View Full Version : Combining Transom Wood
07-26-2001, 09:48 AM
I was wondering if it would be alright for me to laminate a 3/4" sheet of doug fir ply to 3/4" mahoganey ply for my transom on my skiff. Are there problems associated with combining wood like this? The reason I ask is that I would like to be able to save a little cash without jeopardizing the aesthetics of the boat on the outside.
07-26-2001, 10:31 AM
Chris,no problem as far as i can see.Both are plys,so no stability probs.
One possible prob.will be with the fir.If it is not marine grade,it will have a fair amount of voids.Any fasteners that tap a void will be a potential source for rot.
07-26-2001, 10:52 AM
Several years ago in WB Magazine, there was a story about the transom replacement, using plywood, of a larger boat. The boat belonged to Jon Wilson, WB's CEO. There was some criticism of using plywood instead of the normal planking, as I recall.
So, you're gonna stick this stuff to the outside of your existing mahogany transom? Why would that be? If you've already got some punk and funk going on there you will just succeed in building a sh*t sandwich. Remember, plywood sucks, especially the end grain. The fir plywood is going to be rotary cut unless you order vertical grain/plain sliced (not likely). With rotary cut you get to look forward to trying to keep paint on it, good luck. Rotary cut gives you a veneer made up of winter wood and summer wood, I believe it's the winter wood that doesn't like to stay painted. Hell, maybe it's the other way around, anyway, maybe you should just repair your existing transom.
07-26-2001, 08:33 PM
I assume this is a boat you are building. I'd say on a skiff the aesthetics inside are just as important as those outside. For the work you'll be putting in, treat yourself to proper marine ply for the whole thing. Or better yet, use 1 thickness of ply, and internally frame it with real wood. You'll save some weight and not lose any strength. Better holding for plank screws too. 3/4 ply transom on a skiff sounds overbuilt to me.
07-26-2001, 09:02 PM
Originally posted by RGM:
The fir plywood is going to be rotary cut unless you order vertical grain/plain sliced (not likely). With rotary cut you get to look forward to trying to keep paint on it, good luck. Rotary cut gives you a veneer made up of winter wood and summer wood, I believe it's the winter wood that doesn't like to stay painted. Hell, maybe it's the other way around, anyway, maybe you should just repair your existing transom.
The problem with rotary cut veneer is that one side of the veneeer is in tension and the other side is in compression.
Rotary-cut veneer is produced by chucking the log into a [very big] lathe. The log is spun on the lathe and a large blade peels one continuous sheet of veneer off the log.
Naturally, this veneer is somewhat attached to the configuration the fibers had when it was part of a tree. Creature of habit as it were. When the veneer is flattened, the convex surface of the veneer is put in compression, since it must become narrower and the concave surface of the veneer is put in tension, since it must streeeeetch a bit.
The resulting tension induced lies across the grain and results in tiny tears or splits along the grain.
Imagine, if you would, a 2x12 with a LOT of cup in it. Put it in, say, some sort of big hydraulic press and apply pressure to the board until it is pressed flat. You get the idea -- think of the veneer as a board 1/32 of an inch thick.
07-27-2001, 10:09 AM
I am building a 15 foot v-hull skiff designed for rougher waters and the plans call for two 3/4 transom pieces to be laminated together for a total of 1 1/2". The inner transom will hold the apron and battens while the outer will cover them up. Last night I went ahead and purchased the 3/4 marine doug fir for the inner. I will have to start saving my pennies for my outer mahoganey transom which is about twice the cost at $140.
07-27-2001, 11:26 AM
Go for it Chris.
Hows about periodic updates and pictures as you bring her into the world?
07-27-2001, 11:47 AM
What you suggest doing will work fine technically though I wonder why not just buy the mahogany and cut both inner and outer pieces from that? Unless you anticipate using the cutoff for some other project, or the layout doesn't fit. But then, you can never have enough nice stock laying about!.
One other thought. If you are near a boat shop you might be able to buy a suitably sized piece from them for less than the cost of an entire sheet.
Best of luck,
[This message has been edited by ishmael (edited 07-27-2001).]
07-27-2001, 12:47 PM
Wow! Two pieces of different 3/4" plywood laminated together. You better hope both are dead flat or it's going to take the weight of a herd of elephants to flatten them enough to get a good bond.
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