Glide slope

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I started by flying too slowly and this is a bit of physics about why that doesn't work:

This is a Polar Diagram.
It is a plot of sink rate against air speed. I've no idea what model glider this represents but apparently it is a hang glider.
Since my data is from the USA it is MPH across the top and feet per minute vertically (1 meter/sec = 197fpm):

I'd say it's pretty much as you'd expect. Go really slowly and nothing is working well so it sinks quite quickly. Go a bit faster and it gets better, go a lot faster and you're burning up lots of energy to push air out of the way and the efficiency drops again.

Since we have speeds we can recalculate it all into feet per minute, apply an arctan and get the glide slope angle in degrees:

Again pretty much as you expect with a rotten glide angle when you're slow and inefficient and although it drops off a bit as you go faster you are getting more airspeed and covering more distance so the higher sink rate doesn't cost you so much angle.

However this is not how you react.

Imagine you are starting on a nursery slope that runs down at about seven degrees. See how your takeoff run puts you on a really bad part of the curve. If you are gliding at more than seven degrees your feet keep touching down and if you are gliding at less than seven degrees you gain a little altitude. So to stop loosing height you must pull the nose down so you accelerate. Every bit of speed gives you a better glide angle so the slope you were running down does not come back at you so fast. You don't want to fly up at this point but down.
I found that counter-intuitive but flying down actually gains you altitude with all the advantages that higher speed gives as the control becomes crisper.

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