Cuben fiber-sewn/taped versus bonded

[Robert Alexander]

So I am getting down to making a decision about a 2-3 person shelter purchase (probably a mid) and some manufacturers' fabrication methods leave me with questions.

-One company says it sews and tapes the seams. They go on to say that seam sealing is not necessary as the seams are taped.

-One company says that it sews and tapes the seams for strength, but seam sealing is still necessary.

-One company says that it does not sew the seams but instead bonds them. Therefore there are no seams to seal.

Does anyone have any experience with the above methods or products and be willing to leave a comment on them? I've read that bonding is preferable since it does not puncture the material but the companies listed above enjoy very good reputations.

The only thing I may add is that the bonding process that I've seen on YouTube seems fairly intense but saving a couple ounces on seam sealer (plus my own labor) would seem worth the extra production labor cost. In addition, if it's truly stronger due to the lack of punctures then it will be hard for me to consider anything other than bonded.

I thought I'd leave out specific manufacturers at this point but I'm not against going into greater detail to provide citations.

Note to moderators: I thought I'd post this in the Gear Forum but please move to the MYOG forum if it's more relevant there.

[Link .]

Making a 2-man Cuben Fiber Tent

4 person family Tent

myog mountaineering cuben tunnel tent

[James Marco]

Actually, the best way to attach cuben together is to use both sewing AND bonding.
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=58096&disable_pagination=1
See The Nick Bedouin postings there.

[Robert Alexander]

Brilliant thread!! Thank you. Since it's been a few years maybe there's been some additional revelations so I hope that if anyone has more to share then please do.

[James Marco]

With Cuben, I have always been a long standing fan of the bonding methode. As a carpenter/cabinetmaker you kind'a learn to trust adhesives. But, Nick was from North Sails. He obviously knew his stuff, much more than me.

As far as I know, the adhesives are still known to creep under long term stress. There was a note from another long term member about a couple bag failures due to creep. To my poor knowledge, they have not changed the adhesives with either tape or used for bonding. The threads will lock the material together, reinforcing the bonding methode. Near 100% of the fabric strength was noted. But, threads require some sort of sealing. I don't think you can do one without the other on a tent.

[Robert Alexander]

Thanks again to Link and James Marco.

Wondering out loud if it's preferable to tape the outside of the fabric, the inside, or both? The shelter I am consider weighs a mere 16 ounces so I am not against applying some additional tape myself in order to reinforce the seam. Ultimately, I will ask the manufacturer what they advise.

[Ryan Smith]

"I've read that bonding is preferable since it does not puncture the material but the companies listed above enjoy very good reputations."

I think it really boils down to there is more than one way to skin a cat. Both methods are sufficiently strong which is why the companies your looking at have very good reputations. Buy with confidence.

As far as which is stronger bonding or sewing/taping, it really depends on what part of the shelter your talking about. I would be completely happy bonding a ridgeline, but I don't feel comfortable using only tape in the tie outs(although some people have had success with that method).

Ryan

[Lawson Kline]

If your dead set on Cuben. I would buy a shelter from one that bonds and sews as bonding alone with a roll adhesive like a 3M 9485PC will come apart in cold weather. I don't care what marketing hype they spin. I have the test reports to prove them wrong.

I posted about this a little over a year back. Here is the link. http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=89474&skip_to_post=772142#772142

Here is the post as it related to cuben mountaineering tents.

"The reason you don't see more cuben mountaineering tents is because of the construction techniques that would have to be used.. The shelter would have to be both bonded and sewn as bonding alone doesn't work in cold weather. The adhesive looses all its strength and the shelter will just fall apart.

I had a problem with my drybags in cold weather. People were stuffing their down bags in them and then going out in cold weather mountaineering, snow shoeing, skiing, hunting, etc and the seams were failing. The down bag would literately push the seam apart… So I paid 3M to test the problem. Well they found that ALL roll adhesives loose about 50%- 90% of their bond strength at 0F. Put it this way. 9485PC which is the adhesive that Cubic Tech use to recommend before selling their own, and most likely the adhesive most companies are still using has a T-Peel bond strength of 90.4oz/in at room temp and 12.5oz/in at 0F..

So the problem can be fixed by sewing the seams after bonding, BUT then your sewing through a non-woven material which creates a whole set of new problems."

[Anonymous]

Very interesting and potentially pertinent stuff Lawson, thank you for sharing it.

[Robert Alexander]

To Lawson Kline: Holy moly-this is exactly what I had hoped I'd find-some fairly recent discussion. I'm going to have to digest the thread over several hours. My father, an engineer, always warned me about adhesives that "don't hold in the cold." Thank you for the link and advisory.

[Link .]

1 article I linked is from 2015 and the mountaineering tent thread started in 2014 and is still under discussion in 2015 if you read it.

[Robert Alexander]

Link: had actually read (in awe) through many posts of the thread before, but more out of curiosity. I should probably read more of it since I gathered that the thread was less about merits of various construction methods and more about how to make a tent. Not off topic by any means but less focused on what I'm looking to compare. At any rate, the links are appreciated.

[Ryan Smith]

"If your dead set on Cuben. I would buy a shelter from one that bonds and sews as bonding alone with a roll adhesive like a 3M 9485PC will come apart in cold weather. I don't care what marketing hype they spin. I have the test reports to prove them wrong."

