question about "space Blanket"

Posted by: traceur84

question about "space Blanket" - 01/08/08 10:59 PM

I have been researching making my own gear for awhile. I read about a sleeping bag you make with two "space blankets" does anyone have any idea if it would work.I mean it would be light but would it be warm
Posted by: JAK

Re: question about "space Blanket" - 01/09/08 04:54 AM

Are you planning on using anything for insulation in between?

As layers go, there are lighter alternatives. Unless you would otherwise be naked, the advnatage of the reflective surface is over-rated. If you plan on any sort of tree or tarp overhead the reflective surface becomes fairly redundant. Multiple shell layers are still useful, but unless you get a shell layer less than 0.33 oz per square yard even synthetic insulation is more effective. I try and keep shell layers to a minimum and focus on insulating layers. As a general rule I think all of your insulation should outweigh all of your shell layers in all your gear and clothing. Also I think the insulation should be a healthy mix of wool, synthetic, down, and closed cell foam.

I think those emergency blankets are more than 0.3 oz per square yard. The only thing I know of that might make multiple layers interesting with just some minimal batting in between would be that Cuben stuff. Still, by the time I inlude my own skin, my wind layers, my two sleeping bag shells, and my poncho/tarp I think I already have enough shell layers.
Posted by: Dryer

Re: question about "space Blanket" - 01/09/08 06:33 AM

Are you talking about that shiny mylar sheet "space blanket" you can buy at Walmart? Or the 'emergency rescue blanket" things that are mylar with a little insulation between the layers maybe?

I use the cheap mylar sheet 'blankets' to block wind and create minimal dead air space under my hammock, which works fine. I've used it as ground cover too, but it doesn't last very long, is really noisy, and shreds after a few nights. I consider the "thermal reflective" attributes of the stuff worthless except as a big light reflector...I've rolled the blanket ends onto my trekking poles and made a HUGE signal mirror, which actually worked well! I carry one or two of the things in my pack for their utilitarian value....but......
Making a bag out of it would make a noisy, unbreathable, nightmare unless you figured out a way to vent or perforate the stuff. Nope, I wouldn't waste my time with it, but you might come to other conclusions.
Posted by: Earthling

Re: question about "space Blanket" - 01/09/08 10:33 AM

Good points JAK and Paul.

My problem would be lack of insulating value, noise, and lack of breathability with 'space blankets' as a whole.

There are many types of 'space blankets' now on the market; and one must clarify the specific one they are posting about to get any reansonable answer IMO. For instance there are the cheapo flimsy, tear if you look at it twice type that are solely one use types. Yes, you could get more than one day's use from one if careful, but you cannot predict a sudden wind gust shredding it against something. So you cannot trust this type in the field for extended use IME.

The next type are the AMK type, which are much stronger; though a bit on the small side to me. They have a shiny side and an orange side with printed outdoor tips on it. These I've used for season long use without any issues, and always pack one. 3.5oz IIRC.

The third is the most, IMO, robust of the bunch but weighs in at 12ozs in 5 x 7ft. It's the 'All Weather Blanket' by MPI Outdoors from NH. It's a multi layered fabric blue on one side and reflective on the other. Again, this is a smallish one to use as a tarp, or tarp and ground cover to sit on in fornt of a small cookfire IME. If they made a 10 x 10FT it would weigh more than a pound and a half IMO and negate it's intended usefulness. It does make a good Winter ground cloth, have'nt tried it for wrapping under my hammock as of yet. Pretty stiff, so that would be the issue for conforming under a hammock IMO.

There is a 'Space Blanket' sleeping bag marketed in the mylar film, at least I have one, still in orginal package; that is for emergency bivy use IMO. You'd have to jump in near nekked <img src="/forums/images/graemlins/blush.gif" alt="" /> in order to not wet out your clothing, and it has no foot vent, though that's easily solved <img src="/forums/images/graemlins/smirk.gif" alt="" /> It would be a one time use thing as it would be thin, fragile and bulky after the first use not to mention wet <img src="/forums/images/graemlins/tongue.gif" alt="" /> it's there if I want to fill it with leaves and make a matteress someday <img src="/forums/images/graemlins/grin.gif" alt="" />

Insulation must be thick enough to prevent convection of air currents to keep you comfortable.
Posted by: finallyME

Re: question about "space Blanket" - 01/09/08 01:35 PM

it's there if I want to fill it with leaves and make a matteress someday <img src="/forums/images/graemlins/grin.gif" alt="" />

Insulation must be thick enough to prevent convection of air currents to keep you comfortable.

