May 3, 2012 at 8:53 am #1289493
@troutLocale: Long Beach
My cuben sheet has edges without fibers in them (normal from what I gather). I was wondering, do I need to cut those off? They're probably like 1.5" on one side, .5" on the other, for reference. I was thinking of folding the short one under, as like "eaten by the hem" material. Is the rule just that nothing structural should be attached to the fiber-less part, in which case having it be the only thing hemmed under be fine?
There are also normal cuben edges on a project I'm doing that I'm thinking of putting cuben one sided tape (zpacks) on to stop from fraying, is that an okay way to do this, or should I hem? How does that tape hold up compared to hems?
Thanks! I'm new! I don't know what to do!May 3, 2012 at 10:39 am #1873977
If there isn't any dyneema in the edges you can either cut it off or fold it over on to where the normal fabric is.May 3, 2012 at 10:42 am #1873979
i suppose it depends on what you're making. in my case, currently working on a tarp- so i'm looking to reinforcing the edges for strength. i'm hemming with d.sided adheasive. but if no load is the use and you don't mind the utreated edgegs leaving them would work just fine. ( i might add that i don't know if unsealed edges would absorb rain water or not) personally i feel it's pointless to carry the unuseable edgging that contributes nothing to the cuben's strength.May 3, 2012 at 12:13 pm #1874013
Colin KrusorBPL Member
@ckrusorLocale: Northwest US
I always cut off the excess film at the edges with a hot knife and then fold the new edges over and bond them down. Most of the load on a cuben panel is borne by the whitish dyneema fibers inside the laminate, but the integrity of the outer layers of film is important, too. I soaked a bit of cuben in a methanol/NaOH solution once, to create some microscopic pitting and fissures in the film, and it was much weaker. Mylar film has a property that is familiar to anyone who has torn a space blanket: a tiny nick can initiate a tear that can zip through the material under almost no load. Along the edge of the film on a cuben panel are millions of microtears that can propagate under load. A BPL poster with access to an Instron tensometer confirmed that you can dramatically increase the tensile strength of a strip of cuben by folding the edges over, to reduce the load at the microtear-riddled edges. This evidence also supports bonding or taping as opposed to sewing cuben, because sewing creates a line of jagged punctures (edges) which weaken the film.
So, I'd recommend cutting off the excess film, folding the edge over, and taping or bonding it down.May 3, 2012 at 5:21 pm #1874133
@troutLocale: Long Beach
That was beautifully helpful, thanks! This current project is a rain kilt so I'm not too worried about tension being applied en force but that's great to know for future projects.
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