tinny transom, plywood or solid oak plank?

dkonrai · Sep 6, 2012

as some of you know i have a 1982 valco. the transom is rotted out, and my question is:

5/8 plywood vs 5/8 plank oak? i have some vintage, 1 x 12 oak shelving, really nice clear grain. my thoughts are that the plank is stronger than using plywood? i am in the trades and we always use boards vs plywood for added stregnth.thoughts?
yes i will bond the two pieces, and use some spar varnish all around the exposed wood. plan is the fit the wood, then drill the holes and take it out and spar varnish the whole thing.

Lyle29464 · Sep 6, 2012

Re: tinny transom, plywood or solid oak plank?

The oak will look great. If you were dealing with a larger boat and a bunch of HP I would go with the plywood.

Woodonglass · Sep 6, 2012

Re: tinny transom, plywood or solid oak plank?

2 things. Forum rules ask that you keep your posts concerning your project all in one thread.
2nd the Oak is not really a good Marine wood unless it is White Oak, and is susceptible to rot. Not saying it won't last but the plywood if it's exterior grade, will actually stand up better in a Marine environment.

kfa4303 · Sep 6, 2012

Re: tinny transom, plywood or solid oak plank?

+1. Exterior grade plywood is stronger, cheaper and easier to get too. Make sure it's non-pressure treated, or it will eat through the hull. You'll also need to seal it with either 2-part epoxy, fiberglass mat & wax-free polyester resin, or spar urethane. Be sure to mount it to the hull using stainless steel hardware, preferably dipped in 3M 5200 marine caulk.

dkonrai · Sep 6, 2012

Re: tinny transom, plywood or solid oak plank?

most interesting, plywood is stronger??? wow would have thought otherwise.

yes the oak is white oak. i got a great deal on the oak, way less than a sheet of ply. so now what? should i just scrap the oak and buy a sheet of 5/8 exterior ply?

thanks

kfa4303 · Sep 6, 2012

Re: tinny transom, plywood or solid oak plank?

Nah, probably no need to scrap it. The oak should be fine, but plywood is actually stronger. Most folks actually use two layers of 3/4" plywood laminated together to form a transom. Either way, just seal it well and it should last for many moons. Epoxy is great, but a little pricey and you usually have to order it. Same with the f'glass supplies, but several coats (3-4) par urethane works quite well, and you should be able to get it at any big box store. A quart should be more than enough. It makes the wood look pretty good too. Good luck. Keep us posted. We love pics.

64osby · Sep 7, 2012

Re: tinny transom, plywood or solid oak plank?

The plywood is able to flex a little better then a plank. It won't split. This is why it is preferred especially on boats with larger motors.

That being said, I used a 2x10 douglas fir board sealed w/ 4 coats of spar urethane, on my little tinny, 18hp max. Plywood would be used for a larger motor.

babbot · Sep 7, 2012

Re: tinny transom, plywood or solid oak plank?

Plywood is extremly strong in certain applications because of the alternating grains. A board may be stronger for a shelf but for a transom it may split down the middle of the grain.

aspeck · Sep 7, 2012

Re: tinny transom, plywood or solid oak plank?

Woodonglass said:
2 things. Forum rules ask that you keep your posts concerning your project all in one thread.

Really???? I have not read that anywhere. Multiple posts on the same question are not allowed, but a specific question may get more responses as a stand alone thread than imbeded in a general resto post.

To the OP, I think you have your answer. On a smaller horsepower application, the white oak should be fine if finished properly, maybe not as strong and not as much flex as the marine grade plywood, but fine for your application. And it should look REALLY SWEET!

dkonrai · Sep 7, 2012

Re: tinny transom, plywood or solid oak plank?

wow good stuff here. thanks so much. as for the transom i guess i will be giving the oak back to my buddy, and go ahead with the plywood. i may use some micro lam plywood, it has twice the layers of standard ply. i dont really trust the exterior 5/8 due to the fact it is only four layers. if laminated this would produce 8 layers. if i go with some micro lam, it will have twice the layers so stronger????
i plan in hanging a 20hp motor off the back. i currently have a 15hp there isnt anything wrong with more power

dino

kfa4303 · Sep 7, 2012

Re: tinny transom, plywood or solid oak plank?

