Reserves, pack jobs, and useful life.

[Jimbo 0]

How many pack jobs on a modern reserve before performance really begins to degrade? I know that PD wants theirs back for recertification after 40 pack jobs, but how worn will a reserve be after 40 packs?


-
Jim

"Like" - The modern day comma
Good bye, my friends. You are missed.

[jsaxton 0]

Max life = 20 yrs + 3 = 60 cycles

[sundevil777 94]

I have heard about the testing that has shown that it is the pack job and not the deployment that wears out an F-111 reserve, but I would not consider an F-111 main to be worn out after 40 jumps, and that is with 40 repacks and deployments. So I just don't understand it unless perhaps it is the time spent packed or something else that is the real mechanism.

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

[hookitt 0]

No clue what that has to do with the question since that's just a lenght of time and assuming you packed the reserve ever 4 months for 20 years, that would be 60 pack jobs. Good math though but what's the plus 3 for?
=======

I have a reserve that has at least 20 jumps on it possibly more. 3 of them are by me and the rest were from test jumps prior to installing it. I haven't run it through a porosity checker but it feels just fine. My current reserve has at least 2 water landings and heck, I don't know how many pack jobs but I'm sure it's only 20 or so. It's just fine.

I regularily work on reserves that are used for water landings often in the ocean. They get put through a few rinsings then hung up in a tower. Once a year they get a porosity check. Many of these still pass after 15 years of service and lots of pack jobs.

My grammar sometimes resembles that of magnetic refrigerator poetry... Ghetto

[Hazarrd 1]

I think the idea behind may be that since it is your reserve (ie your last chance), there is no reason to risk anything on it being deteriorated.

.-.

[riddler 0]

I'm sure the manufacturers would like to mandate that reserves get replaced after every use. Think how many canopies they would sell. If the thing still has a useful life, even after 100 repacks, then I'll jump it. But then again, I know my rigger will do a thorough inspection and pack job and I trust my rigger.

[jsaxton 0]

Thanks for the insighr Timmy

[jsaxton 0]

BTW: You're THE MAN!
And I LOVE your riser mod! Gotta get that on my new rig!

[Tonto 1]

Are you not assuming that this reserve will never be used? Every use is likely to be prior to the next packjob, no?

I'm with Hookitt on this. I use my reserves often - and I trust them. I started in the days of F-111 type fabric 7 cell main canopies - loaded to a fraction of my reserve, admittedly, but would probably only start to worry when my rigger did.

I've seen lots of Tempo reserves with built in turns. Mine flies straight. I'll keep it thanks.

t

It's the year of the Pig.

[Hooknswoop 19]

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How many pack jobs on a modern reserve before performance really begins to degrade? I know that PD wants theirs back for recertification after 40 pack jobs, but how worn will a reserve be after 40 packs?

PD requires their reserves be sent back to the factory after 40 re-packs or 25 deployments, whichever comes first. That is just over 13 years if it is re-packed every 4 moths with no deployments.

My theory on why re-packs cause more wear that deployments is deployments load the fabric evenly whereas packing does not.

F-111 (not really F-111 but is the common term in use) is a weave of nylon. These fibers can be 'bunched up', leaving space between the fibers next to the 'bunch'. A Javelin reserve PC is a great example of this. Even when treated like they are made of tissue paper, they still show 'bunches' and lighter areas when held up to the light. A reserve that is inflating or inflated is loading the fabric evenly, or at least fairly evenly. This equal loading doesn't tend to create these bunches and shows less wear than packing. When packing a reserve, the fabric gets loaded unevenly. The rigger deals with one small area at a time, pulling the fabric tight and neat. Oils from the rigger's hands get on the fabric, etc. This results in a stress area, or an area that is more likely to fail when loaded. It also increases the porosity (permeability) of the material, allowing more air to pas through the material. This can increase the amount of time it takes the reserve to open and decrease it's ability to flare for landing.

I think PD's requirements are fine. 13 years is a long time to have a reserve. That is a lot of packing of the fabric. Having them inspect it after 40 re-packs / 25 deployments is a good idea.

