Forums: Skydiving Disciplines: Swooping and Canopy Control:
"Old School" canopy myths

 

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AggieDave  (D License)

Nov 14, 2003, 12:58 PM
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"Old School" canopy myths Can't Post

This has come up in the "carving" thread, about old canopy myths that are being debunked, etc.

This got me thinking, wondering what sort of information that I know and hold to be true, that may infact be incorrect.

My first thought is about recovery arcs in wind, my thought is that when there is wind, a canopy with a short recovery arc will have a shorter recovery arc, due to the airspeed coming out of the "corner" of a dive.


Those with more experience/knowledge (Hooknswoop, etc), please debunk that if it needs to be debunked.


I'm sure there are many more that may or may not be true, so please post some if you have them.


Jimbo  (D License)

Nov 14, 2003, 1:43 PM
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Re: [AggieDave] "Old School" canopy myths [In reply to] Can't Post

 
Quote:
My first thought is about recovery arcs in wind, my thought is that when there is wind, a canopy with a short recovery arc will have a shorter recovery arc, due to the airspeed coming out of the "corner" of a dive.

We've already determined though that airspeed is constant though, regardless of wind, didn't we? Why would any canopy recover more quickly on a high wind day?

-
Jim


diablopilot  (D License)

Nov 14, 2003, 4:45 PM
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Re: [AggieDave] "Old School" canopy myths [In reply to] Can't Post

Quote:
My first thought is about recovery arcs in wind, my thought is that when there is wind, a canopy with a short recovery arc will have a shorter recovery arc, due to the airspeed coming out of the "corner" of a dive.

Yup. Not true.

How about:

"Go to 1/2 to 3/4 in turbulance"

Yeah right. Lets just go and REDUCE the internal pressure of that canopy in turbulance shall we?!Crazy


billdo  (D 25571)

Nov 14, 2003, 6:31 PM
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Re: [diablopilot] "Old School" canopy myths [In reply to] Can't Post

In reply to:
Quote:
How about:

"Go to 1/2 to 3/4 in turbulance"

Yeah right. Lets just go and REDUCE the internal pressure of that canopy in turbulance shall we?!Crazy

I've wondered about that because my thinking was to "let it fly" or even go to double fronts to increase the pressure, but when I asked a well-known xaos team pilot at Eloy he said to go to halfs if cought in a dust devil.

??


Jimbo  (D License)

Nov 14, 2003, 7:27 PM
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Re: [billdo] "Old School" canopy myths [In reply to] Can't Post

 
I don't think that going to double fronts would increase the internal pressure. Would it? Anyone?

-
Jim


parachutist  (D 25468)

Nov 14, 2003, 8:56 PM
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Re: [Jimbo] "Old School" canopy myths [In reply to] Can't Post

In reply to:
I don't think that going to double fronts would increase the internal pressure. Would it? Anyone?

-
Jim

Basically anything that increases your air speed will, in turn, increase the pressure inside your ram-air canopy.

It's just like a wind sock: the higher the wind speed, then the more air is getting shoved inside. The resulting higher pressure inside the wind sock will make the wind sock stand out more.

Another analogy: close your mouth and blow a little, inflating your cheeks. Blow a little bit harder and you will feel the additional pressure.

Smile


Premier ianmdrennan  (D 25821)
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Nov 14, 2003, 8:59 PM
Post #7 of 43 (2568 views)
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Re: [billdo] "Old School" canopy myths [In reply to] Can't Post

Quote:
I asked a well-known xaos team pilot at Eloy he said to go to halfs if cought in a dust devil.

I don't know a thing about dust devils but they happen low to the ground right? If so I'd assume the pilot would be trying to soften the impact in this scenario by going to half brakes.

Dunno - anyone with dust devil experience know any other reason why the XAOS pilot would say this?

Blue skies
Ian


skycat  (D 25740)

Nov 14, 2003, 9:10 PM
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Re: [ianmdrennan] "Old School" canopy myths [In reply to] Can't Post

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Dunno - anyone with dust devil experience know any other reason why the XAOS pilot would say this?

The odds of your canopy collapsing is greater in a dust devil than in any normal turbulance. By going into half brakes you are basically putting your canopy in the same configuration as when it opens with toggles stowed. This in turn allows your canopy to re-inflate faster than if you had the toggles all the way up.

When it comes to dust devils though all bets are off and your best bet is to avoid it.


johnny1488  (D 25453)

Nov 14, 2003, 9:10 PM
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Re: [parachutist] "Old School" canopy myths [In reply to] Can't Post

I've thought about the extra air speed thing. I've heard 2 schools of thought. One is yours, the other is that double fronts deform the airfoil, thus making the canopy more succeptable to turbulence. Scott Miller said its a give and take situation. More airpressure is good, but now your probably heading for the ground a lot faster and if you have a collapse...


parachutist  (D 25468)

Nov 14, 2003, 9:50 PM
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In reply to:
I've thought about the extra air speed thing. I've heard 2 schools of thought. One is yours, the other is that double fronts deform the airfoil, thus making the canopy more succeptable to turbulence. Scott Miller said its a give and take situation. More airpressure is good, but now your probably heading for the ground a lot faster and if you have a collapse...

