Klarinet Archive - Posting 000670.txt from 2001/04

From: "Dee D. Hays" <deehays@-----.net>
Subj: Re: [kl] Superglue and Beeswax
Date: Sat, 28 Apr 2001 08:27:51 -0400

----- Original Message -----
From: "CLARK FOBES " <reedman@-----.com>
Subject: [kl] Superglue and Beeswax

> ... Cracks occur because of different expansion rates at the bore and the
> surface of the clarinet. The most common cause of cracks is a blast of
warm
> air (breath) inot the bore when the instrument is extremely cold. The
> outside cannot expand as fast as the inside and the instrument will crack
at
> it weakest point. This is usually between the top two trill keys.

This simply isn't true. I've run the numbers and it's not the temperature
gradient. Wood has a strength of 1000 psi in its weakest direction and is
several times stronger in other directions. The amount of stress due to
thermal expansion if the outside of the horn is at 0°F and the inside is at
100°F is less than 100 psi, far below the amount required to crack the wood.
The exception would be if there is a pre-existing flaw that couldn't be seen
creating either an unusually weak spot or a stress riser. In these
instances, even bumping the instrument will break it if it's bumped in the
"right" direction.

Now humidity is another story entirely. Water cause extreme swelling of the
wood. Dryness can cause extreme shrinkage of the wood. Water has an
extreme expansion and contraction rate with temperature and has been known
to crack rocks.

Dee Hays
Michigan

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