]

Is the keel solid? Either way you need to build up the laminate to the original condition. There is no problem with using polyester for the repair. It is what the original laminate is made of. You can fill the core with almost about anything. Bondo can do the job. If you are going to use epoxy, don't use mat. It has a binder that epoxy doesn't adhere well to.