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

Edited by Konrad1013 on 02/09/2011 18:02:21 MST.

.

Edited by Ice-axe on 01/09/2013 20:15:29 MST.

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.

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

yeah. just like that other guy said ...

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Edited by Ice-axe on 01/09/2013 20:16:47 MST.

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!

Edited by hikinggranny on 02/09/2011 19:30:42 MST.

Roger - many thanks for sharing your expertise.

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

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.

Andy,

Inquiring minds wanted to know. ;-)

You're welcome.

Party On,

Newton

"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?

The general perception of a "cottage manufacturer" is someone who (perhaps in conjunction with family members) is doing the work pretty much alone, often in their garage. Kooka Bay and Goose Feet as new, one-person firms come to mind here.

Once these firms expand to the stage of contracting out work (such as sewing) or hiring more than one or two employees, IMHO they are not really "cottage" any more. That doesn't mean that their standards have fallen but just that they are a slightly less small business! I'm thinking of Tarptent, Six Moon Designs, ULA and Gossamer Gear as examples.

While I'm of course unhappy to see some of Ron Moak's manufacturing go abroad, I recognize what he's up against trying to stay domestic and congratulate him on his expanded business! I suspect we'll find within the next few years that other small firms who currently contract their work in the US will end up going the same way, like it or not.

Once a business has grown so that the multinationals or at least the big domestic corporations buy it out, then we have to start worrying that the business will end up like the North Face--as appears to be happening with GoLite, getting progressively less "lite." We pray that doesn't happen to any of our beloved small specialized lightweight gear firms! The buyout makes a nice retirement package for the original owners, but in the hands of the big corporations the merchandise goes south!

Edited by hikinggranny on 02/09/2011 22:43:33 MST.

I agree Mary, the progression often goes that route. I suppose I was put-off by Lawson's implication that because Ron was forced to outsource some portion of his manufacturing, that he was going by the wayside and that his product was then somehow inferior.

As in the cases of golite and others, let the gear speak for itself. If, in a year, quality has taken a hit, or the designs do not carry the same UL principles, then draw your comparisons.

It also amuses me how many people on BPL hammer companies that manufacture outside the US, but I venture a guess that the vast majority of these people are also driving themselves to work everyday in a non-domestic automobile.

Again, weren't we talking about silnylon waterproofness?

Hi Dave

> 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.
I did, and I thought I had emailed you the results.
But blowed if I can find the results now.
scruffle scruffle scruffle ...
I measured the weight as 87 gsm, which is just a little over the 2.4 oz quoted. I will have to measure the pressure rating again.

Cheers

Richard

Thanks for the link to your table of rain drop size versus pressure. I'd be very interested in the calculations behind your figures. I have to admit the figures are somewhat higher than I would have expected.

>>> Wind also influences the water pressure of rainfall. When subjected to wind velocity of 20m/sec (44.7mph-comparable to a typhoon), the static pressure of rainfall is estimated to reach 20,400 mm <<<

The effect of wind is very relevant. Here, atlantic lows bring rain in the 2-4mm range often driven by strong wind. The 45mph you mention would not be unusual at all - we have had wind speeds of over 170mph recorded at both high and low altitudes!

Edited to add:
I did some research on measured rain drop pressures and came up with this:



The limitations of the transducer used meant that the first 3us could not be calculated. The text in the paper added "the peak pressure should be dependant only on drop velocity (8-9 m/s in this experiment) and not drop size. However the pressure after peak will reduce faster the smaller the drop size. By 50us the pressure for all drop sizes had reduced to approximately 100kPa."

Pretty big figures. However, a fabric is not a rigid surface and should presumeably result in lower figures. How much lower? I have no idea.

Edited by Scunnered on 02/10/2011 10:00:24 MST.

Wow, I'm learning a lot on this thread. What a pleasure. Roger, you rock!

Here are 3 ways to deal with less than totally waterproof tent fabric:

(1) I use uncoated floors in the tents I make for myself. I rely on an added ground cloth and/or my closed cell foam for protection from ground water. I don't have to worry about light coatings allowing my knees to get wet. The uncoated walls also eliminate condensation on bathtub walls(biggest source of wetness on my sleeping bag).

(2) Solid fabric inner tent ceilings do much better with drips and misting from the fly than do mosquito net ceilings. Drips tend to run down fabric but go through mosquito netting.

(3) Steep fly walls (45 degrees or steeper) really help with keeping rain moving toward the ground rather than working its way through the fly.

Cottage Industries? Well nothing stays the same. My first backpack was a second that Jan Sport was selling out of a 1 car garage.

Edited by lyrad1 on 02/10/2011 14:16:37 MST.

The question of what defines “waterproof” applies to garments as well as shelters. Note that although Polartec wanted the maximum possible breathability, they engineered their new WPB membrane so that the pores provided 10,000mm of hydrostatic head; typical rain drops worst case. Also note that the US Armed Services specifies a garment waterproof level of 17,586mm hydrostatic head; typical thunderstorms worst case. Most of the time it is the hood and shoulders that first wet through on garments because they don’t have the force dispersion angles or give that the rest of a garment does.

