Waterproof Baltic Birch Ply?

[gerryv]

Can anyone tell me if there is a waterproof version of baltic birch ply available and, if yes, who produces/sells it?

[Gary Campbell]

Gerry....
I have not seen/heard of any veneer ply thats waterproof. Whats the application? Could one of the Sinta clones work?

[bleeth]

The closest you can get to "waterproof" birch ply is marine grade exterior. Like Baltic Birch the plys are thinner and cleaner than standard plys, clean clearcoatable faces are available, and the glue is non water soluble.
All ply for exterior use still needs to be protected by an appropriate finish (spar varnish, linear poly-urethatne, Cetol, etc.)

[Acmeaviator]

Like Dave and Gary I've not heard of any - and I use tons of baltic. In my experience there is no such thing as a "waterproof" wood product as such - only ones that hold up a bit longer without proper care:D

[bleeth]

Well you could always build out of solid cypress or Ipe:)
Won't have to worry about it rotting or falling apart for a few centuries anyway.

[knight_toolworks]

you can get appleply with water proof glue. but thats not the same thing.

[gerryv]

The application is pretty unusual. It's for large (24" tall) pulley blocks that will be deployed below the surface in seawater. I'm trying to lower the cost of doing them in plastic which gets pretty expensive, especially when doing a series of prototypes.

Some options I'd considered are laminating teak, also pretty pricey, or using regular Baltic birch and fully encasing it in a waterproof finish.

Thanks much for the feedback; some good thoughts that I'll look into.

[knight_toolworks]

I doubt any ply would hold up. Well if it is fully covered in epoxy of several coats it may. what plastic are you using now?

[gerryv]

PVC because it machines well and is cheaper and UHMWPE because it's light and durable to the extreme. I may just do my modelling with wood and then stick with the plastics for the prototypes and test units.

[woodworx]

4x8 sheets of baltic birch have a exterior phenolic glue. You will see the dark colored glue lines, as opposed to the 5x5's with interior glue. Any one who uses a lot of baltic birch, knows availability is low and prices are high right now.

[bleeth]

For that application I would use purple heart. Although often thought of as a "decorative" wood as lumber it has been used for heavy boat framing for quite some time. Ironbark is another alternative (IPE). Both are water resistant, available in heavy dimensions, and less pricey than teak. They are also strong as hell and would work fine as blocks.

[Gary Campbell]

Gerry...
For your underwater application there are no acceptable wood products. Plywood would be totally out of the question. Some solids, like Dave mentions, of course would work, but to me, plastic or aluminum would be the only choices. PVC TYpe 1 solid is one of the cheapest structural plastics. All the HDPE's and UHMW's are more money.

[dlcw]

There is water resistant and water proof. Some types of wood/plywood are water resistant but not waterproof. You have to find a product that can be immersed in water and the material and any glues will be able to stand up to the immersion. Epoxy is water proof. Most other glues I've worked with are water resistant, but not water proof.

So in short, like Gary said, there are no wood products that can be immersed for long periods of time and not have problems. There are woods that can be outside in the rain and they are ok.

[gerryv]

Clearly, the prevailing wisdom is that it doesn't make sense to use wood, especially ply, in this case. I'll go with that. Thanks everyone.

[billp]

Might be tough to get the sizes you want, but this wood has worked underwater for a long time....
http://www.lignum-vitae.com/

[knight_toolworks]

Might be tough to get the sizes you want, but this wood has worked underwater for a long time....
http://www.lignum-vitae.com/

you think plastic is expensive. I have not looked at prices but it used to be 60.00 a pound.