Joining Bungy Cord...

Discussion in 'Boat and Accessory Building' started by mikemike, Jan 3, 2009.

  1. mikemike

    mikemike Paddler

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    Does anyone know of a good system for joining two end pieces of bungy cord together? Anyone got any good tricks for this?
     
  2. sushiy

    sushiy Paddler

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    I really don't care how the things look like as long as it functions well. So, I melt the end and just do fisherman's knot which is secure but easier to undo if needed.

    http://en.wikipedia.org/wiki/Fisherman%27s_knot


    Doug Alderson's Savvy Paddler syas ( on pg.125) spiral hitching using whipping twine is good for it and makes less bulky joint, and you can cover it with electlic tape to cover the twine.

    The Savvy Paddler
     
  3. Astoriadave

    Astoriadave Paddler

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    Mike, 6 or 7 years ago I got tired of dealing with a bulky knot at the rear of my sprayskirt -- basically an overhand bend, similar in function and bulk to what sushi describes. The thing was large enough it kept popping my skirt, from the back! Now and then I could get it on securely and under the coaming rim a bit, but it was strictly hit or miss.

    So I decided to try a pair of zip ties, about 1/2-inch apart, over both cord ends, with just a quarter inch of free cord on each side. I reefed on those babies as hard as I could with some pliers and snipped 'em off close to the lock. This had the effect of compressing the cords a lot.

    I thought this would be OK for a while until I thought of something better. You know what? Those suckers are on there and still going strong!

    The closure is very low profile and now that sprayskirt always stays on -- the "knot" is always under the coaming.
     
  4. Astoriadave

    Astoriadave Paddler

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  5. mick_allen

    mick_allen Paddler & Moderator

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    If you want a minimal connection appearance, you can play with the fact that the bungee will neck down to 1/2 it's size if you stretch it to maximum.

    so you cut the cord long, c-clamp one end, stretch to max and c-clamp a few inches away. Now the area betw the clamps is stretched thin. Do the same for the other end so it is right beside the first.

    Now you have several options.

    If it is not to be cosmetic, I very tightly whip the 2 necked parts together with a long pc of kevlar pulled from some kevlar cloth, epoxy up, and release it all the next day and cut off the free ends. Makes a slim decent joint a tiny bit larger than the single bungee diameter (for example joining a sprayskirt bungee)

    If it is to be cosmetic, carefully cut the nylon covering of both join areas past the joint, and in both roll the covering back. Then mush the rubber cords together in the join area and epoxy - say over a 1" length or more. Next day cut and clean off excess rubber and roll the covering back over the join on one side and over some portion of the nylon covering.

    Depending on the situation and the thinness of the whipping cord, you maybe can add some during but of cours you can add some later.

    I haven't done the latter part for a join, but have done the first as well as using the principle for finishing the ends of a bungee ( ie pull tight, set up nylon covering in epoxy, setup, then release tension and cut where necked down).

    The latter tech is perfect for threading bungee into tight places - neck it down, soak area in CA and after it's setup in 2 minutes, cut at an angle it'll fit anywhere, heh heh.

    mick
    .
     
  6. Dan_Millsip

    Dan_Millsip Paddler & Admin

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    Better off with a URL link Dave -- the tinyURL links expire after a short while.

    I use a double half hitch style knot for tying my deck rigging -- it's easy, gives you some options if you need to change your rigging setup, and it doesn't require any additional hardware. I'll take a picture of my rigging in the next while and post it here.

    *****
     
  7. Astoriadave

    Astoriadave Paddler

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    Seriously? Never had that happen unless the original link has 404'ed.
     
  8. B1200

    B1200 Paddler

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    Heat shrink applied over any of these solutions provides a smoother, cleaner join.
     
  9. Day_Sailer

    Day_Sailer Paddler

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    Dang, B1200, you beat me to it. I use the heatshrink idea on two critical systems on my (racing) sailboat. Only issue is eventually it gets brittle and leaves the joint exposed. I replace the cord and heatshrink whenever that occurs.

    ADave, The Ziptie idea is very good, but would worry that eventually the ties will weather, get brittle and break at a very inconvient time. I use 10-50 zip ties per day at work, and have never found a brand that did not deteriorate if used outside. We only use them for non-critical tempory uses. Perhaps, taping over that joint would help protect it.

    For absolutely reliable joints I use 2 hogs rings, covered with rigging or electrical tape. Replace the tape as it shows signs of aging, and inspect the shock cord at the same time for possible need to replace it as well.