Derek

[AndyMan 7]

I can't answer your question about PD, nor am I a rigger.

That said, to me - it really depends on how I'll be using the reserve.

For example, a few monthes ago I did a round jump. The main was 30 years old, and I think the reserve was close to 50 years old. I trusted the rigger that packed it, so I jumped it. I knew the reserve had been appropirately tested.

On my own rig though, I'm loading a PD reserve at close to 1.7. When I jump this reserve I need it to be in the best shape possible. I want this reserve to be brand new, because I know at this wingloading I'm going to need every bit of lift this canopy can give me. I'm planning on swapping out this reserve every few years because I only want new fabric.

_Am

__

You put the fun in "funnel" - craichead.

[DrewEckhardt 0]

A reserve is not a main; so the life expectancy should be different.

Few people intentionally load F111 mains beyond 1.0 pounds/square foot.

If you jump a small main and buy a Vector or Javellin sized for it, your reserve loading can easily end up in the 1.5-2.0 pound/square foot range. Preoccupation with the 2 canopy out situation also leads to reserve loadings far in excess of what would be appropriate for an F111 main. At that point, it's worn out when it stops acting like ZP.

Strength requirements may also be an issue. A reserve needs to survive (I saw a reserve split into 2 and 5 cells held together only by the reinforcing tape at the tail) higher deployment speeds (this case was an AFF instructor who got knocked out when the student deployed, resulting in a head-down deployment while unconscious) than a main, especially now that we have cypresses.

Packing is an issue. I fold my mains in the air without clamps, so there's not much friction between the canopy and ground/itself. I carefully pack all my single-canopy rigs on the ground with clamps, so there should be more wear.

You also usually have a reserve to go with your main, so its reliability is less critical.

[LouYoung 0]

I'm not a rigger, nor do I really have much experience skydiving and no experience flying a reserve, but here's my thoughts:

A reserve parachute is just a regular parachute, is it not? It might have stronger seams and be designed to be more docile (not eliptical or ZP) and have a lower aspect ratio, but it's really just a parachute.

If I can pack and jump a regular F-111 9-cell main 1000 times and still fly and land it, why would a reserve wear out after 60 re-packs and no jumps? Why is a used reserve with 5 jumps on it worth less than a used reserve with no jumps? A main sells for nearly retail even though it has 100 jumps on it. Even PD's packing manual states that packing doesn't wear out a canopy, so pack and re-pack to your heart's content for practice.

If the argument that you want your reserve to be as new and as fresh as possible when you have you use it because it's your last resort, then why would you jump a main with 300 jumps on it? If a reserve with 300 jumps and re-packs on it is SO bad and nearly guaranteed to mal, what makes it different than a main? Would you jump a main over and over again if it was nearly guaranteed to mal?

What makes a reserve so fragile?

[riddler 0]

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Even when treated like they are made of tissue paper, they still show 'bunches' and lighter areas when held up to the light. A reserve that is inflating or inflated is loading the fabric evenly, or at least fairly evenly. This equal loading doesn't tend to create these bunches and shows less wear than packing. When packing a reserve, the fabric gets loaded unevenly. The rigger deals with one small area at a time, pulling the fabric tight and neat. Oils from the rigger's hands get on the fabric, etc. This results in a stress area, or an area that is more likely to fail when loaded. It also increases the porosity (permeability) of the material, allowing more air to pas through the material.

Hook - what is the chance of the failure being larger than one square of the material? It seems unlikely that these factors would cause a large failure area in the material - at most a small hole that would probably be found at the next repack.

[DrewEckhardt 0]

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A reserve parachute is just a regular parachute, is it not? It might have stronger seams and be designed to be more docile (not eliptical or ZP) and have a lower aspect ratio, but it's really just a parachute.

Those are probably (I don't know about strength for higher airspeed deployments) the root problems.

ZP fabric does not change the performance characteristics of a parachute - it just means it retains them longer. Stories from the good old days place the effective lifespan of PD's Excalibur cross-braced F111 canopy at a few hundred jumps (wear is higher on a reserve pack job). Conversely, at 1200 jumps my Stiletto is as porous as when it left the factory (it just leaks a little more air through the enlarged stitching holes).

