Official Luthiers Forum!

[QUOTE=JBreault]Michael you are spot on. It is Lee Valley and only $8.50 for a set of five. Not bad.
[/QUOTE]
Hah! I bet they didn't even know they were making the perfect tool for the "Symonds Scribe!"

Y'know, I've never bothered with this because I figured it would be too much work, and each guitar I've built (and got planned) is slightly different, but this is so genially simple I may have to give it a shot...

Wow, what a great tip!! What took me so long to read this post??

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

colin,
i love the tip. my question has to do with the neck and tail blocks. i assume you glue them in before sanding the rim with the dish. do you have a jig to get the right shape onto the ends of those blocks before gluing them to the rims? if you do, i imagine you would have to be nearly dead on when gluing those blocks into place.
my own method has been rather barbaric. i've glued the blocks onto the rims, centered the mold and rim above a block that holds a 1/4" dowel, then dropped my dish over the dowel (the center of the dish has a 1/4" hole), and rotated the thing until the rims and the blocks all have the perfect profile. i then glue the kerfing on a hair proud and sand again. takes a bit of spinning and vacuuming dust away, but it comes out dead on. it's also pretty forgiving as far as the gluing of the blocks is concerned. i'm considering making a motorized spinner for the dish because i think with a little speed and 60 grit, the whole business could be done in about a minute (albeit in a cloud of rosewood if i wouldn't also look after dust collection).
if you've got as good a solution for the blocks as you have for copying the profile, though, you might save me a bunch of time on each guitar.
phil

Colin--

Great tip! Thanks very much for the explanation and the photos. This is something that I have been curious about for a while now.

--Jim

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Jim Howell
Charlotte, NC

Great tip!

I see how this would work wonderfully if the sanding disc is the only radiused taper on the box and the sides are fairly identical in width; but how would this work with some more complex?

My first project is this ABG project based on the Taylor AB-1 and it has a tapered profile top to bottom, as well as headpiece to tail piece. Looking at the bass from the tail in profile the sides are more narrow on the top (near the player) than the bottom (towards the feet) so the front and bakc plates are not parallel by design (if two domes could be parallel but you know what I mean).

I am thinking to approximate the design of the Taylor AB1 I will have to due some profile cutting before the sides are brough to the sanding disc/go bar domes.

Scooter: you're referring to a Manzer-style Wedge (also used by Bill Cumpiano), methinks. If you use wider tape with this, and prop up the mold to deal with the side to side and lengthwise taper, I don't see why it couldn't be adapted for a wedge. Bit fiddlier, maybe not quite worth it, but still.

One more question for Collin and others. I’m one of the newer builders referenced and am trying to understand this. You mention connecting your side profile line from the head block height line to the tail block height line. Wouldn’t this produce a continuous taper from top to bottom? The Cumpiano book (p.213) indicates tapering a section from the head block to a point two inches (2”) beyond the waist (the peak).

So, do most of you taper from end to end or from the head block to the “peak”? Or does the “final arching” steps described in the Cumpiano book result in a more or less continuous taper from end to end anyway?

Since the back plate is arched in only one direction (laterally) by the back braces, I assume it does not initially lie flat against the sides and is arched longitudinally only once it is pulled down tight to the side profiles during the back plate attachment process?

Sorry for the many questions but I am trying to get my hands around the back/side geometry relationship.

thanks

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Doug Mills
Chicago, Illinois

Two approaches, most here, including myself, don't use the Cumpiano style taper, just have a continuous taper on the back from tail to head, usually finally sanded in with the dish. A Cumpiano style taper can be put onto the template as Mattia explains by drawing one half and then propping the mould to do the other half, Remember though that Cumpiano was using a system designed for the builder with few tools and jigs. Most now build with moulds and dishes.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

This place just cracks me up. Every time I think I have thought through a process and settle on the best, someone comes along and shows me how little I know!
Thanks Colin.
Now I'll go back into my shop and think about the next worrisome process, knowing that someone, somewhere is making my life a little simpler.....just have to await the posting.

Tom Armstrong

What Colin Said: define depth at the tail and at the heel, and let the radius dish take care of the rest of the shaping and arching.

I used Colin's method to make a new side template yesterday. Worked great! The only thing I did differently was use a carpenter's scribe instead of a block with a pencil in it.

Thanks again Colin!

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Dave Rector
Rector Guitars

Colin,
After seeing your method and seeing the results you get, I only have one chose. I'm going to have to break down and buy a set of radius dishes!

Good stuff Thank you.

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Joe Beaver
Maker of Sawdust

Mattia how are you? Have seen you online in a bit. Last we heard you were setting up a new shop and busy with your internship. Hope all is well.

[QUOTE=Anthony Z] Mattia how are you? Have seen you online in a bit. Last we heard you were setting up a new shop and busy with your internship. Hope all is well.[/QUOTE]

Doing good...been on vacation for almost 3 weeks, progress on the shop is slow, and internships are looming (they begin on the 11th of next month). I'm hoping to get the shop to the point where it's ready to use before I start seeing patients, but we'll just have to wait and see. I'm going to try finishing up three guitars before then (all need final detailing and trim, little else).

Colin,

Thanks for the clarification. This thread has now cleared up two big question marks for me - how to establish the side profiles without an existing template and how to handle the side taper for the back plane.

So when are one of you guys going to take the baton from C&N and write the updated guitar construction manual for the 21st cent?

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Doug Mills
Chicago, Illinois

[QUOTE=Dave Rector] I used Colin's method to make a new side template yesterday. Worked great! The only thing I did differently was use a carpenter's scribe instead of a block with a pencil in it.

Thanks again Colin![/QUOTE]

Glad it worked Dave.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.