packing in high humidity and jumping in extreme cold!!

[milehighpres 0]

i would not only like everyone opinion on this. but i need to know the real information on this. if you packed your parachute (main or reserve) in regular -high humidity. and you went and jumped in northern alaska (extreme cold) what would happen to it upon opening? would it open regularly, would it freeze into a block and not come out of the d-bag?? what would happen

OPINIONS and FACT (if possible)

"the sky is not the limit....the ground is"

[phoenixlpr 0]

Define extreme cold!

I jumped when ground temperature was about -5 - 15C in Finland. It was not more than 10C in our packing hall and it was quite humid there. My right was stored in a room with temperature over 10C. I had usual openings.

The key could be pack it before you jump it and keep it in a worm place.

I've read about a BASE fatality where a rig was packed wet and got frozen. That canopy said to be a solid brick of ice.

[stayhigh 2]

i heard somewhere that if you have wet canopy and extreme low temp will freeze the canopy... and won't open...

Bernie Sanders for President 2016

[milehighpres 0]

are there any actual reports on this or is it all hearsay??

and cold asa in like the -5 -15c that you described

"the sky is not the limit....the ground is"

[ernokaikkonen 0]

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are there any actual reports on this or is it all hearsay??

#6 on The List.

[IanHarrop 37]

So I guess the solution is:

If you have any questions about a pack job, open your canopy and re-pack it, you would have blown that 15 minutes shooting the shit with someone. Just have them there while you're re-packing and you can still have that same conversation.

Of course, this applies not just to "did my canopy get wet and freeze into block" but to anytime you have a question. I've re-packed a few times just to remove any question about a pack job, perhaps done by me or people that have packed for me, and the exercise didn't kill me.

Blue ones!

"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy

[martin-o 0]

Look at #6 at the BASE fatality list

http://hometown.aol.com/base194/myhomepage/base_fatality_list

/Martin

[tdog 0]

Humidity vs wet....

I can't honestly see any way non-condensing humidity would turn into thick enough ice between the layers of fabric to cause enough cohesion between the fabric to keep the canopy from opening.

There is just not that much air, able to hold the humidity, inside a packjob.


Ok - the science content... Lets say you packed at 100% relative humidity (the maximum water content in the air before it rains/condenses) - at 25 degrees C (77F) - 100 grams of air would hold 2 grams of water.

The density of air at ordinary atmospheric pressure and 25°C is 1.19 g/L. A sport parachute DBag contains between 10-20 liters of content - so at an average 15 liters, with no canopy, the bag would contain 17.85 grams of air. 17.85/100*2 = 0.357 grams of water.


Knowing the air inside the dbag could hold less than 0.357 grams of water in worst case scenarios, which is basically a drop of water, there is not enough water to cause enough cohesion for 150 square feet of fabric to stick together.

Now - can the ZP fabric absorb enough water to become rigid and stuck together. ZP is not exactly the most water absorbing material made... So I ran a quick experiment. I took the opposite of ZP - a paper towel designed to absorb water. I saturated it in the sink, squeezed out any excess, folded it in half, and put it in my freezer. The towel was stuck together, but came apart with some force and be could be crinkled up - proving that it was not so stiff it could not change its shape.

So - if you take your rig and get it wet with the addition of water (spill, water landing, etc) - I believe it could freeze and cause issues, especially if there is standing water between the layers of folded fabric. But there is some new evidence that wet canopies even unfrozen may cause issues.

But, if you pack your rig at 100% humidity and take it to a cold climate (where the moisture in the air between the fabric will condense) - there simply is not enough water content in the air to cause any issues.

And - as you take your rig to a different climate, it will find equilibrium with the air - meaning if the canopy has some moisture content different than the air around it - the moisture will wick out. If you think the container is too thick for moisture to wick - consider a building that flooded. They installed dehumidifiers inside the building and made it very dry compared to the outside world. The restoration company could not understand why the walls would never dry out. The reason was because the moisture from the outside world was traveling thru a foot of cinder block walls and getting stuck in the drywall on the way in the building. As soon as they turned off the dehumidifiers, the walls quickly dried as the moisture was no longer trying to get in the building... So a rig will do the same thing - in the aircraft on the way to Alaska in your example, humidity levels inside the rig will find equilibrium with the dryer air.


