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2 stage reserve ?

 

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Snowflake

Mar 26, 2002, 12:20 AM
Post #1 of 26 (1774 views)
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2 stage reserve ? Can't Post

If Atair can make a Canopy that can stand up to a headdown deployment. Why isn't there a 2 stage reserve that can also do the same thing?????

JG


Premier Remster  (C License)

Mar 26, 2002, 1:18 AM
Post #2 of 26 (1756 views)
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I'm sure it could be made, but I'm not sure I'd want one.... can you imagine a slow opening reserve????

Remster
Muff 914


kwmontreal  (D 25906)

Mar 26, 2002, 4:48 AM
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Ditto to Rem's post. Can you Iimagine..." sh*t I can't clear this..... what 900ft already!!".


Jump Safe

KW



Snowflake

Mar 26, 2002, 6:33 AM
Post #4 of 26 (1722 views)
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Well duh......This is a clear case of why one shouldn't post late at night and drunk....thats my excuse and I'm sticking with it

JG


councilman24  (D 8631)

Mar 26, 2002, 7:02 AM
Post #5 of 26 (1713 views)
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There is a round reserve, the Preserve V that is intended for both high speed, high load deployments and low speed, low load deployments. It uses PC controlled break ties at the skirt. Both the high speed and low altititude low speed deployment video is impressive. I've sold a couple of these to heavier pilot customers. Ram airs may have trouble with meeting all of the criteria but a round using a system like this adapted for sport use might work. The thing they had the most trouble with was blowing up PC's. They eventually had to design a matching high strength PC. Integrating a canopy like this would probably require a dedicated harness/container system. I assume some one is working on this whether with a round or square.



billbooth  (D 3546)

Mar 26, 2002, 7:31 AM
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     16 years ago Bill Coe and I figured out how to make Vector tandem reserves open soft enough at tandem terminal (170 mph) to avoid injuring even the proverbial 87 year old grandmother. So why can't you buy a sport reserve that opens softly at head down speeds? Simple, because of current TSO rules, no one call sell a reserve that won't open completely within 3 seconds after a breakaway. Without complicated reefing devices like pyrotechnic cutters, no canopy can open in 3 seconds at 30 mph and not "kill" you at 170 mph. It's simply a case of the rules being way behind the state of the art.

What to do: Change the rules like we did for tandem reserves. Bill Coe and I are on the committee that is revising the current TSO, and Bill is championing, over some opposition, a rule change that will allow longer opening times on a special class of reserves specifically made for the higher speed disciplines.

However, if you jump one of these reserves in the future, you are going to have to up your pull altitudes by a factor of 2, get a tandem Cypres, and really hope that you never have a canopy collision that requires a low/slow breakaway.




polarbear  (D 25673)

Mar 26, 2002, 7:51 AM
Post #7 of 26 (1689 views)
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Interesting notion...yet another variable in the equation of what gear to buy! I suppose something like this could have its nitch.



riggerrob  (D 14840)

Mar 26, 2002, 10:48 AM
Post #8 of 26 (1645 views)
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As an addition to Bill Booth's post, back in the early 1980s, Manley Butler did a series of test drops at NAWS China Lake to prove that square canopies could be safely deployed from ejection seats. To limit opening shock during these high speed deployments, they installed two or three reefing ropes, in addition to the regular sail slider. They used a complex series of cutters (similar to Cypres cutters) to cut the reefing ropes at various times.
To make reefing ropes work in a skydiving scenario, you would need airspeed sensors and a computer to tell the cutters when to cut.
It is possible to build a reserve - using existing technology - that will satisfy both the high speed and low speed edges of the envelope. The problem is that it would be very expensive and very bulky. The other problem is that complexity might drive it beyond the abilities of amateur riggers. It would certainly have the full-time riggers scratching their heads and staring at the manual!



Martini  (D 23756)

Mar 26, 2002, 3:45 PM
Post #9 of 26 (1611 views)
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So all you genius manufacturers and riggers out there are telling me that a reserve can't be built with inverse opening speed to airspeed properties? I'll bet that a bunch of ordinary skydivers with enough beer could come up with a dozen decent ideas in one evening, one or two of which might even be practical. Fuggetabout complex reefing/timing/pyrotechnic devices, we're talking reserve here. Keep it simple or it aint gonna fly. Yep, going really fast really low still requires special treatment too. Do I have concepts? Depends; who's buying the beer?



