Marine grade plywood or high grade plywood for catwalk?

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Eddie Bait

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The scenario: I am looking to cut a 3/4" 4 x 8 sheet of plywood to go on top of my trailer and under my rollers, to be used as a heavy duty catwalk. I will cut the plywood to the formation of the trailer and bolt it down accordingly. I have also purchased heavy duty outdoor boat carpeting with the proper glue.

The situation:The salesman at Fleet Farm said I needed a high grade non-marine plywood, because that has a ultra smooth side for the glue and it won't delaminate. I originally said I needed a treated plywood and he said that the treated plywood is made with glues that will separate when submerged in water.

The question: After further thought, should I stick with the high grade plywood I purchased, or should I return it and pick up the treated instead? The high grade plywood was $32.00 a sheet! But I don't want my catwalk to rot in a few years either.

What is the answer? To be continued....

Any info would be greatly appreciated,
Thanks,
 
Personally, if it were me, I'd stick with the high-grade non marine ply and waterproof the living daylights out of it. I say that because if it is going to be affixed to the trailer then it is going to be submerged often. Not only that, but if it is going to be carpeted, the carpet is going to hold water against the wood at least until it dries naturally.

I would not put treated wood anywhere near where my boat is going to be, that stuff scares me. Treated wood contains copper. Copper and aluminum is a bad combination causing pitting and corosion. Over all, I think I'd have to go the high-grade route. At least you know you have bought yourself some extra time before you have to replace it that way. Good luck!
 
What would you use for a water proofing agent?

I am glad you mentioned that, as I am looking to make a grate system in the back of my tinny for the gas can and battery to sit. I was going to use treated, but I believe I will now use non treated and H2O proof as you mentioned. Just need to know what to use to seal it. I am looking for a value based sealer as I am kind of a cheap guy.

Thanks.
 
You can buy a sheet of waterproof MDO plywood and a quart of epoxy resin to seal it with for less than what you were going to pay for that sheet of marine grade plywood.

Don't skimp on the sealer, it's your best defense against water intrusion... and water intrusion means rot and having to replace what you built... which is more money.
 
I'd pass on the carpet, sprinkle sand on the wet paint or sealer or use anti-slip material.
 
What if I would just put 2 coats of rustoleum top side on it with the anti slip additive?

If I did so, would I still need to epoxy it?
 
jigngrub said:
You can buy a sheet of waterproof MDO plywood and a quart of epoxy resin to seal it with for less than what you were going to pay for that sheet of marine grade plywood.

Don't skimp on the sealer, it's your best defense against water intrusion... and water intrusion means rot and having to replace what you built... which is more money.


+ 1
 
What I'd do is completly outta the box. I'm assuming that what yer considering as a "catwalk" is a walk way down the tongue of the trailer. What I'd do is repurpose some big rig step sections...


Box+Close+Up+_1_.JPG


... step sections come in aluminum and steel. Attach with U-bolts. They'll probably cost just as much if not less than the material and labor to do a wooden set up. Google-fu some local truck stops around you. Some may have chrome shops that can order various sizes for you.
 
Ditto on the MDO, definitely preferred.

That said, . . . . the most important aspect are the veneers; you want plywood without any gaps or voids, especially in the top and bottom veneers. Look too to the edges - those voids are where you can see the lower quality of the internal veneers; often there were knots in an internal veneer or two edges where the mill joined two veneers and then sandwiched them butt to butt as an internal veneer of the sheet.

The point is that water penetrates where the veneer is discontinuous, where those eye shaped patches are seen on the surface veneer, or where there are similar patches, holes/gaps/voids that you can see only at the edge of the sheet. Sealing helps, especially the edges, but continuous internal and external veneers are the best foundation. MDO incorporates this idea.

As for bolting it down, for each bolt, I'd put a stainless fender washer between the plywood and the trailer so that the wood will stand slightly proud of the trailer and so that air can get in there to dry it out. For the same reason, I'd also just sprinkle sand onto your wet paint/sealer for a non-slip finish; personally, I'd seal the edges and just stain the surfaces.
 

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