Forums: Skydiving: Safety and Training:
RSL, good or bad ?

 

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Dejavu  (D 765)

Jan 26, 2006, 10:23 AM
Post #26 of 111 (1071 views)
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Re: [stillalive] RSL, good or bad ? [In reply to] Can't Post

RSL's are good. I have seen 2 students cut away and been saved by the RSL, they did not pull the reserve hand.

The one student was unable to pull the reserve handle due to his left arm been broken due to and unstable deployment.

The other was in a Spiralling Malfunction and got disoriented. Cutaway and did not deploy the reserve handle.


kelpdiver  (B 7)

Jan 26, 2006, 4:43 PM
Post #27 of 111 (1037 views)
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Re: [tso-d_chris] RSL, good or bad ? [In reply to] Can't Post

In reply to:
Not once conservation of angular momentum is taken into consideration. Experience (and Physics) tells me that no matter how hard you arch after cutting away a spinning mal, there is still a good chance you will tumble, which can be very bad during a deployment.

Huh? Physics says that a person attached to a spinning main will fly straight away when detached from the main, due to centripital force. Just like a ball or rock attached to a line does when you swing it around your head and then release.


diablopilot  (D License)

Jan 26, 2006, 5:50 PM
Post #28 of 111 (1029 views)
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Re: [kelpdiver] RSL, good or bad ? [In reply to] Can't Post

I'm glad someone else realizes this as well.


dharma1976  (D 28634)

Jan 26, 2006, 5:51 PM
Post #29 of 111 (1029 views)
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Re: [stillalive] RSL, good or bad ? [In reply to] Can't Post

In reply to:
Anybody have an opinion whether in any specific situation an RSL worsens your status instead of helping.

Eg. suppose you have multiple line twists and are in a spin, you cut-away and your unstable, on your back or completely mal positioned. Wont that situation cause your already deploying reserve to tangle or open improperly.

If altitude permiting, wouldnt it be better to cut-away stabilize, and then pull silver on your own.

Has any one had or heard about a bad experience with RSL?

medium

Dave


JohnMitchell  (D 6462)

Jan 26, 2006, 8:09 PM
Post #30 of 111 (1016 views)
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Re: [jheadley] RSL, good or bad ? [In reply to] Can't Post

In reply to:
Jim Crouch, USPA's once told me that out of the 8 cutaways he's had, 7 of them were with traditional RSLs, and he's never had line twists on his reserve.

.
10 cutaways, about half with RSL's, no line twists ever. Never "took it down" after cutting away either, always pulled the reserve right away, never lost stability. ARCH! You'd be amazed what body position will do for you. Putting your feet on your butt will keep you head high, too. Good for a nice clean deployment.


Ron

Jan 26, 2006, 11:40 PM
Post #31 of 111 (1000 views)
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Re: [kelpdiver] RSL, good or bad ? [In reply to] Can't Post

In reply to:
Huh? Physics says that a person attached to a spinning main will fly straight away when detached from the main, due to centripital force.

They will fly away, but they could still tumble. The mass and momentum will be in a direct line, but that will not prevent a person from continuing to spin or maybe tumble.

Newtons 1st law.

And for application, I have video of me cutting away from a mal and spinning like a rag doll. I was low and did not take a delay and had line twists. Line twists are better than landing just a container, but no line twists are better.


(This post was edited by Ron on Jan 26, 2006, 11:43 PM)


rasmack  (D 647)

Jan 27, 2006, 2:14 AM
Post #32 of 111 (983 views)
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Re: [kelpdiver] RSL, good or bad ? [In reply to] Can't Post

In reply to:
Huh? Physics says that a person attached to a spinning main will fly straight away when detached from the main, due to centripital force. Just like a ball or rock attached to a line does when you swing it around your head and then release.

Only partially correct, as a person is not a point mass (at least I'm not Wink). If you are spinning at say one revolution per second, you will continue to do so until a torque is applied (by your reserve).


Premier skydiverek  (C 41769)

Jan 27, 2006, 2:25 AM
Post #33 of 111 (980 views)
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Re: [Ron] RSL, good or bad ? [In reply to] Can't Post

In reply to:
I have video of me cutting away from a mal and spinning like a rag doll. I was low and did not take a delay and had line twists. Line twists are better than landing just a container, but no line twists are better.

Could you post it here? I would love to see that!


kelpdiver  (B 7)

Jan 27, 2006, 5:10 AM
Post #34 of 111 (966 views)
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Re: [rasmack] RSL, good or bad ? [In reply to] Can't Post

In reply to:
Only partially correct, as a person is not a point mass (at least I'm not Wink). If you are spinning at say one revolution per second, you will continue to do so until a torque is applied (by your reserve).

