PC for Mirage/Cobalt Combo?

[Jimbo 0]

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though mine opens and flies great.

Yeah, it does now, but by your own admission it didn't open so great when you were using the slider that Atair delivered with the canopy. The slider that they intend for everyone else to use.

I put about 30 jumps on a Cobalt a few years ago, loved the way that canopy flew, hated the way it opened.

-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[imdskydiver 0]

I've just had one hard opening under my Cobalt in 500 jumps , I tried packing different ways and always get the same soft opening , I love mine .

[3ringheathen 0]

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My one and only bag lock was on a tandem that someone had double wrapped the rubber bands on.

What kind of rubber bands were you using?!
I can't imagine that it's possible for the standard skydiving rubber bands, i.e.: the light brown ones, to withstand the pull force that a tandem drogue produces.
My money is on some other cause: drogue not cocked completely, line half hitched around a stow, etc.
-Josh

If you have time to panic, you have time to do something more productive. -Me*
*Ron has accused me of plagiarizing this quote. He attributes it to Douglas Adams.

[3ringheathen 0]

That's surprising, but then I wasn't actually recomending a 20" pilot chute, I recomend a 24" preferably F-111, and replacing it sooner than you would a ZP.

Remember, diameter is linear, but surface area is not. A 24" pc has roughly 44% more surface area than a 20" pc, if I did my math correctly. (I'm rusty)

I haven't been able to find any hard numbers on the actuall amount of drag produced, but it stands to reason that it would be significantly more.

Along the same lines, a 28" pc has about 36% more surface area than a 24" does.

If you've got a larger and therefore heavier canopy, you'll need a larger pilot chute to extract it reliably.

I suspect that average pilot chute size from the rig manufacturers is going to start decreasing in response to the trend towards smaller canopies.

It's well documented that oversized pilot chutes can cause hard openings.
The trick is figuring out what is oversized for a particular set up.
-Josh

If you have time to panic, you have time to do something more productive. -Me*
*Ron has accused me of plagiarizing this quote. He attributes it to Douglas Adams.

[Hooknswoop 19]

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What kind of rubber bands were you using?!

Standard large type rubber bands. Not even the larger tandem bands.

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I can't imagine that it's possible for the standard skydiving rubber bands, i.e.: the light brown ones, to withstand the pull force that a tandem drogue produces.

After recovering the bag, I pulled as hard as I could with my foot on the bridle and the lines wouldn't release and they were not wrapped around each other in any way.

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My money is on some other cause: drogue not cocked completely, line half hitched around a stow, etc.

No, the cause was the double-wrapped rubber bands. Also, when the drogue release ripcord is pulled on the Vector II tandem (the system I had the bag lock on) the drogue partially collapses (and other tandem systems).

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If you've got a larger and therefore heavier canopy, you'll need a larger pilot chute to extract it reliably.

I didn’t have a larger canopy (60 square feet). Once I would reach back and pull the pin, I would have a normal opening. With the PC at the edge of the top of burble and today’s better main pin protection, it can easily take more force to open the container than it does to deploy the main canopy.

I use a 24-inch ZP PC for both my 60 and my Safire 189 with good, consistent results on both.

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I suspect that average pilot chute size from the rig manufacturers is going to start decreasing in response to the trend towards smaller canopies.

I hope not, as that would cause more PC’s in tow.

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It's well documented that oversized pilot chutes can cause hard openings.

I haven’t read that documented anywhere, can you point me towards that information?

Derek

[3ringheathen 0]

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Ok, "smaller PC" according to all of those around me and in the industry (except for Atair), the smaller PC would result in PC hesitation (in the least, PC in tow at the worst).

You haven't talked to enough people in the industry.
I'm going to start another thread with some links to relevant industry leader websites so that people can do their own research and decide for themselves.

It's true that too small of a PC will result in the problems you mention, but it's also true that too large a PC will result in hard openings, and not just on Cobalts.
It's pretty common that as performance increases, so does the amount of finickyness, attention to detail, and/or customized accessories.
A good analogy is sports cars: they tend to need high octane gas, speed rated tires, stiffer suspensions and so on.
With rigs, it's more secure risers covers and flaps.
With canopies it's trending towards a narrower range of pilot chutes for a given canopy, more frequent line replacement, specialized risers and more carefully maintained cutaway systems.

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The "tighter" line stows that was recommended (double stowing small rubber bands) would quite possibly resulted in a bag lock.

