Wood for Boat Transom

[OptsyEagle]

I need to do a much needed repair to the wood transom on my Springbok 14' aluminum boat. Just the wood on the inside of the boat. I know they say not to use the green pressure treated wood because it is supposed to accelerate rusting of the boat.

I am wondering if Cedar would be OK or perhaps the new brown pressure treated wood might be fine. That marine grade stuff is a little too expensive for my 42 year old boat. You would think they are gold plating it or something from the price of the stuff. The biggest motor on this boat is a 15Hp.

Anyone have any thoughts on Cedar or brown PT wood.

 

[SeaFaring]

I would (and plan to) use ACX exterior plywood in my 14' Starcraft. It's the same glue as marine ply, but allows for more voids in the internal plies. This is mainly an issue when you start through bolting things, there's a chance of hitting a void. This risk probably exists with PT plywood as well, or any plywood cheaper than marine grade where the specification explicitly prohibits voids.

I can't comment with any authority on the particular alternatives that you mentioned, but my intuition is against both. For cedar, my rationale is that its use as a traditional boat building material tends to be for interiors and lightweight human powered craft, not for highly stressed components such as transoms. Transoms would traditionally be mahogany, teak, white oak, or similar. I do know that not all cedars are created equal though.

I don't know the first thing about "brown" PT plywood, sorry.


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[DaleH]

I'd have zero reservations about using a good quality piece of white cedar ... not red cedar. This particular wood species is nearly as strong as oak and has superior qualities of being naturally resistant to water, decay and bugs. I'd coat it with a good UV sealant, like Sun Frog.

FWIW we have a few benches made from white cedar out on our docks 24/7 every year from May through the end of OCT and we don't even seal them (due to the saltwater air) ... and they're still as strong as new for > 10-years use.

Not sure it would be cheaper than good plywood though ...

 

[CMOS]

I used 2 pieces of 3/4" regular plywood for mine. Cut to shape, used carpenters adhesive to secure the 2 pieces together, then completely covered the entire thing with 2 coats of Fiberglass resin. Makes the wood completely waterproof.

One other thing - I predrilled the mounting holes in the new transom, then sealed the holes with resin. Don't forget this step.



CMOS

 

[-CN-]

I work in the building material industry so I can relay to you what I know about plywood. The brown pressure treated woods that are on the market simply have a brown temporary finish over the top of the regular pressure treatment. They will often call this process KDAT - Kiln Dried After Treatment, and this allows them to finish the wood immediately rather than the usual curing period for treated wood before you can stain it or paint it. The sole purpose of the brown treated wood that's on the market is so that your project, such as the deck you just built onto your house, looks "done" once you have it built, and it doesn't sit there with the ugly off-green color to it while it's curing. The treatment of the wood is the same process, so do not use it on an aluminum boat.