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dynamic ws flying
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donkeyboy

Apr 1, 2016, 1:04 PM
Post #1 of 57 (19865 views)
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dynamic ws flying Can't Post

Looking for some insight and advice on this condition:
- I've never experienced it while skydiving, only in base and it only happens when going from best glide or a partial flare to a steep dive , but the whole suit will get a little bouncy from front to back. I was thinking that some air from the forward speed was contacting the top surface because of the steeper angle of attack and causing this ?
( I fly a1 and use very little arm sweep while diving ) thanks

mccordia

Apr 1, 2016, 2:45 PM
Post #2 of 57 (19800 views)
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Re: [donkeyboy] dynamic ws flying [In reply to] Can't Post

The bouncy feeling can come from either physical inputs (you reacting) or due to a loose arm sleeve or general suit fit that causes the arm or leg wing to move seperate from your inputs, causing buffeting. Essentially a flapping airframe.
Imagine doing tight acrobatics with an airplane with 20 cm of 'play' on the ailerons/flaps.

Otherwise there is no reason why a suit cant fly from belly all the way to headdown and back without any buffeting, motion or otherwise issues.

Aside from training (a couple of 100+ skydives vs 'tryig it' in base), I suggest looking at (super)tight suit fit, and no issue with inverting leading edge in flight. As that can also cause sudden drag and unwanted movement during steeper dives.

Training it a lot in the (safer) skydive environment is key to make sure you don't run into trouble...

BASEMenace2

Apr 2, 2016, 6:20 PM
Post #3 of 57 (19481 views)
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Re: [donkeyboy] dynamic ws flying [In reply to] Can't Post

This is called the point of back deflection. Where more air is going over your wing then under it. Learning to fly this point in any big suit stably is important to terrain flying.
You can fly this point with skydiving training.

SLAMBO

Apr 3, 2016, 12:11 PM
Post #4 of 57 (19328 views)
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Re: [donkeyboy] dynamic ws flying [In reply to] Can't Post

If you are concerned about something like this happening while BASE jumping, you should probably skydive some more first man. Fuck around with your suit, do barrel rolls, wing-overs and all sorts of wierd shit until you can do pretty much everything without worrying about recovery.

shortleash

Apr 3, 2016, 1:01 PM
Post #5 of 57 (19316 views)
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Re: [donkeyboy] dynamic ws flying [In reply to] Can't Post

I know exactly what you're talking about, I call it backwinding, which is a sailing term and what basemenace said about more air on the top surface than the bottom. Not many people understand this concept and it's already put some on the bfl. You won't be able to practice it in skydiving because you will never be able to get your speeds as slow as in base. The thing you can practice in skydiving is diving with your head and shoulders and not your arms. It's the same movement you use as when going from belly to head down .This type of dive will keep your speeds high and in reality is your only real "margin". It all comes down to the air pressure on the different surfaces of the suit , when you go from best glide to a steep dive you can increase the top skin surface pressure to exceed the bottom skin pressure ( which is the 'bounce' ) so what you need to do is either a diving start to build bottom skin pressure early or start your dive earlier and slowly to build the pressure more gradually ( as basemenace said to find the point of deflection ) which means planning the line far in advance.

pgpilot

Apr 5, 2016, 12:00 PM
Post #6 of 57 (19000 views)
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Re: dynamic ws flying [In reply to] Can't Post

In reply to:
The bouncy feeling can come from either physical inputs (you reacting)

actually true

In reply to:
or due to a loose arm sleeve or general suit fit that causes the arm or leg wing to move seperate from your inputs, causing buffeting.

Hmm, that is demonstrably False. This is a perfect example of an Orange suit that fits balls-tight losing it in exactly the manner the OP describes, right next to a green suit that fits nice and comfy, forward to the 20 sec mark: http://www.nbcnews.com/...ch-alps-402872387611(it’s worth the wait for the ad, as it is a perfect illustration of pitch instability).

In reply to:
Essentially a flapping airframe. Imagine doing tight acrobatics with an airplane with 20 cm of 'play' on the ailerons/flaps.

A terrible and misleading analogy from an outdated school of thought.

In reply to:
Training it a lot in the (safer) skydive environment is key to make sure you don't run into trouble...

True! Obviously. But that’s just regurgitating the same tired advice through a different blowhole. To frame the above as useful information given in response to what is actually a valid question is not cool, IMO.


