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Was: Recommended specs on reserve exit weight, do you go over max?

 

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RMURRAY

Jul 15, 2006, 6:53 AM
Post #76 of 134 (862 views)
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Re: [phoenixlpr] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

In reply to:
I had one ride on a GlidePath Crickett 147.

MSW is 160 lbs, I was around 200-220 lbs with gear.
I had a soft, stand up landing.

I was just testing that rig and none told me about the limit of the reserve. It was not fair from the seller.

I sell a lot of gear for friends. When I sell a reserve I always ask experience level and exit weight. Sometimes, I will not sell the reserve to a interested buyer. For example a Raven 135-M is an OK reserve but only for someone with an exit weight of up to 150 lbs OR unless they have landed one heavily loaded (know what they are doing). I had a -M for many years and it was overloaded too much. Never had to put a jump on it but finally moved on to a PDr, they are bullet proof and handle being overloaded well - like the other modern reserves.

rm


phoenixlpr  (D 3049)

Jul 15, 2006, 12:07 PM
Post #77 of 134 (850 views)
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Re: [RMURRAY] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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I sell a lot of gear for friends. When I sell a reserve I always ask experience level and exit weight. Sometimes, I will not sell the reserve to a interested buyer. For example a Raven 135-M is an OK reserve but only for someone with an exit weight of up to 150 lbs OR unless they have landed one heavily loaded (know what they are doing).

I had a different case. I demod a gear before buying and the case ended that I had to buy that rig. The seller was telling anything about what reserve was there. Most of the people choose their gear, some are chosen by a gear.

I'm planing to use it until 2011 or as long as its airworthy.


(This post was edited by phoenixlpr on Jul 15, 2006, 12:08 PM)


mjosparky  (D 5476)

Jul 15, 2006, 3:36 PM
Post #78 of 134 (847 views)
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Re: [phoenixlpr] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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The seller was telling anything about what reserve was there.

Did you ask or even read the packing data card?Smile


phoenixlpr  (D 3049)

Jul 15, 2006, 10:04 PM
Post #79 of 134 (831 views)
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Re: [mjosparky] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

We don't have packing data card, we have a gear book. A small logbook for the canopies with other info like container, AAD in case of reserve.
The gear was in good shape and reserve pack was valid. Gear books remain ed in a 3rd party who was a kindda mentor of mine in that time. I trusted them and that was a mistake.


mjosparky  (D 5476)

Jul 15, 2006, 11:06 PM
Post #80 of 134 (829 views)
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Re: [phoenixlpr] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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We don't have packing data card, we have a gear book. A small logbook for the canopies with other info like container, AAD in case of reserve.
The gear was in good shape and reserve pack was valid. Gear books remain ed in a 3rd party who was a kindda mentor of mine in that time. I trusted them and that was a mistake.

Just to be sure I understand. In your country they use a type of logbook something like we use a "packing data card" for reserve canopies. Does this logbook stay with the reserve canopy if the rig is split up? Is there a second logbook for the harness/container?

It sounds like you are saying that this logbook stays with someone other then the owner of the rig. Is this right?

In the US we have a problem with packing data cards. There is only one with a complete rig and if the rig is split up the card goes with the reserve canopy. I think there should be a mandatory second card for the H/C so a rigger working on it has a history available.


strop45  (D 957)

Jul 16, 2006, 12:46 AM
Post #81 of 134 (847 views)
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Re: [mjosparky] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

Humm!. I don't know much about skydiving, but do understand the basic laws of physic at least as well as most of the posters in this discussion.

My take is that both sides are partly correct.

Weight affects terminal velocity For the same drag, a heavier object falls faster. (if you don't believe this, try wearing a weight belt).

Opening the canopy increases the drag and therefore the velocity decreases. During de-acceleration the tension in the lines and canopy fabric is only dependant on the velocity, however with higher weight the time taken to de-accelerate is increased and therefore the stress is present for more time.

