A polar calculation question for you number crunching enthusiasts out there

If I understand your question correctly you need to have your polar curve
plotted on a grid which has an origin, e.g., (0,0). You get min sink speed
by drawing a horizontal line from the Y (vertical) axis which is tangent to
the curve. Record the speed and sink at that point. You get best L/D by
drawing a line from the origin (0,0) which is tangent to the curve. Record
that speed and sink rate. Pick your third point at a reasonable cruise
speed, say 80 kts and pick the sink rate off the Y axis for that speed.

I don't mean to insult you with the above, I just don't know if you know.

"ES" wrote in message
...
I'm trying to use Paul Remde's very handy "Reichmann to Cambridge and
SeeYou" spreadsheet to derive some usable SeeYou polar numbers for my
Diana-1. But I'm having a heck of a time picking three speed/sink-rate pairs
from the data set that result in Max L/D and Best Glide Speed numbers that
pass the sniff test.

For example, I can enter 3 pairs of values from early, middle, and late in
the data set, and it tells me I have a max L/D of 49 (wouldn't that be
nice!) at ... 38 km/h. Uh, that's well below stall speed!

Is there any conventional wisdom on this?

Are there any other tools available that can take a set of sink rates
(hopefully more than 3) and produce some decent numbers?

Wishing the flight computers would just start with lookup tables,

tuno/ES