Cuben fiber

[Lawson Kline]

A test meter is alot different then real world conditions. I personally think Steve has been lucky because a tarp made from .33oz cuben is nothing more then disposable gear. If you can tear the material with your bare hands it has no business being used as shelter.

[Erik Danielsen]

Tearing a material with your bare hands involves putting a whole lot of force in opposing directions on a very small area of that material. A properly designed tarp or shelter is made to distribute wind-generated force over a larger area of material.

I really don't think tearing by hand is a good test of whether or not a material is worthy for an application that doesn't involve resisting being torn by hand. I'd say it's just as removed from real-world conditions as testing with a test meter (perhaps moreso, as a test meter could be used to at least measure the tear strength on a distributed area with a properly designed test).

The mylar and LDPE tents recently used at philmont come to mind. Both materials shred VERY easily by hand, but the tents were designed with load distribution in mind and it sound like they held up pretty darn well. No gale-force winds, admittedly, but 0.33 cuben is a much stronger material than either of those.

[Lawson Kline]

I disagree.

LDPE stretches and deforms while .33oz cuben tears. A tarp is a tension structure that requires tensioning in opposing directions to keep the structure taut. This is the same reasons materials either stretch or tear.

[Ike Mouser]

Can someone comment on the High-Bias Cuben Fibers? i was thinking of .7oz for tarps and .33 oz for other stuff as i said, but a helpful member (TIM of enlightened equipment) recommended ordering a size between these two and using it for both, to cut costs. THat way i only have to order one size. But looking at the CF3 file cubic tech sends it seems that CT0.3HBK.08 would be a decent middle point. It is 17.4g/m^2 and is high bias meaning it has more support fibers in it. Does anyone know if a high bias 17.4g/m^2 cuben fiber would be as strong as a non-high bias 25+g/m^2 fiber?

It would be expensive($33) for 9 yards of this stuff, but would still be cheaper than buying two different sizes.

[Dan @ Durston Gear]

Most tents/tarps are made with CT2K.08, which is the 0.74oz stuff. MLD, BPL, HMG, Zpacks etc are all using this stuff for their tarps/tents.

If you wanted to look at lighter variants, you've got 0.33oz, 0.48oz and 0.51oz. I think the 0.51oz stuff would work okay if it was used in a well designed shelter. I don't think there's much point in using the 0.48oz stuff since the 0.51oz stuff is barely heavier and it has a lot more spectra. The 0.33oz stuff makes me nervous. It can work, but there's not a lot of margin of error and when you're spending this amount of money most people prefer to go with a safer material.

If you think about a 0.7oz cuben solo tarp, most of them weigh about 6oz + 1-2oz guylines and 2oz stakes, for a total of 9-10oz. Of that 6oz tarp weight, the cuben is probably 4-5oz and the rest is the adhesive, reinforcements and guyouts.

So if you went with 0.51oz cuben instead of 0.74oz then you'd likely only save 1 or 1.5oz, for a total weight with stakes and guylines around 8oz instead of 9-10oz. Taking this further, using 0.33oz would lead to a total around 6-7oz. So ultimately you are only looking at a couple ounces difference between fragile 0.33oz cuben and bomber 0.74oz cuben. When you spending this kind of money, most people will opt for the 0.74oz cuben that will last longer.

0.33oz cuben is really for people who have shaved every other possible ounce off their kit and who have a desire to push the limits. It's fun stuff to experiment with, but likely not a good choice if you are spending hundreds on a tarp that you want to get years of use out of.

[Bill Fornshell]

Hi,

The reference on the RBH Designs web site about their Cuben Jacket to "wear over one of the newest…." is a typo and should have been "wear under". I expect you will see this changed quick.

I just called them and asked about this so it might take them a little time to get it corrected.

[Dan @ Durston Gear]

"Does anyone know if a high bias 17.4g/m^2 cuben fiber would be as strong as a non-high bias 25+g/m^2 fiber?"

