Terminal PCs

[JaapSuter 0]

Hey,

does anybody using a 32 inch PC with a floating handle? Any reason why most people go floating for their 36 or 38 but go external for their 32 incher?

Does anybody have an opinion on 36 versus 38? Or get both? In case the weight of the canopy matters; I'm jumping a vented 266 canopy.

For an 8 second delay off a cliff, what's your first choice; 32, 36 or 38? Would you comfortably use a 32, even when it's not your first choice?

Thanks,

Jaap

[JaapSuter 0]

And while we're at it, does anybody have any thoughts on large-hole mesh versus small-hole mesh for pilotchutes, in relationship to the different available sizes, inflation speed, as well as snag potential for bridle and centerline.

Thanks,

Jaap

[JesseP 0]

38 vented for an 8 second delay would be my choice. I use that for pretty much anything sub-terminal slider-up.

However you would probably find that more often than not, a smaller pilot chute would work as well in some capacity. I know of someone who took a 30" skydiving pilot chute on a 4 second delay from 700ft and got away with it. Another example is a 500ft cliff we have here. Most use a 42, but it often gets jumped with a 38.

For terminal a lot of people use an F111 36 instead of ZP 32. It fits in the BOC better.

In regards to mesh size, BR (Apex or whatever they are now) construct their terminal pilot chutes (F111 36) with small hole mesh. I'm no scientist but I'm pretty sure it has to do with the higher deployment speed. Perhaps they can give you the specific answers you want.

[riggersam 0]

Jaap,
I can't comment on the 32" PC, other than to say it is too small for my comfort. I currently have a vented 265 canopy and I'm comfortable with my 36" ZP on it for delays of 5+ seconds.

Since I'm stepping up to a 322 canopy (looking forward to seeing it soon ), I ordered a vented 38" ZP PC with it - primarily due to weight considerations. Unfortunately, it will probably be a while before I have any terminal or near-terminal experience with that canopy/PC...

Mark

[TomAiello 25]

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Any reason why most people go floating for their 36 or 38 but go external for their 32 incher?

I think that's mostly history. Adam F. put the 38 handle inside, and the 32 outside. Then, the internal got converted to floating, and the 32 got left. Personally, I kind of like the floating handle for everything (but I've got both external and floating handles in both 32 and 38).

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Does anybody have an opinion on 36 versus 38?

I'd ask the manufacturer. I don't know that anyone makes both a 36 and a 38, and the "named" size is less important than the role (i.e. drag and inflation) that the manufacturer is making it for. You may find that a 36 from one manufacturer is intended for the same role as a 32 from another.

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For an 8 second delay off a cliff, what's your first choice; 32, 36 or 38?

38 ZP with a vent.

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Would you comfortably use a 32, even when it's not your first choice?

Yes.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[blair700 0]

I don't have any experience with a floating handle PC, although I've considered it for my 38's...I only use 38" both vented and not for sub T slider ups...and I WOULD feel comfortable using a 32" for the 8 second delay. Now I always use 32" Vented for terminal, but I've considered going bigger when using a tracking suit. I jump 310 sq foot canopies both vented and non, and have good results with the above setups.
I'm 'guessing' the reason folks tend not to use floating handles on 32's is that is 'usually' a terminal PC, whereas my understanding is that most PC/bridle entanglements have been documented in the sub-terminal environment. Except in skydiving...but of course you know, this aint skydiving
Read....'guessing' and 'usually' etc, cause I don't really know, just sharing what works well for me with the larger-ish canopies.
YMMV
Later
Blair

[DexterBase 0]

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For an 8 second delay off a cliff, what's your first choice; 32, 36 or 38?

38 ZP with a vent.

I that with your particular equipment configuration, or across the board?

Would a person with a 310 and a person with a 185 experience similar results with this airspeed and pilot chute?

The mass you're trying to decelerate can certainly come into play. I think at the extreme ends of the canopy size spectrum, the PC selection may matter a little more. In the middle sizes though, it probably matters slightly less.

