Cracking transom

[scottrbishop]

Hello all, I have a problem with an epoxy repair I made to a '73 Glastron GT-150. I split the hull to replace the transom, and now have the two halves back together. The transom is secured into the bottom half, and I have patched the gap between the transom and the top half with a thick (4-5 coats) of epoxy, but the epoxy continues to crack where it joins with the top half. The transom is not separating from the bottom half, it's the top half breaking away from the transom/bottom half. How would you go about rejoining the two halves without it cracking, is there a better technique than pure epoxy? Cloth with epoxy coated over it? I think its cracking because the tow rope is attached to the top half and the jerkiness is too much for the repair. Any help would be very much appreciated, thanks in advance!

-Scott

 

[ondarvr]

Re: Cracking transom

While epoxy has more strength than polyester resin, it still isn't strong enough to hold up to what you're doing with it. Glass is what adds strength to both types of resin, without it the strength drops dramatically.

 

[scottrbishop]

Re: Cracking transom

Thanks for the advice! I thought perhaps I might need to add something to the mix. I've been using West System epoxy and have tried both 403 and 407 fillers (403 is microfibres and 407 is low density filler). Might sound stupid.. but what is "glass"? Another type of fiberglass filler? If there's a certain type you could point me towards, I'd really appreciate it. Thanks again for the response!

 

[Woodnaut]

Re: Cracking transom

"Glass" is just short for "fiberglass cloth". The fibers in the cloth have very high tensile strength. A piece of cloth has thousands of fibers in it typically running at right angles to each other. The addition of unthickened epoxy resin penetrates and totally saturates the cloth. After the resin sets up, the fiberglass cloth is extremely strong and relatively lightweight. You want to use some fiberglass cloth to build a connection from the hull to the transom. Try a search and you'll probably find some techniques listed along with some pictures.

 

[scottrbishop]

Re: Cracking transom

What type of glass tape should I use for maximum strength? Is Bi-Axial as tough as I'll need? I'm thinking I should lay tape connecting the wood of the transom to the splashwell of the top of the hull all around. Adhere the tape to the wood and splashwell using straight epoxy. Then I could fill in any gaps with another layer of epoxy mixed with 404 (High Density Filler) for "High cyclic loads where maximum strength is necessary".

Does this sound like a good route to go? I would love for this to be my last repair on this boat for the summer.