Bushwalk Australia

This thread on Backpacking Light has some very interesting conclusions about silnylon ...

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=44977&startat=20

Apparently the stuff available from Thru-hiker is light years ahead of most other products available to MYOGers. I knew that silnylon did not have a great waterproofness rating but it is good to see improvements are happening. It would be interesting to know what the cottage industries are using, e.g. if tarptent are using the 'normal' silnylon and don't have problems with it, then maybe it is worth worrying about for tents. Good to have a better product for compression sacks and floors etc though ...

The 'shield' silnylon from thru-hiker should be more durable too? Well in terms of maintaining good hydrostatic head for longer.

Looks good doesn't it. I think you are correct, worth the concern for compression (like drybags, bivy sack floors etc) I wouldn't be overly concerned for shelters. There was some discussion about misting, I noticed this in an earlier golite tent. I guess people baulk at the thought of Anything getting through the tent shell but it happens, its not a big deal. Seen it on Hillebergs Kerlon fabrics also under the right conditions, likely just not noticed with an inner tent situation. There was some testing on hydrostatic head of Cuben and a note that the C08 type had a dismal HH. Even down around 400mm it still is effective as a tent shell. Even so, given the choice, the Thruhiker Shield Nylon is not overly expensive, doesn't seem much point in not choosing it for its higher HH?. May stop those few beads of water on the inside or the misting under extreme conditions?

The thru-hiker site lists the finished weight as: 1.4 oz/yd2 (47 g/m2). Most other sil-nylon I've seen has a finished weight of 1.3 oz/yd2, could it be that they just used more silicone?

Probably, i see on BPL they noted a fairly loose weave when they looked at the Shield in micrographs. Not a lot left besides silicone? More/Different type/Method of fixing?
I did buy some regular Si Nylon from thruhiker, wouldn't be too concerned being assured of good quality either way.

if tarptent are using the 'normal' silnylon and don't have problems with it...
Some have had, however keep this in mind.
As far as I know most of the US silnylon comes from the same source.
There are two types. The lighter (and more expensive) that TT uses for the fly and the slightly heavier (it has some PU mixed in with the silicone) type that we use for the floor and others use for the fly as well as the floors.
The second type is also "renamed" by some and, contrary to the TT tests, appears to have a much higher whaterhead rating.
The difference from the lab tests to the ones we do I think has to do with the way lab test push the water against the fabric as opposed to the way rain actually falls on the canopy.
Possibly the surface tension changes by having the whole of the fabric under pressure.
Also do keep in mind that in my (and others...) experience all too often people confuse mist from with mist through the fabric.
I had the opportunity to test that again last week during three days of heavy rain.
The first evening (I was inside at 7PM) I started to get some regular sprays but after wiping the top of my Contrail a couple of times with a Chux, the rain continued but the mist stopped.
My mate in his Moment didn't bother.
Both tents were up for two days and two night and it rained most of the time.
Here is some vision :
http://www.youtube.com/user/francodario ... 1PNJTJwdGg
When you see me getting out of the tent in the morning the rain had eased off a bit but you should get an idea from the river level of how much rain we had.
Franco

Franco wrote:Also do keep in mind that in my (and others...) experience all too often people confuse mist from with mist through the fabric.

Another confounding effect is that due to an incompletely sealed seam.

If the Shield silnylon is better simply because there is an extra 0.1 ounce of silicone I can't help but wonder what the hydrostatic head would be for "standard" 1.3 oz/sq. yd. silnylon that had ~0.1 oz/sq. yd. of silicone painted onto it. Surely someone has tried this? I know that Jim Wood tested standard silnylon intended for a tent floor before and after applying silicone at about 0.75 oz/sq. yd.

