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celayne

Skyhook input wanted

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Obviously a lot of variables like canopy type & rigger influence can make a difference, but unless the clocks on the videos are way off...


The clocks aren’t off, you are correct and I have learned a bunch and proven a theory.
Both cutaways were from fully deployed mains. That hurts the RSL and helps the Skyhook.
Reason: The RSL is always the same; it is consistent because it always uses the pilot chute which will always have the same drag capabilities. The Skyhook is faster when it has the very high drag of a fully inflated canopy but it will slow down depending upon the drag of the malfunctioned main. As the drag of the main (which is working as a pilot chute) decreases due to an increased severity of a malfunction on the main, the rapidity of the deployment also decreases. My previous views and timings were of higher speed mals to the extent where the malfunctioned main had no drag and the main pilot chute was doing all of the work. This can be dangerous if the main PC is collapsible and has collapsed. In a bag lock the collapsible PC doesn’t collapse with the bag closed. This is where Tandem gets tricky. The drogue has already collapsed upon release and is not available to assist the main if it has deficient drag. So now we are back to depending on the reserve pilot chute which if any good we wouldn’t need the Skyhook.

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Obviously a lot of variables like canopy type & rigger influence can make a difference, but unless the clocks on the videos are way off...


The clocks aren’t off, you are correct and I have learned a bunch and proven a theory.
Both cutaways were from fully deployed mains. That hurts the RSL and helps the Skyhook.
Reason: The RSL is always the same; it is consistent because it always uses the pilot chute which will always have the same drag capabilities. The Skyhook is faster when it has the very high drag of a fully inflated canopy but it will slow down depending upon the drag of the malfunctioned main. As the drag of the main (which is working as a pilot chute) decreases due to an increased severity of a malfunction on the main, the rapidity of the deployment also decreases. My previous views and timings were of higher speed mals to the extent where the malfunctioned main had no drag and the main pilot chute was doing all of the work. This can be dangerous if the main PC is collapsible and has collapsed. In a bag lock the collapsible PC doesn’t collapse with the bag closed. This is where Tandem gets tricky. The drogue has already collapsed upon release and is not available to assist the main if it has deficient drag. So now we are back to depending on the reserve pilot chute which if any good we wouldn’t need the Skyhook.




http://www.youtube.com/watch?v=bmmxBP2zp9o


Almost looks like the reserve pilot chute beats the skyhook as you suggested.










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

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Almost looks like the reserve pilot chute beats the skyhook as you suggested.



It does.
I downloaded the video and brought it into my Video Editor which has been down for over a week. Your first capture “Bag lock chop” is a long time after Riser Release. The risers are halfway up the fully extended reserve bridle. On my time line it occurs at 1:01.05
I used a different time line but they are all relative. I get:
Chop @ 1:00.10
Your Bag Lock Chop picture @1:01.5
Reserve bag out of container@ 1:01.09
Reserve landable/slider down @ 1:08.08

Remember that 13 foot bridle with a PC on one end and a bag on the other is about 16 feet or the distance of separation in the first second. That is commensurate with my observation.
From Chop to Landable I get 7 seconds and 23 frames @ 25 FPS that’s 7.92 seconds.
I don’t believe you can give the Skyhook much credit for this one.


Incidentally; This is a great video to show how a tandem pair go onto their back when a bag lock occurs. Vasilli was correct.

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From Chop to Landable I get 7 seconds and 23 frames @ 25 FPS that’s 7.92 seconds.



Judging from those time stamps and the duration from chop to the canopy open and landable... I think you were only looking at the slow-motion portion, not the full speed one immediately afterwords.
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Almost looks like the reserve pilot chute beats the skyhook as you suggested.



It does.
I downloaded the video and brought it into my Video Editor which has been down for over a week. Your first capture “Bag lock chop” is a long time after Riser Release. The risers are halfway up the fully extended reserve bridle. On my time line it occurs at 1:01.05
I used a different time line but they are all relative. I get:
Chop @ 1:00.10
Your Bag Lock Chop picture @1:01.5
Reserve bag out of container@ 1:01.09
Reserve landable/slider down @ 1:08.08

Remember that 13 foot bridle with a PC on one end and a bag on the other is about 16 feet or the distance of separation in the first second. That is commensurate with my observation.
From Chop to Landable I get 7 seconds and 23 frames @ 25 FPS that’s 7.92 seconds.
I don’t believe you can give the Skyhook much credit for this one.


