American Silnylon not Acceptable?

Thanks for that good info, Roger

I was just in hard rain for hours and there was some misting – also a little condensation on the inside which could have been the problem – just a little mist on the outside of my sleeping bag – no big deal – I don't see why people talk about misting so much

Silnylon floor leaks in a large area under my sleeping pad – not from a foot or hand – there's something about a long exposure with a pressure that isn't very large

My silnylon pack leaks where some insulated clothing pushes against the inside. The clothing wicks the water off the silnylon. If it was a steep tarp wall there would be no problem, water would just flow to ground.

Jerry,
Appreciate your post. Thank you.

Gives me second thoughts about using even the best of the current generation of silnylon for floors. Would be helpful to know if your floor has actually been over puddled water, as distinguished from just wet ground; and whether you use a ground sheet underneath the silnylon. That could add to the pressure if water got in between the layers. Would guess from your post, and other posts about your gear, that you don't. I have the option of using 1.7 oz PU coated nylon (total wt incl coat) instead of 1.4 oz silnylon for a floor, and am in the process of deciding. The PU coat fabric was used by TNF for its lightest weight outer tent walls, and unlike some PU coated nylons, has not visibly degraded over the years. Stretched a piece over a pail and left it out in the rains all last Fall, and it held up fine, with no wetting out. But I still remember PU coated nylon floors wetting out and even leaking. Once they get that wet, they also get dirty, and are a bear to pack and carry, much more than silnylon in my brief experience with a silnylon floor on a rainy trek.

Your experience with the pack is more helpful still. Am assuming, again, that you are referring to the sil-coated 1.1 oz nylon, not the heavier stuff. All the same, it is the coating, not the heavier weight, that stops the water. The sil-coated 1.9 oz nylon from Seattle Fabrics is coated on both sides, the Warmlite is not; but they both weigh 2.4-2.5 oz/sq/yd total with the coatings.

Was thinking of using the heavier sil-coated nylon for a pack (not the pack bottom), because it is lighter than the D-P laminates. So, some second thoughts there also.
However, the heavier stuff would be quite less elastic, I think, and for that reason put less stress under pressure on the silicone coating, and thus be less leaky. I am thinking of Roger's deccriptions of silnylon fabric balooning on his Suter testing machines. He has opined, if I understood him correctly, that less elastic fabrics would not stretch so much under pressure, allowing less stress on the coatings, so have less leakage. So, if your pack is 1.1 oz base nylon, I'm still thinking 1.9 oz base nylon would do OK for a pack. Otherwise, maybe not.

Would appreciate and welcome yours and others' thoughts, comments.

"My silnylon pack leaks where some insulated clothing pushes against the inside. The clothing wicks the water off the silnylon. If it was a steep tarp wall there would be no problem, water would just flow to ground."

Leaky backpack fabric? Solution=garbage compactor bag liner.
Actually they all leak. Even the stuff that says it's leak-proof.. leaks. if it does'nt leak it sweats. The best bomb-proof solution(used by many a long distance hiker) is to line the pack with a garbage compactor bag. Make it your "sanctum-sanctorum" as Fletcher puts it. Just sleeping bag or quilt and clothes go inside.
IMHO forget about trying to make your pack water tight. Use the lightest fabric you can get away with and then simply line it with a cheap plastic bag.

"Would be helpful to know if your floor has actually been over puddled water, as distinguished from just wet ground; and whether you use a ground sheet underneath the silnylon."

wet ground – no groundcloth – 1.1 ounce seconds silnylon

when I put coating of silicone/mineral spirits it was totally waterproof, but that comes off after a while (50 nights?)

heavier weight silnylon might work

Cuben might work better

"Your experience with the pack is more helpful still. Am assuming, again, that you are referring to the sil-coated 1.1 oz nylon, not the heavier stuff. All the same, it is the coating, not the heavier weight, that stops the water. The sil-coated 1.9 oz nylon from Seattle Fabrics is coated on both sides, the Warmlite is not; but they both weigh 2.4-2.5 oz/sq/yd total with the coatings."

I used 1.1 ounce silnylon, which leaked.

When I coated it with silicone/mineral spirits it became totally waterproof. This hasn't worn off after a couple years.

I see no reason to have heavier weight nylon than this. I don't see any wear after a couple years. But then I don't do a lot of bushwacking and I'm fairly careful, so 1.9 ounce would be good too.

