tuning with Dampp-Chaser

[Don]

Hi Charles,

I do not install damppchaser systems without back covers or bottom
covers(for grands). The results are much better with them and the cost
particularly on an upright is minimal, both in terms of materials and
labor. Most upright soundboards have atleast one hole to the back. If a
back cover is used both sides of the sound board tend to be exposed to the
same levels of humidity, and drafts don't dry out the board. On average I
find upgrights with back covers about 4 times more stable than without them.

R.H. and temperature are inverse relationships. As temperature drops R.H.
rises in a closed system. If R.H. rises then the moisture content of wood
goes up which causes it to swell and will most assuredly "smear" your
unisons very quickly. Next your octaves will start to be wobbly as the
plain strung tenor rises. Due to over stringing the first string on the
bass bridge (not A0) will probably be the most stable. Unfortunately as you
ascend the scale the plain steel on the treble bridge is the least stable.

At 12:09 AM 3/24/02 -0500, you wrote:
>Don, and list,
>
>It sounds like you support the idea of using a back cover for a vertical.
>Dampp-Chaser seems to market the back cover as part of a system where
>there are humidifer or dehumidifier elements behind the soundboard. But it
>would make sense that in any system, a back cover would help to keep
>humidity in during dry months. 

Regards,
Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.

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