Take this free advice for what it’s worth:

What I think the OP is referring to, some people call it speed-wobbles. I’ve heard people say “whomps”. It happens to most of us at some point when pushing our suits steeper, or we feel it coming and then back off before it does happen. The root of it is this:

Every airfoil has a stagnation point. It is where the flow encountering your leading edge splits. Some goes up, some goes down. That point of split moves on the leading edge of the profile as the Angle of Attack changes. There are a lot of variables that influence the movement of the stagnation point (arm and rest-of-body position, flight angle changes), but mainly it is influenced by your AoA.

How does it affect us?
As you adjust your angle, the stagnation point moves on the leading edge of your wing – it moves up, or it moves down. It can move up and down quite rapidly, it turns out. Your arm is the leading edge. If you lower your Angle of Attack to fly steeper, the stagnation point moves higher (toward the top surface of your wing), more flow will end up on the top surface and you will feel your arm be forced quickly “down”. If you make a tiny (or not so tiny) adjustment, the stagnation point can very rapidly end up lower on the LE and then more flow will be on the bottom surface of your suit. If this happens in quick succession, as it often does when learning to fly wingsuits steep and fast, then you will experience what you are talking about and what the orange suit in the video above experienced. The answer to learning steep flight is in understanding the relationship between your leading edge, AoA, flight angle, and how you manage your body movements when you go fast and steep.

As for suit character, and this is a bit more abstract, but people understand it intuitively: the cleaner, harder (as in firm), and more efficient a wingsuit leading edge is, the more difficult it will be to manage at steeper flight paths and lower AoAs (provided it resembles a wing profile). A slightly soft leading edge can actually be easier to fly at the steepest angles than a perfectly hard and smooth one because it is more forgiving of varied arm positions and it is easier to warp your LE into a position that works for you.

As BASEMenace says, learning to fly this “point” in any suit is a real thing that the best pilots spend time on. It’s perhaps the most important thing in learning to fly big suits safely at steeper angles. Over the past few years we have seen the favored technique of terrain flying change from an “arms up and back” very stable (but less efficient) position, to an “arms more level with shoulders” more aggressive position, which Scotty Bob favors. It’s faster, to the point that one guy likes to blame him for speeding up his videos (hilarious), but it is also less stable and requires more practice. The “arms more level with shoulders” is the position we use when racing wingsuits at steeper flight paths.

There are some things to think about that may help: What works for me is trying to not over-tension the suit at the wrist. Pushing as hard as you can into the leading edge of the suit at your wrist will rob you of some sensitivity in your arm wing. Instead, try putting lengthwise tension into the suit higher on the arm and pushing into the leading edge more in the middle of your arm. This should leave your forearm, wrist, and hands a bit more free to deal with the micro-adjustments that you need to make in order to maintain stability and keep the stagnation point more stable in the middle of your leading edge.

Find this point gradually. Try to ease into a steeper flight path and lower AoA very gently, by degrees. When you feel yourself reaching that teetering point, stay fluid in your arms but don’t let off the lengthwise tension of the suit until you have to. Then reset and try again.

If this is occurring from what you think is best-glide to a transition to faster flight, you might be flying much too slowly to begin with. Hard to diagnose from here, but speed is generally the answer to most problems in WS BASE.

The stagnation point is also related to stall. This page has some good explanations, in particular the one from Peter Kampf with accompanying photo of a stall warning vane: http://aviation.stackexchange.com/...ve-stagnation-points That image is useful fuel for a thought exercise. If you imagine how that vane works, and when it activates the alarm, then think about how your suit feels when you’re too flat or head high and slow, you can get a feel for how understanding the stagnation point is relevant at our slowest (near stall) speeds as well.

If you have heard it’s cool to be anti-Bernoulli when trying to understand flight, don’t get too caught up in the fact that the stagnation point is often mentioned in concert with Bernouilli’s Equation. The main point here is how rapid changes in AoA (pilot induced) cause the speed wobbles. Understanding the root cause is the first step in addressing it.

I hope that is of some help.

