Vented PC's

[leroydb 0]

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Some of us actually take great Pride in being an Ass-Hole when we Post hear.

Leroy


..I knew I was an unwanted baby when I saw my bath toys were a toaster and a radio...

[Faber 0]

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A 46 or 48 is not hanging like a Anchor long enough to start oscillating.
You pitch it out / It's ripping your canopy out of container.

just a side note,you earlyer told that you use your 48 stowed,for how long delays?

If you pop your pc no matter the size it will need the time to fill up the pc whith air before having a pull force.It dont takes much time to fill it up whith air but you actualy have slightly longer time on your 48 than on a 46,which is why some people use a 46 rather than a 48 as it inflates faster it will pull faster...theoretic at least

Personally i only jumped a 48 once and it were a SL jump so it wont tell a thing. But i have freefalled sub 200ft whith a vented 46´

Stay safe
Stefan Faber

[DexterBase 1]

It's probably going to get you to linestretch at the same time.

The 46 will pressurize faster but will have less drag than the 48. The PC will pressurize faster and pop the pins, but get the canopy to linestretch slower than the 48.

The 48 has more drag. It will pressurize and pop the pins slightly slower but once it's pressurized it will take the canopy from the packtray to linestretch faster than the 46.

So, the 46 will start doing the work earlier than the 48 (probably) but in the end, at this delay range, the result is probably going to be nearly identicle. From the outside, it's going to be hard to tell the difference.

What will be easy to notice, will be the jumper with the 48 opening really low because he stowed a PC that was too large and it hesitated for a second before pressurizing and popping the pins. He could have just went stowed with a 46 and reduced the chances of a hesitation. If it was 300 feet to impact, he could have used a 42" PC and taken a 1.5 to 2 second delay and been just fine.

[Rauk 0]

"If it was 300 feet to impact, he could have used a 42" PC and taken a 1.5 to 2 second delay and been just fine."

Dude, speaking of all this, I did a jump from our 300' B, it has that "alternate" landing to the right of the corner we jumped. That makes it 240' to landing, I took a 1/2 second or so off the corner, had a 50 degree right and landed on the 240' landing. It was reasonable, too, I didn't even bat an eye. I was really surprised that on a half second hand held jump with a 42" PC, I was fine at 240' (inadvertantly, but it sure answered a lot of questions I had on accident).

[RayLosli 11]

In Reply To
just a side note,you earlier told that you use your 48'' stowed,for how long delays?
................................

I usually don't delay more than a 2 sec. with no slider.
I believe people were talking about not using a 48 PC stowed because it not safe.
Just because I used a 48'' stowed for years on every no slider jump does not mean
I go stowed on low & shitty jumps.

Dude Pilot-Chutes are a HUGE subject.

I personally believe that "Air Speed" is the factor that does not mater as much on
46'' - 48'' inch pilot chutes. As far as.. bad-time Oscillation.

When you start cruzing over the 4 sec. mark in free-fall... That's the "Judge" of a balanced PC.
....................................

In Reply To
Personally I only jumped a 48 once and it were a SL jump so it wont tell a thing. But I have freefall sub 200 ft with a vented 46''

I have jumped every sub-200' with a 48'' PC.

** Pilot-Chute hesitation can happen to... Any PC & Any SIZE PC.

** Pilot Chutes are all subject to:... The way they were CONSTRUCTED & The Jumper that is " THROWING" it out.

Weight of PC, also Balance....but..... " DESIGN of Efficiency".... is a Big-One.
that is bigger than efficiency ....It's Design of efficiency.
Every manufactures builds them different & has his own design and thought of design efficiency.
An extremely well Designed 42" PC is a lot better than a fucked up 48" PC and visa-versa.

* Jumper
There is a proper way to * "PRESENT" * a PC to the air when you Pitch a pilot-chute to the air.
both... Hand -Held & going... Stowed.

I don't want to get into all that fucked-up argument of the Mushroom & Super-Mushroom CRAP.
* Lets just say..." There is a proper way to fold a Pilot-Chute."... (enough said) on this over talked about subject

The way a Jumper throws a PC out to the air is BIG.... There is a different way to throw a PC out. For different jump situations.
There is ....TECHNIQUE.....In How & when to pitch a Pilot-Chute.
There is also Technique involved in Knowing.... "Which"...technique to use in Different Jumps.
Different pitches for Different Jumps.

* this can all be... Summed-Up.... in 3 Words.......Design, Technique, Timing .

>- A.Well Built Pilot-Chute.....> - Knowing, How to Throw it out..... >- Knowing, When to throw it out.
.
.

[TomAiello 26]

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Also, why are vented PC's only offered up to a 42 on this website? Why not a 46?

Probably best to ask the owner of the website that, don't you think?

