Increasing Transom Thickness

[woodman7975]

The spec for my transom thickness calls for between 2-2-1/4”. I currently have two layers of 3/4” ply, peanut butter between transom and exterior skin, and two layers of 1708. Right now I am at 1-13/16. I would like to be at 2-1/8”, so according to my calcs I would need 7 more layers of 1708 at the key hole. Would that be too much? If so, is there a better way to go about increasing thickness without pulling off the old glass and adding more plywood?

 

[Woodonglass]

You should have sandwiched a 1/2" piece of plywood between the 2 layers of 3/4. Inch. More layers of glass is Not a good solution.You might consider laminating a 3/8" piece on it and then glassing it with 2-3 layers of 1708

 

[woodman7975]

Would I need to remove the glass that I have on it now, or could I peanut butter the plywood over the glass that I have on it now and then glass over the top?

 

[woodman7975]

Also, just for my knowledge what would be the issue with adding more glass?

 

[Woodonglass]

The biggest issue is cost. 3/8" plywood is a lot cheaper than all that resin and glass. All you need is some PB to glue the wood to the existing transom and then Glass over it. It won't be as strong as it would have been in the start, but it will be more than strong enuf for the transom.

 

[woodman7975]

Just so I’m clear, I can PB the plywood directly to the current transom that has fiberglass on it and there won’t be issues with it sticking? Thanks for your help. Should have checked before I got this far.

 

[zool]

3/8 ply plus the glue may put you over the edge a bit....if its an I/O, you can just increase the thickness about 6" around the keyhole on the inside, keeping it parallel, till you get the your desired result....the 2-2 1/4 range is more for the transom shield than for strength.

You can maybe glue 1/4 ply by just scuffing up the glass you put on already, and clamping the new ply layer over....but i dont think you will need it.

 

[woodman7975]

That was kind of my plan. It is a 1988 Sea Ray Seville, so it has a transom with a thickened center section and smaller “wings” that go from side to side. It is a smaller version of the transom that Frisco Boater had in his Sea Ray videos. If I used plywood or glass I planned to make kind of a thickened “horse collar” just in this thickened section of the transom. Any idea on which route would be stronger/better?

 

[zool]

Any idea on which route would be stronger/better?

An 88 sea ray most likely has a Merc/Alpha setup, so with 2 pieces of 3/4 ply and fresh resin/glass, you are already past the point of diminishing returns.....so more is just overkill as far as transom strength,

 

[Mad Props]

I would get a piece of luan ply, it's about 1/8" andit's made with exterior rated glue and tropical hardwoods (basically thin marine ply).. pb it on and do a layer or two of 1708...

When you glue it on tho, you might want to use a thicker piece of plywood or something as a clamping caul to make sure it's flat cuz it's so thin it could get bumps and lumps from the pb under it..

 

[woodman7975]

It is a merc/alpha setup, that’s why I just went ahead with the 2-sheets of 3/4”, PB and two layers of 1708 It seems everyone else that I read about on this forum and others have had no issue getting to 2” with that setup. I did drill the holes in the transom, per the suggestion in the sticky, to create kind of a rivet with the wood and PB and to allow spots for the PB to ooze out. It did give me an almost perfectly flat surface around the keyhole with no air pockets, but maybe it pulled the transom in a little tighter than others. Either way I have a plan now.
Thanks for all the help. My friend once told me if you ever lose faith in humanities ability to help one another go on a DIY forum and you faith will be restored.