marine grad wood or treated plywood for my transom?

[boatersam]

replacing my transom..not sure what wood to use..some say marine grade..some say regular pywood..cant really afford the marine grade would it be ok to use plywood and water seal it?

 

[snapperbait]

Re: marine grad wood or treated plywood for my transom?

What kind of boat are you replacing the transom on? Jon boat? Fiberglassing in new transom in a fiberglass boat?

 

[JB]

Re: marine grad wood or treated plywood for my transom?

Marine grade plywood and pressure treated (exterior) plywood differ in only one significant way, Sam.<br /><br />PTP may have voids in it; Marine grade doesn't.<br /><br />If you want maximum strength, use the more expensive Marine grade. For light duty boats, save a few bux.<br /><br />Good luck.

 

[Bondo]

Re: marine grad wood or treated plywood for my transom?

For Glassing into a Fiberglass Boat.... <br />CDX Plywood Sheathing......<br />For bolting into an Alum. boat......<br />P/T Plywood.....

 

[boatersam]

Re: marine grad wood or treated plywood for my transom?

replacing the transom on a 75 sleekcraft..150hp mercury inline..

 

[crab bait]

Re: marine grad wood or treated plywood for my transom?

if you can swing marine,, do so..<br /><br />voids in plywood below or near waterline can cause condension in the dead air of the void an rot from the inside out.. by way of differential of the air an water temp...<br /><br />next best is ab doug fir exterior ply.. <br /><br />no home center carries it .. but any lumber yard can get it in a week..

 

[hi-speed]

Re: marine grad wood or treated plywood for my transom?

Marine plywood has been treated to resist moisture in a marine enviroment.<br />You can use ac fir make sure you fill the void around the outside edge of the wood with bodyfiller or you can mix a putty yourself using resin mixed with a small amount of cabosil and grinder dust that has been sifted through 1/4" poultry mesh.<br />I hope this helps.

 

[BillP]

Re: marine grad wood or treated plywood for my transom?

Marine grade ply has the panels laminated at 45 degree angles, exterior and other plys have it at 90 degrees. Marine is MUCH stiffer...don't try to cold mold with it. Marine and exterior use the same glue.<br /><br />PT ply is available in marine grades too. Several companies make the stuff but it isn't easy to find at the retail level. Resin will stick to CCA processed pt wood...things have changed since the early days. Exterior ply is available in high grades where voids are far, few and small, it can and has been used in a lot of boat applications, including boat building. Chances are you won't find high grade exterior on the shelf and will have to order it. http://www.apawood.org/ <br /><br />For most trailer boat outboard applications two layers of the cheapest 3/4" ply set in glass is overkill. Motors clamp a large area and spread the loads over voids. The cheap stuff was used for transoms in production boats for many years and the only problems were from water getting to the wood and causing rot.

 

[sailorkula]

Re: marine grad wood or treated plywood for my transom?

another idea is to build up the transom with ply, glass cloth, and/or glue/resin...... use 1/8" or 1/4" mahogany ply and use a waterproof glue(duval-cold waterbased resin glue. this is inexpensive) and build up the layers to the desired thickness... then glass the last layer to the transom and hull sides... a piece of advice keep the wood up off the hull bottom and cove the glass and resin/with cabosil ..... make sure there is no air pockets.. the space that you leave will help keep moisture(fiberglass is porous) from getting to the end of the ply

 

[CalicoKid]

Re: marine grad wood or treated plywood for my transom?

I don't like Pressure Treated wood because of the moisture in it. Some of it is just dripping wet! Wouldn't this cause adhesion problems when building transoms etc? Are there synthetic boards available that would work as well or better?

 

[airman]

Re: marine grad wood or treated plywood for my transom?

I replaced the transom and some of the flooring in my 21' cuddy 5 yrs ago. I used marine grade for the transom (thank God!) and exterior for the flooring. This weekend I'm going out with a die grinder and cutoff wheel to cut out all the rotten floor. There is no strength left whatsoever. I'm just hoping that I can get all the floor I need without pulling the motor again. Marine grade only for me now! I didn't want to spend the $ to do it right, now I'm finding the $ to do it twice.

 

[BillP]

Re: marine grad wood or treated plywood for my transom?

Hey Airman, if exterior rotted on the floor it got wet. Regular marine ply would have rotted there too. The only type that wouldn't have rotted if it got wet is pressure treated ply.<br /><br />Here's another link on pt wood through Glen-L.<br /><br /> http://www.glen-l.com/wood-plywood/boatbuilding-plywood.html

 

[airman]

Re: marine grad wood or treated plywood for my transom?

Not to be disagreeable but the rotten floor area butts directly against the transom, which seems fine. I too think water must have gotten in there but I can't figure out how. The boat was stored under a lean-to in a desert. I thought for a little bit that it was rodent damage butI think now that it's just rotten. I'll know more in a few hours. Maybe I'll find the transom is rotten in the hidden areas.

