Ladder-braced parlor guitar

[Dave Bagwill]

Oh hey, Kevin, I'm not discouraged at all - that's how we learn stuff.
IMO, and from what I've heard and read, the smoothness of a gluing surface is a good thing, so I don't think it was a contributing factor.

I'm going to guess as a first approximation that there was not enough glue used. Epoxy is not just slopped on - I roll it out very thin, per instructions; but TB is a different animal and I may have starved the poor thing.

That being said, it is a fact that adhesive manufacturers formulate different glues for different purposes. If original TB was the best they could do for lamination, Franklin probably would not have gone through the trouble of developing specialty glues.

It still seems to me that my experiment should have worked.

[Dave Bagwill]

P.S. = from a Franklin online statement (not the answer to my letter):

"Our work has shown that a smooth surface will always have higher strength than a rough surface. Two-hundred grit or higher sanding to get flat or tight-fitting joints works well.

Wood glues work by attaching to cellulose on the wood and the smoother (tighter) the joint, the less adhesive is needed to bond the surfaces. Less adhesive gives fewer areas of imperfections (bubbles, skips, dust and gaps) where stress can accumulate and cause glue line failure. Also, wood glues tend to be around 50% solids and therefore shrink when they dry. If the rough surface is too “gappy,” as the adhesive dries and shrinks, it will pull away from one surface or the other leaving gaps in the glue line, which again will concentrate force when the joint is stressed. This is why wood glues need to be clamped. Clamping keeps the surfaces in contact as the glue shrinks and dries.

A note of caution on smooth surfaces: Burnished areas may be smooth, but will not bond. Burnishing causes the cellulose to change chemical characteristics and thus not bond to the polyvinyl alcohol portion of the wood glue. This can be tested by putting a drop of water on the surface of the wood, if it doesn’t soak in, the surface is burnished or sealed and should be sanded until cleaned of the burnishing."

[John Parchem]

Dave sorry to hear about the delamination.

When vacuum bagging are you using a hand pump or a continuous vacuum pump? My thought centers around sealing the water of the glue in a bag. I know when I am gluing in my vacuum box with a vacuum pump running the joint dries faster as I am guessing the water is gassing off in the vacuum and getting pumped out.

I do not think it has any thing to do with the gaps in Franklin's response as it seems to be a canned response.

[Dave Bagwill]

Continuous-run, John. I haven't heard from Franklin yet but the amount of glue used might be the issue.

[Lonnie B]

Dave the reason I said perhaps the glue was too thin in the beginning. Is I had exactly the same thing happen to me before. Different situation and circumstance but same problem and same results. Still interested in what Titebonds response will be.

[Dave Bagwill]

I thought I did use plenty of glue, compared to what I normally use for other applications. The difference was that I rolled it into the wood pretty well. Maybe that did not leave a 'wet' enough surface for TB types of glue? So in that sense it was too thin on the surface, perhaps.
Nothing from Franklin yet.

[Lonnie B]

That was my thinking also. When you mentioned rolling the epoxy. I thought maybe you rolled the glue also. Oh well that's why we do what we do. That won't happen to you again I bet.