I'd guess that they've found the advantages of the venting minimal on larger PC's/shorter delays, or that they've found some problems (increased hesitation rate, maybe?) on the larger vented PC's. You'll note that the other manufacturers of vented PC's _do_ offer vented PC's in the larger sizes, so it's obviously not something that everyone agrees on.

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http://www.baserigs.com/docs/products/accessories/pilot_chutes.html
(haven't figured out the link thingy yet...)

To make a link clicky, put {url} before it and {/url} after it, but use "["
where I'm using "{" here.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[TomAiello 26]

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...is my brand-new (ok...18 jumps) non-vented PC unsafe?

No. As long as it's manufactured correctly, it'll be fine. People used them for years. A vented PC is probably better, but not so much that I'd throw out the brand new unvented one. Before the vents make a difference, everything else needs to be done correctly, so you may as well use that one to learn everything else. Once it's worn out, you'll have the other stuff down, and you can buy a shiny, new vented PC to use with your new skills.

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What is bias? And what does it mean to me as a low-time basejumper?

Ray did a pretty good job explaining. If that's not clear, post a follow up and I'll try to find diagrams. It's _very_ important that your PC be constructed properly, and tapes sewn on the block of the ZP means it is _not_. In my opinion, a poorly constructed PC is a much bigger deal than the apex vents (or lack of them).

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Please don't stop the attitude, hollering and jeering... I really do get a kick out of it. Just try and teach me something at the end of your post. That's all!

Most of the attitude is done with your best interests in mind. Although it may not come across that way in this form, most of those folks are genuinely concerned to not see you end up as a statistic.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[Faber 0]

Ray i do agree in what you say,but as you know trimming is important then i still belive that my 46´is one of the most used tools of my pc´s(well 42 and 46 to say),i also usaly use a 45-46´for my SL jumps.
I know serval people in Europe jump this way aswell.

Stay safe
Stefan Faber

[sabre210 0]

Ray

"Different techniques for different jumps"

You talked of pilot chute presentation by the jumper (pitching, throwing, placing) for both stowed and hand held jumps. I would be very keen to hear yours (and other experienced jumpers) techniques for folding and presenting the pilot chute to the air in these different situations.

This is definitely something i need to brush up on and i'm sure i'm not alone.


If you're happy to share, i'd be delighted to listen.

ian

[maretus 0]

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"If it was 300 feet to impact, he could have used a 42" PC and taken a 1.5 to 2 second delay and been just fine."

Dude, speaking of all this, I did a jump from our 300' B, it has that "alternate" landing to the right of the corner we jumped. That makes it 240' to landing, I took a 1/2 second or so off the corner, had a 50 degree right and landed on the 240' landing. It was reasonable, too, I didn't even bat an eye. I was really surprised that on a half second hand held jump with a 42" PC, I was fine at 240' (inadvertantly, but it sure answered a lot of questions I had on accident).

Just out of curiosity, if you are going for a jump with 300" to impact, why go with 42" PC when planning to delay max. 2 secs ? Especially I'm interested why you chose a 42" PC on a 1/2 sec delay ? Wouldn't it be more appropriate to use a 46" ? Since all major manufacturers recommend a 45-48" when delaying under 2 seconds and the way I feel it in PC's (as in probably everything in BASE) you should always err on the bigger size. I'm very interested in this 'cause I've done a ~300" A several times with delays of 1-2 secs and my choice has always been 46" (hand held).

http://www.ufufreefly.com

[Faber 0]

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the way I feel it in PC's (as in probably everything in BASE) you should always err on the bigger size.

too big pc can cause centercell stripping if you overdelay that PC.

a 46´wont harm you on a 1-2 sec delay,but neither will a 42´off 300ft.
I before saw people freefall aprox 1 sec delay off 230ft whith a vented 42´ on a unvented canopy,serval times whith out any problems...

NOTE: isure recomend a 45 or bigger sub 250 ft for sure...

Stay safe
Stefan Faber

[NickDG 23]

Rich,

To help you understand, let's go back to the beginning . . .

There were many skydiving and BASE gear manufacturers (and still are) who build pilot chutes improperly. When all pilot chutes were made from F-111 these design problems didn't matter much, but when Zero-P material came into use the problems of bad pilot chute design became apparent.

Picture in your mind a very early round parachute with no modifications (no apex or steering vents). The problem with these parachutes is they would oscillate. The reason for this is the great amount of air trapped inside the parachute had no where to go, so it would spill out from under the skirt. This caused the canopy to tip one way and then the other, hence the oscillations.

On a smaller scale the same thing happens to pilot chutes. The F-111 material in the top of the PC negated this effect somewhat because air can actually pass through this fabric and this has a stabilizing effect. The problem began when Zero-P replaced F-111. We then began to see wildly oscillating pilot chutes. (Check out the Radix video page for Bridge Day 2004, in one of the teaser videos you can see a good example of this, and the effect it has on the canopy).