Orion
I did some experiments by spraying the TT silnylon and using my 3 m tube to test that.
It seemed to take the waterhead from 1200mm or so to over 1500mm after a couple of light sprays.
Again I think that in actual use the result's will change a bit.
Here is a Double Rainbow I did for a customer :
http://www.youtube.com/user/francodario ... BnkGIz9cco
truoble is that I did not test that one before the application so I am not sure of how much better if any it was after.
Note that there is a lot more water coming out of the hose than under most thunderstorm. With the same force (and approximately hitting the same area) I filled a bucket in about 1 minute.
I have never seen 1 foot of rain in a minute in reality...
BTW, the full can has about 50g of silicone, the rest is the propellant.
Franco

Franco wrote:Also do keep in mind that in my (and others...) experience all too often people confuse mist from with mist through the fabric.

I believe condensation can also create a similar situation and agree, they would difficult to tell apart in a small enclosed shelter. Pretty hard to mistake under a 5m tarp pitched high with no condensation prior to rain though..

Yes , I was amused by the comments at BPL that mist never happens with the brand you mentioned (the H type...) but even more so recently reading that the same guy who objected to the thought of that happening had recently a very wet night under another shelter (from condensation ). Good thing that he wasn't using one of his TTs at the time...
Franco

Franco wrote:I did some experiments by spraying the TT silnylon and using my 3 m tube to test that.
It seemed to take the waterhead from 1200mm or so to over 1500mm after a couple of light sprays....
...BTW, the full can has about 50g of silicone, the rest is the propellant.

In the video you spray a small area for a few seconds.
Can you estimate how much silicone per unit area you added?

I already had done that tent. The "spraying" you see in the video is just to give an idea of how is done.
I used about 3/4 of the can on that tent, so about 40g.
You would normally use all of it in two sessions. Spray wait for 30 min or so than spray again.
If you are sensitive to chemicals, wear a mask.
Franco

40g over the whole tarp, which is probably something like 5-6 square yards of material. That works out to around 0.2 to 0.3 oz/sq. yd. I guess it isn't too surprising that spraying some silicone wouldn't be as effective as what they can do at the factory with additional coating.

But I can get cosmetic seconds of standard silnylon at half the price of Shield. I think I can put up with a little misting.

Or you can just make your own silnylon:

Orion ,
That works out to around 0.2 to 0.3 oz/sq. yd

The lighter silnylon is usually quoted as 1.1oz per sq yard uncoated. Coated is between 1.3 and 1.4 so even just spraying doubles the coating.
Michael ,
Atsko in the US as a liquid version of their spray but it comes in a gallon size.
Not sure but I think that it is just highly diluted silicone and some mineral spirit of some sort.
BTW, I haven't bothered spraying/painting any of the shelters I use because they work for me as they are.
Franco

Franco wrote:The lighter silnylon is usually quoted as 1.1oz per sq yard uncoated. Coated is between 1.3 and 1.4 so even just spraying doubles the coating.

Yes, it doubles the weight of the coating but apparently not the effectiveness. I wonder if part of this is due to an inability to apply it evenly with a spray can?

Franco wrote:BTW, I haven't bothered spraying/painting any of the shelters I use because they work for me as they are.

That's good to know. I usually don't encounter epic rain. On visits to Tasmania I take a shelter made from better silnylon (Hilleberg's fabric).

I've never treated a fly but I have diluted silicone in mineral spirits and painted floors of shelters, primarily to eliminate the slipperiness. Now I'm curious to try the spray can approach instead since it should be possible to add less weight to the fabric that way.

Have you noticed if the spray takes away the slippery feel of the silnylon?

I have a spray can of "silicone lubricant" that contains silicone, petroleum distillates, mineral oil, and propellant. That sounds like what I've been painting tent floors with. I use this spray mostly to lubricate climbing camming devices, but now I'll have to try it out on some silnylon and see how it behaves.

have a spray can of "silicone lubricant"
DO NOT use that, different stuff from what I was talking about.
BTW , anyone reading this, please keep in mind that same is not similar.
For example when I talk about silicone, I mean 100% silicone NOT the cheap stuff that is used for bathrooms and the like.
It must say 100% silicone on the label if not you will have problems later on . (peeling, degradation)


Franco

I think you should be very careful using something called a lubricant to waterproof sil-nylon - it has a very different end use and one assumes that it will remain slippery and somewhat liquid. Generally silicon waterproofing/sealing sprays tend to sit on the surface of the fabric and wear off quite quickly. The paint on silicon in solvent will fill any voids somewhat better and last longer although there are reports of them peeling off relatively quickly like an old suntan.

