Rib grain orientation

Ron Overs sec@overspianos.com.au
Sun, 8 Dec 2002 19:43:20 +1100


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At 11:52 PM -0500 7/12/02, Erwinspiano@aol.com wrote:

>                 Honestly I wonder if it matters. I cut up some tight 
>grain& dense old sugar pine stock from material gutted from a old 
>pipe organ. Some of the pieces took on a beautiful tight arc 
>appropriate for some tight radius treble ribs.

Sure, but I was wondering if we shouldn't be choosing to cut it with 
the rays vertical, if there is a choice, to gain the benefit of the 
slightly higher modulus of elasticity along the line of the ray.

>      If there was a slight stiffness difference it could be made up 
>in rib thickness.

True, but ideally aren't we trying to achieve the highest panel 
stiffness with the least weight?

>No big deal. Ask some one in our engineering dept. if the wood 
>strength formulas change for this slight change in orientation. 
>(that would be you).

Ron N's post confirmed that there is a minor though measurable 
improvement in strength along the line of the ray.

>. . Why would it be benificial to change the grain orientation to 
>have the ray run the other way.I don't follow this.


I put forward the question since I have a large slab of Sitka from 
which I will be cutting out the rib stock for piano 4. The board is 
of such a size that I have a choice of grain orientation. The 
question was intended to see if any others might be sharing my views 
on this matter.

I agree its a very small point, but sometimes its the minutiae we 
concern ourselves with. Following on from Ron N's post where he 
discussed the orientation of the rays in hammer shanks, he was saying 
that most makers don't seem to regard it as important. Indeed, I have 
tested hammer shanks for stiffness with and perpendicular to the ray 
and its only just measurable using a dial guage.

Ron O.
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