-Matt

(edited to add attachment)

(This post was edited by pgpilot on Apr 5, 2016, 12:02 PM)
Attachments: stag-point.gif (1.77 KB)

robibird
Phoenix Fly
Apr 7, 2016, 7:49 AM
Post #7 of 57 (18629 views)
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Re: [pgpilot] dynamic ws flying [In reply to] Can't Post

While Matt was being correct on most of the aerodynamics issues in his post, I would like to refer to this paragraph:

“As for suit character, and this is a bit more abstract-----A slightly soft leading edge can actually be easier to fly at the steepest angles than a perfectly hard and smooth one because it is more forgiving of varied arm positions and it is easier to warp your LE into a position that works for you. “

Basically, he is trying to say that loose fit at the leading edge has some aerodynamics advantages, particularly at high alpha (angle of attack, AoA). I would strongly disagree on that. The whole industry that is dealing with semi-rigid airfoils (parachutes, paragliders, WS, and hang gliders to some extent) are constantly striving towards more rigid airfoil, particularly leading edge, in order to get smoother and more predictable airfoil, and as a consequence a desired and predictable airflow, with a final goal of more performance. I have never ever heard that someone is trying to make leading edge softer, and as a result, completely unpredictable in shape, and performance. On the contrary, everybody is trying to improve leading edge shape and pressurization, using different methods e.g. cross bracing, semi rigid inserts (ribs, LE profiles, etc…), in order to get stable airfoil that will have predictable performance in all flight regimes (flight envelope). Having soft, deformable leading edge is just adding more unknown variables to already very complex WS aerodynamics, because the WS as a whole is aerodynamic body that is constantly changing its whole shape during the flight, since flyers are constantly making control inputs with the whole body and all exteremities.

pgpilot

Apr 7, 2016, 10:43 AM
Post #8 of 57 (18531 views)
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Re: [In reply to] Can't Post

I realize that not everyone here speaks english as a first language, and that my post had a lot of words in it. In the small chance that this was a legititmate misunderstanding, and not a case of trying to twist what I wrote, I will point out for you what you missed and / or misunderstood.

In reply to:
Basically, he is trying to say that loose fit at the leading edge has some aerodynamics advantages, particularly at high alpha (angle of attack, AoA). I would strongly disagree on that.

You are incorrect in two ways:

1. I wrote “easier to fly” but you seem to have read “higher performance”. I assume you know the difference. It is a very important distinction in wingsuit flying.

2. You seem to be mixing up high and low AoA, which I’m sure (I hope) you understand, but your mistake may confuse other people reading.
Or I confused you by writing "steep" instead of "low" (AoA is not relative to the horizon), but obviously we are discussing steep/fast flight in those paragraphs.

In reply to:
The whole industry that is dealing with semi-rigid airfoils (parachutes, paragliders, WS, and hang gliders to some extent) are constantly striving towards more rigid airfoil, particularly leading edge, in order to get smoother and more predictable airfoil, and as a consequence a desired and predictable airflow, with a final goal of more performance…

Yeah dude, that’s our industry, and the comp results prove that I agree with you. As you know, in 2015 we made a race suit with a smoother and more rigid airfoil than anyone else’s including (by a large margin) yours, and everyone has seen the results.

Best,

-Matt

cavitator

Apr 7, 2016, 10:56 AM
Post #9 of 57 (18521 views)
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Re: [robibird] dynamic ws flying [In reply to] Can't Post

robibird wrote:
While Matt was being correct on most of the aerodynamics issues in his post, I would like to refer to this paragraph:

“As for suit character, and this is a bit more abstract-----A slightly soft leading edge can actually be easier to fly at the steepest angles than a perfectly hard and smooth one because it is more forgiving of varied arm positions and it is easier to warp your LE into a position that works for you. “



Basically, he is trying to say that loose fit at the leading edge has some aerodynamics advantages, particularly at high alpha (angle of attack, AoA). I would strongly disagree on that. <snip>

Much respect to you Robi but I would strongly disagree! He said that softer leading edges 'can be easier to fly,' which is not at all the same thing as 'some aerodynamic advantages.'

He can answer for his self but to me he means that for people like me with not so much wingsuit experience it can be easier to fly steeper angles than with harder edges... just like regular-pressure canopies are easier for less experienced pilots to control than x-brace canopies which are stiffer. In both case, 'more forgiving' is good for the less experienced until they figure it out. After they do then of course we all want better performance and everything you say about that is true.

thank you both for great comments. I learn a lot from those two posts!

mccordia

Apr 7, 2016, 11:07 AM
Post #10 of 57 (18510 views)
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Re: [cavitator] dynamic ws flying [In reply to] Can't Post

In reply to:
he means that for people like me with not so much wingsuit experience it can be easier to fly steeper angles than with harder edges...

