Drop + Dan Durston X-Mid 1P Tent Discussions | Drop

Jul 7, 2018

KatherineKThe great thing with polyester is that it doesn't sag in the rain like nylon.
Virtually all tents are nylon because lightweight waterproof polyesters weren't available until recently (prior to about 2 years ago you could only buy 40D and up polyester). Nylon is very strong, but it sags in the rain so tents can end up limp in the morning. This isn't a huge problem for traditional tents that use spring loaded poles, since that takes up some of the sag, but trekking pole tents can look terrible after a night of rain if they're made of nylon like nearly all of them are. So if this can be eliminated, it's a huge improvement.
So poly isn't quite as strong as nylon but it's still strong enough. Eliminating sag is worth this. Also, because you can get sil/PU polyester now, you can seam tape on the PU side so the X-Mid comes fully seam taped unlike every silnylon tent. So overall it's a big step forward. The industry is switching to polyester, but slowly. For example, Yama Mtn Gear uses poly in their Swiftline 1P tent, and Six Moon Designs just switched to poly for their new generation of the Lunar Solo
For more on this topic read: http://thetentlab.com/MoonLightTents/PolyNyl.html

Jul 7, 2018

KatherineK

Jul 9, 2018

dandurstonfollow-up: tell me more about why about the PU in the 2000mm sil/PU coating. Normally I read PU = more mainstream tent. Is it about the taping vs. seam sealing?

Jul 9, 2018

Vote

Jul 9, 2018

KatherineKWith silnylon you can get a HH anywhere from 600mm to 3500mm depending mostly on how thick the sil coating is. So you can get very waterproof silnylon. But for reasons unknown to me, silpoly is only available with moderate waterproofness (1000 - 1500mm). If you want polyester that is more waterproof, you have to go with a sil/PU coating. This coats the poly with sil on one side and PU on the other.
The nice thing with sil is that is strengthens the fabric, which PU does not. But the nice thing with PU is that it isn't super slippery like sil and it can be seam taped. So sil coated tents can be annoyingly slippery inside so your mat slides around in the night. And they require users to seam seal which is a hassle and can add 1oz to the weight. So going with a sil/PU blend is nice because the sil is on the outside where it strengthens the fabric, while the PU is on the inside and gives a non-slip floor and a seam taped tent.
So the sil/PU has nothing to do with cost. It's based partly on whats available and partly on what works best. Even if higher HH silpoly was available, I still think sil/PU poly would be the way to go for its non-slip and seam taping.

Jul 9, 2018

KatherineK

Jul 9, 2018

dandurstonthanks for the replies. planning to order.

Jul 9, 2018

Unnamedpeaks

Jul 15, 2018

dandurstonDan, why is seam taping an advantage? I don't mind seam sealing with silicone, and every product I have ever owned that had seam tape has failed. The seam tape delaminates before the product is worn out... The next thing to go has been the polyurethane, which also delaminates and crumbles. . I would be much more excited about this tent if it was made with silnylon.

Jul 15, 2018

Vote

Jul 17, 2018

UnnamedpeaksThe polyurethane you're probably thinking of is polyester based PU, which ran rampant in the outdoor industry for a long time and indeed "degrades and crumbles". This is poor stuff. The good PU is poly-ether based PU, which is radically more durable and only recently has enough attention been drawn to this issue that the fabric makers have shaped up. The X-Mid uses poly-ether based PU and should give you no long term durability troubles, since it doesn't absorb water, get sticky, weaken, crumble etc like the polyester PU. I know it's counterintuitive for a polyester fabric to have a poly-ester PU, but that's how it is. For more on this topic see the post by Geoff near the end of this page: https://backpackinglight.com/forums/topic/silpoly-tarp-durability/
With regards to seam taping, if you have any concerns with it you could easily just seam seal it yourself since the outside of the material is silicone coated. Then you'd be super safe with seam sealing outside + seam taping inside. I like the seam taping because seam sealing it myself usually involves buying a container of mineral spirits and tube of silicone- most of which ends up in the garbage eventually as I only need a tiny bit. Plus a fair time of time. So time, money and environmental waste. But it does work well. The seam taping should eliminate this task and I think it'll work well, but again, if it ever starts to delaminate on you then you could just seam seal the outside like any silnylon tent. So I don't really see the harm in it other than a few grams.
The main thing I don't like about silnylon is the sag in the rain - particularly with trekking pole shelters as there is no spring in the pole set to take up that sag. While indeed silnylon has a stronger tear strength, I think this argument is largely academic, as 20D silpoly is plenty strong for backpacking use. I've never heard of someone with a properly made 20D silpoly tent encounter high winds and have their shelter rip. So with silpoly you get a practical advantage (no sag) and what you give up in exchange doesn't really make a difference in the real world IMO.

Jul 17, 2018

Tullochgorum

Dec 16, 2018

dandurston @dandurston Yay - that's me that you quoted on silpoly PU durability! Mike Cecot-Scherer is probably the most experienced and informed lightweight tent designer around, and he was very generous with his advice. He's a huge fan of silpoly PU, because of its greater dimensional stability in the wet, and he feels that silnylon is pretty much redundant these days for ultralight shelters. He points out that the stretch on wet silnylon means that panels don't perform as designed in the wind, so silpoly is inherently more stormworthy. And in his extensive experience the ether-based PU lasts just fine. The coating does weaken the fabric a little, but he argues strongly (on the basis of wind-tunnel testing and field experience) that it is still plenty strong enough provided the tie-out points are properly reinforced. He also points out that while silnylon is theoretically a bit stronger in the lab, it degrades much faster in UV. So after a bit of exposure, silpoly is at least as strong. Dan has made the right fabric choice here, without a doubt.

(Edited)

Dec 16, 2018