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Matthew Morrissey
Polarmond on 04/05/2013 05:42:24 MDT Print View

Hi everyone,

I came across an interesting project to make an all-in-one insulated tent, sleeping bag and mattress. I'd be interested to hear any general comments or thoughts about the functionality / feasibility / desirability of this system...

Here's the link -


Ken T.
(kthompson) - MLife

Locale: All up in there
Re: Polarmond on 04/05/2013 06:30:38 MDT Print View

Wonder what the locking piece is?

Dustin Short
(upalachango) - MLife
Re: Polarmond on 04/05/2013 11:52:30 MDT Print View

The sketches are pretty piss poor. They're based on "it'd be cool if it worked like this" and not on actual physics or ergonomics. I'm all for innovation in solving problems, but I don't see any problem solved by this product other than "I wish my bag/shelter/pad was just a single item" which I've never heard anyone say.

The concept appears to be that your lower body (all but head) is sealed in a chamber that generates heat. This then pushes moisture through a WP/B layer into the head chamber which is the same as ambient. There the moisture can condense without fear of wetting out your insulation. Sounds great if you ignore all the thermodynamics involved in shelters.

The first issue, how to seal heat in only the lower chamber. This is actually surprisingly hard, heat likes to spread itself around. First we have standard insulation like down or synthetics. Slows down heat so it builds up in the lower chamber. The solution is no different from using a sleeping bag (and pad to insulate from the ground). So this is just a more complicated way to do it with less options to swap out gear as conditions change. That's a simplistic breakdown. Going more in depth...

The specific "innovation" is moving the moisture outside the hot chamber. Heat does this naturally, and a WPB layer would seem to suffice to keep the the moisture that condenses off your insulation. Basically the same concept as any eVent/Goretex bivy...but again married to a specific structure so less modular and versatile. From an ergonomic perspective it also looks incredibly difficult to get into the hot chamber without a bunch of fuss (that's a "pain" point of the consumer that is VERY hard to overcome no matter what the "value" of the product. Convenience trumps all other value usually).

But I want to go into their parameters and assumptions on the physics to show why this is a complete waste of time and little more than a con game for investors (most of entrepreneurship is a con game though unfortunately).

Firs the WPB barrier. They assume they can maintain a 40C temperature gradient across a WPB barrier. That's impractical. Using aerogel fabrics it may be possible, but aerogels fabrics are heavy (negating the primary attraction to aerogel in the first place) and they don't compress or pack very well. Also nearly all WPB barriers require a very high relative humidity to pass moisture vapor. So your insulation with be a microclimate on par with a steamy swamp. If the cold chamber truly is the same as ambient (and far below freezing) then the freeze point along the temperature gradient is likely to be below if not on the inner surface of the WPB barrier. In other words you'll get condensation inside your bag, either liquid or frozen. Not much different than current setups thus necessitating synthetics or vapor barrier clothing anyway (ie no benefit over current systems).

In practice though the cold chamber will not be ambient without major ventilation. Major ventilation is not storm worthy. Lets assume the shelter is storm worthy (if it isn't then there's nothing to talk about). Because it's storm worthy it has to keep out moisture and wind, which requires a lack of breathability in the outer fabric (even if there's some, it's not enough). So the "cold" chamber will actually trap moisture and heat from exhaled breath, and any that escapes from the hot chamber. This may actually help the condensation issue I mentioned in the previous paragraph by moving the freeze point somewhere into the outer cold chamber. It still means you'll have condensation issues inside your shelter like current solutions (and demonstrates that the companies basic assumptions on the physics are what else do they not understand?).

We have other niggling issues like how this shelter has a larger volume to warm up in the hot chamber than in a regular mummy bag, thus it's less thermally efficient than current solutions (their marketing pitch aside).

I would say this is virtually the same as keeping your sleeping pad and bag inside a waterproof bivy and just rolling up the whole package as one, except you can swap out bags or pads or shelters for various trips (you'd need one for arctic dry, arctic wet, dry winter, wet winter, etc). It's really the same as having a waterproof sleeping bag with a minitent over just your head...and somehow a sleep pad integrated.

I just don't see any way this is more convenient, lighter, less voluminous, cheaper, or more versatile than current systems. I'm sure there is plenty of innovation space in techniques, designs and materials that shelter and insulation can benefit from, this company's idea just doesn't bring anything to the table. It's a variation on a theme and what we need is a totally new theme. They're offering a "newer, better, smarter" silver bullet for hunting werewolves when we've already driven lycans to the brink of extinction with the old bullets.

Daryl and Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: Polarmond on 04/05/2013 12:05:45 MDT Print View

I experimented with something like this a few years ago. My design wasn't as sophisticated, however.

I simply made a big bag out of closed cell foam pads. I entered from the side so the thing looked a bit like a standard size envelope.

The foam bag replaced sleeping bag, sleeping pad and tent and, at the time, was lower in weight than the three items I was carrying. It was damp inside but pretty warm. I gave up on it, however. Too bulky, not as warm as what I was already using, etc.

There was also a guy in Seattle in the 70s (Bob Hartley or something like that) who made a clamshell shaped thing out of open cell foam. Never caught on. I'm guessing it turned into a big sponge in heavy rain.

Dustin Short
(upalachango) - MLife
Matt on 04/05/2013 12:06:17 MDT Print View

I hope I didn't rain on your parade Matt. I'm assuming this a company you're working on.

Make a prototype. Test it in a mountain. We'll be happy to help critique and troubleshoot issues on this site. Also I highly recommend you peruse the articles and forums because you'll learn a lot about what the current state of the art technologies, and more importantly techniques, are that your product faces as competition.

I also want to say my analysis is based on current research into state of the art material science used for both insulation and weather protection. The link you posted appears to be a design innovation for outdoor recreation and not an actual innovation in materials. If you do have some revolutionary materials that can be made at scale (like the new polymer aerogels) than that can be a true innovation. But the implications of new materials are far more lucrative in other markets than outdoor recreation (although we do love and appreciate new technology!).

I'm also harsh on new startups. A good investor will either ask the same technical questions as I did, or will ask the far harder and demoralizing questions of "so what? Why should I care? How will it make money for me?"

Edited by upalachango on 04/05/2013 12:08:22 MDT.

Matthew Morrissey
RE: Polarmond on 04/07/2013 11:55:18 MDT Print View

Thanks for the comments guys!

Edited by hornblower on 04/09/2013 08:33:34 MDT.