I'm even wondering about the pack bottom. Maybe don't need heavier weight.

Cuben would make a great pack – strong, light, and waterproof.

"However, the heavier stuff would be quite less elastic, I think, and for that reason put less stress under pressure on the silicone coating, and thus be less leaky. I am thinking of Roger's deccriptions of silnylon fabric balooning on his Suter testing machines. He has opined, if I understood him correctly, that less elastic fabrics would not stretch so much under pressure, allowing less stress on the coatings, so have less leakage. So, if your pack is 1.1 oz base nylon, I'm still thinking 1.9 oz base nylon would do OK for a pack."

The water leakage I have experienced didn't envolve the fabric stretching. Soaking through floor, through pack, or misting through tarp in heavy rain.

I didn't interpret Roger as saying that fabric stretching caused it to leak but I won't speak for Roger : )

then make your backpack fabric waterproof

it seems inellegant to use a bag inside or a pack cover. Then you have to fiddle with them. And it theoretically weighs more. I'de prefer to just have a waterproof pack.

One thing that works is to coat the cheap 1.1 silnylon with silicone/mineral spirits, then it's waterproof, and has lasted for at least a year.

Silnylon with thicker coating would probably work.

Cuben is waterproof I believe, not that expensive for the small amount required for a pack.

But lots of people use pack covers or liners – that works too.

Thanks, Jerry, for your comments.

Because you got better water resistance after adding silicone coating, I think you just needed more/better coating. I tried using heavier 2.4 oz silnylon for a floor, but it added more weight than I wanted to the tent.

One really good thing about silnylon is the ease of recoating or patching with silicone. There are recoat products for polyurethane also, but they never worked very well for me. Certainly not 50 nights.

So, your results with recoating both packs and floors with silicone really encourage me to stick with the silnylon. Recoating is exactly what Roger encouraged me to do with some not so good silnylon, but I didn't follow up because the idea did not sound very 'elegant', much as you felt about the plastic bags. But your comments lead me to rethink.

I like some other qualities of silnylon over PU coated: The lighter weight, the resistance to pitch and other gunk that tends to get stuck to PU, and much less wetting out in the time I've used it. So, because the coating can be refreshed, I will stay with the best silnylon I can find for both the floor and pack applications, and recoat as needed, as you suggest.

As for the heavier silnylon for packs; even if it is not more water resistant, it is a higher denier fabric, and more durable. While hiking off-trail in Colorado is not really bushwacking, it's still nice to have a more durable pack.

Many have gone to Cuben for these applications, but there is still a concern about the durability of the Mylar PET film. It stretches, but is not elastic. The high strength fibers are fine, but they won't keep out the water if the Mylar wears out, abrades or punctures. I'm going to try the Cuben for tent walls and flies first, see how it works out, and go from there.

Edit: Just re-read your comment on another thread about the "CT1K.18 Cuben – 0.75 ounce per yard2 – heavier mylar, light spectra – for tent/bivy floor" – maybe that is the answer if one can afford it.

Coating with solvent/silicone calk is not a cure all and thicker coats can tend to peel. I would suggest a thin coat, very thin, applied to both sides of the fabric. On the order of 20-30 parts solvent to one part calk. This leaves a thin skin far less prone to breakage from folding, abraiding and "running" peels. Based on my experiences in the northeast USA, this helps a lot with water resistance on siliconized fabrics.

Cuben is interesting because it IS highly water resistant. However, condensation with smaller volume tents is as much of a problem as is leakage. And, at 3000mm the floors leak if you lay on them. However a 10,000mm floor will actually hold up to sleeping in a puddle.

Cuben is really nothing more than a plastic sheet(well 2 thin sheets), reinforced with threads(heat bonded between the plastics.) As Jerry presented in his prototyping article, plastic works well for tarps but is fairly fragile. Cuben is a plastic sheet, without the fragility. But, the condensation is a bit worse. Venting needs to be a major consideration for tents made from this. It isn't enough to simply take older designs and use cuben coverings.

