RSL

[chuckakers 370]

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Not true. Your cutaway cables are designed to release both 3-rings at the same time when you cut away.

Slowly pull the cutaway cable on a (single-side) rsl equipped rig - disconnect the rsl first LOL - and see what happens.

No one pulls their cutaway cable slowly during a mal...the only time it matters.

Chuck Akers
D-10855
Houston, TX

[chuckakers 370]

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Not true. Your cutaway cables are designed to release both 3-rings at the same time when you cut away.

Counter-rebutted:

Direct from the horses mouth

Yes, it was straight from the horse's mouth. And as I said, during a mal the pull is so fast relative to a measly 2 inch difference in cable length make virtually no difference...

"In truth, the 2" differential really doesn't matter...." Bill Booth

In other words...

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?do=post_view_threaded;post=4187022;sb=post_latest_reply;so=ASC;

backatcha

Chuck Akers
D-10855
Houston, TX

[sundevil777 93]

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Not true. Your cutaway cables are designed to release both 3-rings at the same time when you cut away.

Slowly pull the cutaway cable on a (single-side) rsl equipped rig - disconnect the rsl first LOL - and see what happens.

No one pulls their cutaway cable slowly during a mal...the only time it matters.

No one should, and no one should stop pulling when one side releases, but some do.

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

[billvon 2,400]

>No one pulls their cutaway cable slowly during a mal..

No, but some people pull until they feel something happen, then stop. In that case it is very advantageous to make sure the non-RSL side releases first.

[JohnSherman 1]

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"In truth, the 2" differential really doesn't matter...." Bill Booth

It wouldn't matter if that was all there was. But there is more within the compression of the long housing. That housing can compress as much as 6 to 8 inches if the cable is unlubed and the loop is tight holding the cable at the riser. I have had it happen to me in the air. This means that even with the cutting differential quoted, the difference would be inadiquet to prevent the right side from releasing if the left side locks up. Reserve out Main in tow.

[Anvilbrother 0]

In a cutaway forces are usually high along with speed. So even if you do cutaway fast that 1-2 inches minimum that you say doesn't matter might mean .25 o r.5 or 1 second delay giving the non rsl side time to release first

Postes r made from an iPad or iPhone. Spelling and gramhair mistakes guaranteed move along,

[nigel99 143]

Thanks John. I learn't quite a bit from your link and post.

Experienced jumper - someone who has made mistakes more often than I have and lived.

[chuckakers 370]

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>No one pulls their cutaway cable slowly during a mal..

No, but some people pull until they feel something happen, then stop....

Well now that would be stupid.

Chuck Akers
D-10855
Houston, TX

[chuckakers 370]

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"In truth, the 2" differential really doesn't matter...." Bill Booth

It wouldn't matter if that was all there was. But there is more within the compression of the long housing. That housing can compress as much as 6 to 8 inches if the cable is unlubed and the loop is tight holding the cable at the riser. I have had it happen to me in the air. This means that even with the cutting differential quoted, the difference would be inadiquet to prevent the right side from releasing if the left side locks up. Reserve out Main in tow.

I agree on both points of your points. 1.) a 2 inch difference in cable length is by itself meaningless under normal operating conditions, and 2.) all manufacturers should consider using non-compressible cable housings.

Chuck Akers
D-10855
Houston, TX

[chuckakers 370]

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In a cutaway forces are usually high along with speed. So even if you do cutaway fast that 1-2 inches minimum that you say doesn't matter might mean .25 o r.5 or 1 second delay giving the non rsl side time to release first

I disagree and so does Bill Booth. He did the math in a previous reply and came up with a delay figure during a real-world cutaway of 1/30 of a second, and said that calculation was using a pull speed that is actually slower than he estimated a person would actually make.

Converting that - we're talking about a .03 second delay OR LESS. That's a mere third of a tenth of a second. Clearly not enough of a delay to make a bit of difference in the "RSL side releases first by design" argument.

Chuck Akers
D-10855
Houston, TX

[billvon 2,400]

>Well now that would be stupid.

Yep. But, sadly, some people don't always do the smart thing. I saw this happen to a student once about fifteen years ago; he spun for 15-20 seconds under a single riser while he apparently tried to figure out what had just happened. The instructor on radio was hollering at him, but I think he was yelling so loud that it wasn't being received intelligibly. Fortunately the student went back and pulled the cutaway handle the rest of the way before pulling the reserve. If he pulled the reserve at all, that is; it was still in its pocket, although he mentioned something about putting it back in the pocket afterwards. Actually it was sort of hard to get a straight story out of him because he was upset.

[chuckakers 370]

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>Well now that would be stupid.

Yep. But, sadly, some people don't always do the smart thing. I saw this happen to a student once about fifteen years ago; he spun for 15-20 seconds under a single riser while he apparently tried to figure out what had just happened. The instructor on radio was hollering at him, but I think he was yelling so loud that it wasn't being received intelligibly. Fortunately the student went back and pulled the cutaway handle the rest of the way before pulling the reserve. If he pulled the reserve at all, that is; it was still in its pocket, although he mentioned something about putting it back in the pocket afterwards. Actually it was sort of hard to get a straight story out of him because he was upset.