    Taping tip (maybe you already know this). I know that most of us like that macho tearing/snapping off of a taping job. But that leads to the ever present 'flag' of tape as it unwraps. For a more permenate tape job, lay the last 2-3 laps unstretched, then cut the tape with knife or sissor(sp?) and lay the end down unstreched. Will usually not unravel. 1-3 rolls of daily use X 31 years.

    Just my $.02
    ds
     
  10. Astoriadave

    Astoriadave Paddler

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    Daysailor, Those zip ties are going on 7 years in service and appear as good today as they did when I put them in place.
     
  11. Day_Sailer

    Day_Sailer Paddler

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    Looks can deceive. If exposed to UV, 7 years is a very long time.

    I've gone back after less than a year on some installations and with a bit of stress on the tie.... snap... even broke a pair of safety glasses when one let go unexpectedly when pulling on one and it broke and I slugged myself .....oowwwww. The tie looked almost new...

    If not stressed a bit, they will hold something static in place for along time. But I wouldnt trust one on a boat. Once when racing out of Marblehead, I had done a quickee repair for the day. Lost a $50 piece of equipment, and had to drop out of a race. 3400 miles towed, one broken tie wrap, 5th place at Nationals instead of ??? (7 race series, at least a 3rd, probably 2nd)

    If the tie is doing an important function, at least replace it with a new one.

    Gear failures when kayaking can be more serious than my broken glasses or lost race.

    Wish I could go paddling today... oh well, best to all ds
     
  12. mikemike

    mikemike Paddler

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    Thanks for the responses; I had one other question: what is the standard diameter of the bungee that is used on kayak decks? It's fairly thick stuff; I want to order some, but I am not sure about the size I need.

    Thanks again,
    MM.
     
  13. Dan_Millsip

    Dan_Millsip Paddler & Admin

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    I like 1/4" bungee -- anything smaller and I find it difficult to lift up off the deck with gloved hands.

    Here's a photo showing how I attach my bungees. Basically it's two half hitches tied tightly over the opposite ends of the cord. It's never once failed or showed signs of loosening. The advantages to this way are twofold -- it's much easier to lift the bungee at the knots, and if I need more bungee so that I can transport large pieces of firewood etc., I can slide the knots towards each other and the bungee gets longer -- if I need the more bungee holding power, I can tighten the rigging up. Best part is that it requires no additional parts. The ends of the bungee are burned to stop fraying. I also use a sliding knot for my perimeter lines -- in cold weather I loosen them off a bit to make it easier to grab with gloved hands:

    [​IMG]


    *****
     
  14. oldsailor

    oldsailor Paddler

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    Dan.... how are these bungees attached to the kayak's deck? It looks like a ribbon of some sort coming through a slit in the deck. Is that right? How do you keep it watertight?

    Craig
     
  15. Astoriadave

    Astoriadave Paddler

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  16. Dan_Millsip

    Dan_Millsip Paddler & Admin

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    Thanks, Dave.

    Craig, they're loops of web stapping with a plywood backing, held in place with Marine Goop.

    Dave's link takes you to a description of the slots being cut, here's a link that shows the padeyes before installation:

    http://www.westcoastpaddler.com/buildin ... 12&pos=192

    *****
     
  17. oldsailor

    oldsailor Paddler

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    Thanks for the links... and thanks for documenting your work so well, Dan. One of the things I like about my Mariner boats is the way the Broze brothers did the bungees. They drilled tiny holes in the deck and then stretched the bungee out so it fit through them and then tied a knot to secure the ends. Thus no padeyes on the front deck to catch spray but the bungees effectively stop any water intrusion through the holes. No messy goop either. It's a bear to replace them, though.

    Your approach looks very elegant.

    Craig
     
  18. Day_Sailer

    Day_Sailer Paddler

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    Here is a link to some UV inhibited shock cord that I have found lasts better than the colored stuff. More expensive but really holds up. Maybe the ol' salts on this board already know of this stuff.

    http://www.apsltd.com/Tree/d3000/e876.asp
    Second item down. Solcor
    Third item down, the solid elastomer also has good UV resistance. Thought it may have too strong of stretch and return strength for deck lines. Might be worth trying though. It has really held up as a spinaker pole springy return keeper. Lots of stress and on its third season always exposed to the sun.

    ds
     
  19. cattail

    cattail Paddler

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    Day Sailor thats great to know on the UV stable bungy. I plan to order some from them. My method is Hog rings to make loop ends on the 1/4" stuff west marine sells plyers to close them too. I liked that slip knot shown cool to be able to adjust these.