On Sep 22, 2:08*pm, wrote:
On Sep 21, 8:49 pm, GM wrote:

Hi all,

does anybody have a usable, step-by-step decription of the LX-Polar
program? The instructions that came with the manual of my LX-20-2000
are pretty useless. I have a polar curve for my glider and I am trying
to calculate the factors a, b and c used to define the polar.
Thanks,
Uli Neumann

Uli,

Basically you just have to invoke the program. *It expects input in km/
hr and m/s, so if you are using American
units you'll have to convert them first. *I had a devil of a time
figuring this out with the LX5000
in our club 304C; the values for the coefficients didn't make sense.
Finally I determined that
they output the sink rate in m/s when fed the speed in 100s of km/hr
(hectakilometers?). *9B's
comments about wing loading, actual experienced polar, etc. all apply
too

Armed with that information I found that the 304 entry programmed into
the unit must be the old
Glasfluegel 304 from the 1970's with about a 36:1 glide ratio. *The
304C is closer to 42:1 and of
course has a different wing loading (especially with me in it), so the
glideslope info the unit spits out
is not very useful for flying fast. *It was very disappointing to
arrive at the finish line about 1000' high
after my PDA cable went inop the last day at R5N, causing me to have
to navigate the old fashioned way.
Now that I know what the coefficients are, all I have to do is
convince the unit to use them!

Matt (sometimes AI)

Hi all,

thanks to all that responded. The problem was simply in the
installation of LXe on my Laptop. For some reason or another, I could
not insert the measured data pairs into the coordinate system. I wiped
LXe from the computer , downloaded the latest version from the LX-Nav
site and re-installed it. Now it works like a charm.
I also got a short version step-by-step from Dr. Michael Seischab at
LX-Navigation.
Here is how to use LX-Polar:
1 if you have a polar curve for your glider (measured or calculated),
make sure the speed is in km/h and the sink is in m/s
2- open LX-Polar
3- under tools, pick 'Insert'. The pointer changes from the arrow to a
hand
4 - move the hand over the coordinate system to the X-Y position. The
exact X-Y position is shown below the coordinate system
5- left-click to insert the point
6- repeat for each point beginning at # 3
7- if you misplaced a point, use the move function to correct the
placement or the delete function to erase a point.
8- enter as many points as you like.
9- when done, hit F9 or select 'calcuate' from the Tools drop-down
menue. The result are the three factors a, b and c displayed in the
coordiante system and on the left side. The program also shows the
max. L/D at what speed and sink rate.
On my LX-20, I can enter these three points under the User-Polar. I
will have to experiment a bit with this new polar before setting out
on that record breaking flight ;-)
Again, many thanks for all the responses.

Uli
Libelle 'GM'