Coaching people fulltime on flying wingsuits from steep to complete headdown and backwards, its especially beginners benefitting from tighter fit and a smooth leading edge. Sloppy response and unpredictable suit behaviour is never in anyones favor, regardless of what marketing tries to tell you.

pgpilot

Apr 7, 2016, 11:24 AM
Post #11 of 57 (18479 views)
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Re: [mccordia] dynamic ws flying [In reply to] Can't Post

I could write that BMW makes low quality cars that drive like shit and have a funny interior smell, but most intelligent people would see that fabrication for what it is: Complete and total bullshit, coming from someone who probably sells Mercedes.

I wish that trying to raise the standard of discussion here wasn’t such a battle. Some people come here to contribute, others come for information, and then there is a tiny-loud group who come here just to spew stinky diarrhea shit all over the place. Two of the three groups are useful.

idemallie
Moderator
Apr 7, 2016, 11:42 AM
Post #12 of 57 (18453 views)
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Re: [pgpilot] [In reply to] Can't Post

pgpilot wrote:
Or I confused you by writing "steep" instead of "low" (AoA is not relative to the horizon), but obviously we are discussing steep/fast flight in those paragraphs.

Could your airfoil orientation be below the relative wind? Is it mechanically possible? Trying to think through it, it takes away any source of lift you have and makes you fall out of the sky, but is that right?

Are you ever steep enough that you aren't trying to get lift and just trying to get max "thrust"? Obviously I have a very limited understanding of wingsuits.

BASEMenace2

Apr 7, 2016, 12:07 PM
Post #13 of 57 (18418 views)
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Re: [idemallie] [In reply to] Can't Post

Ding ding ding ding we have a winner!!!!!!!!

Yes, what the original post was about is this point, where lift from deflection is no longer a goal, and efficient decsent is.
Old school theory will tell you that folding arm wings back is the best stable way to increase speed and decrease angle of attack...diving and gaining power.
However, by maintaining a rigid air foil (stiff arms...whole wing dive), you can build more power and maintain. Treat the entire wing as a diving surface.
The reason this method is not popular is simple...most wingsuit pilots SUCK at freeflying. Most have no knowledge of flying any wing surface other than the bottom on there belly and the top on there back...with very small AOA changes. Maintaining steep angle flight in a big wingsuit is a skill to learn...its doable in all suits, as long as the inlet design allows there wings to stay inflated at those steep angles.
Old designs had major problems with this...leg wing deflations were very common the early days of Brevent...where most really started figuring out multi angle dynamic terrain flying lately.
Proprietary arguments aside...learn to fly steep, learn your recovery arc, learn how your suit reacts to extremely steep angles...and go put it to practice in the sky.
Oh yeah, and try to smile too...this shit is still fun :)

Fledgling

Apr 7, 2016, 2:02 PM
Post #14 of 57 (18303 views)
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Re: [pgpilot] dynamic ws flying [In reply to] Can't Post

pgpilot wrote:
and then there is a tiny-loud group who come here just to spew stinky diarrhea shit all over the place.
You have made more than one post that would slot you into that group. So maybe you could come down of that high horse now.

flydive

Apr 7, 2016, 2:27 PM
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Re: [BASEMenace2] [In reply to] Can't Post

+1

(... as I refill my popcorn for this show)

cavitator

Apr 8, 2016, 2:52 PM
Post #16 of 57 (17941 views)
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Re: [mccordia] dynamic ws flying [In reply to] Can't Post

mccordia wrote:
In reply to:
he means that for people like me with not so much wingsuit experience it can be easier to fly steeper angles than with harder edges...

Coaching people fulltime on flying wingsuits from steep to complete headdown and backwards, its especially beginners benefitting from tighter fit and a smooth leading edge. Sloppy response and unpredictable suit behaviour is never in anyones favor, regardless of what marketing tries to tell you.

Much respect to you too Jarno but you puts words into his post that he did not use; he said a less rigid leading edge mean more forgiving for lower time pilots. That is a very different thing and I wonder if you tell lower time canopy pilots to jump x-brace canopies because 'sloppy response... is never in anyones favor.'

you and robi seem not to understand his English or you twist his words on purpose like politicians. We all trys to learn here, not get in word fights, yes?

For the record, I have a Havok and no Squirrel but Matt say many wise things until someone piss him off, then he says not so wise things too!

mccordia

Apr 8, 2016, 3:31 PM
Post #17 of 57 (17915 views)
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Re: [cavitator] dynamic ws flying [In reply to] Can't Post

cavitator wrote:
he said a less rigid leading edge mean more forgiving for lower time pilots.

