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bsrodeo540

Nova pack?

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I’m experimenting with packing techniques to slow down the openings. I got Safire-1 139 ft and it might be one of the older ones that are known for harder openings (not as bad as Sabres though). I psycho pack and the list of things to try currently include:

1) Better control of the slider during packing (making sure it stays in place and not moving away from the slider stops)

2) Double stowing all the lines even for the closing loops and keeping them tight and symmetric

3) Rolling the cells tighter to the inside without exposing the center cell.

One of the “techniques” I came across a couple of times already on this forum is so-called “Nova pack”. Basically it only implies that you roll the four cells on each side inside and tuck each roll into a respective half of the center cell. Can anyone that has experience with this share his/her thoughts/observations/rationale? When I first read this my first reaction was – WTF.. But like I said, I noticed this advice more than once already and interested in your experience. The way I see it, technically the canopy was not designed for this kind of thing and logically (one would think) once these cells start taking air in and expand still being inside the center cell, it would exert excessive pressure on the inside walls of the center cell which it wasn’t really designed for? Can that potentially damage your canopy, let alone provide inconsistent openings?

I understand a lot of people have their opinions on this matter but particularly interested to hear from whoever tried this method or at least considered it and decided for/against for whatever reasons.

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A long time ago, Performance Designs told us to quit shoving the other cells into the centre-cell.
I used to shove stuff, but concluded that slider placement is more important. The most important part of slider placement is sliding it all the way up the lines so that it firmly rests on the stabilizers/slider stops.

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Some additional things to consider:

1. Slider placement. You are careful to set it against the slider stops and quarter it nice and symmetrical. However, it is important to place your finger on the center of the slider and push it as far down into the canopy fabric as it will go as the last step. This gives the fabric more to hold onto and ensures your slider stays put throughout your pack job. It seems simple, but I have noticed some jumpers quartering their sliders so much, that the center of the slider is pulled up out of the fabric. Upon opening, air is able to get up over the top of the slider and gets a head start on pushing it down which lessens its effectiveness at doing it job.

2. Line trim. As Dragon2 said, be I out of trim can affect your openings. Another aspect to this is the brake setting. Check your steering lines and if they are straight, or if they have been twisted over time to the point that the line may have lost some length. If they are set too deep (or shallow) they will have a very noticeable impact on your openings.

3. Pilot chute size and condition. The PC should be approximately 3% of the size of your canopy. For a 139, your PC should be 4.17 square feet which, if my math is accurate, would put you in the range of a 27 in diameter PC. (edit 27 in would be ideal with ZP, however, 28 in is commonplace on anything below 150-ish square feet). Also the overall condition of your PC and the length of the bridle should be checked.

Beyond what you are already doing, and the items I mentioned, some basic things to consider would be closing loop length. If you psycho pack, you are getting a nice tight pack job, so make sure your closing loop isn't too loose, and body position. Take a couple seconds to slow yourself down as much as you possible can before you deploy. I know that is basic, but sometimes we develop habits.

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Dragon2, it's Spanish but I heard only some of their Safires are like that, not all.

RopeaDope, very solid advice, you basically summarized all the important points I picked up from packing videos and seminars, thank you!

Riggerrob, you made an inspection on that canopy 3 jumps/6 months ago, how is my trim? ;) Btw, it's the one in the rig right now, feel free to pop it and take a look, I won't need it at least till Friday.
Every life comes with a death sentence. Until then, who's in charge?

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peek

***... The PC should be approximately 3% of the size of your canopy.



Where did you get that information?

Hey Gary, one of the current FAA riggers written test questions is the best pilot chute size ratio to the main canopy and 3% is the answer listed. Just went through that and remember seeing it for what it's worth.

You planning on coming down south and jumping with us anytime soon?
Keith
"You don't get many warnings in this sport before you get damaged"

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BKS60

best pilot chute size ratio to the main canopy and 3%



Let's see...

My main is 260 sq. ft. (yeah, I'm a big boy)
So 260 * .03 = 7.8 sq. ft. pilot chute.

Find the diameter of a 7.8 sq. ft. round:
Area = pi * r²
A / pi = r²
7.8 / 3.14 = 2.5
r² = 2.5 ft
r = 1.6 ft radius
diameter = 2r
d = 3.2 feet

A pilot chute that is 3 feet in diameter! Holy crap. Mine is probably half that. But it works just fine...

Have I done my math wrong, or is there something wrong with this ratio?

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FugginNut

***best pilot chute size ratio to the main canopy and 3%



Let's see...

My main is 260 sq. ft. (yeah, I'm a big boy)
So 260 * .03 = 7.8 sq. ft. pilot chute.

Find the diameter of a 7.8 sq. ft. round:
Area = pi * r²
A / pi = r²
7.8 / 3.14 = 2.5
r² = 2.5 ft
r = 1.6 ft radius
diameter = 2r
d = 3.2 feet

A pilot chute that is 3 feet in diameter! Holy crap. Mine is probably half that. But it works just fine...

Have I done my math wrong, or is there something wrong with this ratio?

