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Cuben Fiber

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---Originally developed as a lightweight sail material for boat racing, Cuben Fiber is constructed by laminating plasma treated Ultra High Molecular Weight Polyethylene (UHMWPE) fibers and monofilament polyester film. Cuben Fiber has several characteristics that make it of high interest to lightweight backpackers. It is extremely light, waterproof, resistant to ultraviolet light, has high shear strength, and is more durable than many fabrics that are much heavier. Cuben Fiber fabrics can weigh as little as 0.3 ounces per square yard, or even slightly less.

Contents

Construction

Use in Ultralight Gear

Tests of the tensile strength of cuben to cuben glued seams

here is a photo of the test rig

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here is a closeup. The test piece is a control it is not glued it is 3" x 1" with the edges folded to the middle 

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here is a side view 

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I have completed my tensile tests of cuben to cuben glued with hysol U09fl, Aquaseal and Aquaseal 4 parts cotol 240 1 part. All glued at room temperature for 44 hours. They will have to be repeated because the glue was stronger than the cuben. I tested the hysol first. I tried hard to get the clamps of my set up all even so that the 25mm glued square was evenly stressed . I loaded slowly with sand in the bucket over about 10 minutes and failure happened at 27.5 kilo. Failure was along the bottom edge of the top wooden square clamp washers. I had rounded the edge of these. The glued area was intact. I tried the Aquaseal and on reaching 29.5 kilo I stopped, without failure. Similarly the Aquaseal plus Cotol took 29.5 kilo without failure. Looking up the 25 gram per metre breen cuben on the cubic tech website it should take 105 pounds per inch. It in fact took 60.5 pounds over an inch width of test 58% of optimum. I am pretty sure the spectra threads broke one after another from the sound they made. So I must have loaded the sample more heavily on one edge. The hysol data sheet I saw gave lapshear strength of from one to 12.5 Newtons per sq.mm (1.5 nylon, 10 polycarbonate). The hysol glue on the sample survived 27.5 kilogram force= 270 Newtons over 25 x 25 mm . That is 0.43 Newtons per sq.mm. I tried a peel test just by pulling with my fingers. I thought the hysol was best and the aquaseal plus Cotol was worst . With The Aquaseal the glue failed not the fabric. With the hysol, first the glue failed then the fabric failed between the 2 spectra plys.


NEW TESTS I tested these with a 6mm overlap on a 25mm wide testpiece.With 2 day old samples glued under weights at 15 to 20 degree C. Aquaseal took 13 kilo Aquaseal plus Cotol took 13.5 kilo. These amount to 0.88 KNewton per sq mm. Hysol the first sample failed at 9 kilo by pulling the glue area off the vertical specra threads. I was not happy with this test as it failed as I knocked the bucket while adding sand and caused rotation which twisted the sample so I repeated it, this time the hysol was 4 day old glued under weights at similar temperatures. It failed at 8 kilo by failure of the glue with no damage to the fabric. I wonder if I am not mixing the 2 parts well enough because the glue still seemed tacky. The instruction is: mix equal amounts for 15 seconds after the colour is uniform. My 2 parts were pretty equal although one part is more liquid than the other, both are transparent so I do not get a colour change but I perhaps did not mix long enough. THIS IS CONFIRMED SEE BELOW. I also tested a new control sample. I cut a 75mm x 25mm cuben piece and folded the edges to the middle to make 75 x 13mm. I tested that and it took 32.5 Kilo which is 68% of the Cubic tech datasheet shear stregth of 105 pounds per inch. Folding the edges does spread the asymmetric load of my testing. If I was starting again I would test all samples like this.

I tested 3 more samples Evostick timebond a contact adhesive which allows a bit of slip adjustment. I had bit more overlap than designed. Allowing for this it failed at one glue/ cuben surface damging about 1/4 of the cuben face at one edge, at 9 kilo. that is 0.59 Kilo Newtons per sq. mm. There seems no advantage in using this glue with cuben, unless it is what you have. It is adequate just allow an inch of seam with 25 gram cuben.

I tested another sample of hysol U 09fl and this one was not at all tacky. I therefore believe that I did not mix the 2 parts well enough in some previous tests. The test remnants of the last tests are still tacky. This hysol sample took 24.5 kilo. This is 1.6 Kilo Newtons per sq.mm. This is in the range Loctite show. The failure was totally in the cuben from one edge of the glue area away from the glue area. With this cuben 12mm 1/2" seam width of hysol is enough if properly mixed.

I tested a 1" sample of the main seam bond I intend to use on my tarp tent. 6 stitch per inch sewn once outside to outside then opened up and a glue seam of 20mm glued down with Aquaseal. This took 31.5 kilo which is 66% of the cubic tech figure. The failure was away from the glue area following the stitches for half the distance then wandering away from the glue to the edge of the wooden clamp washer. As plain unglued samples in the same rig took only one kilo more it appears that long stitches do cause a stress concentration but not a very debilitating one. It is probable that the sewing needle never breaks a spectra thread.

I intend to use Aquaseal rather than hysol for the long seams of my tent, although hysol is better, it is more expensive and hard to get in Britain. I intend to sew the seams at least once for location anyway and it is simpler to add another 6-8mm of seam width than use the expensive glue. Apparently silnet is recommended to glue cuben. For completeness I will test a sample sometime. It is not a priority for me though, if I need to attach cuben to a silnylon ground sheet I will need to know.

INTERIM CONCLUSIONS Error my bathroom scales only measure in half kilo. my measurement of glue overlap and sample width must be +/- half a mm. total +/-12%. Testing small raw edge samples seems to weaken the cuben by maybe 40%. So I cannot tell between Aquaseal and Aquaseal plus Cotol. Hysol is stronger than Aquaseal but has to be mixed correctly and well. If you treble the 6mm glue line I used with Aquaseal or double it with hysol you should get up to the strength of the unglued 25 gram /sqm cuben I was trialling. With Aquaseal I recommend 3/4" 18mm of glue minimum for say a ridgeline of CT.2K.08 25 gram /sq.mm cuben. By extrapolation the CT.1K.08 cuben at 68 pounds /inch could be ok at 1/2" 12mm and the CT0.3K.08 at 35 pounds might be OK at 6mm but it would be just as easy to go for 1/2" To put the trial in perpective if you used a 6mm glue width aquaseal sample of 1" wide cuben to try and pull a tent peg out of the ground, at 13 kilo of pull the tent peg would mostly go first. The ultimate strength 25 gram/sq.m cuben tarp would need very big pegs. --Derekoak 14:10, 27 January 2010 (UTC)


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This page was last modified 09:58, 28 January 2010.