Cutting rib radii

[Richard Brekne]

Good points to be sure. The problem can of course to some degree be 
countered by using much longer rib lengths then you will end up with, 
taking the end rib out of the middle section. This implies some waist... 
but just so. You can perhaps not get a perfect circle curve this way 
regardless, but you will get quite close enough me thinks.  As Ron 
points out... from the get go one can question if there is any 
functional difference in the first place.  Indeed... lots of folks been 
doing it this way for a long time... and well... getting nicely away 
with the method as it were.

Still... if someone has (or finds) a jig that does the perfect circle 
with as much ease and as little expense... well very cool indeed.

Cheers
RicB


    Farrell wrote:

     > I think "radii" implies a circle or an arc thereof. If you apply
     > pressure to the mid-point of a board (or rib), the end portions
    will be
     > near straight and the center area will have the most curve. Yes,
    you can
     > produce the target "crown" measurement in the middle, but the
    shape of
     > the curve will not be an arc.

        No, it won't, and I haven't been able to find any source that
        names that curve. It's not a parabola, and not a catenary,
        though the middle section of the curve is similar to either.
        Nearest I can determine, it seems to most closely be a sine curve.

     > I guess then, the question might be: what shape rib is optimal?
     >
     > Terry Farrell

        Or if there's any detectable functional difference at all.
        Ron N