Reserve shape (low aspect ratio square, and perhaps the open nose configuration) means they start off with lower performance (notably a higher stall speed) than a modern main canopy.

Loose some of the already low performance, load it to levels like many of us enjoy on our main canopies, and you're not going to have acceptable (injury free) landings.

[FrogNog 1]

I had sort of thought the "max # of repacks" was intended to be a time limit, not a jump limit. And I thought the reasoning behind the ~10 year time limit was similar to the 5 year time limit on DOT-rated motorcycle helmets: after X years, even though the safety device in question will probably be perfectly serviceable, newer improved safety devices will have been created and your safety can be improved to some degree by upgrading.

Thus, this is a forced upgrade deal. Maybe the reserve manufacturers could clarify this by saying "This reserve may not be repacked by a rigger and should be returned to the factory after it has been packed 40 times or after 12 years since the date of manufacture has elapsed."

-=-=-=-=-
Pull.

[Hooknswoop 19]

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Even when treated like they are made of tissue paper, they still show 'bunches' and lighter areas when held up to the light. A reserve that is inflating or inflated is loading the fabric evenly, or at least fairly evenly. This equal loading doesn't tend to create these bunches and shows less wear than packing. When packing a reserve, the fabric gets loaded unevenly. The rigger deals with one small area at a time, pulling the fabric tight and neat. Oils from the rigger's hands get on the fabric, etc. This results in a stress area, or an area that is more likely to fail when loaded. It also increases the porosity (permeability) of the material, allowing more air to pas through the material.

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Hook - what is the chance of the failure being larger than one square of the material? It seems unlikely that these factors would cause a large failure area in the material - at most a small hole that would probably be found at the next repack.

My concern is that 1) that abunched up area could be the starting oint for a failure on deployment, and 2) with too many bunched up areas, the porosity can increase to the point that the openings are unacceptably long and the landings are too hard.

Derek

[BlindBrick 0]

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How many pack jobs on a modern reserve before performance really begins to degrade?

One of the really big arguments in favor of the extgended repack cycle is that packing lowers the porosity of a reserve, so the less repacks the better. In one test, they found that repacking a reserve just 12 times was enough for it to drop below the porosity standards required for reserves. Granted the porosity of a main could be much higher and still be safe, it is food for thought.

-Blind

"If you end up in an alligator's jaws, naked, you probably did something to deserve it."

[alan 1]

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My theory on why re-packs cause more wear that deployments is deployments load the fabric evenly whereas packing does not

In addition, George Galloway from PS has written that it is the contact with the surface area the reserve is being packed on that causes much of the damage. Most reserves seem to be packed on a carpeted area and the interaction fibers act like velcro and degrade the canopy. I seem to recall reading a comment from him that a smooth, sealed concrete surface would be best for the canopy. Then again, I may just remember it all wrong.

alan

[hookitt 0]

I gotta ask, what tests are you referring too?

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In one test, they found that repacking a reserve just 12 times was enough for it to drop below the porosity standards required for reserves.

Parachutes are really tough so I'd like to see this test.

My grammar sometimes resembles that of magnetic refrigerator poetry... Ghetto

[headoverheels 292]

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ZP fabric does not change the performance characteristics of a parachute - it just means it retains them longer. Stories from the good old days place the effective lifespan of PD's Excalibur cross-braced F111 canopy at a few hundred jumps (wear is higher on a reserve pack job). Conversely, at 1200 jumps my Stiletto is as porous as when it left the factory (it just leaks a little more air through the enlarged stitching holes).

I put 900 jumps and repacks on my Raven F-111 main, and someone bought it and jumped it after me. I wouldn't be too worried about 60 repacks on my MicroRaven reserve.

[councilman24 36]

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***In addition, George Galloway from PS has written that it is the contact with the surface area the reserve is being packed on that causes much of the damage. Most reserves seem to be packed on a carpeted area and the interaction fibers act like velcro and degrade the canopy. I seem to recall reading a comment from him that a smooth, sealed concrete surface would be best for the canopy. Then again, I may just remember it all wrong.

