Why Don't Skydiving Pilot Chutes Have Vented Apexes?

[tso-d_chris 0]

It seems to me that if round canopies oscillate less with a vented apex then the same principle would apply to pilot chutes. I cannot remember ever seeing a non BASE PC with a vented apex. Is there a reason it is not done for skydiving pilot chutes?

[upndownshop 0]

Interesting
I wonder if it has anything to do with suspended weight vrs pulling force?? therefore no need?? Just a guess.

[piisfish 136]

are there vented tandem drogues ?

maybe the speed of extraction does'nt make the vents necessary. Wild guess

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[wmw999 2,168]

I always kind of wondered about that. To me, it'd seem like part of the reason for the vented apex in round mains is just because so many lines wouldn't fit neatly into the top without their being loose.

Even the PC-type parachutes still had little vents where the lines all crossed over each other on the top.

Wendy W.

There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown)

[davelepka 4]

My guess is that the time spent inflated and doing their job is too short for an ocilation to develop, or get very far if it does.

Tandem drouges and BASE PCs are vented due to longer duration of use, and the importance of a clean deployment in BASE.

Just a guess though.

Let me add that a skydiving PC with vents would need to be reinforced around the venting, adding significant bulk to the PC. Otherwise I would guess they would wear in that area very quickly.

Again, tandem drouges and BASE pc are reinforced in this area, but their bulk really isn't an issue.

[AndyMan 7]

It seems to me that venting trades pull-force for stability. A vented parachute is more stable, but provides less drag.

Opening a parachute is such a quick action that stability of the pilot chute isn't the important bit - but a good strong initial pull force is. Maybe?

Hopefully the guy that designed it will chime in...

_Am

__

You put the fun in "funnel" - craichead.

[wmw999 2,168]

No inventor here, but pilot chutes never had apex holes. Before Bill invented the throw-out, they all had springs (MA1, A3, and their ilk). Even the hot dog (a sport spring pilot chute). Some had semi-hard caps on top, some didn't. All the military ones I'm familiar with had vanes, and the sport ones either were just prettier military, or were like the Hot Dog, which had mesh on the bottom half.

I wouldn't be surprised to find that pilot chutes, and not round mains, were the model for the throw-out. In the early days, I used a spring-loaded one with the spring removed for a few jumps, but it didn't work really well.

Wendy W.

There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown)

[mjosparky 3]

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It seems to me that if round canopies oscillate less with a vented apex then the same principle would apply to pilot chutes. I cannot remember ever seeing a non BASE PC with a vented apex. Is there a reason it is not done for skydiving pilot chutes?

One of the main reasons for the apex vent on round canopies is to vent high pressure air during canopy inflation. If the apex vent were large enough to stop oscillation, the descent rate would be to fast to survive the landing.

A 24' flat has an apex vent and oscillate like a SOB. But if you put a couple of vents at the skirt level a couple of gores apart, most of the oscillation will stop.

My idea of a fair fight is clubbing baby seals

[jumper03 0]

a vented apex could increase the likely hood of a streamer - I don't want my pilot chute streamering on me.

Just a guess...

Scars remind us that the past is real

[tso-d_chris 0]

Thanks for that info, Sparky. I was always under the impression the vent was there to reduce oscillations.

For Great Deals on Gear

[tso-d_chris 0]

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a vented apex could increase the likely hood of a streamer - I don't want my pilot chute streamering on me.

Just a guess...

I'm not following the logic behind a vent causing a streamer. Could you elaborate?

For Great Deals on Gear

[mark 105]

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A 24' flat has an apex vent and oscillate like a SOB. But if you put a couple of vents at the skirt level a couple of gores apart, most of the oscillation will stop.

I'm going to agree, then disagree.

In terms of reducing oscillation, I don't think it matters where you put the vents. The pressure is the same everywhere inside the canopy, so allowing air to escape through vents halfway between skirt and apex will be as effective in reducing oscillation as vents near the skirt or vents closer to the apex.

The virtue of vents near the skirt is the vector of the escaping air. The closer to horizontal we can make the escaping air flow, the more effective the vents are as drive windows or turn windows.

And then I'm going to agree again. If the apex vent were large enough to allow the same airflow as vents near the skirt, the descent rate would be greater, again due to the direction of the vented air.

