Walnut and Glue

The runup to D-day saw a massive effort to glue up plywood into gliders, and the early batches didn't hold very well. The trouble was traced to the platen presses (that held the plies together to make loose bits into solid plywood).

(from _The New Science of Strong Materials_, J. E. Gordon) "... a proportion of aircraft plywood was ungluable. The joints in such plywood, made with all due care, looked like any other joints but had no strength..."

The effect is sometimes called case-hardening, and is due to microscopic damage that prevents the glue from penetrating into the wood to make contact with the subsurface (strong, intact) wood fibers.

Sandpaper is a good treatment for the problem.

Reply to
whit3rd
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Howdy,

Thanks for that interesting comment...

All the best,

Reply to
Kenneth

^^^^^^

Using your finger to smear the glue might have something to do with your problem. It could be that whatever oils are on your hand don't mix with the glue. Try using an acid brush to smooth the glue around next time and see if that makes any difference.

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Reply to
Michael Faurot

My first thought at that sort of spectacular glue failure would be 'wet wood'. Wet is not always obvious, but wood above a certain moisture content does not seem to bond well with any waterbased glues that I've used (I haven't used titebond, since it's not commonly sold in these parts; but I understand it to be a member of the 'white glue'/pva/aliphatic family, also).

-P.

Reply to
Peter Huebner

It is in that family. And I'd tend to agree, but this wood was tinder dry. I"m still not sure what the issue was here. I've not had a chance to glue anymore of it, but will let you guys know when I do.

Tanus

Reply to
Tanus

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