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snappertapper
01-15-2003, 05:01 PM
Whats the formula for theoretical speed?

Nokomis
01-16-2003, 10:21 AM
Try this. If you use MS Excel I can email a custom sheet I use.
www.go-fast.com/boat_speed_predictions.htm (http://www.go-fast.com/boat_speed_predictions.htm)

Nokomis
01-16-2003, 10:41 AM
This is like the spread sheet I use in Excel.
www.go-fast.com/Prop_Slip_Calculator.htm (http://www.go-fast.com/Prop_Slip_Calculator.htm)

Toffen
01-16-2003, 10:42 AM
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

HavasuDreamin'
01-17-2003, 09:03 AM
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.
:D