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Old Dec 05, 2012, 01:46 PM
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United States, ID, Burley
Joined Mar 2012
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Originally Posted by botulism View Post
Viking, regarding your previous posts about the P2K's anemic 'turn' response with the rudder.

The sailplanes you specifically point out in your previous posts as having much better turn response than the P2K (the Spirit 100, the EZGlider, and your 'more recent designs...flat-built wings with elliptically up-swept wing tips' all have one thing in common. Polyhedral. Or upswept wing tips (the little anti-vortex wingtips on the P2K don't count as such).

The reason you think the P2K has anemic rudder response is because it's doing exactly what it was designed to do. The rudder is designed to yaw the plane, not initiate turns. On a plane with flat wings, the only thing that's going to roll it (on its longitudinal axis), is the ailerons. Think of a pylon racer. They long ago discovered the quickest (most efficient) way to turn was to bank it (so the wings are 90 degrees to the horizon) and yank it (full up elevator). Pylon racers (and a lot of slope sailplanes) don't even have rudders.

Think how a sailplane with polyhedral (or even dihedral) turns. You yaw the plane left or right with the rudder, and viola, the wingtip facing into the direction of flight
goes UP, just the same as if it had ailerons, and you had rolled it one way or the other. That's because of that big plank on the end of the wings facing into the airstream, forcing the wing up.

A flat wing has no big surface to initiate the roll, so it's going to merrily cruise
on down the highway, yawing to the R or L, but not turning. Meanwhile, you're
thinking 'golly, that thing sure doesn't turn (roll) as well as my xxx'.

As far as 'initiating a turn with the rudder, and then applying opposite aileron' - that's called a slip, and is only useful to increase the frontal area of the plane, which increases the drag, giving it a worse glide
ratio. Only really useful if you're trying to lose altitude, eg. when landing, or to get out of a monster thermal.

You may have found that works for you while turning in a thermal, but 'conventional wisdom' (I hate that term) says it's not doing what you think it's doing, nor what it was designed for ie. a large flat circle.

So, there you go. I'm sure you'll have comments.

btw, I can't believe the weather there in CO this winter, isn't South Park usually covered in snow, with fierce 100 MPH winds in the winter?

i guess im just used to a rudder not used to turn, had no problems when i flew it. very responsive and will turn standing on a wing,with ailerons
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