WS Altitude change after high speed pass

[kallend 1,648]

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wingsuits don't fly at 45 AOA

You're talking about efficiency (maximum or at least decent L/D), which in this case - climbing above the plane as high as possible - is not... efficient (no pun). What is necessary is to maximize the force that pushes you up. Since in the first few seconds of high-speed exit your speed is almost entirely horizontal (the vertical speeds during the climb - 10-20mph are still much less than horizontal ~120-160mph), that force is lift.

For most bodies - be it a superefficient glider, a slab of wood or a brick, the lift is maximum at around 45 degrees (+/-5 degrees).

Stall is a significant drop of lift when AoA exceeds certain value (usually 10-15 degrees). After passing through the minimum, lift goes up again with increasing AoA and reaches maximum at ~45. And that's what we need for the climb.

By the way, because our body dampens the lift/drag characteristics of the wings so much, overall we do not have that dramatic drop of lift (if at all) as airplanes do. The lift simply monotonically (although not as a straight line) increases from 0 at AoA~0, reaches maximum at ~45 and goes back to zero at ~90 degrees.

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they stall much sooner (as do parachutes), even at the slightly higher jumpship airspeeds

Stall has nothing to do with airspeed. You are confusing powered level flight (where AoA to maintain level flight depends on speed) with nonpowered gliding. Stall is a function of AoA only.

And "wingsuits don't fly at 45 AOA" is a 666th reason why flocking sucks, since that's typical AoA for most flocks (L/D=1).

Yuri

But the altitude GAIN is some integral of lift during the transient, and if the drag is excessively high due to excessive AoA the speed (and therefore lift) will bleed off rapidly, decreasing the length of the transient. I think it naive to claim that 45 degrees is the best angle without some hard data.

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The only sure way to survive a canopy collision is not to have one.

[yuri_base 1]

You are right, and Vesa's 30 degrees may be actually closer to the "absolutely right" answer than 45. Also, the optimum angle will depend on wingloading, type of suit, body type, etc.

I was leaving this out because 45 degrees is a reasonable first estimate and we do not have lift and drag as functions of AoA yet. But we will. The data will allow one to do Monte Carlo simulations and find the best angle.

Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

[vidiot 0]

When climbing directly after exiting the plane, your trajectory is 'forward-up', so the AoA is less than seen on photos.

Should the trajectory be 30-35°, the resulting AoA would be 10-15° and everybody on this thread would be happy

Yuri, I am sure you can milk your formulas for the inclination of the trajectory for us?

Klaus

My Logbook

[yuri_base 1]

Klaus, I can milk my formulas until the last drop.

I was underestimating the duration of the climb and the associated importance of drag-induced deceleration, as Professor Kallend pointed out. It turns our that effect was not small. See the attached spreadsheet, it has a lot of superschweet condensed milk! Play with the sustained horizontal and vertical speeds for a fixed initial [high-speed pass] speed. The trajectory drawn is relative to ground. Negative Y is above the plane.

Can you milk more milk and put a Solver in there to maximize the climb by varying vertical and horizontal sustained speeds? (I don't have Excel Solver on my computer.) Of course, it makes sense to limit the vertical and horizontal speeds by some reasonable ranges so we don't get some crazy combination like Vx=666mph, Vy=0.666mph.

Of course, these calculations are in assumption of constant L/D (i.e. constant adjusted lift and drag coefficients Kl and Kd). When we know real Kl and Kd as functions of AoA, Monte Carlo simulations can be carried out to find out the optimal pitch angle as a function of time to achieve even higher climb than for constant AoA.

Yuri


P.S. Jarno, you're my hero, BUT... Vesa and Professor are now my heroes, too!

Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

[kallend 1,648]

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You are right,

I love it when you talk to me like that.

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The only sure way to survive a canopy collision is not to have one.