- Mar 6, 2018 at 8:29 am #3522630
Yo! Thread Revival!
I’m a bit (theoretically) inspired by Polycryo at the moment after reading Ryan Jordan’s Notch Li review and the thread that’s started there. Thought I’d come back here for a read.
I’m more interested in it as a potential optimum floor material…not just as a groundsheet, but floor in some tent designs (won’t be the best ideal for all…) and very light Bivy’s. Why?
- potentially lighter than either heavier cubens/DCF or silnylons
- potentially higher HH than cuben/silnylon
- potentially better durability than cuben. Perhaps getting up there with silnylon at the right thicknesses
- likely very similar “wet weight” to cuben, much lighter wet weight than silnylon
Qualities of course depending on the thickness chosen.
Mar 6, 2018 at 8:35 am #3522631
- what is the optimum weight for a floor for both durability/aged HH (to make the effort of construction worth it), puncture resistance (ie if you are using an air mat of some kind), while still keeping weight down (ideally, we win here if weight is less than 1.0oz/sq yd)
- can we easily bond cuben/dcf fabrics to polycryo? Eg, 0.34 or .51 cuben for bathtub edges?
- could we then sew to those strips of cuben edge, eg sew DWR or WPB or mesh fabric to such?
- or, how well can we sew directly to polycryo? Would cuben tape work well in this situation as an edging to sew through? Note this thread: https://backpackinglight.com/forums/topic/97415/
- Does the Polycryo need lateral reinforcment in a Bivy situation to prevent stretch and failure? Could a few (eg 2-6) strips of cuben tape be place laterally along the floor to do this (mostly in the torso area)?
Another thought I had was bonding Polycryo to other materials entirely. Like, why not bond it directly to the base of a CCF pad? A lighter spec Polycryo might then be used, with the consequences of punctures to the Polycryo being very minimal. Bivy rolls up with the pad. Again, could bond Cuben to the edges. Could have “holey” pad, eg at the foot end, with foam cut out holes to save weight while keeping feet/legs off direct contact with the polycryo thus potentially reducing abrasion/punctures.Mar 6, 2018 at 8:37 am #3522632
Another thought. How hard would it be to bond large areas of cuben to polycryo? Could you get a thinner polycryo (like the GG smaller version) and bond it to say 0.34oz cuben for extra tear strength?Mar 6, 2018 at 12:04 pm #3522639
James MarcoBPL Member
@jamesdmarcoLocale: Finger Lakes
Basically, cuben/DCF is two sheets of plastic with some spectra in between to reinforce it then pressed together.
I don’t think you are buying anything for floors…plastics are still not very puncture resistant to pine needles, small sharp objects.Mar 6, 2018 at 4:12 pm #3522683
Daryl and DarylBPL Member
@lyrad1Locale: Pacific Northwest, USA, Earth
I’ve had good luck with using lightweight uncoated nylon for the floors then laying thing plastic over the floor to keep water out.
The uncoated nylon protects the plastic and keeps out bugs. It dries quickly and allows me to run the entire inner tent through the washer and dryer. The plastic can be easily replaced as needed.Mar 6, 2018 at 7:38 pm #3522725
Nick GatelBPL Member
@ngatelLocale: Southern California
plastics are still not very puncture resistant to pine needles, small sharp objects.
For several years now I have been using a very thin (1/8″) foam pad on top of a sheet of polycro, mostly to protect my NeoAir from sharp things. With this combo the polycro has resisted punctures and has held up well.Mar 7, 2018 at 12:48 am #3522804
David GardnerBPL Member
@gearmakerLocale: Northern California
Having used polycryo for both ground sheets and tarps I can tell you that you definitely do NOT want to bond it to anything. It works OK as a ground sheet in the thicker versions. It’s cheap and light, and easily replaced. But when punctured it tends to fail catastrophically – it can tear completely across all at once. If you bond it to anything else, when it fails (and it will) you’re going to have a mess trying to remove it and replace it with something more durable.Mar 7, 2018 at 12:52 am #3522805
I did a wet test last night with my gossamer gear 1/8 pad, full length. I deliberately folded it in half carefully and then held it under the shower for a couple of minutes trying to evenly wet one side of it only, aka, worst case scenario of wetness as a ground sheet. Note that no pressure was applied; a ground sheet recieves pressure from the person pushing it against wet ground…not sure if that will result it higher water adherence. I shook it ten times at the end.
