Glue Help

[nautiguy]

I'm about to start working on a replacement water tank for San Souci. It will be Finland plywood with cedar (I think) framing, all parts epoxied before and after assembly.
I picked up a jug of Titebond III glue because I was advised that it was the strongest glue that the yard carried. (The yard is McBeath Hardwood in Berkeley, CA.) However, when I read the label carefully I noticed that it is not recommended for use in places where it will be submerged. I thought that I remembered that professionals on this forum think highly of Titebond, so now I'm confused. Should I look for something else? Is Weldwood Plastic powder better? Should I be looking for Resorsinol? I am confused!!!:confused:

Norm

[Bruce Hooke]

If you are going to epoxy everything before and after assembly then that would be the obvious choice to use as the glue for the tank too.

Various people have reported good results with Titebond III but I think the general consensus is that it is risky to use it in a place where the joint will be submerged in water.

For what it's worth, strength is rarely the deciding factor with glue choice. Most common glues are stronger than the wood itself, which makes the actual strength of the glue a moot point.

If for some reason you do not want to use epoxy then Resorcinol is definitely waterproof. However, make sure you pay attention to the instructions related to temperature, clamping pressure, and so on. The high clamping pressures and tight joints called for with Resorcinol often make it difficult to use.

[Jim Ledger]

Ditto on the epoxty

But why Finland plywood? If it's what I think it is, I'd be leery of using it. It's a high quality ply, lots of even thickness plies, no voids, but it's made from Birch, a relatively non-durable species. I'd be looking at some marine ply for this application.

[Thorne]

As above, use epoxy. If you want to buy locally and get excellent technical advice along with it, go to Smith & Co. in Richmond -- they sell slow-cure epoxy that is made right on the premises, and pioneered CPES and oily-wood epoxy mixes.

http://www.smithandcompany.org/

[JimConlin]

Birch plywood will delaminate and rot before your eyes. Epoxy will tolerate submersion, but good luck finding one whose maker will OK it for contact with potable water.

The practical answer is to use a manufactured polyethylene tank. They will last forever, are OK for potable water and are not expensive. I've used tanks from Ronco Plastics (http://www.ronco-plastics.net/marinetanks.html) and there are many other manufacturers.

[nautiguy]

Jim & Jim:
I opted for the Finland Birch for two main reasons; first, all the plies are void free and therefore it's very strong. Second, the glue is very strong, very high in formaldehyde. Delamination will not be a problem. a lot of epoxy should solve the rot problem. Once the tank is finished it won't ever be subjected to degradation due to the elements.

Jim C:
The reason that I am building rather than buying is that I need to fit the tank to the shape of the hull, which has a lot of curve. All of the ready made tanks I looked at will result in major loss of tankage.

Bruce and Thorne:
You've convinced me that epoxy is the best way to glue the tank together. I am a long-time believer in CPES, going back to the time of Chemist and his explanations, during the time of the great debates, of why it works. I'll visit Smith's and pick their brains for the best formulation for this application.

Thank you all for your comments, it's why I love this place.

Norm

[kc8pql]

Alaya's water tanks. 3/8" Marine grade Doug. fir ply. 25 gal each. epoxy/glassed inside, epoxy glued and glass taped joints inside and out, epoxy coated outside. Trouble free for the last three seasons. See the chapter on tank construction in the Gougeon's Book.

http://i35.tinypic.com/m7sun6.jpg