Do you get hard openings before a thunderstorm?

[diablopilot 2]

Humid air is LESS dense than dry air.

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You're not as good as you think you are. Seriously.

[DanG 1]

Put another way, if you look at the equation for drag, the term for velocity is squared, but the term for density is not. The increase in velocity overcomes the decrease in density.

- Dan G

[Scrumpot 1]

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I'm wondering if the moisture is enough to wet the surface of the ZP and therefore cause it to trap air more efficiently.

Let's see... "ZP" = ZERO perosity. How much less than ZERO do you think adding a film of water, or moisture over the surface is gonna provide?

coitus non circum - Moab Stone

[Zymurdoo 0]

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So I was like, "WTF, maybe I am a horrible packer."

That's probably it. You should think about wiping down bowling balls instead of packing parachutes.

Blue Skies, Soft Docks and Happy Landings!
CWR #23
(It's called CRW, add an e if you like, but I ain't calling it CFS. FU FAI!)

[jakee 1,571]

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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.

Exactly the opposite.

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

Exactly the opposite.

Do you want to have an ideagasm?

[soulbabel 0]

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Let's see... "ZP" = ZERO perosity. How much less than ZERO do you think adding a film of water, or moisture over the surface is gonna provide?

I guess I was wrong, I always though a wet canopy opened harder.

[soulbabel 0]

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That's probably it. You should think about wiping down bowling balls instead of packing parachutes.

Looks more and more like that's the case. I think I had too many incorrect assumptions before asking the question, so I think I'll give up it now.

[stayhigh 2]

or did break fire caused the hard opening???

Bernie Sanders for President 2016

[JohnRich 4]

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That's probably it. You should think about wiping down bowling balls instead of packing parachutes.

Looks more and more like that's the case. I think I had too many incorrect assumptions before asking the question, so I think I'll give up it now.

No need to give it up and go bowling. It's good that you're looking for common denominators to explain hard openings. But looking for those explanations in minor weather changes is a waste of time. It would be more productive to examine packing techniques and jumper conditions. Like the guy in shorts and T-shirt without jumpsuit - not only will that give a faster fall rate, but it removes the cushioning effect of the jumpsuit, so that it might feel harder even if it isn't. And hard openings happen now and then no matter how carefully you pack, so it may just be coincidence. But the thing to do is to list the causes of hard openings, like loose rubber band stows, and then take care with your pack jobs to not allow those conditions to exist. Do that, and you can rest assured that you've done everything you can to eliminate hard openings on your customers.

[chuckakers 426]

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"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?

Nope.

What's next? Several people have hard openings on a load just before sunset so we decide that sunset must have something to do with it? How about sunrise, or maybe the moment that the wind turns 180? Maybe at the stroke of noon before the second full moon in a calendar month?

Give me a break already. It's called coincidence.

Chuck Akers
D-10855
Houston, TX

[PiLFy 3]

OK, Chuckles. In my quest for greater understanding. I'll try not to trouble you further.

[PiLFy 3]

Isn't it quite a coincidence that @least five jumpers got slammed within two loads? Three of them being sub-terminal openings, to boot. Aren't the odds of that rather remote? The variables mentioned (faster fall rate, sweaty N rushed packing) can't account for all of them. Are we to take from this that the stars simply aligned perfectly?

[Skyper 0]

it is very easy to check whether your claim is true or not...

the highest humidity region is usually within and around a cloud. The relative humidity is there nearly 100%.

Next time you jump in the cloudy weather open within the cloud and check for yourself.

Please post your findings inhere.

edit:

humid air is indeed less dense than dry air. This means that the terminal speed through humid air is higher than terminal speed through dry air. If higher terminal speed leads to harder opening than this story does make some sense. But I don't believe that humidity may influence terminal speed more than a temperature changes. In other words: do you have harder openings in the summer? If the answer is NO, than the influence of humidity on intensity of the opening is not significant as well.

[JohnRich 4]

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Isn't it quite a coincidence that @least five jumpers got slammed within two loads? Three of them being sub-terminal openings, to boot. Aren't the odds of that rather remote? The variables mentioned (faster fall rate, sweaty N rushed packing) can't account for all of them. Are we to take from this that the stars simply aligned perfectly?

Re-read message #34. Examine the way those five chutes were packed, by whom, the condition of the equipment, and the circumstances of the deployments.

Yes, it would be highly unlikely that these were all just coincidence, but still, it could happen. I was once in a 4-way dive, where three of us all experienced malfunctions on deployment. Long odds, heck yeah. But we didn't blame it on the weather. Those unlikely odds are why you examine things to figure out why they happened. Blaming it on the weather is a no-go - look for REAL causes of hard openings.

