Mylar and Mylar Bivy Advice Needed

Discussion in 'Gear' started by trampalong, Dec 6, 2016.

  1. trampalong

    trampalong Hobo on Wheels

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    I am going to risk overcrowding the forum with a second thread because I'm trying to gather information in rather a hurry. I apologize for monopolizing the forum.

    I purchased a SOL Breathable "Escape" Bivy last year prior to my bike trip and found it very adequate. It is a Tyvek bivy with a mylar (or at least mylar-like) inner coating to reflect heat. The problem is that the mylar quickly wore away, and the bivy is no longer able to keep me warm.

    I don't know if it wore away because the woven surface of the Tyvek simply didn't allow the mylar to cling, if it was cheap manufacturing, or if all mylar is like this. I've also had mylar blankets that had the mylar wear off, but I just chalked that up to them being $2 blankets.

    Is there such a thing as long-lasting mylar? I worry that whatever I buy will erode away as quickly as the SOL, but I need something reflective to increase the heat-retention of my system.

    I am going to keep the SOL bivy for the Tyvek, so I think a blanket would work fine (I'll just tuck it between my bag and bivy), but I would prefer a bivy for ease of stowing away. Anyone with a product recommendation or with knowledge about mylar construction and quality would help me greatly.
     
  2. Nick

    Nick Post 'em if you got 'em!

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    This may be a dumb question, but are you using this thing as a tent or as a sleeping bag? That SOL bivy is meant to be an emergency use thing so it's not surprising that it didn't last very long. I'm no bivy guy, but I've never heard of mylar beind used in anything meant to last. The lack of breathability also makes it a poor choice.

    Edit: Mylar is used inside some pads where it doesn't get direct contact, but that degrades too as was seen in the semi-transparent NeoAir Xlite pads.
     
  3. trampalong

    trampalong Hobo on Wheels

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    I am using inside of a tent. I also use a vapor barrier so breathability is not important. I think that there is certainly a shortage of good Mylar products, but I find that Mylar really rounds out a sleep system that also uses a vapor barrier. It adds to the warmth. I'm thinking there has to be SOMETHING out there for me.

    You are right, though, about the pads. Mine is already going that way, but I wonder if that is not because of my breath being held inside of the pad and causing bacteria build up. Mylar doesn't seem to like staying wet. I used to use Mylar to cover my bike in the rain, but the rain destroyed the Mylar coating quickly.

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  4. Brendan S

    Brendan S Member

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    There are different thicknesses of mylar (PET) (for example cuben fabrics use different thicknesses of PET, also the backing for some XPAC fabrics use a pretty thick layer as part of their laminate)...for a long term solution for your application you might look into if the aluminized cuben is still available. Do a search over at backpackinglight. I know some guys were experimenting with it a couple years ago.
     
  5. trampalong

    trampalong Hobo on Wheels

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    Thank you for the information. I did some reading around and at least I found a term for what happened to me. My problem is with Mylar "delaminating," not with the material it is laminated to tearing. I've heard of two possible reasons for why this happens, one being the use of a water soluble adhesive to bond the reflective layer and one being a lack of protective coating leaving the aluminum exposed to air and oxidization.

    I was reading over at backpacking light and apparently the later version of that aluminized cuben fiber performed fairly well, but the company that produced it was acquired by Dyneema some time after that discussion took place, and I am not sure if the material is still around. Regardless, I am not really in a position to make my own bag right now.

    I bought a SOL emergency blanket to get me through the next short while in the mountains that I have to do, but I don't have much expectation for it lasting. I'll try to keep it as dry as possible and not compress it any more than necessary and I'll see how it goes.

    In the meanwhile, I think that I need to find a high quality item. If anyone has used a Mylar bivvy or blanket extensively and seen it hold up, I would appreciate the info. I'm also aware of western mountaineering's Mylar vapor barrier, but that would especially worry me about m longevity. If someone could vouch for whether the Mylar holds up to sweat and moisture, I would consider it.

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  6. Jackson

    Jackson I like to go outside.

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    This may be a stupid question, but I can't tell based on what you've said so far. Are you using a sleeping bag in conjunction with this bivy and your tent? Or just the tent and the bivy? A good down sleeping bag can fix a lot of these problems and not add a ton of weight or take up lots of space.
     
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  7. trampalong

    trampalong Hobo on Wheels

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    Sorry, I should have clarified that I use a down sleeping bag between the bivy and vapor barrier. It is only a 20 degree bag, though, and a year-old heavily used one at that, so I use the other components to add warmth without adding too much weight.

    Making my system modular like this is the only way that I can sleep comfortably in the summer and winter. I've been on this trip since May.