So the comparison here is CT0.3HBK.08 to CT2K.08. Both variants are using the same ultra thin mylar layers and the difference is just in the spectra inside. The high bias cuben is using the same spectra as we see in the 0.33oz cuben, but you get 2x as much because it's layed not just at 0 degree and 90 degrees, but also at +/- 45 degrees.

Cubic Techs specs show only marginal increases in strength for the high bias variants. For example, CT0.3K.08 is rated at 35lbs breaking strength, whereas CT0.3HBK.08 is only a little higher at 37lbs. 0.7oz cuben (CT2K.08) is much stronger at 105lbs.

It's pretty clear from Cubic Techs specs, that for the same weight you are better off using non high bias cuben. CT0.3HBK.08 is 37lbs breaking strength and it weighs 17.4g/m2. The non-high-bias CT1K.08 also weighs 17.4g/m2 but its much stronger at 68lbs breaking strength.

If you want to order one type of cuben between 0.7oz and 0.33oz, I would suggest the 0.51oz CT1K.08.

The main advantage of high bias cuben is that you have strands of spectra laid in more directions, so it's going to be pretty strong no matter what angle you yank on it. With regular cuben just having the spectra in 2 angles, you need to put a bit of thought into how the cuben is oriented.

[Chris Lucas]

A tarp when used as a tarp is only under tension. There should be no abrasion, tearing, peel, cleavage, or other stranger forces like torsion acting on it. 0.33 has outstanding tensile strength. The mylar film is the same between 0.33, 0.48, 0.51, and 0.75 so abrasion or perforation concerns apply equally to all of them. So we're back to tension. How much spectra do you need to resist the tension placed on the tarp? I strongly suspect 0.75 is massive overkill and evidence is mounting that indeed 0.33 may be perfectly sufficient.

[Erik Danielsen]

Lawson, I did also mention the Mylar tents that were produced prior to the LDPE tents and also did alright. Cuben being essentially mylar plus spectra threads, if one can make mylar work, one should certainly be able to make any variety of cuben work. Again, design for optimum force distribution as well as careful pitching and site selection will be important, and of course even moreso with the mylar tents, but far from being unfeasible or even useless. If I recall, Big Sky showed a tent at Outdoor Retailer Summer Market 2010 that incorporated 0.33 cuben, and they are known for being quite picky with their materials. Add to that the fact that other shelters have been successfully made and used with 0.33 cuben and I really don't think there's any good reason to declare it unworthy. Its strengths and weaknesses simply need to be taken fully into account when working with it, as is true with any material.

[Erik Danielsen]

Chris, don't forget that wind and heavy precipitation may generate torsional forces and possibly, in a poorly designed shelter, cleavage or tearing forces (if two tension panels are pressured in opposite directions, perhaps).

[Dan @ Durston Gear]

"If I recall, Big Sky showed a tent at Outdoor Retailer Summer Market 2010 that incorporated 0.33 cuben, and they are known for being quite picky with their materials."

They did show a cuben version of their Mirage tent but I've never read anywhere that it uses 0.33oz cuben. A close up picture appears to show too much spectra in the cuben to be the 0.33oz stuff (but I could be wrong). It looks like Olive Drab CT2K.08 to me:
http://hrxxlight.com/wp-content/uploads/2010/07/P1030602.jpg

Lightheart gear is using 0.48oz cuben (CT0.6K.08) for their new solo tent.

[Erik Danielsen]

Hmm. I thought I'd read that in the OR report. It may have been in a thread specifically on the tent, however, as I recall browsing one. Might have read something from an iffy source. On review, consider it unconfirmed/questionable.

[Lawson Kline]

Hey Erik,

Mylar and LDPE cost pennies on the dollar compared to cuben fiber so building shelters out of these lower cost materials isn't really a huge financial loss when heavy winds reek havoc. If anything the knowledge gained from building these type of low cost shelters could improve shelter desings and construction techniques. But I can't agree that .33oz cuben is a suitable material for shelters. Its cost is too high and is strength is too weak. Sure on paper it might work but all it takes is one pin hole while the tarp or tent is in tension to cause total material failure.

