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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 12:37pm PT
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Not sure anything is rested here. can you fill me in? I'm really curious.
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High Fructose Corn Spirit
Gym climber
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Oct 28, 2016 - 12:40pm PT
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HFCS, yes weight only relates to speed.
So snakefoot, I'm 500 lbs, my girl is 100 lbs. Wing surface area for both our suits is 10 ft2. You're in agreement with Sula that our glide ratios - whether in theory or actual practice - would be the same?
"Wingloading" in my case would be 50 lbs/ft sq. Wingloading in my girl's case would be 10 lbs/ft sq. Right?
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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 12:45pm PT
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yes, but the speed at which you fly will be different. more weight increases speed when all other things are the same. This is very simplified on a very complex structure (wingsuit).
thanks gary, these guys who wrote this are friends and i try to read as much as i can on the whole topic.
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High Fructose Corn Spirit
Gym climber
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Oct 28, 2016 - 12:52pm PT
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(1) but the speed at which you fly will be different
Got it.
(2) This is very simplified on a very complex structure
Got it.
Yet it still seems given the huge difference in "wingloading" in our example, I at 500 lbs would have to fly at an impractically fast speed to acquire the glide ratio of my 100 lb partner.
I'm a noob, here, thanks for the discussion.
PS.
And that being the case then re different speeds, I guess she and I could never expect to be able to fly together, side by side if not hand in hand. Boo-hoo.
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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 12:56pm PT
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More like she would have to fly faster to keep up with you at the same glide, like put weights on
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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 12:59pm PT
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tami, sounds like true love to me, eh?
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High Fructose Corn Spirit
Gym climber
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Oct 28, 2016 - 12:59pm PT
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A couple more points here, if you don't mind... (1) There is the terminal velocity of a falling body behind all this. Right? No body goes faster than 135, say. Right? (2) So we are talking, and constrained by, a velocity range to all this, say 80 to 135 mph. Right?
(3) Curious. Does any (heavy) wingsuit jumper ever "glide" literally twice as fast as another given more or less the same suit?
...
re: free fall, human
"With air resistance acting on an object that has been dropped, the object will eventually reach a terminal velocity, which is around 53 m/s (195 km/h or 122 mph) for a human skydiver."
"A typical skydiver in a spread-eagle position will reach terminal velocity after about 12 seconds, during which time he will have fallen around 450 m (1,500 ft)."
https://en.wikipedia.org/wiki/Free_fall
So my ultimate speed at 500 lbs and "wingloading" of 50 lbs/ft2 seems awfully limited.
But no worries, I've got a jetpack. lol
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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 01:07pm PT
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again, the idea of terminal is to limit the variable in the equation. We can fall and i mean fall well over 200 mph if we point head down. the topic is oversimplified to say the least, but usually people fall within the range of 90-140 downward. the wingsuit changes the direction of velocity and this can be changed with other factors, body postion, weight, type of suit and so on.
this weight factor used to be an advantage in the old wingsuit races that were steep and had no need for other skills. now the race courses are about multiple skills
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AlanDoak
Trad climber
Boulder, CO
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Oct 28, 2016 - 02:52pm PT
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Wingsuit flyers are not in freefall, they in in gliding flight.
Sailplane theory:
"If the operating weight of a given glider is increased, the
stall airspeed, minimum controllable airspeed, minimum
sink airspeed, and the best L/D airspeed are increased by
a factor equal to the square root of the increase in weight.
[Figure 5-9] Glide ratio is not affected by weight because,
while a heavier glider sinks faster, it does so at a greater
airspeed. The glider descends faster, but covers the same
horizontal distance (at a higher speed) as a lighter glider with
the same glide ratio and starting altitude."
http://www.sweethaven02.com/Aviation/MaintHandbook/gfh_ch05.pdf
Cross-country glider pilots will commonly add water ballast to their vessel in order to increase the speed they can reach the next point; which does not reduce the maximum glide ratio, but does reduce climbing performance in thermal updrafts.
I'm assuming there are more non-idealities in a wingsuit versus a sailplane, but this is the first order effect.
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JLP
Social climber
The internet
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Oct 28, 2016 - 03:01pm PT
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That's another thing I find interesting about that interview - they talk like highly educated and experienced aeronautical engineers or top air force test pilots or something - to let us all know they have such a solid grip on the medium - but holy sh!t - they're so not - and they so don't...
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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 03:02pm PT
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Rich who did the interview was a navy fighter pilot fool.
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JLP
Social climber
The internet
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Oct 28, 2016 - 03:04pm PT
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Haha - perfect - and you??
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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 03:07pm PT
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Oh, are we now discussing credentials in order to be an as#@&%e? lets just say i have fifteen years of formal education in neuroscience.
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JLP
Social climber
The internet
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Oct 28, 2016 - 03:10pm PT
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Oh yeah - and type AAA+++maxxx, too, you nail it!
Have fun with gravity, expert fly boy!
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snakefoot
climber
Nor Cal
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Oct 28, 2016 - 03:15pm PT
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hey, i enjoy the snarky comments. no prob for me, talk is cheap around here.
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Sula
Trad climber
Pennsylvania
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Oct 28, 2016 - 03:35pm PT
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While I was away, AlanDoak supplied a good answer. Yes, the speeds of various performance points (stall, best glide, etc.) scale with the square root of wingloading.
So if wingloading were to increase by a factor of 5 (unlikely in the case of Wingsuit BASE jumpers), speeds increase by a factor of 2.24. A more reasonable ratio between max and min wingloading would be something like 2.5, which gives a speed ratio of 1.58.
And it's probably not realistic to assume that small and large jumpers would have the same wing area. I imagine that a large wingsuit takes more strength to control properly, so it would be used only by a large & strong jumper.
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Sula
Trad climber
Pennsylvania
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Oct 28, 2016 - 03:46pm PT
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And if we wish to talk about terminal velocity in freefall (which is indeed different from gliding in a wingsuit), that scales in a somewhat similar way, but with a complication: it's proportional to the square root of mass divided by "projected area".
Because the heavier jumper can be expected to have a higher projected area, his terminal velocity will not be as much greater as a calculation based on weight alone would indicate.
(All of this ignores annoying complications such as Reynolds number, subtleties in how drag changes with speed, etc.)
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The guy above
climber
Across the pond
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Oct 28, 2016 - 04:18pm PT
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That's another thing I find interesting about that interview - they talk like highly educated and experienced aeronautical engineers or top air force test pilots or something - to let us all know they have such a solid grip on the medium - but holy sh!t - they're so not - and they so don't...
Ha, ha, ha, ha!!!
Here's your shovel, you keep digging...
Richard Webb has been active for more than 20 years in both professional aviation and canopy sports. He holds an Aeronautical Engineering degree and multiple Flight Instructor certificates in Airplanes and Helicopters.
A nine year chapter in the US Navy flying F-14 Tomcats off aircraft carriers came to an end after buzzing an airport control tower in a brand new F/A-18 Super Hornet. After being notified that his flyby services were no longer needed, Richard was politely asked to leave the Navy.
Totally worth it.
And in case you think that's a joke...
http://articles.latimes.com/2005/oct/19/local/me-jetfighter19
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