> I know that someone has done the math on this. How much "spread" is >required of a rib that is 20 inches long, curved on a radius of say 40' to >allow the center to drop .020"??? It has been too long since I dragged my >kids through high school geometry to remember arc and such, but I know >somebody out there has the answer at hand. A 20" rib with a 40' crown radius has a crown height of 0.104". The measurement across the top of the rib, along the curve is about 20.0015", or just about 1.5 thousandths of an inch difference. Roughly half the diameter of a human hair. A 36" rib with a 40' radius crown has a crown height of 0.338, and a rib length to arc length difference of 0.008. Ron N
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