Shelter flies and roofs are a special case in which most of the industry isn’t providing waterproof fabrics except for some floors; they are providing a “functionally equivalent waterproof” shelter. Conventional double wall tents commonly use outer fabrics with hydrostatic head rating from 1,200 mm up to 5,000 mm. Kelty was the first tent manufacturer to use light tent flies. They found that the force dispersion angles and the separate inner tent allowed the occupant to be satisfied using a lighter coating even though water passed through the fly. What happens in a heavy rainfall is that water does go through the taut fly layer and runs down to the ground along the inside surface. A little will drip onto the inner wall but since it was not under pressure it will barely dampen it. Because the inner tent is breathable, the moisture from humid air and from the exhalations of the humans inside would not condense on the inner tent walls but would pass out to the outer fly and leave the inner wall dry. They found that they didn't get double wall customer complaints with as low as a 1,500 mm fly rating.

Single wall silnylon shelter's flies and roofs are not technically waterproof but they can be engineered to be “functionally equivalent waterproof” shelters. Any given shelter’s design and hydrostatic head that provides a tolerable amount of customer complaints is what defines a “functionally equivalent waterproof” shelter.

Shelter floors are subject to different forces. The pressure applied by the knee of the average 165 lb. male is 11,255 mm. This is the typical definition of a waterproof floor's hydrostatic head.

Edited by richard295 on 02/10/2011 11:58:40 MST.

Hey Mat,

If my American pride upsets you, I am sorry.. I just find it ironic that moving your manufacturing to Asia is now considered an Accolade.. Maybe someone should tell Thermarest, Nalgene, McNett, etc...

Stuart,

The general calculations behind the figures you requested are as follows:

The density of water is 1g/cm^3 (1,000 kg/m^3).

Terminal velocity of the smallest 0.002 m diameter raindrop (2.0 mm), neglecting turbulence and updrafts, is 6.4008 m/s, or about 14.3 mph.

The volume of a 0.002 m diameter raindrop is given by (4 * pi * r^3) / 3 = 4.189E-9 cu m.

So with a density of 1,000 kg / m^3, the mass is 4.189E-6 kg (4.189 mg).

The force behind the minimum raindrop is Mass * Acceleration (gravity) = 4.109E-1 N.

Pressure on your fly by this single raindrop is Force / Area; o Area = 3.142E-6 sq m.

This gives that individual raindrop's force as 13.08 Pa or in more common US terms 1.897E-3 psi

For grins on your next UL backpacking trip carry the foil wrapper from a piece of gum. If you feel misting in your single wall shelter, briefly place the wrapper in the rain. The drops will make dents in the foil that are on average 50% larger than the size of the drop. When you get home you can measure across each the largest dent to get an approximate idea of the droplet diameter. Then you can calculate what the force was using the general procedure outlined above.

Edited by richard295 on 02/10/2011 12:37:11 MST.

>>> The force behind the minimum raindrop is Mass * Acceleration (gravity) = 4.109E-1 N. <<<

Really?
The force of gravity is balanced by air resistance when the drop is falling. The force on the fabric is the decceleration of the drop as it hits. This is a very different, and dynamic, figure as the image above shows. The force, and the area over which it is exerted is not at all easy to calculate.
A very simple approximation can be found by using delta momentum = impulse
m.v^2 = F.d
where d = diameter of drop

Edited by Scunnered on 02/19/2011 02:03:09 MST.

I am amazed by the figures quoted here.
7500mm minimum water head ?
Really ? how come for years and well before TT and others came about, we have had tents that were and are still rated at 800mm or thereabout ?
I remember Ben pointing out that a very popular line from Eureka (Timberline series) has the fly AND floor rated at 800mm; beside what is the rating of the floor in all those shelters that don't have one....?
( that is how come people in their mids often with just a mat on top of a groundsheet, do just fine ?)
This reminds me of a comment at WB along the line that "the higher the bathtub floor , the more llikely you will get flooded " the point there was about location, made from a guy that uses an open tarp
Winds of 190 mph (later amended to 170) .. really ?
(BTW we had winds like that here, from a cyclone, however nobody was camping, just trying to stay alive above water in a few emergency buildings)
Do you expect any tent to stand up to that ?
And , in my experience, unlike some other fabrics that wet out and somehow lose some of the water head , silnylon remains the same. So yes you can get some mist within minutes but it will hold prolonged rain for days. I have done several test leaving my shelters up for days on end .
BTW, at least before they wet out, as far as I understand 800/1000/1200mm waterhead is the same regardless of the fabric/laminate in use.
A point that has been glossed over is that , as Richard pointed out, the misting in many shelters is somewhat masked by the inner , particularly the ones made of fabric or with a fabric top, however you may end up packing up a wet ,from the inside, shelter that in some cases will develop mildew and or delamination in the long term and at least result in a heavy shelter right away.
(again, weigh your shelter dry, leave it out in the rain for a few hours , then pack it up . weigh again. You will be surprised at the weight gain...)
Anyway, when you guys find a fabric/laminate that it is lighter/stronger/has abrasion resistance , a higher water head than silnylon,has better UV resistance, does not delaminate, can be seam taped, comes in your favourite hue, cannot form mildew /become sticky and is less than $20 per yard, ...please let me know.
Franco