That would depend on the nature of your spin. If you're getting rotated about by your main, your body itself may be staying pretty constant relative to the canopy. Remove the lines, and straight off you fly. Very different from you flat spinning.

Some of these canopy mals are very dynamic, so I can't imagine the variety of forces and rotations the body would undergo.


Ron

Jan 27, 2006, 8:13 AM
Post #35 of 111 (945 views)
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Re: [skydiverek] RSL, good or bad ? [In reply to] Can't Post

In reply to:
Could you post it here? I would love to see that!

Sorry, to be honest I have no idea how to even start doing that.


Ron

Jan 27, 2006, 8:21 AM
Post #36 of 111 (946 views)
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Re: [kelpdiver] RSL, good or bad ? [In reply to] Can't Post

In reply to:
That would depend on the nature of your spin. If you're getting rotated about by your main, your body itself may be staying pretty constant relative to the canopy. Remove the lines, and straight off you fly. Very different from you flat spinning.

Except you keep forgetting about drag. Your example of a rock on a line is cool and all, but rocks don't have arms or legs. These arms and legs are going to cause drag that will try to either make a skydiver belly to earth, if in an arch, or back to earth if fetal.

So in your theory that a cutaway will throw a jumper directly away from the axis of rotation would be great....Except, that would mean in a perfect standing position. And as soon as you are free from the main, I very much doubt you could maintain that position and maintain stable in a standing position going feet first away from the axis of rotation.

In reply to:
Some of these canopy mals are very dynamic, so I can't imagine the variety of forces and rotations the body would undergo.

I have 6 mals and only once was I ever perfectly stable after the cutaway, and that was from a stable but uncontrolable mal. BTW on that jump I had line twists on the reserve also. So I can imagine the forces.


(This post was edited by Ron on Jan 27, 2006, 8:31 AM)


AFFI  (D 25538)

Jan 27, 2006, 9:02 AM
Post #37 of 111 (934 views)
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Re: [Ron] RSL, good or bad ? [In reply to] Can't Post

Many years ago I was dealing with Line Twist on my main and did not remain altitude aware, when I finally decided to cut the mess away I feared I had gotten to low but still was not altitude aware and cut away and deployed the reserve as fast as I could. The result was line twists on the reserve (pic attached) due to instability at reserve deployment time BUT had I waited to get stable first I would not be here typing this now, according to people watching on the ground I was already too low. I got low because I was not altitude aware; had I waited even a few seconds after cutting away to get stable or if I had trouble locating my reserve deployment handle I quite likely would not have survived. An RSL would have been a life saver had I not been able to deploy my reserve in this circumstance.

There are a few families this past year who wish the skydiving member of the family who cutaway too low and died was using an RSL...

The USPA recommends that all experienced jumpers utilize an RSL unless they have a compelling reason not to (CRW, Wingsuits, ect).


(This post was edited by AFFI on Jan 27, 2006, 9:50 AM)
Attachments: ResreveLineTwists.jpg (10.2 KB)


tso-d_chris

Jan 27, 2006, 9:20 AM
Post #38 of 111 (929 views)
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Re: [kelpdiver] RSL, good or bad ? [In reply to] Can't Post

In reply to:
In reply to:
Not once conservation of angular momentum is taken into consideration. Experience (and Physics) tells me that no matter how hard you arch after cutting away a spinning mal, there is still a good chance you will tumble, which can be very bad during a deployment.

Huh? Physics says that a person attached to a spinning main will fly straight away when detached from the main, due to centripital force. Just like a ball or rock attached to a line does when you swing it around your head and then release.

I believe you are referring to centrifugal force.

The spinning mal has a certain angular momentum. Immediately following the cutaway, the jumper and the canopy separate, and the jumper is thrown away along the tangent line of the previous arc of rotation. However, the angular momentum is conserved, split between the jumper and the canopy.

Experience tells me that the jumpers new axis of rotation is orthogonal to the axis of rotation of the original spinning malfunction, but I don't have the equation at the moment to verify or disprove this, only experience from cutting away from several spinning malfunctions.

There are, of course, other factors involved, such as drag. I'm not sure how large a role it plays, but that effect will increase with the square of the jumpers velocity at time of cutaway.


