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Thread: speed formula

  1. #1
    snappertapper
    Whats the formula for theoretical speed?

  2. #2
    Senior Member
    Join Date
    May 2010
    Posts
    109
    Try this. If you use MS Excel I can email a custom sheet I use.
    www.go-fast.com/boat_speed_predictions.htm

  3. #3
    Senior Member
    Join Date
    May 2010
    Posts
    109
    This is like the spread sheet I use in Excel.
    www.go-fast.com/Prop_Slip_Calculator.htm

  4. #4
    Toffen
    Hi!
    Pitch fx 25 inches x rpms fx 6.000 / 1056 / gear ratio fx 1.75 = teoretical speed fx 81,16 mph. Then reduce with approx. 10 % slip if fast hull.
    Cheers,
    Toffen

  5. #5
    HavasuDreamin'
    1. RPM/Gear Ratio
    2. That No. * Prop Pitch
    3. That No. /5280 /12
    4. That No. * 60
    That = Theoretical Speed with no Slip.
    5. Take off 10% slip as an average
    To find your slip take actual GPS speed/Theoretical Speed. Then take 1-that number.

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