Forums: BASE Jumping: BASE Technical:
PC size and type
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Quagmirian

Jul 1, 2020, 6:41 AM
Post #1 of 15 (2282 views)
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PC size and type Can't Post

I'm putting together a rig and I need to make a guess at what PC I want. The canopy is an ultralight 210 and will come in at about 6 lbs. I intend to do 5-15 sec delays and I don't mind getting a bit of hesitation as opposed to ripping the centre cell out. My friend guesses that a vented ZP 32 will suit me. What do we think?

Dadsy

Jul 1, 2020, 6:49 AM
Post #2 of 15 (2279 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

Guessing the size PC you need really isn't a thing, so please stop listening to your friend
You are going to need a few different sizes. I jump Toxic's.
Are you doing a course? Speak to them

Quagmirian

Jul 1, 2020, 12:39 PM
Post #3 of 15 (2250 views)
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Re: [Dadsy] PC size and type [In reply to] Can't Post

Sorry, did I write guess? What I actually meant was 'estimate accurately, taking into account a number of factors'.

Highjinx

Jul 1, 2020, 5:39 PM
Post #4 of 15 (2227 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

Checkout http://www.apexbase.com
go to education/articles and then pilot chute selection

AntoineLaporte

Jul 3, 2020, 10:58 AM
Post #5 of 15 (2120 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

When is the last time you've heard about a center ripped because of a too big PC ?
I never heard of that (that does not mean that it did not happened).
I also would not use the same PC for a 5 and for a 15 seconds. About that I would love to know where you are jumping a 15 second slick ?

Last but not least, do not think about your PC with the delay but with the air speed.
I would use a 38 for the short delay or one piece suits or bigger jumps, 36 for slick / 2 pieces tracksuits any delay.

Best on the market are for now Toxic and Snatch, maybe the new Adrenalin will be good too, but I've not seen it enough in real to recommend it.

Quagmirian

Jul 3, 2020, 1:34 PM
Post #6 of 15 (2107 views)
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Re: [AntoineLaporte] PC size and type [In reply to] Can't Post

I was hesitant when I started this thread to say what I'm jumping from. Suffice to say it will be an aircraft flying low and slow. I won't say what and where because the wrong people could see this thread.

As for the delay, I was very surprised to run the numbers and find that at a 5 sec delay, a pc provides half the pulling force than at terminal, assuming a dead start. What I can't get my head around is why a skydiving pc works over an enormous speed range and a base pc doesn't work over that same speed range.

BodeyM

Jul 3, 2020, 3:02 PM
Post #7 of 15 (2097 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

Just spitballing, I imagine it's slightly less critical to have a sky PC be undersized for the jump and delay the extraction versus a BASE PC needing to provide as consistent an extraction as possible.

RGrove

Jul 4, 2020, 3:28 PM
Post #8 of 15 (2045 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

I use a 36 out of all of the low and slow aircraft jumps. Slick or track suit. And all the way to longer than 15 seconds, if you can get your low and slow aircraft to a higher altitude.

When I was getting out of said aircraft with the 5 second delays the 38 would work better, but the 36 gets the job done. And since there is no wall to hit out of said aircraft, it works nice.

TomAiello

Jul 5, 2020, 2:10 PM
Post #9 of 15 (1994 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

Quagmirian wrote:
I was hesitant when I started this thread to say what I'm jumping from. Suffice to say it will be an aircraft flying low and slow.

How slow? If the aircraft is moving faster it may change things.

I'd say use a 32" for delays of 9 seconds and more. For the 5-9 second range jumps, I might upsize slightly (36, maybe) but you'll probably be ok if you have altitude to spare (meaning you're pulling high on purpose, not taking a short delay because you're low to the ground).

AntoineLaporte

Jul 6, 2020, 10:50 PM
Post #10 of 15 (1914 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

Quagmirian wrote:
As for the delay, I was very surprised to run the numbers and find that at a 5 sec delay, a pc provides half the pulling force than at terminal, assuming a dead start. What I can't get my head around is why a skydiving pc works over an enormous speed range and a base pc doesn't work over that same speed range.

The different sizes recommended for BASE are here to have the more consitant openings because you might have to open close to the terrain and you don't want a slow opening or not enough tension in the bridle that can help causing twists.
A skydiving PC does not work over an enormous speed range compares to BASE PC, it is just here to get the canopy out, and people don't care if it is not the right size to have good opening, they just want opening.

cokaofly

Jul 15, 2020, 4:49 AM
Post #11 of 15 (1741 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

I use 32 'vented for + 12s with two piece TS. I don't feel a difference in the opening time if it was a 36 '(I believe that the difference in the opening time is very small with more than 12s. But I feel the difference in comfort. It is softer). I've also used this configuration with 11 ft bridle and it seemed slightly more comfortable. Now I use 9 ft.

AntoineLaporte

Jul 19, 2020, 9:12 AM
Post #12 of 15 (1620 views)
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Re: [AntoineLaporte] PC size and type [In reply to] Can't Post

I think there is still this what I think misconception that the size of the PC has a big influence on the canopy inflation.
How is that ?
The size of the PC changes how fast (and strong) the canopy is getting out of the container and how fast the line stretch happends.
When the canopy starts to inflate the PC has done his job and does nothing more, so it has no real influence on the canopy opening IMO.
What I think it that because the timing of the opening changes with a bigger PC were are not ready and relaxed like we are with the PC we are used to, so it feels different, but I really don't think it is.

If you want a softer opening you can change your slider.

The choice of the PC should be only based on the air speed and the canopy weight, and the best is to test.
Rear camera, if the bridle-canopy-lines are in straight line during the canoy extraction until line stretch the PC size is good, try a smaller, if it is not a straight line but make a curve like the canopy is "falling" get back to the previous one, it's the good one.

jjmacc

Jul 20, 2020, 3:36 PM
Post #13 of 15 (1554 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

jumping from a slow moving aircraft? www.dropzone.com

want a skydive answer, ask on skydive forum.

unless you're leaving this super secret aircraft at 0mph and 200', any size PC is going to get the job done. If you want specific answers, you need to give specific information. Speed, height, delay, altitude. If you don't give these, how can people advise over the few inches diameter difference on pilot chutes?

Quagmirian

Jul 21, 2020, 3:10 AM
Post #14 of 15 (1525 views)
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Re: [jjmacc] PC size and type [In reply to] Can't Post

I came here looking for advice on how to not kill myself. I've provided details of canopy weight, airspeed and a starting point in size. I ask here because my setup has more in common with a base rig than a skydiving rig, even though it's technically skydiving.

Please take your attitude and piss off.

StraightEdge

Jul 21, 2020, 10:17 AM
Post #15 of 15 (1507 views)
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Re: [Quagmirian] PC size and type [In reply to] Can't Post

This is a BASE-jumping forum. It is you who have the attitude.

If you want advice - genuine and sincere advice - be honest about what you want it for. That means providing full details.

This is not Dropzone.com. BASE is a different activity. The atmosphere may seem unfriendly or unhelpful at times. Humility goes a long way.

PS. I contacted you once before on the skydiving forum with some advice. Feel free to PM.


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