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dthames

Vertical stack spacing/positions

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When flying vertically stacked I have heard the flock plan of the design that the fliers that are above the base, get progressively further forward of the base, based on their position in the stack. For example, moving up from the base the first person above the base might be 3 feet forward, the second person above the base up might be 3 feet forward of the person right below him/her, and so on.

If this is done for aesthetics, that makes sense because that is the desire affect.

If it is done to keep people out of the burble of the one below them, I have some questions.

If the flock is moving at a glide ratio of 1.0, the burbles are trailing the fliers at a 45 degrees angle, or very close to it. This would allow 6 feet tall fliers to move down, directly on top of the person below them to about 6 feet distance before their tailwing started touching the burble caused by the lower person’s head. Most people are happy with something like 8 feet and not as close as 6 feet, so at 8 feet vertical separation, there is wiggle room of about 2 feet behind the tailwing that you can slip back before there is any concern. Even then, you can feel the burble before it has radical effect on your flight and you can (should) push forward to get back in your slot.

So, why is the stepped stack favored over a straight vertical stack with safe vertical distances? Or is it just the people that I happen to be around?
Instructor quote, “What's weird is that you're older than my dad!”

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If you fly 3 feet forward you fly 3 feet from the person below you which happens to be nicer looking AND more fun. Also if you look at flat formations there usually more spacing at the back so a vertical formation usually has more at the top... The more spacing you have close to the base the greater that effect will be so fly closer as a general rule in all situations and you'll be golden ;) Not always that easy though

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A step stack provides more tolerance for the combined effect of the position adjustments everyone makes once flying in slot. It reduces the risk of burbling the person above you or getting burbled by the one below when say, a formation is breathing and everyone is moving as there is more tolerance for forward/backward movement. One positive consequence of this it that it also allows for a smaller vertical separation between rows.

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It also gives the top guys more visual reference on how the stack is behaving. As you cannot see the base if you're directly above it and there's lots of people in between. You should not only be lookin the flyer just below you, but also the flyers below him. This gives you the possibility to smoothen the motions of the stack and not just react to the moving of the guy below you.

"Fear is the path to the Dark side"
(Master Yoda)

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Aesthetics is in the eye of the beholder, no comment.

Practically it gives:

Better visibility

More tolerance for positioning errors

Easier sequential moves.

IMO.
...

The only sure way to survive a canopy collision is not to have one.

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kallend


Aesthetics is in the eye of the beholder, no comment.

Practically it gives:

Better visibility

More tolerance for positioning errors

Easier sequential moves.

IMO.



That ... plus some people prefer stacking as close as possible.
"That looks dangerous." Leopold Stotch

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Butters

***
Aesthetics is in the eye of the beholder, no comment.

Practically it gives:

Better visibility

More tolerance for positioning errors

Easier sequential moves.

IMO.



That ... plus some people prefer stacking as close as possible.

+1 to all above, it also enables the base if back flying to arch on back enabling a higher performance flight and not a de arched position dropping out.
Dont just talk about it, Do it!

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kallend


Aesthetics is in the eye of the beholder, no comment.

Practically it gives:

Better visibility

More tolerance for positioning errors

Easier sequential moves.

IMO.



Tolerance is the main thing here. To the OP: a burble is not a discrete thing that occupies a discrete space. If you are flying directly above somebody, your feet are probably flirting with the edge of their burble at times. That's no fun, nor is it practical.

Not sure I understand the better visibility. The top guy in a perfect vertical stack, or a perfect tilted stack, will in either case see nothing but the guy below him.
www.WingsuitPhotos.com

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"http://www.amazon.com/Wingsuit-Formations-Douglas-Spotted-Eagle-ebook/dp/B00BNHQ9U4"The Book of Wingsuit Formations discusses this at length.

3' is pretty far forward. Kallend lays out the thought well, but I don't think 3' is necessary. Keeping people out of burbles is the goal, and if two bodies are directly aligned, it's easy for one or the other to out/under pace the other and the upper falls into the burble of the lower. Keeping a buffer by upper being slightly forward allows for greater safety, visual, and makes for pretty pictures.

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DSE

Keeping a buffer by upper being slightly forward allows for greater safety, visual, and makes for pretty pictures.



Three people now have said something about better visuals. Can somebody please explain? See attached photo which shows top guy's FOV. He can't see past the guy under him if everybody is lined up. In real life the line won't be perfect, so he will see bits and pieces of everyone else in the stack. But this is no different or better than what he would see in a vertical stack.
www.WingsuitPhotos.com

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IMO, the side visual/aesthetic is better if the stack leans forward similar to a CRW stack.
Yes, if _no one_ is moving, and everything is aligned the top view doesn't see _every_ thing under him. But he surely sees enough to stay aligned. That same argument applies if he's DIRECTLY over someone else too.

And flying behind simply isn't possible. So all things considered, a forward leaning stack is prettier to look at, and provides as much ability to see what's below as any other position.

However, one can also fly half a body length back if he stays aggressive.
https://vimeo.com/21494763

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The bottom person's head at waist or mid chest is idea for a stable stack. With that said, angle, forward speed and suits (both yours and the flier below) all factor into your positioning over a person. Burble position and angle are roughly the same across suits, but some burbles contain better, more stable air flow on some suits than others.

Remember you eye picture is generally higher than what you think you are flying at. Remember back to AFF when you were taught how to flare. Instead of the waiting a second or two, you want to drop a ft or two to get something tight and flyable. Always give yourself an out off to the sides or above when learning.

With that said, I've stacked almost directly over & flew only 1 ft or so on some, but again it all comes down to feeling of the air and the there factors I've mentioned.

Here's one picture of a dual stacked formation from last year:
http://www.wingsuitmedia.com/p54318707/h312E3458#h312e3458



Here's a video I just realize I uploaded a while back of flying a stable stack from PR 08.
https://vimeo.com/36331189

Where is my fizzy-lifting drink?

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