Wants to broach

Discussion in 'Stability' started by Moods, May 25, 2018.

  1. Moods
    Joined: May 2018
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    Location: Perth

    Moods New Member

    9A7D4914-7278-48AF-A28A-2A74414E5586.jpeg C490F365-0B2E-488D-9471-4BC37624D383.jpeg 9A7D4914-7278-48AF-A28A-2A74414E5586.jpeg C490F365-0B2E-488D-9471-4BC37624D383.jpeg 0E388459-4349-4C36-8BEB-3A8055EC910D.jpeg 1D7131AB-B9F4-405A-BD55-3C1FD2F324B6.jpeg 3C4F05B0-00EF-4827-A805-DDE5CB1905CC.jpeg Hi all,
    I have an 8m jackman that likes to lean over towards the on coming sea when traveling side on, it rides great directly into and with the sea.
    I feels like the rail grabs and pushes the nose down make you have to steer out of it the it will jump to the other side ( can be quite scary at times).
    I think the person that built it has put more cabin on to the it was designed for.
    I have 300kg of ballast in the transum that helps a lot.
    I’m looking at getting 2 large chimes weld on either side to try and help push the nose out.
    Thoughts if this will work or other ideas please
     

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  2. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Junior Member

    Sell it for a loss and move on.
     
    Last edited: May 26, 2018
  3. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Nice looking boat all except that it appears hopelessly top heavy and hints that it would run down by the bow.

    The skippers chair is way above the center of buoyancy and that alone is enough to influence the behavior of a relatively small boat. Aft end of the top appears to have vertical rod holders. Even the rods would have a small but measurable affect.

    300 kg is a lot of ballast for such a boat. Take an inventory of all the things that you can remove from the forward end of the boat. Twould be a shame to have to remedy the situation by using Light Fandangos advice. He may be closer to the reality of the situation than is pleasing to contemplate.
     
  4. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Junior Member

    It is a lovely looking boat , even with the advise of it's issue it may sell for not much less, with a guilt free conscience, fine in a river or some lakes,. fair weather..no swell..? Not many in WA
     
  5. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Fully concur.

    All skippers chairs are.....one assumes you mean the CoG.!!
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Talk of a fire-sale is premature, the boat needs thorough experimentation with trim tabs, properly used, cross-wind lean is common in such boats with high forward structure, and with a single engine, tabs/interceptors are your only way to correct it. 300kg of ballast ? Are you speaking of the engine ?
     
  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Are there any examples of this boat that run well. For example, with a sterndrive installation?
     
  8. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I take it the transom ballast is the engine?
    My first response was to sell and move on.
     
  9. HJS
    Joined: Nov 2008
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    Can this form of spray strip be the cause of this particular behavior?

    JS


    upload_2018-5-30_12-46-30.png
     
  10. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Not likely, perhaps the opposite.
     
  11. HJS
    Joined: Nov 2008
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    BleuBell
    Do you have any concrete experience? Otherwise, your post has extremely limited value.
    JS
     
  12. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I do, but "buyer beware".
     
  13. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    So the boat "leans over" when traversing beam seas, and the lean is toward the oncoming waves. Then, reading between the lines, it jinks around as waves pass under the boat. That is not "broaching", especially since he says it runs perfectly well, down sea. It sounds like the lean is induced by the helm being put over, in the cross wind that is producing those waves, to keep the high bow from being pushed down-wind. I'd advise using tabs to correct the lean, and trimming the engine in, to move the CLR more forward, so your line of thrust isn't pointing so much off-centre, which will steer the boat as the CLR oscillates back and forth.
     
  14. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    The chines are angled down rather severely, sounds like the boat may be tripping over them when a wave pushes from the side.
    I don’t think additional chine outside the hull is the best approach to that problem.
    I think the existing chines are turned down so far that they are acting as skegs, tripping the boat as the wave moves under it.
    How about filling the chine until it becomes more of a chine flat than a skeg?
     
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  15. JanAF
    Joined: May 2018
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    Location: Stockholm, Sweden

    JanAF New Member

    I'm guessing the inertia of that relatively tall superstructure causes the problem. When the boat meets a wave the hull is slightly slowed down and veered away while the superstructure will want to continue forward in the previous direction. That would make the boat heel into the wave. At least it could contribute to such movement. Counterbalance weight would, as you noticed, help. If I'm right, reducing the superstructure weight/height would help even more. my2c.
     
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