How winds affect canopy flight...

[marks 0]

  Quote

I did not read this whole thread as I've seen this discussion far too many times. The question has nothing to do with aerodynamics, it is basic relative motion, from high school physics. But I thought of a way to explain it that maybe has no been suggested yet.

Imagine you are standing on the ground in a 20mph wind. Let's call this "condition A".

Imagine you are standing on the ground, there are no winds, the ENTIRE surface of the earth (including trees, buildings, and all) is somehow moving like a conveyor belt at 20mph. Let's call this "condition B".

Could you tell the difference between A & B? No, you could not. In both instances, anybody on the ground would say "there is a 20mph wind today".

Now, imagine you go make a skydive, on a no wind day. Little do you know it, but the surface of the earth has turned into a conveyor belt while you were on the airplane. You exit, deploy, and are flying your canopy in "no wind" (condition B), and yet everybody on the ground swears there is a 20mph wind! Will your vertical speed somehow be magically altered during turns? Nope.

(You will have a fun time landing on that speeding conveyor belt if you don't fully understand relative motion, but the point I was trying explain had to do with vertical speed - even during turns - being independent from horizontal wind speed).

EDIT: I see the poster directly above beat me to it.

that is a very good analogy.

It is very basic, but it is hard for some people to understand. thats where analogies come in, they help people use a different train of thought to understand.

the fact remains that you have to have an open mind to be able to accept something you don't understand. hopefully your analogy will help clear the air, for those that are open minded to it.

• Quote

[hparrish 0]

I may not understand the physics of all this, but I do understand that when winds are high and I set up my 270 at 800 feet i come out way too high, and when i drop it down to 500 -550 Feet, i'm hitting the gates and landing perfectly.

Maybe I'm defying Physics, but that's what's happening. We can discuus it at the Wicked Liquid Swoppers Boogie.

I'm not too good at visualizing written explanations, I have to see what your talking about.

[Pendragon 1]

I think what's happening is that, due to the wind pushing you back, the arc looks much steeper than in nil wind conditions. As a result, you may be tempted to tighten and quicken your turn, reducing the amount of altitude loss.

I would assert that it is your interpretation of how the set-up is progressing (am I too low etc?) and subsequent reactions that cause you to make inputs that reduce the overall altitude lost, rather than anythng directly to do with wind action on a canopy.

--
BASE #1182
Muff #3573
PFI #52; UK WSI #13

[marks 0]

the thing is, if your eyes, "perceive" that your low, you will add input to correct it, sometimes even without realizing it.

peeps adding input to reduce their arc, is one of the most common things I see peeps do wrong.

  Quote

I think what's happening is that, due to the wind pushing you back, the arc looks much steeper than in nil wind conditions. As a result, you may be tempted to tighten and quicken your turn, reducing the amount of altitude loss.

this is also very common.

[frost 1]

  Quote

when i drop it down to 500 -550 Feet, i'm hitting the gates and landing perfectly.

Lets wait for the gurus of swooping to tell you that you are too low and are doing something wrong. May be you'll learn something, but you'll have to keep an open mind. Forget what your neptune is telling you - they know better.

[ntacfreefly 0]

  Quote

Lets wait for the gurus of swooping to tell you that you are too low and are doing something wrong. May be you'll learn something, but you'll have to keep an open mind. Forget what your neptune is telling you - they know better.

No-one is saying that he can't turn at that altitude and have a good swoop. What they're saying is that he cannot turn exactly the same way without being low/high.

Has nothing to do with anyone being a 'self professed guru' and everything to do with aerodynamics.

Unfortunately, in this case, the sentiment is simply incorrect and no amount of debate can change that.

Blues,
Ian

To the mind that is still, the whole universe surrenders. ~ Lao-Tzu

It's all good, they're my brothers ~ Mariann Kramer

[f94sbu 0]

How much do you adjust your point of initiation in high winds? If you initiate at the top of the gates (where I usually initiate) and the winds are strong, this will push you away from the gates much more than during a no wind day. And since my visual of the gates is changing, this will make me wanting to turn back into the gates much quicker than I normally do. This quickens the turn and changes the altitude loss. Have someone video you during a no wind day and a windy day and compare the video. If there is the slightest difference in time between initiation and when you are finished with the turn this means that the loss of altitude will be different. This may explain it abit clearer to you since then you will really have something to reference between.

rgds,
Stefan

[frost 1]

If one chooses to think of the wind as homogeneous mass of air from the physics point of view where the wind is strictly parallel to the ground... then it works as designed. I don’t think anyone was arguing with that.

