Saturday, January 9, 2016

Titebond III Test

Since there was a comment on my last post that Titebond 3 might be a better option for laminating fir plywood, and since I have some in the shop, I think another test is in order.  Titebond 3 is a great glue and I have used it in the past, but only in applications where I have been able to tightly clamp it, or screw it down.

I will be laminating my ply layers however without high clamping pressures.  The first layer will be glued and screwed to the framework so clamping pressure is no problem there, but subsequent layers will be nailed down with Raptor polymer nails.  I can weight down the plywood before nailing, but will not achieve anywhere near something you could call clamping pressure.

Nonetheless, I have a feeling that Titebond 3 will be stronger in tension than across the grain in fir plywood.  It is worth checking out.  Here goes:

I rounded the small ends with a belt sander so I can get a wedge in to break them apart.  Glue got smeared on one piece only since that's the way I'd be doing it with the boat - paint on some glue and then lay a panel down and nail it.

I just stuck them together by hand and am letting good old atmospheric pressure hold them together.

We'll let the clock tick and bust it apart tomorrow....

Early next morning the instruments of submission are employed...

And the wood fails, not the glue!

So for my application, and the reason for the tests in this and the previous posts, was to see if either PL Premium or Titebond III would be suitable to laminate the layers of plywood that will make up the bottom, sides and decks of my boat.  In addition to the glue these layers will be fastened with Raptor polymer nails to the tune of 4 per square foot.

Based on this test, and the ease of application of the Titebond III compared to PL Premeium, I am leaning heavily toward laminating the ply layers with the Titebond.


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  2. Speaking of Titebond III...and an earlier remark you made regarding cement...

    it got me to thinking. I posted this on Triloboat talk on the deck covering thread...

    Forgive me if I'm getting stupid..but I have a question.
    Suppose...the boat was assembled from rigid foam..the interior surfaces were laminated with dynel (nylon, polyester, burlap, whatever )...and TiteBound III

    Suppose the Exterior surfaces and high wear areas would be ferrocemented using basalt fiber ( fiber, grid, what ever, it comes in many configurations)...and cemented. Portland cement and sand...concrete..Make a thin shell cement structure with the foam as the mold..

    no ferro no rebar...basalt fiber only. It has interesting properties , such as having the same expansion coefficient as cement...and seems like it should work well for boat building...someone made a cement canoe with it.

    it that configuration completely off the wall?

    would I be wrong or would this technique, if it works, not decrease the cost dramatically?

  3. Foam sandwich construction is used a lot in homebuilt aircraft. I think that for strong skins on either side of the foam Titebond 3 would work with fiberglass cloth because it has more strength and stiffness. I think the cement canoes were made with Portland cement and fiberglass cloth. The cement is strong in compression but very weak in tension so that is why the cloth must be fairly strong and not flexible. Worthy of some experimenting if you are so inclined though. Around here the foam is pretty expensive so I don't know what the savings would be.

  4. A number of our lamination tests over the years have looked good in small, but been disappointing in whole sheets. In one example, WELDWOOD left gaps we could slide a playing card into. The resulting structures seemed strong and held up, but left us with a queasy feeling. Lately we've switched to expansive LPU (Liquid PolyUrethane... mostly Gorilla Glue) which expands to fill any internal gaps.

    I think the RAPTOR nails will be good, but a caution... our bronze ringshanks pulled the ply down at point of contact 'dimpling' the sheets. We seemed to have good glue contact in the nail's vicinity, then gaps in between. Due to cost, we were nailing every square foot... every 6in would, I think, have cut out the gaposis in between.

    Soo.... one thing we've tried without nails (a couple screws to fix position) and good success is to laminate in stacks supported flat, and using transverse, BOWED 2x4s on top, placed convex face down. Clamp the 2x4s around the area, springing them flat for good pressure across the middle. The more the merrier, even with some bar clamps around the edge gaps, if any. This worked well enough (with LPU) that we're reconsidering TBIII, ourselves.

    Ideally, I think vacuum bagging would be the way to go, but have never gotten our act together for that.

    Good luck, and always glad to hear of successful tests!

    1. Maybe I should just bite the bullet cost wise and stick with epoxy for laminating the plywood. If I vacuum bagged - easy enough to do on a sheet by sheet basis - I would have to do the nailing afterward. Reassuring but redundant at that point. The other thing I could do is drive a screw and fire a polymer nail beside it - pull the screw and move on. Time consuming but it would get the clamping density required...what do you think? And, as always, Thanks Dave for your help!