Actually it was the Belgian army that did the some of the studies on packing surface effect, as well as porosity changes due simply to packing. They presented the data at one of the PIA symposiums, 1997 I think. Hmmm, maybe 1993. Their testing on surfaces consisted of dragging weighted fabric across different surfaces. I don't remember whether the testing was porosity, tensile strength, tear strength or a combination. The Loser, a worn poly tarp, like at your local bogie. The fibers stick up and "tear" into the material like a very stiff brush. The Winner (least damage) was a commercial smooth finished concrete, like you might find on a factory floor, not a sidewalk. Porosity changes were seen after just a few pack jobs.

Many of you have indicated trust in your rigger. We appreciate it but recognize that very few independent riggers or lofts have the capability of porosity testing. We can only guess at the changes. As Hook talked about, in extreme cases like Javelin PC's it's easy to see the changes in the weave. In canopies the changes are much more subtle.

Why does it matter and why are reserve held to higher standards than non ZP mains? It's your LAST CHANCE TO LIVE! It speaks alot that reserves don't often blow up if not overloaded. But with the current trends in gear more and more people are wearing smaller reserves and going faster. It better be in the best shape that it can be.

The industry tried to suggest a 10 year service life 10-15 years ago. That went over like a lead brick in the U.S. Recent discussions at PIA rigging and technical committee meetings have concluded that there are so many variables in gear usage and storage that any mandated service life could not necessarily be supported. Many (all?) manufacturers will quote a manditory service lifes when bidding on military contracts or selling to similar users. These, according to some of the manufacturers, are really based on the desires of the customers and the contract, versus any real data or need to take component out of service. Many other countries or users impose manditory lifetimes. But don't look for it to become widespread or manditory in the U.S. sport industry in the near future.

About the rounds mentioned above. They started at 80 to 120 cfm, or 40 to 60 cfm, versus 0 to 3 cfm for new F-111 type fabric. F-111 is no longer made.

The oldest sport reserve I current work on is 1989. (I've got a couple of older pilot rigs.) This is mainly a matter of changes in design and evolution of gear versus taking reserves out of service. The obsolesence of the entire rig gets it put in the closet. About 4 years ago I was still packing a 1981 5 cell Swift. I didn't much want to but didn't have a good reason to retire it. The jumper (a 1970's world champion) finally retired from jumping, partly based on not wanting to invest in new gear at this time.

So, by the time you don't want to jump the reserve (based on age, not usage), your likely to want to jump newer gear anyway.

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

[mjosparky 3]

How much do you think the material has degraded during the handling during manufacturing. I know some or maybe even all the manufacturers test fabric when received, but how many check the completed canopy?
Sparky

My idea of a fair fight is clubbing baby seals

[riggerrob 563]

Strong Enterprises insists on retiring all their tandem gear after it has been in service for 18 years and I do not know any rigger who will repack a tandem reserve with more than 20 "rides."

The original reason for Strong instituting service lives was to get all the earliest tandem rigs back to the factory for all the updates. Trust me, everybody's early tandem rigs were crude. In the long run, Strong's policy (8 year and 13 year inspections followed by retirement at 18 years) is practical. If you have not worn out a tandem main within the first 8 years, you are in the wrong business. After 8 years in the California desert, a tandem rig is faded, frayed and filthy = due for a major overhaul.

Back in the mid-1990s - when we were tearing up F-111 Strong tandem mains on a regular basis - we used to repack their reserves a maximum of 20 times. After that we cut off the Kevlar lines, installed Dacron lines and put another 600 jumps on them before retirement.

One reason for service life limits is to limit liability for manufacturers. They have no way of knowing the condition of gear after it has been in service for 20 plus years. The last thing they want is their good name associated with a faded, frayed, filthy and sloppily repaired rig that they last saw 20 years ago.
In comparison, does your local Ford dealer still sell parts for Pintos?

Now let's look at service life issues from the fashion angle. How many modern skydivers still want to jump round reserves or Safety Flyers or Sentinel AADs or Top-Secrets or Wonderhogs or Pegasus, etc?