Cuben – The 422 mm hydrostatic head dirty little secret

[Richard Nisley]

Nick,

The short answer to your question is, "Yes". The long answer follows:

I test a low HH reading Cuben, followed by a high HH reading Cuben and then repeat the sequence and get the same readings. It seems illogical to me that calibration could possibly explain this phenomenon. If the calibration needed to be adjusted, all the reading would be higher or lower than they should be; different samples wouldn't vary by ~600% HH on a consistently repeatable basis.

MY commercial grade HH tester was manufactured and certified for accuracy May 2009. It was unused and wrapped in plastic until I un-wrapped it about 30 days ago.

Look at the one independent test done by Ziff and the battery of tests done by Lance Marshall. They both used different types of DIY HH test equipment but for each general fabric type tested and the results correlated. Significant calibration error using any of the methods wouldn't have resulted in the results being close.

My significant other is a molecular biology scientist who works in a research lab every day. I have had her independently duplicate my tests using Protocol B and my equipment. The test result differences have been in the noise level. They primarily arise from large sample surfaces where the test head is placed at different random locations by each person.

Mountain Laurel Designs owns a commercial HH tester and Ron has possession of the original sample that precipitated Protocol B. Contact him and ask him if he thinks the anomaly could be explained by equipment calibration.

A shipment of all the virgin samples from the beginning of Protocol B until those received by end of day this Friday are scheduled to be shipped to Roger on Saturday. After the transit time to Australia, contact Roger and ask him if he thinks the anomaly could be explained by equipment calibration.

[Richard Nisley]

I create micro graphs at 1024 x 768 resolutions. When I insert the images in my posts, they are automatically reduced to only 550 x 413 resolutions. Other than posting micrographs to an independent Web site and requiring that forum readers link to another site to see them, is there a way to insert forum images higher than 550 x 413 pixels?

[dan mchale]

Higher res would be good – whatever it takes to do that. Otherwise I'm not sure what value there is. Lighting could be improved also to provide more contrast.

[Alexey Pomortsev]

Hi everyone!

>At this point, I don't see any strong evidence indicating
>whether it's A or B, but testing on B should indicate
>whether B is true.

Dan, I guess cuben deterioration is rather stochastic process so HH data for different samples should vary. Meantime both "bad" samples has exactly the same (down to milimeters) HH values. Thus it seems variant "A" is more probable IMHO. Bad batch(s) made of substandard mylar film or something alike…

[Alexey Pomortsev]

>Keep in mind that each aging cycle is more than 8x the
>work of the initial test. There are some people
>understandably impatient for a quick anomaly resolution.

Richard, I'm the one of whose impatient :-) Was about to push the button and buy this unfortunate CT1K08 just before saw current topic… When are you going to make aging tests? Gonna wait for all samples to arrive to make "virgin" testing before?

[Richard Nisley]

Alexy,

Every new submission will have its initial test result published the day that it is received. This will occur regardless if the aging test cycles may have started for the first batch's submissions. We will stop accepting new submissions when we decide to end Protocol B batch aging tests (explained below).

My plan is to begin aging tests on all coated submissions (Cuben, silnylon, sil/PU nylon, and PU coated nylon/polyester) in multiple batches. All submissions received by this Saturday mid-day will be categorized as the first batch submissions. Before my local post office closes this Saturday, all virgin submissions received to date, will be shipped to Roger Caffin. The submission number, determined by the order received, followed by the letter (A) is labeled with a permanent marker in the upper left corner for each submission. These (A) sample submissions are the ones that I have posted virgin results for in the Protocol B thread.

I will begin aging tests for the submissions labeled (B) in the upper left corner will then be shipped to Roger via BPL Bozeman.

A new batch aging cycle will begin after the prior one ends. Additional batches will continue to be aged only until the point that Roger and I agree that enough data has been collected for any reasonable person to draw an informed conclusion; other commitments in our lives dictate that we suspend Protocol B testing; or some new protocol is required to resolve unanswered questions.

In parallel with the above heavy testing schedule, I will attempt to honor the requests for higher resolution micrographs and micrographs at more testing stages. I have begun to look at options to accomplish these requests. I will propose a new micrograph plan and provide sample results for review and discussion by the end of next week.

[Warren Greer]

OK Dan. Thanks for the clarification on that. Good to know what I'm looking at.

[dan mchale]

They can actually be seen with as little as 8x magnification – like with a photographers loupe. They are tiny at that mag though.

[William Zila]

I blame this thread for the headache I just got lol good read though

[Alexey Pomortsev]

Monday? Great! I guess one aging step (out of eight) a day?

