Polars web page

Hi,

At the request of a WinPilot user I have added WinPilot polar parameters to
my Polars web page. I also pulled a lot of data into my page from the data
provided by Carl Herold and displayed on the WinPilot web site. I have also
received data from quite a few pilots from around the world.

There was some confusion when pilots were sending me polar data. Some would
use the factory polar or data from a measured polar data but then supply the
all-up dry weight (with pilot) of their particular glider. I think it is
very important to remember that polar data is only valid at the wing loading
(and therefore weight) of the glider used when the polar data was measured.
If the weight of your glider is different it is not as simple as changing
the weight value when you enter the polar data into your soaring software or
flight computer. The correct thing to do would be to re-calculate the polar
numbers to adjust for the difference in weight between the glider used for
the polar data and your glider with you in it. As the weight increases the
polar will shift down and to the right.

To make it easy to calculate the adjusted airspeed numbers for your glider I
have created 2 new Microsoft Excel spreadsheets. All you need to do is
enter the polar data from the data source and then enter the current all-up
dry weight of your glider and the spreadsheet provides the adjusted numbers
for your glider. One spreadsheet accepts polar data in the Cambridge format
and one spreadsheet accepts data in the "WinPilot" or "Reichmann" format.
Both spreadsheets provide polar data output in both formats so they can be
used to convert polar data between formats. The equations used in the
spreadsheets were quite simple. I used equations from Helmut Reichmann's
book "Cross-Country Soaring" for the polar calculations and derived some
equations for the polar conversions myself. However, the output can be
strange depending on the polar data provided. When converting polar data
from the WinPilot to the Cambridge format it sometimes lead to data that
looks a bit off. That is due to the way the a curve is fitted to the data
and can't be avoided.

Of course, the polar data on the web page must be used with caution. The
pilot is responsible to make sure the data looks correct.

Below is the procedure I recommend for creating polar data for your glider
with you in it.
Procedure for Creating Polar Data for Your Sailplane

1.. Find flight test data or a factory polar or data from the table on the
web site.
2.. Take data from the polar and enter it into one of the 2 spreadsheets
found on the web site. It is my opinion that the Cambridge approach to
representing polar data is the most accurate way to enter the data.
3.. Enter into the spreadsheet the weight of the glider when the data was
measured
4.. Enter the all-up dry weight of your glider with you and everything you
fly with
5.. Read the polar data for your glider from the spreadsheet
Please continue to send polar data to me and let me know if you have
corrections to the data on the web site. Ideally the data would come from
actual flight tests. Be sure to supply the weight of the glider used to
measure the flight data.

The polar web site is available he
http://www.soarmn.com/cumulus/polars.htm

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com