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LAND-Shark Emergency Survival Bag - Experience? or Reviews?
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Moe Dog
(moedog56) - F
Re: Re: Re: Re: Re: Weight concious solution on 11/16/2006 13:43:22 MST Print View

The makers of the Space Blanket claim that 38.5% of body heat loss is attributable to radiation.

So are they just full of sh--? (Supposedly results from U.S. Army Laboratories). Or is this only when the outside temperature is 40 below zero? It would seem that even with a thick sleeping bag, IR thermal imaging could still detect radiant body heat... hence, radiant heat loss?

Would love to hear more technical discussion on this...

David Wills
(willspower3) - F
Re: Re: Re: Re: Re: Re: Weight concious solution on 11/16/2006 14:37:10 MST Print View

In statistics class today, my teacher said "everything in statistics is wrong, but it is the best we can do" (we did probabilitie statistics, but it was a blanket statement concerning all guessing equations). He then proved to us just that by showing an example where the answer was 40% (the real answer) you get by counting. Then, with using the appropriate formula, he got 36.5% for an answer. As a marketing major, I have seen a huge number of examples where these statistics can be made in any kind of numbers you want them to. MPI is using the most biased statistics they can find from a 'reliable' source in order to further their product. They used a study (in unknown conditions) that had radiative heat loss first, probably because that is what most people think of space blankets as helping with. They put VB layer 3rd probably because people consider it uncomfortable to be clammy, even though it is, IMHO the space balnkets 2nd best (just due to the nature of all my other gear that is windproof)warmth retaining feature. I wouldn't put much stock in what they say, especially considering convective heat loss varies at any given moment. They didn't even consider the conductive heat loss required in sleeping situation to warm a sleeping pad or the ground. There is no exact equation that can predict real life radiative heat loss in a backcountry situation. there are too many variables. But, it is a presence, small, but still there, and can be helped by reflective layers.

A few question to ponder concerning the position of reflective layers and loft:

Would your clothes radiate heat if they were warmer than the next layer up?

How much of the heat your clothes radiate would be captured vs. being transfered by the reflective bags radiative heat loss (being wamer than the next layer up)?

Would a 20* sleeping bag radiate heat if it was warmer than the air around it, due to your body heat?

A good something to ponder. I have a boring class to go to now, so I will have plenty of time to think :)

Edited by willspower3 on 11/16/2006 15:15:38 MST.

Moe Dog
(moedog56) - F
Re: Re: Re: Re: Re: Re: Re: Weight concious solution on 11/16/2006 15:21:42 MST Print View

Sure, I'm not putting too much faith in the accuracy of that percentage. However, I do think that radiant heat loss could be more of a factor than what most people (hikers / gear developers) consider. There isn't too much gear on the market with radiant heat barriers to test this.

Convective and conductive heat loss are both fairly easy to combat with current gear. Evaporative heat loss requires a little more education to comfortably handle and far fewer manufacturers employ this. Yet radiant heat loss gets dismissed quite rapidly (view the previous comments).

Why is that every insulated lunch box has some type of foil/refective liner? Why is that Domino's delivers their pizzas in insulated packs that are foil/reflective on the inside. Why are the better insulated homes now constructed/retro-fitted with foil/reflective radiant heat barriers?

Just looking at the heat loss/gain differential of residential buildings to the outside temperature is nothing like that of "a flame". Yet radiant heat loss IS a significant factor. In fact, the temperature differential in that scenario is the same for a hiker: comfortable (room) temperature in relation to uncomfortable (outside) temperature (too cold or too hot). The actual "delta T" is not huge, but not so small as to be dismissed.

Brett .
(Brett1234) - F

Locale: CA
snugpak uses reflective material in sleepingbag on 11/16/2006 18:36:46 MST Print View

Jason, at least one company (I know of) uses a partial radiation barrier in their sleeping bags- Snugpak. I own two of them and while they are not SUL, they are warmer than you would guess based on loft:

"Reflectatherm layer - "Space Age technology in a down to earth application."
This metallised fabric is designed to reflect heat and retain warmth. A highly breathable material, which adds little to the weight or packsize of the product and provides at least 15% additional warmth whilst being undetectable by touch in the sleeping bag or garment."

Moe Dog
(moedog56) - F
Re: snugpak uses reflective material in sleepingbag on 11/16/2006 21:34:04 MST Print View

Thanks, very cool. Stephenson's Warmlite is the only other one that I know of (besides the aforementioned HotSac by WM). Nice to know that this radiant barrier concept may be catching on.

David Wills
(willspower3) - F
Re: snugpak uses reflective material in sleepingbag on 11/16/2006 23:02:11 MST Print View

I would love to get hold of some of that reflectatherm for quilts when a VB is too clammy.

Joshua Mitchell
(jdmitch) - F

Locale: Kansas
Radiative Heat Loss CAN be dismissed in adequately insulated backcountry on 11/17/2006 07:32:49 MST Print View

Okay, it's about time for me to chime in...

Some points about radiant heat loss

1) Radiant Heat Loss / Gain does NOT happen through opaque material, period (well... there are probably some crazy materials but those are way exotic).
2) Radiant Heat Loss / Gain happens across distance separated by empty space (or air filled space)
3) The 'delta T' involved is the two surface temperatures that are separated by empty space.

AKA The ONLY place you can have radiant heat loss be significant is when you compare the outer surface of your sleeping bag to the inner surface of your shelter (everything else is touching or close enough to touching that convective / conductive more than dominates). If you have prepared your gear adequately, this delta t is essentially zero.