The longer the force is present the more likely that the lines/fabric will reach breaking point and fail.

Conclusion, if you exceed the design/certification limits you run the real risk that the canopy will fail.


(This post was edited by strop45 on Jul 16, 2006, 12:55 AM)


phoenixlpr  (D 3049)

Jul 16, 2006, 2:38 AM
Post #82 of 134 (839 views)
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Re: [mjosparky] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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Just to be sure I understand. In your country they use a type of logbook something like we use a "packing data card" for reserve canopies. Does this logbook stay with the reserve canopy if the rig is split up? Is there a second logbook for the harness/container?
One (small)book per canopy. The H/C is registered in those books.

In reply to:
It sounds like you are saying that this logbook stays with someone other then the owner of the rig. Is this right?
It was with a 3rd party util I payed the rig.

In reply to:
In the US we have a problem with packing data cards. There is only one with a complete rig and if the rig is split up the card goes with the reserve canopy. I think there should be a mandatory second card for the H/C so a rigger working on it has a history available.
AFAK In Finland the repair logs seems to be in the book of the reserve, but I'm not a rigger.


mjosparky  (D 5476)

Jul 16, 2006, 11:50 AM
Post #83 of 134 (816 views)
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Re: [strop45] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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During de-acceleration the tension in the lines and canopy fabric is only dependant on the velocity,

And the velocity is dependant on the weight. Lower weight, lower velocity.

In reply to:
The longer the force is present the more likely that the lines/fabric will reach breaking point and fail.

Fill time of a canopy plays a role in this. The shorter the fill time is the faster peak loads are reached. It is this sudden onset of peak load that is more likely to damage the canopy. Canopies with a longer fill time can take the same loads without damage because it comes on slower.

Conversely when the peak forces are stretched over a longer period of time the jumper can be affect more. A human can take more gs in a spike than he/she can over an extended period.

I hope this makes senseSmile


mjosparky  (D 5476)

Jul 16, 2006, 11:53 AM
Post #84 of 134 (815 views)
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Re: [phoenixlpr] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

If the H/C and the reserve get split up, the logbook goes with the canopy, correct? How do you keep track of the history of the H/C?

Open to response from anyone who's country has a way to handle this problem.Smile


strop45  (D 957)

Jul 16, 2006, 1:39 PM
Post #85 of 134 (809 views)
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Re: [mjosparky] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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Fill time of a canopy plays a role in this. The shorter the fill time is the faster peak loads are reached. It is this sudden onset of peak load that is more likely to damage the canopy. Canopies with a longer fill time can take the same loads without damage because it comes on slower.

Conversely when the peak forces are stretched over a longer period of time the jumper can be affect more. A human can take more gs in a spike than he/she can over an extended period.

I hope this makes sense

Thanks for your reply. Smile Makes good sense. Fill time is obviously a very important factor in determining the load on the lines and fabric (and the jumper). I guess that this is why terminal reserve openings are generally less fun than main canopy openings and hence this thread.

I also think that your comments about ability of jumpers to take g's also applies to some extent to canopies/lines.

Imagine two jumpers of different weights and body shapes such that they both had the same fallrate. For a given canopy both would cause the same peak tension loading in the lines/fabric, however the heavier jumper would cause it to be present for longer, hence more total load and higher risk of failure.

Looking at it another way, the kinetic energy in a moving object is proportional to its mass, i.e. for a heavier jumper you are asking the canopy to absorb more energy. The manufacturer has rated the canopy to only absorb a certain amount of energy without failure, if you put more load on it than this, it may fail.


phoenixlpr  (D 3049)

Jul 16, 2006, 2:36 PM
Post #86 of 134 (802 views)
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Re: [mjosparky] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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And the velocity is depending on the weight. Lower weight, lower velocity.
Impulse and kinetic energy is depending on speed and weight. Velocity is not depending on weight.


mjosparky  (D 5476)

Jul 16, 2006, 2:59 PM
Post #87 of 134 (798 views)
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Re: [phoenixlpr] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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In reply to:
And the velocity is depending on the weight. Lower weight, lower velocity.
Impulse and kinetic energy is depending on speed and weight. Velocity is not depending on weight.

