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  1. #1
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    cuben characteristics

    i've been trying to figure out how to join two peices of cuben to create a cat shape on a tarp ridge line. pretty much unuccessfull so far, i might add. anyway, last night it occured to me that i might be trying to use the mat'l in the wrong way. and since i don't have any cuben on hand to help assess this, i have to ask here. the cuben has dynel strands running at 90degrees to each other as renforcing. this should resist stretching very well...but what about streching in a 45 degree direction? ( on the bias?)- is there much give in that direction? if so, it might be a simple reorentation of the cuben to allow the stretch to work for me, to create a cat shape on the ridge. i figure it would require about another yard or two of matl to do. that is unless if it's available with strands already at 45 degrees to the factory edges.( fat chance of that!)- might be very intersting to experiment with.

  2. #2
    Senior Member SGT Rock's Avatar
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    I haven't tried to ever measure stretch in any one direction, but my general experience is it won't stretch in any direction. Someone might prove me wrong by showing it will stretch 1% more to the bias, but I don't know if I would count that.
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  3. #3
    WV's Avatar
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    I agree with Sgt. Rock. The laminate is polyester, so it doesn't stretch the way nylon would, but the thing that limits diagonal stretch the most is the fact that the dyneema fibers are held in place by the outer layers - they can't slide past each other the way fibers in a woven fabric would.

    Making a cat cut ridgeline is probably very tricky. I haven't attempted it because I don't think it's necessary. Getting "an extra yard or two" is going to cost you another $50. I suggest a plain ridge seam for the tarp with a ridgeline below the tarp as part of your suspension.

    You're asking interesting questions, which shows that you're thinking. Keep thinking. (There are people who make catenary ridgelines with CTF3.)
    Last edited by WV; 12-16-2011 at 14:25.

  4. #4
    Strung out's Avatar
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    I have to disagree with you 2. surely you have some material laying around.
    Grab a piece and just give it a pull with your fingers.

    I've got a piece on the desk here that I can stretch from 3 inches to over 4 inches pretty easily on the bias.

    The standard cuben material used in most gear only has fibers running at 0 degrees and 90 degrees .
    You can buy cuben with fibers running at 45 degrees also, but it's nearly twice the cost. and weight.

    There is a significant amount of stretch at 45 degrees.
    The laminate does try to resist this, but it has little strength.

    Not sure how you might use that to your advantage in your ridgeline.

    To make a cat cut ridgeline, I would simply cut the 2 edges in the a catenary shape, and adhere them together.

    seems like it would work fine.

  5. #5
    WV's Avatar
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    Hmmm. I just drew 45 lines 6 inches long on a piece of CT.6K.18 and a piece of CT.6K.08, then I attempted to stretch and measure the lines. They both stretched to 6.25 inches. I was surprised; I expected the CT.6K.08 to stretch more. Must have been flawed testing technique; it's hard to stretch and measure at the same time.

    There is a significant amount of stretch at 45 degrees.
    The laminate does try to resist this, but it has little strength.
    The laminate is also what keeps the water out, which is the reason I'm now using CTF3 materials with .18 laminates (although my CT.6K.08 tarp is still performing okay).

    To make a cat cut ridgeline, I would simply cut the 2 edges in the a catenary shape, and adhere them together.
    I agree completely.

    Sgt. Rock, my test procedure may be faulty, but if so, there are few others I'd rather be wrong with.

  6. #6
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    Quote Originally Posted by Strung out View Post
    To make a cat cut ridgeline, I would simply cut the 2 edges in the a catenary shape, and adhere them together.

    seems like it would work fine.
    Bingo. That's how you do it.

    Ryan

  7. #7
    Senior Member SGT Rock's Avatar
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    Very interesting. I guess my next concern would be long term stretching of the material on the bias. I could be worried about nothing, but I wonder if the fact the materials are laminated together could eventually lead to shortened life expectancies since the two materials are going to stretch / move in different ways. If someone does make a bias cat cut cuben, I'd be interest to hear how it holds up over a few months of steady use.
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  8. #8
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    . yes intresting! thanks for all replys. when i started out, this tarp was a straight ridge with a tarp width of 9'plus. to get this i was going to insert a panel of heavyer cuben about 9-12"wide that strattled the ridge line ( also to minimize the wear in that area, heavyer cuben). now that design has been aultered a few times, but it looks like i'm back to it. only now if i cut that panel on the bias, and then attach the side sheets( no bias) with 1/2 catenary cut depth in each seam would spread the curve out over two seams. actually 1/4 cat cut out of each edge)assuming this would make things a lot easyer than trying to get the full cat depth on the one center seam!(btw- the plan is to use bonding thruout) ---------------------well my self imposed dead line for design is march, so i don't feel the need to finalize that for some time. the reason why it may appear that i'm fixated on a cat cut is cause i enjoy working with curved shapes and since straight is almost a nobrainer i'm naturally drawn to the more difficult. while in the early stages of tarp building, it does no harm thinking about it....both curve and straigh are viable at this point
    Last edited by the_gr8t_waldo; 12-17-2011 at 13:49.

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