One piece back vs. two piece back

[tnpathfinder]

I have search the threads for this topic and not found anything...please let me know if this has been covered.

If there any advantages or disadvantages of one piece back mandolins versus two piece backs? Is there a sound difference? Structural advantage? Just cosmetic?

[Bill Snyder]

Since you asked, it has been covered a few times now. I think the answer is no discernible tonal differences. Two piece backs are readily available so they are used more. Other than aesthetics the only advantage to a one piece back is the elimination of the glue joint which some would suggest is a structural advantage.

[Spruce]

"Since you asked, it has been covered a few times now. "

Yep...

Here's (http://www.mandolincafe.net/cgi-bin/ikonboard.cgi?act=ST;f=7;t=36242;hl=one+and+two+an d+piece+and+backs) one...

And another (http://www.mandolincafe.net/cgi-bin/ikonboard.cgi?act=ST;f=13;t=37513;hl=one+and+two+a nd+piece+and+backs)...

Yet another (http://www.mandolincafe.net/cgi-bin/ikonboard.cgi?act=ST;f=12;t=31411;hl=one+and+two+a nd+piece+and+backs)...

Oh, and here's (http://www.mandolincafe.net/cgi-bin/ikonboard.cgi?act=ST;f=12;t=29012;hl=one+and+two+a nd+piece+and+backs) one...

[tnpathfinder]

I just could not get that search function to pan out! This is what I was hoping for. Thanks!

[dunbarhamlin]

Building cylinderbacks (backs made with <.1" flat stock,) one piece backs would be nice (no worries heating the glue line during, or jointing the bent halves after bending)

For carved, I suppose using 2 piece backs (or tops) reduces the chance of finding unwelcome features (pitch pockets etc) in the material after hours of labour (you've already confirmed it's sound, at least sagitally)

Lets you get more of the finished skin on the quarter, and also pick and choose where to have the tighter grain (laterally for lutes, medially for mandos)

[whistler]

...the only advantage to a one piece back is the elimination of the glue joint which some would suggest is a structural advantage.

Bill - I had always believed the contrary. Using a bookmatched set for a back ensures near-perfect symmetry, both visual and structural. Also, a good glue joint should be stronger than the wood. Don't splits more often occur along the grain than along the join?

Or am I missing something

[Bill Snyder]

"which some would suggest". Look through the old threads and find the some I refered to and ask them.
Actually the only advantage I see was mentioned in some of the threads Bruce linked to and that is on occasion glue joints have been known to fail.

[Big Joe]

Back seams do come open and occasionally a top seam will. Eliminating the seam may eliminate the need for an open seam repair. However, the same issues that can cause a seam to open can cause a grain line to crack. If it is just old dried out glue there is not issue, but if it is due to humidity issues the one piece back is as likely to crack as the two piece is likely to open. Fortunately, that is not often the case. Usually it is the glue gives way with time on some two piece backs.