Effect of dipping your right shoulder on heading

[460 0]

I'm posting this to provide food for thought. There seems to be a number of misconceptions...

If you jumped slider down and dipped your right shoulder significantly during pilot chute pitch and during the opening, which direction do you think your parachute will open?

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[JaapSuter 0]

Interesting question; I haven't voted yet. I'm actually not sure.

The way to answer this question is to figure out how dipping a shoulder contributes to an offheading. There are three factors I can see.

• The airstream behind the person becomes more assymetrical, although I think this is neglectible on slider down jumps.
  
• The packtray is not presented in a laterally horizontal way, this means your packjob will come out tilted to one side.
  
• One riser is loaded before the other one.

I'm probably overlooking other factors. My gut feeling says that the middle one is the biggest contributor, largely based on my observation that offheadings happen long before the lines are taut, so long before riser-loading comes into play.

[lifewithoutanet 0]

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The packtray is not presented in a laterally horizontal way, this means your packjob will come out tilted to one side.

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largely based on my observation that offheadings happen long before the lines are taut, so long before riser-loading comes into play.

But you must take into consideration other factors that could contribute to this, such as the direction of pull by the PC due to oscillation or wind conditions.

I'm skeptical that the angle will really play as much a factor as you think when the bridle is extracting the packjob from the tray from a single point (except where a multi is in use).

I'd say the direction of pull from the PC would play a greater role than the tilt of the packjob and tray.

-C.

[JaapSuter 0]

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But you must take into consideration other factors that could contribute to this, such as the direction of pull by the PC due to oscillation or wind conditions.

How does dipping a shoulder affect the direction the PC pulls from? The original question asked about the effect that dipping a shoulder has on offheadings. Are you implying that dipping a shoulder affects the angle the bridle bulls at, which in turns affects your heading? I'm skeptical that dipping a shoulder will have much influence on PC oscillations.

[lifewithoutanet 0]

I muddled my point by including that statement. I've since stricken it from the post.

Still, I maintain that if a shoulder is dipped and there is no crosswind or oscillation of the PC as a factor, except in extreme cases (i.e. the shoulder is more than simply 'dipped' a little low), and before line-stretch (in which case loading one riser before the other occurs) the angle of the packtray will have little effect. In cases where it's more than just dipped a little low, I'd worry more about the container distorting the packjob as it leaves the tray than on the simple angle alone.

Am I making sense now?

-C.

[JaapSuter 0]

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Still, I maintain that if a shoulder is dipped and there is no crosswind or oscillation of the PC as a factor, except in extreme cases (i.e. the shoulder is more than simply 'dipped' a little low), and before line-stretch (in which case loading one riser before the other occurs) the angle of the packtray will have little effect.

Assuming you are correct in this (which I'm not convinced of, nor am I of the contrary), then what are you actually contributing the offheading to?

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In cases where it's more than just dipped a little low, I'd worry more about the container distorting the packjob as it leaves the tray than on the simple angle alone.

Hey, I like that one. You mean the side-walls of the container scraping past the packjob perhaps?

[lifewithoutanet 0]

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Assuming you are correct in this (which I'm not convinced of, nor am I of the contrary), then what are you actually contributing the offheading to?

Good, 'cause I'm not convinced either way, either.

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Hey, I like that one. You mean the side-walls of the container scraping past the packjob perhaps?

Yes. I think the angle is only a factor when it reaches a point where a part of the container inhibits extraction from the tray.

However...at terminal or close to terminal speeds, I could see where air slipping between the container and packjob on the side w/ the lower shoulder could effect the heading performance.

-C.

[460 0]

Think about it... It's the tensioning of the right lines prior to the left lines during the initial inflation, IMHO.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[piisfish 135]

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Think about it... It's the tensioning of the right lines prior to the left lines during the initial inflation, IMHO.

That's what I thought about. Right side being tensioned and likely pressurized before the left, therefore it would make the canopy turn left (I think).

But it might also "angle" the canopy more on the right side inducing a spiral to the right...

This is why you should not dip the shoulder

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[TomAiello 25]

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The way to answer this question...

Might not a better way be to just run out and do 20 jumps, dipping the right shoulder intentionally, and see what you observe?

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[lifewithoutanet 0]

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Think about it... It's the tensioning of the right lines prior to the left lines during the initial inflation, IMHO.

Agreed, if the off-heading is not a result of the packjob twisting prior to linestretch.

Jaap hijacked your question and was pointing out examples where the packjob has turned before any input from the riser. I let him drag me down that path.
-C.

[PeteS 0]

I would guess 460 means "all else being equal, what if?" My guess would be "generaly right".

[lifewithoutanet 0]

Agreed. "Right" is how I voted.
-C.

[460 0]

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This is why you should not dip the shoulder

In a John Lennon voice: Imagine being in freefall. At some point before pitch, you realize you're uncontrollably dipping a shoulder. Knowing instinctually which direction you canopy will open will lead you to anticipate which correction should be made once the opening is complete.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[flite 0]

I said to the right, because having one riser group lower than the other equals a banked turn to that side.

