"T o d d P a t t i s t" wrote in message
...
"Bill Daniels" wrote:

John, I'm sure there are situations where that applies but the reduction
in
turn radius is not great for a small reduction in airspeed. For example,
reducing the airspeed from 50 to 45 knots in a 45 degree bank decreases
the
radius by only a little more than 40 feet.

You are missing the point. You don't reduce airspeed to get
a tighter turn radius. You reduce airspeed to get a
shallower bank in the *same* turn radius. The shallower
bank, even when flown at an airspeed less than the min sink
speed for that bank, produces a lower sink rate than the
same turn radius flown faster at a higher bank angle.
Flying at min sink for the bank angle is not the optimum.

See the Turn Radius Calculator:

http://www.soarcsa.org/thinking_page...n_rad_knots.ht
m

See Jud's article.

I read the article and I don't agree with it. I think it's much better to
fly the minimum sink airspeed for the bank angle. Lets do the math.

A 45 degree bank at 43 knots results in a turn radius of 164.1 feet. For
me, that's a fairly standard thermalling turn that takes 14 seconds. That's
minimum sink in my Nimbus 2C if flown dry and it turns inside almost
everyone including the 12 meter ships.

At 40 knots and 40 degrees bank the turn radius is 169.3 feet. That
actually INCREASES the turn radius and it means I have to wobble along just
above stall at a high sink rate. That's a very bad deal from both a soaring
and safety standpoint.

Maybe if the starting point is someone that flies a 45 degree bank at 65
knots with a 375.1 foot radius, it looks different. Reducing the airspeed
to 45 while reducing the bank to 30 results in a radius of 311.3 feet or a
radius reduction of 63.8 feet. That's significant but just reducing the
speed to 45 knots turn is better still.

In fact, 45 - 45 is a good turn for most gliders. At a 45 degree bank,
there is little increase in G load so the sink doesn't increase much at all.
I'm beginning to think there is a big payoff for an angle of attack
indicator so we can just fly AOA and not have to compute these things.

Bill Daniels