breathable bivy
Posted: 10 September 2007 04:06 AM   [ Ignore ]  
Member
RankRankRank
Total Posts:  11
Joined  2007-06-08

so, I’m thinking about making a bivy like the Bozeman Mountain Works ones.  How would Momentum work for the top as far as being water resistant enough to be worthwhile (my down quilt has a 1.1oz teflon dwr shell) while still being breathable.  any advice?

Profile
 
 
Posted: 10 September 2007 04:26 PM   [ Ignore ]   [ # 1 ]  
Administrator
Avatar
RankRankRankRank
Total Posts:  432
Joined  2007-05-07

Momentum is the best thing going for those light-duty splash type bivies right now.

It’s a tough call, though.  You’ve already got a very water resistant top on your quilt as it is.

If you made your quilt with hydrophobe thread and already have that teflon dwr shell, I doubt that you’d get much from a momentum overbag in terms of water resistance.  And in fact, any time you add another layer of fabric, no matter how breathable, you increase the likelihood of condensation.

On the other hand, the places where an overbag shines are for
a) air infiltration mitigation for quilts.  this is a big deal and the primary attraction of an overbag, not water resistance. Sometimes people like to tout some degree of extra warmth, like 5 or 10 degrees, but much of that comes from retaining vapor as well as heat.  I’d much prefer to get an extra 10 degrees with a little big more loft than with an extra layer of fabric.
b) bug protection

I have considered making
a) a down quilt with a momentum liner and nanoseeum shell
b) a synthetic quilt with a momentum liner and a nanoseeum shell, or no shell at all
to be used in conjunction with an overbag like you’re talking about.  But you can tell from what I’m considering that I do believe that breathability (and also of significance, weight) is significantly impacted by additional layers of fabric.  Even if it were perfectly breathable, the extra layer of nanoseeum would add around 2 oz of extra weight over what a straight quilt or 3 oz more than a traditional down bag.

It’s tough to keep this reshuffling from turning into a zero-sum game.

AYCE

Profile
 
 
Posted: 11 September 2007 02:53 AM   [ Ignore ]   [ # 2 ]  
Member
RankRankRank
Total Posts:  11
Joined  2007-06-08

so, you’re thinking of making the outside shell out of nanoseeum, such that it has to be used with a bivy?  especially with a synthetic, that would be neat to try, but then why not just build the dwr shell into the quilt like normal and save the weight….

I wonder, how about making a silnylon bivy-type floor and hood that somehow hooks or straps on to the quilt to seal out wind and bugs….  perhaps the velcro or straps necessary to do so would weigh almost as much as the top shell would.  The trick would be making a light design that fully seals out the wind without negating the variable-girth of the quilt.

Profile
 
 
Posted: 12 September 2007 02:23 PM   [ Ignore ]   [ # 3 ]  
Administrator
Avatar
RankRankRankRank
Total Posts:  432
Joined  2007-05-07

so, you’re thinking of making the outside shell out of nanoseeum, such that it has to be used with a bivy?  especially with a synthetic, that would be neat to try, but then why not just build the dwr shell into the quilt like normal and save the weight….

Right- the idea is that it’s
a) most effective to draft seal with an enclosure like an overbag (or of course a sleeping bag, bottom insulated or not), especially if the user does not sleep like the dead.  But the I-gotta-vent crew would be pretty bitter about something enclosed like an (over)bag, especially one without a zipper.

b) important to eliminate redundant layers of fabric for breathability and weight reasons

AYCE

Profile
 
 
   
 
 
‹‹ Sewing Info      quilt pattern ››