Which is stiffer -

[hilo_kawika]

Quartersawn or slabsawn wood from the same board?

Actually, they appear to have the same inherent stiffness!

Some time ago I was looking into the stiffness properties of several types of wood for their use as go-bar material. The wood was cut into 2' lengths which were 1/4" square in cross-section. In all cases, I tried to make one orientation as quartersawn as possible with no runout.

I then placed each wood strip across a pair of wooden bars, hung a weight in the middle and measured the deflection. The strip was rotated 90 degrees around the long axis and the deflection with the same weight measured again. So now we have measurements of quartersawn and slabsawn deflections for the same piece of wood. Using standard equations, I then calculated the Young's modulus (modulus of elasticity) for each piece in both the quartersawn and slabsawn directions. The figure below shows the results.



The solid line shows the slope of a 1:1 line. In the case I have described above, because the quartersawn and slabsawn direction dimensions are the same, I could as easily have plotted the actual deflections in each direction and gotten the same results. I didn't do this at the time because I was after the elasticities rather than the deflections.

Your thoughts?

aloha,

Dave Hurd
http://www.ukuleles.com

[jeffhigh]

Yes David, at some stage I have seen results suggesting that for harder woods such as maple, flatsawn orientation is slightly stiffer in bending.
And Fender necks are almost always flatsawn.
There are many good reasons why we tend to use quartersawn woods, but bending stiffness is not a valid one.
Jeff

[Taffy Evans]

Thanks Dave, thats as clear as mud to me, I new I should had done more at school than woodwork. But I get your message. I had alway cut my maple [Fender style] necks on the 1/4 for years. Then I had to re-order and could only get Maple neck blanks and these were slab cut. I complained and thats when I found out what you mentioned above.

[hilo_kawika]

There are many good reasons why we tend to use quartersawn woods, but bending stiffness is not a valid one.
Jeff

Jeff, I'm not suggesting that we make all tops flatsawn rather than quartersawn but rather that this observation was simply an interesting one and perhaps counterintuitive to some readers! And further, it's a concept that's easy to test for oneself.

Geez, lighten up a little...

aloha,

Dave Hurd
http://www.ukuleles.com

[graham mcdonald]

There have been a few similar tests done over the years, especially in relation to soundboard braces. American Lutherie has had a couple I think. From memory the main advantage of using vertical grain timber for braces was getting a better glue join!

cheers

[jeffhigh]

[quote="hilo_kawika
Jeff, I'm not suggesting that we make all tops flatsawn rather than quartersawn but rather that this observation was simply an interesting one and perhaps counterintuitive to some readers! And further, it's a concept that's easy to test for oneself.

Geez, lighten up a little...

aloha,

Dave Hurd
http://www.ukuleles.com[/quote]

I know you are not suggesting flatsawn tops David, I am only saying that we should be making intelligent decisions on grain direction for the varying components on an instrument based on such considerations as stability (radially versus tangentially)workability, crack resistance etc and not on slavishly insisting on quartersawn wood for everything (because it's stiffer) when it has been proved otherwise.
Ok I'm feeling pretty light right now thanks
regards
Jeff