This is exactly what happened with my cuben hammock. On paper it was the perfect material with it's 105lbs of breaking strength. When one of the hammock test models failed it didn't slowly tear it catastrophically failed. I sent the hammock to a Materials Scientist and a Materials Engineer and they both concluded CT2K.08 .75oz cuben fiber should never be used for a hammock even though it has more then enough strength on paper. I had 40 emails from people wanting cuben hammocks and wasn't confinced the material wouldn't work so I did a battery of fail tests. The first test went like this. I hung the CT2K.08 hammock and sat down in it (I am 6'1 and weigh 200lbs) I took an aluminum nail peg and stabed the hammock. I was on the ground before I even knew what happened. Just like one of the test hammocks the material catastrophically failed.

I was really upset because I spent alot of time and money getting the hammocks ready for production but there was no way I would sell something that could hurt someone. I have since switched over to 30d silnylon (70lbs an inch break strenght which is 35lbs less then CT2K.08 .75oz cuben fiber) and I can stab holes through it all day long while laying in it and it will not fail. I am sure with enough holes it will but one of my test models has over 100 holes and I tested it to 500lbs the other day with no signs of failure.

I am not arguing with you to be right. Instead I am giving my opinions of why someone shouldn't waste their time or money with such a lightweight expensive material (.33oz cuben fiber) when the CT2K.08 .75 oz stuff works great for tarps and shelters.

Cheers,
Lawson

[Tim Marshall]

for me it comes down do the balance of cost, weight and performance.

I agree that .33 is too light for shelters as the reduced amount of spectra that reinforces the film makes it pron to abrasion issues. Even though .48-.74 all use the same film i have found that all of them are much more abrasion resistant than .33 as there is more spectra backing/reinforcing the film.

I recommended .48 or .51 as a way to order only 1 9m piece instead of needing a piece for a quilt and 1 for a tarp, but this advise is wasted if the design calls for more materials than 9m will provide. If you need more than 9m you will have to order 18m so you might as well get .33 or .48 for the quilt and .74 for the shelter. However, if you only need 9m for both items then use the .48/.51 which i believe should work very well if the shelter is well designed.

-Tim

[Steven Evans]

This is a great thread.

I actually don't even like making recommendations on cuben fiber to someone who has no experience with it, just because I think it is important to feel/hold several weights before making a decision. I usually tell people to order the sample pack and get an idea of what they're getting into and then we can discuss options. The weight of fabric suitable for each application really depends on the conditions, terrain, weather, site selection, user expereince, etc.

Example…
N2 Tarp (0.33 oz/yd): Designed for low level forested areas where natural windbreaks are plentiful.

All-WET (0.74 oz/yd): Designed for exposed areas where full body coverage is required from the elements (wind, rain, etc.)

Also, I think it was Thom Darrah who had a custom tarp made from cuben fiber (1.5 oz/yd): Designed to be used above treeline and withstand substantial wind/rain/elements.

So it really does depend on it's intended use.

With that said, I've been using the 0.33 stuff for a while now and I feel there is potential for it to be used more and more. Remember a few years ago, everyone was super worried about the 0.6 oz (now 0.74 oz) stuff and now it is considered bomber (which I agree with). Who knows, in a few years we all might be using sub 2 ounce full sized tarps.

As for the tarp in the video link above. The N2 tarp has literally amazed me with it's performance. I thought FOR SURE it was going to get torn to shreds in Zion while camping on the mesa but it held strong all night through the wind and rain. I wouldn't consider it a crazy storm or anything, but that was the worst that tarp has been exposed to. I have much more confidence in it now. Based on that night, I did some more tieout tests on the 0.33 oz/yd CF and was really happy with the results.

0.33 oz/yd Tieout Test

In the tests, yielding in the superior performer occurred at about 80 lbs. Have you ever lifted an 80 lb dumbell? It's freakin' heavy! I realize there is more to tarp stresses than a simple hang test, but it gives you an good idea of its ability. I can't wait to read Chris Lucas' article on testing cuben fiber. People are usually afraid of the unknown so it will be nice to put some solid numbers to the fabric.

