Nov 13, 2006 at 2:01 pm #1220206
Anyone had any experience with this product?…
Has anyone USED THIS? or ever seen it in real life? How durable did it seem? Was the material quiet? What situation did you use/intend for? etc. etc…
(Please, no opinions on using a bivy vs. other shelters – I’m perfectly capable of forming my own. No need for a discussion about pros/cons of a non-breathable bivy, either.)Nov 13, 2006 at 2:05 pm #1366994
@crazypeteLocale: Above the Divided Line
I would help you out but the only thing I could tell you that would not be an opinion are the specifications of the product.
How durable did it SEEM??
Was the material quiet??
What is it used for??
These are all questions that require an opinion for an answer, and since you are able to make your own opinions I don’t know why you bothered to ask them
I just looked at the site and I don’t even know why you would be interested. Essentially you are paying for a reflective coated nylon sack. It weighs 18 oz. Why not carry a real shelter for that weight?? Or you could carry a large roll of plastic for the same effect.Nov 13, 2006 at 2:50 pm #1367000
Ok, smarty pants. (I should have known I’d get flamed). I ‘re-worded’ it, so it doesn’t sound as harsh. Please try to understand the intent. Unfortunately, you did exactly as had hoped any replies would not: disrespect my “interest”.
As any ultralighter could attest, final weight of any product is not the ONLY consideration. Otherwise, we would all be using 2 oz cuben fiber packs because that is about as light as any pack could get!
Some of us try to think outside the box and look at gear for multiple uses, individual preferences/circumstances, and unique scenarios.Nov 13, 2006 at 5:50 pm #1367023
Doug Ritter seems to like it, which I would take to mean it is effective as an emergency/survival shelter:
“In my opinion, the toughest and therefore most reliable, as well as most versitile of these is the “LAND/Shark,” from Corporate Air Parts, which is designed for use both on land and in the water (as illustrated here). It can also be turned into a tarp by slitting the seams (see below). It is vacuum packed inside a very tough bag for protection from abuse in storage.”Nov 13, 2006 at 10:11 pm #1367066
That’s actually where I learned about it. He just didn’t have much to say about it. I would love to hear from someone on this forum who may have used it. Oh well, I’ll probably just plunk down the money and test it myself.Nov 14, 2006 at 8:32 am #1367092
Jason, did you check out the forum at Ritters site for more info?Nov 14, 2006 at 10:09 am #1367109
This may be more for the gear swap are, but I have enough reflective silnylon left over from my order to make you a 5.5 oz reflective/durable Vapor Barrier Bag. It’s only enough to make it big enough for a 6′ person. It would definatley be more weight concious, while still plenty durable. I can put it in a ziploc to emulate the vacuum packed thing it comes in :) $50 (sorry, the stuffs expensive material) email me at little_daddy979 at yahoo dot com if you are interested.Nov 14, 2006 at 1:34 pm #1367143
BINGO! Thank you, John. I hadn’t seen that they had a forum on that site.
Well, I did a search and there’s a fair amount of discussion regarding it. But it seems no one ever purchased it – they wanted to but always opted for something else. Ritter gives it good marks but says little.
Alas, still no reviews on it…Nov 14, 2006 at 1:44 pm #1367147
Thanks for the offer, David. While tempting, I actually own a Western Mountaineering HotSac, which is essentially that. 5.5 oz reflective vapor barrier bag. I’ve used it many times as a bivy. Love it, works perfect. Durability is fine… if handled with care.
The LAND-Shark interested me for the same reasons, in addition to the camo color (not too crazy on fire engine red, I would like to blend in to the scenery), for the high-visibility orange in rescue situations, it’s a bit roomier (HotSac is narrow), and being able to use boots inside (I’m a heavy guy and the HotSac probably wouldn’t hold up too well with my boots).
Although, I still might be interested in your fabric. What color is it?
As far as the vacuum packing… not necessary – I’d actually want to use the thing! The ziploc IS a nice touch, though.Nov 14, 2006 at 11:39 pm #1367205
The fabric seems really durable, the same as 1.3 silnylon, just with the reflective side. I doubt that it is as reflective as a space blanket, but it seems warmer than a regular VB bag. I think I will do some tests with baked potatoes in a Ref. SilNy, SilNy, Space Blanket competition in the near future. Heres a pic of me standing in my bag. I am 6’2, and the bag fits like a glove length wise, while roomy everywhere else. The outside is a bit duller than in the pic, while the inside is more reflective.
Nov 15, 2006 at 11:46 am #1367242
That’s a good looking vb bag… not so sure about the guy, though ;-)
Hats off to you if you made it yourself, too.
I just can’t seem to find a reflective silnylon in any color other than gray/silver. Metallic grey (on the outside) seems just as ‘loud’ as fire engine red. I’m really liking the camo of the land-shark, but I’d even settle for black or charcoal… if I could ever find it, or create it for anything less than 7000 yards.
I would be very interested in your test results for that experiment. Your experience with feeling warmer in the reflective vb is not simply anecdotal. Radiant heat barriers are continually scoffed at as worthless, along with vapor barriers as being unmanageable. Both are total myths – as a simple example, look at the insulation methods employed in building construction.
