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Author:  Pwoolson [ Wed Jan 12, 2005 3:09 am ]
Post subject: 
Ok all you math wizz-types. I need some help. I'm
trying to layout a side pattern (not a bending form) for
one of my guitars. Before I just left them tall and
sanded them down to height on my dished sander.
Well, that's a pain and I'd like to have the know how
to figure the exact shape prior to shaping.
Charles Fox once explained the process to me as
taking a 25' sphere and cutting it with a guitar
shaped cookie cutter. The areas closest to the apex
of the arc (waist) will be the tallest and the areas
furtherest away (lower bout, tail) will be teh most
shallow. But how do I put that into numbers? Thanks
in advance. Paul
Author:  Brock Poling [ Wed Jan 12, 2005 3:14 am ]
Post subject: 

You want to calculate it, not duplicate it?

I have duplicated side profiles of existing guitars by taking very low tack tape and covering a side, trimming it out carefully with a razor blade then removing the tape.

Transfer that to wood and presto. You are in business.

Worked like a champ.

Author:  John How [ Wed Jan 12, 2005 3:16 am ]
Post subject: 
I wouldn't begin to know the mathmatics involved and probably wouldn't trust them if I did but after you've built one you could certainly make a pattern by wraping it with paper and tracing the side. You could use you mold to hold the paper tight against the guitar.
Author:  Pwoolson [ Wed Jan 12, 2005 3:21 am ]
Post subject: 
I've done both of these methods. I just have this
wierd thing nagging at me that makes me think I
need to do it the mathmatical way.
Thanks for your responses. Paul
Author:  Dickey [ Wed Jan 12, 2005 3:29 am ]
Post subject: 
And then our own Michael Paine does something similar, see his architectural renderings for Lance. Michael, can you plot a side, lay it flat and print it out? Paul, you aren't the only one plagued with this question.

I used tin foil to wrap a six inch strip down the side of a completed guitar, make the impressions of all edges, remove and transfer to 1/8th inch tempered bath board. The finished product, you'd swear it couldn't be right looking at it. And, profiled, if you miss the waist by even a little in the bend, it won't be correct.

Better to do like McKenzie, remember his little tricornered scribing tool, marks the arch on the side of straight rimsets and gives the proper cut line. As accurate a method as I've seen. It's in the jigs section of the OLF.
Author:  LanceK [ Wed Jan 12, 2005 3:30 am ]
Post subject: 
Paul,
check out Mike Doolins article

HERE

This is pretty mathematical
Author:  Bobc [ Wed Jan 12, 2005 3:38 am ]
Post subject: 
I have used Mikes method and it works great.
Author:  Pwoolson [ Wed Jan 12, 2005 4:14 am ]
Post subject: 
Hey Lance, thanks for the tip. Mike's method was EXACTLY what I was looking for. I wrote him and requested a copy of his excel spreadsheet to check my math. With his permission, I'll post it here so all can share in the mathmatical fun. Thanks again. P
Author:  Brock Poling [ Wed Jan 12, 2005 5:07 am ]
Post subject: 

I certainly understand why this might be helpful if you are building an entirely new shape from scratch, but if not, is this an area where precision is all that critical?

Cutting the shape close on the band saw and then sanding the rims before you install the kerfed linings usually gets things right on....

Or am I missing something?
Author:  Bobc [ Wed Jan 12, 2005 5:23 am ]
Post subject: 
Brock your not missing a thing. I only use it for a new body shape. If I already have a guitar made I copy that on to poster board, cut out a pattern then make up a plywood jig with the contour on it. So next guitar I just put the sides on the jig oriented correctly and run thru my router table with a pattern cutting bit. I do make them a bit wider to allow for dish sanding.
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