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Discussion Starter #1
Hey All,

Noob question, is the AB Fir marine plywood sold at Lowes and Home Depot suitable for a transom? I can pick it up locally at it's about $25 cheaper a sheet than the lumber yard here in Jax. I plan on sandwiching 3/4" with thickened epoxy, also any suggestions on epoxy brand would be welcomed. I've been thicking either West Systems, Total Boat or RAKA from Gulfstream Composites, stuff is pretty inexpensive. Any and all suggestions are welcome.

Thanks,

-e
 

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Hey All,

Noob question, is the AB Fir marine plywood sold at Lowes and Home Depot suitable for a transom? I can pick it up locally at it's about $25 cheaper a sheet than the lumber yard here in Jax. I plan on sandwiching 3/4" with thickened epoxy, also any suggestions on epoxy brand would be welcomed. I've been thicking either West Systems, Total Boat or RAKA from Gulfstream Composites, stuff is pretty inexpensive. Any and all suggestions are welcome.

Thanks,

-e
Howdy Do Pauper, I'd be very hesitant using the wood for your boat transom from the big box stores due to the moisture content. On a roof or home project, no problem. Epoxy and polyester resins do not like moisture. Kiln dried PT is suitable. Not sure where you are located but Inland Plywood in Cocoa FL. Has it. A composite board is best but you'll pay the price. Wood transoms if done correctly and penetrations are sealed properly will last a life time. West system is good, be sure to add bleeder holes to your ply every few inches to eliminate any air pockets and ensure visually the coverage as it seeps out.
Hope this helps.
 

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I've used the marine ply from Lowes and couldn't tell the difference from the fir ply I bought from a marine supplier. I used quite a bit of totalboat epoxies from Jamestown distributors with good results. With plywood , my first coat of epoxy is thinned down and allowed to cure before laminating together or installing cloth on it. Seal all penetrations and edges and you're good.
 

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Discussion Starter #5
Initially I was thinking coosa, but $275 seems pretty steep given this is a. my first boat with a motor, b. the first time I've attempted a restoration c. I've very limited experience with fiberglass. Having said that, I want this skiff to last as it will be my baby to explore places I can't get to from my kayak. BTW, I'm in Jacksonville, and for the life of me I can not find a boat building supply place here.
 

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Discussion Starter #6
I was going to use the total boat penetrating epoxy to coat first. I was just curious as to the difference in quality from big box marine fir and the local ply distributor. Thanks for the input!
 

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Discussion Starter #7
It's listed as a 1960 Gemcraft on the title with an FLZ HIN... looks like a Johnsen. 14' length and 59" beam. I picked up a 2018 25 merc 4 stroke NIB from the St. Augustine Nor Tech rigger, 20" shaft for a good price.
 

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That's a really stout transom for just a 25hp. That's heavier duty then I an building for my 60hp. I would save he weight and do one full sheet of 3/4", and then double up the clamping board to 1.5".
You don't need penetrating epoxy. A neat coat of laminating epoxy will work just fine. I'm going to disagree with Myakka here. PT plywood should never be used with a resin system, you can't determine what chemicals are in it and bonding issues have been known to happen. Both box stores and lumber yards can be hit or miss, just look through the stack and make sure it looks decent.
 

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sun supply in palatka fl sells certified marine plywood, they cater to the cabinet making industry but they stock some marine or they can have it next day. used them on 3 of the last 5 boats i built. they deliver to ocala and may do so to jax. they will not deliver to your home but you can make arrangements to meet them at one of their cabinet shop delivery points. must say i have not bought from sun supply in a year or more so just assuming they still handle quality marine plywood. 2nd Raka supply, they are hard to beat, will never mention names but went to a shop once that was rebranding Raka resin under another label. non blush resin is only a few dollar more at raka.
 

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My opinion is similar to @firecat1981 - don't use PT! I also over built my transom with two 3/4" sheets laminated to 1.5". It is silly for the 25hp 2 stroke that weights 107#. At the time of the transom replacement, I was trying to match what was on the boat previously instead of calculating what was actually needed...
 

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The pressure treating is in the wood ,not the glue. Ive not used it on a skiff , ive used it above ground tho. Had issues w/ it delaminating and puckering. Good luck
 

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I've read some positive and negative results about glassing over pt plywood. If it were mine, I won't do it.
 

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Hey All,

Noob question, is the AB Fir marine plywood sold at Lowes and Home Depot suitable for a transom? I can pick it up locally at it's about $25 cheaper a sheet than the lumber yard here in Jax. I plan on sandwiching 3/4" with thickened epoxy, also any suggestions on epoxy brand would be welcomed. I've been thicking either West Systems, Total Boat or RAKA from Gulfstream Composites, stuff is pretty inexpensive. Any and all suggestions are welcome.

Thanks,

-e
What exactly are you doing to the boat?
Beefing up the transom or replacing the whole back end of the hull?

If the cheaper plywood is chinese and the lumberyard ply is domestic, spend the extra 25 bucks. Any chinese building material is suspect, imo.

As to sealing against moisture, its the film thickness of the epoxy that does it. Usually a layer of glass that is laid on and well covered with a film of epoxy does the job. I especially like West System. The maker,
https://gougeon.com/
has super extensive technical and testing documents along with outstanding customer and technical support. Visit their site and spend some time reading.

I’d probably add aluminum sheet for the motor to clamp on to keep from cracking the coating over the wood below. But can’t say for sure without knowing more about your project.
 

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Don’t use pressure treated ply.. there will be delamination issues bc if the moisture. Use 3/4 ply and double it at the top for clamping board. Glass it with 10oz or 12 biaxial.. several coats of epoxy over that. It will last forever. When you drill holes into it, over drill them and back fill with thickened epoxy. You will never have issues.
 

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Discussion Starter #16
I wasn't talking about pressure treated (pt) plywood. The Lowes and Home Depot in Jacksonville, FL sell AB marine fir, I just wanted to know the quality aspect if anyone had used it.

In terms of transom thickness, if 1.5" is overbuilt for a 25 hp, what should I use then?

My apologies for the late response, went fishing sat and slept sun.
 

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1.5” is overkill for entire transom. 3/4” across the whole stern with 1.5” at clamping area. I usually do an 18” section in the center @ 1.5” and the rest 3/4” on a small boat/skiff. What most are saying and are right is... you can get away with 3/4” across the stern and just a strip across the top in the center maybe 6” deep that is 1.5” for clamping area. I just do the whole center because that’s how I like to do it for ease of lay up and aesthetics.
 

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the plywood you are referring to will work fine as long as you coat the edges or encapsulate all sides with the epoxy. I have used it myself when short a piece though i much prefer non Chinese meranti or okoume. some older boats ive repaired transoms and floors on look like the manufacturer used CDX and polyester resin and they lasted 15 years
 
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