Cut away at 100 feet??

[councilman24 36]

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Where do you find this stuff online?!

He didn't find it online, unless it's bootleg. SAE sells AS 8015B for $59. They have indicated that they will not revise it. That's why PIA TS-135 has been submitted to replace it. But there have been known to be copies of copies of copies floating around.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[Squeak 17]

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Wet behind the ear know-it-alls don't need glimmers of hope to encourage foolish behaviour.

Am I a wet-behind-the-ears know-it-all?

Why yes Dave Yes you are Welcome to our club

You are not now, nor will you ever be, good enough to not die in this sport (Sparky)
My Life ROCKS!
How's yours doing?

[peregrinerose 0]

Does anyone know how long it would take with the slider packed in the normal fashion, so there is accurate comparison between skyhook, RSL, no RSL?

Do or do not, there is no try -Yoda

[tso-d_chris 0]

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I think the truth should always be told so that people can make informed decisions based on facts. What they do with it is up to them.

It is unfortunate so much gear is not marketed with this philosophy.

For Great Deals on Gear

[billbooth 10]

We can ESTIMATE the distance from breakaway to "open" reserve if we know the initial descent before breakaway, and the time to a "fully open" reserve. It is hard to directly measure this distance using pressure sensing devices because the rapid change in body position during opening shock, as well as the shock itself, tends to make such readings unreliable.

Estimates from watching video of Skyhook deployments seem to indicate breakaway to "fully open" reserve can take as little as 70 feet, with average sized, normally packed, sport equipment. At this point the reserve is fully inflated, but we don't really know how "survivable" a landing at that exact moment would be...and volunteers willing to find out have so far been rather scarce.

The major problem with this "how high do I have to be when I breakaway?" argument is that skydiving altimeters are not all that accurate, and there is always some amount of time, and therefore lost altitude, between making the decision to breakaway, and actually doing it. (Hell, just the time it takes to look at your altimeter could easily cost you an additional 100 feet.) Plus, depending on how fast your main is spinning, and how long you have been riding it, your ability to respond quickly may have been seriously compromised. At the end of our Skyhook video, a very experienced jumper, with previous breakaways, takes a full 5 seconds from the time his hands leave the risers (decision time) until he finally locates and pulls his breakaway handle. He then takes four more seconds to locate and pull his reserve! So, he was well above 1,000 ft. when he decided to breakaway, yet he was only about 10 feet above the ground when the reserve actually opened.

And please remember, the main purpose of the Skyhook was "better" reserve openings. Faster is only a side effect.

[peregrinerose 0]

Thank you for the extra information!

Do or do not, there is no try -Yoda

[jloirsdaan 0]

And please remember, the main purpose of the Skyhook was "better" reserve openings. Faster is only a side effect.***

Thats awesome, thanks for that!

Jordan

Go Fast, Dock Soft.

[ZigZagMarquis 8]

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If you want to know more about how reserves work, grab one of the packers/riggers at the DZ and ask... preferably later in the afternoon once the work is pretty much over.

... and take them Beer!
Anyway... up post... thanks for the 411 on the Skyhook video with the base jumpers chopping at 100ft having had their resrves packed slider off (or down ?). I didn't know that part. Still impressive though.

[nicknitro71 0]

Bill,

A S/L BASE deployment burns up about 75'. That is possible due to specific canopies designed to pressurize very quickly and packed without a slider.

I do not understand how a SD reserve packed slider up can achieve a full inflation in only 70'. Even if the skyhook was virtually anchored to the sky (and it's not) you still have to deal with a reserve that uses a sail slider, that it is not free-bagged, and not designed to open incredibly fast.

I just don't get it.

Memento Audere Semper

903

[tso-d_chris 0]

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Bill,

A S/L BASE deployment burns up about 75'. That is possible due to specific canopies designed to pressurize very quickly and packed without a slider.

I do not understand how a SD reserve packed slider up can achieve a full inflation in only 70'. Even if the skyhook was virtually anchored to the sky (and it's not) you still have to deal with a reserve that uses a sail slider, that it is not free-bagged, and not designed to open incredibly fast.

I'm interested to hear how he got around Physics, as well.

By doing the math, one can determine that from a cutaway with a vertical descent rate of 29 mph (used arbitrarily, as the student CYPRES malfunction activation speed), it will take about 30 feet (assumes main canopy completely ceases descent at cutaway) to reach line stretch. A 70 ft deployment from cutaway would imply 40 feet for the canopy to leave the free bag, open and inflate.

As you pointed out, BASE equipment does not open that quickly. It is unreasonable to expect a slider up reserve canopy to open more quickly.

For Great Deals on Gear

[riggerrob 561]

Even if the skyhook was virtually anchored to the sky (and it's not)

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Main risers recoil/rebound when you cutaway, so they might even go back up for the first couple of seconds after a cutaway.