Ron

Jan 27, 2006, 10:29 AM
Post #39 of 111 (914 views)
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Re: [AFFI] RSL, good or bad ? [In reply to] Can't Post

In reply to:
An RSL would have been a life saver had I not been able to deploy my reserve in this circumstance.

There are a few families this past year who wish the skydiving member of the family who cutaway too low and died was using an RSL...

On the flip side, your experience shows that those same families would have been happy if the jumper had CORRECTLY performed the emergency procedures.

Instead of putting the focus on getting new toys that can cause problems...How about we focus on training to prevent someone from cutting away and not pulling the reserve? Remember the is one family this year that migth have been happy if the jumper DID NOT have an RSL.

After they have the emergency procedures practiced and trained. THEN add an RSL if they want as an added step, not a replacement for training and practice.


Premier wmw999  (D 6296)

Jan 27, 2006, 10:40 AM
Post #40 of 111 (907 views)
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Re: [Ron] RSL, good or bad ? [In reply to] Can't Post

Quote:
Remember the is one family this year that migth have been happy if the jumper DID NOT have an RSL
One thing to remember is that the person who might have had the RSL contribute to his death was a student. He would, under any circumstances, have an RSL. Few would disagree with that.

That said, it's hard to disagree with more training. It's stupid to substitute RSLs for adequate training, including hanging harness. But I will say that when you're talking about people who look for a medicine to fix whatever is wrong with them, and an easy eat-everything-you-want diet that lets them lose weight, or who want to downsize NOW because Johnny did, it's hard to imagine a more likely thing to happen.

Maybe we should go back to rounds. Then you'd really have to want to skydive Sly

Wendy W.


AFFI  (D 25538)

Jan 27, 2006, 4:44 PM
Post #41 of 111 (880 views)
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Re: [Ron] RSL, good or bad ? [In reply to] Can't Post

In reply to:
On the flip side, your experience shows that those same families would have been happy if the jumper had CORRECTLY performed the emergency procedures.

Instead of putting the focus on getting new toys that can cause problems...How about we focus on training to prevent someone from cutting away and not pulling the reserve?

I could not agree with Ron more but the unfortunate truth of the matter is that many skydivers do not put survival as the top priority, most put safety secondary to the bad ass stuff they can do in freefall and the awesome swoops they can make in front of the awe inspiring cheers and admiration of spectators not to mention how cool it looks to have pillows on both sides while operating a canopy one is not ready for.

It is not about promoting extra aspects of our gear as part of the equation, but rather making up for the apathy of a good percentage of the individuals currently participating in skydiving illustrates these days.

As unfortunate a perspective as this might seem like, IMHO it is an accurate one.


Ron

Jan 27, 2006, 8:38 PM
Post #42 of 111 (867 views)
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Re: [AFFI] RSL, good or bad ? [In reply to] Can't Post

In reply to:
I could not agree with Ron more but the unfortunate truth of the matter is that many skydivers do not put survival as the top priority, most put safety secondary to the bad ass stuff they can do in freefall and the awesome swoops they can make in front of the awe inspiring cheers and admiration of spectators not to mention how cool it looks to have pillows on both sides while operating a canopy one is not ready for.

It is not about promoting extra aspects of our gear as part of the equation, but rather making up for the apathy of a good percentage of the individuals currently participating in skydiving illustrates these days.

While I think you are correct in your thoughts....That does not make it ok to forget about trying to do things the right way.

Dylan Thomas.....I think you know what I mean.


JohnMitchell  (D 6462)

Jan 28, 2006, 9:30 AM
Post #43 of 111 (835 views)
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Re: [Ron] RSL, good or bad ? [In reply to] Can't Post

In reply to:
And for application, I have video of me cutting away from a mal and spinning like a rag doll. I was low and did not take a delay and had line twists.
What was the loading on that reserve? The reason I ask is that I've heard a properly loaded reserve will fly straight with line twists, while a too heavily loaded reserve can spin up and in like a Stiletto or worse. Maybe it's another reason to not make your last chance the smallest canopy you got.


Ron

Jan 28, 2006, 4:32 PM
Post #44 of 111 (802 views)
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Re: [JohnMitchell] RSL, good or bad ? [In reply to] Can't Post

In reply to:
What was the loading on that reserve? The reason I ask is that I've heard a properly loaded reserve will fly straight with line twists, while a too heavily loaded reserve can spin up and in like a Stiletto or worse. Maybe it's another reason to not make your last chance the smallest canopy you got.

The line twists were not spinning the canopy. The canopy flew perfectly straight ahead, but *I* was spinning under it.