Like the old canvas, silnylon relies on water tension for water resistance. This simply means that water has a "skin" of it's own that is quite strong (you can look up the numbers.) The extremely fine weave of any nylon will lend a degree of water resistance to it by supporting this film. The siliconizing agents do little more than make the nylon hydrophobic, supporting the water skin. This also means that you can touch it without the leaks associated with touching canvas, since, the fabric will not wet out (except under high pressures. ) This also means that any very small imperfections, we are talking microscopic type imperfections, here, will leak or mist under impact pressures. We have all encountered this. Most is condensation being banged off the inside (exacerbated by the water film closing all breathing space and building up more,) but some is through the fabric. Both contribute to interior misting in a hard rainstorm. Indeed, a new tarp may resist this for a short time, but after a couple heavy rains, it will mist (as the coating elongates and breaks with water droplet pressure on impact.)

The hydraulic pressure of the impact can exceed the quoted numbers. This is due to the small “pocket” size of the silicone coatings. It will form a slight dimple. Similar to an armour piercing shell from an explosive, this can compress the impact forces into the pocket. This can greatly exceed the water impact forces that were mentioned. So, going with an 800mm sidewall on a hoop tent is a good way to get wet. Indeed, I expect that it will well exceed the wet through of any siliconized fabric, Asian or American.

The solution, though inelegant, is to use two layers. First, break the impact of the water droplet and second, to provide “waterproofing.” In the interests of weight conservation, this is not usually done, though. So, we have this same conversation, usually based on the differing conditions encountered by and the expectations of those in the hiking/camping community. Soo (ha ha, a lot of words, I guess,) it all depends on who you are selling to, where they are camping, and what they expect from “waterproof.” Few will understand the technical aspects, nor care.

Politics acknowledged but put aside for the moment.

@ Roger Caffin,

@ James Marco,

@ Franco Darioli,

@ Marc Penansky,

Your input and information gathered from facts and experience is much appreciated. The OP asked the question "Who actually has the good stuff"?

The intent was to inform us MYOG types where to go for the best material for our projects. Learning the why it works and the science of it all is a valuable bonus.

As it seems to me what I have learned from this thread;

1) Silnylon is water resistant.

2) Double coated is better

3) A taut pitch will keep you drier even if your material isn't the best.

4) To get the quality you want ask questions and request specs.

5) There will be an intersecting point of lines of quality, cost and waterproofness.

6) Number 5 is known as a Compromise.

7) I have always be able to trust my small collapsible umbrella to keep my bald head dry in a downpour even though I do not know where I purchased it from, what its hydrostatic head pressure ratings are, if it is single or double or coated at all, what its yarn count is and wether or not it has been Suter tested. :-)

Party On,

Newton

It would be nice if someone sold silnylon that had a thicker coating for a floor or a pack.

Fabric sellers are very short on specs. Maybe they'll have the weight of the fabric before coating. and the cost per yard and fabric width (that can be off a few inches either direction). and that's about it.

It would be nice if they had more specs, and like whether it would be good for a floor or sidewalls. But then different users will have different experiences and complain.

Jerry,

"It would be nice if someone sold silnylon that had a thicker coating for a floor or a pack".

I probably needed to add a number 8 to my list. See below.

8) Since it seems silnylon will leak water through if enough direct pressure is applied to it. Also it seems that the pressure exerted by the human body lying on the material or elbows, knees, hands and feet exerting localized pressure will result in leaks.

IMO the choice of a material for the floor of a bivy or tent should be PU coated 1.9+ oz. nylon or something else more substantial and waterproof (a.k.a. cuben). The coating would go towards the inside of the bivy or tent and the nylon fabric would go towards the bottom or exterior side.

Does anyone know of a nylon fabric with a PU coating on one side and a silicone coating on the other side? The silicone could help to repel and shed the water while the PU coating could hopefully hold back the water.

Party On,

Newton

Or…add a silnylon groundsheet to effectively double the HH. It would weigh about as much as a 70d PU floor.

After I treated my silnylon floor with silicone/mineral spirits, it was waterproof

Only problem is eventually it starts peeling off

Based on this, I would think a 1.1 ounce nylon with extra heavy silicone coatings on both sides would make a good floor

I hate to have to have a seperate ground cloth. Weighs more. It just seems inellegant.

>>> Does anyone know of a nylon fabric with a PU coating on one side and a silicone coating on the other side?

