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KrisFlyZ

Reynolds Number and Max L/D

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That one is easy. Low Re numbers correspond to dominance of viscous forces over the inertial forces. Viscous forces = friction. It's impossible to make such a configuration of the wing that friction will have a component perpendicular to the flow (lift) much greater than the parallel component (drag). Only by cleverly using inertia of the air you can achieve maximum L/D.
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In my studies of small airplanes, a 30 inch chord seems to be about the minimum.
Yes, you can build a wing tip smaller that 30 inches, but it is unlikely to be very efficient, unless you have a very gracefully balanced design and very tight quality control.

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That one is easy.



Then why did only 3 people out of 13 get the correct answer?

http://www.desktopaero.com/appliedaero/fundamentals/reno.html

Anyway, the chord length or the mean chord length is the characteristic length used to calculate the reynolds number for a wing.

Kris.


Thanks! I can fly much better and longer after I gained this info. ;)

I really don't know how birds can fly without knowing a sh1t about aerodynamics.:S

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Yea, I just went out on a jump and tried it, it works great!! All I really know for sure is my Reynold's number is better and can beat up your Reynold's number. ;)
"The evil of the world is made possible by nothing but the sanction you give it. " -John Galt from Atlas Shrugged, 1957

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It is not about good or bad reynolds number. In the range that all humans fly, nothing definate can be said about what body shape/size is better because of its reynolds number.

The point of the post is not to try and prove one is better than the other, it is to show that the range of reynolds numbers that we fly at is actually a good thing. Lower reynolds numbers when flow is streamlined but viscous forces dominate(that would be like trying to move a wing thru honey to generate lift) does not allow good L/D.

Birds have this information ingrained chemically in thier brains(?), they do know all this stuff. We can learn a lot by observing them or by reading the published works of people that have spent a signifcant amount of time doing that.

Here is an example. The article has important information that one can apply to their wingsuit flying, if they were so inclined. :P

Kris.

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I assume were talking about the aspect ratio of the arm wing, like a fast parachute has a higher aspect ratio over an old slow accuracy parachute having a more square low aspect ratio,

the problem we have with a wingsuit is that too much wing cord at the wrist is very tiring on the arms,
were making the arm wings long at the body and short at the wrists to alleviate this problem,
thats my 2 peneth worth
Life is a series of wonderful opportunities,
brilliantly disguised as impossible situations.

tonysuits.com

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Hi Tony,

This post was just meant to be a theoritical discussion.

Reynolds number or biggest chord does not mean anything. When applied to the regime that we fly our wingsuits in. Bigger wing chord in a wingsuit does not imply better glide. It does have some advantages for arm wings. Be happy to discuss if you are interested.

Afterall, the biggest chord anyone can get (whole body as a wing) is when we track. As soon as we start spreading the legs, the chord reduces and the velocity reduces(at best glide). Adding wings reduces the velocity even more at best L/D speeds.

Reynolds number for a wingsuit flyer will be lower than the same person's Reynolds number in a track. Does anyone track better without a wingsuit than in one?

Kris
P.S: I met you at the Richmond Boogie in 2004. Came to see if you could help hook up my GPS on my helmet. You suggested sewing a pouch on the GTI and I chickened out.

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Reynolds number for a wingsuit flyer will be lower than the same person's Reynolds number in a track. Does anyone track better without a wingsuit than in one?

Kris
t.



But that's an invalid comparison, since you are changing a whole bunch of variables at the same time, not just Re.
...

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

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