At airspeed approaching terminal, a 32 has SOOOOO much drag. I've always thought it would be fun to sew a soft handle onto the end of a bridle and pitch a 32" PC in freefall then attempt to hold on to the handle. I'm just afraid what it would do to my shoulder. I'm positive there's no way I'd be able to hold onto the damn thing though.

[TomAiello 25]

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...whereas my understanding is that most PC/bridle entanglements have been documented in the sub-terminal environment.

I can think of a BASE fatality with a PC/bridle entanglement at terminal, on a wingsuit. I suspect the wingsuit increases the likelihood of this malfunction, as there have also been a couple cases of this reported on skydives, which you can find if you dig through the wingsuit forum.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[TomAiello 25]

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For an 8 second delay off a cliff, what's your first choice; 32, 36 or 38?

38 ZP with a vent.

I that with your particular equipment configuration, or across the board?

My configuration. I'd do it with any of my canopies down to 260 though. With a 240? Hmmm. A toss-up, I guess. I'd probably be happy with whatever PC I had on there.

I've seen a 32 used at 5 seconds on a 300+ canopy repeatedly with no adverse effects.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[blair700 0]

Righto Tom, I should've clarified, I don't 'really' consider wingsuit as a 'terminal' jump, even though I know your vertical decent rate is decreased significantly, your horizontal speed increases greatly
...hence one of the reasons I use a 38" on WS BASE jumps. I think I'm familiar with the fatality you are referring, and wasn't this on a 'hacky' style handle?
I do understand what you are saying, just wanted to clarify my statement.
Later
Blair

[JaapSuter 0]

Thanks for the replies everyone.

Somebody brought up an interesting point. I'm planning on jumping with my Phoenix pants and jacket. I'm also fairly tall, but very light. All that results in a terminal falling speed that is far below average.

Now imagine that worst case scenario, I'm using a 32 inch PC, and I chicken out or I count too fast, and I pitch at 6 seconds....

Am I going to die?

Mmm, perhaps I should just borrow a 36/38 from somebody. Should be no problem.

My own 38 is on order already. Thanks everyone!

[TomAiello 25]

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I think I'm familiar with the fatality you are referring, and wasn't this on a 'hacky' style handle?

Yep. It was also the incident which spurred the development of the floating handle.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[TomAiello 25]

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All that results in a terminal falling speed that is far below average.

Are you certain?

I haven't done the math, so I don't really know, but remember that you need to add your downward and forward vectors to determine your actual relative wind speed during deployment. Wingsuits and tracking garb decrease the vertical vector, but they increase the horizontal vector--I'm not sure what the net effect is.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[JaapSuter 0]

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Are you certain?

Yeah, because I just stall out my tracking suit and fall straight down.

Kidding. You're right, that's something I hadn't thought of. Duh...

It's one of those things. It'll probably work, but for my first slider up base jump, I'll feel better at the exit point with a bigger PC. I've taken 42 from 300ft, but I feel better with my 46. Same in this case.

Thanks!

[brits17 0]

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It's one of those things. It'll probably work, but for my first slider up base jump, I'll feel better at the exit point with a bigger PC. I've taken 42 from 300ft, but I feel better with my 46. Same in this case.

Good thinking. Decisions like that will keep you alive... or at least give you optimum opportunity.

I thought it was interesting when you asked about marquisette netting vs. large hole mesh on a BASE pc. I originally thought large mesh would inflate faster, seemed logical to me. But I did a search and found there were some very good information regarding PC inflation. Quoted from Treejumps:
A pilot chute generates lift exactly as a ram air canopy does, by having the air flow over the wing (around the round canopy).
in this thread.

So in conclusion, I'm not sure it would matter what type of mesh you'd use for a terminal jump. I'd like to hear more theories on this.

_______________________
aerialkinetics.com

[JaapSuter 0]

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So in conclusion, I'm not sure it would matter what type of mesh you'd use for a terminal jump.

I'm pretty sure it matters, although not by how much.

Assume for a moment that Treejumps is right about this, which I'm not entirely convinced of, the pilotchute would still have to get to its wing-like shape before the effect fully kicks in. For this to happen, air needs to enter the volume in between the mesh and the ZP.

