> Are we saying the same thing in a different language? ie. A one inch > square rib until the taper begins?. Then it becomes ...tapered? > Dale Almost. Crowned top, flat bottom, taper feathering. I cut 'em to depth on a table saw, so the thickest part is in the middle. I make no attempt to keep the section depth constant through the center, and would prefer not to even if I could easily do it. They're a taper of one sort or another from the center point to just inside where they meet the rim. I want them to bend as uniformly as possible, like a bow, so stress is evenly distributed and vibration response is from the whole rib (and membrane) at once. At least, that's the intent. Make a 1/3-1/3-1/3 taper-straight-taper test rib, and another of the same dimensions with conventional tapering. Support the ends and load the center. The taper feathered rib forms a nice smooth continuous arc, or if it was constant radius crowned to begin with, it deflects to a nearly straight line under the right load. The conventionally feathered rib shows a tight bend in the feathered sections, a relatively straight run, and a relatively tight bend in the center where the load is. The tight bends are the high stress areas. while the relatively straight sections aren't responding like they could. The conventional rib shape just wasn't very well designed as a load bearing member, which is why I use the shape I do. It does what I think I want it to do. If I had an easy way to do it, I'd probably crown the bottom of the rib too, but the taper is easy and quick with a router jig, even though it buries me in chips, and works pretty well. Ron N
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