Tarp/tent fabric and water resistance?

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jameso
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Tarp/tent fabric and water resistance?

Post by jameso »

How water resistant should I expect 30D silnylon to be? I read it was 2000-3000 WP rated and if that was a jacket I'd expect it to be quite water resistant but wet through after a while particularly with wind-blown rain.
30D S-N Seems a common spec for tarps and tarp tents though. I've experienced water pushing through a tarp after a few hours of steady but not torrential or stormy rain and it's partly why I often don't bother with tarps - if they won't keep me dry all night I may as well either keep moving when it's raining and find some shelter to sleep under, and travel lighter.

I do take a tarp sometimes as wind or shower shelter. Is that what others use them for, better-than-nothings?
Can I use silicone+solvent painted on or soaked in to increase water proofing?
I really need a dyneema tarp tent don't I..
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Chicken Legs
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Re: Tarp/tent fabric and water resistance?

Post by Chicken Legs »

This is one of the reasons I like my ZPacks Hexamid, its made of Dyneema Composite Fabric which doesn't wet out like silnylon but is still light.
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whitestone
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Re: Tarp/tent fabric and water resistance?

Post by whitestone »

I've not had water come through our tarps (Alpkit 3.5 & 7). Our first bikepacking trip was on the WHW on the weekend that the Fort William World Cup was cancelled because of the weather - biblical! Strung the 3.5 up in the woods above Kinlochleven and was dry all night.

Is it actually "coming through" or is it condensation on the underside being shook off by the rain hitting the material?
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ScotRoutes
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Re: Tarp/tent fabric and water resistance?

Post by ScotRoutes »

I don't think I've ever had rain coming through a SilNylon tarp, so I've always been happy to consider it as waterproof enough to spend a wet, windy night under. However, I'm also using DCF now.
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Bearbonesnorm
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Re: Tarp/tent fabric and water resistance?

Post by Bearbonesnorm »

A HH of 1500 is considered to be waterproof. However, if the coating is worn or damaged, any rating goes out of the window.

I think what you're describing is 'misting'. I know it can happen when heavy droplets fall from trees, buildings, etc.
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jameso
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Re: Tarp/tent fabric and water resistance?

Post by jameso »

Chicken Legs wrote: Thu Jun 17, 2021 7:51 pm This is one of the reasons I like my ZPacks Hexamid, its made of Dyneema Composite Fabric which doesn't wet out like silnylon but is still light.
Small though aren't they... maybe you should upgrade to something bigger maybe, time to sell that one on... ; )
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Shewie
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Re: Tarp/tent fabric and water resistance?

Post by Shewie »

I've had spray come through once the tarp is saturated and the rain drops are heavy enough, but that's on a big Warbonnet Superfly hammock tarp in quite a flattish pitch. It's never really been a concern though, not enough to wet any bedding out. I've got a video clip of it somewhere, really visible at night with a headtorch on. I even wiped out the inside of the tarp with a microfibre cloth once to dry it out and rule out condensation.

Silpoly apparently absorbs less moisture than silnylon so might be a cheaper alternative to DCF, I've not owned anything in silpoly yet but I'm a few weeks into a tarp order with gramxpert so I'll see what that's about.

I use a splashproof bivvy with most single skin shelters when I'm hiking, on bike trips at lower levels I've come to the conclusion it's easier to just use a waterproof bivvy and small tarp and put up with a bit of misery sometimes.
jameso
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Re: Tarp/tent fabric and water resistance?

Post by jameso »

Bearbonesnorm wrote: Thu Jun 17, 2021 8:06 pm A HH of 1500 is considered to be waterproof. However, if the coating is worn or damaged, any rating goes out of the window.

I think what you're describing is 'misting'. I know it can happen when heavy droplets fall from trees, buildings, etc.
You could be right, I think that night I was pitched under / edge of tree cover as added shelter. Seems it backfired :grin:
It was that sort of sustained rain and no wind where drops seemed to be pushing the water through once wetted out. The coating isn't worn, it's a relatively little-used tarp. Not sure it actually is coated, just straight silnylon maybe? Doesn't look any different each side, same as other tarps I have. Might pitch it in the garden next time it rains (without me under it o/c) as a test to get my faith in it back.

Is it actually "coming through" or is it condensation on the underside being shook off by the rain hitting the material?
- possibly, I was awake enough to watch and see why I was getting unexpectedly wet and it seemed that drops landing were pushing through - they can't have been in reality so I assumed it was holding water / wetted. Condensation could be it as it was a more enclosed pitch.
I've had spray come through once the tarp is saturated and the rain drops are heavy enough, ... I've got a video clip of it somewhere, really visible at night with a headtorch on. I even wiped out the inside of the tarp with a microfibre cloth once to dry it out and rule out condensation.
- sounds very similar to what I saw.
jameso
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Re: Tarp/tent fabric and water resistance?

