A little theory help please

[Dave Bagwill]

Right before the top is sloped from soundhole to neckblock - is each point of the top rim all on the same plane? In other words, if you laid the rim on a flat board, top down, should there be any gaps?

[Kyle Barbour]

That is my understanding of it, no gaps. I would let Ken advise. I'll be watching to see what the verdict is

[ken cierp]

Yep -- it should lay on the table/bench, no gaps, also the neck and tail blocks should be perpendicular to the surface and ideally the entire side profile -- its a good thing! And after you slope the that top edge and set it back on the bench most the rim will lay flat and you should see a small gap at the neck block about 1/16" +/-

[Dave Bagwill]

Before the slope, any irregularities - such as, perhaps, a waist being a skosh high, but anywhere along the rim actually - what would be the cause? I'm talking about 1/16" or less?

[Ken Hundley]

Might be a slight twist in the way the sides were bent....I have a rim like that. I am waiting to finish rebuilding my bender (actually done, need to rebuild the forms to fit it) to re-bend the sides. Basically, the upper and lower bout bent perfectly, but somehow the waist was not bent perpendicular to the sides, meaning the waste near the top is not bent as deep as the waist near the back, causing the rim to be proud at the waist by 1/4" when out of the mold. It will lay flat when clamped, but I'm not thrilled with having to force a rim to shape by gluing it to a top or back. Then again, your issue could be caused by something else. Who bent the sides, and what method? Pipe or bending machine?

[Dave Bagwill]

It's not my situation - another guy who had waists about 1/16" proud, and not a problem, really, when the front slope was done.

[Mark from Ashland]

This is a great topic, perfect for this venue. You can read about the theoretical build, but the actual issues that come up during construction... One feels as if no one else has ever screwed up a guitar in this particular way. Am I such an incompetent luthier that noone has ever had this issue before? This type of thread really helps a new builder to feel that others also deal with such issues. Thanks, Dave. And thanks responders!

-mark lacoste
somewhere in the wilds of southern Oregon