Forum Index » GEAR » Cuben - The 422 mm hydrostatic head dirty little secret


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dan mchale
(wildlife) - MLife

Locale: Cascadia
figures on 03/20/2011 18:00:15 MDT Print View

As far as I can tell, a hydrostatic head of 422 means that particular Cuben Fiber, if fashioned into a stuff bag 16.5" tall, it would hold the water if filled and hung up. That sounds pretty waterproof. What I find amusing Roger is given that, you are arguing against it's usefulness in UL packing for tarps, ponchos, raincovers, and many other practical things based on standards that, by the nature of standards, are in excess of what is needed anyway.

I think a more practical way to approach this would be to find out what the minimum fabrics are that do the job we want them to, and then find out what the HH figures are for those. It seems that much of UL packing has to do with risk assessment so I don't understand your resistance to seeing different meanings of what waterproof can be. This is the practical way to go about things. What is showing here is how limited things can be when we accept standards somebody else set up that we do not question.

We need more information about lifetime and degradation of many fabrics. Most of them get wasted by UV alone, and in that sense I'm willing to bet Cuben has done it's homework.

Edited by wildlife on 03/20/2011 18:42:39 MDT.

Lawson Kline
(Mountainfitter) - M

Locale: LawsonEquipment.com
Cuben Fiber on 03/20/2011 18:49:34 MDT Print View

I agree with Dan Mchale, hyrdostatic head numbers NEVER translate into real world performance. I have been using one of my CT2K.08 9'x9' flat tarps for over two years now and never once has it ever "misted". At .75oz no other material can compare. Cuben Fiber is super strong, amazingly lightweight, has amazing tear resistance, doesn't absorb moisture, has awesome UV resistance, and is one of the most real world water resistant material available.

Edited by Mountainfitter on 03/20/2011 21:00:53 MDT.

Dave U
(FamilyGuy) - F

Locale: Rockies
Cuben on 03/20/2011 18:54:55 MDT Print View

"As far as I can tell, a hydrostatic head of 422 means that particular Cuben Fiber, if fashioned into a stuff bag 16.5" tall, it would hold the water if filled and hung up. That sounds pretty waterproof."

How does this test water that is moving at speed, i.e. water pressure? A simple DWR could handle that.

Edited by FamilyGuy on 03/20/2011 18:55:48 MDT.

drowning in spam
(leaftye) - F

Locale: SoCal
Re: waterproof cuben on 03/20/2011 19:32:40 MDT Print View

I too would like to see additional testing, but regardless of the results, I'm still going to be using cuben fiber for my shelters whenever I can afford it.

dan mchale
(wildlife) - MLife

Locale: Cascadia
tasty 20 mph on 03/20/2011 19:41:23 MDT Print View

David, from information from an earlier post I made, I passed on that the minimum British standard for waterproofness was 1000mm and that rating could handle rain wind driven to 35 MPH. The maximum rate of falling rain is 20 MPH so using these numbers we need about 571mm to handle 20 mph rain. 15 mph rain would need 429mm. We don't really know how that was determined in the first place though, that 1000mm, so we're in the same ball-park with 422mm - Richard's test number. If that 1000mm came from the same place that brought us ' a pound on the foot is 5 on the back' we can probably add some NaCl to it and call it a day.

Did you do your homework yet and test your Cuben bags? I just hope the seams are well sealed in order to hang water.

Edited by wildlife on 03/20/2011 20:16:50 MDT.

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Re: Re: Re: scientific type on 03/20/2011 20:24:47 MDT Print View

"Does that mean Cuban Fiber should not be used for a shelter? I never said that, and I don't think Richard did either. I imagine it could be used in mild conditions very happily, although I think we need more information about lifetime and rate of degradation."

Ah, the sweet voice of reason.

ROBERT TANGEN
(RobertM2S) - M

Locale: Lake Tahoe
Cuben anecdotal evidence on 03/20/2011 20:24:53 MDT Print View

FWIW, here is a bit of anecdotal evidence from an online reviewer:
“I can say for sure that the [Cuben-fiber Rocket Tent] is dry. The fabric is waterproof. It rained, and occasionally snowed big, wet flakes, for about twelve hours straight. Every piece of fabric that I had with me got wet. The outer layers of all my three-layer, waterproof fabrics got soaked; the pack was soaked; boots; gloves; you name it. And I wasn’t ever out for long. The tent didn’t let one drop of water in. As a matter of fact, when it was time to take it down, I removed all the anchors and ski poles, and just held it by the probe in the wind. It flapped away for about three minutes, and was pretty much dry.”

dan mchale
(wildlife) - MLife

Locale: Cascadia
risky business on 03/20/2011 20:59:10 MDT Print View

Roger said he did not 'think' Richard said Cuben should not be used for a shelter either. Here's what Richard said after saying it's a POOR SOLUTION for rain;

"Unless Cubic Tech or Mountain Laurel Designs can solve the problem with the poor hydrostatic head performance of my MLD Cuben Grace Duo I will probably never buy another Cuben product. I still have a couple of Granite Gear Cuben dry bags. Sometime before packrafting season I will test them to see how much at risk I am using them."

At Risk? Sweet voice of reason?

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: risky business on 03/20/2011 21:13:06 MDT Print View

"At Risk? Sweet voice of reason?"

Dan - I was referring to Roger's last post. Maybe I should have qualified it by referring to Roman Dial's earlier comments about a Cuben shelter being his go to for many of his hikes in Alaska, known for its wet weather. He did say that for worst conditions, he used silnylon, though, IIRC. It wasn't a matter of total waterproofness for him, rather enough waterproofness to justify its lightness and protect him from the worst of the downpour. Tradeoffs you make in the real world?

dan mchale
(wildlife) - MLife

Locale: Cascadia
not on 03/20/2011 21:50:20 MDT Print View

Sorry Tom, I was just pointing out the quote you selected was largely untrue regarding what Roger said Richard said.