Maybe. As I said, too small and too large can be problematic. I tend to single stow the last couple of bites of line, and double all the others.
It's worth mentioning that John Sherman once said something to the effect of "There's a reason the military spent a bunch of money researching parachute bands. They are supposed to break fairly easily."
This is why those new black rubber bands, bungy cord, and to a lesser degree, tube stows aren't such a good idea.

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There's a problem when every other canopy on the market of the same type opens perfectly with the PC that the container manufacture recommends and with small rubber bands single stowed, but this canopy has to have these two things different (dangerous) to fix its openings.

I already acknowledged that there are problems with some of them. That's not in dispute.
It's also true ATAIR isn't at all unique for having these problems.
However, it's *not* true that all other canopies work great with factory PCs and single wraps on the line stows. On average, it's less of a problem for some of the others, but a problem nonetheless.

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I can't tell you the number of times that I've seen a Sabre2 open so soft that it has collapsed endcells. I guess that'd be called a "2 stage opening" as well.

No, that's a snivel. Similar, but not the same.

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I don't remember any of them recommending to change a piece of equipment that is out of the realm and into the container manufacture's realm, though. Eitherway, the Cobalt has been produced for a good number of years (since the Space), seems like the opening problems would have been fixed instead of "bandaged" by now.

The barrier you call the realm of one type of manufacturer Vs another is somewhat arbitrary.
Again we'll use the car analogy. Ford has specific parameters for tire size and inflation for it's vehicles. Yet know one freeks out when an aftermarket tire company throws larger or smaller tires on the vehicle, changes the rims, etcetera.

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you have to turn pretty low to get a fun landing out of a Heatwave

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Eh, not really. I have to turn lower on the Stiletto I'm jumping now of the same size to get as good of a swoop. With the Heatwave I was jumping, I'd toss out a 270 at about 450ft. That's not too much lower then with the Xfire2 I was jumping or the Cobalt I demoed a while back. Only about 100ft, max.

Whether or not the Stiletto or the Heatwave is better based upon our personal experiences is kind of silly to argue about.
My Stiletto 120 was markedly better than the Heatwave 120 I borrowed for a while, and come to think of it, it opened a lot softer, too.
Canopies of the same make and size have widely varying flight characteristics. It's the nature of a fabric wing. I don't doubt your experience was different, I just take exception to the implication that I'm wrong to have had a different experience.

As for your 450' figure, unless you were jumping specialized testing equipment, you can't possibly have figured out your altitude with that sort of precision. Neither eyeballs, nor altimeters give anything more than rough approximations.
Thus you are left with a highly subjective estimate.
-Josh

If you have time to panic, you have time to do something more productive. -Me*
*Ron has accused me of plagiarizing this quote. He attributes it to Douglas Adams.

[Ron 10]

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Cobalt is a more or less HP canopy. Same like at all HP canopies, you sacrifice freedom of doing as you like for joy and speed. Small HP canopies don't forgive as much as the bigger square one do. and you have to play by the rules to survive when flying/opening HP canopies. if you don't like the rules, get a 7 cell loaded 1.0 :1 at most. with that you can virtually open on your back and it will open nicely, probably a little harder, but you'll survive.

I have jumped a Stiletto 107, Vengence 107, Velocity 96,90, Specter 107, Crossfire 105?, Jedei 93?, 105? Extreme 88 and 69, and a Cobalt 105 all with the same rig,bag and pilot chute set up...

Only the Extreme 88, and the Cobalt opened like shit....The Extreme BTW was a test canopy back in 96, so I kinda expected it to open like shit...The Cobalt was a Demo.

Why did all the other canopies (almost all considered to be high performance) open great with the same set up, but only the test canopy and the demo Cobalt opened hard?

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Anyway you can start accusing cobalt and the usual, i said what i had in mind. Go on and make cobalt look a bad canopy with bad openings, like the conversation about cobalt usually ends, though mine opens and flies great

No, it FLEW great, but opened like shit. And if most conversations about Cobalts go in one direction...Maybe there is a reason? Where there is smoke, there is fire.

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p.s.: You have to earn the love of cobalt

I never had to earn the love of any other piece of skydiving equipment....Im not about to start now.

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[rigging65 0]

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I had a 28" PC on my Cobalt 95, in an Infinity container. My openings were hit and miss, with the not infrequent slammer.
I switched to a 24" F111 PC, and the openings have been *far* more consistent and two staged. The difference is unmistakable.

I'm assuming you did this on the same canopy, right? If that's the case, there are other things that could have caused the change besides just the P/C. Changes in trim come immediately to mind. As well as one or two others...

