Re: wing spars witc C grain at front?

From: hbmccrory <mccrory.hb_at_gmail.com>
Date: Wed, 11 May 2011 02:21:10 -0000

I think strength and stiffness is based on a measurement of the force exerted to deflect--and direction of deflection--of columns or beams of equivalent mass. Since no contiguous cuts want to be identical twins, I usually strip a dozen, or so, spars and marry the "close" ones.

Grain, or ray orientation never seems to affect strength or stiffness, so my stripping is always based on the thickness of the source sheet. (Normally, Egyptian cotton...)

However, member depth outside of square always influences comparative deflection resistance, ie., it's a beam, or spring board; and the taper (either way) can really add to the thrill of deflection when the piece is loaded.

The only time grain direction consistently impacts my construction considerations is in carving propellers; and rolling tubes. And, some builders have contested even those comfort standards with good logic and construction examples.

Good flying and building,
Bruce in Seattle
Received on Tue May 10 2011 - 19:21:17 CEST