[Richard Nisley]

Yes, one aging step will be reported for every coated sample in that batch each day. If a significant variance occurs during aging, then a high resolution micrographic will highlight the problem. The high resolution micrographs will be hosted on another site to bypass the photo size restrictions on the BPL site.

[Hamish McHamish]

Others said:

"My biggest concern is whether the material wears down over time."

"My interest now is in durability – the low weight is amazing but so is the cost. To justify the latter the tent needs to be last."

This is what matters to me on the cuben issue. I simply can't justify cuben's cost if it is going to deteriorate inordinately through reasonable field use. What is "inordinate"? I can't quantify that, but my OWare silnylon tarp is chugging along fine after years of faithful service. If a cuben tarp is going to shat the bed after a year or two of use with reasonable care, it ain't worth the weight savings to me.

Edited to add:

Here's a small download from Cubic Tech that lists the individual part numbers and (some) specs for their CTF3 line:

http://www.cubictechnology.com/CTF3%20PRODUCT%20INFO%20PACK%2007192010_4c.pdf

[Richard Mock]

disregard

[Roleigh Martin]

I'd like to see this thread re-opened with 2014 data. Anything new to add to this thread? Among items I'd like to see if anyone has seen their cuben fiber tents, now that they're a couple of years old, fail in the field due to prolonged high-intensity rain. Please indicate the thickness of your CTF3 fabric when posting.

I had great success with a new Zpacks Triplex tent with their optional extra-thick .74 oz CTF3 fabric this year, it was the wettest JMT hike I've done in 7 straight years; on August 3, it rained for 12 hours straight, hard. The tent held up fantastically well.

Thanks in advance.

[Roleigh Martin]

In 2017 the bottom of my Zpacks Triplex tent suffered water penetration from the bottom in a very severe rain storm (at least that is my observation, I have nothing scientific to prove such).  It (the floor) is 1.0 oz CF.  I have a choice of having Bear Paw Wilderness Designs (bearpawwd.com) replace my tent floor with either 1.25 oz or 70D (2.3 oz) Silnylon.  The owner of Bear Paw says either is significantly better than 1.0 oz CF but did not specifically pick either as being superior to the other.   What are the opinions of people here?  Thanks in advance.

 

[Hoosier T]

1. I’ve never felt that cuben is the most suitable material for a floor.
2. I would stray away from Bearpaw as there have been numerous horror stories as of late involving their quality and customer service. Also, they don’t exactly use the latest and greatest in materials other than offering cuben.
3. Have you contacted Zpacks to see if they can do anything for you?
4. 1.1 Silpoly PU4000 is a very nice material for shelter floors.

[Roleigh Martin]

Thanks Hoosier.  I’ve done business with Bearpaw before and was satisfied.  Zpacks does not offer silnylon fabric so the best I could so with them if they did anything would be to replace the floor with a thicker CF fabric.  However, I should email Joe V first to give them first opportunity.  Good idea.  Thanks!

[two pints]

I always use a polycryo ground cloth with my silnylon tent floors.  If the ground is wet when I put up my tent, I notice that groundwater comes through the silnylon floor anywhere I put pressure (i.e. knees, butt, sleeping pad, etc).  The groundcloth keeps this from happening.

I personally would steer away from a silnylon floor if I was planning on using it without a ground cloth.

Is the floor on your Zpacks so far gone that it absolutely must be replaced?  Or could you get by with just using a polycryo ground cloth under your Triplex?

[Sam Farrington]

“What are the opinions of people here?”

Your inquiry is about the failure of Cuben Fiber, so I guess it falls within the general scope set by the OP in his controversial expose.

It should be said that silnylon is not necessarily a bad choice for a tent floor.  And I think the choices you were given by Bearpaw were heavier than is necessary.

Ripstop by the Roll now offers a “Mountain” silnylon, touted at over 3000 mm HH, and higher tear strength.  With the slicone coating, both sides, it is spec’d at 1.3 oz/sq/yard.  Much lighter than what you are considering.  If it performs to specifications, it is more water resistant than the excellent silnylon from Lightheart Gear of the same weight used for the floor of a remodeled One Planet Goondie that has never leaked a drop, despite its heavy occupant (me) and his two dogs:  https://backpackinglight.com/forums/topic/81307/   An earlier silnylon floor, used to replace a polyurethane floor on an Australian Bug Dome, was made of silnylon of similar weight from Thru-Hiker, and never leaked either.  Note that all these silnylons were not the newer type, coated with various combinations of silicone and polyurethane, and which may or may not be better, depending on the quality of the coating and application.