So, while I have not tried it and do not suggest anyone should if they are concerned, I claim "myth busted" - a rig packed in high humidity will not have enough moisture content to freeze into a brick in very cold climates.

[Titanman2789 0]

this could be something for mythbusters to try out. with dummies of course, not real people

[RiggerLee 61]

I know of at least one incedent where a rig was taken inside from the cold and condensation formed on the rig. It was an f111 pilot chute and when he took the rig back out into the cold the condensation that had formedon the boc froze glueing the pc in place. It could not be broken in shear. The rig had never been alowed to warm all the way up to room temp.

Lee

Lee
[email protected]
www.velocitysportswear.com

[JohnRich 4]

Perhaps a related example of how this can happen...

In the military, serving in a freezing combat environment, you are taught to leave your rifles outside when coming indoors for something, and post a guard with the rifles. The reason for that is that if you bring them indoors, condensation will form, which will freeze up when you go back outside. The action will then be frozen shut, and you have an inoperable rifle.

[popsjumper 2]

Quote

So I guess the solution is:

If you have any questions about a pack job, open your canopy and re-pack it, you would have blown that 15 minutes shooting the shit with someone. Just have them there while you're re-packing and you can still have that same conversation.

Words of wisdom well worth repeating.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[tdog 0]

Quote

Perhaps a related example of how this can happen...

In the military, serving in a freezing combat environment, you are taught to leave your rifles outside when coming indoors for something, and post a guard with the rifles. The reason for that is that if you bring them indoors, condensation will form, which will freeze up when you go back outside. The action will then be frozen shut, and you have an inoperable rifle.

That is because you are taking a cold piece of metal indoors, where the temperature of the metal is below the dew point of the humid air inside... This is the same reason condensation/frost appears on the side of your mug if the mug is stored in the freezer before the is poured. If you leave that glass on the counter for an hour, the frost will melt to water, then the water will eventually evaporate after the outside of the mug reaches slightly above the dew point temperature.

If you took the rifle inside, let the condensation form, then let the rifle warm up to above the dew point of the air, then let the condensation evaporate, then took it outside - you would not have the problem... The problem is, in a quick dinner break, this complete cycle cannot occur - leaving moisture to refreeze.

However, the reason why you get so much condensation is because there is a lot of air inside, and it is allowed to condense...

Another way to prevent the condensation would be to seal the rifle in a plastic (impervious to moisture) container, take it inside, and let it warm up above the dew point. The condensation would be limited to the amount of moisture in the bag - less than a drop... Not enough to jam the weapon.

Back to a skydiving rig in the original post... The poster's question was, would a rig packed in warm humid environments freeze when taken to cold temperatures. While I of course would open a pack job and inspect if I had a fear - I don't believe it is of concern because unlike the rifle example, the parachute started warmer than the dew point, and it holds limited quantities of air inside the dbag and container - so it is actually the opposite of the rifle in terms of

1) The temperature difference between the surface of the material and the ambient air (Cold gun vs Warm parachute)

2) The amount of moisture laden air surrounding the material (Entire air content of the building vs the amount of air between the layers of fabric)

So while I learned something new about military rules and procedures by reading your post, I am going to suggest that perhaps I disagree if it has anything to do with the original question... However, I do agree that - if you have a very cold rig, bring it inside and let condensation form, and do not let it dry before taking it back outside, that would be an issue.

So, if you have a skydiving rig that is very cold and you want to bring it inside for a short while - seal it in a garbage bag with limited air in it, and you will not get any condensation issues...

[Guinness_fr 0]

In terms of physics you're definitely right, but what about chemistry?

The products used on our canopies and lines do react to humidity and temperature.
That is something that cannot be left out of the equation and which probably explains the previous example of a stuck pilot chute.

[phoenixlpr 0]

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The products used on our canopies and lines do react to humidity and temperature.

That's still physics. Our rig does not react with clean water.

[martin-o 0]

You could call it colloidal chemistry. The possibilities are endless

[Guinness_fr 0]

Both the canopy and the lines are coated with products that may behave badly under certain temp/humidity conditions.

If you think that you can store your canopy in a humid cold environment simply because someone demonstrated that it won't physically freeze your canopy, please think again.

I think the physic argument is valid to answer the OP's question; but I certainly don't want people to start thinking that it's ok to store your rig in a cold, humid environment.