Seating and Balance

Discussion in 'Boat Design' started by justinDesign, Nov 26, 2007.

  1. justinDesign
    Joined: Sep 2006
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    Location: Grand Rapids

    justinDesign Junior Member

    I am designing a small 12 foot tunnel hull to be used by two occupants for fishing purposes. While underway the occupants are to be seated side by side near the outside of the vessel. The power for this vessel will be a surface drive outboard weighing about 200lbs. Since it is a surface drive I believe that trim for level will be less effective. I am curious as to how to disperse the weight from the center of the boat for balance underway, I’m thinking 50/50 right now, placing the occupants directly in the center of the vessel while underway. This vessel is not intended to go over 40 miles an hour, so the tunnel is basically for looks. Any suggestions on where I should seat the occupants.
  2. BWD
    Joined: Aug 2006
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    Location: Virginia, US

    BWD Senior Member

    This is no info to go on for a precise calculation, but for planing and maybe up to 40kts, I would think the CG ought to be somewhere 38-45% of the way forward from the transom. That's typical for a range of boats, anyway. It is a big range though, big diff. between 38% and 45%.
    But it sounds like you are in the neighborhood (or at least area code).
    Count on putting the gas tank fwd, maybe the battery too though, as even with 2 200 lb dudes amidships you're working from 33% if the motor's on the transom. Of course your build may pull cg fwd too, how much depends on the stuff you have not posted (shape, scantlings). Luckily on a small boat moving the battery, gas tank or your rear can fix a lot of things....

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