But in reality, when is wind ever straight forward and parallel to the ground? So if you allow for the fact that it alters your flight IN RELATIONSHIP to the ground horizontally, then why not accept that it can alter your flight vertically IN RELATIONSHIP to the ground? Since the wind is not perfectly parallel to the ground, it will carry you vertically into or away from the earth. If you think of it as 2-D flight, you won’t see it, but in 3-D it will be a different story.

[frost 1]

I was being as sarcastic as i could without putting a gay smily at the end of my post

  Quote

No-one is saying that he can't turn at that altitude and have a good swoop. What they're saying is that he cannot turn exactly the same way without being low/high.

Must i go and quote another thread?

  Quote

Has nothing to do with anyone being a 'self professed guru'

It has EVERYTHING to do with that.

[Pendragon 1]

Oh absolutely - of course the wind could also be moving upwards. How else could I ridge-soar in my hang glider?

However, you need a hill in order to deflect the wind and cause it to move upwards (or rising air in a thermal, or wave effects [marked by lenticular clouds])...

... but we're not talking about swooping the pond in the middle of hills on a particularly thermic day when a cross-valley breeze has set up nice wave too. In general, we're thinking about fairly level, unobstructed fields - and that's because we're considering the aerodynamics of the wing, rather than what the airmass is doing relative to the ground.

Wind will absolutely have an effect on swooping; the point of the set up, the perspective of the ground during the turn etc. It's just that, aerodynamically, it doesn't make any difference. Wind does not turn a canopy or keep it in a dive any longer. The initiation altitude should be the same (if you do everything the same).

I don't consider either myself or anyone else who's contributed to this thread as a self-appointed guru. I just think the quality and logic of any answers and/or questions will bear through.

If someone has a good argument against what I have just said, please let that person stand forward and write - I would like to hear what they have to say.

--
BASE #1182
Muff #3573
PFI #52; UK WSI #13

[The111 1]

  Quote

If one chooses to think of the wind as homogeneous mass of air from the physics point of view where the wind is strictly parallel to the ground... then it works as designed. I don’t think anyone was arguing with that.

But in reality, when is wind ever straight forward and parallel to the ground?

Now, I'm not a self-proclaimed guru of the English language, so I looked up the word "wind" in the dictionary.

wind
n.
1. Moving air, especially a natural and perceptible movement of air parallel to or along the ground.

The title of this post is "how winds affect canopy flight". The answer is succinct: constant wind affects groundspeed but not descent rate.

Not only are you turning the argument a bit semantic by redefining the word "wind", you are also changing your position drastically from your original post, where you claimed that your canopy is exposed to more wind during a turn and that would change the way the canopy flies (which clearly implies you were talking about horizontal air movement - how would turning expose more wing to vertical air movement?). Now you are talking about updrafts pushing you up/down. Well of course they will. But I for one am a bit curious how an updraft hits your topskin.

www.WingsuitPhotos.com

[frost 1]

It's great that you paid such attention to the original post! Did you happen to see the one where i was saying that i was simply raising a discussion? and that I've read the theory, understood it and now simply was questioning it? I was hoping that was still the best way to learn.

It isnt warranted being talked down to like a clueless AFF student... There are different ways of relaying information and that way is the least productive one. Someone can be providing most excellent info but if presented in such manner it will generate nothing but rejection - the opposite of what was intended by the speaker. This is not directed at you personally, just a general comment.

If I am saying something that differs from my original post, that is simply because I dont really have a solid position on this and am trying to determine the reason why I find myself having to make a quicker turn in higher winds or using toggles to come out of a dive. Thats all.

BTW, I am not an english language guru either - it is afterall my second language. But i think this topic is definitely getting semantic. And redundant.

[The111 1]

I was not intending to talk down to you. Gotta have a thick skin in this sport and on these forums, you should know that.

