AVSIG: self launch skydiver.. wwswsigarch.jpg (7236 bytes)

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AVSIG Discussion Sections >> Drones, RC, Sport, Recreation

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Jeff Hartmann CIC
Top Gun


Reged: 05/18/04
Posts: 7323
Loc: Chico,CA
self launch skydiver..
      #225906 - 12/05/08 10:49 AM

Could be true...maybe not..

Creative !

http://www.metacafe.com/watch/2070868/extreme_parachuting/

--------------------
Jeff

nothing clever to say right now...


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B. Butler (Oregonian)
Top Gun


Reged: 05/15/04
Posts: 9760
Loc: Ashland, Oregon
Re: self launch skydiver.. [Re: Jeff Hartmann CIC]
      #225919 - 12/05/08 12:58 PM

Here's a longer, clearer version.

http://www.metacafe.com/watch/2076978/this_guys_having_extreme_jump_with_catapult/

Seems improbable, but after seeing this one, I'm not so sure.

http://www.metacafe.com/watch/yt-XMCAlXViRis/gofast_catapult_parachute/

--------------------
"Why not be a nihilist? A man has to believe in something."
-Bernie Gunther


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Scott Dunham (RDU)
Top Gun


Reged: 04/29/04
Posts: 6470
Loc: Chapel Hill, NC
Re: self launch skydiver.. [Re: B. Butler (Oregonian)]
      #225957 - 12/05/08 02:59 PM

>> Seems improbable...

Seems like an audition for the Darwin Awards...


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Dan Barclay [ORG]
Top Gun


Reged: 05/06/04
Posts: 4492
Re: self launch skydiver.. [Re: B. Butler (Oregonian)]
      #225986 - 12/05/08 06:09 PM

>> Seems improbable, but after seeing this one, I'm not so sure.

I can't imagine that his legs could withstand that, particularly when it
appears that one was significantly bent at the knee.

Does someone want to do the G calculation... acceleration over a 2ft distance
to a speed enough to travel some distance (a couple of hundred feet?) in the
air.

I don't see it, unless someone can come up with an acceleration in a
reasonable range.

Dan


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Ralph Jones
Top Gun


Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Re: self launch skydiver.. [Re: Dan Barclay [ORG]]
      #225988 - 12/05/08 06:45 PM

Quote:

Does someone want to do the G calculation... acceleration over a 2ft distance to a speed enough to travel some distance (a couple of hundred feet?) in the air.




Time to climb 200 feet = 3.5 seconds

Launch velocity = 113 ft/sec

Acceleration required to attain 113 ft/sec in 2 feet = 3192 ft/sec^2

Ninety-nine G's, dude. And that's assuming it's uniform.

--------------------
Ralph Jones
LS-4a N49LS 6R


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Dan Barclay [ORG]
Top Gun


Reged: 05/06/04
Posts: 4492
Re: self launch skydiver.. [Re: Ralph Jones]
      #226008 - 12/05/08 09:56 PM

Ralph,

Thanks for crunching the numbers. Some time ago I'd have done the ciphering
myself, but I got over that years ago<g>.

>> Ninety-nine G's, dude. And that's assuming it's uniform.

Seems a bit... errr... much, huh?

Order of magnitude check: 200ft/2ft... 100x... 99G vs 1G yea, it's not
tight number but the 99G sure passes the sanity check.

"somebody's gonna get hurt tryin' that"

or

"hey yall, watch this!"

Sadly, somebody somewhere is gonna try it! They're gonna end up with their
shoes up their axx.

Dan


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Stephanie Belser-2
Top Gun APC


Reged: 04/28/04
Posts: 7139
Loc: KFAM
Re: self launch skydiver.. [Re: Dan Barclay [ORG]]
      #226015 - 12/05/08 10:21 PM

Quote:

Order of magnitude check: 200ft/2ft... 100x... 99G vs 1G yea, it's not tight number but the 99G sure passes the sanity check.

"somebody's gonna get hurt tryin' that"

or

"hey yall, watch this!"

Sadly, somebody somewhere is gonna try it! They're gonna end up with their shoes up their axx.

Dan




It would be more humane if the dropped weight just fell on him, I reckon.

--------------------
If you wish to make an apple pie from scratch, you must first invent the universe.-- Carl Sagan


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Ralph Jones
Top Gun


Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Re: self launch skydiver.. [Re: Dan Barclay [ORG]]
      #226023 - 12/05/08 11:06 PM

And as far as the forces on the guy's feet are concerned, you have to add gravity's 1G, so there's an even hundred <g>.

--------------------
Ralph Jones
LS-4a N49LS 6R


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Russell Holton
AVSIG Member


Reged: 07/07/05
Posts: 14136
Re: self launch skydiver.. [Re: Dan Barclay [ORG]]
      #226035 - 12/06/08 03:16 AM

Among the other things that seem wrong is why something subject to the force from a teeter-toter would go straight up.

I think a far more likely outcome is the guy would be thrown some 10-15 feet into the air toward the wright and that board would be snapped in half.


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Dan Barclay [ORG]
Top Gun


Reged: 05/06/04
Posts: 4492
Re: self launch skydiver.. [Re: Russell Holton]
      #226129 - 12/06/08 07:43 PM

>> I think a far more likely outcome is the guy would be thrown some 10-15
>> feet into the air toward the wright and that board would be snapped in
>> half.

Had the board snapped he would have gone to the side, but the premise was
that it did not and was real. The question was IF it were real, what would
the acceleration have been. IF it were real (which it ain't <g>) and the
lift were across the entire range he'd have had (about) a foot of lift below
the fulcrum and (about) a foot of lift above the fulcrum... below going one
way and above going the other, net zero.

Dan


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