Oops, I didn't realize that turbulence was part of this equation. I thought it was a straightforward question about whether not pressure would increase

Right, I don't think that double fronts through turbulent conditions near the ground would be such a great idea. Letting the canopy go to full flight is the advice I've always gotten & it seems like the best idea in turbulent conditions.

Chris


grega  (D 100020)

Nov 15, 2003, 10:08 AM
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Re: [Jimbo] "Old School" canopy myths [In reply to] Can't Post

Hmm actually the pressure inside the canopy is never higher than the pressure of the air at that altitude temperature and humidity. The air pressurises at speeds waaay higher than you could fly with any canopy (more than 300mph)

What changes is the pressure that is around the canopy, which get's even less, so the canopy is even more "tight" (streched apart). it's the same think why the canopy is pressurised. because the pressure outside is less than the pressure inside the canopy. and inside the canopy pressure is always same as the pressure that is at the stagnation point (few inches infront of the canopy)

But nevertheless, the faster you go, the bigger the difference in pressures, more rigid the wing is.


Hooknswoop  (D License)

Nov 15, 2003, 10:56 AM
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Hmm actually the pressure inside the canopy is never higher than the pressure of the air at that altitude temperature and humidity. The air pressurises at speeds waaay higher than you could fly with any canopy (more than 300mph)

Then explain how an airspeed indicator works at less than 40 mph..........

The air pressure inside a canopy is higher than the static air pressure near the canopy.

Derek


grega  (D 100020)

Nov 15, 2003, 5:20 PM
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In reply to:
Then explain how an airspeed indicator works at less than 40 mph..........

I don't know, but i'd like to find out.


AndyMan  (D 25698)

Nov 15, 2003, 5:56 PM
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Re: [Hooknswoop] "Old School" canopy myths [In reply to] Can't Post

I understand that the preasure inside the canopy is pretty much normal, but its a low preasure area above the canopy which keeps it inflated...?

_Am


Hooknswoop  (D License)

Nov 15, 2003, 7:59 PM
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Re: [grega] "Old School" canopy myths [In reply to] Can't Post

An airspeed indicator works with a pitot tube and a static port. It compares the ram-air pressure coming into the pitot tube with ambient pressure from the static port to give airspeed. The ram-air pressure into the pitot tube begins immediately and increases with airspeed.

The same thing with a canopy. It flys through the air and rams air into it, creating a higher pressure inside the canopy than outside the canopy. The low pressure (lifting force) is only above the canopy from the shape of the upper surface.

One atmosphere is only 14.7 PSI. A few PSI is enough to make the canopy quite rigid, like a mylar helium balloon.

Derek


grega  (D 100020)

Nov 16, 2003, 10:52 AM
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Re: [Hooknswoop] "Old School" canopy myths [In reply to] Can't Post

I looked closely into it and you're totaly right.
i can't even remember where i read what i was claiming before. But obviously i misunderstood something when i read that... Blush

Anyway hooknswoop is right. The internal pressure is higher.


kallend  (D 23151)

Nov 16, 2003, 11:36 AM
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Re: [parachutist] "Old School" canopy myths [In reply to] Can't Post

In reply to:
In reply to:
I don't think that going to double fronts would increase the internal pressure. Would it? Anyone?

-
Jim

Basically anything that increases your air speed will, in turn, increase the pressure inside your ram-air canopy.

It's just like a wind sock: the higher the wind speed, then the more air is getting shoved inside. The resulting higher pressure inside the wind sock will make the wind sock stand out more.

Another analogy: close your mouth and blow a little, inflating your cheeks. Blow a little bit harder and you will feel the additional pressure.

Smile

But the opening on a wind sock is at the front. The openings on a high performance canopy are usually under the nose. If you move the stagnation point away from the openings by lowering the AOA too much you will initiate a top skin collapse starting at the LE. Going to 1/4 brakes will keep the stagnation point down under the nose where the openings are.


apoil  (D License)

Nov 17, 2003, 8:07 AM
Post #18 of 43 (2140 views)
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Re: [skycat] "Old School" canopy myths [In reply to] Can't Post

In reply to:
The odds of your canopy collapsing is greater in a dust devil than in any normal turbulance. By going into half brakes you are basically putting your canopy in the same configuration as when it opens with toggles stowed. This in turn allows your canopy to re-inflate faster than if you had the toggles all the way up.

Maybe I'm misreading this.

You don't stow your toggles to make your canopy inflate faster.
you stow your toggles so that you don't open in full flight - which is dangerous if there's any kind of problem like a malfunction or an imminent collision. It also HURTS because it's a faster opening.

I see no reason half brakes would allow for faster reinflation.


breadhead  (D 236)

Nov 17, 2003, 8:41 AM
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Re: [billdo] "Old School" canopy myths [In reply to] Can't Post

Straight from the PD website:

http://www.performancedesigns.com/faq.htm

Quote:
If you find yourself in turbulent conditions, we recommend flying at full glide. At full glide, the canopy will penetrate through turbulence better, and be less affected by it.