You are very correct on that, Bill.

On another note, Your story actually brings the conversation full circle. If the risers had released at the same moment, the person you speak of would not have been in that situation in the first place.

Maybe designing the cutaway system to release the RSL-equipped riser first (which I still argue doesn't make a hill of beans difference if the cutaway is performed properly) isn't such a good idea after all.

Chuck Akers
D-10855
Houston, TX

[billvon 2,400]

>If the risers had released at the same moment, the person you speak of
>would not have been in that situation in the first place.

Agreed. But that is nearly impossible since the tolerances involved do not allow a guaranteed simultaneous release. So given that one is going to release sooner anyway, in general the non-RSL side is a good choice.

[chuckakers 370]

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>If the risers had released at the same moment, the person you speak of
>would not have been in that situation in the first place.

Agreed. But that is nearly impossible since the tolerances involved do not allow a guaranteed simultaneous release. So given that one is going to release sooner anyway, in general the non-RSL side is a good choice.

Agreed, but if the system was designed to release simultaneously, the chance of it happening that way is pretty much guaranteed to be better than if it's designed not to.

Gotta admit, this a terrific learning discussion for everyone. At least everyone willing to discuss it without their pride getting in the way.

You bring a lot of wise thoughts to the table, my man.

Hey kids, listen to the discussion. It might just save your butt.

Chuck Akers
D-10855
Houston, TX

[KCJumper 0]

Maybe i'm wrong in my thinking but when I think about the difference in cable length I always thought it was for the accidental dislodging of a handle. That way if one riser became disconnected it would be the non-RSL side.

[billvon 2,400]

>Agreed, but if the system was designed to release simultaneously, the
>chance of it happening that way is pretty much guaranteed to be better
>than if it's designed not to.

Do you think it would ever be much higher than zero?

There are so many tolerances in the system that I think trying to match them all will simply never work. One riser will always release first once you pull the handle to some specified length. If you _don't_ trim the cables so that the RSL side releases last, then the challenge becomes having them release close enough in time that the reserve does not begin deploying until the other side releases. What is that time? 100 milliseconds? 250 milliseconds? Does that mean you have to pull at a speed of 10 feet per second? If you have a hard pull and need to try twice to get the second riser cut away - which riser do you want still connected? How does the timing/forces/sequence change when you are under a spinner pulling 3 G's, and your harness is all stretched out? What if it's a low drag mal and there's _no_ force on the harness? What if you pull the handle sideways because your harness is all catty-wampus from a spinner?

All of that is very hard to quantify, which, I think, is why trimming the cables in a standard system to guarantee one side releases first is a good idea.

Jump Shack's approach is a system that does not pull the reserve cable until both sides disconnect. While that system has its own problems, it does make the system agnostic as to which side releases first.

The Collins lanyard is another approach; it guarantees that the 'other' riser cuts away once the first one does.

Both of these systems add some complexity and hidden failure modes, and so one could make arguments both ways.

[chuckakers 370]

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>Agreed, but if the system was designed to release simultaneously, the
>chance of it happening that way is pretty much guaranteed to be better
>than if it's designed not to.

Do you think it would ever be much higher than zero?

There are so many tolerances in the system that I think trying to match them all will simply never work. One riser will always release first once you pull the handle to some specified length. If you _don't_ trim the cables so that the RSL side releases last, then the challenge becomes having them release close enough in time that the reserve does not begin deploying until the other side releases. What is that time? 100 milliseconds? 250 milliseconds? Does that mean you have to pull at a speed of 10 feet per second? If you have a hard pull and need to try twice to get the second riser cut away - which riser do you want still connected? How does the timing/forces/sequence change when you are under a spinner pulling 3 G's, and your harness is all stretched out? What if it's a low drag mal and there's _no_ force on the harness? What if you pull the handle sideways because your harness is all catty-wampus from a spinner?

All of that is very hard to quantify, which, I think, is why trimming the cables in a standard system to guarantee one side releases first is a good idea.

Jump Shack's approach is a system that does not pull the reserve cable until both sides disconnect. While that system has its own problems, it does make the system agnostic as to which side releases first.

The Collins lanyard is another approach; it guarantees that the 'other' riser cuts away once the first one does.

Both of these systems add some complexity and hidden failure modes, and so one could make arguments both ways.

I agree with your comments. Just a bit of advocacy for the devil on my part.

In the context of this conversation, it seems the most bulletproof systems would be the Racer style dual RSL (two-out main canopy cocooning aside) and the Collins lanyard.

Nitpicking a bit here, though. Would a sideways pull make any difference? You'll have to enlighten me on that one.

