I just finished testing a few different ways to bond the reinforcement patch on the corners of cuben fiber tarps. All the methods, even just plain old sewing, took a substantial amount of weight before failure. And, the difference in max load between a sewn corner and a bonded corner was only a 20%. Much smaller gap than I thought.

So, now I am curious. Has anyone had a cuben tarp tieout fail? Or any cuben failures out there? I have several cuben shelters and none have failed in the field.

Edited by Steve_Evans on 09/22/2010 17:25:35 MDT.

Steven,
Your question was asked Here.

And James Patsalides's Survey Results are Here.

I can't tell how that survey distinguished between a tarp being damaged by a falling pine cone, a wind induced failure at a tie out, or by packing it in a bag with broken glass.

Steve,
I believe your question is different, and deserves this thread.

I would also like to see the cuben fiber weights listed, conditions surrounding the failure, and if the failure occured at a seam and if it was a bonded or sewn seam.

I believe it would also be relevant if users of cuben fiber tarps, that have not experienced a failure, but have seen a noticeable "stressing" of an attachment point would also post their comments.

Thanks

I remember that survey - I actually took it and claimed my tarp had been damaged but it was from wood debris when I broke a big stick and it flew into my duomid. It was good to read through again though, so thanks for links. I guess I was curious about tarps failing due to weather conditions/field use etc., as it seems cuben fiber has a name of being fragile in the backpacking world. Even BPL states it in their tarp description.

From BPL site:
"Cuben Fiber....often associated with the stigma of poor strength resulting from sewn seams along the ridgeline, edges, and guyline tie-out reinforcements."

I always seem to be convincing people that cuben is strong enough for their needs, yet I know of only one person who has actually had their cuben tarp fail.

Anyway, I was curious so did some tieout tests. It's documented on my website, so feel free to read if you like.

Link below:
Testing Various Corner Tieouts For Use On Cuben Fiber Tarps

If I come across any other methods, I'll add it to the results.

Edited by Steve_Evans on 09/22/2010 22:06:22 MDT.

I had a failure due to wind on my SMD Refuge-X. It was clearly a design flaw as the guy-out was just sewn on a straight line with no reinforcment.

Nice work Steve. I read your report. Great stuff!

I have had a sewn corner tie out experience some damage but it was still pretty far away from 'failing'. I'll see if I can explain this clearly. In this instance, a nylon reinforcement patch was sewn to the corner of the cuben by sewing along just the perimeter of the nylon patch. The guyout was then sewn at the corner through both the nylon and cuben. This design led to damage of the cuben because the nylon has some stretch to it. When a force was applied to the corner, the nylon would stretch and thus leave the non-stretchy cuben to bear the brunt of the force. In effect, the cuben wasn't really reinforced because the nylon was only sewn around the perimeter and it was able to stretch and leave the cuben to bare the force.

As a result, the cuben started tearing where the guyout was sewn. However, since the guyout was also sewn through the nylon, once the cuben had somewhat failed the nylon was then left to bare the brunt of the force. The nylon would then stretch and disperse the force between all the stitches along it's perimeter which seemed to be working. I also don't know for sure, but the cuben seemed to be CT1K.08 rather than CT2K.08. The manufacturer claimed 0.6oz cuben but having used CT2K.08, I would say this was a lighter weight.

Regarding Lynn's failure, I have a photo of this spot:



In the initial design the guyout was attached to the loop of nylon at the bottom. Since the guyout pulls somewhat perpendicularly to the cuben, this put the stress on only a few stitches at the bottom leading to Lynn's failure. After reading about Lynn's failure I used a needle to re-route the guyline through the nylon as shown. I believe this method disperses the force over a much larger number of stiches and thus is less likely to fail.

Regarding your tests Steve, I would say that the sewn method is more prone to experience gradual failure than the other methods. While the sewing failed suddenly in your trial, I believe it can experience stress under normal use and the stitching holes can gradually enlarge and slowly bring it closer and closer to failing. I don't think this 'gradual fail' is really a possibility with the bonding methods.