I may be using the wrong word, but I will guarantee you that if you strap on 40 lbs. of lead you with be falling faster than without it. (all other things being equal) How fast you go in freefall depends on surface area to mass or weight. That is why FFs fall faster than RW flyers.

I am done with this.Crazy


Ron

Jul 16, 2006, 7:28 PM
Post #88 of 134 (779 views)
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Re: [phoenixlpr] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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IMHO the overloaded reserve blowing up on opening has no base, that's just a myth.

Here is an example of a reserve blowing up.

Quote:
http://www.dropzone.com/...post=1121963#1121963
After the opening shock, I looked up to see my bright, white reserve, and to my horror, see several cells blown out.

Why ignore people with real world experience?


(This post was edited by Ron on Jul 16, 2006, 7:31 PM)


crewkeith  (B 24861)

Jul 17, 2006, 8:59 AM
Post #89 of 134 (743 views)
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Re: [mjosparky] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

yeah but still under max weight

.


phoenixlpr  (D 3049)

Jul 17, 2006, 9:56 AM
Post #90 of 134 (732 views)
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Re: [Ron] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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Why ignore people with real world experience?

Opening from higher speed than certified was not a question.


Ron

Jul 17, 2006, 10:16 AM
Post #91 of 134 (731 views)
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Re: [phoenixlpr] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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Opening from higher speed than certified was not a question.

Neither should be weight, but you debate that?

See how your arguments make no sense? You claim that only one (speed) is important, not the other (weight). There is a reason why the people who make these things have both a speed and weight listed.

I still can't understand how you think you know more than the makers of the canopies, and the people who test themCrazy

Do you really think you know more than the people who make and test these things?


phoenixlpr  (D 3049)

Jul 17, 2006, 10:21 AM
Post #92 of 134 (727 views)
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Re: [Ron] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

Have you read the thread or just the last post? Crazy


Ron

Jul 17, 2006, 10:29 AM
Post #93 of 134 (723 views)
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Re: [phoenixlpr] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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Have you read the thread or just the last post?

The whole thread.

You debate guys like Sparky who have more test jumps than most people have jumps. I'd bet that Sparks there has more jumps on experimental equipment than you have total jumps.

You are clearly not an idiot. You have alot of book smarts. Sparky has the actual experience of dealing with these things.

I wonder what makes you think you know more than the makers and testers of the equipmentCrazy


(This post was edited by Ron on Jul 17, 2006, 10:36 AM)


phoenixlpr  (D 3049)

Jul 17, 2006, 10:41 AM
Post #94 of 134 (719 views)
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Re: [Ron] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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Ever notice that EVERYONE has disagreed with you? But you still claim to know better than ALL of them?
How dare you ask questions if EVERYONE could be disagreed with you?

I have my opinion as long as someone can prove me that my point is wrong.


Ron

Jul 17, 2006, 11:18 AM
Post #95 of 134 (710 views)
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Re: [phoenixlpr] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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I have my opinion as long as someone can prove me that my point is wrong.

I wonder what makes you think you know more than the makers and testers of the equipmentCrazy


phoenixlpr  (D 3049)

Jul 17, 2006, 11:34 AM
Post #96 of 134 (708 views)
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Re: [Ron] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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I wonder what makes you think you know more than the makers and testers of the equipmentCrazy

I wonder what makes you think that mine is bigger than yours ... or his is bigger than your ... is the right way to prove anything?Crazy


RogerRamjet  (D License)

Jul 17, 2006, 12:03 PM
Post #97 of 134 (700 views)
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Re: [phoenixlpr] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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In reply to:
I wonder what makes you think you know more than the makers and testers of the equipmentCrazy

I wonder what makes you think that mine is bigger than yours ... or his is bigger than your ... is the right way to prove anything?Crazy

Oh well, here goes....

