American Silnylon not Acceptable?

[Richard Nisley]

Matt,

Yes. See:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=24349&startat=28

[Jack H.]

Interesting… production moving overseas from the "cottage" business…

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[Lawson Kline]

Hey Jack,

Didn't you know there were cottage factories in Asia.

[Ken Thompson]

At what point does the cottage get replaced with a factory?

[Lawson Kline]

When you move your manufacturing to Asia I would say your no longer a cottage gear company..

[Jack H.]

Lawson :) Yep, I'm aware.

I bet we could get this lady to vamp up production for cuben.

[David Ure]

Water falling within a column doesn't mimic wind squalls so I wonder if that plays a significant factor. I agree with David that a steep pitch of silnylon doesn't get the full effect. In other words, there is a good chance that HH becomes less of an issue. It is not like there are many flat topped UL silnylon shelters, at least that I can think of first hand. There is a reason rain jackets are waterproof to 10,000mm and up.

But what about silnylon floors? The pressure of a 200lb person putting much of their weight on a knee under a very wet ground? I have had seepage this way.

What about sun exposure degrading silnylon fabric? Maybe this is also a durability issue? Older silnylon exposed to the elements may become decidedly less waterproof more quickly than silicon coated fabrics.

Regarding the quote from MSR – I am quite sure that they do not use silnylon in their tents so maybe not a fair comparison given the above.

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[David Lutz]

Ron – Congratulations on your success!!

[Roger Caffin]

Hi all

I guess I had better explain a bit.

I spent 27+ years in Textile Research with the CSIRO, ending up as a Senior Principal Research Scientist with a large team under me.
I have a Suter tester (it measures the pressure rating of a fabric) of my own and I have been testing (on my own behalf) light-weight coated fabrics for many years (6+).
I have tested many of the fabrics from the various suppliers in the American cottage industry – (thanks to various people including Sam for all the samples).
I keep seeing claims of 'our silnylon is superior', but I have yet to find a sample that really is superior. Some show normal variation; others are actually inferior.

I have tested Asian fabrics which are nylon 6.6, have a pressure rating several times that of the stock American silnylon, and are slightly lighter than stock silnylon. (Also polyesters.) Some of those fabrics have pressure rating of up to 80 kPa, compared to stock Westmark silnylon which is around 15 kPa.

The old 'wet-look' Westmark silnylon also got to 80 kPa, but the coating company (Duro) had its coating line closed down by the EPA because it was releasing too much solvent into the atmosphere. They could not be bothered upgrading their plant. As noted by some, operations in Asia are not restricted by the EPA.

The current Skylite silnylon from Westmark is not designed for our outdoors use. It is designed for parachutes and for the huge blow-up advertising puppets you see outside (or on top of) shopping centres. Neither of those markets have a water-pressure requirement. Unfortunately Westmark does not feel enough market pressure to improve the pressure rating – perhaps because those outdoors companies which are concerned have simply gone to Asia for their fabrics.

Some people have claimed that Asian fabrics are inferior. Nice try guys, but no cookie. Some (most?) of the world's major high-tech textile companies are located in Asia. You have only to ask what happened to Pertex: the UK holding company sold the brand and tech knowledge to Mitsui.

Now for some technical details. Please note that every statement made here is one based on actual measurement or observation. No guessing at all.

You might like to note that 10 kPa is roughly equivalent to 1 m (1000 mm) water pressure. I tend to work in kPa.

I will have to take some photos of pressure testing. A fabric with 20 kPa pressure across it is bulging quite significantly. When the fabric gets to 80 kPa (8000 mm) presure the bulge is … startling. Or alarming.

The idea that a tent fly (tarp, whatever) will experience broad pressures of 15 – 20 kPa from rain is mostly unreal (typhoons excepted!) imho. The tent would explode from the ground due to the forces involved. And you won't get spot pressures on a fly like that either: the existing surface film of water dissipates the impact of every (non-typhoon) rain drop very well. Water flows; bullets don't.

