Pie Slice Pilotchutes

[JaapSuter 0]

Does anybody have any opinions on pilotchutes where each pie slice is its own unique piece of ZP fabric?

I'm aware that Asylum's Toxic also has the vents moved, something I can potentially see as an advantage. But I'm not convinced the advantages of more symmetric fabric loading are worth the introduced complexity of the extra seams.

I ordered a Toxic to check it out, but I'm curious what other people think. Not just about the Toxic, but about pie-slice based PCs in general.

Thanks,

Jaap Suter

[d_goldsmith 1]

I don't know a ton about it, but what has been explained to me is when they do the pie slice method it gives them the ability to line up the block and bias so that the material is as stucturaly perfect as possible. If the block is lined up incorrectly to the seems the PC will strech under load and probably oscilate.

Maybe you already know this and you are asking a different question, but if not, grab one of your PC's and look at the block pattern. If you poll from corner to corner it will strech, but from flat line to flat line it won't.

[JaapSuter 0]

Yeah, that's what I meant referring to the "more symmetric fabric loading". I suppose I could have explained that better.

Part of me is imagining a pilotchute of which one spoke blows up. On a single-piece pilotchute, you'd probably generate enough drag still (albeit asymmetrically), whereas on a multi-piece pilotchute you now have a big hole across half your pilotchute, significantly reducing drag.

Now I'm sure Asylum (or any other manufacturer that makes PCs this way) assures me that the seams just won't break, but in a sport where the working of a pilotchute is the difference between life and death, I'm not sure if I want to tinker with a proven design.

That said, Asylum's QA has always been phenomenal so I ordered one and will see what it's like.

[980 0]

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line up the block and bias so that the material is as stucturaly perfect as possible.

How they line up the block or bias relative to the rest of the pilot chute has no bearing on the structure of the material.

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If the block is lined up incorrectly to the seems the PC will strech under load and probably oscilate.

The ZP(or Low Porosity) material in the pilot chute stretches/deforms under load no matter how the seams are oriented.

The amount of deformation can be minimised by orienting the reinforcing tapes along the bias, as this is the direction that the material will deform in the most under load.

Maybe you already know this and you are asking a different question, but if not, grab one of your PC's and look at the block pattern. If you poll from corner to corner it will strech, but from flat line to flat line it won't.***

It still stretches, just much less.

Jaap - I think there can be real advantages to this idea.

Just look at a tandem drogue and the level of complexity in its construction.

With a pie-slice construction method, you can now shape the top skin of the pilot chute into a half toroid rather than a deformed hemisphere.

Or you can use more ripstop and less mesh, a la vector reserve pilot chute.

Maybe that is the way to go, no mesh, but with more vents, some of them being one-way, like bottom skin inlets. A pilot chute that will start inflating no matter which orientation it hits the air stream in.

I am not sure I understand what you mean by ‘blowing a spoke’?

To me the possible failure modes of a one piece ripstop pilot chute are far worse than a segmented pilot chute.

I think the number of reinforcing tape spokes make a real difference here, more makes for a less catastrophic failure and probably extends the life of the pilot chute too.

My form of cheap insurance is to replace my pilot chutes every 50 jumps or so if they are treated nice.

Cya
Sam

[base935 0]

Why haven't pilot chutes evolved since they began as a circle of mesh and a circle of fabric? Does anyone disagree that pilot chutes/oscillations are a primary cause of off-headings?

Then why aren't pie-shaped, round-style PCs making an entry into the market? Besides being rounds, I don't think anyone would want to jump a round into the ID bridge if it had suspension lines as long as the radius of the fabric! Then why would PCs have to be so primitive and potentially trouble causing? Lets advance pilot chute technology next, unless someone has a better place to continue...

Gravity Research Institute

[460 0]

Why bother? It's too much trouble making them that way. The old para-innovators from many years ago used to have independent gores, but expense was no issue since it was military related.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[hookitt 0]

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Why bother? It's too much trouble making them that way.

My new "Pie Slice Pilotchute" (Actual name: Toxic) is ready for pick up at Asylum. They're already being made on a limited basis, meaning, you can get one, but there's a long wait time. They're definately more labor intensive. It's an impressive design and built rather nicely.

My grammar sometimes resembles that of magnetic refrigerator poetry... Ghetto

[Calvin19 0]

hmmmm....
i have a lot of PC ideas, not to mention a ton of sewing experience, and a fuckton of spare time these days so, maybe i will.

