Official Luthiers Forum!

Hello to all and long overdue introductions. I've been a lurker here for many months with only a few posts and I'm grateful for all the things I've learned through all of your most generous sharing. I'm currently tooling up to build my first guitar and with the help of Lance, Robbie O'Brien, John Hall and others I'm well on my way with forms, molds, plans, jigs, etc.

My next group of projects include sanding bars, solera and radius dishes. I've put together a spreadsheet to assist me in these efforts and I thought that I'd share it. I'm sure that there are many others that are available and most of them better. I've tried to add not only the included segment length (the depth of the dish) at the center of the input radius but also the length of the included segment at any distance from center, once the initial radius has been entered.

For example; if you want the depth (segment length) at center for a 25 ft. radius circle and you have a lower bout width of 14.875", you would enter 300" as the radius and then 14.875" as Chord length "c".

The answers are calculated in cells F28 & F29 with F28 being the segment length. In cell F29 the length of any segment at any distance from center can also be calculated once the initial radius and segment length have been input. This is handy for those of us who are trying to construct a curve by connecting the points. I'm going to try and attach both a screen-shot and the Excel file to this post and I do hope it will be of value. It could also be used for fretboard radiusing.



2006-03-22_175542_Segment_and_Chord_analysis.xls

I've got about 2 more years before I retire (at 62) and I'm hoping to at least learn a bit about this wonderful avocation to enable me to build a few guitars not only for myself but for a few friends and relatives, my children and soon to come (first coming in October) grandchildren.

Pete Liccardello
Troy, MichiganPeter J38799.314375

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Peter

Hi Peter -- this is the first post I've seen from you - so a belated welcome!

That's a handy spreadsheet!

Nice mathing.

Al

Welcome to the OLF. Alot of us are new and this is a great place to learn from others mistakes as well as new ways of doing things. That is the mathematically correct way of doing this radius...but since I'm not a math major, I just post a pole out in my yard and measure 25' from the pole and at a 90 degree angle with a pencil at the other end, I draw the radius on a 2 boards.....After sanding the boards to that radius you can attach a router on a jig and center a dish underneath and route out your radius while turning the dish. Thanks for posting this because I don't think most people would have the patience(and maybe not the knowledge) to figure this out. Good work! Jeremy

MATH
    Isn't it wonderful.
john hall