Do you get hard openings before a thunderstorm?

[soulbabel 0]

Two people I packed for complained of hard openings last weekend. I've packed for these people before and they say the openings are usually good when I pack for them. One jumps a Crossfire2 135 and the other a Pilot 150, so their canopies should be pretty forgiving even for a sloppy pack job. So I was surprised to hear how hard their openings were when I packed the canopies the same way I always do.

I didn't charge them, since I felt pretty bad, but I couldn't stop thinking about why they would get such hard openings when hot air is thinner and therefore should cause the canopy to open slower.

We jump out in Virginia, so the day was very hot(90 F), very humid, with an approaching thunderstorm about 2 or 3 hours out.

When I consider the following variables:
High temperature = thinner air (air molecules are more dispersed at higher temperatures)
High humidity = thinner air (because water molecules are lighter than Oxygen and Nitrogen gases)
Lower barometric pressure = thinner air (air molecules are less dense due to less atmospheric pressure)

it seems that the weather conditions would provide them with the nicest, softest openings ever because the air would be so thin. Yet my two pack jobs managed to defeat all of these awesome conditions and give two people hard openings. They were on different loads about 25 minutes apart.

So now I'm wondering if the approaching thunderstorm is the factor I really need to consider. Perhaps all that moisture traveling upwards into building the storms clouds is enough to cause the hard openings. I know that paragliders ride thermals to altitude, but is this the same thing? Has anyone noticed their openings were harder when a thunderstorm was approaching?

I'll appreciate any feedback, whether it be personal experiences or scientific explanations, etc. Because right now I'm thinking if I know a thunderstorm is coming, as they frequently do during Virginia summers, I'm going to pack every parachute like I packed my insta-whack Monarch 175 canopy (push the nose way in, and roll the crap outta the tail).

[JohnRich 4]

Only if opening facing in the direction of the oncoming storm.

[CHRCNF 0]

Only if it is both a leap year and high tide.

[DaVinciflies 0]

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When I consider the following variables:
High temperature = thinner air (air molecules are more dispersed at higher temperatures)
High humidity = thinner air (because water molecules are lighter than Oxygen and Nitrogen gases)
Lower barometric pressure = thinner air (air molecules are less dense due to less atmospheric pressure)

it seems that the weather conditions would provide them with the nicest, softest openings ever because the air would be so thin.

Just to play devils advocate, those same variables could contribute to a higher terminal velocity at pull altitude. Might that affect the openings?

(Not that I am suggesting that this is the answer, merely offering a counter-point to your assumptions).

If you want to get really speculatory, how about:

The electrostatic charge in the pre-storm atmosphere coated the canopy in electrons which all repelled each other when the canopy came out of the bag!??!

[PiLFy 3]

I'm replying more to remind me to watch this thread. It's an interesting question. As high humidity means more water in the air. Would not the air be harder to compress (more dense) under an opening chute? That's the only possibility that comes to mind.

[PiLFy 3]

Well, he did say he'd appreciate any feedback...

[soulbabel 0]

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Just to play devils advocate, those same variables could contribute to a higher terminal velocity at pull altitude. Might that affect the openings?

That was actually my first thought. I jumped that day too, so I downloaded the data from my Altitrack into Jumptrack and reviewed the speed graph. It didn't seem like a noticeable increase in speeds, though, so I started pondering other factors.

[stayhigh 2]

You should've still charged them, sounds like you are new to packing game.
You get paid to put shit in the bag and not how it comes out.
Only thing i won't charge for is step thru. Other than that you owe me six bucks.
And no im not gonna spend my time looking for your main, you should've chase that thing down.

Bernie Sanders for President 2016

[soulbabel 0]

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As high humidity means more water in the air. Would not the air be harder to compress (more dense) under an opening chute?

Can you rephrase that part? I wasn't really clear on the question.

