Cuben Fiber vs. Sil Nylon water absorption Test Results

[colorado_rob]

Another thread "single vs. double walled tents" where the benefits of cuben (CF) vs. sil-nylon (SN) were discussed prompted me to run a test of water absorption of the two materials, and here are the results.

I used a zpacks 0.51 CF Solo+ tent, a zpacks 0.74 CF duplex and a Big Agnes SN Copper Spur 2 tent for the test, along with a piece of Tyvek (one of my Solo+ floors) and a piece of Polycryo (the other, lighter solo+ floor).

The solo+ is 3.5 years old, and used at least 100 nights, probably more. The duplex is much newer, bought this year, used about 50 nights (out of roughly 65 nights backpacking this year). The Copper Spur is 2 years old, used a couple dozen nights. It was our go-to “couples” tent before we finally sprung the 6-bills for the shiny new zpacks duplex.

I carefully weighed everything bone dry first. Then I soaked the tents and solo+ floor sheets with a hose. I tried to NOT soak the bug netting attached to the tents, reasoning that those would remain fairly dry even after soaking rains. I did soak the floors on the outside. I shook everything off for a couple minutes each, simulating how much time I would typically shake off water in the morning at camp. Even more shaking would remove some more water, but with diminishing returns. I tried to spend an equal amount of time shaking all pieces, but didn’t actually time this. I carefully weighed everything again.

Then I wiped everything down with a chamois cloth, wringing the cloth out frequently. I tried to spend an equal amount of time wiping/wringing all pieces, but didn’t actually time this either. 2-3 minutes per piece.

Here are the weights for the tents:

Zpacks 0.51 CF solo+ tent:
Bone dry, 13.3 ounces
soaked/shaken, 21.8 ounces (8.5 ounces of water left)
Wiped w/ chamois, 19.0 ounces (5.7 ounces of water left)

Zpacks 0.74 CF duplex
Bone dry, 22.4 ounces
soaked/shaken, 38.0 ounces (15.6 ounces of water left)
Wiped w/ chamois, 29.0 ounces (6.6 ounces of water left)

Copper Spur 2 Sil-Nylon
Bone dry, 33.6 ounces (total, fly + body, but not including poles, of course)
soaked/shaken, 65.0 ounces (31.4 ounces of water left)
Wiped w/ chamois, 50.0 ounces (16.4 ounces of water left)

Discussion: I was surprised how much water the CF tents still retained after shaking off, about 8 and 16 ounces respectively for the two tents, but then I weighed the sil-nylon tent and found almost 2 pounds of water left after a minute or two of shaking. So these results were a bit mixed; I had thought I could get almost all the water off the CF by just shaking, but then again, the situation with the sil-nylon tent was about twice as bad.

After using the chamois, all got a lot better, I was able to get the CF tents down to 5.7 and 7.6 ounces of leftover water, and the sil-nylon tent down to just about a pound of excess water (wiping with chamois removed a full pound of water)

So one conclusion is that wiping with a chamois helps a lot, especially with a sil-nylon tent (gets another pound of water off), but still a bit with a CF tent (another 6 ounces or so). So carry and use a chamois! Wipe, wring it out, and hang on pack and it will be dry (and back down to a couple ounces of weight) in no time.

For the two types of floors I have for my zpacks solo+ floor (the tent otherwise only has a bug screen floor), here are the numbers:

Tyvek floor
Bone dry, 4.7 ounces
soaked/shaken, 14.1 ounces (9.4 ounces of water left)
Wiped w/ chamois, 10.8 ounces (6.1 ounces of water left)

Polycryo floor
Bone dry, 1.8 ounces
soaked/shaken, 3.0 ounces (1.2 ounces of water left)
Wiped w/ chamois, 2.0 ounces (0.2 ounces of water left)

Discussion: as might be expected, the polycryo plastic sheet really doesn’t absorb water, though some residue does cling even after a wipe-down.

What really surprised me was the poor performance of the tyvek… a thorough shaking left 9.4 ounces of water, and even after a wipedown, 6.1 ounces. Even the dry weight of the tyvek compared to the polycryo is telling, it is much heavier. To be fair, the tyvek floor is a bit larger than the polycryo one, I made it larger to try to create more of a “bathtub floor” vs. the flatter polycryo in my solo+ tent.

