On Thursday, June 11, 2015 at 8:22:42 AM UTC-7, Steve Leonard wrote:
Actually when you do the simple, graphic solution, you find that the speed you should fly if your ring is set to 2, and you are flying in air that is going down 1, is the speed you should fly if the ring was on 3 and the air was still. And believe it or not, the speed ring shows just exactly this.. It does combine the higher glider sink rate due to higher speed with the air mass sink rate to point towards the correct speed to fly.

If you put together the chart, you will come up with a speed to fly for each wind speed and no air mass vertical motion. That is the easy part. If you know what the glider sink rate should be at that speed, and you see that the sink rate is higher, you can then adjust roughly based on a chart. This is not to be something that you are trying to extract every possible inch of distance the computer says you can get. This is a ballpark. The air will change as you fly through it. It may go down slower in just a couple of seconds. If you are going to try and chase it that much, I will leave you to your own devices. My vision is a 5 by 5 table at most. 0, 10, 20, and 30 knot wind columns, rows for 0, -100, -300, -500 air mass sink rates.. And you can probably narrow it down more from there if you see the speeds don't vary too much.

Steve Leonard

Roger - got it. The speed ring only knows what the glider is doing, not the airmass so it's a bit of an iterative solution. It's easy to figure out best glide speed for any given sink rate (OP question I believe), the trick is doing some simple math in your head to: 1) read the vario, 2) read the airspeed, 3) estimate the sink rate of the glider based on #2, 4) use the difference to pick a speed to fly. Easier if you have a Netto or speed to fly.

Honestly, if the needle points down I speed up. If it points way down, I speed up a lot. I've done the math on flying off-optimal STF. Precision only matters if you are in a long line of sink and the effects compound.

Might be best to just have a linear rule of thumb on three dimensions: 1) for every X increase in sink, fly Y knots faster, 2) for every Q knots in headwind, fly R knots faster and 3) for every A knots faster you fly subtract B knots from the vario reading to get netto so you know what the air is doing. If you center it around best L/D plus 10 knots, 2 knots of sink and 10 knots of headwind, the liner rule of thumb should work reasonably well.

9B