Weight before; 83grams.
Weight after 185grams.
Water absorption penalty, single side = 122%
This seems to be a much higher water % absorption than elsewhere for Polycryo and Cuben, which seem to be in numbers in the 60-70% range, double side. The Evazote ~30kg/m^3 foam is undoutedly waterproof, but it lets plenty of water stick to it.
Thus, implies that having the pad directly on the ground may not be a great idea in this regard.
Sailrite.com seem to sell various 3M and other branded spray glues that look quite easy to use, for sticking foams and plastics together, including plastic to foam. I might try and get some, and some locally sourced (I’m in Australia) Evazote to do some tests with. Unfortunately much of the info in this thread regarding sources of Polycryo doesn’t help me too much as brands are much different, so I’ll have to work it out myself.
I’m thinking though that lighter thickness Polycryo could be the go if adhered to the CCF Evazote. Even the 1/8 evazote, about the thinnest you can regularly buy, is quite laterally strong. Together they’ll be stronger. Tears shouldn’t really be an issue unless you are reckless. And small holes or punctures will be of no consequence as the foam is waterproof.
Interestingly, I’m a bit weird with sleeping pads. I seem to find a torso pad like the GG Nightlight, or an 8mm evazote CCF pad, to be really comfortable even on my tile floor at home. Whereas other inflated pads I just don’t sleep as well on. I think partially its the way they move around, and also, let you push through under pressure to the hard floor.Mar 7, 2018 at 1:40 am #3522819
Here is a link to a 3M pdf on their spray adhesives. Reading this, I’m thinking that 3M type 74 spray is the one to use? Do people think this would work with Polycryo and EVA foam?
Cheers!Mar 7, 2018 at 4:42 am #3522851
Franco DarioliBPL Member
Bonding PolyCryo could be a problem if you live the item out in the sun or in a hot car.Mar 7, 2018 at 11:25 am #3522875
Yeah the temp limits of these adhesives are interesting. Some are rated better than others.
With EVA thin mat bonded to it, it would be most straightforward to then roll the end product up. For me that will usually entail then an outside pack attachment. I was thinking of doing a short section of a more durable fabric for the last bit of the outer roll. This would be more UV resistant also.
As its rolled, all the inner parts of the roll would be insulated by the outermost layer. So high temperatures would mainly be an issue for the outermost part.Mar 8, 2018 at 5:44 am #3523067
Rene RavenelBPL Member
How much will the glue weigh? How does that compare to water adhesion weight? How much would a coat of silicon spray do to address the latter (and at what weight penalty)?
I suppose bonding the polycro to foam will address how readily polycro tears once started, but if you put the foam on the outside, you don’t really have to worry about tearing the polycro, so your need for glue goes away.
You could also cut a hole in the polycro slightly smaller than the foam and bond at the edges. Double sided tape would probably work for this. When either part gets worn out or damaged, just peel the taped seam. But this raises the stakes for a bond failure.Mar 8, 2018 at 6:15 am #3523072
Good thoughts Rene, a couple similar to what I had. I was thinking prior to doing my wet-weight test of EVA of bonding edges of polycryo to the edge of the mat. But the mat retains more water than even silnylon does (from what I’ve read of other tests).
My chemistry training was very long ago (and not that high a level), but my thoughts with Silcon and water are that the water is forming a weak covalent bond to the silicon. Not sure what the strength of that is relative to polycryo or mylar, but clearly its higher. Potentially though, it does seem like that bond is less than the bond to EVA. Or, the EVA bond could be weak, but, the actual surface are of the EVA I’m guessing is much higher, with the face of it containing lots of cut away air pockets or crevices.
Would be interesting if Mylar or Polycryo or similar plastic could be physically bonded to the EVA without a glue, EG, by spraying it on hot? It would then fill all the small crevices on the face of the EVA. Perhaps it could then be much thinner? The Polycryo would actually need to form some kind of bond with the EVA though. Not sure if that works.
Not to hard to measure the weight of the glue in a test. I need to try get materials for a test.
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