You can feel an immediate difference in warming effect by simply wrapping your forearm in a waterproof/breathable fabric, then do the same with a non-reflective silnylon and after some time you can feel the slight increase in warmth from no more evaporative heat loss. Then do the same with a space blanket, and the effect is much more profound – an immediate warmer sensation from the radiant heat barrier and then eventually the same warmth from the vapor barrier.Nov 15, 2006 at 12:32 pm #1367251
without going into too much detail on heat transfer theory (a year or two ago, i made some Forum Posts with some related mathematical heat transfer equations, IIRC), it’s not so much that reflective barriers are worthless at body temperature, but that at such low temperatures, the radiant component of the heat transfer equation is very small compared to the convection and conduction components.
to minimize heat loss at body temp (and lower temps), eliminating as much as possible convective heat losses and minimizing conductive heat losses is more important. Also, evaporation is important as was noted by another post mentioning VBs.
now, at the temperature of a burning flame, radiant heat loss becomes much more significant.Nov 15, 2006 at 2:07 pm #1367259
That is true, I just wanted to get every possible bit of warmth out of the VB I use anyway in cold weather. I would guess and say that the reflectivity in the sac will add about 2-3* over a regular VB, which in turn would get a full 10* warmer over my sleeping bag, instead of the “5-10*” estimates of other bags.
I made a 5×9 tarp out of this stuff too. I think it would come in very handy in winter when a small fire is a few feet away pitched lean-to style, or in the summer when its hot and I normally wake up sweaty because of the sun (pitched wrong side out). I would bet my headlamp can find it in the dark easily too.
That is one ugly fellow in the pic though. poor guy…Nov 15, 2006 at 2:19 pm #1367261
looks like you’ve done some good thinking on this matter. good for you. i prefer more stealthy shelters to avoid being noticed, however, you have some very nice uses in mind for your reflective layer in your tarp – very clever.
as far as the pic goes, hopefully, winsome charms are able to overcome a repulsive visage. probably not.Nov 15, 2006 at 2:32 pm #1367262
now, at the temperature of a burning flame, radiant heat loss becomes much more significant.
Strictly speaking, it is the temperature difference that matters. There will be no net radiant transfer between objects at the same temperature. BUT … the rate of radient heat transfer is proportional to the difference of the two temps raised to the 4th power! … moderate temp differences can yield good radiant heat transfer rates.
Now, how does that play out here? In the case of a liner in a sleeping bag, the temp of the liner will be quite close to body temp and I don’t think you’ll gain much relative to a non-reflective liner. But when using a liner alone (as an emergency bivy) the bag wil be cold and the reflective surface is a winner (witness the Adventure Medical Thermolite Bivy keeping me warm (and damp) during 50*F nights.)Nov 15, 2006 at 2:37 pm #1367263
@ryanLocale: Northern Rockies
Further to Jim’s comments, it’s a general rule of thumb that radiant heat loss is negligible in the presence of more than one inch of insulation next to the body, relative to the amount of total heat loss. So, yeah, in “thin” applications, like an emergency bivy, it’s “more” important.Nov 16, 2006 at 1:16 am #1367325
certainly delta-T is a term the radiant heat transfer equation (generally the last term on the RHS when written from left right).
just trying to keep it simple gents as i’m not sure that my ancient Posts involving heat transfer and insulation equations were appreciated (nor necessary in retrospect) at the time, IIRC.
my point of the burning flame was simply to illustrate the concept relative to something that a backpacker could relate to.
The “fourth power”, from the Stefan-Boltzmann law no doubt – if we’re talking blackbody radiators, where it’s ABSOLUTE temp, not delta-T; when not considering ideal radiators it’s still a 4th power function for the delta-T, i.e., after raising both T’s to the 4th power) which was my point exactly w/o getting too much into the mathematical details as not everyone on these Forums has a technical background. The “fourth power” is the reason why radiant heat loss can be so great at high temps (like that of a burning flame – how often are a backpacker’s surroundings at the temp of the burning flame??!!.
Excellent example of the sleeping bag liner temp relative to the body temp to illustrate the practical application of radiant heat loss.Nov 16, 2006 at 7:41 am #1367345
“The “fourth power” is the reason why radiant heat loss can be so great at high temps (like that of a burning flame – how often are a backpacker’s surroundings at the temp of the burning flame??!!.”
Mostly when newbs aren’t careful when cooking in their tent vestibule… Or maybe I should say ‘shortly after’ rather than ‘when’… :D
Edit – I’ve stopped chiming in after someone else adequately takes on the radiant heat loss subject that so few backpackers understand. However, something occured to me that not many people talk about… the ONE application where reflective cloth really shines in backpacking is for reducing radiant heat gain (aka as a place for shade in the summer).Nov 16, 2006 at 10:06 am #1367348
>>”the ONE application where reflective cloth really shines in backpacking is for reducing radiant heat gain (aka as a place for shade in the summer”
Ray Jardine in BB & GoLite Chrome Dome umbrella address this. IIRC, Stephenson mentions this somewhere about tent fabric (maybe not his own fabric – can’t remember), but maybe it was another source, so please don’t quote me on the tent fabric application.Nov 16, 2006 at 11:40 am #1367352
Yeah, the chrome dome would make a nice nap spot…
The TiGoat guys will make tarps and their tipis out of a reflective SilNyl… actually, that reminds me, they do mention using it on the inside to capture more of the heat of a fire / stove… which would be a suitable application as well.Nov 16, 2006 at 12:43 pm #1367357
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…Nov 16, 2006 at 1:37 pm #1367364
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 :)Nov 16, 2006 at 2:21 pm #1367369
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.Nov 16, 2006 at 5:36 pm #1367394
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.”
http://www.snugpak.comNov 16, 2006 at 8:34 pm #1367414
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.
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