Measuring cloth porosity

Design Insight: A better way to measure porosity

“We should be measuring flow, not time.” Bastienne Wentzel explains why

20 January, 2025, by Bastienne Wentzel

Porosity is one of the main properties that should be checked when your paraglider or paramotor wing gets its periodic inspection. 

Porosity is a measure of how much air leaks through the fabric. It is usually given in seconds. If the air flows through the fabric too quickly, the glider has aged a lot and its flying properties deteriorate. Anything above 100 seconds is considered fine. At 25 seconds we should start to take notice and be aware and 10 seconds or less means we should not fly the glider anymore.

Porosity is also often used as a measure for ascertaining the secondhand value of a glider. And that is where problems in understanding can arise, says Fred Pieri, designer at Ozone. 

It may seem simple to understand: let’s say a new glider gets a value of 1,000 seconds and after one year it gets 500 seconds. Another glider has a porosity value...

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