Suit area vs flyer weight.....

[Professor 0]

I agree with Tonto for body type ordering, especially for fall rate performance. It effects glide performance as well, but not as obviously. However, this is at best the third most important factor in performance, with pilot skill and suit type being first and second. Physical fitness starts to play a role with the more advanced suits, further negating the impact of body type. Also, the wingsuit community isn't a very big one. The companies making these suit are small operations, and I'm guessing that people with builds close to those of the primary test pilots of the suits (Robi for PF, Yari for BM, Loic, etc) will be at an advantage.

All the aerodynamic theory is great, but it really doesn't hold too strictly in the wingsuit world. When your aircraft's 'airframe' is moving around and changing shape unpredictably, the 'theory' stuff gets too complex to be workable.

Ted
Like a giddy school girl.

[F16Driver 0]

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The only way that we can "max perform" a wingsuit is by knowing what that L/D max airspeed is. Unfortunately, we would need to carry an airspeed indicator and try different airspeeds, or be lucky enough to get into a horizontal windtunnel, get hooked up, and check different airspeeds. Body position and wing position adds more variables to the problem, also.

You've just left out the desity of the air. E.g. one tracing position is good @ 4000m and start stalling around 2000m.

That's false. You DON'T change airspeed based on your altitude. If you were able to know what your L/D max airspeed was and were able to have a airspeed indicator to maintain it, you would be max performing the suit through all altitudes.

EX: When an aircraft lands it flies an approach speed, lets say for this example 100 knots. At an airport at or near sea level, the aircraft will be at 100 knots when it touches down (IAS=TAS). At higher elevations (mountains), the approach is still flown at 100 knots. However when the aircraft lands it will be going maybe 120 knots (just a guess, I don't have the formula in front of me). This is because the TRUE airspeed is higher than the INDICATED airspeed because of the density of the air. Even though it touches down faster, the approach speed is still flown. This is about the simplest way I can explain it without getting into more detail.

Dangit you guys, your making me remember all my college crap!!!

"I promise, I will never die."

[F16Driver 0]

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All the aerodynamic theory is great, but it really doesn't hold too strictly in the wingsuit world. When your aircraft's 'airframe' is moving around and changing shape unpredictably, the 'theory' stuff gets too complex to be workable.

Like I said before, there are other factors to consider when max performing a wingsuit. But you still have to use some of the 'theory' stuff to make it all work (Even though some of it is complex)

"I promise, I will never die."

[pchapman 261]

To address one of the topics in this thread, let's have a look at the issue of scaling people up and down, and how that affects wing loading and stresses on the jumper. It is useful because the effect of scaling laws are non-linear, and as someone said, we don't naturally think very well in non-linear terms.

While this stuff should help to understand the effect of scaling alone, there are of course other at least as significant factors that have already been mentioned, like jumper skill, body position, and body shape. People probably don't scale up and down perfectly evenly (such as in the percent of muscle mass, or proportion of torso to limb length, or whatever). The proportion of skinny or more solidly built people may also vary depending on their height.

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The basic physics of scaling are that
volume (and mass) increases with the cube of the length, and
area increases with the square of the length.

As an example, consider a 6 ft tall jumper vs. 5 ft tall jumper, OF THE SAME BODY SHAPE:
The taller one is 20% taller,
would have a 44% larger wing area,
would have a 73% greater mass, and therefore
would have about at 20% higher wing loading.

WING LOADING EFFECTS:

This square & cube law thing is the primary reason why ants hardly notice a long fall, a mouse may brush itself off uninjured, a cat might limp away injured, while a human goes splat.

The 20% extra wing loading translates into more speed at a similar glide ratio.

Basic aerodynamics then says the glide ratio doesn't change. But additional factors might change things.

(It isn't quite the same situation as for a jumper under a parachute, where the same person under a smaller, higher wing load canopy still has the same body drag area, same line thickness, etc. as under a larger canopy, like tso-d_chris wrote about.)

Who knows, there might be some small tendency that at the same wing loading, a larger wingsuiter would have a better glide ratio. This is like swooping with weights and a larger canopy at the same loading. Crinkles in the fabric may not tend to scale up much, harness webbing stays the same size, etc., so their disturbance will be proportionately lower for a larger wingsuiter.

MUSCLE STRENGTH EFFECTS:

As for the comment about small people being able to outdo the tall & skinny, by better being able to hold a good body position, one can keep on playing with the effects of scaling. The taller person's arm is longer, the load is greater, but the shoulder size and muscle size are greater too. In the end, there's both a 73% increased muscle mass and 73% more force needed. But that doesn't even everything out, as the cross sectional area of the muscle has only gone up 44%. So the stress per unit cross sectional area is 20% higher on the taller person's muscles. Even without knowing the biological details, I expect that that is important to what force the jumper can apply. It goes right back to the idea of volume being cubed, but area squared.

(I did run basic engineering calculations on this to confirm the numbers. The jumper's arm can be considered a cantilevered beam supporting a spanwise distributed load, with a muscle applying an inwards counteracting force at the bottom of the root of the beam.)

So the scaling laws suggest the bigger person person is at a strength disadvantage, if the person is of the same body shape and proportions as the smaller person.