It seems to me the results of your tests show that if you want a stronger corner, instead of sweating about what method to use, the best method is to use a larger reinforcement patch. Since the samples normally failed along the edge of the reinforcement, using a larger reinforcement would spread the forces over a larger area of the cuben.

Edited by dandydan on 09/23/2010 15:16:11 MDT.

Nice work on the comparison of tie-outs, thanks for sharing the info.

I read somewhere that you can use contact cement to bond cuben. Is this correct, have you tested it by chance.

Thanks

Lawson mentioned contact cement in a cuben thread (MYOG section - Tensometer thread?) a month or two back. I picked up some contact cement and it performed terribly so Lawson must have been using something different that I was using. I went to my local hardware store and grabbed a normal looking tube of contact cement...not sure what brand. I think I tossed it because the bond was virtually nil.

> if you want a stronger corner ... instead of sweating about what method to use,
> the best method is to use a larger reinforcement patch.

Right on.

Cheers

Dan Dursten, you just saved me from myself!! I'm in the process of planning a DIY cuben tarp and was going to use nylon to re-enforce the tie-outs. Your explanation of the problems caused by the differential stretch of cuben vs nylon makes a lot of sense to me. I'm now going to use multiple layers of cuben for the re-enforcements.

Thank you very much, Dan!

Lynn,
I read about your failure. I also have a Refuge X and can tell that is a weak point. Mine has some odd striped tape on the inside of it.

Dan,
Thanks for the info. I totally agree that the bonding is stronger than sewing. I also agree the bonding will probably not see the gradual failure you mention. You actually summed it up very nicely at the end of your post. The larger reinforcement patch is really the key.

Chris,
I tried the contact cement right after Lawson mentioned it in the other thread. Mine worked out pretty good, but not as well as some of the other methods. I used the contact cement on the yellow shelter in my avatar. It is really quick and easy to use. But it has very little strength when in peel. I was a bit confused with it. When I tested it in peel, it appears as though it delaminates the cuben, but I'm not certain as the force required is so low. I can pull it apart by hand fairly easily. It just doesn't make sense but I have no other info or tests to explain why it acts like this.

I think we have learned alot about cuben recently. Looking forward to the upcoming article on bonding methods and testing.

Nice work Steve.

The reason contact cement causes delamination is because it creates a mylar to mylar bond that is stronger then the mylar to dyneema bond. Technically a bond that causes delamination is the strongest bond you could possibly achieve. Try testing contact cement in lap sheer mode since cuben should never be bonded in T peel mode.

Edited by Mountainfitter on 09/28/2010 22:24:39 MDT.

Good call. Cuben really shouldn't be bonded in peel, I usually just use my hands for those tests to give me an idea of how strong it is.

I'm doing a couple of other tests using the lightest cuben material. My N2 Tarp really is stronger than you think and I want to get an idea for what the tieouts can handle. I'll try contact cement this time around to put some numbers to it.

Edit: Having read the posts, I now realize that I have been spelling re-enforcement as reinforcement in the document...my apologies, my spellcheck didn't pick it up :)

Edited by Steve_Evans on 09/29/2010 13:42:50 MDT.

Where do you find the 3M 9485PC tape or the venture tape 1163MS74 in retail quantities? I haven't been able to find a source.

Edited by joshualee101 on 10/03/2010 16:31:20 MDT.

I get the Venture tape right from the manufacturer, but the 3M product is from a local industrial supplier up here in Canada called Fastenal. I think you guys down south can get it from McMaster Carr though.

Steve,
maybe I'm missing this information on your write-up of the tie-out test, but what width tapes were you using to bond the re-enforcement patch to the tarp? Was it a 1/2" bond along the top edge of the patch or was the entire re-enforcement patch bonded to the tarp?

Edited by joshualee101 on 10/03/2010 16:39:18 MDT.

Joshua,
I bonded the entire patch using the adhesive or in the case of the tape, using strips of it. I have seen several shelters on the market that just use a strip along the top like you mention. I think that would be fine as the failure is typically in the parent material, but I didn't test it that way. I think as long as you sew your grosgrain through the adhesive, it "should" act the same, but I'm wrong all the time. :)