Now reason ad absurdum; instead of the mesh part, use a solid fabric with only a tiny hole at the bottom. Is this PC going to inflate fast? I doubt it.

A small-mesh hole will let less air through than a large-hole mesh, given the same amount of pressure and time. Hence, a large-hole mesh inflates faster.

This reasoning won't hold up scientific scrutiny, but 460, 736, 974 and all other intelligent people on this board can just look away for second. I'll trust my instincts and what manufacturers tell me.

[JohnnyUtah 0]

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I thought it was interesting when you asked about marquisette netting vs. large hole mesh on a BASE pc. I originally thought large mesh would inflate faster, seemed logical to me. But I did a search and found there were some very good information regarding PC inflation. Quoted from Treejumps:
A pilot chute generates lift exactly as a ram air canopy does, by having the air flow over the wing (around the round canopy).
in this thread.

Thats the post where Tree (Treejumps) exclaims that:

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Pilot chutes do not capture air to inflate.

a PC is not a air capturing device.

Im sorry, and Im not trying to take a dig at Tree, but those two statements have got to be two of the dumbest things I have ever heard.

Regardless of what the air pressure is on the outside of the material, a PC captures air to inflate. That is what holds its shape.

Have Fun, Don't Die!
Johnny Utah
My Website
email:[email protected]

[JohnnyUtah 0]

A post of mine from that same thread.



Some basics:

Square canopy
A square canopy is an airfoil, a wing, a glider. The pressurized wing generates lift because it is an airfoil shape. In this thread, round canopies seem to be the topic, so…

Round canopy
A round canopy is a drag device. The canopy captures air as it is pulled in a direction. This capturing of air pressurizes the canopy with static pressure holding the round canopy in its inflated shape. The shape of the round canopy creates drag, which is the opposing force to whatever is pulling the payload in the said direction (i.e. gravity). It is this drag that allows a person to land with a safe rate of decent under a round parachute.

Inflation of a round
For a round parachute to be considered inflated, it needs to be pressurized with air. For air to get into the round parachute, it goes in through the opening at the skirt, not the apex. Air exits through any hole at the apex.
During a round deployment with some airspeed, the canopy starts out in a stretched out streamer type of shape. The skirt of the canopy is gathered together in the center and therefore the opening at the bottom is very small if any. Because there is some airspeed, the airflow across the canopys outer surface creates a low pressure. Since there is a lower pressure on the outer surface of the canopy than on the inside of the canopy, the streamer shape begins to expand. The opening at the skirt begins to expand as well.
As this happens, air does go in there.
The air keeps collecting inside there, and it is at the apex of the canopy where it collects for the most part. Once the opening at the skirt becomes large enough to let in enough air to completely expand open and pressurize the canopy, then that is what happens.

The low air pressure on the outside of the canopy during initial inflation, helps the canopy change from a streamer shape to an expanded, more open shape.

IMHO- If a round parachute were deployed with its skirt completely opened up (full diameter), then it would inflate (pressurize) immediately and the need for an external low-pressure to help expand the streamer and open the skirt up (as during initiating inflation), would not be needed. I agree that the static pressure created by the canopy capturing air is greater than the external pressure and therefore the canopy stays open.

Pilot Chutes
I have no doubt in my mind that when doing a high airspeed deployment, there is a low pressure created on the outside of the PC which helps it to initially expand. It seems to work very well and that is why I use a regular mushroom for those types of jumps.

In this thread we were talking about a very low airspeed PC hesitation. My point of view is that if you can get the mesh/rip-stop seam of the PC opened quicker (and reliably) on its own, then air will go right in there and pressurize the PC that much quicker. That is why I was mentioning the Super Mushroom. Thats its purpose.

If you pack the PC so that it is dependent on airspeed to begin to open, then you need sufficient airspeed at deployment time or enough altitude to get away with a hesitation (like we see in the video).

With the regular mushroom, sometimes you can do a throw and go and the PC opens immediately with nil to very little airspeed. I believe this works because enough air successfully flows through the opening of the seam and successfully inflates it. However, sometimes the airflow is not so successful to get in and inflate the PC at low airspeeds with the regular mushroom. The result is an occasional hesitation. In the video, it probably hesitated until an external low pressure did happen and helped get the PC to open. Not ideal in my opinion.

