Dear all, as a new bod from england who is very keen to try out this lightweight, home sewn business, I've been fascinated to trawl everyone's input to this forum. It's delighted me to see so much creative energy and advice being shared so freely.
I'm trying to design a lightweight sleep system for myself, based on a poncho tarp and a synthetic quilt, and I was hoping that someone could give me some pointers about how best to manage condensation.
I was impressed by David Willis' quilt project with it's unbroken layer of water resistant momentum fabric on top- http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/4439/index.html - , and thought this sort of design, combined with a generously sized tarp would allow me to dispense with a bivvy sack. But I am worried that this approach will simply move the location where the air reaches dew point to inside the quilt, between the top fabric and the insulation. Only experience will tell me if this is the case, and having none of my own, I'm hoping to borrow someone else's. Any thoughts?
If a bivvy is needed, ( I would make the lightweight, semi-waterproof type, probably from momentum and sylnylon) should I still shell my quilt with a DWR fabric, or would this be just too much DWR between me and the outside air, creating excessive condensation?
My standard DWR shelled sleeping bag and heavyweight Gore-tex bivvy setup works by wicking moisture up to between the sleeper and the bivvy, and sleeper's DWR shell stops any excess sinking back down into the insulation. This would suggest the need for both a sack and a DWR shelled quilt. Or could I get away with a non-dwr upper on the quilt, leaving me totally breathable on fine nights where the bivvy stays rolled up in the sack?
I will use this setup in the UK, so low altitude, mild climate, but with westerly winds and a fair amount of rain.
I know this is a lot of questions, to which there will not be any definitive solution, but I would be interested to hear anyone's opinions, and would be grateful for any advice offered. Part of the obsession with detail is that we just don't have the supply of materials in this country, so I'm going to have to calculate my fabric requirements really carefully, and hopefully only pay one lot of postage from AYCE at thruhiker!
All the best,