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Thread: Working out Center of Gravity

  1. #1

    Default Working out Center of Gravity

    Hey

    Iam a little lost when people say you have to work out the CG when mounting everything down into the boat.

    As far as what my hull says is that its 11" in from the back of the transom, now i have held it at 11" in and the boat doesnt sit straight it falls one way then the other or is this how its suppose to be?

    Also once i add all my components into the boat should the nose be heavier then the back when looking at my CG at 11", as in should the nose dip forward or should the transom be dipping back?

    Also when they say at 11" is that with all hardware on the boat?
    Do people run radio boxes or.....?

    Some help here guys would be really great.

    Thanks
    Dean

  2. #2
    Join Date
    Feb 2008
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    Va
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    4,572

    Default

    The center of gravity should really say the center of balance. The boat should be balanced front to back at this point. This is of course with everything in it including batteries. Hopefully you can use the batteries to start at this point and then adjust for or aft depending on how the boat rides in the water.
    IMPBA 20481S D-12

  3. #3

    Default

    So when the boat has all its hardware, electronics etc it should sit fairly even from front to back.

    Should the back have slightly more down force then the front when stationary in the water?

  4. #4

    Default

    It's a very importatnt thing to get right and also a fairly simple thing to do. Most hulls like around 30-33% as a starting point for the COG. Figure your hull length and divide it by 3. That will give you your starting COG (33% forward of the transom) I make a mark on both sides of the inside lip of the hatch at that point. (with boat ready to run, all hrdware/batts/etc) Hold the hull at that point with your fingertips. It sould stay level in your fingers. If it leans forward that means your COG is farther forward, if the transom tilts down it means your COG is more rearward. Hope this helps.
    FE BOATING: Less like a hobby and more like an addiction!

  5. #5

    Default

    My boat is a Mono hull its the Speedmaster 45, which is 37.5" in length.

    37.5/3= 12.5, So from the back of the transom 12.5" in is my center of gravity.

    Why on my manual it says its 11" in from the transom?

  6. #6

    Cool

    11" is 29%, in the expected average range for monos. 12.5" is 33%, also in range. Different hulls will have different CG requirements, and different speeds can require different CG values. Start with what the manufacturer recommends.

    It is not possible to say how the hull should sit in the water while static. Most monos will be a bit bow-high but it depends on the design. Put your model together with a CG 11" ahead of the transom and you should be very close to perfect.



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