Question 59Navigation Problems

70% to pass

If the speed necessary for reaching port at a designated time is 17.4 knots and the pitch of the propeller is 25.6 feet, how many revolutions per minute will the shaft have to turn, assuming a 3% positive slip?

A 67
B 63
C 75
D 71
AI Explanation

The correct answer is D) 71 revolutions per minute. To calculate the revolutions per minute (RPM) of the shaft, we need to use the formula: RPM = (Speed in knots x 1.6889) / (Propeller pitch in feet x (1 - Slip percentage)). Given: - Speed necessary for reaching port: 17.4 knots - Propeller pitch: 25.6 feet - Positive slip: 3% Plugging the values into the formula: RPM = (17.4 x 1.6889) / (25.6 x (1 - 0.03)) RPM = 29.4 / 0.412 RPM = 71 The other answer choices are incorrect because they do not correctly apply the formula and account for the given propeller pitch and positive slip.

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Official Resources
USCG Navigation Rules (COLREGS) 33 CFR Navigation Rules USCG National Maritime Center
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