Nylon tent fabric silicone/PU-coated, 80g/sqm http://www.extremtextil.de/catalog/Fabrics/coated/Nylon-tent-fabric-silicone-PU-coated-80g-sqm::1162.html

But a plain PU coating has a higher hydrostatic head: Groundsheet, Nylon, PU-coated, 90 g/sqm http://www.extremtextil.de/catalog/Fabrics/coated/Groundsheet-Nylon-PU-coated-90-g-sqm::460.html

Hi Jerry

> I am thinking of Roger's descriptions of silnylon fabric balooning on his Suter testing machines. He has
> opined, if I understood him correctly, that less elastic fabrics would not stretch so much under pressure,
> allowing less stress on the coatings, so have less leakage.
Yes, the nylon fabric does bulge upwards under pressure. Quite alarming at first.

But does the stretch increase the chance of leakage? I am not so sure about that. You see, silicone polymer is very elastic, and I think that the amount of stretch due to the nylon fabric under those conditions is probably not much more than 5-10%. In my experience silicone polymer can handle a lot more stretch than that without breaking.

However, there are two other factors to consider here. The first is that I THINK the silicone polymer is actually slightly micro-porous. I know that it is very slightly soluble in water. Yes, I really did mean that. So a very thin silicone polymer coating can thin out over time.

The second factor is really some blind lack of careful thought by gear manufacturers. They insist on using a RipStop weave rather than a plain weave. You have this nice regular fabric surface (the plain weave) for the silicone to get into, then suddenly you interrupt that with one or two great big fat threads for the ripstop. Not only that, but you have these fat threads crossing over. So what happens when the fabric is pressurised in a Suter tester – or under your knee? At first, and for a long while above that in pressure as well, ALL the leaks happen at the ripstop cross-overs. The sudden discontinuity in the fabric surface is a real source of weakness in the coating. I don't see many leaks in the plain weave area. In fact, a fabric which leaks at 15 kpa at the ripstop cross-overs would probably sustain 40+ kpa if it had been a plain weave. The use of 'ripstop' is seriously degrading the pressure ratings.

But it gets worse. Where do you think the coating on the fabric will preferentially abrade in the field? Yep, over those same bulging ripstop threads. Rather than adding value to the gear, the ripstop feature actually degrades the gear.

Do we get any benefit from the ripstop feature? It's meant to add value by preventing rips after all. Well, my silnylon tent was taking 100+ kph winds with no trouble at all. I don't think the loads on the fabric were getting anywhere near 10% of its strength. So under any realistic conditions the ripstop feature is completely unnecessary.

Let's imagine you did reach a situation where the fabric started to rip but the rip was (hopefully) stopped by the ripstop threads. Yeah, right. If things have gone that pear-shaped, a few fat ripstop threads are NOT going to save your bacon. Zero value.

So why does everyone use ripstop fabric? Two reasons, and the first is marketing pressure: 'ripstop' sounds technical. The second reason is that you can't easily buy coated plain weave fabric – see first reason.

Cheers

> Does anyone know of a nylon fabric with a PU coating on one side and a silicone coating on the other side?
Yes, this is available from a number of suppliers in Asia. Good quality stuff too, down to 40 gsm. (I have samples via intermediaries.)

However, the tent/gear manufacturers who have sources won't say where they get it from, and the Asian sources will only sell in rolls of 1,000 yds (or similar).

Drives us up the wall!

Cheers

I agree with Roger on the plain weave. Ripstop's offer nothing but marketing value..

This comes close:

Skylite ripstop
Skylite Silicone Impregnated Ripstop is extremely lightweight, packable and waterproof. Use for tarps, clothing and tent flies

Use a wet wipe to clean. Gentle machine wash if necessary, hang to dry.
Content: Urethane/Silicone impregnated
Suggested needles: Microtex 70/10
Weight/sq yd: 1.1 oz before impregnation
Weight/sq yd: 1.4/5 -1.7 oz after impregnation

I agree with Roger and Lawson – "rip stop" sounds cool but is just marketing hype.

I've seen some fabric that looks like it's "fake" rip stop. You can see a grid pattern on it but you can't feel any pattern. Maybe if the marketing people want to do that, it's okay.

I have used a 70D Nylon Ripstop with Silicone/PU blend coating before and it works great for tent floors. It has a finish weigh around 2.3oz which is on the heavier side of town but its much more durable then a 30D silnylon and its hydrostatic head is probably close 10 times more so you never have to worry about a leaky floor.

