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working out canopy speed

 

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JoHawley  (C 103157)

May 10, 2003, 4:40 AM
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working out canopy speed Can't Post

A friend of mine recently flew into a bank on landing. He was surprised at the amount of damage (serious steelwork in the leg and a broken back) and he's curious to know what sort of impact speed it was. He flies a Sabre 2 150 loaded at about 1.55. There was no wind. Is there a formula to work out how fast he was going?
Cheers
Jo


andy2

May 10, 2003, 5:45 AM
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Re: [JoHawley] working out canopy speed [In reply to] Can't Post

I'm not really that great at math, but I have a hunch you would need his surface area as well as his wingloading to get a truly accurate measure.


mikeat10500  (B 3715)

May 10, 2003, 6:44 AM
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Re: [JoHawley] working out canopy speed [In reply to] Can't Post

When all the data is not available I use a SWAG
calculation...I came up with 44.3mph!

Hope your friend gets well soon....mike


riggerrob  (D 14840)

May 10, 2003, 8:06 AM
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Re: [mikeat10500] working out canopy speed [In reply to] Can't Post

Theories, math, density altitude, etc. amuse mathematicians are useless in the real world. The only accurate measurement of canopy speed is done with a wind meter while hanging under a open canopy.


SkydiveMonkey  (B 102345)

May 10, 2003, 9:10 AM
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Re: [JoHawley] working out canopy speed [In reply to] Can't Post

Depends whether he was on full drive on near the stall point in the flare


mikeat10500  (B 3715)

May 10, 2003, 9:52 AM
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Re: [riggerrob] working out canopy speed [In reply to] Can't Post

In reply to:
Theories, math, density altitude, etc. amuse mathematicians are useless in the real world. The only accurate measurement of canopy speed is done with a wind meter while hanging under a open canopy.

In this real world we can not turn back time and put a wind meter on our injured friend...so I challenge
anyone to come up with a more accurate method.
...mikeCool


Premier PhreeZone  (D License)
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May 10, 2003, 10:14 AM
Post #7 of 42 (1781 views)
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Re: [mikeat10500] working out canopy speed [In reply to] Can't Post

Put a wind meter on someone else of similar size Wink

Canopy speed in normal flight tends to be in the 20 mph range.


mikeat10500  (B 3715)

May 10, 2003, 10:24 AM
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Re: [PhreeZone] working out canopy speed [In reply to] Can't Post

In reply to:
Put a wind meter on someone else of similar size Wink

Canopy speed in normal flight tends to be in the 20 mph range.

If a sabre2 at 1.55:1 flys at 20mph I guess that
my pd210 at 0.9: would be....10mph and a manta
with a 95lb girl would fly at 4mph and under her
round reserve -6mph airspeed??????????
Hows that work?


Premier PhreeZone  (D License)
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May 10, 2003, 11:26 AM
Post #9 of 42 (1759 views)
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Re: [mikeat10500] working out canopy speed [In reply to] Can't Post

Actually... normal forward speed of a canopy is usually with in a few miles per hour of each other no matter the size or loading (to a point). Air Speed is 20-25 mph but ground speeds are a different matter. A stilletto and a Sabre fly at almost the same exact air speed, but one is trimmed differnt so it feels faster then the other.

I fly fairly close to the same airspeed under my Jedei 136 at 1.5 as a tandem at 1:1 or a student at .8:1. The issue is the Jedei is trimmed steeper so it comes down faster. I've floated with both the above so I know its possible.

Rounds are a different function altogether.


CRWBUDDHA  (D 11759)

May 10, 2003, 11:41 AM
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Re: [JoHawley] working out canopy speed [In reply to] Can't Post

In your first jump course you were given the basics of canopy flight and perhaps you remember the descent rate of a ram air canopy is 25fps. take that times 1.5 and you will get started.....next take that number times 60 to get into minutes then times 60 again to get into hours then divide by 5280 and get mph.

Many similar results are found on todays roads at 25 mph so don't feel slighted that you were not going some outrageiou speed like 60 or 70.

