> I invented a $.01 windshirt tester (paper coffee filter air permeability reference) that is MUCH more accurate than just blowing through fabric to determine if it is easy or hard....a double layer paper coffee filter will provide the near optimal 35 CFM air permeability...a single layer paper coffee filter will provide ~70 CFM.
Thank goodness...never liked the Vader test, too much variability for my taste. (Not to mention the *actual* taste of new jackets, and the withering looks I get from staff as I breath-test jackets at REI).
Someone here at BPL had the idea of using a spirometer (lung capacity tester) as the dependent variable for a home permeability tester. I already own one, along with an air compressor that can yield a constant, repeatable amount of air-- so would like to try it. But I don't have swatches of fabric of known permeability, so my ability to calibrate has always been missing.
If I'm reading Richard correctly, he just solved my calibration problem. One coffee filter 70 CFM, two 35, and by extrapolation three 18, and four, 9 CFM. Yes?
EDIT: Sorry for the thread derail, I'll open a new thread for this. Please carry on re Patagonia.