Roger said this about Richard; "Does that mean Cuban Fiber should not be used for a shelter? I never said that, and I don't think Richard did either."

I then supplied what Richard said early in the thread. You must have missed it. It's very easy to deduce that Richard does not think Cuben should be used for shelter. It's as good as saying it.

Edited by wildlife on 03/20/2011 22:00:30 MDT.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Random WP Definitions and Tent Fly HH Ratings on 03/20/2011 22:24:32 MDT Print View

wp4


Two weeks ago I posted the HH values that I personally define as waterproof and a brief explanation as to how I calculated them. For what it is worth, they are similar to what the above sources also define as waterproof. See: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=43902&skip_to_post=373814


TF2

Edited by richard295 on 03/21/2011 00:32:57 MDT.

josh wagner
(StainlessSteel) - F
hehe on 03/20/2011 22:32:57 MDT Print View

when you guys get all done being sciency, will someone please PM me and tell me to whether or not to trade in my spinntex tarp for cuben?
thanks,
a layperson

dan mchale
(wildlife) - MLife

Locale: Cascadia
spectra not hard on 03/20/2011 23:42:26 MDT Print View

Roger, I wanted to point out that I believe you are assuming Spectra is a hard thread when you say this a few posts back;

"In other places the total thickness will be that of two layers of Mylar film PLUS two layers of very hard Spectra thread."

Because you say that, I don't believe you are familiar with Spectra. It is a strange fiber and is very supple and can morf quite readily around corners. If the Mylar gets compromised, it is in the HH machine doing the testing. That's not cool. I said something similar but only in reference to the mylar being damaged during testing, not during manufacturing. Cuben does not claim to use Spectra anyway, but the dyneema is similar.

It would be interesting indeed if it was the machine causing the relatively low HH numbers because it damages the fabric. I'm not going to count on that though.

Edited by wildlife on 03/21/2011 02:17:09 MDT.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: .7 oz/yd2 CTF3 (Cuben) - The 422 mm hydrostatic head dirty little secret on 03/21/2011 00:29:34 MDT Print View

My cuben tarp has never leaked. But then I do not live in the PNW. But it has been is some serious thunder storms. I can also tell you that a mouse can chew through a cuben sack.

Last night I had dinner outside of my tent. Temps below freezing, my Fugu jacket kept my body warm (thanks Richard), and the pack pad from my McHale kept my butt warm and dry while sitting on snow (thanks Dan), these are the things I look for; functionality.

ziff house
(mrultralite) - F
CUBEN on 03/21/2011 00:30:24 MDT Print View

is da' bomb man..

I see Event is listed at 15-30000mm, there's another big debate, how come i always get soaked when i wear that thing?

Wayne Wagner
(wagnerw) - F

Locale: NorCal
Re: figures on 03/21/2011 01:32:58 MDT Print View

=>As far as I can tell, a hydrostatic head of 422 means that particular Cuben Fiber, if fashioned into a stuff bag 16.5" tall, it would hold the water if filled and hung up. That sounds pretty waterproof.

I'm not sure how you got this number. It seems to me that 422 mm is less than 1.5 feet of static water. Of course, static water on your tent/tarp is likely to be less than a few mm deep (unless it is pooling). If the water were wind-driven or falling (as rain tends to do), then I imagine you would need more than a few mm of HH resistance in your fabric to stay dry.

I am not sure; do we have a number that is the accepted number for HH in a tent or tarp? Is 1000 mm just some arbitrary round number that is close enough to waterproof or is it what we should be looking for in a tent fabric?

Wayne

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Re: Rain Room Tests Show That Some Fabrics With Less Than 1,000 mm of Water Resistance Keep Water Out on 03/21/2011 01:33:13 MDT Print View

Jeff,

Equilibrium allows a somewhat porous 10 CFM and typically doesn't have a good DWR treatment; so it is not the ideal for the Fur-tech concept but it will work. Fix the DWR by washing the jacket in non-detergent soap, add a good fluorocarbon DWR like Grangers, and dry at 140F for about 15 minutes to set the DWR. Add a thick fleece under it and it should act like a regular WPB rain jacket ensemble.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Re: figures on 03/21/2011 01:45:28 MDT Print View

Wayne,

I am not sure if your question is addressed to a specific person. If it is an open question, then my answer is 3,000 mm if you want to avoid misting from low HH. 1,500 mm is Ok if you have a bivy or WPB shell on your bag to shield yourself from mist related to low HH. This answer assumes you will be camping in areas that are vulnerable to Thunderstorms with typical 4.5mm max drops.

1,500 mm is the minimum European HH standard. 1,000 is a fur-tech proposal based on wearing a thick fleece under a 1,0000mm garment.

Edited by richard295 on 03/21/2011 15:00:50 MDT.

dan mchale
(wildlife) - MLife

Locale: Cascadia
hydrostatic testing at home on 03/21/2011 02:49:00 MDT Print View

Richard, couldn't somebody just take a clear tube and hose clamp some fabric to the bottom of it to create a tester? All you have to do is graduate the cylinder and make sure the clamp or clamps don't leak. Am I correct?

Thom Darrah
(thomdarrah) - MLife

Locale: Southern Oregon
figures on 03/21/2011 02:49:02 MDT Print View

Now I know why I should not have skipped science class to go out and run when in school. :(