Porosity Check

[tdog 0]

Can anyone tell me about porosity checks for canopies... I know a paraglider dealer can do it for a paraglider using a tool. Seems like this could be handy for used canopies in our sport too..

[DougH 270]

I allways suck on the fabric... very hightec I know!

"The restraining order says you're only allowed to touch me in freefall"
=P

[firstime 0]

put it over your head for 10 minutes... if you die,it's still good my understanding is that if you can push your thumb thru it.. it's done??

[mark 107]

Balloon fabric is usually tested with a differential pressure of 10" H2O. Aerostar makes a nice portable tester, with a carrying case about 1 foot cubed. Fabric permeability tests are a standard maintenance item.

Parachute canopy fabric is tested at just 0.5" H2O. I have seen home-built permeability testers that use a variable-speed vacuum cleaner motor to create the differential pressure, but I think that if you want a substitute for sending your canopy back to PD (Icarus, etc.), you'll have to spend big bucks.

Frazier Instruments sells a permeability tester: http://frazierinstrument.com/products/fap/fap-lp.html. It doesn't look very portable. "Call for price." I haven't called Frazier Instruments because I don't have room for a bench-mounted tester. Perhaps their price is reasonable. Let us know!

MARK

[mark 107]

Quote

put it over your head for 10 minutes... if you die,it's still good my understanding is that if you can push your thumb thru it.. it's done??

Not quite. The "thumb test" gives you information about strength. There are plenty of fabrics that are stronger than F-111 or ZP, yet much more permeable.

Mark

[tdog 0]

Well I took a paraglider I ended up buying tonight, to a friend who is a paraglider instructor and... He had this cool little toy:


http://www.jdc.ch/site/index.php?option=com_content&task=view&id=64&Itemid=134&lang=en


He ran 7 tests, threw out the best and worst, and took the average of the rest, in a database application he built, and kicked out a number that lines up with paragliding manufacture's and DHV tables... He had a database of 119 other wings tested and could tell me exactly where the canopy lined up with other wings tested. Scores are, 300 = grounded, no longer airworthy. 15-20 (ish) = new. Everything in between is airworthy but at various life remaining...

I kind of want one... If I tested a group of new skydiving canopies, and a group of canopies at the end of their life, I could figure out where a used canopy sits...

I am a toy person.

[diablopilot 2]

It's got to be 4 times the value of most peoples rigging kits!

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You're not as good as you think you are. Seriously.

[tr027 0]

Found this also:

http://www.paragliding-tales-and-reviews.com/porosimeter.html

"It seems the industry standard for paragliding, and possibly other air sports as well, is the JDC Mk-1 made by JDC Electronic S.A., a Swiss company. I've seen prices anywhere from around $1100 through to $1500. Their simple-to-operate meter measures the time it takes for 0.25 liters (0.0088 cubic feet) of air to pass through 38.5 cm² (5.97 in²) at 4 hPa (10 mb) of pressure. The time obtained then has to be converted to the standard units of liters per square meter per minute to get a permeability score. Here's some more specs.

* size: 150mm diameter cylinder, 230 mm high (6.0 inch diameter x 9.0 inch height)
* weight: 2.3 kg (5.1 lbs), 3.1 kg (6.8 lbs) with case
* accuracy: +/- 2% claimed, but actually not quite that good with cloth material
* power: replaceable lithium battery, 30000 working hrs (included and installed)
* warranty: 2 years
"

"The evil of the world is made possible by nothing but the sanction you give it. " -John Galt from Atlas Shrugged, 1957