Marine plywood needed? Where to find in OC?

[mondorally]

I'm looking for a few sheets of plywood to make seat bases. Can you guys that have made seat bases help me out with the following:
Is marine plywood required? If so, where do I buy it. I'm in Huntington Beach, work in Gardena. Regardless, I'll be at minimum coating everything with resin, possibly line-x.
What is the most common plywood thickness for seat bases?
To attached the pieces together do you recommend nails, screws, some combo, corner blocks, angle?
And where
Thanks
-Justin

[Keith E. Sayre]

just a suggestion, copying from the Schiada handbook--probably the biggest
oversight when building these seat bases is the holes that are drilled. Try
to drill the hole a bit bigger than is needed, then resin the inside of the hole
where it was drilled out which will keep water from seeping into the hole itself.
Keith Sayre
Conquest Boats

[Tom Brown]

I don't feel marine plywood is necessary for seat bases. I went with exterior grade ply on the recommendation of a builder and it's been fine for several years. I only used marine ply for the transom.
Required thickness depends on the base design. Mine were done in 1/2" but if it's a big base, it might need 3/4".
Also, not that Keith needs my endorsement, but I've restored two boats and I've looked at a lot of used boats. The problems with soft wood and rot always center around bad rigging, ie: unprotected hole or fastener of some kind.
To mount my seats to their bases, I drilled the base, used an acid brush to resin the holes, and then installed a brass threaded insert. Then I just bolted the seat to the base. This was recommended to me by a builder.
Also, I made sure there was a couple of small drain holes on the very bottom edge of the seat bases and I was careful not to glass them over when I installed the bases. The goal was to allow water to get out and a tiny amount of air to circulate.

[lucky]

i did mine in 3/4 marine - dattoe'd the joints glued and screwed with stainless - I'm hopping to let you know the outcome in 20years

[mondorally]

To mount my seats to their bases, I drilled the base, used an acid brush to resin the holes, and then installed a brass threaded insert. Then I just bolted the seat to the base. This was recommended to me by a builder.
You wouldn't happen to have a pic of what you're talking about here? I'm thinking along the lines of a threaded concrete insert that we use to tie scaffold to buildings but I may be totally off.
Thanks all for the input. Sorry to have to ask a boat related question on the forums.......
-Justin

[It's all Good]

Ganahl Lumber has Marine Plywood at the Costa Mesa location on Bristol. Just drive to the back where the specialty lumber is under cover.

[mondorally]

Ganahl Lumber has Marine Plywood at the Costa Mesa location on Bristol. Just drive to the back where the specialty lumber is under cover.
Thanks
-Justin

[Tom Brown]

You wouldn't happen to have a pic of what you're talking about here?
They are made of brass and they look like this:
http://rtlfasteners.com/Merchant2/gr...550-116619.gif
By the way, I glassed in mahogany corner blocks instead of dados because I was trying to keep the end grain to an absolute minimum.
I'm the president of the local Glastron Owner's Association and I've seen a lot of 60s and 70s boats. Every one of them has gone soft from the rigging points. The screws that hold the seat brackets to the floor go soft 100% of the time. Silicone doesn't help. Use a polysulfide based sealant or resin to seal. The old inline 6 cylinder Mercs has a remote trim pump that would mount to the side of the bilge... they're all soft where the screws go through the wood. The wood is usually pretty solid, except where the screws go through.
That's why I coated all of my wood with thinned down resin 2.5:1 prior to assembly. The wood soaks it up like a wick. If you dip the end of a 2x4 into the thinned resin, it will creep up 6" in 5 minutes, with no problem. You have to use good resin though, not the crap with tons of fillers they sell at Home Depot. Quadroople up on your MEKp also, it doesn't like to light off when it's that thin.

[rrrr]

Marine plywood is made with water resistant glue. Other than that, same as Home Depot.
Treated plywood is made with the same glue, and treated with chemicals to resist water intrusion and rot.
I use treated plywood on floor and transom replacements....

[Tom Brown]

Treated plywood is great if you're going to leave it bare but it warps all to shit if you resin it.