[avenfoto 0]

seen one in person a few times, and it is extremely nice.. like a mini tandem drouge almost, but lots of stitching involved.

[base935 0]

Ummmm, just for the record- Toxic pilot chutes are not made to look like tandem drogues. The mesh and ZP are the same dimensions...

Gravity Research Institute

[avenfoto 0]

agreed... i dindt say that, and im not a rigger..

[RayLosli 11]

Making BASE PC's more complex in design for the short job it must do of opening and pulling out the Canopy to start it's inflation ? Will there ever be a perfect Hand Deployed PC. That sits in air-movement and Tows without movement ? The perfect human deployed PC is a pipe-dream. PC's these days really do a outstanding job for BASE and they are at there highest point of design and function especially the vented smaller PC's. designed for higher air-flow speeds.
The BASE PC has a important job but it's job is very narrow/specific in function. It must go-out, open, then pull-out. In a Very Short time span. All PC's move around somewhat in the air-flow and the job that the BASE PC does in Free-Fall is nothing in comparison to what a Drogue has to do especially in the long term designs of free-falls where it has a specific job to do that is more complex than just opening and starting the Canopy inflation sequence.
When everything is done right like symmetrical construction, distortion from tread tensions kept uniform throughout construction with proper Tapeing along with a centered Tow. The BASE PC tows strait with movement to a minimum. It simply does its short job very well and for me. I am pretty satisfied with what I am getting and seeing out there BASE jumping.
.
.

[RayLosli 11]

There is also a huge flaw with this Thread. In comparing Drogue construction & BASE PC construction to promote better functional design and is flawed with endless for disappointments in the quest for the perfect hand deployed BASE PC. Flaw in comparing the design, there/SIZE - function/job, length of each in TIME used to complete it's designed job, air-speeds in which each performs it's designed job. Along with the basic one size fits all for Tandem and BASE uses specific sizes for a specific air-speed of ranges.
The quest to become more proficient in BASE is much more important than the quest for a perfect BASE PC.
.

[460 0]

I would be more impressed with an auxiliary custom system to release my spandex pouch and launch the pilot chute away from me in case I was having difficulty with the extraction.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[base935 0]

I can't imagine that PC technology is at a standstill just because it has reached the top of today's technology and ideas. A pilot chute is perhaps the simplest and most critical aspect of the entire operation.

If the pilot chute is oscillating because it is a piece of crap, then your badass canopy with your 2 hour Building packjob is pretty much compromised.

I don't believe that a pilot chute just needs to open at pitch time, pop pins or velcro, get to line stretch, and then it is done. It needs to be a ultra-stable, ultra-reliable, non-oscillating, and pull in the desired direction. (UP!) Kind of makes you think of a miniature water round or Army round.

The canopy when it is coming off your back isn't a canopy. It is a bunch of nylon folded and pressed together, and the direction and force of the pilot chute pulling on the center of the topskin is a EXTREMELY critical time in both the lives of you and your canopy. Simply, if it isn't pulling straight up, your canopy is going to be influenced in that direction.

I am not a rigger, manufacturer, or any of that stuff. I just love to jump and watch videos if there is any light. But a significant percentage of the off headings that I have watched are due to the packjob coming out perfectly straight and on heading- but pointing straight at the wall. The pilot chute comes out wobbling, pulls the packjob out as expected, twisting and oscillating, and the packjob gets turned around at the mercy of a PC that is pulling anywhere but straight.

Pilot chutes can be improved. They have been lately, but I used to have a 32" PC that I use for slider up that gave me 180s most every time. And when you watch the videos, it shouldn't surprise you. It looks like a propeller behind me, and the canopy with a nice packjob just goes where it is pulled. In this case, anywhere but straight. Replaced with one that doesn't suck, I have great, solid openings.

Now the question is how to make PCs that are a little more than a disc of mesh and ZP. If need be...

And Ray, I would be really interested in learning your opinion of how many off headings are the result of PC oscillation. And this isn't just limited to oscillations- why do jumpers still accept that PCs just don't inflate sometimes, or hesitations are just part of the game?

Gravity Research Institute

[bert_man 0]

this has probably been thought of already, and i'm willing to bet that there's a good reason for this not being done, but i'm bored so here goes anyway:

To decrease/eliminate PC hesitations, what about introducing some kind of rigidity or memory to the design? for example, a thin, flat, flexible length of plastic sewn into each radial reinforcing tape? I'm talking only a slight amount of stiffness, so upon extraction the PC spreads open a little bit rather than staying stuck together until the airflow pulls it apart? But not stiff enough to cause bridle entanglement issues.