That’s it! All weights are within 0.1 ounces or so, but the rest of this little experiment was not thoroughly controlled (by timing the shaking, wiping, etc). It does show to me though that Cuben Fiber tends to absorb less water than Sil-nylon, but still CF does “absorb” a bit, whatever “absorb” means (is it all water clinging to external rough areas or actually soaked into nylon or cuben fibers?)

These results don’t sway me one bit on which tent to carry. Most of the time I’ll carry the UL CF tents, but in very cold weather (fall, spring in the CO high country), we carry the Copper spur, because it sleeps definitely warmer and generally won’t get wet that time of year anyway.

[cmoulder]

Thanks much — that was a lot of work! :sun

Very nice data points that dispel some myths.

I agree... I'll still be carrying the Duplex for the most part.

[cmoulder]

hmmm... don't know how I double posted :confused:

[Kookork]

What an interesting and useful experiment. I loved it.
There are so many revealing and helpful numbers in your experiment. Good to know the numbers . Thank you

[sethd513]

[emoji1303]


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[Kookork]

Did you wash your hands between touching the different tents?:D

[Crossup]

Thanks for the very interesting work, for me a big take away is the value of wiping down...it has to have a significant affect on drying times. OH NO, another test idea :eek:

[Franco]

Years ago I did one comparing silnylon with polyester (two types) and Epic.
Polyester in my test retained more water than the rest. I did not wipe , just used the shake test.
Some have pointed out that with use CF starts to retain more moisture.

[Greenlight]

Another thread "single vs. double walled tents" where the benefits of cuben (CF) vs. sil-nylon (SN) were discussed prompted me to run a test of water absorption of the two materials, and here are the results.

If I can get my wife hiking with me (numerous reversible health problems and two partial knee replacements on top of that) more, to the point we're consistently overnighting or section hiking, I like the idea of the Duplex. Cuben is noisy for all its benefits, but I think we could make it work. When I'm solo hiking, I hang in a Hennessy hyperlite. I'm not against going to the ground. I have several comfortable mats and bags that pair well with them, and through Scouting as a youth and a 20 year military career, I've slept on just about everything from hugging the HMMWV mounted TOW gunner's turret all night, to pallets, to cave floors. A duplex with a Thermarest mat is still close enough to heavenly for me to get 40 winks.

Your experiment is top notch. It reaffirms that sometime in the middlin' future, I'll prolly be springing for a cuben tent.

Thanks!

[johnspenn]

I always thought that CF was entirely waterproof and would not absorb/retain moisture. Who knew? Great job on the testing!

[gbolt]

I wish I had been more scientific with my Tarp in Sleeves. However, I was surprise that dry weight of a Tarp vs the wet weight inside CF sleeve and stuff sac was over an eight ounce difference. I have now purchased Mesh Sleeves. Thanks for this data!

[saltysack]

Very interesting...I didn’t realize cf retained any water.....I’ve never bothered with wiping down just a few shakes then at a lunch break open up to dry....I’m still not likely to chamois as I’m to damn lazy...and in a hurry to get moving...


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[hipbone]

Really nice little experiment. I swear by a pack cover for this very reason...I'd think a backpack could take on at least 10 oz or more of water if it's not cuben. I carried a golite breeze (no hip belt) with no pack cover and when it got wet I could swear I felt the weight of the water on my back. Thanks for your efforts

[Cedar Tree]

The copper spur is not sil-nylon. BA uses a sil/pu fabric for their tents just like I use for the Packa. From the BA website:

Fly and floor are silicone treated proprietary patterned random rip-stop nylon with 1200mm waterproof polyurethane coating.

[johnspenn]

Really nice little experiment. I swear by a pack cover for this very reason...I'd think a backpack could take on at least 10 oz or more of water if it's not cuben. I carried a golite breeze (no hip belt) with no pack cover and when it got wet I could swear I felt the weight of the water on my back. Thanks for your efforts

I've always thought that too. Even if your pack is completely waterproof, as some claim that some of the Z-Packs and similar are, water will still collect in the nooks and crannies, adding weight. A pack cover can mitigate that.

[Kaptainkriz]

Very interesting and thanks for the test results. I was out with my Duplex last weekend in the rain and had to tear-down in the pouring rain. I noticed immediately when I rolled it up that it weighed much more than when I set it up. Shaking was a little useless because it was still raining. The tent was still dry inside, just wet outside and a whole lot heavier.

[cmoulder]

I've always thought that too. Even if your pack is completely waterproof, as some claim that some of the Z-Packs and similar are, water will still collect in the nooks and crannies, adding weight. A pack cover can mitigate that.

