RC vs CC again

Delwin D Fandrich pianobuilders@olynet.com
Thu, 2 Oct 2003 10:13:56 -0700


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----- Original Message -----=20
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: "Pianotech" <pianotech@ptg.org>
Sent: October 02, 2003 8:33 AM
Subject: Re: RC vs CC again


>=20
> All of this suggests to me that in general, a CC board has an easier
> time generating a higher stiffness to mass ratio...as long as the
> compression in the panel holds. Yes ?
>=20
> RicB=20
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No.

Remember the stiffness of the ribs increases directly with its width but =
with the cube of its height:




y =3D deflection of beam (measured at center)
K =3D a constant (0.25 for a center-loaded beam)

P =3D load on beam (at center)

E =3D modulus of elasticity (1.57 x 106 for Sitka spruce)

l =3D length of beam

b =3D width of beam

d =3D depth of beam


... and we get to manipulate both the height and the width of the rib. I =
can make that rib enormously stiff before I run into mass problems.

Del
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