New transom in fiberglass boat

Hey Guys,

I began rebuilding this 15' tri hull a while back. As of right now the transom and 18" around the area is all ground out. Here's my problem, due to cracks I found, and some crappy repairs from the previous owner I have low spots from grinding in the outer skin and in the lower corner along the bottom of the transom. Examples, the splash well drain hole I have ground out and will be filling in, and very bottom of the boat under the drain plug where it looks like he dropped it on the boat ramp and did a horrid repair. I have ground these spots half way through from the inside and plan on filling them in 1 1/2 oz mat-18 oz woven-mat-woven ect until filled in. Followed by covering with mat-woven-mat over the entire outer skin (tabbed in also) then two layers of marine grade, then mat-woven-mat-woven-mat as the inner skin. Not: all of these layers will be done in one piece meanin it's own skin and tabbing. The plywood will be bonded together and then to the outer skin with the super duty pl adhesive as well as the fillet.

I have west system epoxy sitting here that I plan on doing this with because everyone online says something different about which resin to use. I already had this sitting around from another boat and its a whole gallon.

The rest of the grinding and filling of the repairs will be done from the outside when the boat is done and can be flipped over for the remainder of the repairs and hull paint.

The boat is rated for a 85hp motor and came with a very nice johnson 90 which I'm sure is bigger in size and weight compared to most 85's so this needs to be over kill and I do have the room for all of this glass (overall transom thickness)

Can anyone tell me if my plan will work or if I'm going the wrong way? I have everything here and ready to get started!

Also, do I have to do all the layers at once while they are wet? Or can I do a mat-woven-mat and do another layer of woven-mat another day?

Any advice would be appreciated. I wish I could upload a picture, but IPhones suck! Thanks guys

Re: New transom in fiberglass boat

For those low spots you're repairing you don't just want to fill them, but the new glass should overlap onto existing good glass, around 1 " per layer. Search the West Systems website, I think they have a pretty good explanation.

I think overall your plan sounds ok, except that with epoxy you don't need the mat. Something like DB170 biaxial cloth would be plenty good. That mat will suck up a lot of resin that could have been better used elsewhere and it doesn't really add any strength.

Also, as far as letting one layer cure and then adding to it, it's better to do it all at once. If you absolutely can't do all the layers at once your best bet is to cover the first layup with peel ply, let cure, and remove the peel ply just before doing the next layup (it "micro-fractures" the surface when you remove it which makes for good adhesion for the next layer). At a minimum you have to thoroughly sand the cured layer and then thoroughly clean it before proceeding.

Oh, as far as putting a 90 on a boat rated for 85, don't tell anyone I said this but personally I wouldn't be concerned about that. They're pretty much the same engine.

Re: New transom in fiberglass boat

Thanks for the response. I know its been a while, ive been having huge computer probs. Im going to try starting a new thread with pics!

Re: New transom in fiberglass boat

No need to start a new thread this one's just fine.