In regards to the high humidity, I'm wondering if the moisture is enough to wet the surface of the ZP and therefore cause it to trap air more efficiently. That could make it a contributing factor to a hard opening.

[soulbabel 0]

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You should've still charged them, sounds like you are new to packing game.

The first guy was a camera guy, so he showed me his opening. His opening was so hard on his Xfire2, he had a brake fire and got spun into some crazy diving, line twists and nearly cut away. The second guy said he got pretty dazed on opening, and stopped jumping after that. He told me 3 of the 4 people who did a hop and pop also had hard openings, so he didn't blame me, but I still felt bad since it was the second hard opening in a row.

They offered to pay, but I turned them down. I make all my money from packing tandems, so I wasn't really worried about the money. My main concern is figuring out if I need to start factoring environmental factors when I pack. If conditions are normal, then I pack without doing anything special. If a thunderstorm is coming, I'll do what needs to be done for a softer opening, even though I know it'll probably be off heading.

[PiLFy 3]

In other words. Picture a column of air. The column is the vertical track the chute will follow while inflating. If it's very dry within the column? The chute won't have to compress a lot of water molecules in the air on the way down. If there's a high concentration of water molecules in that column of air? They will quickly begin to be compressed by the chute as it snivels/opens, creating more resistance.

[ShayneH 0]

Density altitude affects parachute openings. Try jumping a canopy at sea level vs a higher altitude on a hot day (ie colorado).

Here is what the SIM (sect 5-5) says about it:

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4. As density altitude increases, airspeed increases by:

a. almost five percent per 3,000 feet up to 12,000 feet MSL

b. more than five percent per 3,000 feet above 12,000 feet MSL

5. As density altitude increases, a ram-air canopy pilot can expect the following:

a. a higher stall speed

b. a faster forward speed

c. a faster descent rate

d. higher opening forces

I thought I had also read something by Brian Germain on the topic somewhere, but couldn't find it. However, I don't think that a thunderstorm could change your density altitude enough to alter openings that severely.

Oh, and there's no reason not to charge them for a simple hard opening.

[wolfriverjoe 1,523]

Were any other jumpers complaining of hard openings?
Either those packed by you or by someone else?

Or was it just those two packjobs that opened hard?

To be honest. it sounds like a funky coincedence to me, but I've been wrong about that sort of thing before.

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[airtwardo 7]

So now I'm wondering if the approaching thunderstorm is the factor I really need to consider.

[chuckakers 426]

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So now I'm wondering if the approaching thunderstorm is the factor I really need to consider. Perhaps all that moisture traveling upwards into building the storms clouds is enough to cause the hard openings.

Not a chance.

Chuck Akers
D-10855
Houston, TX

[PiLFy 3]

"The first guy was a camera guy, so he showed me his opening. His opening was so hard on his Xfire2, he had a brake fire and got spun into some crazy diving, line twists and nearly cut away. The second guy said he got pretty dazed on opening, and stopped jumping after that. He told me 3 of the 4 people who did a hop and pop also had hard openings,"

Den splain that to me, Lucy... Was not some phenomena @work to cause these hard openings?

[soulbabel 0]

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Were any other jumpers complaining of hard openings?
Either those packed by you or by someone else?

For the second jumper, he said 4 people did hop and pops on his load, and 3 of them had hard openings. His canopy was the only one I packed, and the other two were by someone else.

[JohnRich 4]

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In other words. Picture a column of air. The column is the vertical track the chute will follow while inflating. If it's very dry within the column? The chute won't have to compress a lot of water molecules in the air on the way down. If there's a high concentration of water molecules in that column of air? They will quickly begin to be compressed by the chute as it snivels/opens, creating more resistance.

If that were true, there would be an epidemic of hard-openings in high-humidity places like Florida and east Texas. But it ain't happening...