Incidentally; This is a great video to show how a tandem pair go onto their back when a bag lock occurs. Vasilli was correct.



Yeah I'm just using movie player on an old Dell, I know there were frames I couldn't 'stop' the player on...best I could do.

I could kinda tell the PC beat the SH but with this computer I couldn't be sure.

Thanks for the clarification.










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

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Obviously a lot of variables like canopy type & rigger influence can make a difference, but unless the clocks on the videos are way off...


The clocks aren’t off, you are correct and I have learned a bunch and proven a theory.
Both cutaways were from fully deployed mains. That hurts the RSL and helps the Skyhook.
Reason: The RSL is always the same; it is consistent because it always uses the pilot chute which will always have the same drag capabilities. The Skyhook is faster when it has the very high drag of a fully inflated canopy but it will slow down depending upon the drag of the malfunctioned main. As the drag of the main (which is working as a pilot chute) decreases due to an increased severity of a malfunction on the main, the rapidity of the deployment also decreases. My previous views and timings were of higher speed mals to the extent where the malfunctioned main had no drag and the main pilot chute was doing all of the work. This can be dangerous if the main PC is collapsible and has collapsed. In a bag lock the collapsible PC doesn’t collapse with the bag closed. This is where Tandem gets tricky. The drogue has already collapsed upon release and is not available to assist the main if it has deficient drag. So now we are back to depending on the reserve pilot chute which if any good we wouldn’t need the Skyhook.



In general, wouldn't a malfunctioning main generate more than the 18lbs of drag on a RPC? Even in a baglock or streamer situation? In a baglock, the main's PC is still functioning, correct? Therefore, a Skyhook should generally be faster than an RSL right?
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In general, wouldn't a malfunctioning main generate more than the 18lbs of drag on a RPC? Even in a baglock or streamer situation? In a baglock, the main's PC is still functioning, correct? Therefore, a Skyhook should generally be faster than an RSL right?



I would say yes the skyhook would be faster in almost all situations. Bag locks are an exception though as they could go either way. The beauty of the skyhook is that if the PC ends up being faster the skyhook is designed to seperate from the main and allow for a standard deployment.

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In general, wouldn't a malfunctioning main generate more than the 18lbs of drag on a RPC? Even in a baglock or streamer situation? In a baglock, the main's PC is still functioning, correct? Therefore, a Skyhook should generally be faster than an RSL right?



Nope....

The Drogue ( PC ) on a Sigma Tandem collapses before it pulls the bag.
The Racer RPC generate 190 lbs pull force at terminal.

The problem with the skyhook is that the system is complicates and yet unreliable. Sometimes it does its job, sometimes it doesn't. And that has nothing to do with the drag of the main. Spinning main will produce a lot more drag than any RPC and yet, skyhooks disconnects.

Check this video out:

http://www.youtube.com/watch?v=bzKd8e47icY

A streamer will produce enough force to stand the tandem pair up, but apparently less than the mesh less Vector 2 RPC.
I can't believe that...
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In general, wouldn't a malfunctioning main generate more than the 18lbs of drag on a RPC? Even in a baglock or streamer situation? In a baglock, the main's PC is still functioning, correct? Therefore, a Skyhook should generally be faster than an RSL right?



I would say yes the skyhook would be faster in almost all situations. Bag locks are an exception though as they could go either way. The beauty of the skyhook is that if the PC ends up being faster the skyhook is designed to seperate from the main and allow for a standard deployment.



Yes, check the segment starting at 8:08:

http://www.youtube.com/watch?v=z-WBBLAgE_s

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In general, wouldn't a malfunctioning main generate more than the 18lbs of drag on a RPC? Even in a baglock or streamer situation?



No, and the bad part is that you can't rely on it or predict it. It varies from way more drag than you need to not enough drag. You could have in situations such as twisted lines and a full canopy where you got more drag than you need, but there are videos of streamers on YouTube that, because you are vertical, you are falling faster than you would be if you were on you belly, no drag there. If your main pilot chute is collapsible, as it always is on Skyhook tandem, you will have no drag and you must go back to and rely on the reserve pilot chute which has only 2.3 Effective Sq. Ft.
At the point in the deployment where you are quoting 18 pounds (1 second after release from a 20FPS descending main at 2000 ft. on that model of pilot chute only) there is only 3 pound per sq. ft. resistive pressure available.
With 2.3 Effective Square feet on the Skyhook reserve pilot chute you will have only 6.9 pounds of drag not 18. That’s why some rigs have a Skyhook. It takes more than 6.9 pounds of drag to pull a tightly packed bag out of the reserve container especially if the reserve weighs more than 7 pounds.