Measure your PC. 3.2 feet is 37-ish inches. I'd be willing to bet you have a 38 in PC

*my math comes out to 37.8 inches for a 3% ratio on a 260

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RopeaDope


Poynter manual vol 2, pg 245.



Interesting, although it is also in vol 1, which while printed in 1991 was last revised in 1984 it says in the cover. (Page 338 in 1991 printing)

So the data is at least 32 years old.
And who knows, maybe even older and for rounds.

Good job FAA! "Probably nothing new in skydiving since then."

(And I did the calcs, for a Velo 89 you want a 22" diameter PC according to the FAA. And a bit under 26" for a 120 canopy)

I have seen newer info in the last decade from various skydiving manufacturers on their recommendations for pilot chute sizes.

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Yes, and that data would have been compiled using F 111, whereas now ZP is becoming more common. I haven't looked at all the manufacturers, but since I have a Javelin, I looking at Sun Paths canopy sizing chart. It also shows the PC size for each container size and hey don't stray very far from the 3% ratio

*I would suppose that by now, 3% is a starting point that each manufacturer tweaks as they test their containers and various canopy styles to come up with the best all-arounder for the results they desire.

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RopeaDope

******... The PC should be approximately 3% of the size of your canopy.



Where did you get that information?

Poynter manual vol 2, pg 245.

And yes, it's currently in the question bank for the written test.

3% is for round canopies.

The original 1971 Poynter's has slight different numbers than the current 1991 edition. The 1971 numbers are:

. . up to 200 knots 3%
. . 200-300 knots 2%
. . over 300 knots 1%

-Mark

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I have a 210 main and a 33in PC. The math on mine puts 3% at 32.96, so it works out on my rig.

*not that I'm trying to argue the point. Just that for anyone planing to take the test, 3% is the answer.

I reference the Poynter manuals, new rigger handbook, FARs, and ACs, and then the manufacturer has final say for anything in question

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Well, folks, I'm glad I asked that question and I'm glad I was a bit skeptical. What is the "correct sizing" of a pilot chute supposed to insure?

1. That the parachute doesn't open too quick?
2. That the parachute opens quickly enough?
3. ?

Aren't there more important questions to put on a rigger's test?
(A lot more important?)

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To summarize:
The pilot chute size thing was just one point you were making about canopy packing methods in general, way back in post #4. A fair enough concept, that sometimes gets talked about. (E.g., Bill Booth has sometimes written about pilot chute sizes and how much it should decelerate relative to the jumper, when pulling the bag out.).

While that particular 3% number looked quite reasonable to you due to the FAA relying on it in testing material, others of us then dug a little deeper, to show that the FAA's use of the number is a little shaky and not up to date.

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"Basically it only implies that you roll the four cells on each side inside and tuck each roll into a respective half of the center cell."

Check your manual, contact manufacturer and your rigger.

FWIW: Did that with my F-111 PD-230 back in the 90's. Worked great: opened soft and reliable every time.

Moved on to a ZeroP Sabre (1)-210. Cautioned by PD and my rigger to NOT place rolled cells into center cell. Followed their advice. Occasional hard openings despite following PD's instructions (including John LeBlanc's article on avoiding hard openings) on packing, slider position, body position, slowing down before deployment, etc. Finally had my rigger install a pocket on my slider last year = not a hard opening to date. I now have to plan for openings that run 600-800'.

Don't know if that would be applicable to your situation. Trust your professionals. Good luck.

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RopeaDope

Slider placement. You are careful to set it against the slider stops and quarter it nice and symmetrical. However, it is important to place your finger on the center of the slider and push it as far down into the canopy fabric as it will go as the last step. This gives the fabric more to hold onto and ensures your slider stays put throughout your pack job. It seems simple, but I have noticed some jumpers quartering their sliders so much, that the center of the slider is pulled up out of the fabric. Upon opening, air is able to get up over the top of the slider and gets a head start on pushing it down which lessens its effectiveness at doing it job.



Guys, will repeat my post in this thread to give credit to a good piece of advice that solved the issue in my case:

Discovered this thread and decided to post my results in case someone is facing the same issue in the future. Basically, from my findings, good slider control during packing solved the issue for me.

First, I make sure slider grommets are always tight against the slider stops and never slide back down the lines when I put my canopy on the ground. Second, quartering the slider: I used to put too much emphasis on the "quartering" part, meaning ensuring that each quarter of the slider is tucked neatly between the lines and inside the stabilizers. I found that actually creates an issue so that when I do that - my slider center that I have just tucked deep into the center of the canopy between the line groups, slides back up a little.

Now I make sure I tuck it in really well and spread the corners that stick out neatly without tension, so that the slider itself stays deep where it needs to be. Also, once on the ground (again, I psycho-pack), I grab the center of the slider and pull it up once again before folding the triangle. Also, when actually folding the triangle, I put my knee just over where the slider grommets are and make sure whatever I do after does not cause the slider fabric inside my packjob to slide down.

That, on top of rolling my cells toward the center a bit tighter and leaving the center cell out, along with always double-stowing ALL my lines (I used to do it only on the first two stows) ensured consistent nice and pleasant (but not too long) snivels.
Every life comes with a death sentence. Until then, who's in charge?

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