Post by jameso »

I don't think I've ever had rain coming through a SilNylon tarp, so I've always been happy to consider it as waterproof enough to spend a wet, windy night under.

Reassuring as I expect you'll be out in bad weather more often than I am, at least under a tarp. I've just got into the habit of using found shelter in the rain on so many trips now but I want to get back to using something <400g and not thinking I'll be wet by the morning.
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Bearbonesnorm
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Re: Tarp/tent fabric and water resistance?

Post by Bearbonesnorm »

just straight silnylon maybe?
Silnylon is silicone coated nylon ... the clue's in the name :wink:
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Bearlegged
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Re: Tarp/tent fabric and water resistance?

Post by Bearlegged »

Wild conjecture here, but is the comparison with waterproof jackets much help? I feel like the contact with the inside of the coat (which you wouldn't have with the tarp) contributes to the water coming through once the fabric is wetted out.
jameso
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Re: Tarp/tent fabric and water resistance?

Post by jameso »

Bearbonesnorm wrote: Thu Jun 17, 2021 8:36 pm
just straight silnylon maybe?
Silnylon is silicone coated nylon ... the clue's in the name :wink:
Ah ok : ) I get the name but thought it was siliconed nylon thread and the coating was PU, or you could get PU coated SN?
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Re: Tarp/tent fabric and water resistance?

Post by jameso »

is the comparison with waterproof jackets much help?
Not sure, I have had lower-rated WPs and Windstopper Active shell jackets wetting through seemingly faster in windier conditions. The wind can add to the pressure the water hits the jacket at and the WP rating is based on pressure.
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Bearbonesnorm
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Re: Tarp/tent fabric and water resistance?

Post by Bearbonesnorm »

Ah ok : ) I get the name but thought it was siliconed nylon thread and the coating was PU, or you could get PU coated SN?
You can get PU coated nylon. Also perhaps worth noting that some materials are coated on both sides and others only on one.
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Dean
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Re: Tarp/tent fabric and water resistance?

Post by Dean »

jameso wrote: Thu Jun 17, 2021 8:44 pm
is the comparison with waterproof jackets much help?
Not sure, I have had lower-rated WPs and Windstopper Active shell jackets wetting through seemingly faster in windier conditions. The wind can add to the pressure the water hits the jacket at and the WP rating is based on pressure.
When sitting on a wet surface with 5000mm waterproof trousers your body weight alone will force water through the fabric (same for kneeling down on wet ground to tie shoelaces or wearing a 8kg rucksack)

Umbrellas have a rating of about 700mm, so not legally waterproof, but as the material is taut the water will run off. A tarp pitch with a low angle/not taut enough will not allow water to run off quick enough so it will build up.
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Alpinum
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Re: Tarp/tent fabric and water resistance?

Post by Alpinum »

jameso wrote: Thu Jun 17, 2021 7:35 pm How water resistant should I expect 30D silnylon
Waterproofing comes from the silicone treatment, not from the thickness of the thread, which the D in 30D stands for (Denier).
jameso wrote: Thu Jun 17, 2021 8:40 pm or you could get PU coated SN
Some brands use Nylon coated with PU one side and silicone on the other. Mostly US tents, due to fire safety regulations.
Such fabrics will still loose some tension when wetted.

Silpoly (polyester) holds tension better than Silnylon when wet.

And yes, DCF fabrics are completely bomb proof in strong rain and winds, tue to near complete lack of elasticity under outdoor use.
Not so bomb proof in handling though and packsize is comparable to mid-light weight silnylon.
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Alpinum
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Re: Tarp/tent fabric and water resistance?

Post by Alpinum »

And for this talk about silnylon not being capable to hold water back:

If the fabric was rather new, it must have had a badly made coating.
Happens. I've came across one new shelter which had this issue.

Also after lots of use, the coating eventually breaks down/erodes, rendering the shelter not so waterproof anymore.

Good news is
you can easily re-coat any silnylon fabric yourself.

There are a couple of threads on this forum about reproofing/re-coating silnylon.

Our most used shelter's colour has faded heavily from an intense gold-yellow to a sandy and weak yellow. Many long trips, including some weeks in an area where the most intense UV rays on Earth have been measured... It already had it's re-coating, a new zipper and new tie out points. Sometimes, after a couple of hundred nights it's time to say good bye to your shelter.
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