Cuben tent for mountaineering?

[matt brisbin]

I've seen a ton of cool tents come through this message board and figured you guys/gals would have some good input/thoughts on this. Why is it that I haven't seen many 4-season cuben mountaineering tents? To me, the fabric seems quite robust and with it being fully waterproof it would make a great mountaineering tent… also super light. Perhaps it behaves oddly in cold environments?

[Colin Krusor]

I'm not sure of the answer, but it occurs to me that ultralight backpackers are willing to pay for a $500 cuben tarp/tent that replaces a $250 nylon one to save a few ounces. Tent manufacturers might have concluded that mountaineers are not likely to value small weight savings so highly. This is the major reason, I would guess.

Cuben doesn't perform differently under cold conditions than under warm conditions (within the range of normal outdoor temps, ie -30F to 100F).

[matt brisbin]

Good point!

Yeah, I can see that being the case for large scale manufacturing. I was more-or-less focused on the MYOG'er/mountaineer which is why I posted here. Sorry if that was unclear. Perhaps this question is better suited for summitpost :-)

[Roger Caffin]

It's rarely used because it is not trusted.

After lots of creasing the Mylar cracks at the creases and the fabric leaks quite easily. The heavier gauges are less prone to this, but they are heavy.

The fabric has no stretch, so it is hard to get a good pitch without creases. So it flaps a lot more, which can be damaging.

The fabric has no stretch so it cannot absorb shock loads the way silnylon does. This means it can fail catastrophically. Silnylon has a remarkable ability to handle extreme conditions safely.

You cannot sew onto Cuban with safety, without a lot of reinforcing. The stitch holes have a very bad habit of growing under load. To be sure, this can be handled – mostly, but doing so adds weight.

Cheers

[matt brisbin]

Roger,

Thanks for the insightful response. Good to know. I haven't personally worked with cuben but do own a zpacks tent for fair-weather conditions. I've folded my tarptent numerous times over the course of a year and haven't experienced it leaking. I assume your talking about the waterproofness degrading over a very long span of time?

As for the material not being able to stretch. What are your thoughts on using a shockcord as a guyline to keep things taunt during heavy winds (just thinking/typing out loud)?

[Roger Caffin]

You may need to test your tarp under a bit of water pressure. First noticed under heavy rain of course, then it gets worse as the cracks at the folds develop. Search here at BPL for hydrostatic head testing – some time ago.

Shockcord – we had a thread on that very recently. 'Lots' of shock cord just lets the tarp flap badly. A very short loop of strong shock cord might be useful with Cuban.

cheers

[Ryan Smith]

Have there been any reports of cuben actually leaking in the field? I know Richard N was able to make it leak in his suter tester, but anyone actually experience it? There are thousands of .51 and .75 cuben tarps/shelters out there, so there should be at least some reports of it happening if that test is indicative of performance.

Ryan

[dirtbag]

What about cuben rain gear? Add all the tarps, tents and rain gear that's out there..heck what about just the gear that's on BPL forums..plenty of us have/use it. Any leaks or problems?

[Randy Martin]

Mountaineering tents are very beefy to handle the severe winds and snow loads they need to encounter. It's a much less forgiving environment. Even in Nylon, true mountaineering Tents are so expensive (generally > $500) that I would imagine a Cuben version would be ridiculously expensive. Some other considerations are that in mountaineering you can't be worrying about what will happen to your tent if it's scraped by rock, accidently punctured by a crampon etc.. It's just not a place you want to be worrying about babying your gear.

Cuben doesn't do well with abrasions or punctures that weaken the material unlike ripstop nylon which doesn't care too much about punctures and the like.

[Roger Caffin]

> What about cuben rain gear?
Well, if we ignore Gore's utterly fatuous claim of 'guaranteed to keep you dry', then there is considerable concensus that in bad weather you are very likely to get a bit damp inside your gear. One of the biggest reasons for this is that when your sweat hits the rain gear, it condenses on the inside. No, Virginia, breathable rainwear simply does not exist.

OK, given that you are going to get wet in sustained bad weather, will you notice a few extra leaks coming through the Cuben rain gear? Unlikely, imho. As long as it sheds 99% of the rain you are fine.

Let us move on to tarps etc. The same problem obtains: you get condensation on the underside in bad weather. Some people claim that the water shows the roof is leaking, but very often most of that water is condensation. Will you notice one or two extra leaks coming through the Cuben? Probably not, at least until the leaks become quite bad. For many users this might not happen for 5+ years, as they are not using said tarp every weekend of the year.

Does this mean that Cuben tarps work? Well, mostly, they do. Relax your expectations slightly, and they are fine, at least below the tree line.

Cheers
PS: yeah, spelling …

[Ken Thompson]

@Roger. Do you need to teach your spellchecker about cuben vs. cuban? As they are not the same thing at all.

