Hi David, I think you have the physics of how the wind affects the insulation a bit backwards. Wind does not add cold, it removes heat. And it does not have toMessage 1 of 57 , Sep 2, 2003View SourceHi David,
I think you have the physics of how the wind affects the insulation a bit
backwards. Wind does not add cold, it removes heat. And it does not have to
blow into the insulation to do this, it only has to remove the layer of air
that was warmed up by the insulation that your body warmed up.
Your body heats up your first layer of insulation, and the air between you
and that layer. Your body will try to heat that layer up till it is the
same temperature as your body. That layer will then try and heat up
everything around it so that it is the same temperature as that first layer
of insulation. That includes you other sections of the same layer, and the
next layer out, as well as the air that surrounds it. This process
continues on out to your outermost layer of insulation and then out to the
air that surrounds it. Each layer will be a little colder than the one in
closer to your body.
You are in effect generating your own bubble of heat. this bubble actually
extends several inches below your hammock into the night air, even with a
very good pad. Any time that the wind blows anywhere into your bubble it is
blowing away part of that bubble and your body needs to generate more heat
to reform that bubble. So the wind is not blowing cold into the closed cell
pad, it is removing the air that the pad warmed so that the pad has to warm
another layer of air before it reaches some sort of equilibrium.
If you were to put a windproof silnylon barrier right up against that
closed cell pad that was losing heat, it would make only a very minor
difference in your warmth. On the other hand, blocking the wind from
penetrating a down garment would make quite a difference in how warm it
will keep you.
The goal of your windproofing efforts should be to keep the wind as far
from your insulation as possible, not just to keep it out of your
insulation. The advantage to the skirt and cone ideas is that they protect
the outer air layer of your heat bubble. I think that changing the way you
look at how the wind affects your insulation should help out with your
As for the condensation issues, I think that having a breathable hammock
will help with them, but it is not completely necessary. You need
convection, but the source of the air does not necessarily have to come
through the fabric. You might even be able to come up with some sort of
venting system through the hammock. But going with non-breathable fabric
means coming up with a more difficult solution, so I think your experiments
are leading in the right direction.
Looks very nice. _____ From: Chet Clocksin [mailto:firstname.lastname@example.org] Sent: Friday, September 12, 2003 5:55 AM To: email@example.com IMessage 57 of 57 , Sep 12, 2003View Source
Looks very nice.