Why Did I Capsize???

Discussion in 'Boat Design' started by trimlinedale, Sep 28, 2015.

  1. trimlinedale
    Joined: Sep 2015
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    trimlinedale New Member

    Yesterday I was Captain on a 14' Chris Craft, 1947 Comet built from plans in 2009. 40hp, 2009 Evinrude outboard. 4 passengers, 1-2 foot waves. I was jumping waves, and in an instant we were upside down. No one was hurt, but everyone was terrified. Any help understanding what happened would be greatly appreciated. I am an experienced boater, educator, and boat builder. I ski and pull skiers most weekends (I am 50 years old), and as a kid, listed watercraft until they capsized...14' sailboat, canoes, rowboats, etc. When the boat flipped, I had no time to react, we were immediately upside down, and in the lake. I usually take waves at about 30 degrees, so most likely that was my angle when we rotated. FYI, I was a passenger on this boat, going a bit slower in larger waves, and the boat listed so far, I thought we were going over. The owner is inexperienced, so I thought this was operator error. I wonder if this hull design is prone to "catching an edge", like steering a rudderless wakeboard?
    Please be kind with your responses, I am humiliated. I am extremely lucky that no one was hurt, still I was captain, so take full responsibility.
    I am hoping both to learn what happened, how this boat capsized in an instant, and hopefully, use this forum to showcase my mistake, and prevent another accident.
    Thanks in advance!
     
  2. pogo
    Joined: Mar 2010
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    pogo ingenious dilletante

  3. BMcF
    Joined: Mar 2007
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    BMcF Senior Member

    I'm not familiar with your specific craft, but I had a 1953 Chris Craft Sportsman that "swapped ends" violently and without warning once. Threw a passenger out of the boat and the other two of us hard against the low side...coming very, very close to rolling over whilst executing the violent nearly-360 spin.

    After some investigation, I found the incident to be caused by:

    1. Relatively high speed; the boat had more HP installed than it had ever been delivered with originally.

    2. Wrong prop geometry causing too much stern lift.

    3. Characteristic of the hull form. (I call it "Ski boat behavior"..a flat-running hull with the ability to trim the bow in and spin the boat around within barely more than it's own length)

    My guess is that your craft ended up with too much bow immersed and too little stern...and responded much as mine did.
     
  4. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Experienced this myself on another type of boat, one moment you're shearing sideways when turning and the next it grips. The reaction is immediate. I was fortunate flipping never happened because I was aware of the characteristic and always played it safe.

    Don't worry about the humiliation. Every one gets a turn.
     
  5. trimlinedale
    Joined: Sep 2015
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    trimlinedale New Member

    Thank you!

    Thank you for your posts, as this has been heavy in my head since we flipped yesterday. My friends runabout is in my shop for repairs. I will look into the prop, and engine size for sure. As this is a small boat, my thinking is leaning towards the trim being set too low. The driver sits in the middle, so the trim was probably set for a couple. When another couple (more weight) was added to the bow, the trim should have been raised to compensate. So this would be entirely my fault...gulp!
     
  6. BMcF
    Joined: Mar 2007
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    BMcF Senior Member

    If it makes you feel any better, my changing to an entirely different prop (smaller diameter and less rake) did help. But the "rest of the solution" was simply recognition of the possibility that the hull had a speed limit. Being an inboard, there wasn't much I could do about it's running trim.
     
  7. baeckmo
    Joined: Jun 2009
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    baeckmo Hydrodynamics

    Did you flip end-over-end or sideways? If sideways (or "diagonally" for that matter) it is a result of the flat bottom with a sharp chine, combined with a tumble-home freeboard. Landing just the slightest yawed after a jump or passing a crest will cause the chine to "bite" and act as an efficient lateral plane.

    With four pax and an outboard in this small boat, the vertical center of mass is high enough to create a strong heeling torque when the sideways sliding is suddenly stopped by the biting chine.

    This is the reason that the later Hickman "sea sleds" have a chamfer, or a "positive deadrise" to their sides. The originals did not have this feature, and were notorious for throwing people overboard in turns.

    As a skipper you are responsible for the selection of heading to suit the boats behaviour, and the practice of "jumping the waves" at a 30 degree angle is not good seamanship in this kind of boat. Sorry, that has to be said, but of course we are all happy that you all escaped unhurt.
     
    Last edited: Sep 28, 2015
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I can't find a pic or drawing of the hull, but I assume it is pretty well flat bottomed, not very beamy, and maybe over-powered, and has tripped on the chine (as has already been alluded to) when being put into a turn in the choppy water. More sedate speed and conservative handling required, imo.
     
  9. Ike
    Joined: Apr 2006
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    Ike Senior Member

    Having investigated a lot of boating accidents (Hundreds?) I would have to agree with baeckmo's analysis. You had 4 adults in a 14 foot boat which depending on where they were seated, and how low in the hull the seats are, could significantly affected stability, not only side to side but fore and aft. Jump a wave and if weight is too far forward it digs the bow in and swaps ends. Move it too far aft and the stern hits first and the bow flies up in the air and can actually cause the boat to flip end for end. Also going fast enough to jump wave's in a 1 to 2 foot chop would put the boat almost airborn a some point, at which it is going to lean dramatically to one side or the other depending on the side the waves are coming from. It then "caught a chine", that is tripped over the chine on the lower side.

    Way back when I was a teen my Dad taught me to not quarter waves like that in a planing hull boat. It works ok a slow speeds, or in a displacement hull but not in a small planing hull boat moving at planing speeds.
     

  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    This boat is a typical pre '63 series warped bottom, with next to no deadrise aft (maybe a few degrees).

    [​IMG]

    They are prone to tripping, perticularly if cranking hard in high speed turns or hopping waves and taking them at odd angles on takeoff and especially landing.

    Couple these with an engine that's a fair bit heavier, than the origional 2 stokes would have weighed and a full crew load and you'll looking a one of two possible situations, the first is a chine trip (which is what I and a few others suspect) or you ran her "over center", which means she became longitudinally unstable because of her speed and/or loading. Both situations are possible and if you can describe the "event" a little better, we can pin it down. Since you rolled the boat, the trip seems most likely, though landing on a wave oddly, could have "coupled" with a few other issues causing a similar event. A 14' boat with max power and full load, is asking an awful lot from this little puppy, don't you think?
     
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