just dropping in

[jmuller92]

hey all, back again, hows everyone been?

Guitars going soundly, will try and attach a few photos. Was set back a bit over a month though as i broke my hand, so am going into the workshop alot more often to get it finished.

Im up to bracing the back, and want to use the same simple method i did to curve the x braces on the soundboard; which was to hammer in two nails at the length of the brace, and place a nail in the middle offset a few millimetres, then curve a thin piece of timber between them to get my curved line to transfer onto the brace. Using this principle, i was wondering how much i would offset it for the back braces? and whether i could use the same curve for different length braces on the back?

cheers

[Lillian]

Looking good Josh. Its come along nicely. Lots to be proud of there.

[vandenboom]

.... how much i would offset it for the back braces? and whether i could use the same curve for different length braces on the back?

Josh - I have just dug out the Cumpiano book, as he uses this method.
For back braces on steel string, he uses 1/4" offset over a span of 16" for all of them.
I presume you are not using a radius dish?
If you aren't there are a few things to think about in fitting the back that depend on the side profile you adopt. Can you tell us what you have in mind for this?
Cumpiano talks about a dimple you can get in the head block region due to a type of clash between the lateral and longitudinal arches that is dealt with by a bit of extra planing of the sides in the right places.
If you don't already have the Cumpiano book, it is is pretty popular in local libraries and could be worth looking out for this.
Frank

[jmuller92]

Its Jake everyone

Yes i have the cumpiano book, must have missed the bit about the 1/4 inch offset.

The side profile tapers towards the headblock, in which the headblock follows the same taper.

Dont have acces to a radius dish, with the soundboard i only arched the x braces which worked for me, by making a curve template, transferring the line onto the brace and planing it down to the line. But i obviously plan to arch all the back braces. Do you think this'll work for me?

[Lillian]

Sorry, my fault. I'm not my best at 4 am with 5 hours of interrupted sleep.

[kiwigeo]

I use a 15' radius dish for the backs on my classicals and steel strings.

You can work without a dish but its a P in the A and when you do get yourself some dishes youll wonder how you did without the things. They might seem a bit pricey if you buy them in but theyre going to last you a lifetime.

[vandenboom]

Its Jake everyone

Yes i have the cumpiano book, must have missed the bit about the 1/4 inch offset.

It is definitely workable as your approach is along Cumpiano lines.
See Pg 150 of Cumpiano for brace arching info. On Pg 231, he has an important section titled "removing the headblock discontinuity" which is the bit I was referring earlier - if you don't attend to it, you can get a noticeable dimple in this region, plus the back will not make full contact with the headblock.
Frank