Feature Request: Ability to move polar up/down the Y-axis

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Lenticular
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Feature Request: Ability to move polar up/down the Y-axis

Post by Lenticular » Mon Jun 14, 2021 10:33 pm

Hi,

Is it possible to enable the polar to be moved up/down the Y-axis? This is useful for determining optimum speed-to-fly when encountering sink but still flying at e.g. best L/D speed, or min sink speed.
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Lenticular
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Re: Feature Request: Ability to move polar up/down the Y-axis

Post by Lenticular » Sat Jun 19, 2021 5:22 am

Maybe moot now - I've created a spreadsheet that computes optimum speeds to fly in sink. I'll release it shortly.
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wickid
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Re: Feature Request: Ability to move polar up/down the Y-axis

Post by wickid » Sat Jun 19, 2021 8:40 am

You know the e-vario in Condor tells you what speed to fly in sink? Press right ctrl to set it to sollfahrt (speed command) mode. Alternatively watch the arrows on the left part of the screen. This is assuming you set your MC setting for the expected climb.
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Lenticular
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Re: Feature Request: Ability to move polar up/down the Y-axis

Post by Lenticular » Sat Jun 19, 2021 11:31 am

Yes I did, but I use the polar chart for pre-flight planning.

Not sure how it's done IRL, but I can imagine there are situations where you want some ballast, but not max ballast.
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wickid
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Re: Feature Request: Ability to move polar up/down the Y-axis

Post by wickid » Sat Jun 19, 2021 1:02 pm

Yes. If the thermals average below about 1.5 it may be more efficient to have half ballast due to the relatively long time spent climbing. The few cm/s you sink more with water become more and more significant the weaker the thermals become.
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wickid
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Re: Feature Request: Ability to move polar up/down the Y-axis

Post by wickid » Sat Jun 19, 2021 2:55 pm

I wanted to elaborate a bit more on the above.

It is not only the straight flight 1G polar you have to take into account in this calculation. Some manufacturers also produce circling polars. They show the increase sinkrate when flying with bankangle. What you have to take into account is that bank give a higher loadfactor. This has the same effect as adding ballast (higher wingloading). 30 degree bank gives you a 0.15 increase in wingloading. That is similar to adding about 20 kg of waterballast to a typical glider. 45 degree bank is like adding about 150 kg!

What also happens is that you have to maintain a higher speed with water. This makes the radius of your thermal turn bigger. That also reduces the effective climb you can achieve. Where the crossover lays depends on how much the climbrate suffers. That depends on how easy the thermals are to center and what the actual difference in climbrate between an empty and full glider is. My rule of thumb is, if I average below about 1,5 m/s with a full glider, I dump about half the water. If it is less than 1 m/s on average, I dump everything.

One thing to consider is: Any thermal before the line does not count towards your average speed. So if you plan to fly with less than full ballast, ALWAYS fill up to full. Only dump just before you reach your first climb. This gives you an advantage of being able to fly faster on the first glide and having more energy going over the start line because of all that mass. In real world the hassle of filling the glider might not be worth it, but in Condor we don't have to lug cans of water around.
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