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Looking for parachute design info

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Does anyone know where I can find information on what determines a canopy's 'recovery arch' and flare characteristcs from reliable sources?

I'm assuming the recovery arch has much to do with the Angle-of-Incidence (AoI) of the parachute and the thickness of the wing. It makes sense to me that the higher form drag of a 'thick' wing would allow the jumper to swing underneath sooner. The AoI would play a role in that a steep AoI would mean the jumper would have to swing further under the wing to reach a given Angle-of-Attack compared to a canopy with a more shallow AoI.

But I'm tired of speculating with my 'armchair knowledge' of canopy design. I've scoured the web but can't find much useful info out there. I'm looking for fairly technical info.

If anyone can help, let me know.

Thanks!
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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Does anyone know where I can find information on what determines a canopy's 'recovery arch' and flare characteristcs from reliable sources?

I'm assuming the recovery arch has much to do with the Angle-of-Incidence (AoI) of the parachute and the thickness of the wing. It makes sense to me that the higher form drag of a 'thick' wing would allow the jumper to swing underneath sooner. The AoI would play a role in that a steep AoI would mean the jumper would have to swing further under the wing to reach a given Angle-of-Attack compared to a canopy with a more shallow AoI.

But I'm tired of speculating with my 'armchair knowledge' of canopy design. I've scoured the web but can't find much useful info out there. I'm looking for fairly technical info.

If anyone can help, let me know.

Thanks!



I have a program that calculates trajectories based on input variables of velocity, lift and drag coefficients, WL and density altitude.
These input variables are not linked to specific geometric specifications of canopies.
The code is only two dimensional right now. The simulation starts at the time from the end of a speed inducing maneuver to natural recovery (hands off flying). It does not model any type of flare maneuver.
Some sample results were posted here awhile back.

If you find me funding, I can develop it further.

.
.
Make It Happen
Parachute History
DiveMaker

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I'd be curious to see what you were playing with. I'd toyed with something similar but I was never happy with the results. It should be a pretty simple problem. I could never decide if I had a bug some where or if I was missing something but my answers weren't coming out the way I expected and I think I had an error in there some where. Basically I was looking at the canopy as it passed through a wind shear. Like at the end of the day when it goes dead still but 150 feet up it's still blowing. I'd been arguing with a guy about recovery arc and was trying to do a quick model. I lost interest and never got around to getting it working.

Lee
Lee
[email protected]
www.velocitysportswear.com

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I don't think many people do know what determines the "recovery arch", but you might be better off asking about the canopy's "recovery ARC". :D



HA
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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I have a program that calculates trajectories based on input variables of velocity, lift and drag coefficients, WL and density altitude.
These input variables are not linked to specific geometric specifications of canopies.
The code is only two dimensional right now. The simulation starts at the time from the end of a speed inducing maneuver to natural recovery (hands off flying). It does not model any type of flare maneuver.
Some sample results were posted here awhile back.

If you find me funding, I can develop it further.



I think I can work on the relativistic version if anyone wants to jump near a black hole.

-- Jeff
My Skydiving History

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I think the importance of the recovery arc is more complicated than a matter of angle of incidence only. The way the weigth of the jumper is distributed between the front and the rear of the canopy counts as well. The shape and size of the airfoil is responsible to generate the lift and it is likely going to influence the recovery arc too.
That question should be ask to the following canopy specialists: John LeBlanc at PD, John Sherman at Jump Shack, Brian Germain, Georges Galloway from Precision Aerodynamics, Ted Strong...
Learn from others mistakes, you will never live long enough to make them all.

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Exactly. That's kind of what I'm looking for. How much each part plays a role. AoI, CoG, planeform, lift coefficient...yadda, yadda.