  Quote

If I am saying something that differs from my original post, that is simply because I dont really have a solid position on this and am trying to determine the reason why I find myself having to make a quicker turn in higher winds or using toggles to come out of a dive. Thats all.

I think Pentagram (Dr. Parkin) has offered the best explanation, and the only explanation - you are varying your rate of turn, initiation altitude, or some other relevant variable, due to your perception of movement (groundspeed).

P.S. You speak English very well for a second language, I would not have guessed.

www.WingsuitPhotos.com

[marks 0]

I'm not so sure why you think others, or me are talking down to you. is it possible you didn't understand something in the english?

you type english well so i would have never known you used english as a 2nd language.

but I will highlight one thing for you.

your perception to the ground changes when there is wind, if your flying downwind, to say do a 180, it is going to seem like you cover more ground "because you are" so you feel like you have to turn faster. but relative to the wind, it is all the same. so you really don't. you only do because your trying to land at a fixed point. not one that is moving with you. that is most likely why you have to turn higher.

and if you add inn turbulence, updraft, rotors, thermals, or changing in the speed of the wind. then it gets a whole lot more complicated.

your probably flying the canopy different without even knowing it.

and please, take this post, as it is... for what its worth. all or nothing.

[dharma1976 0]

mr mike speaks better english than me most of the time...

and its funny but perhaps I will throw more into the mix...

perhaps when it is windy the density altitude changes due to a pressue system change occuring which would add to said same altitude change

Cheers

Dave

http://www.skyjunky.com

CSpenceFLY - I can't believe the number of people willing to bet their life on someone else doing the right thing.

[frost 1]

i speak good

[dharma1976 0]

hella good baby

Dave

http://www.skyjunky.com

CSpenceFLY - I can't believe the number of people willing to bet their life on someone else doing the right thing.

[audacium 0]

Hello all canopy-people,


Sorry, I do not have much time, so I will just throw this in, without having thought much about it, maybe it is still of interest and my idea goes in the right direction.

I think the effect of the "wind gradient" has been forgotten until now and it might play a role in this discussion. Wind gradient simply means, that wind will get slower closer to the ground due to the friction. So, in higher winds the wind gradient will be stronger.

Being in a wind gradient means that the canopy is always entering the next layer of air (which moves slower) kind of too slow (risk of stall if you are in deep brakes), so maybe it has an effect when in full flight / carving the canopy in that the lift of the canopy will be less than in a weaker wind gradient. So this might explain why maybe indeed you have to set up a little bit higher in high winds.

But some people seem to experience vice versa :).

It seems most arguments in this discussion have relied on a homogeneous wind velocity from set up height to ground which is not exactly correct I believe.

Whatever, just some food for thought, I hope you get the idea what I am trying to say, now I have to continue working, sorry, maybe I can join the discussion later in the week.

--
Eduard

[marks 0]

  Quote

It seems most arguments in this discussion have relied on a homogeneous wind velocity from set up height to ground which is not exactly correct I believe.

yes it has been, but it was discussed this way to make it simple, and to take other variables out so it could be understood in its most basic form.

but what you speak of, "wind gradient", is interesting I have heard of that before, not sure how much a role it plays, but it is something to think about nonetheless.

[The111 1]

  Quote

Wind gradient simply means, that wind will get slower closer to the ground due to the friction. So, in higher winds the wind gradient will be stronger.

What you're talking about is a boundary layer. I'm curious what the actual distribution is from 0-1000ft for a given wind intensity, but I would guess that the gradient is very negligible. I mean, standing on the ground we can still feel very strong winds. Although, theoretically, the winds must be 0 mph at 0 ft.

Anybody have any real data to answer this question? I have no idea.

www.WingsuitPhotos.com

[audacium 0]

Boundary layer...I would apply that rather in aerodynamics around well defined bodies, but whatever, I am not a meteorologist
The term wind gradient comes from paragliding (at least that is where I know it from), and it is in strong winds very relevant. Quite some people stall their gliders unwantingly in deep brake approaches in high winds because they do not know about wind gradients.

Now, a paraglider is obviously a different beast, but at least for me this is sufficient to believe that wind gradients are not negligible. Agreed that real data would help, but the wind gradient would offer a qualitative explanation for a start.

