Spectra vs. Dyneema

Discussion in 'Sunfish Talk' started by phish133, Jul 8, 2008.

  1. phish133

    phish133 Sunfish sailor

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    Can someone give me a simple answer to the difference if any.

    Also, what's the timeline for these ropes? First Spectra , then Dyneema 60, then 75 , then 78, etc...? Any reason to buy Spectra/Spectron if it's available?
    Seems to me that if the cost is comparable, then one would always buy Dyneema 78 . right?

    This all came about because I've got to change my outhaul/and cunningham lines.
     
  2. DanB

    DanB Crabber

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    From the “Shhhh - - if they think it’s mysterious they’ll pay more for it” Dept.

    [From Wikipedia]
    Both are high-modulus polyethylene (HMPE). Dyneema is a registered trademark of Royal DSM N.V. (The Netherlands). Honeywell developed a product identical in chemical structure, which is sold under the brand name Spectra.

    I believe 60, 75, 78, etc all refer to the strength to weight ratios when this material is spun to create oriented-strand yarns. The higher the number, the greater the strength ratio. ( http://www.dsm.com/en_US/html/hpf/dyneema_yarn.htm )

    IMHO it is splitting hairs infinitesimally to be troubled much over the strength quality for the light loads and short lengths found with Sunfish. The key benefits are the fast running and low water retention properties. Some reading up and selective matching of line to application has great potential for saving much $$.

    .
     
  3. billmcinnis

    billmcinnis Member

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    A problem I've had with some of these is that they tend to flatten out with use and then slip in the cleat. Amsteel 12 seems to stay rounder and grips in the cleat better.
     
  4. DanB

    DanB Crabber

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    Sampson Rope’s Amsteel 12 is still a HMPE (Dyneema) fiber only with a urethane coating added. I think what everyone is failing to grasp is the need to see past all the marketing hype and trade name buzz. Fiber composition is important for some of a rope’s qualities, but much more is dependant on how that fiber is spun, twisted, laid parallel, braided, double braided, and pre-stretched. A fantastic fiber spun into in a loose single braid might make a suitable dock line, but would be worthless for holding a set as a halyard. Buying a fiber name without understanding what application the rope’s constructed for and what about that construction makes it so, places the consumer at the mercy of the marketing department when it should be the other way around.

    So, why is Amsteel 12 better at holding it’s shape – the urethane coating, the 12 plait lay-up, the tightness of the braid, pre-stretching? Is it going to be well suited for the static line outhaul and cunningham application being considered? :rolleyes:

    .
     
  5. billmcinnis

    billmcinnis Member

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    I don't care why it holds it's shape better, I just think that it does. I don't think the material matters, it just probably has a tighter weave or whatever. I'm not saying that it's the only one that's any good, but, there are some that I paid quite a bit more for that were stronger and had less stretch (which we don't need), but they ended up slipping in the cleat and I had to get rid of them.
     
  6. phish133

    phish133 Sunfish sailor

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    Now to fuel the fire again, what about diameter? I tried some 1/8" Polyester cover/Spectra or Dyneema cored line, and it seemed to bind a bit. I have used a solid Dyneema or Spectra in the past(seemed slightly smaller than 1/8"), and the lack of a cover material seemed to help it"flow". Of course a Polyester cover on the 1/8" line helps it cleat, but at too much of a price in "flowability" (don't look that word up...).

    I'm thinking of trying 7/64" Dyneema(Amsteel Blue), but am concerned it may be too small/slippery for the Clamcleats on my spar (standard Sunfish Black Clamcleat). Any comments/suggestions?
     
  7. DanB

    DanB Crabber

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    I think in your situation, given I don’t have deep pockets for trial & error shopping. I’d take advantage of being in a location such as yours where there’s undoubtedly many boat parts dealers. I’d go to a couple of those stores, grab a suitable cleat off the shelf, walk across the room to the rope locker and start comparing lines. :)
     

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