You're probably ok going up to a 20 hp. I have a '66 OMC 20 hp on my 14' semi-V hull tinny. The bigger issue is the weight. 2-stroke motors are generally much lighter than their 4-stroke cousins. While you will probably be ok with a 2-stroke 20 hp (mine only weighs about 80 lbs.), a new 4-stroke 20 hp will weight quite a bit more and may be too much for the boat. There may be a capacity plate riveted to the hull that can give you an idea of the max load and hp. It's usually on, or near the transom, but boats built before the mid 70's, or so weren't require to have one, so don't be surprised if you can't find it.

dkonrai · Sep 7, 2012

Re: tinny transom, plywood or solid oak plank?

ok i cant afford a 4 stroke, and i like the smell of two strokes

the tinny is a 1982, but the tag for the boat is long gone just like the transom!

transom

a little rot

got the old wood out

old benches

some stress cracked rivets

dkonrai · Sep 7, 2012

Re: tinny transom, plywood or solid oak plank?

more stress cracks

rear bench

middle bench

had to stop bc of these guys

good thing is i got the 74 johnson running. need to change the impeller and rebuild the fuel pump. its slow going when you work, have kids, making the wifey happy.

as for the transom support i plan on fabricating another one out of 1/4" aluminum plate that i scored.

dino

64osby · Sep 8, 2012

Re: tinny transom, plywood or solid oak plank?

dk - man that is one rough little tinny. I thought mine was beat.

What is the action plan on the stress cracks?

dkonrai · Sep 8, 2012

Re: tinny transom, plywood or solid oak plank?

64osby said:
dk - man that is one rough little tinny. I thought mine was beat.

What is the action plan on the stress cracks?

option 1: see if my buddy can weld up the cracks. as well as the transom.
option 2: marine epoxy, with a small coin sized patch.
option 3: scrap is worth 1.00 a pound....

i plan on using gluvit on all the rivets and epoxy patches.

fishrdan · Sep 8, 2012

Re: tinny transom, plywood or solid oak plank?

dkonrai said:
i dont really trust the exterior 5/8 due to the fact it is only four layers.

Why only 5/8 ply, is that what the boat was built with originally? Usually they use 3/4 plywood, or laminated plywood for a thicker transom.

dkonrai · Sep 9, 2012

Re: tinny transom, plywood or solid oak plank?

fishrdan said:
Why only 5/8 ply, is that what the boat was built with originally? Usually they use 3/4 plywood, or laminated plywood for a thicker transom.

the original ply measures 5/8. 3/4 stock will be too thick and i will need to pry the transom lip to fit.

dkonrai · Sep 9, 2012

Re: tinny transom, plywood or solid oak plank?

64osby said:
dk - man that is one rough little tinny. I thought mine was beat.

What is the action plan on the stress cracks?

i only paid 400 for the boat motor and trailer.

64osby · Sep 9, 2012

Re: tinny transom, plywood or solid oak plank?

I saw on an older tinny where the owner welded cracks and the heat weakened the surrounding material. New stress cracks formed with in year.

Your option 2 maybe a better option. Drill the ends of the cracks and then rivet a plate over it with liberal amounts of 5200 between it. There was a thread here where a tinny had about 10 gashes and cracks. The guy did a great job patching them. It wasn't really pretty but very effective.

dkonrai · Sep 9, 2012

Re: tinny transom, plywood or solid oak plank?

ok, option 2! it is. it seems there is some options on sealing, marine two part epoxy putty. gluvit.aluminum gutter seal or 5200. i may go with the epoxy putty route and see if this stops the leaks.

should i install the new wood and follow the old transom as a template? or is it ok to beef up and run full width and length with the new wood, i.e. basically fill up the transom with two sheets of ply? i figured it would be really stronger with more wood due to spanning the load and flex over a wider area.

i guess i will leave the transom failed edge, and just install "L" channel or "C" channel over the the old break.

tinny transom, plywood or solid oak plank?

Senior Chief Petty Officer

Lieutenant

Supreme Mariner

Banned

Senior Chief Petty Officer

Banned

Admiral

Petty Officer 2nd Class

Moderator

Senior Chief Petty Officer

Banned

Senior Chief Petty Officer

Senior Chief Petty Officer

Admiral

Senior Chief Petty Officer

Admiral

Senior Chief Petty Officer

Senior Chief Petty Officer

Admiral

Senior Chief Petty Officer