space blankets for insulation

[tmckay2]

if anyone has hammock camped before, you know that the underside can get very cold due to the material, the air, and the temps at night. its best to insulate it with something, and i was wondering if those space blankets (you know the super light weight reflective material that is water proof and radiates heat back to you) could be put under the sleeping bag and work to reduce the cold felt on the underside. or, will it be too thin?

[StagLefty]

It's probably better than having nothing under you but I'm not sure if it's enough if your in a bag ? I would think you may have to step up to a better pad under you. I have no experience in hammocks so I hope someone else can give you some real experience with this [Beer]

[rondog]

Go to Home Depot and get some Reflectix insulation. Basically two sheets of very small bubble wrap sandwiched between three sheets of foil. Google it.

[275RLTW]

Anything that will add a layer of air underneath you is best.

[rondog]

This stuff.... http://www.reflectixinc.com/basepage.asp?Page=Double+Reflective+Insulation&pageIndex=622

[jerrymrc]

Space blankets are great especially for car use. I carry 2 of them in the truck when we used to travel the Forrest roads in the winter.

Where they come in handy is as a first layer. I always have a cheap sleeping bag in the vehicle and the space blanket is additional. And my space blankets are not the tiny thing in plastic. they are the quilted ones the Army has and they do work well.

Look like this.

[gnihcraes]

Tried the space blanket under the bed matress pad for a year here in the house, didn't really notice much help reflecting heat. Nice and crinkly sound when rolling over though. :)

[2008f450]

I keep 2 space blankets in the go bag but i also keep a space bag. It makes a great liner for a sleeping bag and makes a decent cold weather rated bag work in colder temps. I agree they are best used as a first layer then add on top of it if you can.

[KevDen2005]

I am a huge proponent of spaceblanket and have used them on numberous occasions. I have a similar one to what Jerry has as well as the disposable ones (I like the silver/gold combo for easy use).

I have made shelters and lined them with the space blankets and feel they definitely helped warm me up.

I keep a couple in my truck, along with a poncho liner and cheap sleeping bag. I also keep a couple in my "go" bag as well as my backpack for camping that I often refer to as a "rescue pack."

[earplug]

The little thin film space blankets that is about the size of a package of kleenex do not hold up well.
We got stuck in a mountain hail storm and wrapped up in the things. They are very easily ripped.

[rondog]

So, there's two kinds of "space blankets"? The thin mylar-looking things and a military type? Where can a guy get the military kind? I need to get some to keep in my Jeep.

[StagLefty]

So, there's two kinds of "space blankets"? The thin mylar-looking things and a military type? Where can a guy get the military kind? I need to get some to keep in my Jeep.

I think you can find them at most box stores in camping dept. I carry the thin ones in my bags but have the heavier type in the truck all the time. [Beer]

[rondog]

Kewl, thanks! I'd resisted buying the mylar kind because they're so flimsy I figured they were worthless, but I didn't know there was a heavier military version. Them's what I need.

[Tim K]

Heat is transferred three different ways. They are:

Radiation - Like when you feel the heat from the sun or a fire

Convection - Moving air across a surface. A cold wind is an example of convection cooling.

Conduction - Contact heat transfer. Sticking your tongue to a flagpole in winter is a pretty good example.

Some combination of the three is at work in almost all situations. In the hammock illustration, heat will be transferred away from the sleeper primarily by radiation and convection. Conduction is not a significant issue because you are not sleeping on the cold ground.

Space blankets work primarily by limiting radiation of heat. They're marginally effective at limiting convection cooling, and totally ineffective with conduction. As a result, adding one will be better than nothing. Determining how much better is the job of a specialized engineer and a super computer.

[StagLefty]

I refuse to put a specialized engineer & a super computer in my BOB [ROFL1]

[68Charger]

I refuse to put a specialized engineer & a super computer in my BOB [ROFL1]

Technically, I'd have a specialized engineer carrying my BOB [LOL]

(as long as you don't specify the specialization of the engineer)

[tmckay2]

thanks for the replies. lets try to keep something in mind and help me formulate a good option for what i am looking for. sure, you could use a foam pad or something, even a fleece blanket, and those aren't off the table, but remember that these take up a significant amount of room (although they are fairly light). we want to minimize the weight and size which is why these small space blankets SEEM like a good idea. however, because they are so thin it does make sense that they would do little to stop convection. but, they are about the size of my hand and weight almost nothing. are they supposed to be disposable or is it simply that they are too flimsy to be used again? what are some other options?

i could make something that is super insulating, but large. i could make something thats not insulating but is small. the trick is finding a medium

[Tim K]

Actually, I think they'll do more than I may have led you to believe concerning convection heat transfer. They are wind proof so they should stop any evaporative cooling, and they will probably be much better than nothing. I'd try it before you rule it out.

[rondog]

Oh, this is for a BOB? I thought it was a camping question. Disregard my Reflectix suggestion, although that stuff would be great on the floor of a tent.

[tmckay2]

no its for camping but i rarely car camp, i usually back pack. so in other words, the lighter and smaller the better. thats why i even switched to a hammock. its insanely smaller and half the weight of a normal backpacking tent. probably half the size too.

[jerrymrc]

Some thoughts touched on this subject will lead to a new thread in a couple of days. [Coffee]