Boat leans to the port side

Discussion in 'Powerboats' started by agr, May 11, 2008.

  1. agr
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    agr New Member

    I have recently purchased a small 17" ski boat with a 350 Chev in it. It goes very well but it leans to the port side once it is on or above half speed. (i.e. on the plane) If you let go of the steering wheel it pulls to the left also.

    The boat has a small anti-cavitation plate. Could this be the reason for the lean to the left hand side ?
     
  2. TeddyDiver
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    TeddyDiver Gollywobbler

    It's the propeller effect.. At planing speeds the waterline beam comes narrower and that increases heeling. Get trim tabs to compensate...
     
  3. agr
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    agr New Member

    Thanks for your advice. I'll read up on the subject.

    What are trim tabs and where do I locate them ?

    Thanks:)
     
  4. TeddyDiver
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    TeddyDiver Gollywobbler

    Adjustable plates at the the transom. Every boating shop sells them..
    Google "trim tibs"
     
  5. PAR
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    PAR Yacht Designer/Builder

    Don't bother with trim tabs on a boat that size, they'll cost as much as the whole boat, if it has any age. Buy a "DoelFin" or "StingRay" hydrofoil and mount it on your ventilation plate (the flat piece of plate sticking out and above the prop. It's a fraction of the cost of tabs and will provide more control.

    If she's still steering left a lot, then adjust the zinc tab, usually found just above and behind the prop. This will address the torque steer problem. It can't get rid of all of it, but will make it much better once adjusted properly.

    If you still have issues, then you can use tabs, but I suspect if things are trimmed right and the anode is canted properly, then most of your troubles will go away. A good set of trim tabs is $500, while a StingRay XPII is about $70.
     
  6. Willallison
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    Willallison Senior Member

    Paul - I suspect he's talking about a shaft-driven boat, rather than a sterndrive. But as an aside, it's quite remarkable the effect those fins can have on a boat's handling. I installed one onto the leg of my old 27ft Searay and I saw a marked improvement in low-speed planing ability and dynamic stability on the plane.
    In terms of ski boats, I've seen it completely eliminate torque-steer from one boat. Then again on another it had no effect whatsoever.
    Based on nothing more than my own anecdotal obsevations, they seem to give the most marked improvement on heavily laden boats &/or those with the LCG/LCB located a fair way aft.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Will, you're right I was assuming it was an I/O in a boat that size. A small block Chevy in a 17' as a straight shaft, makes for a pretty cozy ride with the engine.

    A lot depends on the type of Hydrofoil they use, with the DoelFin working well on moderate speed boats while the StingRay (and others) seem better suited to higher speeds, like this boat might get rumbling to.

    Agr, it would be necessary to clarify what type of drive you have. A straight shaft arrangement would require tabs, though a well placed shingle, may be all you need.
     
  8. Willallison
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    Willallison Senior Member

    Yes - sorry - an all my ramblings I never addressed the issue at hand....
    As TeddyDiver doesn't know what trim tabs are, I suspect he is unlikely to know what a shingle is.....
    Essentially you would add a small wedge to the bottom of the boat on the port side. It doesn't need to be very big - and is possibly best left to someone with some experience in curing ill performing boats....

    Paul - have you ever seen the equivalent of sterndrive anode (only not a zinc) placed in way of the prop-wash of an inboard for this kind of thing? I haven't... no doubt its been done before, though I guess with the down-angle of the shaft and prop clearance issues, it would need to be quite large to effectively enter the prop-wash....
     
  9. PAR
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    PAR Yacht Designer/Builder

    Not really Will, though I have heard of some old timers using tear drop anodes on the starboard side of the rudder only, to effectively create similar. I'm not sure how well this would work, but the concept suggests it might. I have shingled boats and you're right it usually takes only a 1/2" shingle to make a huge difference in the trim out.
     
  10. TeddyDiver
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    TeddyDiver Gollywobbler

    :D
    However I'd like to know that shingle:confused:
     
  11. PAR
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    PAR Yacht Designer/Builder

    I'm not sure what's with the comment from Will, which I suspect is something you both know, but we don't. A shingle is just as it sounds and a shingle is tacked to the offending under side of the hull, right at the transom edge. It creates a "hook" which will add some lift to this portion of the hull, correcting a trim issue. With wooden hulls we'd tack literally a cedar shingle to her butt. With 'glass boats foam, plywood or just laminate is built up and shaped in the area needed. It's trial and error thing, but you can nail a trim issue down in an afternoon's efforts.
     
  12. Willallison
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    Willallison Senior Member

    Oops! Sorry TeddyDriver - I was actually talking about agr, the original poster, who asked what trim tabs were....
     

  13. TeddyDiver
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    TeddyDiver Gollywobbler

    Thanks PAR!
    No fence taken Willallison:D You happened to be half right anyways. And I think me and my ego can live with it..
     
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