transom material

[sr71]

I have been reading the tinboats forum for quite awhile now and I have learned alot. I was given an old trailer, a old 14' Starcraft aluminum and a old (1974) Evenrude 9.9 hp. I am a rookie at all this, but hopefully it will be a fun project to get all of these back in shape again. Plan on using the boat at the Jersey shore for crabbing and fishing next summer. Anyway, I have completely fixed up the old trailer as per all the info I learned from "tinboats". I just put the boat back on the trailer so I can work on it now. I just took out all the old rotted wood from the transom. The wood I took out was not glued together, but had some thin aluminum sheets between them. I would think that I should glue the two new pieces of ply together which should be stronger than unglued with the thin aluminum sheets. Also, I was wondering if anyone has used Starboard instead of wood for their transom. Is the weight of Starboard a factor? Any thoughts on this would be appreciated.

 

[Go Fish]

Starboard is absolutely NOT an appropriate material for transom reinforcement. It lacks the rigidity that you need to offset the forces being applied by the motor.

Stick with a couple layers of good quality exterior grade plywood and "glue" them together with thickened epoxy. I'm a big fan of encapsulating wood parts with epoxy to keep the water out but some folks swear by less expensive coatings like spar varnish.

 

[lckstckn2smknbrls]

Starboard is absolutely NOT an appropriate material for transom reinforcement. It lacks the rigidity that you need to offset the forces being applied by the motor.

Stick with a couple layers of good quality exterior grade plywood and "glue" them together with thickened epoxy. I'm a big fan of encapsulating wood parts with epoxy to keep the water out but some folks swear by less expensive coatings like spar varnish.

Exterior grade not treated.

 

[Ringo Steele]

I recently replaced the transom in my 16' Ouachita semi-vee and used t layers of 3/4" exterior plywood. I glued them together with TightBond III waterproof glue, drilled all holes slightly oversize, then covered in 3 coats of West Marine 105 epoxy, including through the holes. It turned out great, and should last longer than I will! :LOL2: It seems to be as solid as wood can be made without resin saturation throughout the wood. Installed it with all stainless hardware.

 

[PSG-1]

Starboard is absolutely NOT an appropriate material for transom reinforcement. It lacks the rigidity that you need to offset the forces being applied by the motor.

Uh, oh! LOL I had a customer a few years back that had a big piece of starboard he wanted placed in the transom of his boat after the wood had rotted out. So, we did. Never heard anything from him about any issues with it, but in the future, I'll definitely avoid the starboard.

 

[sr71]

Thanks for all the info. I got a 4' x 8' sheet of Arauco ply from Lowes today. It will be just enough for the transom and the 3 bench seats (as long as I measure twice and cut once!). Also got some Titebond III for bonding the pieces for the transom. I have never used epoxy on such large surfaces before, but I will do the transom first to "get the feel" on working with it before I do the seats. I have 2 questions about epoxy and wood.....Is West Marine 105 uv protected? Also, when I epoxy the bench seats should I just coat the top and edges to let the wood "breath" on the bottom side, or coat the whole bench seat?

 

[Go Fish]

...I have never used epoxy on such large surfaces before, but I will do the transom first to "get the feel" on working with it before I do the seats...

Epoxy working tip: When spreading epoxy on large flat surfaces pour a puddle of epoxy onto the surface and spread it around with a cheap window squeege (you can get 6" plastic squeegies at Lowes or Home Depot for about $2 a piece).

West Systems 105 does not have UV stabilizer and will yellow over time. It is also REALLY expensive. Give Larry at Raka Epoxy ( www.raka.com ) a call and tell him what you want to do. He can recommend a product from his line that will get it done better for less $$$.

Coat every surface and pay special attention to the edges. I use a disposable sponge brush to "dab" epoxy into the edges. The edges will soak up a lot of epoxy so keep after it until they won't take any more.

 

[Ringo Steele]

"West Systems 105 does not have UV stabilizer and will yellow over time." Should it be top coated with something, maybe spar urethane, to protect it?

"The edges will soak up a lot of epoxy so keep after it until they won't take any more." I can surely attest to that statement! :wink:

 

[Tinklespout]

I noticed that everyone is talking about exterior grade plywood. Would'nt marine grade plywood be better?

 

[Go Fish]

It is my understanding that there is no functional difference between "Marine Grade" ply and good quality exterior ply save that marine grade is confirmed to be void free via examination by X-ray. The materials are comparable, the glue is the same... One could argue that marine grade ply is better. But, in the context of fixing transoms on small boats, the substantial extra expense is really not justified.

Some insurance companies require that boats (typically big expensive ones) be built with certified marine grade ply in order to be covered. So, if you are looking into a Lloyds of London backed policy for your tin you will need to use marine grade ply. Otherwise, go to your local lumber yard and buy a nice sheet of high quality North American (not made in China) exterior ply.

 

[Ringo Steele]

I had a question on the UV properties of the West Systems epoxy and got this reply from them:

"Our WEST SYSTEM® 207 Special Clear Hardener has a small amount of UV inhibitor added – but not enough to be a final finish. The UV inhibitor depresses the physical properties and our products are first and foremost structural adhesives, so we do not make just a final coating. We always recommend using an over coating – a clear urethane, varnish, or paint. Here is a link about Finish Coatings,
https://www.westsystem.com/ss/finish-coatings/"