by Bushcraft-Joe » Sat Jul 10, 2010 7:28 pm
Yeah an underblanket is like half a sleeping bag that attaches to the underside of the hammock, the thorey is..
when you lie on a sleeping bag you compress the insulation making it next to useless, on the ground you use a sleeping mat to compensate for this, in a hammock most people don't bother, but they soon find that it can get cold at night as the cold air is blowing accross their back and removing body heat.. SO.. in steps the Underblanket.. clip the blanket to the underside of teh hammock, and you instantly add the insulation you lost from compressing your sleeping bag, plus you have an area of warm air trapped below you.
the blanket should idealy be water proofed and to a good degree wind resistant, to minimise loss of heat. When using this system you can reduce the size of sleeping bag required and therefore the amount of weight and pack size.
hope it helps you