The mechanics of swooping and speed/was "Valkyrie 67 demo first jumps"

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While reading the thread "Valkyrie 67 demo first jumps", started by Charlie Mullins, I began thinking about the mechanics of swooping and canopy speed. I notice that many people questioned Charlie's technique of reversing the turn during the swoop.

I have "swooped" considerably in the past, but my techniques would be called "old school" at this point in time, so I am asking for the thoughts of swoopers who use what would be called more current techniques.

I make this explanation because my questions might otherwise seem rhetorical or smart-ass, but they are not. I am asking them hoping to discuss technique and the physics of the swoop.

So here we go:

May I assume that the main/only reason for using a turn (other than for alignment) while swooping is to gain speed? If you could gain speed in another manner (and use turning only to align the landing), would this be desirable? (In other words, if you had a "magic handle" that could do that.)

May I assume that swoopers at times during the phase of gaining speed may be pulling on one front riser or both?

(Assuming a front riser turn) I think that we can all agree that when the rate of turn is reduced by reducing how much the riser is pulled, that the speed will begin to bleed off. Right?

The amount that a front riser can be pulled is limited by some things, 1.) the distance that the jumper can actually pull it, determined by things like the length of their arms and the length of the risers, etc., and 2) how far a riser/risers can be pulled without collapsing the canopy, and of course 3.) riser pressure.

And after all of those questions... Phew!

Is it possible that the bleeding off of speed when reducing the amount of (one) front riser, can be reduced by always pulling on at least one of the risers? (In other words, maximum pull on one riser, transitioning to partial pull on both risers, then transitioning to partial pull on the opposite riser.)

I am assuming that maximum pull on a riser cannot be maintained 100% of the time because the jumper must use some of this time to align for the landing.

Or to ask a simpler question, are we sure that the technique of reversing the turn during the swoop is really all that inefficient? How do we know? Can we use instrumentation to collect data to prove or disprove this?

By the way, one reason that I can think of for reversing a turn would be that it might reduce the possibility of vertigo caused by a prolonged turn affecting the inner ear. (This would of course be highly variable among different people, and may affect so few people that it could be disregarded.)

[raymod2 1]

I think people are questioning Charlie's technique because it is unfamiliar. I don't see any reason why reversing your turn direction would be especially counterproductive. There may or may not be a dip in vertical speed during the reversal but even if there is that doesn't mean the technique is disadvantageous. Most GPS data I have seen of turns larger than 450 degrees the vertical speed plateaus well before the rollout or there is a phase where the vertical speed drops and is rebuilt before the rollout.

Regarding your questions about front riser input: I submit that riser length and arm length have nothing to do with how much riser input you can generate. You are not pulling the riser down to you - you are pulling yourself up to the riser. Once you have put all your weight on your front risers you are accomplishing nothing by pulling yourself higher other than getting into a tucked body position to reduce drag. At any rate some pilots use front riser input and some don't. There doesn't appear to be a distinct advantage one way or the other. Modern canopies will dive very hard with just a little harness input.

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raymod2

I submit that riser length and arm length have nothing to do with how much riser input you can generate. You are not pulling the riser down to you - you are pulling yourself up to the riser. Once you have put all your weight on your front risers you are accomplishing nothing by pulling yourself higher other than getting into a tucked body position to reduce drag.

Understood. I had forgotten that sometimes the force of lift on a riser or risers is greater than the jumper's weight.

[danielcroft 2]

Best bet would be getting a flysight and do some testing on what actually happens when different turns are performed. You'd probably want to average in a statistically significant way to figure out if one was "better" than the other. You could see in each swoop whether the turn decelerates and if the switch in direction has an effect.

I've been wanting to get one for myself so that I can see what I'm doing and where my technique can change and improve.

[DocPop 1]

My understanding of this (as very much an amateur) is that the ideal turn is one which builds steadily to canopy terminal velocity.

The turn is used to change the angle of the lift vector as far away from vertical as possible so that it is reducing that terminal velocity as much as possible.

Bigger turns make for harder accuracy when trying to hit gates and are, therefore, a necessary evil rather than a desired part of the swoop.

If the above is correct then the "reverse turn" fails in that it does not steadily build vertical velocity as when the turn direction is reversed, the canopy will start to recover and some element of the dive will be lost.

It may be that in the hands of a pilot who is not experience in bigger turns, the easier accuracy of two smaller turns tacked together outweighs the disadvantage in gaining speed.

Just my thoughts on the subject. I'd like to hear from someone who teaches CP.

Ian? Brian?

