Transom plywood

[iwombat]

I know this has been discussed a bazillion times, but here goes again.

I found some rot in the transom on my tinny ('77 Starcraft SS). I was hoping to make the transom replacement next winter's project, but I don't want to take the boat out in the chuck with the upper port corner of the transom rotted out (and who knows what else).

Anyway, I've been doing some reading. Seems like PT ply is the product of choice for transoms, I'd like to make this project a quick turn-around though and I'm a little concerned with how wet the PT comes. Any other alternatives that won't need to sit up for a few weeks drying out? I'll be using epoxy for the job.

I'm figuring this should take the better part of a day once I have the motors off and the old transom out.

 

[drewmitch44]

Re: Transom plywood

If you are trying to make it quick PT is def. not your choice. It has to dry for months so that any kind of resin will stick to it and even then who says it even will. I thinl that ply that has the most ply's as you can find will be better as long as its not PT. The idea is that you wrap the ply with glass and resin anyways so at the end of the day it really dosent matter if its regular ply or pt as it will all rot anyways if you dont do it right. Its just easier to use nice dry 7 or 8 ply 3/4 thick plywood. If you do that you got 16 plies of plywood when you put them together. Thats a nice rugged transom. Its up to you though. If you get PT ply you better let it dry a couple of months so that way you can do the basic things with it.

 

[fishie]

Re: Transom plywood

I have a tinny I replaced my transom in, used AC exterior ply. 2- 3/4" plys sandwiched with gorilla glue and screws. Then 4 layers of glass mat went on, i'll go out on a limb and say its as strong as a steel beam and waterproof to boot.

 

[iwombat]

Re: Transom plywood

Fishie - that's kind of the route I think I'm going to take.

I'll probably epoxy (with cabosil) the two pieces together and wrap with epoxy and cloth. Oversize the outboard mounting holes and epoxy them in too. The existing transom looks pretty solid except for the one corner so I'll have a nice template to work from anyway.

Well, that's the plan. I'll take the motors and the transom cap off tomorrow and see what's what. Serves me right for wanting to find out why the 4200 was splitting off the splashwell joint. I'll have to figure out why it rotted from the top corner too. That seems pretty odd.

 

[tashasdaddy]

Re: Transom plywood

this will work as well for laminating. http://www.stickwithpl.com/Products.aspx?ID=fef65cc9-47bf-4802-aaa9-a343f2ef9458
spread it on one side of the transom panels, with a notch trowel, apply second panel, screw or clamp together. then seal exterior. i've been using this for years. the wood comes apart before the bond.

 

[iwombat]

Re: Transom plywood

TD, I haven't seen that product near me. I've been using liquid nails for years though. Probably about the same thing, I'd guess.

 

[tashasdaddy]

Re: Transom plywood

lowes and HD, have it. where the liquid nails is. much better than liquid nails, water will turn loose liquid nails.

 

[iwombat]

Re: Transom plywood

I see LN has a polyurathane product now too.

Anyway I'll look for the one you recommend (nothing like a success story).

 

[Woodnaut]

Re: Transom plywood

I extended the length of my boat two years ago when I repowered. I used marine plywood (Okoume) and then capped the edges with Honduran mahogany. West System epoxy in between and all around, then glass on the outside. I think Okoume is a species of mahogany and good for marine applications, but it's also hideously expensive. Around here a 4' x 8' sheet of 3/4" is about $130. At least it was in 2006 - no telling how much it is by now.

 

[tashasdaddy]

Re: Transom plywood

great job. love the style.

 

[comalley@gloryroad.net]

Re: Transom plywood

Glad that I read this thread. I know nothing about boat restoration, and joined this site today to get some help. I bought some pt plywood today to replace some rotten deck in my boat, guess I'd better find something else. I don't feel like waiting a few months. If any one could help me with this..my first "problem": The foam ballast that was sprayed at the time of manufacture in the port and starboard sides is holding water(I recently recovered this boat it had been outside for the last 10 yrs). I have most of the foam exposed, will it dry out over time? or should i tear it out and replace? I thought about cutting grooves in it down to the hull to maybe promote evaporation and the refill it with "great stuff" or another spray foam? Any suggestions or redirection to other threads would be appreciated!! Thanks

 

[mcbroomsear]

Re: Transom plywood

If it's holding water it's gotta go. It will continue to evaporate and eventually lead to the mildewing and rotting of your stringers.

Once it's waterlogged, it won't provide the bouancy you need.

Just tear it out and look hard at your stringers and hull walls for any bad spots. Then re-fill with either 2lb or 4lb foam. www.uscomposites.com sells it in different quantities and its better and cheaper than greatstuff.

I'm in the exact same boat (pun intended) as you are. All of mine has gotta go as well and us composites seems to have the cheapest I've found.

As for the flooring, I don't know what the master re-storers around here will say, but I plan on using regular exterior grade CDX and cover it in Resin and mat several times to make sure it will keep the water out.

Again, check those stringer's my friend, the last owner of my new project re-floored it without replacing them and now... It's dust wet mulch...

 

[Coors]

Re: Transom plywood

That foam will never dry; search in here for old threads, and opinions.

 

[comalley@gloryroad.net]

Re: Transom plywood

hey thanks for your replies. I'm so new to all this I didn't even know what a stringer was. This is a 1980 model sea ray my dad bought new. I wouldn't be messin around with all this if not for the sentimental part of it. Tryin to do as much as I can myself. This is turning out to be more than I originally planned on. Will the stringers be in the foam or is there another compartment below the foam. Do the stringers run the whole length stern to bow? It is a 19' boat.