Contrary to what some people have been told, flying in brakes does not necessarily help keep the canopy pressurized.

Aerodynamically, the canopy is actually more susceptible to turbulence in brakes. Years ago, flying in half brakes seemed to make some older ram-air canopy designs more stable in turbulence, though they were obviously very different from modern canopies.

Flying in brakes is definitely not the best technique to use with the canopies we're flying today, although a lot of skydivers are still told to use this technique.


sammer  (A 43037)

Nov 17, 2003, 8:56 AM
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Re: [breadhead] "Old School" canopy myths [In reply to] Can't Post

I would have to agree with that. In my short (75 jumps) skydiving carreer I have been caught in turbulence quite a few times and I have tried all three approaches: Brakes, full glide and double fronts. The double fronts seem to make the turbulence more violent but the 1/4 brake approach caused my canopy to collapse and reinflate violently pointing the wrong way every time. I was taught that 1/4 brakes are best for turbulence, but I am thoroughly convinced that is bullshit. My canopy is big and lightly loaded, so this might not apply to everyone, but I know full glide works best for me.


diablopilot  (D License)

Nov 17, 2003, 10:41 AM
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Re: [apoil] "Old School" canopy myths [In reply to] Can't Post

Quote:
You don't stow your toggles to make your canopy inflate faster.
you stow your toggles so that you don't open in full flight - which is dangerous if there's any kind of problem like a malfunction or an imminent collision. It also HURTS because it's a faster opening.

I see no reason half brakes would allow for faster reinflation.

Actually you stow them for both reasons.

If you have closed end cells on your main, what do you do to get them inflated? Pump the brakes.

Flying in turbulance should be in full flight. That gives you the best internal pressure, and platform stability to get through the turbulance.

If you suffer a collapse of any sort, pumping the brakes while keeping the wing level till you establish reinflation, or you are forced to flare for landing is the best course of action.

Remember when low to the ground the key point is keeping the wing level, no matter what you have over your head. A partial canopy landed straight in is preferable to a partial canopy landed in a spiraling turn.

As for the inlets being located lower on the nose of a high performance design, think about the angle of attack of the canopy. They are right in line with it. Stay full flight, especially on an elliptical. They have peculiar inflation characteristics sometimes.


rigging65  (D 21921)

Nov 17, 2003, 11:21 AM
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Re: [apoil] "Old School" canopy myths [In reply to] Can't Post

Quote:
You don't stow your toggles to make your canopy inflate faster.

Ummmm....actually...you do. Try jumping without your breaks stowed. The openings are much longer. It takes more time to pressurize the canopy, since there is more volume to fill...among other things.

As for using breaks in turbulence, the most important thing is to keep the wing level. Some say 1/2 breaks, others (PD) say it doesn't really matter. BUT, keeping the wing level and flying the canopy all the time is the most important thing you can do under canopy...regardless of the adverse conditions you're in.


AndyMan  (D 25698)

Nov 17, 2003, 1:16 PM
Post #23 of 43 (2025 views)
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Re: [rigging65] "Old School" canopy myths [In reply to] Can't Post

Quote:
Ummmm....actually...you do. Try jumping without your breaks stowed. The openings are much longer. It takes more time to pressurize the canopy, since there is more volume to fill...among other things.

That's odd. I've jumped a few times without brakes stowed, and each opening has been a slammer...

_Am


Hooknswoop  (D License)

Nov 17, 2003, 1:57 PM
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Re: [AndyMan] "Old School" canopy myths [In reply to] Can't Post

Quote:
That's odd. I've jumped a few times without brakes stowed, and each opening has been a slammer...

I think it depends on the canopy. I jumped an FX w/o the brakes set and it snivelled for 1000+ feet.

The faster the canopy flys, the more internal pressure it has, which helps it resist collapsing, and the more lift it produces, which helps it resist collapsing. The flip side is if it does collapse, you are going faster near the ground and have less time to fix it and you may hit harder if you cant get it re-inflated prior to impact. More speed may make turbulence feel more intense, but that is only because you are flying through the updrafts and downdrafts (or rotors) faster. Kinda like hitting a speed bump slow or fast. Hitting it fast makes it feel harder, but the speed bump is the same size weather you hit it slow or fast. So the best method to keep the canopy from collapsing is the worst thing to do if those efforts fail and it does collapse. The worst thing to do in turbulence is go to deep brakes. This lowers the internal pressure of the canopy and you are more susceptible to the canopy collapsing. You are flying slower, which is good if the canopy does collapse, but it may not have collapsed in the first place if you have been at full flight.

My plan for handling turbulence is full flight until it actually begins to fold up. Then what ever is necessary to get it to re-inflate, keep it flying straight, and keep it over my head. Of course the best plan is too learn where turbulence can most likely be found and avoid those areas or dont jump in turbulent, gusty conditions.

Derek


freakydiver  (D 26421)

Nov 17, 2003, 2:32 PM
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Re: [sammer] "Old School" canopy myths [In reply to] Can't Post

I've found with my Sabre I flying full is the best remedy to turb. Quarter and half brakes only seem to make things worse. My two cents of course.


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