I'm sad that another zoomie got smacked however no amount of higher intelligence can be successfully legislated or guarenteed to present itself at any given moment. The fact that your friend sustained serious and permenant damage should be enough education to warrant you and any others to refrain from those activities that increase risk beyond most bodies ability to heal.

Perhaps your inquisitiveness might be more well suited to investigating ways to improve awareness and decrease reaction time to avoid such results.

God knows that the sport could use some really good scilence in this area, ...........How many would heed any advice.............?

I hope your friend heals well enough to become a mentor to someone else before they follow suit.
Cheers,
Buddha


(This post was edited by CRWBUDDHA on May 10, 2003, 11:54 AM)


mikeat10500  (B 3715)

May 10, 2003, 11:45 AM
Post #11 of 42 (1752 views)
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Re: [PhreeZone] working out canopy speed [In reply to] Can't Post

In reply to:
Actually... normal forward speed of a canopy is usually with in a few miles per hour of each other no matter the size or loading (to a point). Air Speed is 20-25 mph but ground speeds are a different matter. A stilletto and a Sabre fly at almost the same exact air speed, but one is trimmed differnt so it feels faster then the other.

I fly fairly close to the same airspeed under my Jedei 136 at 1.5 as a tandem at 1:1 or a student at .8:1. The issue is the Jedei is trimmed steeper so it comes down faster. I've floated with both the above so I know its possible.

WOW I did not know they were that close in speed
and if you are correct than wingloading to
injury severity is a total myth(not to put words in your mouth).

In reply to:

Rounds are a different function altogether.
Yes...rounds do not really fly....the descend with forward speed.
...mikeCrazy


rgoper  (C 32349)

May 10, 2003, 12:13 PM
Post #12 of 42 (1738 views)
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Re: [JoHawley] working out canopy speed [In reply to] Can't Post

Quote:
He flies a Sabre 2 150 loaded at about 1.55. There was no wind.

he should have been flying a canopy that provided a 1.0:1 wingload, this surely would've prevented the whole scenario.

hope your friend heals quickly.


mikeat10500  (B 3715)

May 10, 2003, 3:08 PM
Post #13 of 42 (1711 views)
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Re: [PhreeZone] working out canopy speed [In reply to] Can't Post

In reply to:
Actually... normal forward speed of a canopy is usually with in a few miles per hour of each other no matter the size or loading (to a point). Air Speed is 20-25 mph but ground speeds are a different matter. A stilletto and a Sabre fly at almost the same exact air speed, but one is trimmed differnt so it feels faster then the other.

I fly fairly close to the same airspeed under my Jedei 136 at 1.5 as a tandem at 1:1 or a student at .8:1. The issue is the Jedei is trimmed steeper so it comes down faster. I've floated with both the above so I know its possible.

Rounds are a different function altogether.

PhreeZone

I looked around DZ.com for some measured air
speeds under canopy and found very little.
(1)>snip>>I measured the air speed of both a 190 Sabre and 190 Triathlon. Both were 30 mph with about 230 lbs suspended.
(2)>snip>>I used a Kestrel 1000 which resulted in an airspeed about 23-24 mph on a Sabre 170 loaded about 1.1.
Going on this info it would seem wingloading does indeed effect air speed (more than you think) and
you need a smaller pilot chute!
Watch out or I'll blow right by you with my PD210!!
The whole idea of lower wingloading is to reduce air
speed ( and the related ground speed) and to reduce force of impact (speedxwieght) when someone biffs. You can however slow down your canopy to fly relitive with someone else using toggles,
risers or a combo of both(welcome to CRW).
....mikeCool


Premier PhreeZone  (D License)
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May 10, 2003, 4:28 PM
Post #14 of 42 (1691 views)
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Re: [mikeat10500] working out canopy speed [In reply to] Can't Post

I guess I should have said at the same trim angle. Flaten out a canopy on rears and it does'nt decrease your speed, but it does flatten out the glide angle and things become closer in airspeed. PD is the ones that state on the same size canopy they are all very close in speed.

