How does a canopy turn?

[quade 4]

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When you pull a front, that side isn't changeing the shape of the wing (camber or planform).

Pulling front risers most certainly changes both angle of attack and camber. I do not see how it could do otherwise.
Paul
http://futurecam.com/skydive.html

[markbaur 0]

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Isn't that what a Vario is for? ;^)

The wink says you're not so serious, but ... the vario just gives an indication of the strength of a thermal (or, if you're unlucky, the rate of sink). You still need to do some calculations to figure out the best speed to fly, which is dependent also on weight and expected thermal conditions along your route.
Mark

[freeflyguy 0]

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I do not see

It only twists the wing, changing the AOA on basically one side. If you don't see, either re-read my post, or hit the books.

[quade 4]

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It only twists the wing, changing the AOA on basically one side. If you don't see, either reread my post, or hit the books.

If the wing were not flexible in multiple directions, I might agree that it would not change the AoA. However, the wing is not only flexible along the lateral axis, allowing the wing to twist, but it's also flexible between the B and C lines which creates a "hinge" and therefore changes the camber slightly when you increase the tension on the A & B lines. It has to. Sometimes the effect is just a simple bend between the B and C lines. Other times it looks more like a little stair step with the A to B line section the lower step, the B to C section a slight diagonal and the C to D section the top step.
Exactly what book do you want me to hit? ;^)
Paul
http://futurecam.com

[freeflyguy 0]

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Exactly what book do you want me to hit? ;^)

It might be better if the book hit you.
***continue reading in normal careless manner***

[quade 4]

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It might be better if the book hit you.

Nice.
I take it then that you don't think my observations are valid?
Fly next to somebody, have them pull on their front risers and then look at the top surface of their canopy. Tell me what you see.
Paul
http://futurecam.com

[remko 0]

[Waking from hybernation]
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Sent: Wed, 06 Mar 2002 03:38:07 -0700
Subject: How does a canopy turn?


When I asked myself this question a while ago it kept me puzzled and awake at night for quite some time and it doesn't surprise me at all that after so many posts only Paul has touched the essence of the solution to the canopy turning problem by mentioning the pendulum effect.

The BIG difference between an airplane and a canopy is the position of the aerodynamic center and the center of gravity.

In an airplane these two are close together. Moving the aileron itself will not turn the plane but only roll it, rolling the lift vector with it creating a sideways pointing component that will turn the plane. During roll-in, the downward deflected aileron on the outside of the turn will create more lift during the roll-in thus, as mentioned before, create more induced drag. The upward deflected aileron on the inside of the turn will decrease lift, thus less induced drag. this will yaw the plane to the opposite side (outside) of the turn. This unwanted side effect is called adverse yaw and is compensated for with rudder into the turn during the roll-in and out of the turn during roll-out. Note that aileron is used only to roll-in and roll-out of the turn and not during the turn and that the resulting decreased vertical lift component will make the plane decent if not countered.

Under a canopy the center of gravity and the aerodynamic center are some 10 feet apart, depending on the line lenght. Now, pulling a toggle or rear riser down will increase lift but the weight of the jumper on that extreme long arm will prevent it from rolling. The increased drag however will yaw it, swinging the jumper to the outside (in fact, it's momentum will want to keep it going in a straight line while the canopy turns), rolling the wing and with it the lift vector, creating the sideways force. Note that the "aileron"(toggle) is used throughout the turn and that the turn is a combination of "adverse" yaw caused by increased drag and rolled lift vector caused by the pendulum effect. Also the decreased vertical component will increase the decent rate. If continued this will develop into a spiral dive which is also confusingly called a stall turn.

Remko

-- skydive long and prosperous

PS: A toggle/rear-riser increases camber as well as angle of attac, a front-riser only increases camber.