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/graphics/00000001/112550-116619.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.

[steve-o13]

lows store

[OCMerrill]

I just finished my re-floor project with my Lavey. I used Marine grade plywood for a little extra insurance then resin coated it 3x before glassing it in a screwing it down.
Ganahl Lumber as stated before has the wood. Be prepared its about $70 bucks a sheet.
I used Mahogony for a few new supports. Resin coated before I installed it.
I used the West System resin at West Marine. Seems to be fine but only time will tell.

[sorry dog]

I never used, but was under the impression that marine ply used higher grades in the inner plies opposed to the D grade inner ply that Depot wood has. Not true?
I know if you want to go real high end I've worked with this ply that's for cabinets that 7 layers for 1/2" and made of oak or birch. It's actually pretty light and seems much stronger than pine.

[mondorally]

Thanks again everyone!
-JH

[Riverkid]

We built thousands of sets of seats over the years with 1/2" ACX from Royal Plywood. You definitely want to reinforce all the stress areas (we used 2X2 blocks and a framing nail gun). The foam is cut around these when glued down and you'll never feel them down by the tack strips. We had a 1/2" seat base with another 1/2" tack strip on top all shot together with a nail gun to give you a 1" bottom to each seat frame. You then clearance the wood cut from the tack strips and they become your seat cushion bases. Next cut some holes in the seat cushion bases with a hole saw or arbor, and route the edges of everything to take all the hard edges off. We further glassed all areas with matt that had curves or angles to ensure they didn't break down over time. Everything then went next door and got 100% flowcoated with quality resin.
I replaced a lot of floors over the years. TB is right - they all rotted where the mounting hardware penetrated and allowed a point of entry for the water to get through the glass laid down.
I have the original 1987 seats we built in my Schiada in the garage. Nobody can believe it's the original interior. Also, when your done boating, pull all the cushions out and flip them over for a bit. It allows any water in the cushions to seep back out through the stitch holes, and also allows the seat bases/pedestals to breathe and allow any trapped moisture in there to evap.
Good luck Justin.
http://www.***boat.com/image_center/data/523/2880Catalina05_096_Medium_.jpg

[mondorally]

We built thousands of sets of seats over the years with 1/2" ACX from Royal Plywood. You definitely want to reinforce all the stress areas (we used 2X2 blocks and a framing nail gun). The foam is cut around these when glued down and you'll never feel them down by the tack strips. We had a 1/2" seat base with another 1/2" tack strip on top all shot together with a nail gun to give you a 1" bottom to each seat frame. You then clearance the wood cut from the tack strips and they become your seat cushion bases. Next cut some holes in the seat cushion bases with a hole saw or arbor, and route the edges of everything to take all the hard edges off. We further glassed all areas with matt that had curves or angles to ensure they didn't break down over time. Everything then went next door and got 100% flowcoated with quality resin.
I replaced a lot of floors over the years. TB is right - they all rotted where the mounting hardware penetrated and allowed a point of entry for the water to get through the glass laid down.
I have the original 1987 seats we built in my Schiada in the garage. Nobody can believe it's the original interior. Also, when your done boating, pull all the cushions out and flip them over for a bit. It allows any water in the cushions to seep back out through the stitch holes, and also allows the seat bases/pedestals to breathe and allow any trapped moisture in there to evap.
Good luck Justin.
http://www.***boat.com/image_center/data/523/2880Catalina05_096_Medium_.jpg
Thanks 'kid for all the info. I actually just bought a bench and 2 buckets from Lee. Luckily he had a set that almost perfectly match the colors of my boat. I just need to make the bases to go with them and want to do it right.
-Justin

[rrrr]

Treated plywood is great if you're going to leave it bare but it warps all to shit if you resin it.
Hey, don't you have some muffins to eat? :D
Haven't had that problem in floors and transoms. Yeah, you're correct though. A bucket seat would not be good with treated plywood.....

[Riverkid]

Lee's buckets are some of the most comfortable out there. Most of the Schi's we saw all had 1/2" wood framed bases with 1 1/2" aluminum L angle through bolted at the top and bottom, with blocks in the corners to keep everything squared up, for the bench. They used SS carriage bolts for the aluminum fasteners and just carpeted over them. Everything through bolted, no screws. They seem to last forever that way. I think he's on to something... :idea:
Buckets had the same, or just bigger aluminum L angle in some race app's.

[mondorally]

I think he's on to something... :idea:
I agree! The seats I removed were 20 years old and structurally perfect.....
-Justin

[BiggusJimbus]

Marine plywood is free of interior VOIDS (no gaps in inner plys).
It's purpose is for structural integrity and consistency.
Regular exterior ACX is perfectly suited to interior parts.

[mondorally]

Marine plywood is free of interior VOIDS (no gaps in inner plys).
It's purpose is for structural integrity and consistency.
Regular exterior ACX is perfectly suited to interior parts.
So if I understand you correct the marine plywood would be recommended for hull layup use (bulkheads, transom, etc.) but not required for a minimal stressed part like a seat base?
-Justin

[BiggusJimbus]

Exactly.
Probably not really even needed for bulkheads, but wouldn't hurt either.
The voids in ply are some of the more common causes of delamination.

[H2oracer]

I race and build my own stock outboard race boats I have seen boats that were built useing exterior grade and luan plywood. It doesn't last, even when sealed. It warps and delaminates. Even in non structural areas. Alot of times the center cores are ground up wood and glue. Yet boats that are built useing marine grade wood both douglass fir and okoume work excellent. I know of one boat that is 30 years old that is still in use because was built with marine plywood. You won't save any money if you have to do the job again. The only other sugestion is to seal it with epoxy and if you do any glueing you can use epoxy mixed with a filler. If you have any questions send me a PM with your phone number I'd be more than glad to help you out. George

[gnRacer98]

Austin Hardwoods in Santa Ana (next to the train station) stocks marine ply. Also carry "aurocco"(sp?) not quite full marine ply but an xlnt plywd. I'd agree with the comments above, 1/2" ACX from El Depot would work fine, especially if your seal with resin.

[Tom Brown]

Maybe Marine ply is required for a submarine but I restored a 1972 Glastron v-173 and the 1/2" CDX seat bases were in as-new condition, wood grained mac-tack coverings and all.
Wood will not rot unless it's moisture content rises above 18%. At that level, micro organisms can exist in the wood and it's those organisms that eat the wood.

[H2oracer]

Maybe Marine ply is required for a submarine but I restored a 1972 Glastron v-173 and the 1/2" CDX seat bases were in as-new condition, wood grained mac-tack coverings and all.
Wood will not rot unless it's moisture content rises above 18%. At that level, micro organisms can exist in the wood and it's those organisms that eat the wood.
The cdx plywood made in 1972 is probly a better plywood than the cdx that is made today. Whose talking about submarines??????????

[Tom Brown]

Whose talking about submarines??????????
Perhaps you're not familiar with the buoyancy of the early 'Tron. :D

[Jbb]

Perhaps you're not familiar with the buoyancy of the early 'Tron. :D
Dive,dive,dive.. :p

[Jbb]

I'm the president of the local Glastron Owner's Association
And he makes all the underlings call him ...."El Presidente"... :p

[Tom Brown]

Si!