Have Fun, Don't Die!
Johnny Utah
My Website
email:[email protected]

[toni 0]

Hello Jaap

I use following (with FOX 245 and FLIK 242)

4-6s:
38', ZP, large mesh

6-12s:
36', F111, fine mesh
36' ZP, vented, fine mesh

I began useing the 36', after I felt that the snatch-force of the 38' PC became very hard, the moment when the PCs work is most important. The opening speed after line strech was feeling the same than with a 38'.

>12s: 32', vented, fine mesh
I used quite some time the 36' on delays up to 15'. At some spots, where it is better to pull in full track, I felt a big difference between 36 and 32, I began useing the 32' from 12seconds.

This is just to give a different input about the PC sizes, since I see that people tend to use bigger sizes than I use. I think, that useing too big PCs can be very bad too, not only because of the harder opening more I think about of line-overs/twists/off-headings (I think that a too big PC and not useing a good direct slider control is the main factor of slider-up line-overs).

For your questions:

- Floating handles I don't use.

- 36' vs. 38': Get both

- 32' for a 8s delay: Sure, it works fine, but to feel confident: It depends...


Hope it helps
/t.

[JohnnyUtah 0]

Good post toni.

My preferences are mostly the same as yours.
I prefer my 38-inch PCs to be vented.
I currently have large-hole mesh on my 32-inch PCs.
Have you had a chance to compare a 32-inch with large mesh against a 32 with fine mesh? If you have, just curious what you thought. Thanks.

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- 36' vs. 38': Get both

I agree. Jaap, there will be times when you will want one over the other.


Along the lines of what toni is saying about too much snatch force and malfunctions/line-twist/off-headings.
You want to always consider the degree of center cell strip your set up will cause on that jump.

Here are a few excerpts from a post I wrote a while back in this thread about center cell strip:

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{Center Cell Strip is a result of too much snatch force (such as having too big of a PC at terminal). What causes center cell stripping is that the cocoon is extracted too quickly from the container.}

Center cell strip is just exactly what it says; when the center cell is stripped off the packed canopy (cocoon). This happens when the opposing forces between the bridle and the jumper are high during container opening. The bridle yanks (snatches) the attachment point away from the jumper so fast that the heavier part of the packed canopy (cocoon) cannot keep up. In other words, the majority of the packed canopy stays in or closer to the pack tray, as the center cell is stretched vertically by the attachment point being yanked upward by the bridle. Whew!!! That was a mouthful.

To simplify:

Let us define an anchor, as that force, which pulls against the jumpers fall, causing the canopy to come out and play.

Let us create and define a new term called, extraction speed. Extraction speed is how fast the anchor pulls the canopy out of the container. This speed is determined by the total force downward (jumpers fall rate and exit weight), minus movement of the anchor (like in the case of a pilot chute).

My definition of Center Cell Strip is: When the center cell is stripped off the packed canopy (cocoon), as a result of an extraction speed that is too fast.

A go and throw, would cause the slowest extraction speed (that I can think of right now). Its extraction speed is only slower than that of a S/L or PCA because the pilot chute moves with the jumper. A S/L or PCA also have a very slow extraction speed (unless you are using a hypothetical 40 foot static line or bridle).

Center cell strip distorts and undoes your pack-job. At or close to terminal velocity, there is always some degree of center cell strip (unless you are using a sleeve). The goal is to minimize it without causing too lengthy of a deployment.
The more center cell strip you have, the greater the chance of having a malfunction/line-twist/off-heading.

edit to add:
If you are ever unsure about the best PC size for a particular jump, my philosophy is:
It is safer to error to the side of one size too big instead of one size too small.