My understanding from reading various threads at Backpacking Light is that the most waterproof of the sil-nylons actually have some pu in the mix or a pu face and a sil face.

You guys are probably right that the formulation of a silicone lubricant won't give the desired "rubbery" results if sprayed on silnylon fabric. I was curious and thought I'd try it out on a small test swatch just to see.

Franco wrote:I mean 100% silicone NOT the cheap stuff that is used for bathrooms and the like

What's "100% Silicone" mean?

I have several silicone sealants that say "100% Silicone" on the label and they are all for different purposes, including use in the bathroom. In fact, our glass shower enclosure is held together and attached to the tile with just such a product. The base of the shower is caulked with a "100% Silicone" product designed specifically for kitchen and bath. It contains an ingredient to resist mildew. According to its MSDS it also contains petroleum distillates. So what exactly does that 100% mean? If I mix a 100% silicone sealant with mineral spirits is it still 100% silicone?

Silicone is not one thing but a class of polymers. The details of the formulation are important otherwise there would just be one 100% silicone product instead of dozens.

Earlier this year I tried out a couple of 100% silicone sealants (one made by McNett and one made by DAP) to see if there was any difference between how well they bonded silnylon fabric together. They felt different, they smelled different, and one of them formed a much stronger bond. Both 100% silicone but quite different.

Mark F wrote:My understanding from reading various threads at Backpacking Light is that the most waterproof of the sil-nylons actually have some pu in the mix or a pu face and a sil face.

That's interesting. I have a small amount of 70d (2.6 oz/sq yd) silnylon that has a different feel to it and doesn't easily stick together with silicone adhesive. I've been wondering if there might be some polyurethane in it.

What does 100% silicone mean ?
In the context it means that is not mixed (apart from minor additives) with other stuff as it is the typical silicone you buy at Bunnings.
So for example, I use both the GE2 as well as the Selleys roof and gutter stuff as I have occasionally used the McNett one. They are all slightly different but all work for me. But I have also tried other Selleys silicone (not labelled 100% silicone...) and that stuff peels off after a short time.

My understanding from reading various threads at Backpacking Light is that the most waterproof of the sil-nylons actually have some pu in the mix or a pu face and a sil face.
The two main types of silnylon made and available in the US are the 1.1oz (pre coating) that TT uses for the fly and the slightly heavier (and curiously cheaper) version that we use for the floors.
The second type has some PU mixed in with the silicone prior to application.
That is the one that some attach magical names to it...
There is also the type sold as silnylon with PU undercoat. This does usually have a higher waterhead but it has less stretch, less tensile strength and can perish with age or humidity (IE when stored wet)
And for those reasons TT chooses not to use it but do keep in mind that it is in fact cheaper, to us, than the stuff we use.
In the end you go for the one that appeals to you most.
BTW, I think that the cost has to do more with the production volume than the actual cost , per yard, of production.
Franco

Franco, do you have any idea if the 70d 2.3 oz/sq yd "silicone-impregnated ripstop nylon" that bearpawwd.com sells has any PU in it?

http://bearpawwd.com/fabrics_misc/fabrics_misc.html#70D

By the way, I sprayed a couple of test swatches of standard silnylon with my can of silicone lubricant. I sprayed one swatch lightly and the other one I really soaked it good. After allowing them to fully dry it is as if nothing happened to either one, at least not that I can see, feel, or smell. I guess lubricating silnylon is kind of a silly idea!

Orion
Don't know about the 70d stuff.
It is described as being silicone coated both sides and impregnated but it could, as it is with our floors, have some PU in the silicone mix.
Rubbing my fingers on the grey and the black silnylon I can feel the black to be just a touch rubbery whilst the grey is very slippery so I guess you could maybe tell by that.
But if the silicone is thick enough it will also feel rubbery , so not sure about that.
BTW, yesterday I glued a piece of mesh using silicone, you can't do that with a lubricant...
Franco