I don't know how current drop testing for TSO is done, but here is what I witnessed at Z-Hills in the late '70s. Strong was going for a TSO on a reserve. They did several drops at maximum allowed velocity for that canopy (I don't recall the velocity, too many years ago) and tested the reserve to failure. You know how? By adding 25lbs of weight to the dummy after each drop until the reserve blew up.

Think whatever you like, but velocity AND weight count....


phoenixlpr  (D 3049)

Jul 17, 2006, 12:22 PM
Post #98 of 134 (692 views)
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Re: [RogerRamjet] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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Oh well, here goes....

I don't know how current drop testing for TSO is done, but here is what I witnessed at Z-Hills in the late '70s. Strong was going for a TSO on a reserve. They did several drops at maximum allowed velocity for that canopy (I don't recall the velocity, too many years ago) and tested the reserve to failure. You know how? By adding 25lbs of weight to the dummy after each drop until the reserve blew up.

Think whatever you like, but velocity AND weight count....

I'm not a test dummy. How is a drop test executed?


RogerRamjet  (D License)

Jul 17, 2006, 12:37 PM
Post #99 of 134 (689 views)
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Re: [phoenixlpr] recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

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In reply to:
Oh well, here goes....

I don't know how current drop testing for TSO is done, but here is what I witnessed at Z-Hills in the late '70s. Strong was going for a TSO on a reserve. They did several drops at maximum allowed velocity for that canopy (I don't recall the velocity, too many years ago) and tested the reserve to failure. You know how? By adding 25lbs of weight to the dummy after each drop until the reserve blew up.

Think whatever you like, but velocity AND weight count....

I'm not a test dummy. How is a drop test executed?

At that time, we had a Cessna 196 (Cessna 195 with a 450hp engine) that was used. A drop dummy that could have weight added internally, and a rail system that allowed pushing the dummy out of the aircraft. The aircraft made a constant speed pass at 500ft agl and the dummy was manually pushed out. The reserve had to inflate without failure up to the speed AND weight being sought for the TSO. Strong also chose to continue adding weight until the reserve actually failed (or was required to, I do not know what the rules were/are). At any rate, every reserve I saw tested that summer eventually failed when enough weight was added. You can decide what that means for yourself. I think it means that if you exceed the specified exit weight by enough, you risk blowing up your canopy. Surely the canopies are over rated to some extent to allow for variations in materials and such, but just how far do you want to push it?


(This post was edited by RogerRamjet on Jul 17, 2006, 2:33 PM)


labrys  (D 29848)

Jul 17, 2006, 1:26 PM
Post #100 of 134 (679 views)
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Re: [strop45] Was: Recommended specs on reserve exit weight, do you go over max? [In reply to] Can't Post

Quote:
Imagine two jumpers of different weights and body shapes such that they both had the same fallrate. For a given canopy both would cause the same peak tension loading in the lines/fabric, however the heavier jumper would cause it to be present for longer, hence more total load and higher risk of failure.

If peak force being present for longer periods of time increases the risk of failure wouldn't that also mean that the reserve could only be used x number of times? I know that any canopy will wear out with time and use, but I'm trying to get a feel for how this particular argument works. My approach might be too simple, but here goes:

Let's say that doubling the max weight causes the canopy to experience the peak load twice as long. I know that this might not be linear, I'm just giving an idea a shot. Wink

If twice the max weight causes or significantly increases the risk of blowing up the canopy, then wouldn't opening at just the max weight 2 times result in the same risk? I'm assume the canopy also doesn't "heal" from the damage induced during a normal opening at max weight.

Even if the time under load is not linear, what is the difference between max weight and twice max weight, 10 times longer, 100 times longer?

Are reserves also rated for how many terminal openings they can sustain?

This is not intended as a challenge to the fact that the canopy has a higher risk of failure at higher suspended weights, it's just a question about this particular example.


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