Transom fiberglass help needed

[jeremy5780]

So I did a thing a couple months back, I poured my transom with ARJAY. I used a ladder to stop the transom from bowing, but that didn't work and I got one HELL of a hump in the transom! So after letting it sit several months due to my frustration with it I decided to Grind the hell out of it and level it back out. Several hours later and several sanding discs and MANY MANY itchy nights later I got it leveled out! So I attached a picture of the transom, the grey in the middle is bare ARJAY with solid glass about 8-10 inches around the sides. My question is how many layers of glass do you recommend me putting on the back of the transom? I was going to go 1st layer CSM followed by 2-3 layers of 1708 Biaxial using poly laminating resin. Your thoughts are always helpful and welcomed.... Thanks

[RickK]

Question: How much ARJAY do you think you ground off? Is the transom still strong/thick enough to support whatever you are going to hang on the aft? Usually you have at least 1.5 inches of core plus glass inside and out.

[mshugg]

3 layers of 1708 is probably the minimum that I’d want to go with as a transom skin.  That would be just under 3/16” thick.  The CSM would probably be better as the outer skin.  The 1708 already has a layer of mat stitched to it to produce a good bond between layers.  So, your layup would be 1 layer 1708 mat side toward transom.  Wash rinse and repeat X2. Then, finish with a layer of CSM.  The CSM provides a finishing layer, so when you prep and fair, you won’t be grinding into your structural 1708.

[jeremy5780]

Thanks, transom is solid and every bit of 1.5 inches thick! Most of the grinding was in the middle where it bowed out. I would say 1/2 inch maybe.

[jeremy5780]

Ok I put 3 layers of 1708 stitched biaxial on the transom today with polyester layup resin. I let it cure for a couple hours then put a coat of gel coat on it so it could fully cure. I was going to give it a solid 24 hours then sand it and either put another layer or two of glass, or just fair it and prime it? What's everyone's thoughts?

[RickK]

Ok, so you didn't grind much away - good.
The transom outer skin is a part of the entire hull. When you recore a transom (from the inside) you usually add a couple of layers of cloth to the inside of the transom (overlapping on the sides and bottom of hull) to beef up the outer skin which usually gets a little thin from the grinding to prep. Then you add/clamp coring in and then add 3 more layers of cloth to the inside. Now you have a solid transom that is a part of the hull and will take the pressure of the engine pressing forward against the transom/hull as the boat is pushed through the water.
Your transom skin was compromised when you ground through it. When you laminated the layers of 1708 did you lay the cloth around to the hull sides and bottom to tie the transom into the hull? If you only laid the cloth across the aft of the transom to cover the Arjay, there is not any improvement in structural support. You might be ok but what are you going to hang on the transom? (I am not trying to be negative here)

[jeremy5780]

Ok so to clarify when I cut open the back of my transom and ripped the old wood out I left approximately 4-6 inches of the original transom around the edges and bottom to tab back into. I cleaned the old wood out and took the inside down to bare glass, then I added a layer of CSM to the inside. Old outer skin was reattached, and the back of the transom was braced for the Arjay pour (not well enough) the outer skin bowed in the middle so I had to grind it down to level it out (mostly the middle not so much on the sides) So as you can see in the picture I still have a good 4-6 inches of solid original fiberglass from the original transom around the sides and bottom. So when I laid the 3 layers of 1708 stitched biaxial yesterday I covered the entire back of the boat I did NOT wrap it around the side's or under the bottom. My plan is to hang a flotation bracket with a swim platform on the transom and hang the old 225 Johnson. Hope this helps

[Tampa Bay Mike]

I'm no pro but I would venture to say that the arjay in the center will be stronger than a few layers of the original glass would have been. So with the three extra layers the outside should be ok there. I'm more worried about the inside. You may want to think about adding more than just a layer of CSM there and possibly extend it to the bottom and sides.