I learned a trick about 10 years ago. This of course won't work to keep you warm when your in your boat fishing but it sure keeps you warm at night. I don't have a camper with a furnace, instead I sleep in my van.... it can get really cold in the winter time so a friend showed me one year to put a rock about the size of a volleyball on the edge of the fire.... leave it there till about half an hour before you go to bed.... take the rock out and leave open to the air to cool down a bit. The rock will actually glow red so it must cool for a bit. After it is not glowing red anymore, wrap it in newspaper and put it in a pillowcase. You can put it in your sleeping bag and it will stay warm all night. In fact after all the guys saw me do this the first night they all started to tease me the next night saying.... "Hey Steve.... you better go get your rock to heat up in the fire." Well, believe it or not but when I went to my sleeping bag to get my rock to heat up for the night to my surprise and everyone else's, the rock was still warm almost 24 hours later. The next year when we all got together people were saying..... oh, your the guy that sleeps with the hot rock.... this trick works great..... try it, you might be surprised at how well it works..... Steve.