I think pushing the limits is fun and exciting. Its what I enjoy doing and there are others out there who are like minded. I get e-mails asking to buy an N2 tarp all the time (I don't sell them) so if anyone wants to make them, go ahead.

[Lawson Kline]

Hey Steve,

As always nice job on your testing. I would love to see someone test a strip while poking a hole through the material with a sharp object.

[Doug Hus]

So is .6 oz/sqyd cuben fiber tuff enouph for a tarp/tent?
Doug

[Dan @ Durston Gear]

I would say CT2K.08 aka 0.74oz cuben (which is still sometimes called 0.6oz) is stronger than the silnylon used commonly in tarptents. So yes, it would work well.

It doesn't seem to have quite the same abrasion resistance though, so it's not ideal as a standalone floor. For a floor, 1.2oz cuben is really the minimum in my opinion if you don't want to use a groundsheet. That's the lightest way to go, because IMO a lighter floor requires a groundsheet so your total weight is higher. 1.2oz cuben or 1.5oz (same mylar layers, different amounts of spectra) seems pretty bomber as a floor material. A rodent can barely chew through this stuff.

[John Roan]

The .6oz is what zpacks uses on their Hexamid tarps and tents. I have the twin version tent, and after about 20 nights of use this summer, I believe it will last a very long time. Just be careful with sharp object, as it isn't very puncture proof.

If you want something more puncture proof, with with the 1.5oz, which works very well on backpacks.

[Dan @ Durston Gear]

FWIW, I talked to Joe from Zpacks and the '0.6oz' stuff he is using is actually 0.51oz CT1K.08. Joe has now changed this on his 'materials' page:
http://zpacks.com/materials.shtml

[John Roan]

This supports the idea that a well designed shelter will work with .51 oz cuben. The zpacks Hexamid design does not require a drum tight pitch like catenary cut tarps and other shelters do. This puts less strain on sewn seams.

[Ike Mouser]

I knew they were using CT.1K.08, i ran the calculations and it just didn't add up that they were using .6oz stuff. Its really tempting to have a 5.1oz hammock tarp but im still not sure about .51oz in a massive storm, especially sewn.

[Sam Farrington]

John,
Must dissent. When the loose or sagging pitch gets hit by high winds, there will be plenty of stress on the fabric, especially if the wind gets into the shelter and there is a wind pocket effect. But just billowing and snapping creates stress as well.
Oh, how I wish a WP polyester around 1-1.5 oz could be found.
Sam

[Anonymous]

""I do however have a prediction of whats going to happen. Some company is going to realize there is a huge demand for a really lightweight strong materials at an affordable price. The material will become a huge success and will go mainstream.""

This prediction is so overdue that the prophet risks stoning. However, I too, have been sure for years that the revelation of this new material is imminent, only to be disappointed year after year. I recall reading here in this forum about 3 years ago that General Electric or a subsidiary had a patent that was just being sat on at the time it was discussed here. Anyone recall this in more detail?

[Dustin Short]

Sam's right. The problem with cuben is that the spectra has very low stretch, so any shock forces cause it to tear (usually catastrophically). It's called jerk and is the reason why bullets penetrate anything. Lead is soft, and if you slowly push on it the same forces it feels being shot from a shell, the bullet would just flatten. But if you apply that force over a short enough time, the bullet pierces. Wind does the same thing, and when a loose pitched cuben tarp snaps, the forces start becoming high enough to tear the material. A tight pitch has little deflection, therefore little to no snap and the wind moves around the panel instead of trying to pierce it.

The inability to absorb sudden forces is why the lighter weight cubens are not ideal for shelters unless the user knows how to pick a naturally sheltered campsite.

This is the main strength behind using silnylon, it stretches so is much more forgiving of a loose pitch. As it stretches, it effectively lengthens the time that the force is applied over, bring jerk forces below the maximum strength of the silnylon.

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