"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

[TALONSKY 0]

The most ironic thing (in my opinion) about the Cobalt is the canopy was supposedly designed to open at high freefly speeds in case of a premature deployment freeflying or incase a freeflyer did not decelerate before deploying and some of them open fairly hard and need some bandaged style of fix’s to make them not open hard.
Kirk

[3ringheathen 0]

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I had a 28" PC on my Cobalt 95, in an Infinity container. My openings were hit and miss, with the not infrequent slammer.
I switched to a 24" F111 PC, and the openings have been *far* more consistent and two staged. The difference is unmistakable.

I'm assuming you did this on the same canopy, right? If that's the case, there are other things that could have caused the change besides just the P/C. Changes in trim come immediately to mind. As well as one or two others...

Yes, the same canopy.
The only variable was the pilot chute, therefore it's unlikely that the improvement was due to anything other than the smaller pilot chute.
This is why the scientific method is so valuable.
If it were line trim, it would have been a gradual change. It was not.

What are your other hypothetical causes?
-Josh

If you have time to panic, you have time to do something more productive. -Me*
*Ron has accused me of plagiarizing this quote. He attributes it to Douglas Adams.

[JYorkster 0]

Talked to Dan today and he does not believe it is a PC problem. Also, he did not give me a list of things to try to fix the openings. He was very receptive to the information I had and wants me to send it to them to test jump. I feel confident that if there is a flaw, they will take care of it.

As to the original question of the thread about which PC to use:

After videoing the opening sequence, I feel confident that a 24" ZP PC has enough snag force for the Mirage G4 and a 120 Cobalt. Thanks for all the responses.

Rock

[AggieDave 6]

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Also, he did not give me a list of things to try to fix the openings. He was very receptive to the information

I'm very happy for you then, my experience with Dan was the exact opposite, thus he lost a canopy sell and I tell people about my very bad experience all the time.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[rigging65 0]

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Yes, the same canopy.
The only variable was the pilot chute, therefore it's unlikely that the improvement was due to anything other than the smaller pilot chute.
This is why the scientific method is so valuable.
If it were line trim, it would have been a gradual change. It was not.

Well, if you did enough jumps on the canopy to really be scientific about your testing, than by the time you changed to another p/c there certainly would have been some trim change. And, if you had done the same amount of jumps on the new p/c (again, to be scientific) there would have been even more trim change. Sounds to me that it's pretty tough to pin the problem on any one specific item, no?

As for the "other" possible problems...canopies are dynamic animals. You can never pack it exactly the same twice in a row. The slider could have been slightly different, the nose placement...who knows. You often hear of people going through "bad cycles" in their packing. They get a week or two worth of bad openings and then it suddenly goes away. Who knows what causes these changes?

If you changed the p/c on your rig and you don't have any more problems, good for you. But I'd be hesitant to say that nothing else changed or that it must have been the pilot chute. Parachutes are systems made up of single items that all work with each other to produce a result, not individual items doing their jobs independent of one another. I'm glad your openings are better!!

"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

[3ringheathen 0]

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Yes, the same canopy.
The only variable was the pilot chute, therefore it's unlikely that the improvement was due to anything other than the smaller pilot chute.
This is why the scientific method is so valuable.
If it were line trim, it would have been a gradual change. It was not.

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Well, if you did enough jumps on the canopy to really be scientific about your testing, than by the time you changed to another p/c there certainly would have been some trim change. And, if you had done the same amount of jumps on the new p/c (again, to be scientific) there would have been even more trim change. Sounds to me that it's pretty tough to pin the problem on any one specific item, no?

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It's not at all difficult to assess what is by far the most likely cause.
Your logic is flawed:
1) Line trim changes are very gradual. That is, you don't jump a canopy 200 times and all of the sudden the outside lines shrink by two inches. It's a teeny bit of shrinkage on every jump, perhaps 1/100 of an inch. If you graph the change you get a nice, straight diagonal line.

In my case, I had decent, but harder than expected openings. I changed the pilot chute. I had exceptionally nice openings. Not at all a linear change. Therefore, not line trim. It's quite simple.

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As for the "other" possible problems...canopies are dynamic animals. You can never pack it exactly the same twice in a row. The slider could have been slightly different, the nose placement...who knows. You often hear of people going through "bad cycles" in their packing. They get a week or two worth of bad openings and then it suddenly goes away. Who knows what causes these changes?

