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Im going to do my first backstrip on a koa back. it will be b/w purfling,koa,b/w purfling. the purfling is plastic. I want to sandwich it all on the shooting board. seems simpler than inlaying it and routing a channel. people seem to have different opinions on which way to do it. if i do the sandwich what type of glue will be the best. i plan on building most of the guitar with hhg but have never used it before. all my previous guitars have been titebond and ca glue for bindings. i feel like the best way for the sandwich would be get it all tight in the shooting board and flood it with ca glue. any recommendations?

If I were using plastic, I would inlay it instead of sandwiching it. I would trust the integrity of the joint more that way. Or, if I wanted to sandwich it, I would switch to wood or fiber. It may be prejudice on my part, but I want wood in the important joints.

"Best" is subjective. Personally, I would not use CA for joining plates, whether sandwiched with a backstrip or not. Like Don, I prefer wood or wood fiber purflings. I did use some non-wood binding and purfling materials on my first couple of guitars and had success using both of these adhesives sold by LMI: http://www.lmii.com/products/finishing/ ... -adhesives

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George :-)

Gluing them into a sandwich is fine considering...

The backstrip/purfling should be of sound material and the same thickness as the back wood,

and

The glue should have at least as much structural integrity as titebond or hide glue. (yes, I know that neither is structurally rated but they do perform well in that regard in a dry, not to hot environment)

Side note: I personally would not trust plastic in the mix

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Joe Beaver
Maker of Sawdust

I have wood fiber also I was just going to try something new but sounds like I should just stick with the wood purifying.

I agree that inlaying plastic would be better but you most certainly can join a back with CA. It may be a bit unorthodox even by today's standards but I've done it and it works on guitars that I built over ten years ago. Just be sure to shellac the edges in about 2 inches then join your boards so you have a fresh wood cut but the pours are protected from CA seeping in.

When the subject comes up of whether CA is OK for structural bonds, I always think of what Rick Turner posted here. He said he had been using CA for some time to attach bridges with no failures.

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Joe Beaver
Maker of Sawdust