Binding / Purfling (paua!)

[rccosta]

I’m about to route the binding channels for my acoustic build using the router with ball bearing method.

As you look at the soundboard, the scheme I’m following is:
Curly maple (0.08”) / bwb (0.04”) / paua (0.098”) / bwb (0.04”) — for a total binding+purfling width of 0.178”.

The curly maple channel will be routed to a deeper depth while the bwb/paua/bwb will be on a less deep channel, depths of 0.25” and 0.05”, respectively.

My kerfed linings are 7/32” (0.21875”). I thicknessed my sides to 0.08”, and my soundboard to 0.105”.

Am I at risk of routing my soundboard clean off the guitar?? The total width the soundboard has to latch onto the sides on is comprised of the thickness of the sides (0.08”) plus the width of the kerfing (0.21875”), for a total of 0.29875”.

Thus, the amount of wood the soundboard has to be securely glued onto is 0.29875”-0.178”=~0.12”.

Granted, the inner channel (bwb/paua/bwb) is only going to be cut 0.05” deep, and thus won’t be going through the entire soundboard (0.105”), I fear that the combined thinning of the soundboard plus very limited width of kerfing that the soundboard is now wholly glued to, uninterrupted by purfling channels, could pose a serious structural risk to the guitar.

Should I have bought a narrower paua? Should I have cut my kerfing thicker knowing I was going to make such a thick purfling design? Is there no risk at all?

[Glen H]

Think of it this way: the wood you are removing from the top is being replaced with purfling and shell. With glue it’s all one unit essentially. Cant count the number of guitars with wide purfling and no tops falling off.