What's the best material for a deck?

[71kidcasper]

I'm ready to install the new deck in my 20sf and I'm planning on doing it with 5/8" marine plywood. Is this a goood choice for thickness? I have already raised the stringers 3/4" and I'm planning on putting 1x3 mahogany on the bottom of the plywood and running it laterally, that way I will gain a total of 1 1/2" in height over the old deck. Hopefully this will allow for better drainage.

[FELLOW-SHIP]

When I re did the deck on my 23 I used 1/2” plywood to replace the lamination inside the two skins of the deck it is very solid. If I were doing your deck removing the whole thing raising up and then setting in a new one. I am sure ½ to 5/8” would be plenty strong enough. The one thing I would do is laminating both sides of the deck with one or two layers of glass for stiffness and to prevent water from getting in. I did that both for my gas tank deck and for the deck part under the CC it is unbelievably strong.

FellowShip

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My motto: Just for the Grins

[oldbluesplayer]

for what it's worth, when I redid part of the floor on my 20' Seafari, what I found for original core was 3/8" plywood in 6" squares, under the seat pedestal, and 3/8" end grain balsa core all the way back from that. I took off the top skin with a circular saw, set for a shallow cut, took out the wet core, left the inner (lower) glass skin in place - then glassed in new 3/8" plywood, then reglassed the top skin back on, and seamed the cut lines.

The result is solid as a rock - I think the key is the glass/core/glass sandwich construction.

Bill

[71kidcasper]

Oldbluesplayer, Fellowship
I agree that the glass/core/glass combination is the key to strength in any lamination. I'm just wondering if the 5/8" is overkill and maybe I should be using 1/2". I'm planning on putting the mahogany strips on atleast 20" centers.

Thanks for the feedback!

[FELLOW-SHIP]

Ha 71

Since you are doing the 20 footer and weight in the entire boat is a issue with them I would go with ½” plywood because of weight. I really like weight in boats, for me it gives the boat a better ride in the chop. But, to much weight on the 20 footer could have a adverse effect. Theoretical speaking you would not go out in 4-6 foot seas needing a lot of extra weight to help absorb the pounding but there has been times I have with my 23 footer. As far as stiffness in the deck with the lamination of glass on both sides that’s really not a issue.

FellowShip

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My motto: Just for the Grins

[Yamtt125]

What type of plywood did you guys use for the floor? I used marine ply for my transom, but is it really worth it to use it for the floor too, even through your just going to glass both sides? What other types of plywood are there for this application?
Thanks
-andrew

[FELLOW-SHIP]

I used marine grade plywood there are a few grades of quality and for the floor if you use epoxy and first wet it down with epoxy to soak in you could use the cheapest quality out there. But I would stick with marine ply because of the glue and plugging up the holes on all marine grade plywood. It seems that the higher the number of lamination ply’s of the wood increases the cost of the stuff.

FellowShip

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My motto: Just for the Grins