Quick and easy test... take your hand out of your sleeping bag, 'feel' the outside surface then 'feel' the inside surface of your shelter... I'd bet dollars to donut that, if you have an adequately rated sleeping bag, both are going to feel cold (aka zero delta T).

Note, this also explains why you can feel colder sleeping under the start than in a tent... in that case you're comparing your sleeping bag to the coldness of outerspace... however you don't need a 'reflective barrier' to block this you just need an opaque barrier.

Edited by jdmitch on 11/17/2006 07:33:27 MST.

John S.
(jshann) - F
Re: Radiative Heat Loss CAN be dismissed in adequately insulated backcountry on 11/17/2006 07:47:56 MST Print View

I saw an older physiology textbook stating that lining garments with gold was good for reflecting heat. It mentioned that these garments enabled Arctic expeditions to carry less weight in clothing. Does anybody know anything about this?

Joshua Mitchell
(jdmitch) - F

Locale: Kansas
Reflective Lining in Clothes on 11/17/2006 09:50:12 MST Print View

"I saw an older physiology textbook stating that lining garments with gold was good for reflecting heat. It mentioned that these garments enabled Arctic expeditions to carry less weight in clothing. Does anybody know anything about this?"

It might add some benefit, however the added benefit from radiant heat transfer blockage is likely overstated. The reason it might add benefit is that, during movement the clothes are not likely to be right against the explorers skin it would reflect radiant heat back to the skin... however realize that this would only happen when the insulation is less sufficient.

However, I suspect that the actual benefit was that, in order to reflectivize the fabric they likely needed to make it a tighter weave resulted in more wind-blockage and it acted as a semi-VB.

Edited by jdmitch on 11/17/2006 09:51:40 MST.

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: Radiative Heat Loss CAN be dismissed in adequately insulated backcountry on 11/17/2006 10:12:11 MST Print View

Not the Antarctic, but...

a sister division of the company i work for makes the NASA astronaut's space suits. An ultra-thin metallic layer is used in the suits to keep out radiant heat and reduce the cooling requirements of the suit.

David Wills
(willspower3) - F
hmm on 11/17/2006 21:16:15 MST Print View

From what I have gathered, the use of reflective layers would only be useful in emergency situations when underinsulated (stand alone summer bag, or my 40* quilt in 30* nights :), my plans to begin with), or as a tarp to reflect significant heat gains from a fire to the body, or in the summer to reflect the sun away for coolness. Sounds like its pretty versatile nomatter what time of year it is though. It'll be a fun test to see how low I can go with this reflective VB bag in my 40* quilt.

"If you have prepared your gear adequately"- now what's the fun in that?

Edited by willspower3 on 11/17/2006 21:20:53 MST.

Jennifer Looy
(canyousurvive) - F

Locale: California
Re: LAND-Shark Emergency Survival Bag - Experience? or Reviews? on 10/07/2010 18:22:46 MDT Print View

Good Afternoon Backpacking community,

My name is Jennifer Looy, I am the daughter of the inventor of this product. I was reading though everyone’s reviews and comments in regards to the Land/Shark product. I appreciate everyone’s honesty and welcome any questions or feedback in regards to the product.

To answer your questions:

Has anyone USED THIS?
I have had personal experience with the product in instances of land (backpacking in Montana) and water use of this product (FAR 135.331 Crewmember Training Class, Pool Demonstration.) See below for additional comments.

Ever seen it in real life?
Yes, I aided in the manufacturing of this product.

How durable did it seem?
The bag is intended for one use ideally. As I am beginning to gather the general backpacking community would prefer a more durable product that could be used in multiple instances. Although the material is strong it would not be ideal for multiple uses. The inventor of this product initially wanted something for water emergency situations.

Was the material quiet?
Its is not loud like one of the crackly space blankets, but it not completely quite either. When getting into the bag you will be heard. Once settled into the bag it is relatively easy to keep quiet.

What situation did you use/intend for?
My experience with the bag on land is as follows: During my experience we ended up using the bag for a heli-vac of one of our team members who took a bad spill down a snowy mountainside. We thought she might have back or neck injuries. We had to keep her on as flat of a surface a possible so we took turns digging a ramp down to a place where the helicopter could land and sliding her slowly down on the land shark in this instance it was slick enough that it acted as a nice sled. After the bag had been used we ended up just messing around with it. We cut it up and made snow boots. Seeing as we tried our best to dry out our snow boots during the night. We used it to carry water, etc.

My experience with the bag in a water situation is as follows: We host a FAR 135.331 Crewmember Training Class for the Pilots and Flight Attendants of the Corporate Aviation Industry. Its is a class taught by Tim Kneeland (who has a long resume mostly involving SERE and various other survival techniques, obviously in the instance of Corporate Aviation he teaches people how to survive while trying to do things to be found.) At the end of the class day we do a demonstration with life vests, a life raft, land/shark, and various other ways of keeping afloat and alive in a ditching situation. I take the course every couple of years. After donning a life vest you open up your land/shark and get in it water and all and then you do your best to assume the fetal position or any other non moving position. The goal of both the land/shark and the exercise is to show people how much water takes heat away from your body. As soon as you get into the land/shark and stop moving you can feel a layer of water almost stick to your skin and begin to warm. You feel warm as long as you are doing your best not to move and there is no current over your skin.

I apologize for not being the most articulate person, but I hope that some of my words have answered your questions.

Warm Regards,

Jennifer Looy
Corporate Air Parts, Inc.