Permeability effects on aging reserves?

[pchapman 261]

The question occasionally comes up about aging reserve parachutes, not just what the strength loss might be, but what effects there may be in terms of increased permeability of the fabric (from packing or use), and to what degree that affects the opening characteristics compared to when the reserve was TSO'd.

Eg, a current discussion on retiring old reserves is at
http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=4716147#4716147

Anyone have actual data on permeability testing or what companies like PD have found from any tests on old reserves or reserves used as demo canopies?

I had vaguely heard that some company found that older reserves with a lot of pack jobs didn't open as quickly as when new... but I have no proof of this or any information on the magnitude of any effect.

The point has been made that an old F-111 style main with 60 jumps would still be considered nearly new, while an F-111 style reserve with 60 pack jobs might be considered very old -- with little data to support just how different those canopies really are from the brand new state.

Below is one person's take on permeability changes. I copied it from Dropzone long ago but searches don't seem to find the post anymore at all!??

It gets into some actual permeability data.

Quote

WillemdeVos
Location: Austria
Post subject: Permeability/Porosity tester
Posted: Thu Aug 26, 2004 8:18 am

Hi
I build a cfm indicator.
About 50$ material and view hours work.
It work well as a INDIKATOR.
I do not need to know if F111 has 2,34cfm.
It is ok fore me that I know that my F111 has a range of 2 till 3 cfm.
I can check if reserves are good: 2-6 , borderline: 7-9 or bad: 10 and more .

My experience is:
1)
New F111 canopies (Foil, Manta, Raven ect) decrease in the first +/-150 jumps from 3 to 8cfm.
Than they stay a long time between 8 and 10 cfm .
After 500 and more jumps they go over the 10 cfm stay the next +/-200 jumps that way.
They Reach 12 and more cfm between 800 and 1200 jumps.
That is the same Lifetime that the Dacron lines have.
A good indicator of F111 canopies are the Lines!
2)
Newer Reserves are build from better F111.
I washed (no soap)10 years Old (never used stock repair PD F111) 2 times and it came from 4 to 8 cfm
I washed New (never used stock repair PD F111) 10 times and it came from 2 to 6 cfm
I washed new F111 from Galvenor textiles over 20 times and it stays on 3-5 cfm.
Did you know that PD changed in their reserve manual the max cfm from max 6 to max 8 cfm?
Strong and Vector Tandem reserves can have a max of 10 cfm by the manufacturer.
3)
Now I was asking me why reserves go faster bad than Main canopies.
I tested a 15 Years old Parachutes de France reserve.
It was 15 years build in the same gear and packed 2 times each Year.
100%No jumps on it.
I indicated on all cells a cfm of 10 cfm.

(I edited out parts not relevant to this discussion)