A long time ago I discovered that if I put my bedtime hot water bottle in my crotch I stay warmer longer. I freely admit that this may well be psychosomatic but, hey, the net result is the same.
The geek in me just had to do the calculations:
32oz of water (2lbs) with a temperature drop from 210 deg F to 70 deg F represents a total heat loss of 280 BTU's which should be about equal to 70 kCal of food energy. So, not only does this little bottle of hot water help you start out warmer and keep you warmer through the night, it also reduces your food energy requirement.
That being said, I have always found it best when winter camping to drink plenty of hot, non-caffeinated beverages before turning in - warm milk with honey and butter is my favourite - as well as eating a bit of protein and fat - either a big chunk of cheddar cheese or a big chunk of dried salami or similar sausage. When you wake up to take care of the inevitable call of nature, a DISTINCTLY shaped bottle into which you can make a deposit is very handy.
I used to use HDPE Nalgene for my pee bottle and polycarbonate Nalgene bottle for my hot water/beverage bottle until the night my flashlight died and I discovered that TASTE is not the way you want to be telling these two apart!
I used this trick on the last scout campout. It was better than "hand warmers" and cheaper. I put the bottle between my feet for the first 30 minutes until they were toasty, then I put it mid thigh between my legs and slept warm all night. I'll use a bottle from now on. I could have used this trick as a kid, but water bottles were not as durable and water tight back then.
Hanging in the Ozarks
I have just recently started using a hot water bottle for winter camping. This January I was spending a night out with some buddies and I decided to try the HWB for the first time.I was impressed with how well it worked. I also used a pair of stick on hand/foot warmers on my behind to help nip the cold. I'll freely admit that was one of the best sleeps I've had in any hammock in a while. That Clark was a house of snores that night.
Gave this a try last night in my Aluminum Water Bottle which I stuffed into a wool sox. WOW! What a huge difference. No issues with cold at all.
Yesterday I bought a Nalgene on sale at Target ($7.99) to use for a hot water bottle.
It's great to learn so much on this site.
But Jesus often withdrew to lonely places and prayed. (Luke 5:16 NIV)
He said to them, “But now let the one who has a moneybag take it, and likewise a knapsack. And let the one who has no sword sell his cloak and buy one." (Luke 22:36 ESV)
While people are saying, “There is peace and security,” then sudden destruction will come upon them as labor pains come upon a pregnant woman, and they will not escape. (1 Thessalonians 5:3 ESV)
I'm gonna try this when I go out next. Thanks!