Size...in relation to how a canopy flies...yes. Knowing that various sizes have different characteristics. But in relation to wing loading...no. I want to be able to leave wing loading out of the equation. For example, explaining why a particular 120 would have a different recovery ARC than another 120 with the same person underneath it.
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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It all boils down to a CL and CD. are you looking to build a model based on that or are you trying to predict them based on the spec's of the canopy. One is very doable the other is pretty much a nightmare. Honestly the best way to do the second problem is to measure it directly off a canopy. Eather being kited or in a tunnel.

Lee
Lee
[email protected]
www.velocitysportswear.com

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Actually, I'm not trying to build/predict anything.

I'm putting together a canopy class for our drop zone. One thing I would like to do is put together a portion using canopy 'myths'. This led to a few other areas but one of them being the often lauded 'recovery arc'.

I would like to find a way to explain why some canopies have a long recovery arc.
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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Ok, try this on for size. First keep in mind that there are a lot of variables here and it is at best hard to make really wide generalazations. We're talking hands up no toggle imput here. Also be advised that I'm pulling most of this straight out of my ass.

Here goes. A canopy is trimmed at a natural CL. So in a steady state it wants to fly at certin air speed to produce the lift to suport your body weight. G=1

Now for its flight path to curve upwards you have to produce more lift G>1. In other words you have to go faster. L is proportional to the square of V. But surfice it to say that the amount of excess lift relates to how much over speed you are going. The amount of curve in your arc depends on how much G you are pulling and your over all speed. a little of excess L on a fast canopy, slight arc, long recovery. A lot of extra L on a slow moveing canopy, Hard turning fast arc, quick pull out.

I'll try to make this make sence. Big student canopy. Wants to fly slow. Hook it and it feels like you swing back underneath it in nothing more then the length of the lines. If you get it going even a little bit faster it's a signifagent increase in lift and your not going that fast over all so the recovery happens over a very small arc length.

Remember you have to increase your speed by the sqr of 2 to pull two G. So if you can go 40% faster you'll be makeing a 2G pull out. So 40% faster on a Manta is still not that fast. At two G it ony takes a couple of seconds to correct your path back to steady state. In the mean time you have not gone all that far along the arc. It almost looks like a 90 deg corner.

Same canopy heavier guy underneath it. The canopy wants to fly faster. For the same percentage increase in speed it takes the same amount of time for the canopy to recover. But now the over all speed is greater during this time. That means a longer arc.

Other examples. Lets take a flat trimmed canopy like a Stileto. Being trimmed flat means it has a good glide angle but is a little bit slow. The flatter you trim the canopy the slower it will be in stedy flight for the same wing loading. You hook it and it has a relatively short recovery arc because the steady state speed of the canopy is relativly slow. Also the glide path is shallow so it feels like the angle you've returned to as you come out of the hook is more pronounced. In fact sence the canopy is going to come out of the hook and may climb to a path above it's natural glide angle you may find that it almost planes it self out with out any input.

Now lets look at a canopy of the same size but with a steaper trim. I'll throw out a Katana as an example. The natural glide angle is not as good but the canopy wants to fly faster. When you hook this with the same percentage increase in speed you're pulling the same G loading but moveing much faster. So the recovery arc is much longer. Also the angle it wants to return to is steaper and you may feel that it has not pulled out on it's own. You may feel that it needs more toggle to plane out.

The issue becomes even more extream as the canopies become smaller and there speed increases. We have one guy that jumps a canopy in excess of 4.0 In steady flight I'm guessing he's running in excess of 60 mph. He spots his exit for his landing approach. I mean i would guess he starts his turn at over two grand.

This is pretty dumbed down. It's really not fair to compare diffrent canopies like this. We're leaveing out a lot of variables. And I don't write very well. But at least it sounds like a decent line of bull shit. Pollish it a bit and I think you can pass it off on an unwitting low time jumper.

Lee
Lee
[email protected]
www.velocitysportswear.com

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Well, you've pretty much stated the same conclusions I've come to. Sorry to say this only after you've written all of that. But maybe we're on the right track then?

It seems to come down to that wicked angle of incidence thing.
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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