The point is; that the Skyhook is sometimes faster and sometimes slower than a Racer with an RSL. The Racer will be predictable and consistent and the Skyhook will vary depending on the severity of the malfunction.

BTW: That 18 pound number you have latched on to is the maximinum allowable extraction force of the reserve bag on any rig. Most pilot chutes will just barely pull it and some won't at all. They are the ones who need a Skyhook.

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Hi blue,

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wouldn't a malfunctioning main generate more than the 18lbs of drag



Back about 1965, when the Stevens Lanyard was first put into general useage, someone found a PhD physicist who did some calculations. He used an average weight person, the length of the lanyard, etc, etc, and came up with a force at the reserve ripcord handle of something on the order of 9,000 lbs.

I doubted his numbers as the time & still doubt them. But if you take a 100 lbs and drop it 2 ft or so, you will generate a lot of force at the end of the line ( or lanyard :P ).

Just my rememberances,

JerryBaumchen

PS) When I was doing the testing of the RAX System I tested would it would take to just break the red riggers thread tacking and came up with an average of 25 lbs; the high being 26 lbs and the low being 24 lbs. I did a lot of drops in my garage and the tacking always broke very quickly. For those drops I used a total weight of ~30-35 lbs.

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Personally, I don't see the downside of the extra complexity as being worth it to 'me'...but in the right circumstances it does seem to do it's job.



This is about how I feel about it - my current rig has a Skyhook, but it's a pretty even decision either way and I wake up feeling differently about it about once a week. I am very pro-RSL, but a bit conflicted nowadays about the MARD part.

One thing that nobody here has mentioned yet though is the Collins lanyard built into the Skyhook. Extra complexity for sure, but it certainly feels like an important safety feature if you're going to have an RSL at all.

(Also, to newer jumpers who watch that Petra mal video and suddenly realise they want a Skyhook - are you jumping a tiny experimental canopy and doing massive turns into the gates? Then maybe not so useful as an example. Note this goes for me too :P)
--
"I'll tell you how all skydivers are judged, . They are judged by the laws of physics." - kkeenan

"You jump out, pull the string and either live or die. What's there to be good at?

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Also, to newer jumpers who watch that Petra mal video and suddenly realise they want a Skyhook - are you jumping a tiny experimental canopy and doing massive turns into the gates? Then maybe not so useful as an example.



Yeah, that kind of stuff can only happen to those tiny, experimental canopies under extreme circumstances. Equipment failures or malfunctions don't happen to 'normal gear'.

;)

Why are you pro-RSL?
Why are you sometimes conflicted about MARD's?

Maybe just me, but if I felt conflicted about any part of my kit, it would stay on the ground.

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One important feature of the skyhook, when having a spinning malfunction or when the jumper's body is not being vertical, both followed by a cut away, is that the reserve deployment is done with bridle, risers and jumper's body in line. That provides a better chance for an uneventful deployment since both sides of the reserve canopy will inflate at the same time.

OTOH, when a reserve is deployed by its pilot chute, this pilot chute goes up vertically whatever is the position of the jumper. If the jumper's body is sideway or not in line with risers, the lowest riser lines will make the corresponding part of the canopy inflate first creating possible inflation problems
Learn from others mistakes, you will never live long enough to make them all.

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I watched that a few times. Those were fast!

I want one! The reality is that I'll probably never "need" one as opposed to an RSL... But I want one. I also hope to never find out exactly where the line is.

Also, I've looked for other skyhook videos. The owner of that one should change the title or add key words so that it comes up under a search for "Skyhook".



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Another Skyhook compilation:

http://www.youtube.com/watch?v=5PBgEfJ4PAU

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It is easy to think that a MARD has no disadvantages, or only minimal problems that could happen in only rare circumstances. Before people conclude this, consider that a guy intimately involved with the concept thinks that it shold only be applied when you might need to cutaway at a few hundred feet. Here is his contribution to the topic:

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=4299972#4299972
People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

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One important feature of the skyhook, when having a spinning malfunction or when the jumper's body is not being vertical, both followed by a cut away, is that the reserve deployment is done with bridle, risers and jumper's body in line. That provides a better chance for an uneventful deployment since both sides of the reserve canopy will inflate at the same time.