Silnylon also has other advantages:  It’s smooth surface and stretchiness make it very resistant to abrasion and puncturing by objects under the tent, and since it is not being used for a taut canopy, its greatest weakness, sag, is not a detriment.  I’ve found that a chevron pattern of silicone sealer on the bottom of the sleeping pad prevents sliding, although some others are not satisfied.  For them, the nylons coated on one side with polyurethane are a good fix, although the tent design must stretch the floor at its corners to keep it from floating about.  With such a design, choosing a tent site on level ground keeps me and he dogs from sliding around.

There is an awful lot of lesser quality silnylon sold, both in terms of the nylon and its coatings, and even the larger companies seldom approach 3000 mm HH with their tent fabrics, so there are many horror tales that give silnylon a bad name.

A big issue is your not being an MYOGer, and thus limited to less choices fabric-wise.  But you might contact Rainy Pass Repairs, Inc., which has been repairing gear for many years, to see about replacing your cuben tent floor.  You’ll have a much lighter and more packable tent to boot.

[JCH]

How old/how many nights do you have on your triplex?  If it is a “high milage” shelter I might consider it well used and seriously consider allowing Zpacks to replace the floor like for like.  Or, if you really want something more burly than the stock 1.0 cuben, the 1.43 cuben would make a bomber floor albeit at a weight penalty.  The Zpacks bear bag is made of 1.43 and it is one tough little bugger.

[J-L]

If you decide to go non-cuben fiber, I would also recommend the SilPoly PU4000 over silnylon. The waterproof rating on this fabric is very high and has been independently tested by Richard Nisley. The material is more puncture resistant than silnylon, and the PU coating means less sliding around. I have used it as the floor on my MYOG tent with good success.

For reference, here’s the thread with PU4000 test results: https://backpackinglight.com/forums/topic/105800/

[James Marco]

I would avoid any PU coated materials on a floor. I never use a ground cloth under my tents and get occasional leaks. When these happen, I simply use a slury of mineral spirits and silicone caulk on the floor and reseal it after a couple years. Any tears, punctures and holes can be repaired with the appropriate sized patch glued in place with the 100% silicone caulk. Never had a problem that required a full floor replacement with any silnylon. Two of my tents are used for car camping before/after a hiking trip and are well over 15-18 years old (pre-cuben.) The floors of both have been patched/resealed two or three times and don’t leak.

[Matt Swider]

Just curious the magnitude of the failure being described by Roleigh? Based on the two posts in this thread the tent could have seen 4 summers of use.  I know as some point Cuben just starts sort of falling apart, maybe that is what is happening with your floor.  The dumb question is, have you considered a bit of cuben tape to repair it?

I can’t resist a bit of thread drift, but I had my solplex set up in a very poor location and ended up in a 2″ puddle, absolutely no issues with water intrusion into my tent.

[Sam Farrington]

John H., Re: “The material is more puncture resistant than silnylon, …”

Am guessing that you are referring to the post on the link about pushing pins through polyester and nylon fabrics.  With the advent of RBTR, there has been considerable debate on BPL about whether polyester fabrics are stronger than nylon.  This has been generated by the same one or two folks. However, I believe that as a general rule, nylon is a much stronger material, weight and coatings being equal.

It is Roger Caffin’s example of an elbow being pushed into a tent floor on soft and wet ground (or snow)  that i think illustrates the issue for most of us.  Polyesters are almost infinite in number, whereas with nylon, we are usually talking about Dupont 6,6.  So for the polyesters, and for cheaper nylons,  I don’t think that generalizations about strength are helpful here.  More scientific tests of specific fabrics such as Richard conducts are helpful if the specific fabrics are available.  It is the elasticity of nylon, especially silcoated, that deters puncturing and abrasion, not by pins, but by less sharp objects under the tent floor.  And the demonstrations on RBTR with puncturing and tearing the Mountain Silnylon are persuasive, and illustrate greater strength than any polyester of similar weight that I’ve seen.

Suggest not throwing silnylon under the bus just yet.  As my former boss used to say, ‘Be careful what you wish for.’

 

[Geoff Caplan]

Well, to continue the thread drift, I’ve posted elsewhere that I had some communication with one of the top freelance designers of lightweight tents – with decades in the business and access to the labs and repair shops of most of the big US brands,

In his opinion, the superior strength of silnylon vs poly in the lab is soon overtaken by the superior UV resistance of poly in the field, as sil quickly loses its advantage as it degrades.

He also points out that outside of extreme usage it’s a non-argument, as with proper design, seams and reinforcement the fabric is not a significant point of failure unless it’s punctured, and that both have very poor puncture resistance.

So in practice, either is plenty strong enough for normal usage. He uses poly on his own range, because of its resistance to stretching when wet, which he regards as a much more important performance issue.

[Author]

Posts