Now gotta get back to work .

--
Eduard

[genoyamamoto 0]

  Quote

Boundary layer...I would apply that rather in aerodynamics around well defined bodies, but whatever, I am not a meteorologist
The term wind gradient comes from paragliding (at least that is where I know it from), and it is in strong winds very relevant. Quite some people stall their gliders unwantingly in deep brake approaches in high winds because they do not know about wind gradients.

Now, a paraglider is obviously a different beast, but at least for me this is sufficient to believe that wind gradients are not negligible. Agreed that real data would help, but the wind gradient would offer a qualitative explanation for a start.

Now gotta get back to work .

I do not expect the boundary layer to extend very far at all. I think you can get an order of magnitude estimate for boundary layer thickness from the rules of thumb used to describe the turbulent area above objects during windy days (i.e. x2 height of feature, this in my mind would be the worst case scenario for air flow perturbation). Most common feature on the ground lets say is grass or rocks, a few inches high so take x2 of a few inches, which is probably going to be no more than a foot or so.

I don't know anything about paragliding nor the conditions/environment where you witnessed people falling out of the sky but I would venture to make an uneducated guess that they are hitting rotors off of obstacles upwind on a windy day and landing hard.

If you are up to it, find a very tall antenna in your neighborhood, take an anemometer with you and measure the wind speed as a function of height on a windy day. This should give you some idea of the magnitude of the velocity gradient. I'd be curious to see what you find out!

Gotta go... plaything needs to spank me
Feel the hate...
Photos here

[audacium 0]

  Quote

I do not expect the boundary layer to extend very far at all. I think you can get an order of magnitude estimate for boundary layer thickness from the rules of thumb used to describe the turbulent area above objects during windy days (i.e. x2 height of feature, this in my mind would be the worst case scenario for air flow perturbation). Most common feature on the ground lets say is grass or rocks, a few inches high so take x2 of a few inches, which is probably going to be no more than a foot or so.

Honestly, at the moment I have no idea, what you say sounds reasonable, but I could imagine that a boundary layer over ground extends much further. I will try to find data.

  Quote

I don't know anything about paragliding nor the conditions/environment where you witnessed people falling out of the sky but I would venture to make an uneducated guess that they are hitting rotors off of obstacles upwind on a windy day and landing hard.

Well, falling out of the sky is maybe not the exact description :). But there is definitely a wind gradient effect as opposed to hitting a rotor. Typical case: people landing in high winds on a large field (so no turbulences around), in deep brakes, and closer to the ground the glider stalls. Most people will react fast enough and put the hands up so they land safely, however, sometimes it happens too close to the ground or they react wrong. I experienced this myself, at least the glider becoming soft.

  Quote

If you are up to it, find a very tall antenna in your neighborhood, take an anemometer with you and measure the wind speed as a function of height on a windy day. This should give you some idea of the magnitude of the velocity gradient. I'd be curious to see what you find out!

Sounds like a very good idea!

--
Eduard

[bob.dino 1]

  Quote

I do not expect the boundary layer to extend very far at all. I think you can get an order of magnitude estimate for boundary layer thickness from the rules of thumb used to describe the turbulent area above objects during windy days (i.e. x2 height of feature, this in my mind would be the worst case scenario for air flow perturbation).

It actually extends 1-2km from the Earth's surface and affects both speed and direction. I don't have figures for the magnitude of the effect at various altitudes. I'll try to have a look over the weekend and get back to you...

[pchapman 279]

Just to touch on the wind gradient issue:
Various formulas (usually exponential) exist. As height goes up, wind speed increases rapidly at first, and then more slowly.

One reasonable formula, for example, results in the following numbers, over terrain that consists of high grass or low crops:

5 ft height ------ 18 mph
15 ft height ------ 22 mph
33 ft height ------ 25 mph
100 ft height ------ 31 mph
200 ft height ------ 35 mph
(The above would be for a weather report of 25 mph winds, since a standard measuring height is 33 ft.)

Real life of course will vary a lot! While the formula makes it all a gradual change, the overall change is significant -- the wind is about doubled a couple hundred feet up, compared to what one feels in one's face on the ground.