On Monday, April 18, 2016 at 7:18:31 AM UTC+12, xcnick wrote:
Dan, I have the USB to serial working in modern windows, but the Cambridge software only had ports 1 to 4 as an option. The USB to serial wire was assigned a higher number like 8.

Were you able to reassign the wire to a lower number or find later Cambridge software with a larger selection of port numbers?

Bruce, I did give you garbage. When the xcsoar numbers came out as a parabola I knew I screwed up big time. I guess those are the number generated when you choose discus.

The actual numbers from Johnson show the kink some talk about so I don't expect them to fit a parabola.

So I took my school boy ruler to the little graph on page 3 of the Johnson article and come up with the following. I guess I am looking for a quadratic equation near these numbers except 97 knots. Because of the kink 97 knots should be off the most.

max L/d 42.5 @ 53kts min sink 115 ft/min @ 45kts
50kts 121 ft/min or 1.195kts or .615 m/s
60kts 160 ft/min or 1.58kts or .813m/s
65kts 195 ft/min or 1.925kts or .99m/s
76kts 270 ft/min or 2.666kts or 1.372m/s
80kts 308ft/min or 3.05kts or 1.569m/s
97kts 650ft/min or 6.42kts or 3.3m/s

You gave me enough I should be able to learn some calculus. I was not able to get there this morning, but I will try again.

Is the A,B,C of see you x y and z of a quadratic?

About the kink...

If this copy of a Discus polar is roughly accurate ..

http://www.fsglider.de/polaren/pol_dcs.gif

... then you never ever want to fly above the kink (at the lighter weight) unless the MC setting plus current airmass sink is 10 knots or more! In which case you should go straight past the end of the curve to .. I don't know ... whatever point between rough air speed and Vne makes you comfortable?

Meantime, you're only flying slower than the kink if MC plus airmass sink is less than 3 knots.

For every situation between MC=3 and MC=10 (in still air), right on the kink is the only place to be.

(assuming no wind)