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More bend in the bar stores more spring energy, but does not apply any additional load. Once the bar reaches it's critical buckling load, the clamping pressure it applies is constant. For a 3/16" x 24" fiberglass bar, this point is reached with about 1" or less deflection and under 3/4" reduction in length. If you want to understand this, Google 'Euler theory column buckling ', or refer to any decent mechanics of materials text (Hibbeler, etc.).

Another consideration: for a constant diameter bar, the shorter one applies more pressure, so a 3/16" x 28" bar will exert a wimpy 5 lb clamping pressure or so, while the 24" bar will apply 7-8 lbs.

And finally - just because it will come up again - the clamping pressure is always, always, always applied along a straight line between the two ends, so a bar with ends aligned such that they are vertical will never apply any side forces to a brace or box, while a bar whose ends are not vertical will apply some degree of side force (a very handy thing, indeed).

I hear that Chuck Norris just stares at the top/back and they immediately clamp together, forming an airtight fit until the glue (which is actually Chuck Norris spit) holds fast in about 1-2 nano-seconds...

Too bad you can't play his guitars without them breaking your arms... unless, of course, you ARE Chuck Norris.


edited to say:
Really? That was my first post? Years of building guitars and browsing this and other forums, and my first post is a response to a (great) Chuck Norris joke? awesome...

I do it this way. This is the fasted method I've tried. I use hhg for the back and top so every second counts.