Twice that has happend to me, and not once has my PD113 even thought about turning.


billbooth  (D 3546)

Jan 28, 2006, 4:58 PM
Post #45 of 111 (799 views)
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Re: [NelKel] RSL, good or bad ? [In reply to] Can't Post

In reply to:
The misunderstanding that an RSL deployment from a spining malfunction is common. The fact is that line twists in that situction are most often caused by the jumper struggling to get belly to earth while deploying the reserve.<<<

Exactly! Wink
I do not currently use an RSL, but had one on my first rig. I have had 2 cutaways. My first was a sport rig with out an RSL from a spinning linetwist. I did EP's one hand on each handle. No reserve problems. The second was on a Sigma Tandem, that RSL/Skyhook is fast! It felt as thought the reserve canopy was surging forward and backward for the first few seconds of inflation. Kinda like it deployed faster than it could inflate.

Two points:

1. The very deep ("rock and roll", "tail-below-the-nose") brake setting on RWS 360 tandem reserves, along with other design features, was the only way we could insure these canopies could open "softly" at tandem terminal (170 mph) Remember, your tandem reserve has no drogue. It has worked well for over 20 years on thousands of canopies.

2. Line twists are not a big problem on most reserve opening situations. However, if you have line twists AND unequal line lengths, caused by an unstable body position (body not aligned properly into the relative wind) then you could have a serious problem. Unequal line lengths, caused by one shoulder being "lower" than the other, when added to several line twists, cause by the bag being pulled "sideways" out of your reserve container, could cause an unrecoverable spin (just like the one you probably just broke away from). The chance of this happening on your reserve depends on the shape and wing loading of your reserve canopy. If reserves keep getting smaller, and take on higher performance elliptical shapes, this will become more and more likely.

The reason I went through this rather long winded explanation, was to point out the difference between breaking away from a spinner with a "normal" RSL, and with a Skyhook. While the normal RSL will allow the pilot chute to deploy your reserve canopy "into the relative wind" and possibly "across" your body, causing unequal ine lengths, AND line twists, as the reserve comes out of the bag, the Skyhook "places" your reserve right where your main was 1/2 a second earlier, or exactly in-line with the vertical axis of your body, greatly lessening the possibility of both line twists and unequal line lengths.


JohnMitchell  (D 6462)

Jan 28, 2006, 7:14 PM
Post #46 of 111 (787 views)
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Re: [billbooth] RSL, good or bad ? [In reply to] Can't Post

In reply to:
The chance of this happening on your reserve depends on the shape and wing loading of your reserve canopy. If reserves keep getting smaller, and take on higher performance elliptical shapes, this will become more and more likely.
That's exactly what I was wondering about. I wonder how many people are considering that scenario when they choose a reserve?


chachi  (B 3406)

Jan 31, 2006, 2:10 PM
Post #47 of 111 (728 views)
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Re: [JohnMitchell] RSL, good or bad ? [In reply to] Can't Post

who cares if you get line twists on your big square docile canopy. you will certainly be able to kick out. rsl or skyhook i think is suitable for anyone that does not jump a camera.


JohnMitchell  (D 6462)

Feb 1, 2006, 7:19 AM
Post #48 of 111 (692 views)
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Re: [chachi] RSL, good or bad ? [In reply to] Can't Post

In reply to:
who cares if you get line twists on your big square docile canopy. you will certainly be able to kick out. rsl or skyhook i think is suitable for anyone that does not jump a camera.
Yep, that's what I think, too. I jump an RSL. I just wonder why anyone would want a reserve that might spin up on them, or that you have to be perfectly stable for it to be reliable.


tso-d_chris

Feb 1, 2006, 7:31 AM
Post #49 of 111 (688 views)
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Re: [chachi] RSL, good or bad ? [In reply to] Can't Post

In reply to:
who cares if you get line twists on your big square docile canopy. you will certainly be able to kick out. rsl or skyhook i think is suitable for anyone that does not jump a camera.

For those that make the smart decision to jump with a big, docile reserve canopy, that is good advice in most cases. Not so straight forward is when the jumper loads his reserve very heavily.

There is no substitute for proper execution of emergency procedures.


tso-d_chris

Feb 1, 2006, 7:37 AM
Post #50 of 111 (688 views)
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Re: [JohnMitchell] RSL, good or bad ? [In reply to] Can't Post

In reply to:
I just wonder why anyone would want a reserve that might spin up on them, or that you have to be perfectly stable for it to be reliable.

I think it has more to do with the fact that there are so few containers available for anyone who wants a small, zippy main and a sanely sized reserve.


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