The underlying problem is really not the Zero-P material itself, it's the way the PC is manufactured. If the trim of the pilot chute is incorrect when manufactured then when inflated the upper surface forms a perfect circle. This will cause the oscillations. A better design will make an inflated pilot chute looked lobed (the trim tapes break up this circle and forms channels down the side of the PC.) These channels allow air to pass by the pilot chute and at the same time stabilize it. There's much more to pilot chute trim, but in simple form that's it.

I'm not convinced, at this point, that vented pilot chutes aren't just a quick fix for badly designed pilot chutes.

NickD BASE 194

[TomAiello 26]

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...The underlying problem is really not the Zero-P material itself, it's the way the PC is manufactured.

In my experience, the problem, 9 times out of 10, isn't the PC manufacture. Almost everyone is getting their PC's from a handful of (generally good quality) manufacturers. There are still some "garage specials" floating around, but fewer and fewer all the time.

What I've seen, more often than not, as the cause of orbiting or oscillation is asymmetric attachment, not manufacture. Even a perfectly made PC can oscillate if you attach it assymetrically, and most of the modern designs allow assymetric attachment (I have some Paratech PC's that will not, and Marty made me some custom that won't either--I heard a rumor that this is standard for Asylum now, but I'm not certain).

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I'm not convinced, at this point, that vented pilot chutes aren't just a quick fix for badly designed pilot chutes.

I'm actually fairly convinced that they are a fix for poor attachment. So most of the gains from this gear advancement have gone to allowing us (jumpers) to get away with sloppiness.


Back to the original question: I think that if you learn to attach the PC symmetrically, it's not going to be much of an issue, the vast majority of the time. If you attach the PC wrong, then the vents aren't going to save you (they'll help, though). If you have a properly constructed (most PC's) and symmetrically attached (unfortunately, not most jumpers), PC, then you may see some improvement from vents, but the improvement will be at the margin, and not noticeable on the majority of your jumps.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[TomAiello 26]

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What is bias?

BASE311 was kind enough to give me this diagram of block and bias.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[maretus 0]

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the way I feel it in PC's (as in probably everything in BASE) you should always err on the bigger size.

too big pc can cause centercell stripping if you overdelay that PC.

a 46´wont harm you on a 1-2 sec delay,but neither will a 42´off 300ft.

Sure thing that overdelaying with too big PC is not recommended but neither is underdelaying with too small PC. Of course you can get away just fine with 42" PC on a 300 footer with 1-2 sec delay but my main question was kinda why choose a 42" instead of 46" if you are planning a delay that is inside 46" PC's recommendations ? Do you see any considerable pros in using the smaller PC ?

This is starting to slide offtopic, feel free Tom to edit this or start new thread.

http://www.ufufreefly.com

[Faber 0]

did you read Dexters comment?
http://www.dropzone.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=1406670;page=2;sb=post_latest_reply;so=ASC;mh=25;
it kind of sums it up.

a 42 will inflate faster than a 46,and pop the pins.
It still need to pull out the canopy through..

Stay safe
Stefan Faber

[DexterBase 1]

I prefer the 42 on anything over 300 feet because it's a lighter PC. When you throw a pilot chute out to the side, the added inertia of a heavier PC will take more time and airspeed to overcome and inflate.

I prefer the 42 for anything over 300 feet but once I'm under 300 feet, I use the 46" PC in a handheld configuration. Remember, my personal hard deck for going stowed is 300 feet. I've gone stowed plenty of times just over 300 feet with a 42 and I'm very comfortable with it. Step under 300 feet though and the 46 goes on and the PC goes into my hand.

There's nothing wrong with using a 46 for this same 300+ foot jump, I just don't think you'll gain anything over the 42 at this airspeed. Go out to a friendly object and do a bunch of go and throws with a 46, then do a bunch with a 42. Decide for yourself.

Remember, all of my opinions are exactly that, opinions. I do what I feel comfortable with. I'm offering this information because we're discussing this topic. In no way do I recommend you take your 42" PC and go stowed from 300 feet. There are many things that need to be done after the canopy opens and just physically getting the parachute open over your head is just the start of the dangers of a BASE jump. I feel comfortable that the height my canopy will be open above the ground after taking a one second delay (stowed) from 300 feet will give me the time I need to land the parachute with some degree of safety. Based on your individual experience, opening 300 feet above the ground may give you the same degree of confidence. Others are more comfortable exiting and opening much lower than I am. To each his own in this sport. Remember, no information on this forum is going to keep you alive unless you have the experience to make it work, and have the patience to gradually up the ante.

