Cutaway cures spin?

[fonz 0]

There's been a discussion going on over at the dutch forum for a while and I'm curious about what you people here at dz.com think about it.

Question is: if you have a violently spinning mal on the main, will you stop spinning once you have cut it away (cleanly, no hangups)?

My educated guess is that you'll get slingshot away in a straight line (the canopy no longer pulls you in a circular motion and you leave along the tangent) but depending on the situation your body itself might still be rotating.

Alphons

And five hundred entirely naked women dropped out of the sky on parachutes.
-- The Hitchhiker's Guide to the Galaxy

[Zeppo 0]

I think it's simply physics. It takes an external force to keep an object spinning in a circle. Like a weight attached to a string spinning around your head. The weight always wants to go in a straight line, however, the string keeps pulling it in, suddenly remove the string, and the weight will go in a straight line.

Same with a canopy. If you have a clean cutaway, then any sprial that the malfunction put you in will end.

One thing to consider though is that your body may still be rotating, yet still travelling in a straight line.

So pretty much, just as you said. High School physics, and the laws of centripetal force.

http://en.wikipedia.org/wiki/Centripetal_force

What goes up, must come DOWN!!!

[fonz 0]

reply]I think it's simply physics.

[Gene03 0]

Isn't Wikipedia a little back-asswards on that one?
Even though it has some impressive math to a moron like me, I wouldn't trust it for answers on a college final.

“The only fool bigger than the person who knows it all is the person who argues with him.

Stanislaw Jerzy Lec quotes (Polish writer, poet and satirist 1906-1966)

[Zeppo 0]

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Maybe not entirely. Some people have reported that it felt like they left in a curve rather than a straight line. I think that's mainly a matter of desorientation, which is physiology rather than physics.

But I do believe we're on the right track: the jumper's body moves in a straight line but might still be rotating around itself.

Thanks,

Alphons

It could also be possible that they are curving, depending of their speed and their body position to the relative wind. If they're going fast enough, then the wind will definitely have an affect on their trajectory.

What goes up, must come DOWN!!!

[fonz 0]

Haven't checked it out yet. I like to think that I know my physics, having been to university and all.

But I'll have a look at it.

Alphons

And five hundred entirely naked women dropped out of the sky on parachutes.
-- The Hitchhiker's Guide to the Galaxy

[fonz 0]

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It could also be possible that they are curving, depending of their speed and their body position to the relative wind.

I think you're right. But I also wouldn't want to rule out the possibility that desorientation merely makes you think you're carving when you're not. Or that you try to fly straight, but your brain is temporarily confused about what is straight.

I think that both theories (body position plus wind versus the brain stuff) can apply. Possibly even at the same time.

Alphons

And five hundred entirely naked women dropped out of the sky on parachutes.
-- The Hitchhiker's Guide to the Galaxy

[Nutz 0]

I can say from experience that the spinning stops. The reserve has line twists though.

"Don't! Get! Eliminated!"

[marks2065 0]

with a good arch and no rsl no problem - but with a rsl will definately have line twists on the reserve

[spoons 0]

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with a good arch and no rsl no problem - but with a rsl will definately have line twists on the reserve

I don't think definitely, but maybe it is more likely...I know of people who have not had twists (even when jumping smaller and more highly loaded mains [and reserves]).

I guess a lot depends on body position on deployment (of reserve).

[DJL 232]

I'll let Kallend set this right since he teaches this shit but your center of mass will continue in a straight line. You will continue to rotate because at the point you are released your feet are travelling faster than your head through the arc of your rotation in the original spin.

Furthey Hypothesis:
You'll probably spin into your reserve lines because of the mechanics of where the lines are attached.

"I encourage all awesome dangerous behavior." - Jeffro Fincher

[spoons 0]

Ah, that kind of makes sense - although I'm not sure if it would be enough to make you continue rotating by much...anyway, I'll leave this up to others to discuss

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[wmw999 2,121]

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with a good arch and no rsl no problem - but with a rsl will definately have line twists on the reserve

Not necessarily. I've cut away two spinners, with an RSL, and haven't had line twists on my reserve.

Wendy W.

There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown)

[SkymonkeyONE 3]

When I have chopped from spinners, I have been spit straight backwards. However, I have seen plenty of video of people getting shot away, spinning like a ragdoll.

