Thermo shrinking ropes for lashing?

Discussion in 'Materials' started by Petros Polonos, Aug 15, 2018.

  1. Petros Polonos
    Joined: Aug 2018
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    Location: Samos, Greece

    Petros Polonos New Member

    I am new to the trade and my aim is to develop lashing skills and eventually build skin-on-frame Aleut kayak. I started from small things (bamboo bike trailer) and I am looking now for better materials.
    Can anybody point me towards lashing ropes with thermo-shrinking effect? The idea is to use hot air gun to finish (tighten) joints when done.

    If there are natural fibers with this feature, it would be a great bonus.
  2. JamesG123
    Joined: Mar 2015
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    Location: Columbus, GA

    JamesG123 Senior Member

    Raw hide and sinews are I guess what you are thinking of. They shrink when drying, but heat accelerates that. Its the traditional material for kayaks.

    I can't think of any structural polymers that have this effect. At least none that aren't exotic and super expensive. Plastics and line manufactures go to great pains to AVOID thermal variability in their materials. The chemistry is tricky. Most of the time the process that causes "shrink" , driving off solvents or shortening polymer chains, compromises the strength of the material. That is why thermo-shrink is usually used as insulators and encasements.
  3. Petros Polonos
    Joined: Aug 2018
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    Location: Samos, Greece

    Petros Polonos New Member

    Skin on frame builders (Guillame Kayaks and Wolfgang Brinck) mention in their walkthroughs that the skin fabric shrinks under the heat (Nylon?) and contact with water (Polyester?). But they say nothing about lashings. I did some tests and on the cheapest no-name rope achieved ~10% reversible ans some 3-5% irreversible shrink.
    I think I will stay at that plus anti-slip separators (pieces of old bicycle rubber tube) and doing lashings really tight (clamps and mallet).
  4. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    If you use something stretchy it will become very tight. An analogy would be wrapping a rubber band around your finger while stretching it. Nylon builders string is strong and stretchy and can be dyed different colors.

  5. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    PP, welcome to the forum.

    Cumulative-loading is a term that comes to mind for rubber-band type materials.
    Those that are elastic in nature.
    Versus those that shrink when heated or dried or by some other "trigger" mechanism.

    I prefer elastic material.
    Bungie cords can work well.
    Used bicycle tire inner-tubes work great but are not UV resistant!
    They can be covered.

    Thin nylon cord can work but it can be hard to find.
    It doesn't stretch very much.

    All that said, I think your best bet is look to the aboriginals of the north who created the Aleut.
    They knew exactly what to use and where to get it.
    And getting it may be your challenge.

    What intrigues me most about the Aleut is the bow design.
    The original bulbous bow!
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