Premier PhreeZone  (D License)
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Mar 26, 2002, 4:08 PM
Post #10 of 26 (1606 views)
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Problem is that it is an inverse relationship. More speed leads to faster/harder openings. Try and dump in a full head down or stand once and see how quickly the relationship is realized. I'm jumping a canopy that is staged and I'll dump in a sit everyonce and a while to just have some kicks. The openings are MUCH harder and faster.
I'm sure that there are designs that will open really slowly from a high speed but how is that going to help in a slow speed cutaway at 900 feet? Is it going to require a long distance to inflate from a cutway? If so thats going to be a few fatilities untill the lessons are learned. Its getting a reserve that will meet the TSO, the ablitiy to go super high speed/open slow and low speed/open fast that I think is the Holy Grail of reserves....

I wish you would step back from that ledge my friend... ~3EB


Premier billvon  (D 16479)
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Mar 26, 2002, 4:30 PM
Post #11 of 26 (1598 views)
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>To make reefing ropes work in a skydiving scenario, you would need airspeed
>sensors and a computer to tell the cutters when to cut.

I posted something on here a while back that would allow you to do this pretty simply. Have two brake settings on a reserve - one for high speed openings, one for low speed openings. Put an extra white brake-stow loop on the reserve riser, and stow both sets of brake settings on the toggle. In this position, the reserve is set for a normal low-speed opening (i.e. it will open quickly.) Releasing the brakes releases both brake setpoints.

Now, take the extra output on a cypres and connect it to two cutters that will cut the low-speed brake-stow loop. Once this happens, the reserve is set for a high speed (i.e. more reefed) opening. The Cypres, if it detects a speed >150kts and an altitude of <1000 feet, fires all three cutters - the two riser cutters and the reserve closing loop cutter. This gives you a safe reserve opening if you remain head down and have a cypres firing.

To get it to do that during an accidental deployment is tougher. Simplest way I could see would be a light sensor on the Cypres control unit. If the sensor suddenly sees sunlight (indicating the freebag has left) and you're above 1000 feet and >150 knots, fire the riser cutters only.

-bill von


Martini  (D 23756)

Mar 26, 2002, 4:37 PM
Post #12 of 26 (1594 views)
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The inverse relationship I was referring to is in fact fast airspeed = slow opening and slow airspeed = fast opening. Yes this is, or should be, the holy grail of reserve openings unless you are at high airspeed and also low altitude; you need a fast opening here regardless of airspeed. This is the only exception I can see to the "ideal" reserve, and it would require a special AAD setup. Otherwise I think that a reserve can be built to open inversely using relatively ordinary principles/materials. But now that I think of it the dependency on electronic devices if I need a canopy while fast and low isn't something I would allow in my own rig, so I guess I'll stick with simple technology that gives me a reserve opening that's fast and reliable. Now if we can just get rid of those damn rubber bands........



AndyMan  (D 25698)

Mar 26, 2002, 5:50 PM
Post #13 of 26 (1582 views)
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Is there not something you could do with the slider?

Somehow get the slider to stay up until a certain airspeed?

_Am

ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
AIM: andrewdmetcalfe
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riggerrob  (D 14840)

Mar 27, 2002, 6:56 AM
Post #14 of 26 (1535 views)
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Good point Anyman,
About a month ago, I thought about tying the slider to the bottom skin and using a Cypres cutter to release it. But I also thought that it might be a patentable idea, so I kept my mouth shut. The only disadvantage with that is that the slider reefed canopy would expose more bottom skin to the wind than a rope-reefed canopy.
Something else for the engineers to figure out would be figuring out where to tie the slider to the canopy. One tie in the center would be simplest and most reliable, however, that would not control the position of the slider grommets relative to the bottom skin. You might need to tie each slider grommet to the bottom skin to get consistent openings.
Manley Butler, are you listening?




Premier billvon  (D 16479)
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Mar 27, 2002, 9:53 AM
Post #15 of 26 (1510 views)
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>Is there not something you could do with the slider?
>Somehow get the slider to stay up until a certain airspeed?

Anything that's attached to the canopy either requires wires running up into the canopy (reliability problem) or an extra set of reefing lines going down to the rig. I wouldn't want to actually attach the slider to anything because of the massive problems with mals that could cause.

