Topic

DIY Air Permeability Tester


Forum Posting

A Membership is required to post in the forums. Login or become a member to post in the member forums!

Home Forums Gear Forums Make Your Own Gear DIY Air Permeability Tester

Viewing 8 posts - 1 through 8 (of 8 total)
  • Author
    Posts
  • #3460607
    Lance M
    BPL Member

    @lancem

    Locale: Oregon

    Placeholder

    #3460609
    Lance M
    BPL Member

    @lancem

    Locale: Oregon

    The recent topic “A good alternative to WPB gear for ACTIVE backpacking” inspired me to complete a DIY air permeability tester that’s sat unfinished on a shelf.

    My original interest in doing this was to compare common LS travel shirts with wind shirts and perhaps make a long sleeved, hooded, button front sun/bug/wind shirt.

    So far the results have been repeatable and encouraging.

    The vacuum source is a Shop-Vac. The amount of vacuum is read directly from a liquid column manometer. Because the Shop-Vac is not positive displacement, it doesn’t generate much vacuum as air flow increases.  I’m limited to 1” water column, given the size of the test heads and the sensitivity of the flowmeter.

    The volume gauge is a Dwyer 0-200 CFH variable area flowmeter. The gauge is marked in increments of 20 CFH.  I interpolate to the nearest 5 cfh and divide by 60 to get CFM.  I need a second, more sensitive gauge for fabric with low (<15 CFM) permeability.

    There are two test heads; one 7.26 sq. in. (shown) and one 3.14 sq. in.. The larger test head is for less breathable fabric and the small test head (not shown) is for more breathable fabric.  A little math yields CFM per square foot.

    The base:

    The bottom half of test head:

    Ready to test:

    Reading results:

    Table of results:

    I do not know what the ASTM (D737) standard is for pressure differential between the two surfaces of the fabric. One reference prefers .4 to 10 inches of water with .5 minimum.  I used one inch.  Until I can find a definitive answer, my measurements are just relative amongst themselves.

    There are a lot of variables not taken into account: altitude, humidity, atmospheric pressure, latitude, time of day, favorite color, etc, etc., but I’m OK with that.

    Hope this has been interesting,

    -Lance

    #3460713
    Roger Caffin
    BPL Member

    @rcaffin

    Locale: Wollemi & Kosciusko NPs, Europe

    Seriously interesting stuff!
    Go for it, and publish.

    Cheers

    #3460732
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    Nice!  Amazing what you can do relatively cheaply.

    I like the 1 coffee filter/2 coffee filters comparison – some validity to your setup

    #3460778
    Lance M
    BPL Member

    @lancem

    Locale: Oregon

    A few more tests:

    .

     

    #3460787
    Richard Nisley
    BPL Member

    @richard295

    Locale: San Francisco Bay Area

    Lance,

    Excellent work!

    The 35 – 70 CFM range appears to be reasonably close. The low and high ends could benefit from additional calibration tests. This may help with your calibration. It is material that you may already have, or is cheap to acquire. My commercial system is accurate to .01 and here are some examples of my low-end test results.

    Rockwoods EMN-Coyote Brown Nextec Epic = .14
    Tyvek 1422R = .15
    Green Driducks Poncho = .33
    Blue O2 Rainwear Jacket = .33

    These Polartec values are accurate to calibrate your high-end.

    Polartec 100 = 254
    Polartec 200 = 325

    #3460859
    Lance M
    BPL Member

    @lancem

    Locale: Oregon

    Richard,

    Thanks for the calibration references.  Any chance you have a number for Thru-hiker M90MR (October 2014 vintage)?

    “My commercial system is accurate to .01”

    Whoa! I’d be pleased if mine is within 10%

    I have a new gauge on the way which should extend my low end testing.  In the meantime, I might experiment with pressure differentials.

    Thanks again.

     

    #3460907
    Richard Nisley
    BPL Member

    @richard295

    Locale: San Francisco Bay Area

    Lance,

    I tested the M90 2013 version offered by Thru Hiker in Ski Patrol Red. TH listed it as M90 V3. It tested 11.31 CFM.

Viewing 8 posts - 1 through 8 (of 8 total)
  • You must be logged in to reply to this topic.
Forum Posting

A Membership is required to post in the forums. Login or become a member to post in the member forums!

Get the Newsletter

Get our free Handbook and Receive our weekly newsletter to see what's new at Backpacking Light!

Gear Research & Discovery Tools


Loading...