[DJL 232]

I'm sure you could google calcs for figuring out tangential velocity but you'd have to make a lot of assumptions about the radius of the circle and angular velocity. No, it probably wouldn't be much and someone's body position would have a more immediate affect.

"I encourage all awesome dangerous behavior." - Jeffro Fincher

[marks2065 0]

or the reserve pack maybe it would have had line twists on a normal deployment - my chop on a barrowed gear with a rsl had several twists

[dragon2 0]

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with a good arch and no rsl no problem - but with a rsl will definately have line twists on the reserve

Not necessarily. I've cut away two spinners, with an RSL, and haven't had line twists on my reserve.

Wendy W.

Ditto.

ciel bleu,
Saskia

[Gene03 0]

Centrifugal force;
The force which to make a rotating body move away from the center of rotation: it is due to inertia.
Think centrifuge.

Centripetal force;
The force tending to make rotating bodies move towards the center of rotation.

(From the Webster's New Universal Unabridged Dictionary, Second Edition)


Visualize this example.
A common ceiling fan in a large room free of obstacles.
Secure a, let's say, one foot length of fishing line to the end of one of the fan blades.
Attach a fishing weight to the free end of the line.
Turn on the fan and observe.
What will happen to the weight?

Same fan, same weight (mass), but lengthen the fishing line to 5-6 feet in length.
Turn on fan and again observe.
What will happen to the weight this time?

Wiki defines centrifugal force as a fictitious force.
How can it be fictitious if it is observable and repeatable?

Maybe I'm confusing common, everyday use with the pure science?

“The only fool bigger than the person who knows it all is the person who argues with him.

Stanislaw Jerzy Lec quotes (Polish writer, poet and satirist 1906-1966)

[The111 0]

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Wiki defines centrifugal force as a fictitious force.
How can it be fictitious if it is observable and repeatable?

Because the definition of fictitious force is not "unobservable and unrepeatable."

www.WingsuitPhotos.com

[billvon 2,400]

> Centrifugal force;
>The force which to make a rotating body move away from the center of
>rotation: it is due to inertia.

It's not just due to inertia; it IS inertia. What we call centrifugal force is inertia in a spinning system. It's not a separate force.

[DrewEckhardt 0]

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Question is: if you have a violently spinning mal on the main, will you stop spinning once you have cut it away (cleanly, no hangups)?

Yes.

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My educated guess is that you'll get slingshot away in a straight line (the canopy no longer pulls you in a circular motion and you leave along the tangent) but depending on the situation your body itself might still be rotating.

You're going to go in a straight line, in whatever orientation you were during the spin, and may get a little angular velocity from the risers not releasing at the same time or aerodynamic forces.

[Pulse 0]

I tend to think we're over-analyzing the common sense.

No....as was stated, the center of mass would travel in a straight line. But the jumper's body may spin, it may stabilize. But that's a different matter.

The fact that jumper's may feel they are falling away in a 'curve' would have more to do with their instability and possibly inner-ear workings. The fact is, at that moment they are not in the best situation to truly realize what kind of trajectory they have.

I suppose it would be plausible that the jumper's body position could fling them into a curve. But think about it. The conditions would have to be sooooo perfect that I doubt it would ever happen. The aerodynamic forces from the jumper's body would have to cause enough force to offset the momentum causing him to go in a straight line.

I don't know if I'm clear about what I'm saying. But no, the jumper may spin. But his trajectory, when viewed from above, will be in a straight line.

"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

[Gene03 0]

Thanks Bill,
I read that Wiki site 3 times and still couldn't get my apes' brain around it.
Back to my other post, what would happen to the weight on the long line?

“The only fool bigger than the person who knows it all is the person who argues with him.

Stanislaw Jerzy Lec quotes (Polish writer, poet and satirist 1906-1966)

[Gene03 0]

Douhhhh, didn't realize the blue words were links.

“The only fool bigger than the person who knows it all is the person who argues with him.

Stanislaw Jerzy Lec quotes (Polish writer, poet and satirist 1906-1966)

[D22369 0]

I have had one cutaway on a stiletto and had no time to delay after the chop (got out at 1800' and took a 5 sec delay) had no line twists on the reserve. it felt like it tossed me straight out from the center of the spin.

Roy

They say I suffer from insanity.... But I actually enjoy it.