Mark

[jumper03 0]

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a vented apex could increase the likely hood of a streamer - I don't want my pilot chute streamering on me.

Just a guess...

I'm not following the logic behind a vent causing a streamer. Could you elaborate?

well, the vent in the top allows air to escape. They are there to slow the opening of a round. If the apex is too big, too much air escapes and the canopy does not inflate - streamer. Pilot chutes are small - any vent might allow enough air to just flow right through and not let the pilot chute inflate. That would be bad.

or I could be full of it...

Scars remind us that the past is real

[uponone 0]

It sounds like your describing a PC in tow, not a streamer. I was taught that a streamer is your canopy towing behind you in a wad of shit.

[nbblood 0]

Sounds like a pilot chute in tow, not a streamer when the main is out of the d-bag but not inflated.

Blues,
Nathan

If you wait 'til the last minute, it'll only take a minute.

[billbooth 10]

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It seems to me that if round canopies oscillate less with a vented apex then the same principle would apply to pilot chutes. I cannot remember ever seeing a non BASE PC with a vented apex. Is there a reason it is not done for skydiving pilot chutes?

In almost all cases, freefall pilot chutes do their job in under 1 second, so whether they oscillate doesn't really matter, does it? As was said above, adding an apex vent would: 1. Make them open slower, 2. Make them harder to manufacture, and 3. Make them more bulky...none of which would be very helpful.

[tso-d_chris 0]

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It seems to me that if round canopies oscillate less with a vented apex then the same principle would apply to pilot chutes. I cannot remember ever seeing a non BASE PC with a vented apex. Is there a reason it is not done for skydiving pilot chutes?

In almost all cases, freefall pilot chutes do their job in under 1 second, so whether they oscillate doesn't really matter, does it? As was said above, adding an apex vent would: 1. Make them open slower, 2. Make them harder to manufacture, and 3. Make them more bulky...none of which would be very helpful.

The reason I am curious is that I have talked to hard core CRW dogs in the past that swear that, all else being equal, a ZP pilot chute will contribute to off heading openings, whereas as deployments from F111 pilot chute are straighter. I have also heard this elsewhere.

The only reason I can think of for this to be true is because the F111 pilot chutes are venting air through the fabric, having a similar effect as a vented apex. This is a guess, and there could in fact be other reasons.

Additionally, if BASE pilot chutes have the vents with benefit, wouldn't that benefit be increased with higher deployment speeds of skydiving, even if it's not as critical to have on heading openings?

As far as the reduced surface area, that is easily added back with a slightly increased PC diameter. The extra bulk seems like it would be minimal. I understand the extra build expense, but if there was an actual benefit, it seems it would be worth it if there proved to be a benefit to having a vent.

For Great Deals on Gear

[packertom 0]

vented apexes are there to decrease ocillation... that's what they're for.

venting in other places on a round canopy are for the purpose of steering or drive.

some BASE pilot chutes have vented apexes for the express reason or lessening ocillation of the pilot chute, with the intent of decreasing the chances of an off heading main opening. whether this actually works is a point of contention, but if it makes you feel better, by all means...

My only guess as to why sport main pilot chutes are not vented would be that they don't need to be.... having said that, the are intended to operate in the envelope of higher speeds (than BASE), if you open a bit off heading, so what? it's a big sky and there isn't a mountain 20 feet away, and theoretically a pilot chute without the apex might last a little longer... or perhaps it has to do with that fact that it 's easier to build without an apex

an interesting question and an interesting discussion... I know that all of the pilot chutes the we produce, BASE and sport do not have vented apexes (or is it apexi :-)

Tom

www.applieddeceleration.com

[email protected]
www.velocitysportswear.com
What's YOUR Zombie Plan?

[Tonto 1]

980 (DZ.com username) uses a vented PC on his skydiving rig, mainly for Wingsuit dives.

F-111 is my prefered material for PC's, and I like them on the bigger side (32 inch) also for use on wingsuit dives. I have far more consistant openings with F-111 PC's than with ZP PC's. I don't mind replacing them every 200 dives or so.

For me, risers, 3 rings, PC's, bridals, pins and closure loops are the most critical components of any parachute system. They ensure the rig stays shut till you need it, works when you want it to and allows you to escape when it doesn't work. I don't need much more than that.

t

It's the year of the Pig.