Chuck Akers
D-10855
Houston, TX

[JohnSherman 1]

Try as I may we just can't get them to release evenly every time. The best we can do is guarantee release within 2 inches every time, which we do! To do that it requires housings which have minimum compression. No such thing as Zero.

We control our housing length by dimension and cut our cable length also to dimension, never relative, as the amount of compression is unknown. Like trying to even the table legs. I think the reason we want this is: "if one side goes both sides should go, if one side stays both sides should stay". It is easier to release two sides than one side under the total load.

Therefore we must have a slick release cable cause it is always the loop load which hangs them up. There I’ve said it, have fun with it.

[Deyan 31]

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In the context of this conversation, it seems the most bulletproof systems would be the Racer style dual RSL (two-out main canopy cocooning aside) and the Collins lanyard.

Check the LOR 2 from Parachutes de France. I can't upload the manual,but here is a picture of the system if you haven't seen one.

Blue skies

"My belief is that once the doctor whacks you on the butt, all guarantees are off" Jerry Baumchen

[gowlerk 1,912]

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Check the LOR 2 from Parachutes de France. I can't upload the manual,but here is a picture of the system if you haven't seen one.

So.....that picture is not that good, but it seems to show two RSLs, one on each riser, with two separate pins, in two separate loops, correct? If so, I wonder how well the various AAD cutters work on that? I wonder if the pins can interfere with each other? Sometimes the cure is worse than the disease, but I'll never be a rig designer, just a mere question asker!

Ken

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[chuckakers 370]

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Try as I may we just can't get them to release evenly every time. The best we can do is guarantee release within 2 inches every time, which we do! To do that it requires housings which have minimum compression. No such thing as Zero.

We control our housing length by dimension and cut our cable length also to dimension, never relative, as the amount of compression is unknown. Like trying to even the table legs. I think the reason we want this is: "if one side goes both sides should go, if one side stays both sides should stay". It is easier to release two sides than one side under the total load.

Therefore we must have a slick release cable cause it is always the loop load which hangs them up. There I’ve said it, have fun with it.

John, my wife jumps a Racer (circa 1998, no RSL) and she has been very satisfied with it. I really appreciate your contribution to this thread and I'm learning (yes, learning after 26 years in the sport) a lot from your's and Bill Booth's posts on this issue.

Just out of curiosity....

The single-handle cutaway system works about as well as you guys can tweak it to. However, it sounds like a perfectly simultaneous release (whether all that important or not in context) is something that has eluded all you genius rig building guys.

Have you thought about shifting the paradigm by developing a single-point chop? Speaking from a completely uneducated perspective, how about a system that uses a single cable extraction point to release both 3-rings. I can't really explain the design, but my thought is a system that uses a single point for the 3-ring activation on both sides rather than a single point handle configuration with dual cables.

I know it sounds a bit looney, but you rig builder guys seem to have a vision that might just help the idea make sense.

Thoughts?

Chuck Akers
D-10855
Houston, TX

[P-dro 0]

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So.....that picture is not that good, but it seems to show two RSLs, one on each riser, with two separate pins, in two separate loops, correct?

Correct

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If so, I wonder how well the various AAD cutters work on that?

Cypres has a specific 2 pin container cutter, but I don't know the differences with the 1 pin cutter.

[likestojump 3]

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So.....that picture is not that good, but it seems to show two RSLs, one on each riser, with two separate pins, in two separate loops, correct?

Correct

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If so, I wonder how well the various AAD cutters work on that?

Cypres has a specific 2 pin container cutter, but I don't know the differences with the 1 pin cutter.

the manual specifies fingertrapping the two closing loops into one line, which would mean to use a single cutter for the single closing loop with two heads.

[JohnSherman 1]

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Check the LOR 2 from Parachutes de France.

The problem with the LOR is the same as any single sidded system. One side can release without the other. Consentrating the release forces to the unreleased side. The cross connector keeps thes forces more even when only one side releases.

As to Chucks suggestion about a new approach. I wish!! The problem comes back to flexiable components and the housing compression. Every system needs housings and we are doing the state of the art in housings. The 2 inches slop I have now is all in the long side housing.

John

[Deyan 31]

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So.....that picture is not that good, but it seems to show two RSLs, one on each riser, with two separate pins, in two separate loops, correct? If so, I wonder how well the various AAD cutters work on that? I wonder if the pins can interfere with each other?

Yeah, sorry for the bad picture, but you've got the idea.

The two loops are from a small diameter line and they both go trough a single cutter. The standard CYPRES line is 2.3 mm when fingertraped. The small diameter line for LOR loop is only 1.5 mm. So two loops will have just a bit more flesh for cutting.

I can' talk about other cutters, but I've seen CYPRES cutter to make a clean cut on 2 loops from the standard line with no tension on the loops, so I think that with the small diameter line the outcome will be the same.

As for "pins interfere with each other", I've never heard about that happened somewhere......but that doesn't mean that it never happened or it will not happen.

Blue skies

"My belief is that once the doctor whacks you on the butt, all guarantees are off" Jerry Baumchen