Question about sealing the plywood before skinning w/ alumin

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Question about sealing the plywood before skinning w/ alumin

Postby hartk1213 » Thu Nov 26, 2015 10:33 am

When I skin the trailer with aluminum is there anything I need to do to seal the plywood, I know that I should use some sealant around the edges of the aluminum when I put it on butbi just want to know if I need to apply urethane to the edges of the wood or if I could just paint it or if i need do to anything at all?
Thank you in advance
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Re: Question about sealing the plywood before skinning w/ al

Postby tony.latham » Thu Nov 26, 2015 11:35 am

hartk1213 wrote:When I skin the trailer with aluminum is there anything I need to do to seal the plywood, I know that I should use some sealant around the edges of the aluminum when I put it on butbi just want to know if I need to apply urethane to the edges of the wood or if I could just paint it or if i need do to anything at all?
Thank you in advance
-Hartk1213


Having had a commercially built teardrop that managed to have problems with water along the wall edges in the galley, I've got strong feelings about this. I think most if not all commercial trailers fail sooner or later because water gets inside the walls. It's an area where us homebuilders can easily set a higher bar.

I use Raka thin epoxy (127?). Two coats. Epoxy is the choice for wooden boat builders. It's not that expensive and is easy to apply with a squeegee. I buy their pumps for measuring. Their three coat kit will do a drop. And epoxy the floor of your galley... sooner or later you'll spill something in there.

http://store.raka.com/3quartkit.aspx

The other option, in my book, is to use several coats of "The Mix", a highly diluted polyethylene oil based varnish. It has a great following on this forum. I'd feel comfortable with either method but will stick to epoxy.

Tony
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Re: Question about sealing the plywood before skinning w/ al

Postby coyote » Fri Nov 27, 2015 4:20 am

how successful is spraying the Raka epoxy/painting over it? Coyote
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Re: Question about sealing the plywood before skinning w/ al

Postby tony.latham » Fri Nov 27, 2015 9:52 am

I've never tried spraying epoxy. The stuff is different than a varnish. It likes to be moved with a plastic squeegee.

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Re: Question about sealing the plywood before skinning w/ al

Postby KCStudly » Sat Dec 05, 2015 9:01 am

tony.latham wrote:The other option, in my book, is to use several coats of "The Mix", a highly diluted polyethylene oil based varnish.

I am pretty sure he meant polyurethane, but otherwise I agree with Tony. If you can afford the epoxy and are well versed in the safety precautions using it, that is the best solution. When using "the mix" I have a slightly different opinion that may have something to do with the high build poly that I have been using. I like one or two coats at 50/50 then a couple of coats at full strength. IMO, once those first couple of coats go on things are pretty well sealed and you are just wasting mineral oil. YMMV.
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Re: Question about sealing the plywood before skinning w/ al

Postby Toytaco2 » Sat Dec 05, 2015 9:15 am

I must have missed this somehow. Can someone tell us: what is "The Mix". Is it a home brewed mixture or some commercial product?

Thanks,
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Re: Question about sealing the plywood before skinning w/ al

Postby KCStudly » Sat Dec 05, 2015 9:58 am

Mineral spirits mixed with oil based polyurethane; home brew.

The solvent helps the tubular wood fibers pull the poly into the grain of the wood, especially the end grain. There are two theories about multiple coats. One camp believes that once you have done the initial coat the fibers will be more or less sealed and any more applications of the thinned stuff is just a waste of solvent. They say go ahead and lay on pure to seal and "cap" the wood in fewer operations. The other camp feels that multiple coats of the thin (some even go to 25/75 ratio for the first coats) allows for better penetration and filling of the grain adding protection even if the outer finish becomes worn or damaged.

What I think I have observed is the first thinned coat sinks in better than pure, but anymore than two coats thinned doesn't seem to go anywhere fast; it's not really soaking in anymore and it isn't building up much either. All of my applications have been on a good grade of Okoume or cedar using a high build poly, so it may behave differently on pine or fir and when using standard grade product, but that is my experience.

Knowing what I know now, I would follow Tony's advice and use epoxy.
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Re: Question about sealing the plywood before skinning w/ al

Postby tony.latham » Sat Dec 05, 2015 10:33 am

I am pretty sure he meant polyurethane, but otherwise I agree with Tony


KC's right. I'll blame it on my iphone's spell checker, but who knows. Maybe it was my thumbs.

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Re: Question about sealing the plywood before skinning w/ al

Postby Toytaco2 » Sat Dec 05, 2015 10:51 am

Thanks for the explanation. I actually did use that process on the interior of my build. I just didn't remember it being referred to as "the mix". BTW, it worked great and I'm very happy with the results.
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Re: Question about sealing the plywood before skinning w/ al

Postby bherron1 » Thu Apr 14, 2016 6:11 pm

Jump over to the Bateau wood boat building forums to see how to seal the plywood on the outside. Resin and cloth, you will solve the water intrusion problems. If it seals a boat hull it will seal the td or ttt
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Re: Question about sealing the plywood before skinning w/ al

Postby Graniterich » Thu Apr 14, 2016 10:12 pm

Epoxy is the best , a few coats of high quality exterior house paint that was mixed to the wrong color is only a few dollars at big box stores is only a few dollars if on a budget
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