[todd]

Ken,

Sounds like you're nagging.

[Ken Thompson]

anyway.

I am just pointing out something that I have noticed happening repeatedly.

Have a nice day Todd.

[Jerry Adams]

I too have been saying to myself "it's Cuben, not Cuban!" : )

Cuban fabric probably wouldn't be so good

But I understand what's being said so I guess it doesn't matter…

[Ron Moak]

I’ve been working with Cuben for over 5 years and have a pretty good idea of its properties, both good and bad. Unlike Roger, I’m far less quick to be dismissive about Cuben’s potential in mountaineering tents. For one, I’m not actually sure how much work Roger has actually done with Cuben in this field. So I question whether his observations are speculative or based on tested results.

Brooks Mountaineering created a Cuben Fiber tent several years ago. Yes, it was pulled from the market. According to my discussions with them at OR a while back, the basic problems was that the Aluminized Cuben was delaminating. Plus the fact that the tent was pitch black inside, even in the middle of the day. There was no indication that another variety of Cuben wouldn't have work well.

As to Cuben’s reportedly poor hydrostatic head, I can’t say that I’ve seen the same results as displayed in Rogers famous report. I do have a Sutter tester and my results on both new and 5 year old Cuben are significantly different.

Last summer I spent a night at 12,000 feet, above timberline, during a pretty intense storm inside a 5 year old Cuben fiber Gatewood Cape (yes Virginia, one does exist). I have to say I was quite comfortable and well protected despite the wind and rain.

With respect to Cuben’s poor abrasion resistance, that is in fact true. Nylon is indeed much better in this regard. However, if required to field patch a tent that was failing in adverse conditions, I’d choose the Cuben 7 days a week. It can be easily field repaired to functional using virtually any tape. Once nylon begins to rip there are only a few kinds of tape that will work and they can be finicky. If you’re using a silnylon tent, there is no tape available that will provide an adequate repair. Especially if you’re attempting to do so in the middle of the storm.

It is true that Cuben can be difficult and extremely expensive to work with. Once you’ve mastered the basic technologies of seam construction and distributed loading, I’m not sure what the limitations are. Truly learning its limits will require actually building and testing different models. It won’t come from making speculations based upon untested assumptions.

[William F]

I own a MLD cuben duomid, bought it used, and have only had the chance to use it on a couple of occasions so far. It strikes me as fairly robust when compared to silnylon tents I've owned in the past. I don't do mountaineering trips though so I can't speak to that particular application of cuben.

Specifically in regards to the point Roger C. has brought up, creating wear/failure because of repeatedly folding your cuben tent or tarp up in the same way, I just don't see how this would be a concern in the real world. The duomid I have has very minor micro creases on essentially every square centimeter of the mid. How it would be possible to fold along the same lines every time kind of baffles me. It would take an absurdly meticulous packing of your tarp/tent to create this effect in my opinion. Speaking for myself, as everyday goes by on the trail, especially if it's wet out and I want to get moving asap, I become progressively less careful in my packing. Most of the time I just shove the duomid into its stuff sack and try and keep the air vent at the tarp relatively flat.

[Jennifer Mitol]

I also find these kinds of threads interesting; there is a whole faction of people who claim cuben isn't tested enough, isn't durable enough, etc. Then there are others who have used the same cuben shelter across several thru hikes and never complained at all about the tent leaking or splitting or failing.

The first time I slept in a silnylon shelter during a nasty storm I sat in my tent that night wondering why it was raining inside…the misting created from the massive wind and condensation and, well, whatever…followed by packing up a seemingly 8 pound shelter the next morning had me searching for something else awfully quickly. I can't say that's ever happened in the paltry 2 seasons I've personally used cuben shelters……

But I do trust folks like Ron who have spent years working with the stuff, and Joe Valesko at Zpacks who won't work with anything else…and I have yet to hear of a really good failure story. After this many years and this many seasons of thru hiking since cuben has been relatively mass-marketed, I really wonder why the continued strong skepticism?

[David Ure]

Depends on the weight of the Cuben. 0.51 is not strong enough for high winds in my experience, nor does it have a high hydrostatic head. It will mist as much as typical silnylon, albeit being considerably lighter. Modern silnylon has a HH over 3500 mm now. Very high for shelter material and misting is a thing of the past (most who claim of misting are simply getting condensation knocked off the interior walls and is more a function of shelter design than the fabric choice).

I have some 0.74 stuff sacks that are quite shredded after two years of use. Granted, they are stuffed and creased – something that you may not do to a shelter, but there are pin holes in my stuff sacks. I have silnylon sacks that are 10 years old. Still holding strong.

Personally, I would want proven fabrics used in my mountaineering shelter. I consider Cuben proven but not for mountaineering and better for 3 season work. Even MLD suggests silnylon over Cuben in the snow given the natural stretch of the material.

