Back Thickness question

thebolo · #1 02-28-2011, 04:44 PM

Hello everyone,

Got a question. I am currently building a guitar. You can see the build thread in Build/Repair. It is the Curly Maple Dred. Anyways...

I was thicknessing the back with the new sander. I got a tiny bit carried away...I was aiming for about 0.10 and it ended up at around 0.090. That is only ten thousadnths difference. Will this make my guitar structurally weaker? If not will it cause any other problems? Thanks for the time.

JohnM · #2 02-28-2011, 04:45 PM

I wouldn't use a back that is .100 thick finished. I shoot for less than your .090 figure too. But to answer the questions... you'll be fine. Build away.

Brackett Instruments · #3 02-28-2011, 04:51 PM

Most (or all?)of my backs are thinner than .090", but I don't pay much attention to the actual measurement. I thickness by flexing, feeling, and listening. There's a point where the feel, as well as the tap tone changes with just a few thou. That's the point I'm looking for with my backs. I wish I could do a better job explaining.

thebolo · #4 02-28-2011, 06:58 PM

This is only the second guitar I've built from scratch, so I'm not sure what to feel and listen for yet. I didnt think it would be a huge problem, but thought I'd ask anyways. The guitar I did before this, the back was just about 0.10 and it sounds really good. Of course I'm using different types of wood this time and I'm better than I was at building.

What techniques do you use to tell when the top is ready? I know thats hard to answer but it wont stop me from asking

Thanks for the response

thebolo · #5 02-28-2011, 07:01 PM

one more thing...

What about side thickness? In Cumpiano's book he says 0.85. Thats what I aim for. What affect does side thickness have on sound?

Tim McKnight · #6 03-01-2011, 08:04 AM

Quote:

Originally Posted by thebolo

one more thing... What affect does side thickness have on sound?

Very little. IMO the sides are one of the least contributors to sound and are more of a structural element.

Just to add to your back question... thicker, stiffer backs [can] give more forward projection. Thinner or more flexible backs [can] actively couple more efficiently with the top's movement via the sound box's air column.

Bruce Sexauer · #7 03-01-2011, 09:48 AM

Big Leaf can get down into the mid-70s before it's unrecoverable IMO, though it varies from piece to piece, of course. Either use.

thebolo · #8 03-01-2011, 10:16 AM

Quote:

Just to add to your back question... thicker, stiffer backs [can] give more forward projection. Thinner or more flexible backs [can] actively couple more efficiently with the top's movement via the sound box's air column.

That makes sense. My previous guitar has a lot of projection.

How thin can the sides be before they get structurally weak?

Once again, thanks for all the answers

Matt Mustapick · #9 03-01-2011, 10:25 AM

I say keep building it at .090, but take care now to sand as little off as possible. I generally keep my backs in the .110 region, closer to .100 for cocobolo and such.

thebolo · #10 03-01-2011, 11:43 AM

Quote:

I say keep building it at .090, but take care now to sand as little off as possible. I generally keep my backs in the .110 region, closer to .100 for cocobolo and such

It is sanded to 220 and I only have a little finish sanding to go, so it shouldnt get thinned out to much more