> Skylite ripstop
> Skylite Silicone Impregnated Ripstop is extremely lightweight, packable and waterproof.
> Use for tarps, clothing and tent flies
> Use a wet wipe to clean. Gentle machine wash if necessary, hang to dry.
> Content: Urethane/Silicone impregnated <<<<<<<<<<<<<<<<<

I don't know what TheRainShed is up to here, but I do know that Skylitect seems to be a trademark used by Westmark, as is Ultrasil. Both Westmark fabrics are double-coated with silicone polymer. There is no PU involved.

Mind you, a silicone/PU fabric at or below 50 gsm would be VERY nice. Send any samples my way and I will test them!

Cheers

Roger,
Thanks for the clarification. Maybe you left the door open a little with the reference to the pourosity of the sil coating. Couldn't that lead to leakage when the thin 30 denier nylon is stretched by the pressure on your tester?

On a more practical note, I will take you up on the offer to test The Rainshed stuff, if there is any left by tomorrow morning.

And don't they have fun confusing the heck out of us with indiscriminate use of terms like "ultrasil," and "skylite."

Jerry,
Have run across a number of 30 denier silnylons with slightly heavier coatings in the 1.5-1.6 oz/sq/yd range total for the fabric + coating.
Alas, the two most promising ones were Suter tested and fared worse than some the best quality 1.3-1.4 oz stuff I could find. One was purchased from Oware and was coated on both sides; the other from Thru-Hiker as a "prototype," and was coated on one side only, perhaps with floors in mind.
It's all well and good to talk about due diligence, but actually getting past go is another matter entirely.

About the recoating: It might work better to apply very think undiluted Permatex to spots that appear worn and/or are wetting out/leaking. I've found that the GE caulk, the SilNet and the Permatex all lose much of their adhesiveness when mixed with mineral spirits or stove fuel. No good for bonding patches at all, for example.

Eugene,
Thanks much for spotting and posting about the Rainshed fabric. Will try to order some tomorrow.

Stuart, ditto on the Extrem material. 80-90 gsm is a little on the heavy side, but if it refers to the material + coating, not just the material, it would still be lighter than the sil-coated 70 denier, 1.9 oz nylon. Definitely worth checking out.

> Couldn't that lead to leakage when the thin 30 denier nylon is stretched by the pressure on your tester?

Well, I am reporting what I see when I test the fabrics. I see the drops slowly forming either on the rip stop threads or, very often, first at the ripstop thread cross-overs.

It has been my experience that very few drops form in the plain weave areas in between, at least until I get to well over 40 kPa.

cheers

Thank you, Roger.

Has there been a thread about where to find 30 denier silcoated taffetas?
Based on your tests, that might actually provide what John, the OP, and many others I think, have been looking for.

Samuel

80 / 90gsm is the coated weight. I am using the 90gsm PU coated nylon for a bathtub floor and can confirm that the quoted weight is accurate. Is it heavy? My floor uses 2.2m2 of fabric and weighs 200g. Using 50gsm silnylon instead would only save 90g and be a lot less waterproof/robust.

Roger,
About the "Skylite", "Urethane/Silicone impregnated" taupe material sold by The Rain Shed: I believe that some "Skylite" material you tested from Westmark (not furnished by me) was also taupe in color, but as you advised, contained no polyurethane in the coating.

A swatch of The Rain Shed material will go out to you shortly, and I hope you can advise whether they are the same.

Stuart,
Thank you for the additional information.
My comment earlier about 80-90 gsm fabrics from Extrem Textiles being lighter than the silicone coated 1.9 oz nylon from Seattle Fabrics was wrong. They are around the same weight, 2.35-2.65 oz/sq/yd, the weight of the SF fabric falling in between the two from ET. The one you are using should add around 3-4 oz more than 1.4 oz silnylon to the weight of a solo-sized floor (22-30 sq. ft., including bathtub sidewalls). Guess it is a matter of priorities. For me, losing close to a quarter pound is the higher priority, if the silnylon resists water penetration up to 15 kPa, or at least 1500mm HH. Also, since you have had good results with a floor of the PU coated heavier nylon, and I with black silnylon from Thru-Hiker, no doubt that influences our choices. Don't doubt your floor is more waterproof/robust.