[soulbabel 0]

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As density altitude increases, a ram-air canopy pilot can expect the following:
d. higher opening forces

I read the SIM's explanation shortly after the hard openings, and I thought I had found my answer as to why they happened. But then I researched density altitude, and I realized that the conditions of that day all point towards a decrease in density altitude. The high humidity, high temperature and lower atmospheric pressure would mean lower opening forces. So I was like, "WTF, maybe I am a horrible packer."

Basically, I sum the SIM's explanation as "your parachute will open harder in the winter, than in the summer at your DZ."

[PiLFy 3]

Something caused those hard openings though, right? I think I've already made my ignorance in this area apparent. Like the OP, I too want to learn what happened.

[billvon 3,077]

High temps and humidity result in high density altitudes, and high density altitudes can result in harder openings since decelerations are greater.

HOWEVER this is a pretty minor effect. Even a very significant change* in temperature and humidity will only change density altitude by about 3000 feet, so it's as if you opened 3000 feet higher - and generally that's not a huge difference. You have to be opening pretty high to notice significant changes in opening 'hardness.'

I'd look at other factors first. Hotter temperatures may mean you're wiping your face more while packing (I know I do) and that you have less control over the pack jobs. Hotter temps may mean people are jumping without suits or with summer (fast) suits, and that leads to faster deployment speeds.

(* - in this case, 50 degrees at 10% humidity vs. 90 degrees at 100% humidity.)

>So now I'm wondering if the approaching thunderstorm is the factor I really
>need to consider.

Not that in and of itself. However, its effects on the air may have a minor effect, and its effects on jumpers may be significant as well.

[Divalent 145]

I'm trying to understand (from a physics standpoint) why openings would be harder as the air density is decreased (either due to altitude and/or atmospheric conditions).

I understand that terminal velocity would be faster at lower air densities (whether due to real altitude or to atmospheric conditions), but shouldn't that also affect the processes involved in the canopy opening? I mean, consider two extreme cases where one is opening at terminal V at 12K on a very hot humid day vs a cold dry day at 3K. It seems to me the force of the wind per unit area should be the same in either scenario at terminal V (although terminal V would be faster at 12K). So shouldn't the force of the wind inflating the cells and expanding the canopy be the same? And although from 12K one has to lose more velocity, the force of the wind against a particular surface area of the canopy should be the same, and so shouldn't the decellerating G force be the same?

I suspect I'm overlooking/oversimplifying some step in the opening process. Anybody got a good explanation (or even a good theory) why one would expect openings to be harder at higher altitudes?

[soulbabel 0]

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High temps and humidity result in high density altitudes, and high density altitudes can result in harder openings since decelerations are greater.

Oops, I forgot I always tend to read high density altitude as high density altitude, and then I start thinking in terms of air density.

You're right though, when I jumped at Colorado I noticed the faster freefall speed and canopy descent than I'm used to, but I didn't notice much of a canopy opening harder or softer.

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Hotter temps may mean people are jumping without suits or with summer (fast) suits, and that leads to faster deployment speeds.

That's definitely true about the second jumper I packed for as he was in shorts and long sleeves. He did tell me he tried to slow himself down before deployment, though, after being warned by the first jumper I packed for. The first jumper was in a camera suit though, so I'd assume he was actually going slower.

What are the chances these guys opened up in the updraft of a thermal?

[soulbabel 0]

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4. As density altitude increases, airspeed increases

5. As density altitude increases, a ram-air canopy pilot can expect the following:
c. a faster descent rate
d. higher opening forces

I'm beginning to question that, too. If both your fall rate and your canopy descent rate increase due to the thinner air, it would seem like your canopy opening forces would be more or less equivalent.

[billvon 3,077]

>So shouldn't the force of the wind inflating the cells and expanding the canopy be the same?

Yes, and so it opens at the same _speed_. But if it takes 2 seconds at 3000 feet vs 2 seconds at 12,000 feet, your opening at 12,000 feet will be harder - because you started from 140mph instead of 120mph. Now take it to 30,000 feet and you have 2 seconds to slow down from 180mph - that's really going to hurt.