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NickDG 23
There's an inherent and natural reefing all canopies, round and square, exhibit in high speed environments. It's called squidding. And it means the canopy just can't overcome the power of the passing air molecules to spread until it slows the load down enough.
It's the reason we could do terminal deployments on early squares before rings & ropes and the slider was invented. Squares of the day were way over built so I wouldn't do that today with a small light weight 9-cell, but there is a downside to modern reefing.
If the system starts to slow you down, and then the reefing system fails, for whatever reason then you get a real slammer. My girlfriend, who's an engineer at JPL, was in on deigning the Rovers currently on Mars. When Vertigo (a bunch of eggheads who don't jump) where tasked with designing the parachutes for the Rovers their first few attempts in the wind tunnel got them a huge round with the apex pressurized and a closed skirt. These bozos labored over their sideways math and slide rules without a clue about what squidding was.
B.A.S.E. jumpers are also counting on squidding without realizing it. We use mesh covered sliders on terminal delays not to control the opening so much but to control the lines.
So find yourself a well preserved 1970s vintage Strato Cloud and you could bang out terminal no slider deployments all day long. But you couldn't because the current definition of a hard opening is something you felt . . .
Oh, and that's how they actually did early tandem terminal jumps without a drogue. It wasn't so much the slider as it was squidding . . .
NickD
There's an inherent and natural reefing all canopies, round and square, exhibit in high speed environments. It's called squidding. And it means the canopy just can't overcome the power of the passing air molecules to spread until it slows the load down enough.
It's the reason we could do terminal deployments on early squares before rings & ropes and the slider was invented. Squares of the day were way over built so I wouldn't do that today with a small light weight 9-cell, but there is a downside to modern reefing.
If the system starts to slow you down, and then the reefing system fails, for whatever reason then you get a real slammer. My girlfriend, who's an engineer at JPL, was in on deigning the Rovers currently on Mars. When Vertigo (a bunch of eggheads who don't jump) where tasked with designing the parachutes for the Rovers their first few attempts in the wind tunnel got them a huge round with the apex pressurized and a closed skirt. These bozos labored over their sideways math and slide rules without a clue about what squidding was.
B.A.S.E. jumpers are also counting on squidding without realizing it. We use mesh covered sliders on terminal delays not to control the opening so much but to control the lines.
So find yourself a well preserved 1970s vintage Strato Cloud and you could bang out terminal no slider deployments all day long. But you couldn't because the current definition of a hard opening is something you felt . . .
Oh, and that's how they actually did early tandem terminal jumps without a drogue. It wasn't so much the slider as it was squidding . . .
NickD
Goddamn, Nick...every post I read of yours both from DZ.com and Basejumper.com I always learn something.
Here's to helpful jumpers *beer*
AdD 1
On the dz
Every jumper's dream
3 rigs and an airstream
What was the result of that droptest? Were the canopy or lines damaged? I would love to see some reserve droptest data for various manufacturers posted online.
From: http://www.parachutesaustralia.com/s2/prod_icarus_tan.php
We transferred the Icarus Tandem construction into the Precision TR375 tandem reserve and put it through the FAA TSO process. During the heavy drop testing we gradually increased the weight and speed and eventually dropped the canopy at 250MPH with 900lbs under it (400 KPH with 400 KG) the equivalent of 4 people doing double terminal. Measuring equipment on the dummy showed the total load on the canopy during the opening had been almost 10,000 lbs (4.5 tonne's). The canopy opened perfectly with no damage. (Exit height for these tests was 300ft)
AC DZ
... Guess our atmo buddy's just being reckless, not illegal...
But only if his vertical speed is higher than the normal vertical speed with a drogue. So check this out and let us know if this is the case, before you make your statement.
BTW You can say the same thing (being reckless) about backflip exits I guess.
riggerrob 643
That is more than a 10 G opening!
You sure would not want to be awake for that opening!
We had a similar experience in 1994, when we were drop testing P124A/Aviator (pilot emergency system) prototypes.
After we completed enough heavy-weight (I lost count after 360 pounds) and high-speed drop (205 knots) tests to satisfy TSO C23D, George Galloway (head of Precision Aerodynamics) told us to continue upping the weight. We ran out of day light before we ran out of lead weights.
The moral of the story is that we were not able to tear a P124A canopy made by Precision.
AC DZ
skydiverek 63
http://www.jumpshack.com/default.asp?CategoryID=Video%5FGallery
AdD 1
On the dz
Every jumper's dream
3 rigs and an airstream
mostly, because they do deploy it a little before they pull the main canopy...
http://youtube.com/watch?v=5iV6DRD78k8
Still seems there's no regulations prohibiting drogueless tandems except for the manufacturers'. Guess our atmo buddy's just being reckless, not illegal...
D.S # 125
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