OTOH, when a reserve is deployed by its pilot chute, this pilot chute goes up vertically whatever is the position of the jumper. If the jumper's body is sideway or not in line with risers, the lowest riser lines will make the corresponding part of the canopy inflate first creating possible inflation problems



Why would the reserve pilot chute pull in a different direction a cutaway main canopy?

The strength of the spring is not going to extract the bag (as we know from ground cutaways) and the relative wind would affect both the PC and the cutaway main in the same direction.
"The ground does not care who you are. It will always be tougher than the human behind the controls."

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Why are you pro-RSL?
Why are you sometimes conflicted about MARD's?

Maybe just me, but if I felt conflicted about any part of my kit, it would stay on the ground.



That's actually a fair question (especially the last implied one).

So... I'm pro-RSL because I think the getting a reserve pilot chute out as soon as the main is cut away is more useful than being able to time your reserve deployment after cutaway, for most of us. CRW (voluntary or otherwise) aside, it just doesn't seem helpful. Whereas trying and failing for stability, losing alti awareness, dislodging or being unable to grasp the reserve handle, are all things that have happened to otherwise pretty together people.

If you have a big snaggy camera mount, I can see the point. If you have a canopy where malfunctions are going to be radical, then that's just not something I know that much about. But for most of us, the balance of probability seems to side with it being a good idea.

Conflict about MARDs is just to do with benefit. They cost a bunch of money, they give riggers and container manufacturers more opportunity to make mistakes, they force design changes in rigs to accommodate them, and they make people feel safer than maybe they are.

In return, they get a reserve out slightly quicker, maybe in a better orientation... sometimes.

On balance I think my Skyhook makes me safer, probably. Now that I've shelled out for it. But I'm just less convinced it was a no-brainer than I am about the plain ol' RSL on my previous rig.
--
"I'll tell you how all skydivers are judged, . They are judged by the laws of physics." - kkeenan

"You jump out, pull the string and either live or die. What's there to be good at?

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Why would the reserve pilot chute pull in a different direction a cutaway main canopy?



The higher extraction force of a MARD limits the potential for the jumper to rotate off axis after a cut away. A standard RSL takes longer to function and therefore allows more time for the jumper to possibly tumble after cutaway.

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Conflict about MARDs is just to do with benefit. They cost a bunch of money,


Not that much money, especially not if you price it out over the lifetime of the rig. $250 over 1000 jumps is 25c a jump and we know that harnesses can last 10 times that long.
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they give riggers and container manufacturers more opportunity to make mistakes,


Firstly I don't see this at all. Definitely not more so than any other components on the rig. And lets face it, there are a number of RSL designs on the market that actually have caused incidents and fatalities. Unless someone corrects me on this I am not aware of any Skyhook related fatalities. So your argument for RSL over Skyhook is flawed here.

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In return, they get a reserve out slightly quicker, maybe in a better orientation... sometimes.


I would say it gets the reserve out significantly faster and in a much better orientation and lot more than just "sometimes". I can understand the Skyhook no Skyhook debate but I cannot relate to your RSL over Skyhook debate. Especially if you begin to reference costs as a factor.

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Unless someone corrects me on this I am not aware of any Skyhook related fatalities. So your argument for RSL over Skyhook is flawed here.



There was the NC tandem double fatality a few years ago. A Cypres fire during the main canopy snivel that caused the reserve bag to fall out and backload the red skyhook lanyard. A cutaway soon followed and the reserve never came out of the bag. In response UPT modified the packing process to include the staging loop to prevent this seemingly rare type of accident. That's the only one I can think of.
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Unless someone corrects me on this I am not aware of any Skyhook related fatalities. So your argument for RSL over Skyhook is flawed here.



There was the NC tandem double fatality a few years ago. A Cypres fire during the main canopy snivel that caused the reserve bag to fall out and backload the red skyhook lanyard. A cutaway soon followed and the reserve never came out of the bag. In response UPT modified the packing process to include the staging loop to prevent this seemingly rare type of accident. That's the only one I can think of.



As far as I understand it the theory of the skyhook backloading was entirely speculation.

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In response UPT modified the packing process to include the staging loop to prevent this seemingly rare type of accident.



Yes UPT did add the staging loop to ensure that the free bag would stay in the container in the event of a low pull/snivelling main/cypres fire/low speed scenario. This was to help prevent a two out scenario in the even that you snivel into cypres fire altitudes.
Do not interpret this as UPT adding the staging loop to prevent the freebag from backloading the skyhook to effect a cut away.

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