[nicknitro71 0]

Dip right go right as far as I know.

Memento Audere Semper

903

[badenhop 0]

Hello,
My experience, all other factors ignored, is a dipped shoulder
at deployment causes the canopy to open in the opposite direction.
Dip your right shoulder, canopy will open to the left.
To really prove the theory, well you can't.
Pilot chutes do stuff.
I don't pack perfectly.
Riser extraction is violent.

==================================

I've got all I need, Jesus and gravity. Dolly Parton

http://www.AveryBadenhop.com

[truckerbase 0]

Ive done this jump several times. Dip your shoulder to the right, open right. Dip your shoulder to the left, open left. However, since the heading isnt guaranteed anyway, its more accurate to say that if you dip your shoulder in a given direction, your opening will be more in that direction on the same jump, pack job, and wind conditions at that exact same moment than if you didnt intentionally drop a shoulder. In other words, if the jump is going to be a 90 left and you dip a shoulder left, youll likely end up closer to a 180, If your opening was going to be a 90 right, and you dipped your shoulder left, than youd have an on heading. You couldnt make an authoritative statement on this question because of heading ambiguity.

Specifically, early on I did a low tower jump with cables, managed to muck up the exit, that I turned 90 degrees left in freefall; I dropped my right shoulder , and got an opening directly away from the tower...

[avenfoto 0]

i once did a high tower jump, (#3)with a serious tailwind, and a no-go tree line a short distace away at 0degrees... i pitched while intentionally dipping way right, and opened directly into the wind...

i believe the wind direction was as much a factor in the opening heading as well as the shoulder however...

[pope 0]

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Knowing instinctually which direction you canopy will open will lead you to anticipate which correction should be made once the opening is complete.

Although I totally think we should use all of our best instincts while we're jumping, my personal belief on each and every jump is that my canopy is only going to open one way... the WRONG way. Early on I had this nugget passed on to me as I'm on top gearing up to make one of my first few tower jumps, going over the jump with a more experienced friend:

Him: So which way is your canopy going to open?"
Me: "That way (motioning an on-headng opening)."
Him: "Wrong."
Me: (looking puzzled)
Him: "You're going to open up with a 180 and line twists, you'll have a couple broken lines and your canopy will be on fire... You ready to deal with that?"
Me: (thinking for a minute) "Yeah, except for maybe the fire part."

I understand the context in which you made the statement, but I think it's important to point out a couple of things:

1. that there are no absolutes on heading performance. All of us have seen (or been) jumpers with good body position, square shoulders, good packjob, and light/varible winds have fucking horrendus openings. I think that by beleiving that you know anything about how those uncontrollable aspects of a BASE jump might play out, you're being complacent.

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anticipate which correction should be made once the opening is complete.

2. You should certainly always read your opening, but in most cases, by the time the opening is complete you should already be well-into problem-solving mode and beginning to make corrections, but again, YMMV depending on your situation. each jump/jumper has their own circumstances.

Not meant as an argument C.S., just adding my own languaging.

cheers,
pope

[460 0]

When I dip my right shoulder, I almost always open to the left. I completely agree with Pope, and I think his advice is pretty good. "No your going to have a 180 with line twists." This sounds like a Mick saying. In actuality, I tend to go more by the tension feel of the risers on my harness to make corrections. 180s, 180s with line twists, slider up line over malfunctions have all been dealt with properly just by going by feel.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[yuri_base 1]

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When I dip my right shoulder, I almost always open to the left.

Since the prevailing experience of others is "dip right - go right", there must be something peculiar about your particular configuration that makes you almost always open to the left.

It would be interesting to find out what exactly causes such consistency and thus better understand the mechanics of offheadings. Could it be caused by your particular canopy, how tight your chest&leg straps usually are, whether your hips are not level when the shoulder dips, etc.?

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[nicknitro71 0]

It's called chaos theory

Given 460's BKG, he could give you some insights.

Edited to add:

That is if you consider a BASE jump a deterministic system. If a BASE jump is a non-deterministic system then we are dealing with quantom chaos.

In the end as 460 pointed out, you'd better using your feel!

Memento Audere Semper

903

[pbla4024 0]

No, it is not.
Chaos theory is about system with:
1) Dense periodic orbits
2) Transitive flow
He was not talking about such system, was he?

Fido

[460 0]

Chaos theory deals with systems that are extremely sensitive to initial conditions, to the point that experiments seem unrepeatable even with what seems to be the same initial conditions. Quantum plays no role here. The so-called butterfly effect though is the idea taken to the wrong extreme. The is something called the KAM theorem that plays a significant role in preventing the butterfly effect from generating a hurricane on the other side of the world.

Keep in mind, it is widely believed by aerodynamicists that the parachute opening is the most complex aerodynamic process known. I try to minimize some of the chance by simply staging my opening. But that's another story. I don't believe chaotic dyanamics play what I would call a major role in the openings, but that's just an opinion.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174