>About a month ago, I thought about tying the slider to the bottom skin and using
>a Cypres cutter to release it.

The thought of having a reserve malfunction because your Cypres (or whatever) batteries are low is pretty scary. I think any solution has to be fail safe - if nothing electronic works, the canopy still opens normally in either its high speed or low speed reefing modes.

-bill von


billbooth  (D 3546)

Mar 27, 2002, 11:18 AM
Post #16 of 26 (1503 views)
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Bill:
Pyrotechnic reefing line cutters hooked to barometric speed and altitude sensors are what make zero/zero ejection seats possible. These parachute systems are expected to function from zero altitude/zero airspeed (with ballistic deployment and skirt-spreader guns), all the way up to Mach 1. However, the initial cost and subsequent maintenance of such systems would break the budget of any skydiver I know.
I'm not saying that this is an impossible problem to solve. But to do it cheaply, with no reduction in deployment reliability, is a hard nut to crack. But believe me, it is being worked on at this very moment. Any ideas from any readers will be listened to and appreciated.
I believe that tying the slider to the canopy, and releasing it with pyrotechnic cutter adds too much cost and complexity to be truly safe. A simpler method must be found.
For instance, our tandem reserve canopies are reefed so that only the center cell opens immediately, forming a large drogue, but the slider will not start down the lines, nor any other cells open, until the tandem pair decelerates to around 90 mph, even if initial deployment velocity is 170 mph. We accomplished this through the relationship of slider size vs cell size, and a unique cross-porting system. Sport reserves could be set up like this, but they would not pass the 3 second test at low speed. This is one of the reasons I made tandem opening altitudes higher.



Engovatov

Mar 27, 2002, 12:11 PM
Post #17 of 26 (1492 views)
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> Any ideas from any readers will be listened to and appreciated.

I mentioned some time ago one idea - would be interesting to know what is your opinion on that..

If I understand correctly, the problem is not with the reserve withstanding the opening shock: it can be reinforced, but with the user's back being broken.

Somewhat similar problem in ice and aid climbing occurs:thought there it is not the integrity of the back - taken care by the dynamic ropes - but the brittle protection. One solution is the use of shock absorbing webbing (like http://www.yatesgear.com/climbing/screamer/screamer.htm ). Can it be incorporated into harness/risers? Unsymmetrical activation maybe an issue, but it maybe solved by a following system: have the main riser bent into a bite and shortened by a replacable shock absorbent sling, that is attached with some sort of a release system.. so when activated non-symmetrically, it can be then released and the full riser extended.
Combined with a better material for lines (why did they switch from dacron - is not it a good shock absorber, used for this purpose on BASE rigs?) it will not slow down extreme opening, but may absorb the shock energy in the suspension.

Another idea: why not a bungee cord closed slider pocket? Like in bungee cord collapsible PC. At high speed it will open and slow down the slider, at normal speeds, it will work like a usual slider.


AndyMan  (D 25698)

Mar 27, 2002, 12:43 PM
Post #18 of 26 (1489 views)
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In reply to:
We accomplished this through the relationship of slider size vs cell size, and a unique cross-porting system. Sport reserves could be set up like this, but they would not pass the 3 second test at low speed. This is one of the reasons I made tandem opening altitudes higher.
Thanks bill, this is more along the lines of what I was suggesting. I don't have nearly any of your guys knowledge in this though.

It seems to me that by changing the shape and material of the slider, you should be able to get it to come down rather quickly when you're below 135mph, and to hang up for just a bit when going faster - it would hang up until you slow down.

It seems to me it's just a matter of finding the right size and shape of the slider, isn't it?

I'm failing to understand why subterminal openings would fail the three second rule. Without the high airspeed, what's keeping the slider up?

_Am

ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
AIM: andrewdmetcalfe
Yahoo IM: ametcalf_1999


Premier billvon  (D 16479)
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Mar 27, 2002, 1:48 PM
Post #19 of 26 (1473 views)
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>One solution is the use of shock absorbing webbing . . .

I see a few problems with that. One, you need a significant length of extensible webbing to deal with a 120-to-0 deceleration. Two, it either requires replacement of the rig after use or mechanical separation of the reserve risers to replace the material.

>Unsymmetrical activation maybe an issue, but it maybe solved by a following system . . .

