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From: dmason@ecs.umass.edu
Newsgroups: rec.skydiving
Subject: Re: bungee jump from plane
Message-ID: <12490.27c03db2@ecs.umass.edu>
Date: 18 Feb 91 20:48:49 GMT
References: <38P3w3w161w@grafted.UUCP>
Lines: 68

In article <38P3w3w161w@grafted.UUCP>, dappel@grafted.UUCP (Dave Appel) writes:
> to: the genius who wants to bungee jump from a plane.
>  
> Uh, excuse me, but where did you leave your BRAIN?

          Really, not to mention....
>  
> Do you have any idea of the effects that vector forces have
> on an airplane?  Lift, drag, thrust, etc?  Have you ever
> noticed the pilot trying his darnedest to maintain straight
> and level flight with 4 or more skydivers hanging on the
> outside?  Usually causing the CG (center of gravity) to
> be outside of normal limits?
>         
           what about the.....

> First off, connecting the bungee cord to any point other than
> the center of gravity is going to cause the plane to be unstable
> at best, or tumble out of the sky at worst.
> 
            when the, you know........
> SECOND, as each person leaves the plane, the center of gravity
> changes.  Thus the connecting point is going to move.
>  
            It would...you would.....
> THIRD, it would be impossible to connect the bungee to the
> "true" CG, but it would have to be connected to the frame
> or fuselage at the nearest point. Thus, when a force is
> applied on the connecting point, it will cause the plane
> to rotate. Initially in a direction perpendicular to the
> line segment between the connecting point and the true CG.
>  
            ....really messed up......

> FOURTH, the pendulum effect of a mass hanging at the end
> of a long elastic cord is going to cause it to bounce around.
> What effect do you think this will have on the pilot's efforts
> to keep the plane stable?
>  
                  WOW is that dumb!!

> How big a plane did you plan to do this from? I've noticed that
> even when a skydiver shifts his position from sitting on his
> (or her, excuse me) butt to a kneeling position in the back of
> a Twin Beech, that the pilot immediately feels it and has
> to make small adjustments.  Now imagine the torque applied
> by a 200 pound object at the end of a 300 foot elastic cord.
>  
> Maybe, just MAYBE, such a stunt would be possible from a C-130
> hercules, where the weight of one jumper would make only
> a very small difference in the CG.   But anything the size
> of a DC-3 or smaller would be courting disaster.

             O.k., now say this person does get ahold of a C-130,
maybe at Fort Benning,Ga AIRBORNE school, and you do get to jump with
the cord attached. I can tell you right now, when the cord recoils, and you
get slapped across the underside of a C-130, you will be hurtin' 4 certain.
One particular jump I made at AIRBORNE School, I jumped from the door, and a
strap got snagged on a piece of metal, I was left dangling on the outside of the
plane, getting bumped around against the fusilage about a dozen times before
the trainer got me loose. I had bruises for months. Sheeeeeeesh, a bungee cord.

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Don Mason                           \   Send all replys and comments to me
College of eNGinEeRiNg              /     all .sigs on vacation
University of Massachusetts         \          
Amherst                             /
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