“Misting” Silnylon!

[Lynn Tramper]

Miguel, I think calling your comments "hysterical" was uncalled for. However, I also think that expecting a UL single-skin tent to withstand anything that Japan (or insert extreme weather conditions here….) can throw at it is also unwarranted. It is good to let other members know the limitations of UL gear, but that's all it really is. You've found the limitations of your shelter. I have survived gale force winds plus torrential downpour (side-pour acvtually as the wind driven torrent was almost horizontal), and I believe the design of the Double Rainbow was improved as a result of my feedback to Henry after that trip. However, I was not expecting a gale/downpour, and if I had known things were going to be that bad I would have taken a different tent (actually I would have stayed home!). The fact that the tent and I survived the storm is a testament to the tent IMHO. So UL often means compromising "bombproof" and we should all know that by now. Silnylon is not 100% waterproof. That is the take-home message I hope everyone takes from your experience.

[Roger Caffin]

Hi Miguel

Yes, it seems to be lasting quite well. But no, I don't use it these days: it's a bit too short. Yes, it is made of long staple Egyptian cotton, called 'Japara' and woven on one special loom in Bradford UK. The loom eventually broke, about the time synthetics moved in, and the owners never repaired it. End of Japara.

'Mineral spirits' is a general name for volatile solvents, as far as I can see. I haven't been able to find a hard definition, even from the vendors. But I would be interested in what others have found.

cheers

[Adrian B]

>Personally, I fail to see what all the hullabaloo is about a little misting or condensation.

Well, if it's bad, a single night of it on an unprotected down bag will make it quite soggy indeed. I think that's pretty serious.

A few weeks ago I woke after a night of constant heavy rain (in my Lunar Solo E) to a very wet down bag, from what looked like this exact problem. Temperature about 3-4 degrees C in the tent. The next night it was dry, but below freezing (winter here in s. hemisphere), so getting into a collapsed down bag to spend a cold night wasn't that nice.

This wasn't a slow degradation of loft over a several day trip – this was getting out of the car with a warm+dry bag straight into the tent, and by the morning stuffing a very wet bag.

Interestingly I've often camped in similar or heavier amounts of rain in warmer temperatures (10 C +?) and I haven't noticed anywhere near as much of a misting problem – before this trip I would have read this thread and been similarly dismissive as some. So it was an unpleasant surprise, I'm glad I had what I thought was an excessive amount gear for the temperatures.

Anyway, I'm looking forward to finding out if a cuben tarp+bivy is wetter or dryer in this situation. Failing that, next winter I'll try a lightweight double wall tent. (And hopefully using a bivy in the Lunar will see me out for this winter).

(Edit: it's hard however to pin down exactly where the moisture comes from in this situation – especially when I was soundly asleep ;) could have been heavy fog/cloud directly condensing on the bag, in which case tent material is somewhat irrelevant)

[Lynn Tramper]

Yes, I often had problems with a damp bag in the Lunar Solo, but in my case I knew for sure it was condensation. That's why I always use a bivy bag now. The Lunar Solo seems particulalry bad in this respect.

You would do well to find out 100% for sure if the problem was condensation versus misting as cuben shelters are just as prone to condensation as any other single skin non-breathable shelters of similar design. In other words, a silnylon Refuge would be just as prone to condensation as a cuben Rrefuge-X…

[Franco Darioli]

Interestingly I've often camped in similar or heavier amounts of rain in warmer temperatures (10 C +?) and I haven't noticed ..
Interesting comment.
The other day I set up my Rainbow to do a quick "pressure test". Air temperature about 12c but on full sun. I put my hose with a "jet" spout about 15cm away from the fly and let it rip for 2 minutes. (8 liters from a 4 mm opening, if you can work that out …) . Not even a hint of mist inside, just a "dent" in the silnylon.
Thinking about when I am sure I had "penetration" it would have been between 3 to 6 c, we had sleet in the morning. On another occasion that I detected "penetration" it was also not too far from freezing. So it is my opinion that as the silnylon stretches it also becomes correspondingly less waterproof. This also means that you need several factors (low temperature, fat raindrops and intensity) to make it happen,and that is why many doubt that it happens at all.
Franco

[Roger Caffin]

Hi Franco

So a pressure test in the middle of the day showed that the silnylon did not leak, right?

But you got some moisture on the inside at night in cold weather. Under these conditions (at night) it is normal for the tent fabric to get *colder* than the surrounding air. This means it will attract condensation, on the inside as well as on the outside. Of course, a little cold rain will help cool the fabric down even more, below the dew temperature.

No, the silnylon does not get less waterproof with cold. But it will attract condensation when it gets cold.

Cheers

[Miguel Arboleda]

But you got some moisture on the inside at night in cold weather. Under these conditions (at night) it is normal for the tent fabric to get *colder* than the surrounding air. This means it will attract condensation, on the inside as well as on the outside. Of course, a little cold rain will help cool the fabric down even more, below the dew temperature.

This comment made me very curious about effect of a material's "heat sink" value on the tendency to attract condensation. Will a material that gets colder faster than another material condense faster? For instance I get much colder in my Paramo jacket when it is wet than I ever did in my earlier Gore-tex jackets, even though the Paramo jacket is thicker. I think this has to do with the cold "feel", the heat sink effect, of the Paramo's outer shell. It's the same as when you stand in a room with metal flooring and one with wooden flooring and they both have the same temperature air. The metal room, because it is a heat sink, feels much colder than the wooden room. You can place your hand on the metal floor and feel the coldness of the material. Wood usually feels much warmer.

Does this work on fabrics, too? Would a fabric with a higher R-value not condense as easily and therefore stay drier longer?

[EndoftheTrail]

"Would a fabric with a higher R-value not condense as easily and therefore stay drier longer?"

Interesting question, Miguel, and my reaction is to say "yes". Say you lay two different fabrics on the ground. Both start at a warmer temperature from being exposed to the day. As night falls and as the ground cools… the fabric with lower R-value (maybe looking at it as more conducive) will cool down sooner — and if condensation were to form, would probably be coated with a wet film sooner as well. But as night progresses, without any heat source, the higher R-value fabric will eventually accumulate condensation as well.

[Roger Caffin]

> Would a fabric with a higher R-value not condense [gather condensation] as easily and therefore stay drier longer?

Um …. I am not sure. The question may be a little too vague anyhow.

The reason a tent fabric gets colder than the ambient air at night has to do with the temperature of the night sky – which can be as low as -60 C (from memory). Here we are talking about radiation effects. Is this relevant to a fabric with a significant R-value? Maybe not.

Further cooling of a tent fly can happen if the fly is wet and there is some wind. Evaporation cooling then happens, from the surface. I am not sure whether the R-value is relevant, unless you have a fabric which is so thick that the inside surface will be different from the outside.

> I get much colder in my Paramo jacket when it is wet than I ever did in my earlier Gore-tex jackets, even though the Paramo jacket is thicker.
Interesting. Once again, I am guessing here. Maybe the way the Paramo lets the water vapour through, while the Gore-Tex acts almost like a VBL, has an effect on your evaporative cooling as well. When we went over some snowy cols in France wearing a Taslan shirt and a silnylon poncho (aka VBL), we were warm as long as we kept moving. Take the poncho off and we could sure feel the wind-chill!

2c

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