Finding TE "membrane" style compensators?

Wow, you all provided excellent information, thank you! I think I will
follow Bob's advice as my goal is a nicely working instrument and not
historical accuracy. The aircraft in question is 201B Libelle and I
believe the instrument was factory installed or at least purchased with the
Libelle polar in mind. The last thing I need is a diaphram blowout that
would affect both airspeed indicators.

The funny thing is that it appears it was plumbed to Bob's recommendations
prior to refitting the panel. I assumed that someone made a mistake
hooking things up after translating the labels on the back.

Happy Soaring!

Paul


"Bob Korves" bkorves@winfirstDECIMALcom wrote in message
. 85...
"Paul Adriance" wrote in
ink.net:

I have a Winter combination Airspeed/Vario/Speed-To-Fly instrument
that was designed to use a TE compensator between the capacity line &
the pitot line. My assumption is this was a standard type of device
prior to the common use of TE probes. Talking to some experienced
members of my club confirmed this and they described it as an inline
filter that had a membrane that would compensate for changes in pitot
pressure to the capacity flask.

Unfortunately, one of the previous owners of my glider misplaced or
lost the compensator and now that I'm redoing the plumbing, I want to
have it installed correctly per the manufacturer's suggestion.

Does anyone have these or make these anymore? A google search didn't
turn up much, and I don't see anything like this on Wings&Wheels or
the other common soaring product sites.

Any help would be appreciated,

Thanks!

Paul Adriance



Paul,
It sounds like you have a Winter Sohlfahrtgeber. I once had one in a Pik-
20d. It is possible to hook it up with very good results without the
diaphragm compensator.

IIRC, it will have 3 tubing connections on the back. There is only one
static connection for both halves (ASI and vario) of the instrument. Hook
up the total energy probe to the port marked "static" (this is actually
marked in German, something like "stat. druck"). Hook the port marked
"pitot" to the gliders' variometer static system. Hook the capacity up to
the port marked something like ".6 liter".

It sounds strange, but it works. If you hook it up like it says on the
case then the ASI will read too high -- you will have pitot at +1 and TE
at
-1 for a difference of 2. The ASI needs a. value of 1. So, instead you
use static at 0 on the pitot side and TE at -1 on the static side, giving
a difference of 1. This also gives you a back up ASI that does not rely
on
pitot. It also gives you a check of your TE system. If both ASI's agree
at all speeds then your TE is correct (neglecting port position errors and
instrument calibration issues).

There is a knob on the front to set the Macready by rotating the ASI in
the
case. Then merely match the needles for (theoretically) correct speed to
fly.

Note that these instruments are mfg'd to match a certain polar. The one I
used in my Pik was originally for a H-401 Kestrel, which worked pretty
well. If you have one made for a Glasflugel 604 and you are installing it
in a K-7, then you are going to have big problems. Mine had a label
stating the glider it was calibrated for.

The Sohlfahrtgeber was much more usable than the old Cambridge Mark IV
with
electronic speed to fly in the same glider, especially at high speeds. In
fact, it was the easiest and most reliable speed to fly I have used. Many
speed to fly units go wild at high speeds and become useless.

I would recommend not using the diaphragm compensator with this vario. As
another poster pointed out, the diaphragms get stiff (and/or perforated)
with age.

Sorry for the long post!
-Bob Korves
5H Duo Discus
5K Lak-17A