"The ground does not care who you are. It will always be tougher than the human behind the controls."

~ CanuckInUSA

[raymod2 1]

What is an ideal turn? Reaching maximum velocity with minimum rotation from the lowest possible height? You can hit peak vertical speed with a well executed 450 degree turn from as low as 1200 feet. So why do some pilots use a 630 or 810 degree turn from as high as 2000 feet?

There are other considerations when choosing a turn besides building speed most efficiently. I disagree that bigger turns make it harder to hit gates. To the contrary a bigger turn allows more opportunity to adjust and can be more accurate than a smaller turn.

[stayhigh 2]

the phi ratio; fibonacci spiral = maximum swoop.

imagine if you can stretch the finonacci spiral vertical and make it 3D? that is the nature's intended swoop path.

Bernie Sanders for President 2016

[DocPop 1]

raymod2

What is an ideal turn?

I'd say that would be the one that allows you to carry maximum speed through the gate, and with maximum accuracy.

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So why do some pilots use a 630 or 810 degree turn from as high as 2000 feet?

I don't know the answer to that? Could you explain it?

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I disagree that bigger turns make it harder to hit gates. To the contrary a bigger turn allows more opportunity to adjust and can be more accurate than a smaller turn.

The bigger turn also means that you are more subject to drift and may HAVE to adjust. Adjustment is something that you are doing to correct something that has deviated from the ideal, and is therefore performance-sapping.

I should re-iterate that I am not posting the above as fact, merely as my understanding of the situation.

"The ground does not care who you are. It will always be tougher than the human behind the controls."

~ CanuckInUSA

[Pablo.Moreno 0]

Not a full explanation on the whole thing, just my experience, also my English sucks.

When I am at the right altitude and can do my 10 second dive for a 270, I accelerate enough to make my audible believe I am back into freefall.

Now, when I am a bit lower and do a quick snappy 270, guess what, I don't build enough speed for my audible to go off.

This means that hitting terminal speed depends solely on how long you dive your canopy with the right diving technique, and the minimum time/rotation to hit terminal in a crossbraced canopy loaded 2.2 ish and up would be a 10 sec for a 450, ( According to few canopy courses)



Now writting about I am thinking maybe because on the slow 270 I am losing more altitude where on the snappy 270 I am losing less altitude and that's why my audible goes off...

Either way, I think if you are able to change the rotation of your turn with out slowing your terminal speed, you would be able to build the same amount of power on the recovery arch.

I fly a JVX 94 loaded at 2.5-1 I never looked at my speed, but when I was doing drills when got this canopy, I remember being able to change the rotation while on a step dive with out getting the feeling of slowing down.

Damn you internet... Now I have to try it and check it out.

[skydivebb 0]

stayhigh

the phi ratio; fibonacci spiral = maximum swoop.

imagine if you can stretch the finonacci spiral vertical and make it 3D? that is the nature's intended swoop path.

Can you explain more on this?

Facebook.com/SeamlessRigging

[stayhigh 2]

it is just some bullshit that I came up with after reading, "The Da Vinci Code".

The book made me curious about the Fibonacci sequence and numbers, and I was researching it, and one thing lead to another I ended up staring at the picture of Fibonacci spiral.

As I'm looking at the spiral, and I was thinking, "That's looks like a perfect swoop path."

And when you take a look at the spiral, every 90 degree turn gradually gets tighter after another, according to the "golden ratio".

This golden ratio has significance, as it applies to architecture, cosmetic surgery, sun flower seed formation, the way your ear is shaped, ect....

Bernie Sanders for President 2016

[ianmdrennan 2]

Jay, who revolutionized how we do hp turns, based his technique off of that sequence

Performance Designs Factory Team

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ianmdrennan

Jay, who revolutionized how we do hp turns, based his technique off of that sequence

Ian, please bear with me as one who does not know everyone or everything about really high performance swooping...

Jay who?

In what way did he revolutionize high performance turns?

And, I'm thinking back to my original questions and assumptions. To what extent does changing the turn direction have on the swoop, and how do we know?

[stayhigh 2]

I remember searching dz.com for phi ratio and swooping couple years back and was surprised to see Jay's post and his theory matching mine.

His post and theory was up here, but I can't seem to search for it.

Also he said something about how the swoop should look like water draining down the toilet bowl.

Starts out big and slow, and accelerating as it spins faster and tighter.

My theory came about after reading the Da Vinci Code and little more than 8th of mushroom. I wonder how JayMo came about with his theory....

kinda cool no? How you can apply golden ratio to skydiving.

