Re: Determining balsa stiffness

From: Bruce McCrory <bruce_at_kbdmcc.net>
Date: Tue, 17 Jan 2006 07:35:11 -0000

--- In Indoor_Construction_at_yahoogroups.com, "John Kagan"
<john_kagan_at_h...> wrote:
>
> --- In Indoor_Construction_at_yahoogroups.com, "doctorgonzo788"
> <doctorgonzo788_at_y...> wrote:
> > Does anyone have a method (however scientific or unscientific) for
> > finding the stiffness of really thin c-grain?
>
> Here's what works for me:
>
> I first grade the sheets, relatively vaguely, by thickness and
weight.
> Then I simply hold the sheets near the middle and compare the flex.
>
> I don't necessarily choose the stiffest sheets, by the way. For my
> current F1D sticks I've been choosing sheets with more flex -
partly by
> using lighter sheets and partly with weaker sheets.

John, can you expand on the purpose for doing this?

Chris, I compare "sag" by holding either the end or some point along
the length of two sheets at a time. It is a process of elimination.
You need a pile of sheets in each relative density and nearly matched
thickness range to get anything meaningful. Of a 10 sheet stack only
one had a good H---n compared to the rest; and it performed pretty
well against the other size/density stacks.

Gitlow and Tagliafico feel the sheets. Gitlow also taps them.
Luthiers have resonance tests done on wood for string instrument
building, so I think there may be some merit. Lew has pounded on a
lot of wood, however.

How's that for being scientifically unscientific?

Bruce

 
Received on Mon Jan 16 2006 - 23:36:23 CET