That just gave me an idea, for an emergency bivy. Use one spaceblanket bivy (the closed bag type, not the flat sheet type). Then either use a breathable, thin bag, or nothing at all. Put the thin bag inside the spacebivy, then stuff leaves inbetween to form a thick insulative layer. Or, just stuff leaves inside the spacebivy and get in without the other layer between you and the leaves. Obviously only good with leaves or pine needles around. If it is winter with snow, you could pull the needles off the trees to form the insulated layer. Again, emergency only idea. Any thoughts?
Posted by: Earthling

Re: question about "space Blanket" - 01/09/08 02:20 PM

Yeah, I've done this a few times over the past 30 years and you don't want sticky softwood pitch near ANY gear you intend to keep <img src="/forums/images/graemlins/tongue.gif" alt="" />

That and I prefer to load my SB with leaves and sleep above it so as not to rise a' drippin' in sweat <img src="/forums/images/graemlins/frown.gif" alt="" /> If the humidity is low enough below say 45F I have gotten into it with a slash cut foothole in the footend of the SB. Also, some boughs of softwood laid under the SB is more comfortable than being in it with them IME. I have slept in one that had leaves layered in between another and it did suffice but was noisy as heck if you did'nt sleep like a log <img src="/forums/images/graemlins/tongue.gif" alt="" /> And in the AM there was no ground cushioning left due to crushed leaves. All practiced in Late Spring early Fall <img src="/forums/images/graemlins/smirk.gif" alt="" />

Other than that you have a great idea <img src="/forums/images/graemlins/smirk.gif" alt="" />
Posted by: finallyME

Re: question about "space Blanket" - 01/09/08 02:32 PM

Well, like I said..emergency ONLY. This is where you throw out LNT and try to stay ALIVE. <img src="/forums/images/graemlins/crazy.gif" alt="" />
Posted by: cheap

Re: question about "space Blanket" - 01/09/08 06:27 PM

Let's stay on topic! He doesn't wan't to use it as a "blanket", he wants to stick two together at the edges to make a sleeping bag. I have heard of articles on these, but you would have a major problem with sweating.

when you sweat, your body is saying it's too hot so it tries to cool down. But trapped inside a thermal blanket sleeping bag, instead of evaporating,like normal, it would make your clothes damp and would make you cold, and, quite possibly, make you very uncomfortable when you wake up in the morning.

If you poked a couple holes at the bottom of the bag, it might help with ventilation. I hope this helped. <img src="/forums/images/graemlins/laugh.gif" alt="" />

Posted by: Trailrunner

Re: question about "space Blanket" - 01/10/08 03:13 PM

I read about a sleeping bag you make with two "space blankets" does anyone have any idea if it would work.I mean it would be light but would it be warm

What do you mean by the word "work"?

Will it keep you alive in an emergency? Maybe.

Will it keep you just as warm and comfortable as a real sleeping bag? Definitely not.

You have to give something to get something. Everything is a compromise. This "sleeping bag" is on the extreme end of the spectrum where comfort is all but eliminated to save weight and cost.

It sounds like a great idea to long as I don't have to sleep in it.
Posted by: TomD

Re: question about "space Blanket" - 01/10/08 09:04 PM

This exact same topic came up a couple of months ago.

Space blankets and bivys are designed for short-term emergency use. If this was a good idea, companies would be making and selling them for long term use. There are reasons they don't.

If you want to find out firsthand how this would perform, make one using a couple of blankets and duct tape and see for yourself.

There are many threads here on sleeping bag design and physiology. I suggest you read back through them for a better understanding of how a bag works and what your body is doing while in one.
Posted by: Earthling

Re: question about "space Blanket" - 01/11/08 04:29 PM

Weather anomalies do not make the use of this rig a 'safe' bet for a night's sleep. As a backup rig it's even a hassle at best; i stated my uses and trials with it.