Tent footprint – help me choose one

OK, I got my polycro groundsheet from Gossamer Gear today and cut it to length. It is barely wide enough for my Hubba Hubba. I taped light rubber bands on the corners using packing tape cut in half. The tape holds well on the sticky fabric and the rubber bands hold the grounsheet in place nicely.

Here are some pics:

The whole thing weighs 1.38 oz including the rubber bands. That's nearly 7 oz weight savings over my factory Hubba Hubba groundsheet (8.18 oz)!

I can't wait to test it out in a couple weeks.

David:

The shortfall in width was the main reason why I didn't get the Polycro for my BA Seedhouse 2 SL. I also figured that if I were to cut down the size of my 2-mil plastic sheeting to match the Polycro, the weight difference would be no more than 1 lousy ounce. And yet, with the plastic sheeting, I have much better coverage.

Curious, can you compare/verify the weight of a similarly-sized 2-mil plastic sheeting vs. the Polycro?

David – you get the Lightitude Award for the lightest fully anchored groundsheet ever. Congratulations!

Out of curiosity though, what is it's primary function?

1. Abrasion resistance?
2. Tent cleanliness?
3. Appeasing wife?

I think it would work pretty good for 2 and hopefully really well for 3, but I question it for number 1.

.

Ben,

The polycro sheet is 40" x 96". I cut off 18.5" off the end, so mine is 40" x 77.5" = 3100 sq in. Now, the 2-mil sheeting from Wal-Mart is 13824 sq in and weighs 16 oz. If you cut it down to 40" x 77.5", then it would be 22% of the area of the original sheet, thus 3.59 oz.

So, it's 1.38 oz for the polycro or 3.59 oz for the 2-mil. A difference of 2.21 oz.

I think the width is actually fine for my tent. Two pads are 40" in width, so it just barely covers the area where we will be lying/sitting. It's a little bit smaller than the original Hubba Hubba groundsheet (in the pic), but not by much.

I'm happy with the groundsheet, but time will tell how durable it is.

David,

Since you cut off some of the Polycro sheet, could you do us a favor and do some "destructive testing" on that and the 2-mil plastic?

Could you take a sharp sizzors or similar object to mimic a twig and puncture both the materials, comparing the pressure needed to punch through.

Also, could you do the same experiment with a sewing needle to mimic a thorn?

This is what I did to come to my conclusions stated in an earlier post in this thread. I compared 2-mil plastic, 1.1 oz silnylon, and Tyvek Homewrap. I did not have any Polycro to compare to, so if you could compare the Polycro to any of these three, we could rank all four materials for their puncture resistance.

What a group here! Inquiring minds want to know!

Michael,

I thought the very same thing about the scrap piece! I wish I could come up with some kind of controlled test in which I measure the force required to puncture the material with various objects (twigs, rocks, etc.). Perhaps I can strew rocks over my bedroom floor and sleep on it for the next week. Ah…all in the name of science! Stay tuned…

David,

When I tested the plastic, silnylon and, Tyvek, it was clearly evident which was more puncture resitant! They are not similar at all in that characteristic so it was very easy to feal the difference in pressure needed. No scientific calibration required!

If you do the test and the pressure required to puncture the Polycro is hard to distinquish from another material, that's fine. Report that and we will lump the two materials into the same "puncture resistant" category.

As to abrasion, that is tougher to measure. Perhaps, drag pieces of fabric on a piece of sandpaper with a fixed weight (brick) on top of it and visually compare the results?

I am concerned more about puncture because that represents immediate failure in the field whereas abrasion resistance deals more with long term durability and the material can be replaced periodically.

David,

I use just about any type of plastic, 2 to 4 mil, and cut it to shoulder-to-hip length for a side entry tent and about a foot or so longer for a front entry tent to provide protection for those areas where body weight is applied. Saves not only a tad bit of weight, but space as well. It is also much easier to pack up for an early start.