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Re: playing in hot weather

Author: wrowand
Date: 2006-07-23 20:30

vboboe,
You wrote:
>>Seems worthwhile commenting here that the diameter of post-holes is small (somebody else please provide size & do the math, don't have time to research it just now) and 0.06% metal expansion over 30 degree temp range in that small space would equal what ***percentage*** expansion in the post-hole? <<

I don't mean to belabor this point, but I already *did* the math. It's in the quote above. 30 degrees multiplied by 0.00002 is 0.06%, that is, six hundredths of a percent. That's the ***percentage*** expansion due to a 30 degree temperature change.

If you want to know the absolute change (not the percentage)... on a Loree oboe, the portion of the post screwed into the wood is 3.5mm wide at its widest point. Therefore a change in temperature of 30 degC results in a change of (0.0006 * 3.5mm) = 0.0021mm or about 2 micrometers. I don't think the tolerances are so tight on the post holes that you need to worry about an imagined problem if cracks caused by thermal changes. Better to worry about the *actual* problem of the wood shrinking and expanding due to changes in humidity.

Wood swells and contracts readily with changes in humidity, the percentage changes are on the order of 0.5 percent per percent change in moisture content of the wood. At least that's what I found on the web for rosewood which is in the family of woods used for making oboes. Moisture differentials across the wood, for example when the interior of the oboe is moist and the exterior is dry can put enough internal stress on the wood to cause cracks on the exterior surface. I think this is particularly bad when playing in a cold room since the relative humidity drops when the air is cold, but the breath you put into the oboe is moist.

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lucyw

2006-07-22 00:09