I think ships can travel at fractional speeds. Use the weapon officer to plot a torpedo attack - the speed he chooses is often between whole numbers. I do the 3.15 rule and I go with the number I calculate (sum of four readings /4) as the best estimate of target speed. I think convoys have a whole number target setting (e.g. 7kts) but they can fail to achieve that speed as a function of the weather.
Kb
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