Hi Lawson,

The cold affecting the tape makes total sense and the reports from 3M back it up, however we never hear of it happening in the field. Are the forces at work a little different in nature than the dry bag example(wind vs mechanical force) and they're also getting spread out along several feet of seams? Thoughts? With a few thousand bonded shelters out there I would have it would have come up at some point. Granted, there are much fewer people out at 0F for this issue to occur so the sample size is smaller.

Thanks for always passing along the knowledge you acquire. Always interesting and helpful.

Ryan

[J-L]

I think most seams in a shelter would be under a shear load. Even if the peel force of the glue is substantially reduced, it may still be plenty strong in shear. Kind of like how velcro can peel apart, but is strong in shear. Were the 3M tests just measuring the peel strength?

Or maybe bonded cuben shelters are simply held together by hopes and dreams.

[Ryan Smith]

The dry bags coming apart would indicate shear strength is also reduced. Yes? They would pull apart due to forces in shear if the sleeping bag was pressing out from the inside, not peel.

I could also buy the hopes and dreams argument. You get a lot for your money with cuben!

Ryan

[J-L]

Yea, there will be a reduction in shear strength when the peel strength is reduced. I guess I phrased my post wrong. It should read: "Even if the peel force of the glue is substantially reduced, it may still be strong enough in shear…for a shelter".

Stuffing a big winter sleeping bag into a cuben dry bag may be too much force for the bonded seams to handle, especially if there is no place for air to escape. Repeated stuffing and stressing would gradually break the glue bonds, eventually leading to failure.

I do imagine a winter storm being an inconvenient time for your shelter's seams to start coming apart.

[James Marco]

I believe you will find the adhesion force on the tape will be significantly reduced, per Lawson's and 3M's reports. These tests are usually done in shear mode. Peel mode is usually weaker unless the bonding is 100% or better than the substrate strength. In which case it wouldn't really matter because bonding would be as strong as the fabric in any mode.

Note that cuben is, basically two parts (maybe more, depending on the type.)
1) A loose mesh of spectra, dyneema, and/or carbon fibers.
2) A plastic interstitial barrier between them.

So any stress will likely concentrate on the threads because the plastic will stretch and the fibers do not. This is rather unfortunate, because the stretch characteristics of the two materials are different, giving different failure rates and pressures. A total stress application is one number, holding it for 24 hours will give another number much weaker than the first as it fails in stages. Temperature apparently effects the stickiness of the adhesive.

I would speculate that cold apparently turns it more and more like a solid. This causes the adhesive to loose it's stickiness. Like frozen duct tape is much easier to pull off than warm duct tape. Cold enough and it is just another layer that does not bond at all (it actually gets fairly stiff at -20F, but this might be due to the plastic coatings.)

[J-L]

Lawson stated the tests were T-peel (so not in shear).

[Clifford Deakyne]

Having run many tests like this, the shear test shown above will have failure initiated in peel at the free ends. Thus reduced peel strength will result in a reduced shear strength. If low temperature performance is needed for a tent, there are other adhesives with much better low temp performance, likely at the cost of the RT performance. Getting it in an easy to use roll form may be an issue.

Cliff

[Anonymous]

"Or maybe bonded cuben shelters are simply held together by hopes and dreams."

My sense from reading this site is that not a lot of people go out into single digit temps nor especially below O*F.

So for a lot of people here, it's mostly a non issue. But still good info for those whom do to know.

[[ Drew ]]

"Note that cuben is, basically two parts (maybe more, depending on the type.)
1) A loose mesh of spectra, dyneema, and/or carbon fibers.
2) A plastic interstitial barrier between them."

Regarding (2) above, I thought it was plastic/Mylar sandwiching the fibers as oppressed to a plastic/Mylar barrier between the fibers . However the interstitial barrier is unclear to me…?

[James Marco]

Drew, Yes, it starts as two sheets with a core of fibers. Through pressure and heat over and under the mesh, it becomes one piece, usually partially melting in to each other…a true mechanical bond. This is basically running in between the squares created by the woven fibers. The interstitial barrier is simply that area, creating the overall waterproof sheet. No adhesives are used.

Here is another description from HMG: https://www.hyperlitemountaingear.com/technology
From Cubic Tech:http://www.cubictechnology.com/technology.htm

A more general article from http://indefinitelywild.gizmodo.com/how-the-lightest-strongest-outdoors-fabric-is-designed-1601176186

Enjoy!

[Art Tyszka]

Not scientific at all, and a lot of you guys have a ton of knowledge on this (impressive). All I'd ask (maybe point out) is has anyone ever seen a report of a bonded Duomid or Trailstar seam coming apart? I have not.

[James Marco]

"… seen a report of a bonded Duomid or Trailstar seam coming apart?"
Nope. I worry too much. Like I say, I really like bonding. But, the reports I have seen seem to indicate a severe degradation over time and/or temperature. And, this is NOT what North Sails, (now Dyneema?) recommended. They like using both.

[J-L]

I have not read any reports of bonded cuben shelters coming apart. Given that Justin Lichter and Shawn Forry used a cuben MLD DuoMid (which uses bonded-only ridgeline seams) on their winter PCT thru hike, it is probably not an issue in reality for most users. Which is all the more interesting given Lawson's test data which suggests that it could be.

However, I have also not read of any failures of sewn-then-taped cuben shelters. The sewn-then-taped ridgeline on my ZPacks tarp seems plenty strong. I have only read about issues with sewn-only cuben.

So for the OP, I would go with sewn-then-bonded or bonded only – whichever design you like best.

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