UV proof synthetic standing rigging for mast stays.

Discussion in 'Multihulls' started by markstrimaran, Mar 1, 2019.

  1. markstrimaran
    Joined: Dec 2014
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    markstrimaran Senior Member

    Hi
    Anybody know of a good brand of line for rigging, best type, sheath or braid.

    Need for a small trimaran 18' mostly as a safety when in 30 mph winds.

    Currently using 3/16" polyester paracord.
     
  2. JamesG123
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    Location: Columbus, GA

    JamesG123 Senior Member

    Dyneema ?
     
  3. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Paracord is nylon not polyester. Almost any other synthetic fiber would make better standing rigging. Dyneema is very reasonably priced and extremely easy to splice eyes into. It will survive years of UV exposure. Covering it with a polyester jacket will significantly extend it's life. Kevlar doesn't get along at all with spreaders.
     
    markstrimaran and revintage like this.
  4. markstrimaran
    Joined: Dec 2014
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    markstrimaran Senior Member

    I KNOW it is a low stretch kermantal line, might be dacron. It was an inexpensive alternative at the time.

    I am looking into 1/8" 3/32" kevlar lines. 800 pound test. The mast is held with stainless steel cable. The line only supports the very top from bending above the hounds.

    20170724_102200.jpg
    20150911_235156.png
    The forward stay sail is a 150 Geona. In a 20 knot wind it puts most of its force at the top of a old Hobie cat mast.
    Leaving a 4' fulcrum as the hounds as the fulcrum.
    It is on its 3rd season and has been in the sun the entire time.
    If it fails the top of the mast at the hounds will be sheared off. In a dead in the water, stalled in jibing situation.
     
  5. markstrimaran
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    markstrimaran Senior Member

    It's been a while, and everything changes names or something new is created.
    Spectra, dyneema, spider wire, amsteel.
    Nylon, polyester, hemp, cotton, sisal, polypropylene, polyethylene, kevlar.

    I am looking for synthetic 316 stainless steel. Ya that's it.
    Able to hold a Bouy knot, and a
    3 round turns with a half hitch.
     
  6. markstrimaran
    Joined: Dec 2014
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    markstrimaran Senior Member

    Bouy knot side
    20190302_081123.jpg
    The silver washer covers a Hdpe plastic repurposed pully wheel. With a 1/4" rope grove.
    It bolts through the mast.

    Round turn side
    20190302_081203.jpg
    The ratchet used to hold the outriggers secure during transport. It was convenient to us as a stay tensioner.

    I should add that, all the stays are online with the pivot of the mast. The mast foot is hinged, the back stay is spooled to a worn gear winch.

    The stays could be non adjustable in length. I dont use the ratcheting mechanism.
     
  7. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    I am confused by your sail plan pic. Is your mast base aft of your cockpit with the mast canted way forward hanging two jibs? The inner jib has an odd very straight foot, is it boomed? What is the black rectangle interfering with the foot of forward jib? Is it's luff normally this loose? Is the black bar extending from the transom a boomkin?

    Are you looking for a backstay replacement?

    I don't mean to be offensive, but the close up of your mast head scares the be-jesus out of me. I predict the stays lubberishly attached will come off of the mast long before the mast it self fails.

    I forgot to mention in my earlier post that Kevlar is very susceptible to UV degradation.
     
    Last edited: Mar 2, 2019
  8. markstrimaran
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    markstrimaran Senior Member

    I am only replacing the black polyester stays.

    Yes the mast is aft, and canted.

    The forward stay sail foot is longer than the boat. The black is a cabin. It needs a recut foot, but it still works in very light winds.

    The stern black spar, is the running back stay (mast winching davot).

    The main stay sail is boomed with a solid pivot at the front point. It is fully reefable at any %.
    I 20170318_161000.jpg 20150731_100639.jpg
    The 100% geona. And in really nasty wind a 75% jib sail that will auto jib. IMG_20170402_47576.jpg
    Someday a custom carbon spar. Until then used hobie cat masts are almost free.

    The trimaran is trailed and can be rigged in about 30 minutes, hence the Aft mast.
     