[maretus 0]

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I prefer the 42 for anything over 300 feet but once I'm under 300 feet, I use the 46" PC in a handheld configuration. Remember, my personal hard deck for going stowed is 300 feet. I've gone stowed plenty of times just over 300 feet with a 42 and I'm very comfortable with it. Step under 300 feet though and the 46 goes on and the PC goes into my hand.

That's pretty much the way I've thought about it too.

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Remember, all of my opinions are exactly that, opinions. I do what I feel comfortable with. I'm offering this information because we're discussing this topic. ... To each his own in this sport. Remember, no information on this forum is going to keep you alive unless you have the experience to make it work, and have the patience to gradually up the ante.

That is an important point and point indeed worth of making. Still I'm glad that this discussion took place cause I mainly got the opinions I looked for. I've always thought about PC decisions on delays near 2 secs and on objects round the 300 ft mark.

http://www.ufufreefly.com

[NickDG 23]

>>What I've seen, more often than not, as the cause of orbiting or oscillation is asymmetric attachment<<

And that too . . .

Thanks Tom.

NickD BASE 194

[TomAiello 26]

I actually know people who prefer smaller PC's at lower altitudes. The general feeling is that a smaller PC inflates more quickly, so that in the end it cancels out the greater extraction force of the larger PC.

In my experience, the real killer at low altitude is not slow inflation. It is PC hesitation. Larger PC's are marginally more prone to weird hesitations. Stowing big PC's, in my opinion, greatly increases the risk of hesitation.

So, I think DexterBASE is on the right track here. Downsizing the PC when you stow is definitely a good idea. Keeping the big PC's in your hand helps reduce the chance of a hesitation.

There's definitely something to the "smaller = less hesitation" school of thought. I know people who take this as far as using 42's on 200' freefalls. I'm not quite all aboard for that, but I can definitely see the logic.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[DexterBase 1]

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I know people who take this as far as using 42's on 200' freefalls

I think in ten years, a 46" Pilot chute will be considered the "Big One." The trend seems to show that more jumpers are using pilot chute sizes that were considered (just a few years ago) inappropriate for short delays.

Who knows?

[BASE813 0]

one thing that seems not to be mentioned (i dont think by looking over the thread) is the canopy size. It maybe ok to take a 42 for certain freefalls with a 240 canopy but this does not mean that someone with a 280 should be doing it.

[Faber 0]

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I know people who take this as far as using 42's on 200' freefalls

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I think in ten years, a 46" Pilot chute will be considered the "Big One." The trend seems to show that more jumpers are using pilot chute sizes that were considered (just a few years ago) inappropriate for short delays.

a jumper borrowed my vented 42´attached it to his unvented canopy,fitting in a velcro rig.
we went to 230ftwere he made 1 sec delay on this each time.i made aprox 1,5 sec delay on my 46´vented in a pin rig containing my vented canopy. we ended up under flying canopy arround same hight(70-100ft)each time,both of us.

I know that the Basedudes(Belgium)use an unvented 46(or45) as their biggest pc.

Personaly i have serval ff off 180ft whith my vented 46 pc,that i choose to use a 48 from that alti after my last jump is another thing..

You might want to ask Tom on PM who made the lowest ff whith a 42 on i think it were one from CR jumping off 180 or so,quiet insane but it were done...

From your posts i see i think alot like you in gear.(after a pc hessi on a 180ft ff) i usaly also use a 46 below 300ft now,if i rember.but am ok if needed to jump off 250ft whith my 42´.

I know that Tom has been thinking alot about this as we were asked not to speak up about this as we dont really want to undersize pc´s for jumps,but its interesting.

A jumper once made a pc drag tabel(i cant find it any more which teoretic showed how much pull force a given pc would have at a given time(weight and wing load considdered

its werry interesting stuff

Any way
did you make any of thouse carry on SL´s? i might want to ask you to build some for me.if you havnt i can tell you how to do.
My local beforeBASEfreindly has become unBASEfreindly.
i need some in different lenghts,and the one i have is pretty mush worn out(not that i do alot of them SL jumps he he,i just love it..)

Happy safe new year mate..
besides i think i found a place that sells tickets to that tampac(tampax?)place you want me to go

edit: by request of poster

Stay safe
Stefan Faber

[DexterBase 1]

I've got all the stuff to build the SL setups. Just send me a PM with the lengths you want and I'll throw a few together for you. I've been using them a lot and they work great. I'm building them out of 900 pound dacron.

Tampax??? Seatac!!!!! Crazy Dane...

[DexterBase 1]

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one thing that seems not to be mentioned (i dont think by looking over the thread) is the canopy size. It maybe ok to take a 42 for certain freefalls with a 240 canopy but this does not mean that someone with a 280 should be doing it.

Nice, I was wondering when someone was going to point this out. I'm just getting off work but hopefully I'll be able to post more on this topic later.