Why no center seam brace on the M-20

http://guildguitars.com/g/m-20-in-natural/

Some one asked in the AGF, and I had never looked that close. Is the brace the runs top to bottom on the back if the guitar only needed if it's a two piece back, and the M-20, being small and mahogany a single piece ?

John

Yes, if it's a one piece back, there's no need for a center strip. (Similarly, if a guitar has a three piece back, it will need two.)

That is a good question.
I'd be surprised if it's one piece, that would have required larger and thus more expensive slabs to make the backs.
I think it's more likely that it's small enough that the additional center brace isn't necessary, the cross braces are enough to keep the pieces securely butted and flat.
Sure would like to have one in hand to see for sure. Can't really tell from the pic on the website.
Ah, I see Chris posted while I was composing.
Thanks!
Oh waitaminnit, I read too fast.
I though he said it was a one-piece, but he only confirmed IF it was, it wouldn't need the centerstrip.
Can they also get away without one if it's small enough?

some of the older Hoboken M-20s and F20s have one-piece backs, and no center brace going north/south on the inside of the back. many, or most, have the 2-piece back, along with the center brace.

Not sure about the new Oxnard crop. it does appear from photos they are one-piece like you are observing. I'll check one out again in Sam Ash soon.

Those are nice guitars. Oxnard made Guilds are still working on an identity of their own. Still earning the respect of the hard-cores, and working out some growing pains and kinks. But those M-20s are nice players and the tone of the M-20 is there. Apparently they did not do a good job of disclosing the construction methods on this maiden voyage for Oxnard model, and the set neck is actually also bolted on the inside. But i've played this guitar, and it is a nice M-20 that really does nail the sound. the 1 3/4" nut width is a debut for this model and is a nice option to now have in the mix of M-20s. If they have one-piece backs, im not sure "which variation of mahogany" that might be, and it doesn't really change the tone but that is definitely super cool if that is the case, and I thank you for pointing that out!

Remember the M-20 was always a cheap, student, beginner, even child's instrument, that sounded incredible for what it was. They have also been using the same, or similar, "variations of mahogany" since back in the 60s-70s, that they do today. I think the current M-20 is solid for what it is, definitely gets the job done. There have been some reports of duds or blems but all guitars have that from all guitar makers.

I'd say the one piece backs just need horizontal bracing if they're solid wood. The center strip is mainly stability for the bookmatched joint. Now in the ARCHED backs, there is no bracing at all because the strength comes from the shape of the arch and the lamination process, and therefore it doesn't need bracing. That's my mind working as well as it does at this time. Someone will probably prove me wrong.......

I've seen many models from Martin, Larrivee, and others that have two-piece backs without center-strip bracing, including a solid mahogany bodied Martin that I own.

It's actually a rather common practice.