Have Fun, Don't Die!
Johnny Utah
My Website
email:[email protected]

[nicknitro71 0]

1. Where you live there is no terminal object
Are you going to Europe any time soon?

2. This is my set up (ACE 240).

0-1.5 46" Z-po vented no handle large mesh

2-4 42" Z-po non-vented disk large mesh (soon to be replaced)

5-8 and WS Z-po 38" vented internal handle large mesh

Terminal Z-po 32" vented external handle small mesh

I am making a 42" now that will look like a tandem drouge but vented. The specs are: Z-po, internal handle, vented. Bottom skin: the skirt will be fine mesh (about 1") , then z-po fabric (50% of the length), then fine mesh again (the other 50%).

Memento Audere Semper

903

[Treejumps 0]

AHhhh, the old PC debate returns to the forums Via Winkleport.

You really must listen to yourself more often if that is the dumbest thing you have ever heard. Since the thread and debate has been had before, I'll just let anyone who is (still) interested go back and read the thread. As I recall though, the genreal concensus was that whatever you said was right, and everyone else was wrong, reality not withstanding.

2 things we know for sure. 1. A PC works on the priciple of lift. 2. A PC will inflate using f-111 in place of the mesh. (how does that air get scooped up into the pc if there are no holes?

[crwper 7]

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Now reason ad absurdum; instead of the mesh part, use a solid fabric with only a tiny hole at the bottom. Is this PC going to inflate fast? I doubt it.

I don't know how fast it will inflate in the BASE environment, but this is what's used for Relative Workshop's reserve pilot chutes. It like one big nylon bag over the spring. The reasoning here is that if the pilot chute comes out sideways, a conventional pilot chute loses some drag since the air can flow straight through one side of the mesh and out the other. With an all-nylon pilot chute, the drag is about the same regardless of orientation.

I don't know if it's fast enough for the BASE environment, but RWS seems to think it's fast enough for a reserve deployment system.

Michael

[Zennie 0]

Personally, I use the following PCs for the following delays.

0-1: 46" ZP apex vented.
2-5: 42" ZP apex vented.
5-12: 38" ZP apex vented. Internal non-floating handle.
12+: 32" ZP apex vented. External handle.

I have a 36" non-vented with an external handle but I never use it. I opt for the 38 or 32 depending on the delay.

For an 8 second delay I'd go with the 38. I'd use the 32 given no other choice.

Of course there are exceptions to every rule. Just the other night my jump buddies (*cough*brit*cough*chris) banned me from trying a gainer at 300 so we climbed up to about 450 or so. I set up for a very short delay so I had my 46 with me. I wound up taking about a 3 or so with no problems. Like Johnny pointed out, I was erring on the larger side so it really wasn't a big deal.

Just out of curiosity, has anybody noticed a difference in inflation times when going stowed with a 46+ vs a 42? I've noticed on a couple of occasions now that the stowed 46 seems to inflate a tad slower than the stowed 42. Almost like there's a point of diminishing returns as the PC gets bigger and there is more fabric to unfold & inflate.

- Z
"Always be yourself... unless you suck." - Joss Whedon

[Zennie 0]

I'm no fluid dynamics expert, but I did stay at a Holiday Inn Express last night.

I’m wondering if we actually have two discussions going on here. The discussion in the referenced post seems to relate mainly to the mechanism by which a PC or other round canopy inflates. That is, there is a pressure differential between the inside and the outside of the parachute which causes air to be drawn in. This is also the same principle which causes a square parachute’s cells to pressurize (which I think is what Brit was driving at).

You physicists & aerospace engineers correct me if I’m wrong here, but that said, once inflated/pressurized, I don’t think you can say that round and square canopies operate on the same principle.

As best as I can tell, both are drag devices. Both have an underskin which provides air drag/resistance to counter the downward force of gravity. The round parachute, by virtue of its shape, is a pure drag device. It cannot, as best as I can tell, produce lift. A square canopy has more of an airfoil profile which DOES produce lift. That lift is produced by giving the foil an angle of attack which generates forward momentum and thus forces air to flow over the top and bottom of the canopy.

For instance, I don’t think you can get off the ground by attaching a motor device to a round parachute. It will just slow down your forward progress. You CAN, however, attach a motor to a square parachute and get airborne.

- Z
"Always be yourself... unless you suck." - Joss Whedon