 

[iwombat]

Re: Transom plywood

Well I peeled everything apart. The entire port side is rotten up to about 3" from the side. The rest of the transom is rock solid. Looks like rain got in under the trim from the top of the gunwale and ran right down the side. I'll be paying attention to sealing that up for sure.

Anyway, the top aluminum trim is broken in a few places. I'm wondering both where I can buy some more. Or, what alternatives there are to replacing the aluminum top trim. It needs something to top off the wood-aluminum seam.

 

[Joe_the_boatman]

Re: Transom plywood

My aluminum trim's in bad shape too. I wish I could replace it with new. For now, it'll go on like it is and I'll seal the seams with 5200.

As for the transom, I used pressure treated after it dried for about 2 months. The "micronized" pressure treated I used for my deck seemed about as dry as the non-treated wood. It's a yellowish color, instead of the usual green. You might want to take a look at it.

 

[ezmobee]

Re: Transom plywood

My trim piece was pretty bad too. But since I had no source for a new one I cleaned it up real well with a wire wheel on a drill, glued it back on with 5200 and clamped it. Came out surprisingly nice.

 

[reelfishin]

Re: Transom plywood

I've done a few Starcraft transoms over the last year now, I've yet to do one in PT for the fear of corrosion from the treatment. I realize that not all PT wood is corrosive, but not being able to tell which is which for sure, I'd just as well avoid it.

I do most using 2 layers of 3/4" ply, the best exterior grade I can find, and I screw and glue them together using stainless screws and sandwich them with epoxy and a layer of fiberglass inbetween. I generally just use several coats of epoxy paint over the finished panel and install. My thinking is that most of these boats are 40+ years old and the transoms have survived this long being plain wood, so anything I do beyond that will outlast me or the boat in most cases. Many of those transoms weren't even painted, my 1962 16' Starcraft's transom was bare marine plywood, and appeared to be single layer 1 1/2" ply. It lasted 43 years and the only part I found rotted was directly around the port side rear tie down eye. A former owner had soaked it with Getrot and it probably could have been left be, but being that these are an easy job and I wanted to properly fill several dozen unused transom holes for good by welding, I chose to replace it the same time I did the floor.
The original wood came out intact and made the perfect template.

I did a small aluminum jon boat transom last week, I didn't have enough resin to laminate with handy and it was only an open jon boat. I ran down to the local hardware store and found something called Elmers Ultimate Polyurethane adhesive. After talking to another guy there that raved about how well it worked on his deck, I thought I'd try it. It foams when applied and is completely water proof. I did a test on a piece of 2x12 and some 3/8" ply that I was going to attach to a stand to store an motor I had removed the day before from junk boat. I was surprised at how well that stuff penetrated the wood and every seam. In about 15 minutes, the glue had foamed out of every possible seam and crack, even through a few open splits in the 2x grain. I had used some 2" stainless deck screws to attach the two on various angles and let it dry. In about 4 hours, what had foamed out the edges was dry and sandable but not brittle. I probably used far too much of the stuff the first time. It looked a lot like fiberglass resin when dry.
I bolted the test panel to a stand and imediately hung a V6 'Rude on it.

I did the same with two pieces of 3/4" ply on the jon boat, let it dry wiping over the edges well with the foaming glue while it dried. Once dry, I simply painted the sandwiched boards well with a good epoxy paint and installed it the next day.

I don't know if I'd use this on a larger boat transom or not, but I think it's a viable adhesive for boat use. It bonds to anything, even the drips on the floor won't come up and what dried on the putty knife had to be wire wheeled away. I used it to attach two small scraps together and tossed them into a bucket of water outside to see how it holds up to water. My bet is that the wood will soften and fail before the glue bond gives up.

http://www.elmers.com/products/product/product_page.asp?pCode=P9413

 

[iwombat]

Re: Transom plywood

This is an 18' SS, so not a huge transom, but not a tiny one either. I took everything apart and was surprised to find the upper wings are separate pieces. Makes sense now that I look at it, because you couldn't fit it in otherwise. Anyway, the port wing piece is all but gone and the rot was starting to migrate to the lower piece. Structurally, there was never any problem - vetted by the numerous attempts I'd made to try and flex the transom by hand.

Anyway, I'm going to screw in some eyelets and use the hoist to pull it up tomorrow. I've got 12-ply 3/4" plywood, epoxy, and fiberglass cloth all ready for the job.

Tomorrow: Hoist, laminate the rough-out of the 3/4" and trace the old transom out. I'll make the final cuts once the glue dries.

Honestly, it's all going a lot easier than I thought it would. My wrists are sore from removing the 11-thousands screws that attached the splashwell though.

 

[Joe_the_boatman]

Re: Transom plywood

Just wait 'till you get to put all those screws back in! (I'll be doing that today or tomorrow).

If you're still looking for ideas, you might want to check out what I've posted before about my transom replacement: http://forums.iboats.com/showthread.php?t=243773

Mine was in 3 pieces also. I'd recommend going to a single piece - it's easier to install in my opinion, and stronger. Basically, cut the aluminum sheet that's over the sides and bend upwards to allow the transom to slide up. The cuts will be covered up by the corner cap when you're done.

I used a pry bar and 2X4's and pushed up from the bottom to get mine out. If it's as stuck as mine was, you'll end up lifting the boat before it comes out. Hopefully, you'll get lucky.