However, you can easily get 60 kPa on a groundsheet when you kneel on it. That's where the problem really arises. That is why so many companies use a heavier fabric for the groundsheet: they don't want customers getting wet knees. Customers don't want wet knees either …

Misting
I understand that some people like to blame their tent for their getting wet inside. But just wanting to blame someone else is not a substitute for proper testing and decent science. So-called 'misting' is condensation being popped off the inside of the tent due to the impact of raindrops. (There is one exception I will come to later.)

Why should one get condensation on the inside of a fly/tarp/whatever when it is raining? The reasons are a shade complex, but the effect is at least partly driven by the way the temperature of the fabric is lowered by the cooling effect of the rain. You get a wet outer surface and the water on the outside starts to evaporate a bit, cooling the fabric. Ever seen your windscreen fog up inside when it is raining outside? Same effect. So you turn on the heating a bit and warm up the windscreen.

On the inside of the tent you have a person who is warm, possibly with damp clothing, and the ground is wet, all evaporating away. That makes the inside of the tent around 100% RH, but at a slightly warmer temperature than the ambient, and even warmer than the fabric. When that warm saturated air hits the colder fabric, condensation happens. Yes, this can happen even with some ventilation due to a breeze: the breeze may just be cooling the fabric down even more by evaporation.

For the doubters – note that you can get condensation even when it is not raining, like under a clear sky. The fabric is cooling down here because it is losing heat to the night sky by radiation. The night sky can look as low as -70 C (-94 F). You don't need many degrees of temperature drop for condensation to happen.

Yes, there is one exception, and that is EPIC fabric. This is funny stuff. It has air-flow but blocks water – up to an abrupt threshold. That threshold is set by the surface tension of the water on the coating on the fibres, and is around 15 kPa for clean new fabric. BUT, get dirt, skin oils, vegetable oils, or anything else, on the fabric, and the surface tension effect is shot to pieces. Then the fabric starts to leak like an uncoated fabric – at essentially zero pressure. So your nice new EPIC tent is waterproof for a few days, then collapses.

Where do we go from here?

It seems that the silicone coating is porous under pressure. I am not talking about a few leaky spots here and there. I mean the silicone polymer seems to be actually micro-porous. Under pressure the threads inside the fabric start to get wet. I have watched this happen during testing. However, when I test a fabric with a PU coating on one side and a silicone coating on the other, I see thread-wetting from the silicone side but not from the PU side. Yes, that means the PU coating is inherently more pressure-resistant.

The old PU coatings which sat on the surface rather than going into the fabric actually weakened the fabric, while the silicone coating/impregantion does strengthen the fabric. However, we now have PU coatings which go into the fabric the same way as the silicone coatings do. I expect these to strengthen the fabric.

So I am currently betting on the future being fabrics with a silicone/PU coating – either as a copolymer or as a different coating on each side. And they will be coming from Asia, as so far the American suppliers show no sign of competing.

Cheers

[Roger Caffin]

> So a thunderstorm can produce 11,000 mm head and a Typhoon 20,000.
Not sure about the thunderstorm, but Typhoons … anything goes. The whole tent would probably go too…

Cheers

[BlackHatGuy]

It seems to be pick on SMD day on BPL. FWIW, I just went to Ron's site, and nowhere did I find any statement where Ron calls SMD a 'cottage gear company.' That's a label we're imposing.

At some point every successful business that deals with textiles has to make a decision based on future goals. Some stay small by choice, some desire to grow and make the necessary decisions to make that happen. Nobody's wrong. Different goals simply lead in different directions. I, for one, wish Ron all the best as he tries to successfully expand his business. Hopefully he won't fall into what many here would consider the trap of pandering to the larger audience by adding weight/unnecessary features/etc. Time will tell.

As far as going to Asia means you're no longer a cottage gear company, how specific do you want to be on that? Only the stuff you produce yourself? Only the stuff you produce yourself with textiles? Or anything you carry in your store? Lots of arbitrariness in there.

