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John_snurkowski

Acid Mesh

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Looking for an old rigger's advice. 

Someone just dropped off Security Pilot Emergency rig and asked me to tell them whether or not it's airworthy. (It likely is not.) But the parachute is from the '70s and as far as any records I have seen on it, has not been tested for acidity. 

 

Can someone tell me how I am supposed to conduct that test, and possibly the list of serial numbers (which I'm told are out there) which Security said are subject to the acid mesh pandemic?

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A non-riggers recollection = Some round canopy's drive slot mesh was not properly cleaned / treated during manufacturing which led to a low ph condition on the surface of the mesh = acid mesh.

When the mesh is folded and packed against the canopy's nylon panels, they could become discolored and otherwise damaged, (think failure during deployment due to weakend fabric).

 

How'd I do Jerry?

 

Cheers

 

 

 

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14 minutes ago, kleggo said:

A non-riggers recollection = Some round canopy's drive slot mesh was not properly cleaned / treated during manufacturing which led to a low ph condition on the surface of the mesh = acid mesh.

When the mesh is folded and packed against the canopy's nylon panels, they could become discolored and otherwise damaged, (think failure during deployment due to weakend fabric).

 

How'd I do Jerry?

 

Cheers

 

 

 

Hi Kleggo,

Pretty good, if I do say so myself.

Re:  Some round canopy's drive slot mesh was not properly cleaned / treated during manufacturing which led to a low ph condition on the surface of the mesh = acid mesh.

It wasn't that it was not properly cleaned.  It was that the mesh mfrs added a non-flammable 'coating' to the mesh.  The mesh still met the Mil Spec req'ments.  But, this 'coating' is what caused the interaction with the nylon fabric in the canopies; resulting in strength failure.

They added the 'coating' so the non-flammable mesh could be used in things like tents, etc.

The parachute mfr's did not know about the coating, so they used the mesh without concern.

Anyway, that's my story & I'm sticking with it.

Jerry Baumchen

 

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19 minutes ago, kleggo said:

A non-riggers recollection = Some round canopy's drive slot mesh was not properly cleaned / treated during manufacturing which led to a low ph condition on the surface of the mesh = acid mesh.

When the mesh is folded and packed against the canopy's nylon panels, they could become discolored and otherwise damaged, (think failure during deployment due to weakend fabric).

 

How'd I do Jerry?

 

Cheers

 

 

 

That's about it. Mike Smith from the old Spaceland Parachute Center discovered it while packing his girlfriend's reserve. The fabric tested fine during a repack, then 120 days later during another repack he pull tested it again and the fabric fell apart like wet paper. It was determined that the contaminated mesh having contact with the F111 fabric degraded it severely. No one ever figured out how the fabric could test perfectly fine for a long time, then suddenly fall apart in the course of one repack cycle.

The fix was an acid test followed by a specific washing method if it was positive.

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To further complicate the issue, only certain batches of acidic mesh reacted with certain batches of F-111 fabric. Note that several other fabric mills sold fabric similar to F-111. Finally, it required a specific combination of heat and humidity for the the two types of fabric to interact and deteriorate the canopy fabric. Only Strong Enterprises and Free-Flight stuck with MIL-SPEC fabric and mesh. Round canopies from all other manufacturers are suspect. The FAA, GQ Security, National, Pioneer, etc. issued Service Bulletins to get their customers back in the air, but that was only a short-term goal. By 1990, square reserve manufacturers had caught up with demand and sold plenty of replacement reserves. Sales of round reserves plummeted during the late 1980s. By 1990, square reserve manufacturers had caught up with demand and by 1990 something like 80 or 90 percent of new containers were sold with square reserves.

While I may have tested a thousand-ish round reserves with bromocreasol green and tensile tested them too, I no longer have the tools or the desire to ever test another round reserve built during the mid-1980s. If anyone brings me a 1980s vintage round canopy, I point them towards the museum.

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1 hour ago, riggerrob said:

To further complicate the issue, only certain batches of acidic mesh reacted with certain batches of F-111 fabric. Note that several other fabric mills sold fabric similar to F-111. Finally, it required a specific combination of heat and humidity for the the two types of fabric to interact and deteriorate the canopy fabric. Only Strong Enterprises and Free-Flight stuck with MIL-SPEC fabric and mesh. Round canopies from all other manufacturers are suspect. The FAA, GQ Security, National, Pioneer, etc. issued Service Bulletins to get their customers back in the air, but that was only a short-term goal. By 1990, square reserve manufacturers had caught up with demand and sold plenty of replacement reserves. Sales of round reserves plummeted during the late 1980s. By 1990, square reserve manufacturers had caught up with demand and by 1990 something like 80 or 90 percent of new containers were sold with square reserves.

While I may have tested a thousand-ish round reserves with bromocreasol green and tensile tested them too, I no longer have the tools or the desire to ever test another round reserve built during the mid-1980s. If anyone brings me a 1980s vintage round canopy, I point them towards the museum.

Hi Rob,

Re:  Only Strong Enterprises and Free-Flight stuck with MIL-SPEC fabric and mesh.

From what I learned back then, all of the mesh met the Mil-Spec req'ments.  

The problem was that the Mil-Spec did not consider/address that the materials might be treated with this 'non-flammable' coating.

Not all of the mesh used had this coating.

Jerry Baumchen

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A bit off the topic Rob, but in the small world we live in, you were the one who performed the first two modifications on the Phantom that I have. The diaper was changed from a single stow to a double stow, and then later, after Scott Wakefield blew up a 28' Phantom at terminal, you also did the service bulletin adding a Kevlar reinforcement to the lower lateral band. That's when you were working for Manley at Cal City. I took the canopy with me to Misawa Japan and discovered from Parachutist that it had been recalled for acid mesh. I surrendered and replaced with a square reserve.

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It also was not just the mesh as Rob mentioned.  I had a Pioneer with two panels on one gore next to one larger piece of mesh. So two pieces of white fabric next to one piece of mesh.  Had seen identical conditions since sewn together.  One panel full strength, one completely degraded. The two panels might have come from different lots, batches, rolls etc. but had been sewn next to each other.  We gave Invista, maker of nylon filament, samples of bad fabric.  IF they discovered the issue they never told the industry.  I did several high tech spectroscopic analysis on the bad versus good nylon. I couldn't identify the difference.

To the OP, I pack a lot of old stuff but I would not pack an old Securty LoPo  in a pilot rig.

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