groundcloth

[Anthony Weston]

I have used tyvek as a ground cloth but it's not as waterproof as I'd like. I have also used Gossamergear's Polycryo ground cloth which is light, waterproof but wears out too fast. So I glued the two together and have used on the last few trips. The only drawback has been dust and crud that gets between the two layers but I just shake it out, who cares as long as my bag is clean and dry.

[Zack Karas]

Interesting idea.

Questions:
–which fabric are you putting on the ground side (I'm assuming tyvek)?
–what is the finished weight and dimensions?

[Anthony Weston]

tyvek on the bottom.

Tyvek Groundsheet for Contrail/Virga 5.5 oz
Polycryo 1.5 oz
glue .5 oz

[Zack Karas]

I was thinking you were using this as your only floor–seems a little redundant/overkill and heavy with the bathtub floor of the TT.

I've recently starting sleeping under an Oware pyramid w/ my dog and might consider doing this hybrid, but with the polycro on the ground side to avoid the dog's nails.

[Anthony Weston]

this is my only floor, I use a tarp not a tarptent these days. So far my dog stays at home.

[Zack Karas]

I misinterpreted what you wrote.

What kind of glue did you use?

[David Drake]

Could you glue (maybe sew?) the two layers on only three sides, so that clean out between the layers would be easier? (Maybe this is what you already did.)

[Jay Wilkerson]

Equinox makes a great Ripstop Nylon groundcloth (Globe Skimmer)…90 x 42 at 4.4oz and 4 cloth corner tie-outs. I have used it under my GG SpinnTwinn a lot the past two seasons and it seams very durable–Always preen the footprint!!

-2 cents worth

[Brian Lewis]

"I have also used Gossamergear's Polycryo ground cloth which is light, waterproof but wears out too fast."

My experience has been different. I used polycro on the PCT last year; somewear along the way I got a cut in it or some sort of one-time damage and switched-by-mail to the other one (polycro comes in sets of two). I repaired the damaged one later pretty easily and still use both; with well over 1000 miles on each of these, they're both somewhat beat up now but still plenty usable.

The cost to ship these is substantial relative to the low cost of the item itself, so for a 2-person tent my wife and I share I bought 2-mil painters dropcloth type plastic; it's definitely heavier and I'm confident that it's not as tough.

If you're buying something else from GG so the shipping isn't too big a hit, I'd definitely recommend trying out polycro.

[Nick Gatel]

Agree with Brian on the Polycro. I was sketic at first, but it is holding up well. Been using it all year.

[Thomas Burns]

Ditto on the polycro. It's cheap enough and light enough that you can take along a couple of hunks of it if wear on the first one is a problem.

For my Contrail (with a bathtub floor), I tend to layer it inside the tent when I need a water barrier. Otherwise, I never need to use it. That bathtub floor on the TT's is pretty danged tough, and worth the weight.

Stargazer

[Dondo .]

The cost to ship these is substantial relative to the low cost of the item itself, so for a 2-person tent my wife and I share I bought 2-mil painters dropcloth type plastic; it's definitely heavier and I'm confident that it's not as tough.

I've also found polycryo to be pretty tough. To save on shipping costs, the shrink film used to seal windows in winter can be found in hardware stores and other places. It seems to be identical to polycryo. Frost King is one brand.

edited to correct brand name

[Brian Lewis]

Cool! I'll have to check this out next time I'm at a hardware store (same place I'd look for painter's drop cloth plastic anyway …).

In the meantime, if anyone has actual experience using this stuff as a groundcloth, it would be helpful to know, ditto measured weight per unit of area (sq ft or whatever). All things being equal, I'd rather throw my $$ to Gossamer Gear, but with the shipping cost …
Plus the window shrink film option offers more size options.

Since it's designed to shrink when heat is applied, what about using it in hot weather and/or direct sunlight?? I have this sort of cartoon video in my head of waking up to a one foot squared piece of more rigid plastic centered under my tent …

[Diplomatic Mike]

Hi Brian,
I use window insulation film too. Much cheaper, and just as durable in my opinion as GG Polycro, and i've used both.
The stuff i use in the UK comes in a 1.5 x 4 metre sheet.
Stuff i use

[D G]

Hi Brian,

This is from the GG website:

"WARNING: Since these sheets are made from shrink film they will shrink when exposed to extreme heat. We tested these sheets in heat this summer and found that the sheets shrink 1" to 2" (3 to 5 cm.) in width and up to 5" (13 cm.) in length. These sheets do not need to be in direct sunlight to shrink, just very hot temperatures."

So it would appear the GG polycro sheets would behave similarily. I would assume this would not really be an issue however during the night(when you'd be using them anyways) with cooler temps/no sunlight.

I have to say I've never noticed any shrinkage with my polycro sheets and have been pretty happy with them. I'm tempted however to buy the window film for making some ultralight groundcloths.

[Dondo .]

Some more detail: The stuff I've been using is sold as "Frost King Patio Door Insulation Kit". The size is 84"x110", which makes three groundcloths 3'x7'. Each groundcloth weighs 41g on my scale. Like Mike, I've found them to be as durable as polycryo. You can find it at Home Depot with the window and door insulation. It comes in a red box and sells for about seven dollars.

[Frank Deland]

I just use a strip of coated nylon only slightly longer and slightly wider than my sleeping bag. I have not found it necessary to cover the entire floor area.

[Brian Lewis]

At my local Ace Hardware store today I bought a window insulation kit package (plastic plus double-sided tape). Advertised as a 6-window kit it's 108 sq ft, 62" x 252", and just cost about $13 after taxes — not bad. This is actually branded as an Ace hardware product.

My GG Polycro is 40" x 96"; GG lists this as weighing 43g, and I weighed mine at 47g. That's about 82 square inches per gram, or 0.012 grams per square inch.

The Ace Hardware plastic is about 70% of that unit weight at 0.008 grams per square inch, and indeed it feels a bit thinner to me too, though my old GG polycro has been through a lot and is doubtless a bit less flexibile/pliable.

Given the even lighter weight, I'll be happy to try this alternative, but I'm not confident that it will wear as well. If anyone has weight-per-square-inch info on other brands, that might be interesting, i.e., maybe there's are particular brands that are about equally heavy duty as GG polycro. My 62" x 252" piece from Ace weighs in total 132g (4.7 oz) fresh out of the box.

[Dondo .]

Brian, the ground sheet I cut from the Frost King patio door kit measures 36"x84" and weighs 41g on my scale. That comes to about .0136 grams per square inch, or slightly more heavy duty than polycryo.

[Jack Scheckton]

Been using a cheap mylar "space" blanket as a groundcloth for some time… Have spent maybe 15 nights on it with no tears only a few pinholes.

weighs 2.5 oz

I have no evidence, but it seems warmer than clear poly

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