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  8. Brendan S

    Brendan S Member

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    I don't think any of the metalized fabrics are going to hold up under repeated folding/packing. I think your best and cheapest/lightest/best bet is:
    a) just keep using the emergency bivys and replace when they delam
    b) spend a few bucks on some sportwash or downwash and hit up a laundromat to wash your bag to restore some loft. Makes a huge difference if its gettin grungy.
     
  9. trampalong

    trampalong Hobo on Wheels

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    I'm starting to feel the same way about the longevity of these things. I don't like relying on disposable things, so I'd rather find another way. The cleaning sounds like a good idea, for sure. I might try looking for a lightweight summer bag that's big enough to put my current one inside of. It'll be a kind of heavy fix, carrying two bags, but it's at least an option.

    I'm also going to work on ways to keep from folding my emergency blanket up so much. Maybe there's a way I can store it so that it will last. I might try rolling it around something. It's not like I need the reflection every night, so taking the trouble to store it carefully might work.

    I've made some clothing changes, too, all of which seem to have worked quite well. I won't know for sure how much I need the reflection until I get into the mountains again.



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  10. Ugly

    Ugly Member

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    my 1/2c is that maybe the alum coating itself is not providing much more warmth, but instead the layer is just trapping in more of the heat- so even if it is delaminating that may not make a big difference in retaining heat?

    I have used them as ground covers, especially in winter, and they wear out fast with limited use.
    For a sleeping system though, a sleeping bag liner adds a few degrees and would not weigh much- but costs $...

    If you do get a second bag- I sleep on the coldest winter trips with a 40d syn Inside of a 15d down. Down doesn't do as well when compressed inside a synthetic from my humble experiences.
    Good luck and way to go, that bike you have is pretty sweet.
     
  11. trampalong

    trampalong Hobo on Wheels

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    That's helpful to know. My bag isn't big enough to put around another so I'll look for another down bag if I end up going that route.

    My bivy was much warmer last winter with the aluminized portion, though. I'm certain of that. The tyvek still pulls some work, but it doesn't bounce heat back into the down like it used to.

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  12. Brendan S

    Brendan S Member

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    Agree that lightweight syn is great addition to a winter system but generally having the syn on the outside is preferable, which is why a quilt or serape is nice since it won't compress the down. Moisture from your body generally condenses towards the outside of your system so it's best if it's in the syn rather than down. I have a couple 2.5 oz climashield quilts that cost about $30-$40 in materials and a couple hours to make. ~12oz and killer versatility.
     
  13. trampalong

    trampalong Hobo on Wheels

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    A quilt sounds like a good idea, and if it won't compress the down then synthetic sounds nice. I'll look into that.

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  14. Ugly

    Ugly Member

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    Something that is light and not compressing the down is a good point that I did not consider. I will take a look at a quilt. it would be more versatile than carrying even the lightweight syn around.

    @trampalong Winter is tough, my frostbitten toes usually can use all the help they can get.
     
  15. trampalong

    trampalong Hobo on Wheels

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    Winter is certainly being tough on me, but I've always been a warm-climate kind of person. I'm in the Organ mountains now, and last night was cold enough to convince me that I need to go ahead and get some more insulation (tonight is crazy warm, too. I just can't get used to the desert). I stayed warm but if temps go much lower I'll start to have trouble staying asleep.

    I think I'm going to try the quilt path, as it seems a little more affordable than the second bag path, unless I'm willing to put up with a heavy bag.

    The SOL emergency blanket has survived a couple of nights fine, but it's just not that effective outside of my bivy and it's a lot of work to position every night if I want to put it inside, so I'm about to give up on it and stash it in my bike for emergencies.

    I've got to order the quilt soon because I need overshoes and need to get everything at once. Any advice on a model would be appreciated.

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  16. Brendan S

    Brendan S Member

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    100
    Enlightened equipment (prodigy is their synthetic one...they occasionally have seconds for sale on their site as well) and mountain laurel designs for the cottage companies and looks like Big Agnes is making one now too (kings canyon ul quilt). That might be the way to go if EE or MLD don't have any currently in stock. Make sure you get one big enough to go over your down bag.
     
  17. trampalong

    trampalong Hobo on Wheels

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    Thanks for all of the help everyone. I shopped around and ended up buying the Big Agnes blanket. I've also found another possible Mylar bivvy candidate, the 2go systems trifecta, and I might end up getting that as well and replacing my SOL, but I'm not worried much about it right now. I has the blanket sent ahead to Silver City and I'll pick it up in a two or three days.

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  18. Absarokanaut

    Absarokanaut Member

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    New Mexico? Gotta love the Gila.
     
  19. trampalong

    trampalong Hobo on Wheels

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    Well, I haven't seen Gila yet but I'm on my way there!

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