[David Ure]

Roger – your post is bloody brilliant. Thank you!

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[Konrad .]

Roger, that was very thorough…easily could have been a member's only article on BPL's homepage. Thank you for that!
I too am a firm believer that high quality textiles can be found in Asia…a lot of times we don't see it here in the States because the the end user who imports it doesnt find it cost-efficient to use/sell it here domestically. Lawson, Asian-mills definitely can and will follow a set std. My folks have been in the wholesale textile industry for about 30 years now, and do import Taiwan manufactured hardware, webbing, and fabrics that meet Mil-Spec stds. But as Ron mentioned, unless you're importing large wholesale quantities, it's simply not worth it to freight in the quality stuff. The profit margins are huge for the cheap stuff, and that's why you've probably seen so much of it

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[Ron Moak]

Roger writes >> The current Skylite silnylon from Westmark is not designed for our outdoors use. It is designed for parachutes and for the huge blow-up advertising puppets you see outside (or on top of) shopping centres. Neither of those markets have a water-pressure requirement. Unfortunately Westmark does not feel enough market pressure to improve the pressure rating – perhaps because those outdoors companies which are concerned have simply gone to Asia for their fabrics. <<

For a bit of correction, Westmark is very interested in improving the quality of their fabrics. In addition they do have a Suter tester, which I saw when I was there in October. I know that we and other customers have had numerous conversations along these lines.

To be fair, as Roger mentioned, our industry still constitutes a small percentage of the fabric used in industry. In addition Westmark is neither a mill or nor does it coat the fabrics. So they must work with their suppliers who may or may not see any incentive to change.

As to the Silnylon fabrics with one side PU coated, Roger maybe correct as to it rating. I don't know, I've not used it nor tested it. When we get samples of fabric, in addition to the water resistance are strength tests for warp and weave. In all of the sil/pu coated fabrics I've seen, the strength was signficantly less than the those that had silicone only coating.

Is this true for all of these fabrics or just from a couple of mills I saw samples from? I couldn't say. Also I have no idea if the PU coating will mold, mildew and delaminate like PU only coated fabrics. Until we can find a fabric that has an equivalent strength, and won't mold, mildew or delaminate; we'll stick with silicone only fabrics.

[peter vacco]

" Roger – your post is bloody brilliant. Thank you! "

yeah. just like that other guy said …

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[Mary D]

You're so right, Iceaxe! When I first joined, I spent days and days reading articles. I still keep running across articles I haven't read yet! Frankly, I have found many of the articles from earlier years to be more useful than most of the current ones!

[Andrew Schriner]

Roger – many thanks for sharing your expertise.

Newton – thanks for throwing the question out there and setting off this cascade.

[David Olsen]

Roger-

Did you ever test the red sil/pu coated fabric I sent? It was 1.9 oz base with a .5 oz
coating one side with a blended coating. It was domestic (US) goods.

Also for a time I could get domestic 30d with a blended coating on both sides. Other
than looking and feeling a bit more rubbery it seemed to function the same as the
Dupont patented process for coating with sil. It was made in the same mills, don't know why they changed formulas
at the time.

The only samples of silnylon from Asia I have received were NOT type 66 nylon. Tho they
were cheaper and had what seemed like a decent coating, the tear strength was the same
as the cheaper 70d pu coated types.

There are some nasty solvents used to apply the coatings. The method Dupont uses recaptures the solvents.

[John Donewar]

Andy,

Inquiring minds wanted to know. ;-)

You're welcome.

Party On,

Newton

[Mat Tallman]

"When you move your manufacturing to Asia I would say your no longer a cottage gear company.."

Your willingness to shamelessly bash another manufacturer (a highly successful and well respected one at that) in an open forum has definitely removed my willingness to buy from you in the future.
You might consider altering your tone, Lawson, lest you forget that the perception of members of this forum, your primary customer base, drives your business.

Weren't we talking about material quality here?

[Author]

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