"Tim Ward" wrote in message
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"Bill Daniels" wrote in message
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"Bill Daniels" wrote in message
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"Mike Borgelt" wrote in message
Vacuum.
Use a glass wall vacuum flask. Fill with copper pot scourers.
See Reichmann for a complete explanation of why this is a good idea.
Mike Borgelt
I agree, but I can't find a source of half liter glass vacuum flasks.
The
consumer variety are stainless steel these days.
Bill Daniels
I just fat fingered the delete of a post from Tim Ward (I think) with
some
links to 1 Pt. glass vacuum bottles. Anyway thanks for the links.
As for the stainless steel vacuum, bottles, I had tested them way back
on
another project involving liquid nitrogen and they were far inferior to
the
glass bottles. The LN2 would evaporate from the stainless ones three
times
faster than from the glass dewars. On the other hand, they were a lot
more
rugged.
Bill Daniels
Yep, it was me.
I just Googled for "vacuum bottle" glass pint
A factor of 3 does seem significantly faster.
On a slightly different subject, I keep seing references to "Chore Girl"
copper scrubbers, and yet all I can find to buy is "Chore Boy" copper
scrubbers.
It's not that I think the name will make a difference, but it makes me
wonder when the name changed and why.
Tim Ward
Thanks Tim. I did the same thing with Google and never came up with your
sites. I'm starting to wonder about Google.
I now have a glass 0.45 liter vacuum bottle with two copper scrub pads in
it. I repeated the solar heating test with the glass bottle and there was
no detectable change in the vario reading after one hour in the sun. I also
bought a pint stainless steel flask and it failed the test almost as badly
as the plastic one I tested yesterday. A glass vacuum flask is the way to
go.
"Chore Boy vs. "Chore Girl" it's probably just more annoying "Political
Correctness". I think copper wool is pretty much the same no matter what
the name. A lot of the same stuff is sold as a rust proof pest barrier in
hardware stores. All you are asking it to do is add some heat sink without
contaminating the vario system.
Now for the next test. I want to determine the vario system time constant.
(The vario experts on this forum are welcome to jump in here.)
The experiment I have in mind is to inject a calibrated amount of air into
the capacity side of the vario with a tiny medical syringe such that it
produces a half scale up reading on the vario. Then I will record the time
it takes for the vario reading to decay to half that value. (Is there a
standard for measuring vario lag?) I guess I could also suck out the same
amount of air and make the experiment symmetrical.
The reason for my curiosity is a flight in December at Warner Springs, CA.
There was some ridge lift mixed with weak thermals. Because the inversion
layer was just about at the level of the mountain peaks, I spent most of the
flight working lift very near the slopes. When encountering a thermal, I
could feel the glider surge and see myself climbing relative to the nearby
slopes. Neither vario showed any indication for about three seconds after
encountering the lift. That seems way too slow to me. It would be nice to
get the response down to one second.
Bill Daniels
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