It can mitigate it a bit, perhaps.

The only places it can potentially 'collect' (assuming there are no holes in the pack!) are at the folds in the top where the material is rolled and secured with buckles in the center, and on items stored in the mesh stuff pocket. The water bottle pockets have drain holes. Otherwise, it won't retain very much more water via surface tension than a pack cover would.

Maybe we can get Rob to test this next. :D

However, this is why I prefer a poncho — it keeps both pack and suspension relatively dry... shoulder straps and hip belt will contain moisture from perspiration no matter what.

[colorado_rob]

The copper spur is not sil-nylon. BA uses a sil/pu fabric for their tents just like I use for the Packa. From the BA website:

Fly and floor are silicone treated proprietary patterned random rip-stop nylon with 1200mm waterproof polyurethane coating. Woops! My bad. I wonder f there are any significant differences in various coated nylon fabrics in terms of water absorption or retention?

I suppose I should change all my "sil-nylon" references to "coated nylon".

And for the record, I still don't think Cuben Fiber actually "absorbs" water, I just think the rough surface (as opposes to smoother polycryo plastic) holds water via surface tension. Given a few more minutes and enough dry absorbent towels, I would think one could thoroughly dry out a CF tent, but of course this is impractical in the field.

All I was trying to do here is to roughly quantify how much extra water weight you'll be inevitably carrying when you tent is soaked, and it appears CF is slightly better in terms of avoiding this, but still not perfect. Please take this little experiment with a big grain of salt.

One more little tidbit; I hung all these tents up to dry, of course, and as I have noticed on the trail, the CF fabrics dry very quickly. Yesterday in the bright Colorado sun, my zpacks tents dried practically instantly, with the coated-nylon Copper Spur taking a little more time.

Here's a pic of $1500 worth of tents hanging on ladders and my truck's mirror...

[camper10469]

why not just test same size tarps instead of including a tent? that way the comparrisons are strictly) f the material and not a tent rating.

i find it interesting how much water is retained by these particular tents though. ive got a coper spur ul 1 man which so far has held up very well in the rain up in the adks. i did notice i do get that micro spray after several hours but that may be condensation on the underside of the fly spraying when the wind shakes the tent.

[cmoulder]

Rob, I think your test protocols were excellent and representative of what people actually do on the trail.

[colorado_rob]

why not just test same size tarps instead of including a tent? that way the comparrisons are strictly) f the material and not a tent rating.
If you have said tarps, feel free! Lots of folks would be interested in the findings. FWIW, the two zpacks tents ARE essentially tarps, with sewn-in bug netting though, and therein lies the rub; during yesterday's testing, I tried to not wet down the netting, trying to simulate trail conditions where the netting would stay fairly dry. However, when I shook the tents off, the water flying off of the tent top or floor would tend to soak the netting, and it seemed like once the netting got wet, it held onto water like a sponge and could not be shaken off. the chamois wiping did remove the netting water easily though.

So it would be very beneficial for those pure-tarp (no sewn-in netting) owners to know if there is a significant difference in water retention of fabrics. Tarp users, even with bug netting could remove their bug netting before shaking off the tarp and could easily get better results.

[cmoulder]

why not just test same size tarps instead of including a tent? that way the comparrisons are strictly) f the material and not a tent rating.

i find it interesting how much water is retained by these particular tents though. ive got a coper spur ul 1 man which so far has held up very well in the rain up in the adks. i did notice i do get that micro spray after several hours but that may be condensation on the underside of the fly spraying when the wind shakes the tent.

I did test a tarp, which was the HMG Echo II .74 cuben (about 10.5 oz with guylines) and saw about a 40% weight increase (to about 14.7 oz) when the wet tarp was shaken out rather vigorously. I didn't wipe down with chamois, however.

These are not absolute tests for materials. For that you'd need straight-up, 4'x4' sheets of different materials to test, and a really good scale. Any modification to the material, such as seams or grosgrain loops or guy lines, would taint the results.

[nsherry61]

. . . I wonder f there are any significant differences in various coated nylon fabrics in terms of water absorption or retention?. . .
My understanding is that there is quite a bit of difference depending on the fabric (polyester vs. nylon) and depending on the coating and coating method.

[Franco]

Cordage, zips and seams can retain a lot of water and that could be a reason why in practice (a finished product as used on the field) may give different results from lab tests on just a piece of material.

