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bikeandboots
0
Jul 10, 2018
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Do you feel there is any need for a groundsheet? Either for overall tent durability or to prevent water from seeping up.
Jul 10, 2018
dandurston
5116
Dan Durston
Jul 10, 2018
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bikeandbootsThe sil/PU polyester used in this tent is extremely waterproof. It has been independently tested by Richard Nisley (of Backpackinglight.com fame) and the results are provided on BPL: https://backpackinglight.com/forums/topic/massdrop-announces-a-dan-durston-tent-2-people-2-hiking-poles-29-oz-199/
So no, the tent will be plenty waterproof for a very long time without a groundsheet.
The 20D fabric is of course a lightweight fabric, and thus wouldn't hold up that well if you're pitching on bedrock, sharp gravel or the prickly cones of a Jeffrey Pine. So in the backcountry you'd be fine without a groundsheet as long as you take resonable precautions (scan the tent site for sharp rocks and sticks). On gravel frontcountry sites I'd use a ground sheet.
Jul 10, 2018
a_aa
6
Jul 11, 2018
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dandurstonIn my simple minded head, the benefit of switching from nylon-based fabric to polyester based fabric is no sagging when wet, at the expense of a little less overall strength (at appr equal weight and HH). I agree that this can be a very nice trade off for the rainfly, especially if HH is equal or higher. But sagging is not a problem with the floor, is it? Have you considered if a nylon based fabric in the floor could lead to a more robust floor, without increasing weight or reducing HH?
Jul 11, 2018
dandurston
5116
Dan Durston
Jul 11, 2018
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a_aaThe advantage nylon has over poly is tear strength but the most important thing for floor durability is abrasion resistance. These are very different. A fabric can be very hard to tear but still not very abrasion resistant, such as cuben/DCF. That's why 0.5oz DCF makes a decent fly but an unacceptable floor (in my view). Abrasion tests are hard to come by, but what exists shows that nylon and polyester are much closer in this area - maybe an edge to poly. In practical applications, I've never heard of someone displeased with a 20D poly floor, although lighter fabrics obviously trade some durability for the weight savings. Overall, I don't think nylon has a meaningful advantage in floor durability when compared with similar weights of polyester.
The downside of using nylon as a floor is that nearly all nylons are silnylons, and these are typically quite slippery (search for "slippery silnylon floor"). So if you're pitched on even a slight slope, it's common for sleeping pads to slide around on the tent floor, which can be annoying. Since polyesters are available with a sil/PU coating and the PU is on the inside, you can have a inner floor that isn't annoyingly slippery. The other advantage is that it can be seam taped, which isn't that important for a 1P floor since there shouldn't be seams across the floor (there aren't in the X-Mid - just at the corners) but the ability to seam tape PU is a notable advantage for the fly.
So overall, I think any durability advantage from using nylon in a floor application isn't meaningful in a lightweight backpacking application, and it would come with the downsides of making the floor slippery and losing the seam taping. There's also the practical reason that if you want good pricing on these fabrics you need to buy in bulk. One of the reasons this tent can be so affordable is because it uses the same material for the entire thing.
Jul 11, 2018
dandurston
5116
Dan Durston
Jul 11, 2018
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a_aaHere's a table from RipstopByTheRoll.com which compares various fabrics for tear strength, abrasion etc.
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The material used in the X-Mid is a 20D (1.1oz) polyester with a 2000mm sil/PU coating (see the independent waterproofing test results I posted on BPL). https://backpackinglight.com/forums/topic/massdrop-announces-a-dan-durston-tent-2-people-2-hiking-poles-29-oz-199/
So the abrasion resistance of the X-Mid should be somewhere in between the 1.1oz silpoly in this table (which is actually a sil/PU - see the coating column) and the 1.1oz silpoly PU4000 (also a sil/PU but with a heavier PU coating). The more PU that gets added makes it more waterproof and improves the abrasion resistance, but with a negative effect on tear strength. I think the fabric the X-Mid uses runs the sweet spot here, as it has enough PU to have a excellent HH without as big of a tear strength penalty as the PU4000 fabrics.
Note that the abrasion resistance for these two silpolys is listed as "medium" or "high", while 1.1oz silnylon is listed as medium. So the durability of this sil/PU poly may actually exceed silnylon in a floor application where abrasion resistance is paramount.
Jul 11, 2018
dandurston
5116
Dan Durston
Jul 11, 2018
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a_aaYet one more point: The UV resistance of polyester is far higher than nylon, so it is quite possible that polyester overtakes nylon in terms of tear strength in the longer term. Nylon starts out higher but degrades faster.
For more reading on this topic, check out: https://backpackinglight.com/forums/topic/silpoly-tarp-durability/
Jul 11, 2018
a_aa
6
Jul 11, 2018
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dandurstonMy Borah Snowyside eVent Bivy actually has a "floor" made from the 0.93 MEMBRANE Silpoly, and as the table shows, it is not very durable, but just about sufficient if I'm a little careful. Outstanding HH for the weight. However, I would have liked it with a pure PU side for easy repair (tape instead of SilNet) - when I discussed this with John West from Borah, he could not recommend the MEMBRANE Silpoly PU4000, because of "abysmal tear strength" - as seen in the table. This is a couple of years ago, and I'm aware that there has been a lot of development on the polyester front - and it certainly seems that durability has improved since then :-) It's funny, I actually have two tents and a tarp made with nylon with silicone on one side and PU on the other. A tent from Exped (Orion III UL), a tarp from Sea-to-Summit (Nano TarpPoncho) and a (tarp-)tent from Golite (SL 1) - the first two are expensive and the last went bankrupt ... So the point of finding a good material suited for the entire thing to keep costs and prices down, strikes me as a very good one. :-)
Jul 11, 2018
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