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2) Again, the beauty of the scientific method:
It's true that other variables may come into play, but they are random. Some will improve openings, others will harm them. On average, they tend to neutralize each other.
IIRC from my stats class, the magic number for a sample size that reliably washes out the random variables is about 30.
Thus, it's entirely reasonable to attribute the change in my openings to the pilot chute.

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Parachutes are systems made up of single items that all work with each other to produce a result, not individual items doing their jobs independent of one another.

This I agree with. It's what I've been saying since someone made the blatantly false assertion that pilot chute size does not affect parachute openings.
-Josh

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[psw097 0]

I've tracked the line trim change of my 2 Vipers (same airfoil, line trim and planform as the Cobalt) - My 94 opened very hard regardless of packing, PC, container used, etc. My 105 Viper was similar, but not as severe. I tracked line trim changes as the openings improved. My observations were that the lines shrank into trim, not out of trim. - the brake lines and C-1 line appeared to make the biggest difference. I do not have my spreadsheets with me for the exact numbers but the brake lines on my 105 are something like 8 inches short.

My 94 Viper has ~200 jumps on it now and opens very nice. My 105 has around 550 and opens like butter. The 105 is now starting to have the feel of going back out of trim - near stall on openings, slight tendancy to line trist, very abrupt stall point.

Overall I think the Atair canopy is sensitive to line trim and manufactured "long" to lengthen the life of the line set and lessen the chance of an opening-stall/line-twist/chop problem. Hard openings are better than constant chops for spinning line twist? Throw in copy variation and some open hard and some open great. This is theory of course and I would have thought that Atair would use Vectran line sets if the theory was true.

After 700 or so jumps on Vipers and demo Cobalts I love the canopy but they are interesting to tame. But, I also paid 500 for one and 600 for the other - brand new. For that price I'm willing to ride out a couple wild openings. For 1400, I'd buy something more consistant.

[rigging65 0]

Hey, like I said, if you're having softer openings, great for you! Maybe it's just the canopy you're jumping. I've jumped Stilettos, Crossfires and Xaos canopies over the last few years and have regularly changed pilot chute sizes, bridle lengths, whatever: It's never made a difference. The only noticeable change was the time to took to get the canopy out of the container, which was almost completely due to bridle length. Glad your openings are better...but I'd get a canopy that you don't have to force to make open nice if I had the problems you did. Just my $.02 and three years of test jumps worth...

"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

[3ringheathen 0]

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I'd get a canopy that you don't have to force to make open nice if I had the problems you did...

You must be confusing me with someone else. I never had any significant problems. I simply found the openings to be much better with the smaller slider. They were never bad to begin with.
-Josh

If you have time to panic, you have time to do something more productive. -Me*
*Ron has accused me of plagiarizing this quote. He attributes it to Douglas Adams.

[rigging65 0]

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smaller slider

???I thought we were talking about PCs here???

"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

[3ringheathen 0]

Oops. That was a typo. I meant a smaller *pilot chute*.
A smaller slider would, of course, make openings faster.
-Josh

If you have time to panic, you have time to do something more productive. -Me*
*Ron has accused me of plagiarizing this quote. He attributes it to Douglas Adams.

[Kris 0]

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A smaller slider would, of course, make openings faster.

Not necessarily. A smaller slider could also slow down the openings as it can reef the canopy more at the appropriate size.

Sky, Muff Bro, Rodriguez Bro, and
Bastion of Purity and Innocence!™

[rigging65 0]

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Not necessarily. A smaller slider could also slow down the openings as it can reef the canopy more at the appropriate size.

As was made evident on several VX canopies. A larger slider can radically increase the amount of bottom skin exposed to the wind before the slider starts to descend the lines, thus making for more "area" to catch air and cause a more rapid deceleration and a harder opening. Of course, there are other factors that play into it as well...

We had a customer that was simply getting punished by his VX. We asked for help after trying some of our own fixes, and Icarus sent us a new smaller slider. I made the mistake of informing the customer about what had transpired and he flat out refused to jump the canopy. I put a few jumps on it for him to prove it was ok, and he was dumbfounded. It's about geometry, surface area, and tension...but the most obvious "fix" isn't always right...or even in the right direction!

"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

[VectorBoy 0]

I've got two cobalts. A 120 and a 135. I've got two pilot chutes a custom 23" and a Cazar 28". I swap them back and forth with NO change in the openings personality.

How tightly I roll the tail when I pack and maintain this tight roll will have a great amount of influence on how I can get them to open. I can get them to open brisk but not slam or I can get them to snivel for so long that jumpers watching the video of these deployments would often comment that they would have already gone for silver long before now.