[pct-l] Bag/Quilt Warmth

[ned at mountaineducation.org]

Fascinating, Steel-Eye! Thanks for the stats, however believable...

This was just a thought. Would it be unreasonable to assume that a "10-degree" bag at the start of a PCT thru hike would become a "30-degree" bag by the time (a month, say) the hiker reached KM?
 

"Just remember, Be Careful out there!"

Ned Tibbits, Director
Mountain Education
South Lake Tahoe, Ca. 96150
    P: 888-996-8333
    F: 530-541-1456
    C: 530-721-1551
    http://www.mountaineducation.org
  ----- Original Message ----- 
  From: CHUCK CHELIN 
  To: ned at mountaineducation.org 
  Cc: pct-l at backcountry.net 
  Sent: Tuesday, July 26, 2011 1:12 PM
  Subject: Re: [pct-l] Bag/Quilt Warmth


  Good afternoon, Ned,


  The PCT Hiker’s Handbook section on sleeping bags, Jardine’s paragraph on Loft Degradation says: 
  “Reduction of loft is a major consideration with sleeping bags.  The first time you ram pack your new sleeping bag into its stuff-sack it loses perhaps 8% of its loft.  Forever.  Those imprudent enough to use a compression sack can bid an additional 10” goodby.  That 18% loss is the damage incurred during the first occasion.  Add another 3% for each subsequent hyper compression.” 

  Following his stuffed-but-not-compressed formula, a down bag with 3” of loft would be 2” thick after 12 days, 1” thick after 34 days, 0.25” thick after 81 days, and less than 0.03” thick at the end of a 150-day hike.  Add the compression loss everyday and the final thickness becomes 0.02”.

  Like much of what Jardine writes I believe only about half.  While I certainly agree that compression, or even stuffing, is a bad idea I don’t believe his percentages.  I suspect Ray pulled those numbers out of his exhaust system to illustrate a point.  I don’t have actual thickness reduction numbers based upon experience, but my impression is the loss will be more like 25% over 100-150 days of having been moderately stuffed. 

  Steel-Eye

  -Hiking the Pct since before it was the PCT – 1965

  -http://www.trailjournals.com/steel-eye

  -http://www.trailjournals.com/SteelEye09




  On Tue, Jul 26, 2011 at 11:26 AM, <ned at mountaineducation.org> wrote:

    Here's a related question...

    Has anybody thought about how a bag used from the start, about a month in at
    KM, since it has been compressed daily for all that time and gotten dirty
    and oily during nightly use, will have a worse temperature rating than when
    they started and this is at the very place where hikers need a bag rated for
    colder temps as they go up into the high sierra snow?

    Might be a good place to bring in a new, colder rated bag?

    Have any previous thrus noticed that they were sleeping colder once they
    left KM and before they hit the snow because the nighttime temps were colder
    there?



    "Just remember, Be Careful out there!"

    Ned Tibbits, Director
    Mountain Education
    South Lake Tahoe, Ca. 96150
       P: 888-996-8333
       F: 530-541-1456
       C: 530-721-1551
       http://www.mountaineducation.org