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!

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

[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]

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[Kookork]

Did you wash your hands between touching the different tents?

[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

[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.

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.