cuben tarp heavy after rain?

**Joey** · 10-28-2011, 05:14

So I was out Monday night and slept through a nice steady rain. My cuben fiber tarp kept me dry, and the sounds of the rain had me hard asleep. After I packed everything up I removed the stakes and shook the tarp a bit to get the rain drops still remaining off of it. It had stopped raining at this point. As I began to roll the tarp into the mesh skins I noticed it felt a lot different than normal. As I untied it from the tree I noticed it was a lot heavier. Suddenly my 6 oz. cuben tarp weighed about 2lbs! It was like the material itself had absorbed the rain?

I set it up over my lunch break, during my hike, and it dried out quickly with a little sunshine and light breeze. I'm still trying to figure why it was so heavy. Anyone else experience something like this? I've had my silnylon tarp absorb a bit of water, but not get noticeably heavier as a result. This was very noticeable.

WV · 10-28-2011, 08:40

I carry two small (7" x 9") pieces of "Zorb" fabric (like a backpacking towel) so I can dry my tarp when I take it down. I release the side tie outs so the tarp hangs straight down, then hold one towel with each hand and wipe down both sides at same time. This gives something to push against. Even after a light rain, a surprising amount of water gets wrung out of the towels when I'm done - but not 2 lbs. worth.

What tie-outs are you using? Some, such as nylon mason's line, can absorb a lot of water. How about reinforcement patches for the tie outs?

I'm tempted to weigh my tarp, hang it in the rain tonight, and then weigh it tomorrow morning. If I get around to it, I'll post results.
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Interesting! I just took a 12" x 24" piece of aluminized cuben and weighed it, then got it wet and weighed it again, then wiped the drops of water off with a paper towel (but didn't get it completely dry).

Starting weight (dry): 4 grams on my postal scale - This scale is only accurate to 2 grams, so this reading is really "3 to 5 grams", which is in line with the calculated weight by area (2 square feet) of 5 grams.

Wet weight: 16 grams

Weight after wiping off water drops: 6 grams

Conclusion: water is heavy!

**Joey** · 10-28-2011, 08:56

Originally Posted by WV

I carry two small (7" x 9") pieces of "Zorb" fabric (like a backpacking towel) so I can dry my tarp when I take it down. I release the side tie outs so the tarp hangs straight down, then hold one towel with each hand and wipe down both sides at same time. This gives something to push against. Even after a light rain, a surprising amount of water gets wrung out of the towels when I'm done - but not 2 lbs. worth.

What tie-outs are you using? Some, such as nylon mason's line, can absorb a lot of water. How about reinforcement patches for the tie outs?

I'm tempted to weigh my tarp, hang it in the rain tonight, and then weigh it tomorrow morning. If I get around to it, I'll post results.
----------
Interesting! I just took a 12" x 24" piece of aluminized cuben and weighed it, then got it wet and weighed it again, then wiped the drops of water off with a paper towel (but didn't get it completely dry).

Starting weight (dry): 4 grams on my postal scale - This scale is only accurate to 2 grams, so this reading is really "3 to 5 grams", which is in line with the calculated weight by area (2 square feet) of 5 grams.

Wet weight: 16 grams

Weight after wiping off water drops: 6 grams

Conclusion: water is heavy!

Thanks WV! I was only guesstimating the 2lbs of gain by what it felt like. Your test shows there is a considerable amount of water retention with cuben, which was something I wasn't expecting or prepared for. I will add a small wipe down cloth to my pack list for my next hike!

**ShadowAlpha** · 10-28-2011, 09:00

interesting test WV!
yes! water is heavy

**BearChaser** · 10-28-2011, 11:14

That is interesting. I was thinking Cuben did not absorb water. WV, do you think the water is being absorbed between the layers, have you weighed it again after the test? It would be interesting to see how quickly it dry's out.

**SmokeHouse** · 10-28-2011, 11:22

Thank for this Info,,, have you did a test at home yet... weigh it dry, then spray the tarp down or let it rain on it and weigh the tarp again... I would love to know the results of that.

**Rug** · 10-28-2011, 12:03

This brings up several interesting questions.

a few that come to mind:

Winter durability: if the water is being drawn in-between the layers (capillary action is the most probable cause) what happens when it freezes during the winter.

Delamination would be my biggest concern about this fabric with this news, even if repeated freeze/thaw cycles don't happen. A good way to test the material would be to take a small sample, submerge it in water for x minutes, and then place in the freezer.

If anybody has 2 small strips that they want to send me I can do some through testing and post the results.

WV · 10-28-2011, 13:31

Originally Posted by BearChaser

That is interesting. I was thinking Cuben did not absorb water. WV, do you think the water is being absorbed between the layers, have you weighed it again after the test? It would be interesting to see how quickly it dry's out.

Just weighed it again, and it's back down to 4 gm. Remember that on my scale "4 gm." means "between 3 and 5 gm." Similarly, "6 gm." means "between 5 and 7 gm." The piece tested should weigh about 5 gm, so it's likely that all the weight gain when wet was surface water, not water absorbed by the material.

I probably should do comparison tests of a cuben tarp and a silnylon tarp. I would expect the silnylon to absorb water, but not the cuben. I wonder if they both hold the same amount of water on the surface. Probably not.

**Joey** · 10-28-2011, 13:37

Originally Posted by WV

Just weighed it again, and it's back down to 4 gm. Remember that on my scale "4 gm." means "between 3 and 5 gm." Similarly, "6 gm." means "between 5 and 7 gm." The piece tested should weigh about 5 gm, so it's likely that all the weight gain when wet was surface water, not water absorbed by the material.

I probably should do comparison tests of a cuben tarp and a silnylon tarp. I would expect the silnylon to absorb water, but not the cuben. I wonder if they both hold the same amount of water on the surface. Probably not.

I appreciate these tests, and am very curious about cuben/silnylon comparison. I'm still thinking my cuben tarp absorbed that rain. I shook it off, and it should not have weighed as much as it appeared to have. If it were surface water, most of that should have gone when I shook the tarp, correct? It was a rather vigorous shake. Especially after I unhooked the tarp fly on one end and felt the weight in my hand. I reconnected it and shook it again. It was 5:30 am, and dark so I was working via headlamp. When I set it up later that day I looked at it and could not figure where the water was, but I could sure feel it!

**Poppabear** · 10-28-2011, 14:18

This thread is very thought provoking and poses some very interesting questions. I've been eyeballing cuben traps for quite awhile and was seriously considering ordering one. Now I am having second thoughts and I will be watching here to see how this discussion progresses before making the plunge.