flat sawn as a top?

ive been reading and enjoying the read on the guiter building forums about this.
from what I understand, quarter sawn is recommended for tops and everything else because of there stability strength .

but could you use a flat sawn top for a ukulele or guitar? what problems will you encounter during the build? bridge ripping of in time. the longevity of the top 50 years from now? prone to cracking easier due to weather?

ive read that all quilted wood are flatsawn. and so is Brazillion rosewood back and sides. what other beautiful woods a flat sawn and used.

My first Bruceweiart ukulele has a top that so far from quarter sawn that its getting somewhere near flat sawn in some area's. Its a stunning sounding instrument. Its been quite stable too.

Anthony

This one has a flat sawn top...And it turned out to be a gudun

Flat sawn is actually a little siffer, but quarter sawn is more stable, shrinks less and is less prone to cracks due to lack of moisture.

Timbuck said:

This one has a flat sawn top...And it turned out to be a gudun

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I guess its all in the builder on stuff like this.

I recently had an 8 string with a top almost exactly like that. Bridge ripped off 3 times; the wood kept failing, making it more difficult by the time I got it to get a good gluing surface. My suggestion to the owner was to string it as a 4, since the top was already bowed.

But, the owner valued it for sentimental reasons, and liked the 8 string sound. Too bad, she doesn't know what a good 8 string, much less a good instrument should sound and play like. This wasn't one of them.

I told her it'll happen again, and reminded her its not the glue joint that's failing.

Flatsawn wood usually moves about twice as much when the humidity changes, so you can expect more trouble with cracks, action change, popped glue joints, etc. Honduran mahogany is an exception to this rule, and has almost equal expansion in either direction.

With softwoods, the cross grain stiffness is maximum at either perfectly quartered or perfectly flatsawn, and minimum at 45 degree riftsawn. So unless your piece is flatsawn across its whole width (i.e. cut from pretty far out from the center of a large log), then there will be a lot of variation in cross grain stiffness across the width of it. Not that that's guaranteed to be a bad thing.

So... I'd only recommend flatsawn Honduran mahogany. But I also think there's some room for experimentation with riftsawn softwoods (especially cedar and redwood, which have lower humidity expansion than spruce), since traditional fan bracing adds a lot of long grain stiffness but not much cross grain. So a thicker riftsawn top without fan braces should theoretically produce a similar stiffness distribution, though a bit heavier.

I came across some flatsawn old growth Doug fir on the internet for sale that was very interesting looking with nice wavy figure, but I thought, that's a little crazy and has got to be unstable. But I suppose it could work if it was stable old growth and well seasoned. Pretty stuff though and maybe Doug fir is an unappreciated tonewood. Around here we won't even burn it. Poor firewood. Also I know that some of the cheap Asian "spruce" topped ukuleles are actually fir instead of spruce.

Dennis, could you explain the subtleties of "riftsawn" please. I think people would be interested. I'm thinking that maybe the fir I saw wasn't really flatsawn but maybe ristsawn.

The terms aren't strictly defined, but the way I use them is,
Quartersawn: Vertical endgrain lines, like this ||||||||||
Riftsawn: Diagonal endgrain lines, like this ////////
Flatsawn: Horizontal endgrain lines, like this =======

But perfectly flatsawn is rare to see in anything more than an inch or two wide, due to the fact that the lines are actually curved (because trees are round). So in guitar backs, flatsawn is usually more like ||//==\\||

And riftsawn is often like |||/////, and in back/sides (especially expensive species), is often called quartersawn since the terms are loosely defined.

But in softwood soundboards, quartersawn usually means perfectly vertical grain, or very close to it, due to the cross grain stiffness thing... which by the way, is due to the fact that softwoods have square cells, whereas hardwoods have round cells. When the squares are aligned diagonally in a thin board, they can easily deform into elongated diamonds, hence the low stiffness. When you get to perfectly flatsawn, they're back aligned as squares again, and similar stiffness to quartersawn (usually even a little stiffer).

maybe Doug fir is an unappreciated tonewood

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I believe that Italian guitars from the 70's (eg Eko) used Douglas fir for tops. From memory they sounded OK but not as good as the Martins or Gibsons.
Miguel

maybe Doug fir is an unappreciated tonewood

I would have to disagree we have built several Tenors with Doug Fir tops and they sounded wonderful. The Doug fir we use is very tight grain and quart sawn