Maritime grade plywood - staining needed?

[Newfie]

I've got some maritime grade plywood to replace the old rotten stuff used for the windows in my Trillium 1300.

I don't need to seal that plywood with Thompson's water seal or anything similar, correct?

[Dan-NS27]

Many people just leave it as it is and will finish with oil or vanish. I have seen others who will use clear epoxy and varnish over it for a durable finish.

[steve dunham]

Marine plywood is neither waterproof or rot resistant

[Civilguy]

Originally Posted by Newfie

I've got some maritime grade plywood to replace the old rotten stuff used for the windows in my Trillium 1300.

I don't need to seal that plywood with Thompson's water seal or anything similar, correct?

This page has some good information about marine plywood.

https://www.thespruce.com/what-is-ma...lywood-2736672

[k corbin]

I make sure to seal the edges of the plywood as that is the biggest problem area. That is were it will quickly wick in water which is what causes rot and delamination in any type of plywood.

You can paint the edges with thin epoxy, the kind used to solidify wood. Sometimes I use a paintable exterior caulk and just rub it well onto those edges, that will also seal up all those short little end grains. It is worth taking the time to do espcially if it is being put around windows.

You might also consider coating it with a mold preventing primer just as an extra precaution. You can get quarts of it at most any paint supply sales area.

As to marine plywood being perhaps considered not worth it. The stuff from the lumberyards is not all that great at rot resistance or water resistance either. But you do at least want plywood that is exterior rated so that you know the glues are moisture resistant. I buy my marine plywood from speciality sources, the kind that is actually meant for wooden boat building. It has minimal voids and is made from rot resistant woods. But it is not widely available, you mostly find it in coastal areas where there is a wooden boat building industry such as the areas around Seattle, Florida, New England, etc.

For the blocking around the windows I put into my trailer I used tight grain, Western Red Cedar lumber. It is naturally rot and insect resistant but I still coat the end grains on it as that is the area that is most vunerable.

[Kai in Seattle]

We got our marine ply from a boatyard near Seattle. It is the most beautiful plywood I've ever seen and the nicest to work with--no voids in the edges, etc.. It stained up beautifully, sealed great, and took paint like a dream. I wouldn't leave it "raw," that's for sure, especially if it was going to be exposed to outside weather.

BEST
Kai

[michelvachon]

I also purchased a 1300 a couple weeks ago. Now that the windows are all removed, I am thinking about using aluminium rectangular bar. May be 1/2''x 1 1/2'' . Do some thread into the bar and screew the windows back in place with stainless screew.... Have you ever eard anyone do this ...

[Kai in Seattle]

Michel, welcome to FGRV! congrats on your new-to-you Trillium.

Where did you use the marine ply, or where are you planning to use the marine ply in your Trillium 1300?

If you're screwing through the fiberglass, be sure to use some butyl tape underneath, watch some YouTube videos and read about how best to seal up your trailer as you don't want any leaks!

[redbarron55]

I know you have the marine plywood, but a good hardwood would hols up better.
If you use Ply then be sure to soak the edges with sealant or paint.
Best would be an epoxy thinned a little with acetone to soak into the wood end grain.
Multiple coats would be better. After the thinned epoxy no additional thinning would be necessary.
If stained the epoxy will make a fine finish.
I made my kitchen counter and folding table out of Lowe's Poplar butcher block with epoxy to seal and finish and it has held up well, even for such a soft wood.
Some oak would make a very nice frame.

[k corbin]

Originally Posted by michelvachon

I also purchased a 1300 a couple weeks ago. Now that the windows are all removed, I am thinking about using aluminium rectangular bar. May be 1/2''x 1 1/2'' . Do some thread into the bar and screew the windows back in place with stainless screew.... Have you ever eard anyone do this ...

I have not heard of anyone doing that. A rot resistant wood is just fine.

But you have not thought that approach through. First of all you are talking about using machine screws which are not particularly coarse threaded. Therefore you have to carefully align all the holes. However you will have a layer of butyl tape between the frame and the shell and that makes it difficult to align the holes. Plus you will be getting butyl tape into the threads of the screws as they pass through that layer. That will make it difficult to get the screws started and fed into the fine threads. A stainless steel sheet metal screw into wood is a lot more practical to work with. Being an aircraft fabricator I know all about threading and screwing into aluminum materials as I have done it thousands of times. You are taking an approach that has far to tight of a tolerance for the type of installation.

But the first and most important step is to make sure you replace the seals on the windows and you have proper weep holes for drainage. If the windows are in poor condition you are going to have leaks no matter what material you use for the surround. It is not the choice of framing material that causes the problems, it is the condition of the sealants that prevent the leaks that cause the issues.

[getaway1]

Hi Welcome ! I replaced the wood in my Trillium 1300 and used rocker guard spray (Canadian Tire has it) to seal the plywood edges on the window strips. I felt that anything I could do to make them last longer was the right thing to do. When I removed the old pieces they were swelled to an inch thick or more and crumbled in my hands as I touched them. The factory was more interested in selling than how long the wood lasted around the windows. Typical for many things nowadays ! Good luck with your trailer repairs and use lots of butyl calk strip (3/4") on the outside of frame edges too! Enjoy your Trillium ! Duane

[David Tilston]

Originally Posted by getaway1

The factory was more interested in selling than how long the wood lasted around the windows. Typical for many things nowadays !

Duane, How long did that factory plywood last?

[Mike Magee]

The edges of plywood can be very well sealed by coating them with Titebond II wood glue. I've heard that it's considerably better than paint for this purpose.

Jim Palmer of Eggcamper always coated the top surface of his plywood floors with epoxy resin, but he left the bottom surface as-is so the wood could 'breathe'; he said that any moisture in the wood must have an avenue of escape. Some splashing from driving in rain will not hurt it, but water that sits on the wood's surface for a long period (such as can happen with an interior leak) can rot it. Other, less expensive coatings than resin should suffice IMO, but coating the top surface with something (even paint) seems like a good idea to me.

After seeing how poorly Thompson's protected my mother-in-law's deck, I have a low opinion of the stuff.