I might go get a Kestral and toss it out after some tandems and on my own canopy to get some more numbers.


mikeat10500  (B 3715)

May 10, 2003, 5:08 PM
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Re: [PhreeZone] working out canopy speed [In reply to] Can't Post

Eric
Cool man...love to see some numbers...it seems
they are hard to come by.
...mike@22mphTongue


amir1967  (B License)

May 10, 2003, 5:54 PM
Post #16 of 42 (1672 views)
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Re: [mikeat10500] working out canopy speed [In reply to] Can't Post

If I got it right a canopy of the same size and at about the same wing load will fly at the same speed.
so your┤s jedie can fly in braks with manta or a tandam but in normal flight it will have more forward speed
just my 0.02 Euro cent
How fast in mile/Km per hour I couldn┤t find anywhere and it seems to me that with the acception of atair no other canopy have data or will post some data for people to see.


mikeat10500  (B 3715)

May 10, 2003, 7:08 PM
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Re: [amir1967] working out canopy speed [In reply to] Can't Post

Amir

I think it is very simple.
Higher wingload=faster(air speed)
Less drag=faster(air speed)

Higher wingloads can be accomplished by eating more burgers( add weight) or getting a smaller parachute( ram air thingy ).

Less drag can be accomplished by things like micro-lines, canopy profile, collapsible pilot chute, bringing your feet up, cutting away, etc.

Slowing down well its hard to change your wingloading during flight( though not impossible I'm sure) but you can induce drag by using toggles or
rear risers to create some lift and trade off air speed
(nothing is free in this world) or distorting the shape of the wing ( wing warping) .

that's 3 cents worth....mikeTongue


Premier quade  (D 22635)
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May 10, 2003, 11:02 PM
Post #18 of 42 (1620 views)
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Re: [PhreeZone] working out canopy speed [In reply to] Can't Post

Quote:
Actually... normal forward speed of a canopy is usually with in a few miles per hour of each other no matter the size or loading (to a point). Air Speed is 20-25 mph but . . .

I don't think so.

I mean, I'm definately not an authority on CRW or anything even close to it, but canopies have to be matched up in type and wingloading to even sort get into the ball park.

I know I have to sashay like a mother to shoot the occasional CRW or PRO flag or banner, because I'm usually the one that's going so damn much faster and that's on a Spectre loaded at only about 1.3:1!

So, um, even without and real hard data to back up my statements, I gotta call shenanagans on this one.


(This post was edited by quade on May 10, 2003, 11:03 PM)


andy2

May 11, 2003, 6:25 AM
Post #19 of 42 (1590 views)
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Re: [PhreeZone] working out canopy speed [In reply to] Can't Post

Quote:
Actually... normal forward speed of a canopy is usually with in a few miles per hour of each other no matter the size or loading (to a point). Air Speed is 20-25 mph but . . .

I was under the impression that a higher wingloaded canopy descended faster, thus creating more lift, which converts into faster foward speeds. Is this wrong?


Premier PhreeZone  (D License)
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May 11, 2003, 10:47 AM
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Re: [quade] working out canopy speed [In reply to] Can't Post

Canopies have to be matched up in trim angle, line length and lots other things to fly at the same rate.

The issue that I'm seeing is that compairing a Stiletto to a Sabre there is a trim difference so one feels faster. When I flatten out the glide angle of my canopy to be that of the one I'm flying beside (via rear risers) it does'nt really slow me down but it does reduce my sink. Flying a Sabre beside a Stiletto the Sabre will fall out of formation faster but it also will start to pull away since its trimmed steeper. Get the trim angles the same and the canopies fly very close to each other. I pull away from the guy I jump Lightnings with unless he adds links to his rears to increase his trim angle. The loadings never change but with just trim we can play on either his 193 or 210 and my 160. (Me at about 1.24 and him on the 193 at 1.1 or 1:1 on the 210)

Yes, some one that loads a canopy more will get more forward speed but we're not talking about 50 mph differences here, more like at a max of 10 or so. So 20-30 MPH better?


Premier billvon  (D 16479)
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May 11, 2003, 1:23 PM
Post #21 of 42 (1528 views)
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Re: [riggerrob] working out canopy speed [In reply to] Can't Post

> Theories, math, density altitude, etc. amuse mathematicians are useless in the real world.