Which is still 100% factually incorrect. Regardless of interpetation or 5 languages Robert or myself could read that in. It's simply not ignoring bad aerodynamics, and what the entire aviation, canopy and flight related industry is doing. A completely inverted leading edge, randomly and asymetricly adding drag can never be a positive contribution. Regardless of brand or make. Regardless of experience level.
It can lead to unexpected turns or movement in the worst cases even.

Low time canopy pilots don't tend to jump crossbraced canopies due to them not flying sub 90 sq/ft. But for sure fly much more rigid and responsive student canopies with harder profile and leading edge compared to several years back. And flying and landing those a lot better in comparison as well.

bluhdow

Apr 8, 2016, 3:58 PM
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cavitator

Apr 8, 2016, 4:09 PM
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Re: [mccordia] dynamic ws flying [In reply to] Can't Post

mccordia wrote:
cavitator wrote:
he said a less rigid leading edge mean more forgiving for lower time pilots.

Which is still 100% factually incorrect. Regardless of interpetation or 5 languages Robert or myself could read that in. It's simply not ignoring bad aerodynamics, and what the entire aviation, canopy and flight related industry is doing. A completely inverted leading edge, randomly and asymetricly adding drag can never be a positive contribution. Regardless of brand or make. Regardless of experience level.
It can lead to unexpected turns or movement in the worst cases even.

Low time canopy pilots don't tend to jump crossbraced canopies due to them not flying sub 90 sq/ft. But for sure fly much more rigid and responsive student canopies with harder profile and leading edge compared to several years back. And flying and landing those a lot better in comparison as well.

'Low time canopy pilots don't tend to jump crossbraced canopies due to them not flying sub 90 sq/ft.'

And who is '100% factually incorrect' now (see attach)?

what is that rule? First step to get out of hole is quit digging deeper, yes?
Attachments: velo chart.gif (51.3 KB)

mccordia

Apr 8, 2016, 4:22 PM
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Re: [bluhdow] dynamic ws flying [In reply to] Can't Post

Im kind of missing any mention of squirrel or poorly made suits?
I was under the (perhaps strange) impression it was aerodynamics talk, which applies to every brand. PF had a more loose leading edge in the past vs now. Tony did. Intrudair did. Squirrel did. That new line also features the same tight leading edge improvements, which is why those same words are even more puzzling (and entertaining). The entire industry develops the same direction. Not one brand was singled out in what was written.

I do see a comicly ill tempered rep trying to turn it into something brand related. But popcorn vallue aside, it's not adding much to the initial question and (non branded) discussion.

bluhdow

Apr 8, 2016, 4:25 PM
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surfers98

Apr 8, 2016, 4:35 PM
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Re: [mccordia] dynamic ws flying [In reply to] Can't Post

Jarno, I think what Matt and Scotty are referring to is simply that a more flexible leading edge allows the pilot to manually induce some degree of washout by slightly twisting his arms, which at high angles of attack can help increase stability, and thus prevent radical back deflection. I'm guessing that's why Suirrel still offers the Aura 2 in an all glideskin version (or maybe I'm the only one who reads the fine print).

I don't think anybody is denying that a more rigid airfoil is more 'efficient' or 'faster'.


(This post was edited by surfers98 on Apr 8, 2016, 4:36 PM)

mccordia

Apr 8, 2016, 4:36 PM
Post #23 of 57 (10909 views)
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Re: [bluhdow] dynamic ws flying [In reply to] Can't Post

bluhdow wrote:
You weren't referring to the suit design there? Is that what you're suggesting?

Correct. I was refering to an issue with a loose fit on the sleeve or entire suit. It was never a complaint about design. At PF we have also modified clients suits for this in the past. Baggy fit. Be it measurement or 2nd hand purchase related. And I know other brand users also returning suits due to ill fit for whatever reason. Its a very valid thing to check. Not cause for starting a war.

Try reading the same thing again, without the anger, and you'll see its normal sane advice on what to check. Things that can be 'a' cause of instability issues.

unclecharlie95

Apr 9, 2016, 9:37 AM
Post #24 of 57 (9955 views)
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Re: dynamic ws flying [In reply to] Can't Post

Remember something - we are all men who wear plastic dresses.

jpengel

Apr 9, 2016, 2:33 PM
Post #25 of 57 (9532 views)
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Re: [surfers98] dynamic ws flying [In reply to] Can't Post

Are you trying to add basejumper.com & WS manufacturer litigation to your CV???

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