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Jerseyhiker
3
Jun 19, 2020
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dandurston
5116
Dan Durston
Jun 19, 2020
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JerseyhikerAs you mention, polyester has advantages of not absorbing water weight and not expanding when wet. The latter is a major advantage because nylon expands 3-4% when wet, which is a lot (e.g. that's 6" of loose fabric over the arch of a tent). For a traditional poled tent that means wrinkly fabric and perhaps the fly sticking to the inner, whereas with a trekking pole tent that a bigger problem because the canopy is part of the tent's structure (e.g. nylon becomes structurally unsound as it sags). The water weight advantage is important too because poly doesn't absorb water into the fibers, while nylon does and which can add 1/2 lbs pretty easily to the tents weight and make it slow to dry.
Polyester is rapidly rising in popularity since the debut of the X-Mid, with many companies now offering poly tents (e.g. Six Moon Designs, Black Diamond, LightHeartGear, TrekkerTent) and others likely to start (e.g. TarpTent). I'm not taking credit for that because some of those were using it before the X-Mid, but the X-Mid has certainly raised the profile of polyester as a tent fabric.
The reason polyester is only gaining popularity now is mostly because lightweight versions of it weren't available until the last few years. Historically you could only get heavier polyesters (e.g. 40-70D) which have been used in tents for decades and are quite popular in mountaineering tents, but too heavy for a lightweight tent.
Unfortunately the adoption of polyester has been slowed by misinformation about the tear strength of poly which is spread by companies selling nylon tents and consumers reading that info. I say "misinformation" because (1) tear strength isn't actually that important as explained here by the most prolific tent designer of all time, and (2) nylon isn't stronger than poly in real world scenarios. For the weight, nylon does have a small edge in tear strength in lab tests, but this different is commonly wildly overstated. If you look a reputable source like this materials guide from DuPont it lists polyester as being 99% as strong as the best formulation of nylon (Nylon 6.6; see Table II-2). Others will argue nylon has an advantage more like 10%. At the absolute most, the difference is 20%.
Now let's say the difference really is 20%, which is being charitable to nylon. That doesn't translate to a real world advantage for two reasons:
1) Nylon loses tear strength rapidly under UV exposure - especially lightweight nylons where the UV can penetrate well into the fabric. A new nylon tent can lose 20% tear strength in a few days of sun, and nylon tents have commonly degraded to under 50% of their original strength after a few years due to UV, whereas polyester is virtually immune to UV degradation (the same dose that degrades a nylon tent by 90% might degrade poly by 1%).
2) Nylon loses about 10% strength when wet.
So if you test two brand new tents, yes nylon has a slight edge. But if you take those two brand new tents out in a wet storm, nylon will lose 10% and probably isn't any stronger. And then with continued use the nylon tent will degrade to be much weaker than polyester. That's why I say nylon has no practical tear strength advantage. It's the poly tent that will have longer span and be stronger in continued real world usage.
Of course we are talking about lightweight fabrics here. 20D is a light fabric regardless of weather it's nylon or poly. So taking care of it is wise. There's over 5000 X-Mid tents out there now and I've never heard damage to the fly that might have been avoided with a stronger fabric, but it is possible to damage the floor if you're camped on sharp rocks or sticks. So the best practical advise is to be careful with where you pitch it. A second point is that you do want to pitch the tent well so the fly is loose and potentially flapping/rubbing on the ground during a windy night. I did see one fellow get some abrasion damage to the edge of his fly in this scenario.
Because of everything I've just explained, there's little rationale to using nylon for tents anymore. Polyester is similar or better in every important metric, and there are new formulations of polyester coming out that aren't commercially available but are much stronger than nylon. So the change will take time but we're seeing a lot of companies switching to poly and I think that will continue such that in another 5-10 years nylon will be rare in tents.
(Edited)
Jerseyhiker
3
Jun 19, 2020
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dandurstonThank you so much for the reply - as you mentioned a lot of us have read articles or seen lab tests showing that nylon is stronger than Poly - and thank you for linking the articles you did! Can't wait to take my x-mid out on the rocky hills of NJ soon - if the shelters would start opening ;P
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One question I did have that I haven't seen covered to much in the posts is in regards to the choice of polyester vs Sil-nylon? I know that Poly doesn't retain water or stretch out as much when wet, which is why you went with a Poly construction. I have found though that poly does tend to tear easier than nylon and was wondering how much that weighed into your choice of material or what precautions were taken in the production in light of that? Not that I'm speaking a future rip into existence - I was just looking to see if you had any insight into the production process or ideas of how to safeguard against tears (if that should even be a concern with the x-mid's particular construction).