Mathematical Methods for Creating Radii

[Stephen Johnson]

I created a spreadsheet a few years back to do this. I figured it out from "first principles" similar to some of the discussion above. I haven't used it in a few years. I believe it works correctly, but never fully tested it. Will supply free, "as is", with NO support. Contact stephenpjohnson@verizon.net if interested.

[Rodger Knox]

Louie, your equations are correct, as are mine. Your initial value of S=0.6015 is the same value as the tangent/offset for a 12" length and 120" radius. I'll admit that I'm a little lazy when it comes to math, I like simple. I "build" all kinds of statistical and mathematical models as a civil engineer, from how water falls out of the sky and runs downhill to representations of physical objects, so anytime I can simplify the math it's a plus.
Where did I have a + under the squareroot?
Usually rounding off to 4 decimals will maintain 3 decimal accuracy, but multiplying a "small" number (the trig function) by a "large" number (the radius) can compound the error in the small number pretty significantly.

[Louie Atienza]

I made the error, at the wee hours of the morning... Surprisingly it didn't make much difference since x is very small relative to r.

[MortUK]

Found this online

Radius Calulator for Luthiers

by Artak Kalantarian

http://kalantarian.org/artak/gm/depthcalc.htm

[Greg Robinson]

Hi MortUK,
Please note that we require the use of real full names (first and last) on this forum, and do not accept aliases or "handles". Please let us know your name so we can update your registration.

Thanks.