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Back Thickness?

Posted: Fri Jul 14, 2017 10:52 pm
by Kbore
So I've finished the top but not yet attached. I'm moving to the back. Is there a starting " preferred" Thickness for a rosewood dreadnaught back? I thinned the outside 2-3" around the edges of the top with a block plane, by .010 - .015, only south/ below the sound hole, and it made a HUGE difference in the resonance. I can't find much on the Thickness of the back. It calipers around the edges at .106" thk. Do you "tune" or Thickness the back similarity to the top?

Re: Back Thickness?

Posted: Sat Jul 15, 2017 5:22 am
by Diane Kauffmds
I don't voice the back like I do the top, but I do make sure that it sounds different from the top, to avoid wolf notes.

I prefer a thickness of ~ .095-.100" for the back.

Re: Back Thickness?

Posted: Sat Jul 15, 2017 6:03 am
by MaineGeezer
I'd go with 0.095" or so as well. Maybe as little as 0.085" if you want to build light.

Re: Back Thickness?

Posted: Sat Jul 15, 2017 7:23 am
by Danl8
I agree with above. I have several Martin reject backs; all measure 0.109" (EIR). (Disclaimer-- Harbor Freight, not measured with Starrett.)

Re: Back Thickness?

Posted: Sat Jul 15, 2017 10:21 am
by Kbore
Thanks for sharing. I'll figure removing at least 0.010 harbor freight inches during sanding both sides so I'm gonna call it good. Kind of disappointed cause I'm Loving working on this guitar wood.

Re: Back Thickness?

Posted: Sun Jul 16, 2017 12:13 pm
by Kbore
Having moved onto the back, which method do the experienced members prefer for constructing the back plate: glue the braces first ( Stewmac's manual) or glue the center strip first (p. 225 of Cumpiano's guitarmaking...?

I moved to the top because the large tone bar above the sound hole is too dam short to extend to the kerfing. I will have to remove it and replce it. It came in the kit too short. . I knew it when I was preparing to glue it in place too. Should have called stew mac and asked for another. Guess you just chisel it off? Sorry for all the newbie questions in one post.

Re: Back Thickness?

Posted: Sun Jul 16, 2017 12:41 pm
by MaineGeezer
For the three guitars I've built, I've glued the plates, then glued the reinforcing strip down the inside, then turned it over and routed a channel for the back strip and glued that in. Then I've glued on the braces.

I guess some people glue the back strip in place between the plates when they glue the plates together. That will work as long as the back strip is as thick as the back.

It seems to me that the braces pretty much have to be the last thing you do.

If you are asking about doing the braces or the inside reinforcing strip first, I do the reinforcing stirp first and notch it for the braces. I know some people do the braces first and inset the reinforcing strip in pieces between them. I'm not sure makes much difference. It's probably easier to get the reinforcing strip in a straight lif you glue it first, then notch it.