Bernie Sanders for President 2016

[Skydivesg 7]

Gary - Ian is talking about Jay Moledski. He blazed the trail in CP for many years while others played catch up using his techniques. He was one of the originals on the PD Factory Team.

Be the canopy pilot you want that other guy to be.

[stayhigh 2]

found something.

study of raptors and its logarithmic spiral flight

Having their most acute vision towards the side causes a
conflict in raptors such as falcons, which dive at prey from
great distances at high speeds: at a speed of 70 m s−1,
turning their head sideways to view the prey straight ahead
with high visual acuity may increase aerodynamic drag by
a factor of 2 or more and slow the raptor down. Raptors
could resolve this conflict by diving along a logarithmic
spiral path with their head straight and one eye looking
sideways at the prey, rather than following the straight
path to the prey with their head turned sideways. Although
the spiral path is longer than the straight path, a
mathematical model for an ‘ideal falcon’ shows that the
falcon could reach the prey more quickly along the spiral
path because the speed advantage of a straight head more
than compensates for the longer path.

more here.
http://jeb.biologists.org/content/203/24/3745.full.pdf

So I guess it isn't quite the Phi ratio.......

Bernie Sanders for President 2016

[skydivebb 0]

Interesting article. Some gems in there about the drag coefficients and greater speed thru the logarithmic path.

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[Rad 0]

Since a canopy (at least not the ones we are talking about) don't have motors there is only one way for it to generate speed. That is to trade altitude for airspeed. A canopy has a terminal velocity just like your body. And just like your body you can adjust "angle of attack" to increase or decrease terminal velocity. AOA is not technically correct but I'll use it here anyway. To increase speed to the maximum potential you need to increase AOA to the max I.e. belly to earth and you need to keep this attitude until you reach the terminal velocity for a specific canopy, wing loading, etc. So you can do a Joe Kittinger hop and pop and do 42 million degrees turn at x AOA and you will never go any faster. (Actually you will slow down but that is another topic). Additionally you can do the hardest turn possible but if you are not at that AOA long enough to reach terminal velocity you are also not max performing the canopy.

So to get the maximum speed you have to hit the maximum AOA AND keep it there long enough to achieve terminal. Reversing a turn can slow you down but if you keep the same angle it won't. That means turning very hard and having good altitude judgement obviously.

Caveat... A reversal probably does create enough turbulence to slow you down some. This should be able to be overcome by a long enoug turn. However, the transition from rear risers to toggles has this same effect. To what degree I have no idea but it does have an effect. To counter this I would love to see a better brake line designed.

One other thing. If you turn hard enough to get your body above the canopy in theory you should increase your vertical speed because your lift vector is now pointing at the ground. The vertical speed obviously will translate into forward speed. Personally I think this is where a reversal works in your favor. To me it just seems easier to really turn hard in a reversal. I think it has to do with riser pressure and the fact that after 90-180 degrees worth of turn in one direction you know how your canopy is performing in a certain condition and you can really judge altitude loss. And you are over your spot already so a hard turn at this point keeps you more or less where you want to be.

My .02c

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Rad

My .02c

I think we got a lot for our 2 cents. Thanks for your thoughts on the subject.

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If you turn hard enough to get your body above the canopy in theory you should increase your vertical speed because your lift vector is now pointing at the ground.

Makes me wonder how often a person gets their canopy into that configuration. We have seen plenty of pictures of canopies that look like they are doing exactly that.

[BMFin 0]

Rad

If you turn hard enough to get your body above the canopy in theory you should increase your vertical speed because your lift vector is now pointing at the ground. The vertical speed obviously will translate into forward speed. Personally I think this is where a reversal works in your favor. To me it just seems easier to really turn hard in a reversal.

Interesting stuff. Your point about the lift vector makes sense if you ment to say that the lift vector in this case is pointing horisontally in a slightly downward angle. (not towards the ground)

However, I wouldnt agree this could be better utilized with the reversal technique. On the contrary, I would suppose the reversal technique makes you loose this optimal pilot-canopy orientation for a brief moment once you make the change in direction.

My gut feeling would say that the techniques mentioned in this thread earlier – turning on a spiral that goes tighter at the end – would be the most likely to 1) keep you slightly above the canopy 2) transalate the centrifugal force into a faster downward speed through the slightly downward angled lift vector. -> so the faster your turnrate eventually builds up, the more you can utilize this downward lift vector.

Im no way near a competitive swooper, but in theory I understand "the extra snap" you get when your last turn is rather fast and you hit it well enough. Perhaps this is where it comes from.