Has anyone tried this, and if so, what problems did you run into?

-Ghetto
"The reason death cannot frighten me, is because life has cured me of fear."
Web Design
Cleveland Skydiving

[460 0]

That's the way my specially designed 49 inch pilot chute works. Very stiff tapes to cause it spring open.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[base935 0]

Have you seen any others like it?

Has it worked well enough that a very light stiffener would be practical/reasonable/efficient/a general good idea?

If this is just another good idea that is a bad idea in practice, thats all good. But it might have saved some lives recently.?

Gravity Research Institute

[460 0]

No, I have not seen others like it. It was custom designed by my friend Walt Appel. I had no problems with it, but I was always going hand held.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[d_goldsmith 1]

Maybe something like the image I attached, so you could stow it too. Excuse the penmanship, it wouldn't let me use the text option in paint.

Even if it is a very light springy plastic, it still might way the PC down though and cause hesitation.

[460 0]

Any nick on that plastic is likely to capture the mesh and prevent the pilot chute from inflating. I suggest more rigid external tapes.

Looks like a death sandwich without the bread - Steve Deadman Morrell, BASE 174

[RayLosli 11]

..."I am not a rigger, manufacturer, or any of that stuff. I just love to jump and watch videos if there is any light. But a significant percentage of the off headings that I have watched are due to the packjob coming out perfectly straight and on heading- but pointing straight at the wall. The pilot chute comes out wobbling, pulls the packjob out as expected, twisting and oscillating, and the packjob gets turned around at the mercy of a PC that is pulling anywhere but straight. "

..."And Ray, I would be really interested in learning your opinion of how many off headings are the result of PC oscillation. And this isn't just limited to oscillations- why do jumpers still accept that PCs just don't inflate sometimes, or hesitations are just part of the game? "

-

I wonder what the percentage of those osculated caused deployment Canopy twist was caused by.
.
1- Pilot Error in non-centered Bridal attachment ?
2 - Simply not keeping good symmetry or distortion non symmetric due to bad-non-consistent Thread tensioning on Seams and Tapeing ?
3 - Pilot simply does not know his PC. what habits good/bad or unaware or unable to identify a plan and simple un-balanced Pilot-Chute ?
-

I don't know if it's a matter of just total acceptance of the VERY rare PC total malfunction. PC's do hesitate on inflation this is a documented fact and Given enough altitude most any un-inflated PC will most likely inflate. The biggest risk that must be accepted is that the human error in judgment on the mechanics of Packing and the Grasp & Pitch out plus the human element in the Manufacture and QC is the biggest risk any BASE jumper MUST accept without choice. pilot/human error is the big killer. not your PC
I feel that the level of performance I get when I throw my PC to the wind is Acceptable and Satisfactory. I am happy with the level of design at this point in BASE.
Would not the manufacture of a much more labor intensive and complex PC design be more inclined to the human error not mechanical malfunction ?
.

[yuri_base 1]

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I wonder what the percentage of those osculated caused deployment Canopy twist was caused by.
.
1- Pilot Error in non-centered Bridal attachment ?
2 - Simply not keeping good symmetry or distortion non symmetric due to bad-non-consistent Thread tensioning on Seams and Tapeing ?
3 - Pilot simply does not know his PC. what habits good/bad or unaware or unable to identify a plan and simple un-balanced Pilot-Chute ?

There's an interesting physics problem: double pendulum. "A double pendulum is a pendulum with another pendulum attached to its end, and is a simple physical system that exhibits rich dynamic behavior. Above a certain energy its motion is chaotic."

Extracted canopy and PC at bridle stretch make a double [inverted, driven by drag and gravity] pendulum. Could it be that some PC oscillations can be caused not by asymetry of the PC, but by chaotic double pendulum effect? (A recent antenna strike in Russia, when the properly centered and symmetric PC wildly oscillated and caused 180, is one example.) If we can figure this out, then perhaps this tendency for chaos can be reduced by chosing a certain ratio of bridle length to line length and PC weight to canopy weight? Kind of avoiding the resonance frequency.

See the attached animation. Looks familiar?

Yuri

Edited to attach an animation.

Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

[d_goldsmith 1]

Wow. I never though resonance frequency would have anything to do with deployment, but that is a sound theory.

[bert_man 0]

but then again, its not really a double pendulum system until linestretch, is it?

-Ghetto
"The reason death cannot frighten me, is because life has cured me of fear."
Web Design
Cleveland Skydiving