Self tacking jib system question

Discussion in 'Multihulls' started by nwguy, Apr 24, 2020.

  1. nwguy
    Joined: Feb 2010
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    nwguy Junior Member

    Maybe this isn't strictly related to multihulls, but it's on my trimaran so I'm posting in this forum. Someone suggested I convert my jib to be self-tacking after watching this video of my newly-built boat:



    I did some research and concocted a hybrid between Harken's Standard Self-Tacker with the sheet-forward configuration shown here:

    Harken Sailboat Hardware and Accessories https://www.harken.com/content.aspx?id=3911

    and Harken's Crossbow system shown here (though mine doesn't pivot):

    Harken Sailboat Hardware and Accessories https://www.harken.com/productdetail.aspx?id=40227&taxid=7384

    Question below, but here are pictures of it:

    stj2.jpg stj3.jpg stj4.jpg

    When I looked at these 2 Harken systems I didn't understand how sheeting in would pull the sliding car on the curved track towards the centerline of the hull. Indeed sheeting in does pull the jib clew closer to the sliding car, but it has no effect on the position of the car. What am I missing? Is there a way to configure the sheet routing so it'll work with just one line? Do I need another line that pulls the car closer to the centerline? I was hoping to do this with just one line.
     
  2. revintage
    Joined: Nov 2016
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    revintage Senior Member

    Take look at the red one from the traveller. This is from Harken System Diagrams for Tornado.

    tornado-deck-lg.gif
     
  3. kapnD
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    kapnD Senior Member

    Running the sheet to the bow prevents it from performing both actions.
    In order for the sheet to pull the traveler in, it must pull from the center, just in front of the mast.
     
  4. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    I would use two lines. Your existing one to control the sail's fullness. Plus a second line attached to the track car thru a block located on the center line about a quarter of the way from the track to the bow to control the sail's angle. If the pivot block is too close to the track the line will wrap around it during yacks. If it is too far forward it loses effectiveness.
     
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  5. nwguy
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    nwguy Junior Member

    I did some tests based on what kapnD said, and that seems to work optimally. The first thing sheeting in does is to pull the clew of the jib to the car, then the car moves closer to the centerline. Once you sheet out so the car is at the end of the track, the sheet pays out normally for going way downwind. I thought about the 2 line approach, but if I could get it to work for the 80+% cases of how I sail, then a single line for control is appealing. At least worth a try. The Harken system for Tornados is more complex that what I want, though I see the advantage of sheet control from either ama.
     
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  6. revintage
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    revintage Senior Member

    Think you are complicating things a bit. You should just adjust the second line coming from the center, to get the optimal close hauled sheeting angle, then leave it there. Then you play your present line. If it doesn´t work have might have bought a track with the wrong radius.

    track.gif
     
    Last edited: Apr 25, 2020
  7. upchurchmr
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    upchurchmr Senior Member

    2 lines.
    traveler car to the CL .
    Current line for jib sheet.

    You really want to at least have the jib sheet on both ama's somehow.
     
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  8. nwguy
    Joined: Feb 2010
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    nwguy Junior Member

    OK, I'm going with 2 lines. Not sure which one would be called the sheet, but there will be the forward-routed one shown in my pics above (jib sheet per upchurchmr's post), and the one that pulls the traveler car closer to the CL. Both lines will be routed though the space below the mast. The castings for stepping the mast there are nicely curved and will allow rope to pass through well. I bought a swivel cam cleat to mount a few feet behind the mast base for routing one of the lines to. Should be able to operate that line from either ama with that swivel cleat. Then at that same location I'll mount a non-swiveling cam cleat for the other line.

    So which line should go through the swivel cam cleat (operable from the amas) and which line should go through the fore-aft aligned non-swiveling cam cleat? Seems like the one that pulls the traveler car would be the one you use more often.

    The picture below from a video of a similar system has a fairlead supported by lines only, shown by red arrow. What's the name for that kind of fairlead?

    fairlead.png
     
  9. upchurchmr
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    upchurchmr Senior Member

    That fairlead is called a "barber hauler".
    It is to move the jib sheet outboard when you do not have a jib track.
    You don't need it.
     
  10. revintage
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    revintage Senior Member

    As pointed out twice above, the forward going is for sheeting and should be led through the swivel cam cleat. The line to the traveller is just for sheeting angle and not as often used.
    The 49er has arranged the jib sheet with a swivel cam cleat, works fine. But one sheet end at each side might be better in a boat as wide as yours, and is what is used on every beachcat/tri.
    To get more control you might want to arrange sheet blocks for 1:2 or 1:3 between traveller and jib clew, which is standard procedure. Seems you have very little room, can you move your track further to the rear? But probably it is enough with smaller blocks.
     
    Last edited: Apr 26, 2020
  11. upchurchmr
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    upchurchmr Senior Member

    Most beach cats don't have a jib traveler. That forces two jib sheets and the barber hauler to bring the jib clew wide while reaching or running.
    This doesn't need it

    nwguy, while tacking, you might need to ease off the jib sheet a little, so that the traveler car will run freely. If you leave the jib tight, there might be so much friction in the traveler car that it does not easily move to the opposite side.
     
  12. nwguy
    Joined: Feb 2010
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    nwguy Junior Member

    Even with the jib sheet (line forward to bow) taught, the car runs smoothly from end to end on the track with little friction. That track is actually the mainsheet traveler to the Supercat 20 who's hull I'm using for the vaka. It's 6 feet long. I made a giant square and determined the imaginary line from the jib clew to the forestay, at a 90 degree angle to the forestay. Measured that and drew an ark with a string and pen. Then bent the track to that arc on my friend's bender:

    IMG_20200421_133414200.jpg

    Doing that was pretty fun. The curve is pretty accurate as a result. I mounted a fairlead on the deck of the vaka just forward of the mast to make the jib sheet lie flat on the casting below the mast.

    For the other line I added a 3/16" AL plate to the back of the center of the track. It has a fairlead attached, and above that on the mast a block with a swivel attached to a strap eye. That line runs under the mast, up through the fairlead, over the block and then down to the car. Surprisingly little friction there.

    The knot at the end of the yellow rope shown in the picture will actually tie to the jib clew. Yeah, I've thought about bumping up the pull ratio of the jib sheet with another block. We'll see. IMG_20200426_164318280.jpg

    IMG_20200426_164400926.jpg

    IMG_20200426_164436997.jpg
     
  13. upchurchmr
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    upchurchmr Senior Member

    The setup looks really good.
    Great to have friends with nice tools!
    The friction might change under sailing load.
    Just wanted you to beware.

    Now for the sailing test.

    You are really lucky with that mast step configuration, wouldn't be possible with lots of other boats.
     
  14. nwguy
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    nwguy Junior Member

    My friend also let me do some TIG welding on the brackets that support the track. First time for me. I fillet braze steel bike frames with brass, and it's somewhat similar. Here's a pic of my arc template before bending the track, and the system now with safety tennis balls and (yellow) line to prevent lines from hooking around the ends of the track.
    arc.jpg fullView2.jpg
     

  15. revintage
    Joined: Nov 2016
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    revintage Senior Member

    Most old dated cats don’t have a jib traveller, but almost all modern do;). Not to say that traveller is allways better.
     
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