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Form Setup - Quads

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Does anyone  have the math for setting quad forms, using drill rods?

Also, in using the drill rod method as described on Chris Bogart's site, you must subtract the depth of the forms (at a given station) from the height of the rod in the form (at that station). Shouldn't you be able to just measure the height of the drill rod above the form and compute the depth of the groove from that number, and the diameter of the drill rod?

I know, it shouldn't be that simple.    We build cane rods.  (Mike Canazon)

Here is the formula from the wonderful book by George Barnes, Fly Rods Galore. I believe it was also credited to Ted Knott from an earlier Planing Form article.

Six Sided AE = 1.5D - M
Five Side AE = 1.3507D - 0.8507M
Four Sided AE = (1.7071D - M) 0.7071

AE= the desired strip dimension
D= diameter of the drill bit being used (you need several)
M= projecting height above the form.

I hope this helps. My head is hurting from even thinking about all the math! Art, help me out here!  (Bob Maulucci)