Spreader tip tips ? No pun intended.

Discussion in 'Sailboats' started by SwedenYachtsDaniel, Oct 4, 2024.

  1. SwedenYachtsDaniel
    Joined: May 2018
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    Location: Norway

    SwedenYachtsDaniel Junior Member

    I have a 32 foot, long keeled sailboat that used to be sloped rigged. It has a 1 spreder masthead rig. It was designed in several rig configurations and now i have re rigged it to the kutter stay whit running backstays option. On the designers drawings for the kutter rig it has shroud going via the spreaders to the hight of the cutter stay. I have those shrouds but i have them pretty slack. Am unsure about about how to angle the shrouds to the spreaders. If i need a different spreader tip that makes this new shrouds discontinued? Or if i can "average" the angles between the vertical and this new diagonals/vertical shrouds to the kutterstay?
     

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    Last edited: Oct 4, 2024
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    A drawing would help. I think you are confusing stays with shrouds.
     
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  3. SwedenYachtsDaniel
    Joined: May 2018
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    SwedenYachtsDaniel Junior Member

    Yes i am , Thanks Gonzo. A language mix up. Ill edit my post and add a drawing..
     
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  4. rangebowdrie
    Joined: Nov 2009
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    rangebowdrie Senior Member

    As mentioned above, the running backstays have nothing to do with the spreaders.
    On a single-spreader rig such as you pictured, the ideal configuration is for the spreader(s) to bisect the angle, i.e. the angle between spreader and the wire above the spreader and the angle between the spreader and the lower section of wire should be equal.
    That puts the spreaders in pure compression, as they should be.
    Obviously, the lower spreaders on multiple spreader rigs require some compromise, just the nature of the game, we accept that with stronger spreaders, and just as important, much stronger mountings that can withstand asymmetric loading.
     
  5. SwedenYachtsDaniel
    Joined: May 2018
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    SwedenYachtsDaniel Junior Member

    I agree with you. But my question was not about the backstay. It was not about multiple spreader rigs. How you describe the rig is how it use to be. I added a kutterstay and running backstays. That is also just fine. Just information to provide context to the question.

    My question however is about the SHROUDS going up to the area of the mast where the kutterstay attaches to the mast. (not the running backstay) You se them in the drawing. Can i have those running parallel to the cap shrouds from the spreader down to deck, or do i need to convert the spreader tips to discontinued ?
     
  6. SwedenYachtsDaniel
    Joined: May 2018
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    Location: Norway

    SwedenYachtsDaniel Junior Member

    I added a drawing to my first post , also lock at the answer to rangebowrider where i try to make my question more clear.
     
  7. Will Gilmore
    Joined: Aug 2017
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    Will Gilmore Senior Member

    I am not qualified to answer this question as a NA, but it seems that the upper shrouds should work to hold the angle of the spreaders as is. The additional forces placed on the spreaders by the upper diagonal stay to the cutter forestay would be countered with a little more tension in the lower half of the upper shrouds, because now the two stays above the spreaders are pulling up in unison and must be counted by the lower half of the upper shroud.

    Unless you are letting your shrouds run free over the ends of your spreaders, you shouldn't have to change the angle. When the cutter jib pulls on the mast, it will pull upward on the spreader as the mast wants to bend. That needs a countering brace. Free running shrouds won't do that for you. The other option might be to just connect the upper diagonal to the upper shrouds at the spreaders. In that case, you may want to change the angle of your spreaders.

    I hope this post will give a real naval architect some material to work with.
     
  8. rangebowdrie
    Joined: Nov 2009
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    rangebowdrie Senior Member

    Ah yes, I see now.
    You've added what Will Gilmore calls an "upper diagonal", (good name).
    If you looked at the rig in plan view, (from above,) and mapped-out a force diagram you will see that the shroud you added adds weight aloft and a lot of vertical tension in order to counteract a small amount of athwartships/lateral load.
    You might find that the offsets of the running backs from centerline are actually more in line with the angular displacement that the forestay acquires when the staysail is flying.
    Just a tip, in your rig you have a stay that runs from the "head" of the stem, (stemhead,) to the "head" of the mast, (masthead,) that is called a "headstay", the stay you added for a staysail is called a "forestay", in strict parlance the sail that sets on that stay is a "forestaysail", the term "cutterstay" is one used by the uninitiated.
    As Will Gilmore said, the fore-and-aft loading on the mast from the staysail is far greater than the lateral loading from that sail.
     
  9. SwedenYachtsDaniel
    Joined: May 2018
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    SwedenYachtsDaniel Junior Member

    Thanks Rangebowrider. I mostly agree. The running backs would do the job just fine Im sure. But, i dont see how the "upper diagonals" take up any load for and aft.
    BUT THIS IS NOT MY QUESTION.
    The only thing im asking about is this: My Cap shrouds and the "upper diagonals" go parallel from the turnbuckles on deck, via the spreader tips where the cap shrouds goes to the upper part of the mast and the "upper diagonals" goes to the area where the kutterstay is attached. They therefor has different angles to the spreader. So is it ok to average those angles to the spreader, or should i convert to a discontinued spreader tip, where i only have 1 Vertical from deck to the spreader.
     
  10. rangebowdrie
    Joined: Nov 2009
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    rangebowdrie Senior Member

    I understand what you're saying.
    You've already got that shroud going to the deck, why change it now.
    The masthead lateral load is far greater than any lateral load caused by the forestay, therefore it's not necessary to equalize the angles that those two shrouds place on the spreaders, that would cause the upper shroud to place a greater load on the spreader that was trying to pull the spreader up.
    Look at the angle that the lower spreader on a double-spreader rig has, follow it and you'll be at least in the infield of the ballpark instead of the outfield, (or the parking lot). LOL.
    Oh, "kutterstay" is a made-up word, the proper word is "forestay".
     

  11. SwedenYachtsDaniel
    Joined: May 2018
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    Location: Norway

    SwedenYachtsDaniel Junior Member

    Thanks , i will do that. All words are made up ! ;). ;)
     
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