[scrabbler]

Great info, thanks for taking the time that was a lot of work. One more question - weight of wet chamois after wringing out? (Since one would have to carry it as well).

[Franco]

Much lighter than chamois, less expensive and much faster to dry are the thick "disposable" kitchen cloths.
They last a few weeks of continuous use, longer if you are careful and work well from fully dry (chamois tends to want to be wet before it really absorbs)

[cmoulder]

Cordage, zips and seams can retain a lot of water and that could be a reason why in practice (a finished product as used on the field) may give different results from lab tests on just a piece of material.

This is why IMO Rob's test is far more useful than a lab test! :)

And a high level of accuracy is not needed anyway... so what if there's a +/-10% error? The important things we learned are that Cuben shelters are significantly heavier when wet than widely assumed and that sil/pu/nylon ones are a helluva lot heavier than that.

[colorado_rob]

This is why IMO Rob's test is far more useful than a lab test! :)

And a high level of accuracy is not needed anyway... so what if there's a +/-10% error? The important things we learned are that Cuben shelters are significantly heavier when wet than widely assumed and that sil/pu/nylon ones are a helluva lot heavier than that. Thanks for the kind words, CM, yeah, I was just trying to do a field-simulation thing.

The Chamois: I should have posted these numbers as well... we carry a "backpacking towel" that I was calling a "chamois" because that is what it is, I think. It is synthetic, but absorbs water well and dries fast. HEre are the numbers:

Bone dry, 0.9 ounces. It's an MSR brand, about 18x18 inches. Had it for years. I actually lost mine, so used my wife's. I need to replace mine! Handy little piece of gear, well worth the 0.9 ounce (dry) carry weight.

Soaking wet, it weighs close to 5 ounces, meaning that it will absorb about 4 ounces of water before wringing out. During the wipe-test, I wrung it out a couple times per item.

Wrung out, but still wet: 2.0 ounces, meaning you'll be carrying about an extra ounce of water when you use a towel like this to wipe down your tent. But it dries very quickly. I hand mine on the back of my pack tucked through the side compression cord. I'd guess that within an hour it is back close to its 1 ounce dry weight, assuming its not pouring rain.

[mentalfuzz]

Great article. Thank you


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[Malto]

I agree with your theory of surface water vs. absorption. As far as the wipedown, now you have a wet cloth that weighs extra with all the water weight. Not sure there's enough water on my mid to worry about it, it dries quickly.

[nsherry61]

Much lighter than chamois, less expensive and much faster to dry are the thick "disposable" kitchen cloths.
They last a few weeks of continuous use, longer if you are careful and work well from fully dry (chamois tends to want to be wet before it really absorbs)
+1 on these. I've had a box for years and love them. I think of them as sort of a bandanna weight disposable chamois. I find they absorb faster and more completely than my "camp towels", and they are way cheaper and lighter. I don't take camp towels backpacking (only camping), instead, I take a bandanna and one of those kitchen wipes. Use the kitchen wipe for messy crap and my bandanna for, well, all the not so messy bandanna stuff.

[scrabbler]

Thanks colorado_rob, you rock. Excellent info.

[Elaikases]

Great article. Thank you


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Exactly. Well done. Well done.

Also helps me feel better about using a polycro tarp to set my tent up under. Last time I did that and got rained on, the tent came away dry.

Just switched the tyvek foot print off for a polycro one as well.

This makes me happier with that decision.

[kestral]

Thank you so much for the research and post. My silnylon tarptent and tyvek ground sheet seemed to weigh a ton after a rainy night. The main reason why I like to use a shelter in the rain. Now I know it's not just my imagination!

Does polycro hold up well to abuse, like use as a ground sheet and to put down in shelters to protect my air blanket? Also, can it be sewn, heat bonded, taped to make an economical pack cover or chaps, rain skirt?

your research is making me rethink all my weather gear.

Also, you should contact zpacks with your post rain weight reviews, I think it would impact many people in justifying the big ticket duplex. ( maybe they can send you a freebie, you earned it)

to consider, I always put my tyvek through washing machine to get rid of annoying crinkles, this probably decreases water proof ness and increases moisture absorption and therefor weight.

I will consider bringing a polycro tarp to put over my tent if expecting heavy rain.

Have you tested any light cordage for water absorption?

thanks again for your research.

[JC13]

Actually considering making a polycro rain kilt to replace my tyvek one after this test.