 

[boatersam]

Re: marine grad wood or treated plywood for my transom?

Thanks for the replys..I went out and bought some pressure treated ply the other day and have began cutting the new transom.. the wood looks promising... any other tips would be apreciated..

 

[dixie420]

Re: marine grad wood or treated plywood for my transom?

heres a tip sam, take that pressure treated wood you bought and build a house or something with it. pressure treated wood is different than marine grade wood, pressure treated DOES use different glue than marine grade. pressure treated wood should NEVER be used in marine applications UNLESS, you are using it somewhere it will be exposed to the elements. <br /><br />now go back to the hardware store and tell them you want a sheet of 3/4 AC, dont settle for BC. wanna know why ? ok, pressure treated wood is not a good choice for something you are going to fiberglass around. pressure treated wood is very wet, you already know this much. what happens when you fiberglass wood, the wood absorbs the fiberglass rosin when you apply it, this is because the wood is dry. AC plywood uses a waterproof glue and is acceptable for marine applications. pressure treated wood will rot eventually if its on your boat and it gets wet all the time. if you do a good job fiberglassing the boat, ANY plywood will stay dry. go ask them to show you a sheet of high dollar marine grade ply, i guarantee you it wont be dripping with additives like pressure treated. there is a glue called gorilla glue, its like 5 dollars for a bottle. you can glue two sheets of 3/4 ply together with this stuff and it will be as strong as one sheet of 1 1/2. please dont use that pressure treated wood on your vessel, the fiberglass will never form a good bond to the wood and it will start to crack and break off as the transom is stressed.<br /><br />any wood will stay dry if its fiberglassed properly. <br />marine grade, pressure treated, cheap stuff, will all have a very short life if exposed to the elements.<br />AC plywood IS exterior wood, the glue is pretty much the same as marine grade. and a sheet of 4x8x3/4 is about 55 60 dollars, a sheet of AC is around half that.

 

[BillP]

Re: marine grad wood or treated plywood for my transom?

dixie420,<br /><br />MOST of what you posted is totally opposite of what the APA and other pt ply mfgs publish. They are as credible as it gets concerning plywood. <br /><br />ALL pt, exterior and marine plys use resorcinal glue. <br /><br />Polyester resin sticks to pt wood if the moisture content is low. The CCA process has no detrimental effects on resin sticking. <br /><br />AC is not exclusive to exterior ply, it is just the most common grade you find it in. Exterior comes in other grades too (I have ordered AA & AB exterior).

 

[boatersam]

Re: marine grad wood or treated plywood for my transom?

dixie thanks...but I already cut the pattern out of the PT ply..I hope that the resin will stick..and yeah the wood is pretty wet..I'm letting it dry clamped together so it wont worp.. for my sake I hope you are right though BILL..thanks.. <br /><br />Bill you said polyester resin..what are the types of resin I can use...the stuff at home depot I was looking at was Bondo fiberglass resin..is this ok..or anybody..what resin do I use..

 

[boatersam]

Re: marine grad wood or treated plywood for my transom?

Also when I glue the tow 3/4 pieces together..do I just put a thin layer of resin and cloth and sandwich them together and clamp them together? that's what I was told to do..Please help?

 

[dixie420]

Re: marine grad wood or treated plywood for my transom?

yeah well how many boats have the apa rebuilt. i dont speak from websites i have read over and studied i speak from working on boats and seeing what works and what dosent. other than that, you may know more about wood than me. you said fiberglass will stick to pt wood if the moisture content is low, true, but it dosent stick as well as non pt, well if my eyesight is still good boatersam said his piece is pretty wet. oh and i never said anything about ac being exclusive to exterior wood, AC is the least i would settle for in a boat transom, if you want to put better wood in there, go ahead it wont hurt anything. but if i read correctly, boatersam is looking for the best and cheapest way to do this, not the most time consuming most expensive way. go run back to plywood.com and read up so you can post again. i dont speak from stuff i read on someone elses website, i soeak from building boats and seeing boats stay together and seeing boats fall apart. currently i have a trailered boat that was rebuilt 12 years ago and the transom is as strong today as it was then, i used 2 layers of AC 3/4inch, and about 3-4 layers of matting. i can send you some pics if youd like.

 

[Ralph 123]

Re: marine grad wood or treated plywood for my transom?

I gotta tell ya, you guys have guts! I read through these project posts and just shake my head. I'd never enjoy a single day out on the water with some of the thrifty solutions. I'd be too paranoid the next time I hit the throttle would send me to the bottom....<br /><br />At the beginning of the season here a guy was out with three kids motoring along in Nantucket Sound when his transom broke off and sent to the boat to the bottom in seconds. Luckily the were spotted floating and saved. Now it could have been rot or whatever but who knows, maybe he used the wrong plywood on his transom and it worked good for 1 season and then next, blub, blub, blub