[PiLFy 3]

OK, Thank You John.

[mjosparky 4]

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I'll try not to trouble you further.

Are we to take from this that the stars simply aligned perfectly?

Instead of being a smart ass try paying attention to what is being posted. Not all responses will be tailored to your liking but you can still learn from them.

Weather does not affect the deployment or opening characteristics of a canopy.
As John posted, look for a communally of conditions that would increase opening forces. Jumper related could be body position or deployment speed. If the jumper had one shoulder low it would cause an asymmetrical loading of lines. If the jumper was FF he may not have slowed down before deployment. This will decrease the fill time of the canopy and increase felt snatch force and opening shock. During packing the packer/s may have allowed the slider to creep down the lines while bagging the canopy. This is a sure fire way to get a hard opening.

Sparky

My idea of a fair fight is clubbing baby seals

[PiLFy 3]

You still sore about the last time, Sparkplug? Get over it...

[PiLFy 3]

http://www.theweatherprediction.com/habyhints/260/

Paradoxical but true, Thank You.

[airtwardo 7]

http://www.youtube.com/watch?v=PROnG9ATBGI

Not even IN the rain...

~ If you choke a Smurf, what color does it turn? ~

[soulbabel 0]

Just curious, but what are the odds that a skydiver may pass through an updraft thermal during the deployment process? Is the column of air traveling fast enough to be of any significance?

[Skyper 0]

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Just curious, but what are the odds that a skydiver may pass through an updraft thermal during the deployment process? Is the column of air traveling fast enough to be of any significance?

in theory, when object is falling and the wind is blowing vertically into that object... wind will only reduce the objects vertical absolute speed. In theory this kind of wind will slow you down and your relative speed will remain unchanged.

in practice the influence of vertical current on opening sequence is not significant. but of course it may influence what is happening after the opening... since you're going from falling into the gliding mode.

your body position is the variable that influence your falling speed and your opening sequence in the most profound way.

[soulbabel 0]

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in theory, when object is falling and the wind is blowing vertically into that object... wind will only reduce the objects vertical absolute speed. In theory this kind of wind will slow you down and your relative speed will remain unchanged.

In this situation, is the the updraft thermal like a steady current? I wasn't completely confident about the shape of a thermal, as to whether it was like a column or a bubble.

If it was like a bubble, though, would it be possible that while the jumper is mid-deployment and the canopy is sniveling, he could pass through a bubble traveling upward, thus speeding the opening of the canopy? I assume this is highly improbable, but I thought it was an interesting situation.

[JohnRich 4]

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Weather does not affect the deployment or opening characteristics of a canopy.
As John posted, look for a communally of conditions that would increase opening forces. Jumper related could be body position or deployment speed. If the jumper had one shoulder low it would cause an asymmetrical loading of lines. If the jumper was FF he may not have slowed down before deployment. This will decrease the fill time of the canopy and increase felt snatch force and opening shock. During packing the packer/s may have allowed the slider to creep down the lines while bagging the canopy. This is a sure fire way to get a hard opening.

To add to Sparky's comments... Just because four people on two loads had hard openings doesn't mean that they were all caused by the same thing. Each could have had it's own cause, independent of all the others. One could have been failure to fold the nose inward, another a failure to secure the slider against the upper stops, the next a failure to use properly sized rubber bands, and so on. So they shouldn't be looking for only universal causes, but also for separate individual causes.

[Skyper 0]

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in theory, when object is falling and the wind is blowing vertically into that object... wind will only reduce the objects vertical absolute speed. In theory this kind of wind will slow you down and your relative speed will remain unchanged.

Is this situation, is the the updraft thermal like a steady current? I wasn't completely confident about the shape of a thermal, as to whether it was like a column or a bubble.

If it was like a bubble, though, would it be possible that while the jumper is mid-deployment and the canopy is sniveling, he could pass through a bubble traveling upward, thus speeding the opening of the canopy? I assume this is highly improbable, but I thought it was an interesting situation.

except if you are in the middle of a thunderstorm the speeds of vertical winds in turbulent weather conditions are very very low and do not influence the opening sequence in significant way.

What we experience as "turbulence" under canopy is the difference of only few kilometers per hour in the vertical wind speed.

[funfall 0]

I just read this in CRW instructional material, so will pass it along as one more potential source of a subterminal hard opening during h&p. (no personal experience, as I delay enough to avoid it.)

"Throwing the pilot chute into the prop wash will give you a harder opening."

from:
http://homepages.onsnet.nu/~CaTo/cf2/Learning%20to%20fly%20CF.pdf

Risk may be higher exiting certain planes, I would guess.