Basejumper.com - archive

is there any information out there as to the different pull forces of various pc's?
for example, in a controlled setting such as a wind tunnel set at a known wind speed (lets say 50 mph) measuring the pull force of the 3 different types of 42" pc. zp, av zp and f111.
how much more pull force would a av zp have vs. an f111? my gut feeling is that theres not a huge difference in drag force by having a vented hole in the apex of the pc as opposed to the entire surface made from f111.

i prefer f111 for all my pc's for various reasons. although i dont get nearly as many jumps on them before i need to change them out for new ones i prefer f111. im guessing im in the vast minority using f111 for a 42".

i also suspect the difference will be negligable wen comparing vented pcs to non vented. i even bet f111 is not that much different.

but varios PC designs i think would matter. such as Vertigo ZP 42" vs morpheus 42", etc.

I'm embarrassed to say we tested early pilot chute designs by hanging them out car windows while speeding down deserted back roads (it doesn't work too well). I think you can say the move to ZP began when Will Oxe had a pilot chute failure on a low cliff jump with a F-111 pilot chute. The simple thinking being at low speed ZP just naturally wants to expand more than F-111.

But also at that time, B.A.S.E. jumpers were just beginning to go stowed, and pilot chute folding wasn't the art it is now. We were all rolling and folding it for stowing, like we always did at the DZ.

ZP is probably overkill in most situations, and I'm fine with using F-111. But when you only have one canopy, the question you have to ask yourself is -what exactly is overkill?

NickD
BASE 194

I've always felt the purpose of having a ZP PC over an F111 was for increased snatch force, not necessarily a significant increase in drag.

i was shot down/given a reall bad look when i asked our local 14' wind tunnel guys if i could buy time and test PC's in there. i can see why they said no, really kinda scary. I have a really accurate electronic load cell (measures pull force to the tenth of a kg) that would have been perfect, even would have had the burble of a freefalling body there as well. bastards.

like this one?
I´ll let the person who made it speak up..

It were posted at Blinc serval years ago..

my comp couldnt recognize the file.

its a word file,heres a similar in pdf

thanks, got it. however im just a simple man so that my as well been hyroglyphics. ;-)

(edit: "diminishing factor" was set on 1.5)

Code

Afaik these are not based on tests and measurements, but merely theoretical calculations.

We did some testing in a wind tunnel a couple of years ago, of 14 different pcs, various sizes and designs. Based on those tests one of them where discarded and another one that where suspected to be a little dodgy actually turned out to be really good.

Anyway the results are collected in this excel sheet. Look at the sheet called "tab" and you'll see the chart with all the forces/velocities on the different pcs. Tests where done on three different speeds and calculations and interpolations give the curves. Feel free to ask if something is unclear.

Hans

so it's more than enough for opening ??

 
Stupid question: If 48' forse after 10 sek - 129 kg, my weight 80 should I fly up if I will jump with 48' pc as main canopy :0

No you won't fly up. the PC will anchor and you will get slammed. Thats how I see it anyways.

edit: nm re-read your post, you want to use the PC as your main? those figures were for the initial pull force on the pc. might be a fun ride, but you'd only get to try it once.

Hello Han-Solo,

I'm looking for some new PC's, can you interpret your results into words for the consumer me.

For the 8sec plus delays (Lauterbrunnen up to Kjerag), doing tracking jumps, what PC's should I be looking for?

32", 34", 36" or 38".
Apex vented ZP or F111?
4, 8 or more radial reinforcement tapes?
Small mesh or big mesh?

Looking forward to your analysis.

Cheers.

Mike.

Assuming you just used the PC, since the PC's force exceeds gravity's force (your weight), you would slow down at the rate of whatever the difference between the 2 were until they equaled. At this point, you would be at terminal velocity for whatever amount of drag you + the 48" would create.

Force is acceleration. You can't "fly up" unless you're experiencing acceleration in an upward direction and your speed is 0. If your speed is in the down direction, you have to be slowed down first by the acceleration before you can start to move upward.

Now, if you got in a wind tunnel with windspeed at 10 sec, and held a 48" PC, you would be lifted out of the tunnel.

dont explain that shit to stupid people. I love it when random people ask 'how far do you get thrown up when you throw your chute?'

just keep a straight face, and say 100-200'

Hi Hans,

Those number are great.

I don't suppose anyone has any real data of how much pull force is actually required to extract our standard curved pin from a standard dacron closing loop? I am very aware that this would be dependant on pin tension and other factors too that I haven't thought of yet. (maybe the speed of pin extraction?)

Would this be all to hard to measure because of the pin tension factor?

Dacron closing loop? i thought we used nylon...

and testing that would be easy, i would do it right now, but my load cell has incriments of .5kg.

results would vary a lot, from body postion (container tension) to individual packjobs. but it would be worth a shot.

Fairly good chance I'm wrong, you do more rigging than I do.

I generally always pull test a rig when I get it. I usually take my sloppiest pack job and jam it closed. Then tuck up into a ball and have someone pull test. Usually that number is around 22 lbs. That's the worst case I've ever gotten. If you are a neater packer I'd imagine it would be much lower even in a tucked up configuration.

22lbs is a pretty high number for pin tension! but good job on the tests. I really doubt my worst packjob is that tight, but maybe i should test it. I was guessing mine are around 3lbs at worst.

I agree, 22lbs seems pretty high. Thats standard tension for a skydiving reserve. I would never pack my main to anything like that (No base exp. yet, so I cant comment there but that still seems tight)

for this kind of jumping i'd go for 34 f-111 or 0-p vented from any manufacturer that makes a handle you like. but that's just me...

pin tension is one thing, but accelerating the packjob out of the container is another.

Are you testing it while wearing it and crouched into a ball with a dirty pack job? That's what I'm referring to.

I haven't tested it at all. I was guessing that my tension/pin force was around 3lbs. I do not have a little hang scale thingy.

First you take the mass of the ass....(X).... the heat of the meat.......this will give you the angle of the dangle

It's physics.

Dont ever open one inside your house, it'll blow you through the roof.

Some of the old school guys like JD Walker, BASE 38, would use a flatbed truck, put a vertical pole on the back (tall enough to reasonable minimize vehicle turbulance), attach a bridle to a pull scale to a bridle and to pilot chute and make measurements. This dictated his pilot chute size and design. No wind tunnel needed...

Your answer, which I like and have used, or....

How far backwards do you go when you slam on the brakes in your car? A little farther than that.

I made a tube for freeflying and tested it
by standing up in my wife's convertible
and holding it.

When I first got a velcro rig try to do a
similar thing with my pick-up truck and
a friend but the burble sucked.

Okay, Ive looked long enough, Im trying to find a PC drag table that simply shows delay and PC size and pull force, in American ie.seconds and feet and pounds. Thanks, sorry to kick a dead horse.

Don't have a table but I do have an Excel spreadsheet
that I copied from this forum, I think Yuri_BASE is the
author, but not sure. See attached.

Are you just curious or doing some re-inventing?

http://tinyurl.com/csebxl

How the fuck did you do that? That was cool!!!

Ive seen this one, the one Im talking about is a simple table, very similar to JohnnyUtah's Freefall data chart clicky I know Ive seen one, well, maybe? hell I dont know anymore, nevermind. Thanks anyway.

Like this <==click

How the fuck did you do that, thats was cool!