[William Chilton]

I think the main reason for choosing silnylon in the snow is because snow sticks to cuben more.

[Roger Caffin]

Hi Ron

I did get some Cuben fibree fabric of various weights and did some testing over the weight range. But as you suggest, that was all done in the lab. So not speculation, but not vast field experience.

Richard N did most of the Suter testing. The lighter Cuben Fibre fabrics did show cracking at wear places, but as I said, in many cases you won't notice the leaks for quite some time.

> If you’re using a silnylon tent, there is no tape available that will provide an
> adequate repair. Especially if you’re attempting to do so in the middle of the storm.
Well, I have about half a dozen siloxane tapes which I have been using for 6+ years now to tape up silnylon. This is a 'known technology' and they work extremely well when used correctly. However, they do take about 72 hours for the bond to completely cure, so field repairs in the middle of a storm are not that easy!

I will reiterate my main concern: the lack of stretch. That makes getting the seams dead right really critical, and it means the fabric cannot absorb shock loads in a storm. These may not matter in a tarp of course, so the fabric can be great for that. But I have reservations about its use in a tunnel tent in a storm.

Maybe I should make one of my tunnels out of Cuben just to see. But I don't have the fabric.

Cheers

[Ron Moak]

>> I will reiterate my main concern: the lack of stretch. <<

It is true that Cuben doesn't have the stretch of Nylon. But then again polyester doesn't either and unless my memory fails me, it's been used in mountaineering tents.

>> That makes getting the seams dead right really critical, and it means the fabric cannot absorb shock loads in a storm. These may not matter in a tarp of course, so the fabric can be great for that. But I have reservations about its use in a tunnel tent in a storm. <<

With standard 1.1 silicone coated nylon the tear strength is roughly 30 lb/inch. . All though my memory maybe a bit off on this one. Plus its strength varies wildly depending upon coating etc. With .74 cuben it's about 65 lb/inch. Or roughly twice as much.

With silicone nylon the weakest point is where the panels are sewn together, ie the seams. With a properly designed CF tent, the weakest point is fabric panel, ie. the seams are stronger than the material itself.

There is the question of shock loading. One must wonder if the inherent stretch of silnylon is enough dissipate forces over twice it's static failure load.

While you can do lab test to mimic that kind of load, it only tells a partial story. The configuration of your pole structure can greatly affect how a tent will respond to wind loading and it's ability to dissipate forces.

In the end, the suitability of a fabric for a task depends upon a myriad of factors. Not simply a direct comparison of replacing one fabric with another.

[Roger Caffin]

Hi Ron

No, polyester fibre does not have as much stretch as nylon fibre, but polyester FABRIC does (usually) have enough stretch in practice – in my experience. Often the stretch you need is on the bias rather than square on anyhow, and most any woven fabric has stretch there.

> With silicone nylon the weakest point is where the panels are sewn together, ie the seams.
I agree.
That is why I have some very special seam construction on my tunnels. I put a lot of design work into that too: both seam design, stitch length and thread gauge. Field testing shows that the seam construction works very well, even When Things Go Wrong. The tent took a fair old hammering that night, and the seams, fabric and CF poles all came through without any damage at all. Pity about the Spectra guy ropes which died, but they were fretting against sharp Ti all night.

So it is possible to have really strong seams in silnylon, even if most Chinese manufacturing never bothers.

> There is the question of shock loading. One must wonder if the inherent stretch of
> silnylon is enough dissipate forces over twice it's static failure load.
Um – where do we get the figure of 'twice it's static failure load' from? I am not aware of any real test reports showing that sort of load on a real tent under real conditions. Yes, I have seen photos of shredded tents on the South Col of Everest, but those tents took the weather just fine when first pitched. It was many months later after lots and lots of UV degradation that they failed.

I have tested my snow stakes in the snow to see what sorts of forces they can withstand. The forces are not astronomical, far below anything that could cause damage to the fabric, but even so I have never seen any of my stakes show any sign of moving under load in the field. (Except for one time when the sun heated the stakes so much that the snow around them melted …) I normally use Ti wire stakes in the summer, and I have never had one of them pull out either. So I am not convinced that the tent fabric on a well designed tent is ever loaded near its limits.

To my mind, what really matters is the length of the unsupported fabric span. But, always happy to learn.

Cheers

You are losing my ability to follow you with all of this Roger…

I will reiterate my main concern: the lack of stretch

and then you say:

what really matters is the length of the unsupported fabric span

So, which is it?

What really is it that you think IS the issue that is the "main issue" or "what really matters".

Or, perhaps there is just a long laundry list of things you have against CF ;) Stop being a hater :-p

[Justin Baker]

I have an idea, someone should take a cuben fiber tarp, pitch it super taught off some rocks on some remote ridge in the high sierras during summer, then come back next summer after the tarp has survived a winter on an exposed ridge. Then we will know.

[Mole J]

nm

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