[tso-d_chris 0]

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Bill,

A S/L BASE deployment burns up about 75'. That is possible due to specific canopies designed to pressurize very quickly and packed without a slider.

I do not understand how a SD reserve packed slider up can achieve a full inflation in only 70'. Even if the skyhook was virtually anchored to the sky (and it's not) you still have to deal with a reserve that uses a sail slider, that it is not free-bagged, and not designed to open incredibly fast.

I'm interested to hear how he got around Physics, as well.

By doing the math, one can determine that from a cutaway with a vertical descent rate of 29 mph (used arbitrarily, as the student CYPRES malfunction activation speed), it will take about 30 feet (assumes main canopy completely ceases descent at cutaway) to reach line stretch. A 70 ft deployment from cutaway would imply 40 feet for the canopy to leave the free bag, open and inflate.

As you pointed out, BASE equipment does not open that quickly. It is unreasonable to expect a slider up reserve canopy to open more quickly.

This assumes the 1/2 second elapsed time until canopy leaves freebag, as advertised by RWS. It also assumes the canopy leaves the freebag at approximately the same moment as line stretch occurs.

For Great Deals on Gear

[billbooth 10]

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Bill,

A S/L BASE deployment burns up about 75'. That is possible due to specific canopies designed to pressurize very quickly and packed without a slider.

I do not understand how a SD reserve packed slider up can achieve a full inflation in only 70'. Even if the skyhook was virtually anchored to the sky (and it's not) you still have to deal with a reserve that uses a sail slider, that it is not free-bagged, and not designed to open incredibly fast.

I just don't get it.

A static line deployed base rig starts off with "0" airspeed, while a breakaway from a gliding main already has a lot of airspeed. This significantly speeds up deployment time. But, like I said, my distance calculations are only estimates from video. Whatever the real number is, the fact remains that a Skyhook will get your reserve open faster than a pilot chute by a long shot...and I've read a lot of reports of people without RSL's going in at line stretch. It seems that quite often, every foot counts.

[nicknitro71 0]

Bill,

Thanks for stepping in.

However, a gliding main does not have all that airspeed otherwise those jumpers who cutaway with the skyhook and slider off reserves would have been hurt by the deployment and having seen the video, there does not seem to be all this airspeed.

Don't get me wrong, being a fan of the RSL I see the superiority of the skyhook and I wish I could install it in all my SD rigs.

The problem I have is this 70' deployment. I have already heard of skydivers arguing that because they have a skyhook they could cutaway at 100' and survive. That it just ain't gonna happen! At least not with a slider up reserve. 100' is ridiculously low.

Knowing the little I know about canopies, I would say that a ~250' deployment is more of a realistic figure for the skyhook.

Again my hat's off for the invention but I just would hate to see a wrong message being delivered and causalities to follow.

just my .02

Memento Audere Semper

903

[billbooth 10]

I agree. I don't advocate anyone cutting away at 100 feet. For all the reasons I have stated above, there is so much error in trying to determine how high you actually are, especially when you are losing altitude rapidly while spinning, that 250 feet may not actually be enough. When I heard about that 100 foot breakaway stunt those base jumpers had done, I just shook my head and said: "You've got to be kidding!" I show the video just to demonstrate how quickly the Skyhook can get a reserve to line stretch...with the most dramatic background possible....the ground. I would breakaway below 500 feet only if I was very sure I was going to die if I didn't...a situation I hope I am never in. Hell, I get nervous deploying my main much below 3,000 feet. Remember Booth's first law: " The lower you pull, the more likely you are to have a malfunction."

[riggermick 6]

Remember Booth's first law: " The lower you pull, the more likely you are to have a malfunction."

[billbooth 10]

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Remember Booth's first law: " The lower you pull, the more likely you are to have a malfunction."

Isn't that more of an axiom than a law?

Mick.

[TaylorC 0]

Question for Bill Booth or any rigger:

I watched that video and you show the part when your on the ground you have the system hooked up to cutaway on the ground. It looked like the cutaway cable that was attached to the skyhook side was shorter.
If you have a skyhook should the cutaway cable on the side that has the skyhook hooked up be shorter than the other side?

[dorbie 0]

That was a Collins' lanyard demo only where one riser was deliberately detatched early and the other cutaway cable was pulled all the way out of the housing rather than being significantly longer except w.r.t. running accross the shoulder (it may still be slightly longer protruding from the housing, I dunno). There was no skyhook on that demo rig, just a conventional RSL + Collins' lanyard. If there'd been a skyhook the RSL would still have been attached to the freebag bridle via the skyhook at the end of the demo.

[littlejohn 0]

honestly in my opinion. people shouldn't be cutting away at 100 ft. that's a good way to get hurt. even though there is a new system for that. if you have a mal. get rid of it soon as possible don't wait.

death before dishonor