I think that has two problems:

1. It means the reserve has to complete its opening sequence with one riser significantly longer than the other one, and on a highly loaded reserve, that can induce line twists

2. Such a system would be useless during a cypres activation caused by unconsciousness or incapacity.



-bill von


Engovatov

Mar 27, 2002, 3:19 PM
Post #20 of 26 (1464 views)
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> I see a few problems with that. One, you need a significant length of extensible webbing to deal with a 120-to-0 deceleration. Two, it either requires replacement of the rig after use or mechanical separation of the reserve risers to replace the material.

One need only absorb the peak shock - if it activates, at say 10G, that will absorb a lot of kinetic energy in the stitching. Also - the breakaway element can be easily replaceable (attached at each end to the bent riser.
Unconcious, you will not be in head down..

Assymetric activation is indeed the problem.. Bulk as well. But the biggest problem is that it is not that much needed - current crop of reserves works OK. Getting safer closing loop and flaps will go a much longer way I guess.

What's you opinion on the idea with bungee cord closed thick pockets on slider? Such system even may pass TSO at 150 knots, as it will be invisible, but still activate and slow dow the deployment at 170.. ?





polarbear  (D 25673)

Mar 27, 2002, 5:17 PM
Post #21 of 26 (1451 views)
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I am also by no mean an expert, but I can throw in $.02 here:

While it is true that the slider sees less air pressure holding it up during a subterminal opening, it can still develop a large amount of force. Try driving down the road at 30 mph holding a slider open. Then try driving down the road at 60 mph holding the slider open, and you will see what I mean. Also, during a subterminal deployment, the canopy itself will see less air pressure trying to spread it open and push the slider down, meaning that the forces trying to push the slider down are less.

I think it is true that many years of experience tell us that subterminal openings are often (usually?) slower/softer than terminal ones.



polarbear  (D 25673)

Mar 27, 2002, 5:28 PM
Post #22 of 26 (1445 views)
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Bill, one question I have to ask is that is there any consideration as to actual altitude loss during the 3 seconds required by the TSO? To me, altitude loss is the real consideration. It seems as if a subterminal opening might eat up less altitude per time unit, thus meaning that it would be OK to let a sub-terminal opening take a little longer. Might it be reasonable to redefine the TSO in terms of altitude loss?

I imagine it would be hard to certify that a canopy used up a predictable amount of altitude during opening at a given speed.

One thing I have to say is that I'm not sure that an idea you discussed in an earlier post is such a good idea. You mentioned a sort of "high-speed" reserve, meaning one that was designed to open acceptably at high speeds, but would fit in its own TSO class and thus would not need to obey the 3-second rule. I guess I think that while some high-speed deployment accidents would be prevented with a "high-speed" reserve, there would be at least as many that came about from the "high-speed" reserves not opening in time in a sub-terminal situation.

I think there could be some real potential in using energy absorption methods, like materials that are designed to stretch or break at higher forces and thus eat up some of the high-speed deployment energy.



NathanL100  (D 25636)

Mar 27, 2002, 6:26 PM
Post #23 of 26 (1438 views)
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In reply to:
I think there could be some real potential in using energy absorption methods, like materials that are designed to stretch or break at higher forces and thus eat up some of the high-speed deployment energy.
I agree. This sounds like it could be made reliable and relatively cheaply too. Defiantly a good idea worth looking further into.

Just keep your mind open and suck in the experience. And if it hurts, you know what? It's probably worth it.


Martini  (D 23756)

Mar 27, 2002, 7:36 PM
Post #24 of 26 (1431 views)
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Wow, all these great ideas brewing and not one bottle open! My $.02: The shock absorbing concept is by far the most reasonable one for several reasons; it's simple, cheap, available technology, it requires no user consideration, and most importantly will work just fine even in the case of a high speed /low altitude deployment without dependence on complex AAD technology. Six-foot long shock absorbing lanyards are installed on virtually all fall-protection harnesses used in the construction industry today. Granted, skydiving gear has radically different requirements, but I suspect the technology is at hand to at least begin to improve high-speed reserve openings.



Engovatov

Mar 27, 2002, 8:27 PM
Post #25 of 26 (1424 views)
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>Wow, all these great ideas brewing and not one bottle open!

;-) Should I apply for a patent?



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