Dec 9, 2012 at 4:05 pm #1296907
Has any one tried applying a hydrophilic coating to the inside of a cuben fiber shelter? The hope is that this would encourage water to stick to the material and slide down it rather than bead up and drop off.
If this works, it could eliminate the need to tape seams, which would save a good bit of weight (24% in the case of Zpacks' Hexamid Solo Tarp).
Thanks!Dec 9, 2012 at 4:27 pm #1934353
Franco DarioliBPL Member
Bibler tents have something like that, however you still need to seam seal themDec 9, 2012 at 7:47 pm #1934390
Dustin ShortBPL Member
The weight of the coating for such large surface areas is not negligble. Based on the ZPacks specs your coating would have to be at least under .2oz/sqyd (likely under .15oz/sqyd) to be lighter than seam taping/sealing. That's pretty hard to achieve at home and will likely eventually peel over time compared to seam treatment.
Worth a shot if you want to experiment but likely not worth the effort if you are just playing a hunch to save weight.Dec 10, 2012 at 10:28 am #1934515
Colin KrusorBPL Member
@ckrusorLocale: Northwest US
Hydrophilic coatings for plastics are commonly used for medical devices, filters, and other applications, but I don't know of any that are marketed as retail products the way hydrophobic coatings are. The most common hydrophilic coatings are polyvinylpyrolidone (PVP), polyacrylic acid, and polyurethanes. Most are two-layer coatings that require a bonding layer and a topcoat. They aren't available in aerosol cans; you'd have to aquire them (maybe as samples?) from an industrial supplier and apply them with an airbrush. As Dustin said, these coatings are not weightless. It would probably be substantially heavier than seam taping.
Corona treatment, on the other hand, is essentially weightless, and it radically increases the surface energy of low-energy plastics like PET (the surface of cuben). I've considered making a small corona surface treater for cuben surfaces to improve peel strength of bonded seams. If you have some electronics expertise (you don't need much) and some of spare time, you can build one.
This youtube video shows application of a DIY corona treater to a mylar surface. It's very hydrophilic after treatment:Dec 11, 2012 at 7:53 pm #1934902
Sam FarringtonBPL Member
@scfhomeLocale: Chocorua NH, USA
Some while ago, Jack Stephenson said:
"The extremely low radiant heat loss of the Mylar surface results in a single wall tent with almost as little condensation as our unsurpassed double wall tents."
(From a Warmlite catalog, ca. 1970's)
Sent a page of this 'article' to Roger Caffin, and he commented something like, "Yes, that's Lord Jim all right," but otherwise remained mum (as he is entitled to, of course).
If Jack's statement is accurate, this might explain the comments here about lesser condensation with Cuben tarps. Anyone know, or have an angle on this?
And if true, how would the hydrophilic coating affect the condensation level?
And if all that worked out, sure the coating would have significant weight; but how would it compare to a sub one oz. netting or DWR nylon or polyester inner tent?
Just wonderin' . . .Dec 14, 2012 at 7:11 pm #1935531
Wow – was not familiar w/ corona treatment. I think a hydrophilic effect with NO coating is the clear winner.
Just as a reminder, my interest isn't in eliminating seam sealing, but misting.
Now, which will prove more compelling: building a corona widget or that amp kit I've had my eye on??Dec 14, 2012 at 8:01 pm #1935535
Sam FarringtonBPL Member
@scfhomeLocale: Chocorua NH, USA
You say: "The hope is that this would encourage water to stick to the material and slide down it rather than bead up and drop off."
True enough, but it's still going to be very WET, and if you touch it, some of that additional water is going to douse you or your equipment.
Others were talking about the unwoven material used by Bibler, and earlier by Early Winters to line its GTX tents. The idea is to soak up the condensation, and hold it until it has time to evaporate. It also doesn't feel as wet when you graze against it, because the water has been absorbed and is not just sitting there on the surface.
With the microthin coating, there is nothing to aborb the water, so it will just sit there, or perhaps hang there would be more like it.
If Jack and some others are right about the condensation not forming so much on the PET, or Mylar surface in the first place, that sounds better. Even better if there is netting (that also keeps out bugs) on both sides of you and high enough at head and foot to protect you and the bag/quilt/hat from water contact. Or it could be sub one ounce fabric instead of netting if you like that better. TarpTent seems to like the netting on some of theirs, but no Cuben with them, of course.
In your later post, you shift from water dropping to "misting." This word gets thrown around so much, I'm not sure people know what meaning is intended. Some are talking about fine condensation that looks like somebody "misted" the tent wall with a sprayer. This can be common in a cold, heavy rain in a silnylon tent, even if no one is in it. Others are referring to very tiny water droplets penetrating through the tent wall and falling slowly, like a mist. The latter is addressed by a material with good water resistance. The former is inevitable in a single wall tent, the only thought being that if Jack, et al, are right, it will be less with a Mylar surfaced material.
So it sounds like you hope that the Hydrophilic coat will keep that lesser amount of condensation on Mylar from dripping. But it might also remove the tendency of the Mylar to reduce condensation. Please let us know how it all works out.
In the meantime, I suggest the best avenue is to find very light WPB coatings or treatments that water vapor will permeate through at lower humidity pressure, as you would have in a tent, as compared with a jacket during exertion. Some mentioned in Alan Dixon's article on this site are Event, Nexus Epic, Propore and maybe the updated verions of Entrant being used by Montbell. There are serious water resistance issues with Epic, the lighter Propore materials available are very fragile, the Montbell material is probably not quite breathable enough – so that leaves a very light version of Event. That's where I would suggest looking.Dec 14, 2012 at 9:18 pm #1935544
Everybody has seen water droplets slowly crawl down a window. When the surface in question is *completely* covered in water, there are no longer little sacks of surface tension holding volumes of liquid. Water molecules are free to flow in a planar micro-river between the solid surface and the river's surface tension film. This holds the promise of retaining a lower volume of liquid than a surface covered in bulbous droplets. A continuous film of surface tension also means any degree to which hydrophilic properties increase the rate of condensation ends as soon as the surface is completely wet.
Re. 'misting', agreed – that term has been mis-used to the point that it causes more confusion than clarity. I'm talking cuben, so I meant droplets of condensation being shaken loose and falling inside the tent, rather than a penetration process. When I first experienced this I referred to it as "induced rain." "Blow through" might be a better name for the other effect. Both, of course, resulting in a 'mist' inside the shelter.
I'm set on Cuben for its weight, which also rules out the WPB Cuben (1.43 oz/yd2) (with the possible exception of a portion of the roof near the apex) so a woven/laminate option like Event is out.
If I do conduct any field testing, I'll be sure to post results.
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