[colorado_rob]

I'd be a little careful using Polycryo for much of anything except a ground/floor sheet. The stuff I've used is pretty fragile. As a floor in my zpacks solo+ tent, which has otherwise only a bug-screen floor, I got one piece of polycryo to last about half of an AT, with one or two little tape repairs, IIRC.

I also used it in shelters (kinda rare I slept in them) as modest protection and a dirt barrier for my sleeping pad. This is probably where I got those little tears.

Polycryo is kinda fragile; strong enough if you pull it in tension, but get a little nick and it will tear easily.

Might work for a rain kilt. Hard to say. Cheap enough to test!

Thanks Kestral! I doubt if zpacks is interested, but who knows. I think they would want a more rigorous test, or at least a repeated one with averaged results. I really am just trying to indicate a trend here.

[Slo-go'en]

With nothing better to do on a dreary, light rainy day, I set up my SMD Trekker up in the front yard and left it out in the rain for a couple of hours. The grass was wet, so I used my Tyvek ground cloth, which I always use anyway. I shook and toweled off as much water as possible before stuffing it back into the sack.

Initial weight - 25 oz. Towel - 2 oz.
Wet weight 32 oz. Towel - 4 oz.

Net gain 9 oz. 36% increase. No wonder we hate to carry a wet tent!

Now I hope it's a sunny day tomorrow so I can dry my tent!

[hipbone]

Only thing we need now is a sil-poly tarp tested [emoji16]

[poolskaterx]

Thanks for the info; nice to have our suspicions of extra weight confirmed.

[Crossup]

If anyone is going to try using Polycryo, keep in mind there is interior AND exterior rated material and its available from 0.75mil to 1.5mil. If you hem it with the right tape you only have to worry about punctures. If torn, immediately patch with tape. Lots of info for using it as a shelter over at Backpackinglight which is applicable for many other uses.


I'd be a little careful using Polycryo for much of anything except a ground/floor sheet. The stuff I've used is pretty fragile. As a floor in my zpacks solo+ tent, which has otherwise only a bug-screen floor, I got one piece of polycryo to last about half of an AT, with one or two little tape repairs, IIRC.

I also used it in shelters (kinda rare I slept in them) as modest protection and a dirt barrier for my sleeping pad. This is probably where I got those little tears.

Polycryo is kinda fragile; strong enough if you pull it in tension, but get a little nick and it will tear easily.

Might work for a rain kilt. Hard to say. Cheap enough to test!

Thanks Kestral! I doubt if zpacks is interested, but who knows. I think they would want a more rigorous test, or at least a repeated one with averaged results. I really am just trying to indicate a trend here.

[Starchild]

Water is effen heavy, and I have got on my soapbox on this in respect to water purification method (short answer, the method doesn't matter, the water you carry due to the method does). Same with rain soaked tents, and this proves that CF does a better job at not holding as much. Never did I expect it to be totally dry at packing, and did expect it to gain a significant amount of unwanted weight but never knew how much. I would like to know the results 'in the field' not only on a rainy night but a dew soaked morning what is the extra water weight, I believe it would be eye opening.

[rocketsocks]

I like and appreciate the testing you did, though I likely wouldn’t spend the extra money on cubin fiber.

[Starvin Marvin]

Rob, thanks for taking the initiative and posting the results. Very helpful info.

With my ground tarps, I usually wipe them down, but my hammock tarps I don't. Maybe I should.

[kestral]

In the past I have made a rain kilt and mult sized roll down and then Velcro type stuff sacks out of Renalds brand turkey roaster bags. I have reused these several times on short sections and they hold up well and weigh almost nothing. I have used one at home as a veggie bag just so I can abuse it, rewash, reuse, etc to see how it holds up. So far great.

I seal the sides with an impulse sealer and reinforce high tension areas with cut to fit bits of clear packing tape. This material seems to be very different then the stuff labeled polycro at craft store. Does anyone know the proper name for the oven bag film and / or if it can be purchased in bulk? I think this could make an excellent pack cover, poncho , ground sheet, rain chap. I have tried the dollar store type "emergency poncho" and they tear very easily.

The turkey bag product seems to have some slight permeability and is much more tear resistant. Haven't found its equal in a bulk form yet. Thanks.

[Berserker]

Nothing to add here other than holy crap! I didn't realize a sil-nylon tent would retain that much water weight. Glad I've been using a pack towel to wipe my tent down for years...apparently been saving myself from carrying a good bit of extra water weight for years.