It's fortunate that that's not true, or Boeing would have had to build hundreds of versions of each type of aircraft (and then watched them all crash) before they got one that flew. Mathematical approximations can get you very close to a correct answer, and it's something we all do when we deal with people flying canopies (i.e. we know that a Stiletto at 2 to 1 is harder for a new jumper to land than a Sabre at 1.2 to 1; we don't even need to see them jump both canopies in identical conditions to believe this.)


Push  (A 10205)

May 11, 2003, 1:55 PM
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Re: [billvon] working out canopy speed [In reply to] Can't Post

Would it be safe to assume that the amount of lift the canopy generates is proportional to the suspended weight? The constant of proportionality is then determined by airfoil shape and the direction of the lift force is determined by the AOA. Seems to me it's sort of a no-brainer from here.

(spelling)


(This post was edited by Push on May 11, 2003, 1:55 PM)


Premier billvon  (D 16479)
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May 11, 2003, 2:26 PM
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Re: [Push] working out canopy speed [In reply to] Can't Post

> Would it be safe to assume that the amount of lift the canopy generates
> is proportional to the suspended weight?

The amount of lift the canopy generates is exactly the same as the suspended weight in the classic lift-weight-thrust-drag diagram. It has to be, or you either accelerate upwards or downwards indefinitely. In the case of a glider (which a parachute is) the direction gravity pulls gets decomosed to the weight vector and the thrust vector - since you're descending, there is a component of your weight vector that pulls you forward.

Since parachutes are inherently stable in pitch and airspeed, they tend to very quickly return to an equilibrium where all four vectors balance. Since heavier people have more weight, and thus more "thrust," the equilibrium point is at a faster airspeed than with a lighter person - but in both cases the canopy is still in equilibrium.


Premier billvon  (D 16479)
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May 11, 2003, 2:31 PM
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Re: [mikeat10500] working out canopy speed [In reply to] Can't Post

>Higher wingload=faster(air speed)

That's true but . .,

>Less drag=faster(air speed)

That's not. A parachute is a very stable aircraft in both pitch and airspeed, and when you change the L/D by reducing drag, it tends to correct itself and remain at the same speed. You do get a better glide angle though (L/D is often how glide angle is expressed.)

This is true in aircraft as well. If you increase power (which is the same as decreasing drag in terms of the four-force diagram) the plane will initially speed up - then its nose will come up, it will slow down, and it will stabilize again at about the same airspeed, but this time at a higher climb angle.


Push  (A 10205)

May 11, 2003, 3:05 PM
Post #25 of 42 (1502 views)
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Re: [billvon] working out canopy speed [In reply to] Can't Post

Alright, so, in a glide, the thrust component of the lift will cause the jumper+rig system to accelerate until drag=thrust. Drag should be proportional to the surface area presented to the relative wind, which is the nose. Drag is also related to the cube of the velocity, I think... Because of the ram air design, it is probably safe to assume that the entire nose acts like a solid surface with respect to the drag because it's full of air. So there you go. More AOA, higher thrust component, more drag required to compensate, more time to reach "terminal", higher "terminal". Less cell volume, less drag generated, takes longer to compensate for thrust, higher "terminal" velocity acquired by the system. If my assumptions are true and I didn't forget anything, we can compare the same canopy under different wingloadings safely. Let's see. All else kept constant, AOA in particular, thrust is directly related to weight. All else being equal in the two canopies, we have:

Drag/Drag' = (v^3)/(v'^3), and

ratio of "terminal" velocities=cubic root of ratio of weights.

Which tells us that, as you increase wingloading, you're going to see a dramatic difference between 1.2 and 1.5, but not that dramatic between 2.0 and 2.3, which I have no idea about with my 35 jumpsSmile We also see why wingloading is not as great a measure of performance as we would like it to be. I know nothing of real aerodynamics, so I'll assume it can measure the lift generated just fine. But the drag depends on the nose of the canopy, which is not really all that related to the raw square footage.

Of course, among a ton of other things, this assumes that thrust is mostly constant. Is it?

EDIT: having read this over, I've realized that there are so many assumptions here that it's practically useless.


(This post was edited by Push on May 11, 2003, 3:07 PM)


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