[GaryP 0]

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It seems to me that venting trades pull-force for stability. A vented parachute is more stable, but provides less drag.

There is NO LOSS OF DRAG with a vented p/c once it is inflated, compared to a p/c of equal size & construction that is not vented at the apex.

When a p/c is fully inflated and travelling through the air it is being subjected to more air being forced into the p/c from below. Because no more air can be accommodated inside the already inflated p/c the surplus air spills around to the sides out from the bottom of the skirt.

On an apex vented (AV) p/c, as long as the amount of air escaping through the vent does not exceed that which is spilling out from the bottom of the skirt there will be no loss of drag as the p/c is fully inflated and cannot take any more air inside anyway.

It makes no difference that some of the spillage of surplus air is occurring through the apex vent. As long as the p/c is inflated to the degree that excess air is spilling out around the skirt then it's doing it's job.

g.

"Altitude is birthright to any individual who seeks it"

.

[davelepka 4]

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I have talked to hard core CRW dogs in the past that swear that, all else being equal, a ZP pilot chute will contribute to off heading openings, whereas as deployments from F111 pilot chute are straighter.

A subterminal, free packed CREW deployment is much closer to a BASE opening than a standard skydiving deployment. In that case, a vented PC might be applicable, and helpful.

The F-111 PC seems to be the 'poor mans' vented PC in this case. Seeing as everyhting else hangs out of a closed CREW rig, I guess a bulky vented PC would right at home.

[AndyMan 7]

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There is NO LOSS OF DRAG with a vented p/c once it is inflated, compared to a p/c of equal size & construction that is not vented at the apex.

I've heard this before, I just don't get it.

Here's why.

Start with the proposition that a vent at the apex doesn't reduce drag.

Then take out your scissors and make the vent bigger. Then make it bigger again. If you keep making the vent bigger, eventually you'll end up with a parachute that has a strong resemblance to a tube.

Surely a tube has less drag than a parachute!

So, cue the obvious questions:

Why does a big hole reduce drag but a small one doesn't?
How big does a hole have to be before it starts reducing drag?

To me, the answers to these questions just do not make sense given the original proposition. The original proposition must be wrong.

The obvious answer to me, is that a small vent reduces drag by a small amount. A big vent reduces drag by a big amount. Either way, it's still reducing drag.

_A,

__

You put the fun in "funnel" - craichead.

[chachi 0]

probably because it doesnt really fucking matter. the only reason you don't want the pilot chute to oscillate in BASE is do to it causing slight off headings if it gets bad enough. also that happens mostly in non - terminal openings. the speed in which the pilot chute hits the air at, the size of the pilot chute (much smaller), the fact that in skydiving canopies body position is the most controlable factor, and added wear and tear make it useless for manufacturers to go through extra un-profitable steps to make it with vented apexes.

[mark 105]

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The obvious answer to me, is that a small vent reduces drag by a small amount. A big vent reduces drag by a big amount.

For all round parachutes, including those with pulled-down apexes, the air that goes in the bottom has to come out somewhere. It can go through permeable fabric; it can vent through the apex vent or other vents; or it can spill out from underneath the skirt as the parachute oscillates. For a typical round parachute (no pulled-down apex), as you enlarge the vents, you reduce the amount of air spilling out from under the skirt. The same amount of air goes from inside to outside, so there's the same amount of drag, but the canopy is more stable.

You are right, though: at some point as you enlarge the vent(s), the amount of air going through the vent(s) exceeds the amount of air that would have spilled from underneath the skirt. Then the canopy has less drag and descends faster. I think you'd be surprised at how big you can make the vents before there's an increase in descent rate. Modified 28' rags and T-10s frequently had the equivalent of 2 entire gores (triangular section between radial seams, from skirt to apex) removed.

The vent in a vented pilot chute is at the apex, but not at the top. Because the apex is pulled down more or less even with the skirt, the top of an inflated pilot chute is really a ring about half the diameter of the fully open pilot chute.

Whether a pulled-down-apex apex-vented pilot chute has more or less drag depends on how far the apex is pulled down and how big the vent is, which is to say, how much the vent contributes to stability.

Mark

[AndyMan 7]

Interesting. Thanks,

_Am

__

You put the fun in "funnel" - craichead.