How to seal Dyneema?

Discussion in 'Laser Talk' started by Beachcomber, Jan 25, 2009.

  1. Beachcomber

    Beachcomber Member

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    Any ideas for a good at-home technique for sealing Dyneema rope, aka Spectra and uhmw polyethylene? If you try to melt it in a flame, it frays outwards and doesn't really stick to itself. I whipped my clew tie down and just to see what would happen, I melted it on my gas stove. It was held tightly enough that it did stick to itself, but its tendency to expand outwards was such that it formed a mushroom shape.

    I've tried heating up a knife in the stove flame, but it cooled down fast enough that it didn't make it through much of the rope. If I had asbestos fingers, I could just melt it and roll it together between my finger and thumb, but I don't so it would be painful. I'd like to find a quick technique that's quicker than whipping. I don't know what to try - maybe pliers and blowtorch?
     
  2. Bungo Pete

    Bungo Pete Member

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    I am not familiar with Dyneema, but to keep any synthetic line from unlaying when it is cut (without traditional whipping), you have a few options. Others may have different ideas, but here is my 2 cents.

    1. If you are going to do a fair amount of line work (or are part of a group who will get some use out if it), invest in a good quality, heavy duty soldering gun such as a Wen. You can then buy the line cutting attachment (or it may come with it), and this will be similar to what you see in your local boat shop or hardware store.

    2. You can also invest in an inexpensive heat gun and some electrical shrink wrap. This stuff works quite well and provides a nice finished look. I did a couple of lines using this method last summer and they came out great. Also, be advised that the "marine" shrink wrap "whipping" is the same stuff except in different colors and much more expensive.

    3. The old stand-by is a good Zippo lighter. Don't mess with butane as it won't work nearly as well and you will burn your fingers. Get the real thing and plenty of extra fluid. I keep one handy for quick jobs and as a backup. It also has a cool NAS Bermuda logo on it :D.

    Hope this helps, and stay away from the stove!
     
  3. Beachcomber

    Beachcomber Member

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    Good suggestions. I'd seen photos of what must be heat shrink, but I'd assumed it was electrical tape. I have a Zippo, and have never really had much use for it, so this might be one. I think the Dyneema would still fray outwards no matter the source of heat, unless you do something exotic and pyrotechnical like dipping the rope in the Zippo fuel before setting it on fire!

    I'm sure you're familiar with ultra high molecular weight polyethylene (UHMWPE). It's the ultra strong, ultra tough (therefore hard to cut) slippery stuff that loses it's color when stress is applied to it. It's used on the high tension parts of the newer vang and outhaul systems.
     
  4. 4.7sailor

    4.7sailor New Member

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  5. AlanD

    AlanD Former ISAF Laser Measurer

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    Most dyneema rope has a dyneema core, with a nylon sheath or casing.

    Cut the rope and then melt the ends with a lighter, but not heavily.
    Then pull the core through melted end.
    Cut about 10mm or 1/2" from the core and then slide the core back into the sheath until the core is no longer visible.
    Remelt the end of the sheath so that the core is fully incased.

    For rope which is effectively only a dyneema core (no sheath), other than whipping the end, I haven't really found anything that lasts extended periods.
     
  6. Merrily

    Merrily Administrator Staff Member

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    I've been getting by with a little bit of carefully placed duct/ gaffer tape. Lasts a season. :eek:
     
  7. pez

    pez Member

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    I tape withmasking tape tighly to hold the end together, then melt with a lighter... I find that the masking tape doesnt burn all that much and certainly not as fast as the line. I then stub it out like a cigarette butt and it mashed the molten fibers together inside the masking tape "tube"... once it cools you can with levae the tape on or remove it.
     
  8. laserbahamas

    laserbahamas New Member

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    I also use this techpique except i put electrical tape onto the rope, Burn the rope but leave the tape on the rope so theres no possiblilty of it expanding!
     
  9. Bungo Pete

    Bungo Pete Member

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    Good suggestions all around. I forgot one more option, which is liquid electrical tape. I think that has been marketed as a replacement to traditional whipping.

    Regarding the Zippo, I too have never been a smoker except for the occasional cigar, but they do come in handy and are far superior to the Bic Butane.

    Is there an advantage to a dyneema core line?
     
  10. AlanD

    AlanD Former ISAF Laser Measurer

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    For all you're control lines, you want a low stretch rope. Dyneema /Spectra core ropes are low stretch ropes in comparison to most other types of rope, other than kevlar core rope. Kevlar core rope is generally hard to purchase these days, suffers from breaking if it's taken through tight turns (you shouldn't use bowlines etc with them, because of the tight radius), and finally, it's outsde the class rules to use kevlar rope for the vang and cunningham.
     
  11. glasky

    glasky Member

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    All the above can work - but also whip it by sewing the end with dental floss
     
  12. lawrencew

    lawrencew New Member

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    If you tape the ends with electrical tape, cut the rope in the middle of the tape to stop ends fraying, then drop 5-10 drops of super glue over the end it dries like it's been melted. When its dry just take the tape off. Hope this helps.
     
  13. pez

    pez Member

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    Thats a nice idea with the superglue. I had done trick of always cutting a line through the tape, but handnt thought of the superglue.
     

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