  9. Blueknarr
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    Blueknarr Senior Member

    I'm starting to understand your rig. Just a few more questions.

    Is the mast's sail track forward or aft?
    The black lines you wish to replace are the upper shrouds?
    No spreaders?

    Do you know the righting moment?
     
  10. markstrimaran
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    markstrimaran Senior Member

    The masts sail track is forward, it only gets used when I adjust the distance between the pulleys for the stay sails.

    The upper shrouds , no spreaders, the reason their not stainless steel is due to low budget build, and I never realized the problem until after sail in strong gusty winds. The nylon line was simple to anchor to the mast head.

    The righting moment, I have never calculated it. The trimaran will heel maybe 10 degrees, if flying a hull. It takes two sails up and 20 mph wind.

    I can adjust the outriggers, to sit higher in the water making it more heelish. The amas are large, I once lost a dagger board cassette, and had to sail with the fully flooded ama on the leeward side. In 15 mph winds, with white caps, 3 miles to the boat ramp.
     
  11. Blueknarr
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    Blueknarr Senior Member

    I am assuming the upper shrouds attached to amas.

    Without knowing the exact mast length, distance from mast base to the shroud deck attachment! Or actual righting moment, it is impossible to calculate the minimum strength needed for your shrouds. In an earlier post you stated that you were considering 1/8" Kevlar with a 800lb breaking strength. My guess is your shrouds should be closer to 8 thousand than 8 hundred.

    Spectra, Amsteel, and Dyneema are sufficiently similar to lump together. Ales.stouts and pillsner are all beer, but slightly different. All high tech/strength fiber ropes do not hold knots well including the bout knot and should be eye-spliced. Fortunately, their typical 12 strand construction makes for easy splices.

    Shrouds need to be adjustable. Especially since the height of your amas is flexible.
     
  12. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Good point,.. 6mm 15/64 dyneema 8000 odd pound breaking strain, slide flexible uv poly/ pvc up to past any where it might catch, it's soft when not taught, you can knot it with a ridiculous amount of half hitches . But splicing is so much less Lubberish[nice term, I'll use that thanks], * if your going to knot it allow for the take up as well. Anything sharp...see top of mast photo.. will cut Dyneema and rubbing will mash it into itself ,sort of go furry. 6mm is so strong your fittings will pop/ mast will snap way before it breaks, but if you do catch on something sharp you have more of a sporting chance. It's not as if windage is a big issue on your rig. *.you could buy stainless 0 ring or a block{clunky] and lash from that point to the chain plates, like old boats, cheaper, and very affective. or pulleys/blocks with cleats for quick adjustment, but clunkier and less sound. and a rubbing point when towing. The knowledgeable folk always recommend terminals I've found, which are cheap.
     
  13. markstrimaran
    Joined: Dec 2014
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    markstrimaran Senior Member

    I guess I will reorder some 3/16" dacron equivalent in dyneema. Preferable with a polyester kermantal sheath.

    One note the mast is under zero compression. In most sail boats the mast is compressed, If my memory serves me well.

    The whole tri is about 800 pounds. If I stood on a dock and could pull 800 pounds on my halyard. It would be sufficient force to tip the trimaran over. From the top of the 28' Hobie cat mast.
     
  14. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    You could use gal, it needs swaging though, don't try U bolts, and keep it away from the other metals, it might eat or be eaten by something depending on galvanic scale. I'll let someone else answer the mast statement. but pretty sure they all do when in use..and beam ,plus displacement you'll have enough for your righting moment probably. anyway, cheers
     

  15. Blueknarr
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    Blueknarr Senior Member

    5/8 dacron (polyester) equals the strength of 3/16 dyneema


    Many monohulls have non-compressed masts. My former antique 30 foot racing sloop's shrouds actually sagged dockside. Yet they were sized to withstand tremendous righting force. Many times greater than her 6,000 pound displacement.


    You mentioned that the amas folded in. Are you wider than 8 ft. 9 ft .10ft? Trust me your righting moment is many thousands of pounds.
     
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