You are turning 90 RPM, with a propeller pitch of 24 feet, and an estimated slip of -3%. What is the speed of advance?
• Propeller pitch speed formula: how to convert RPM and pitch (in feet) to speed through the water • Meaning of negative slip and how it changes the theoretical pitch speed • Unit conversions between feet per minute and knots (nautical miles per hour)
• First, ignore slip: what is the theoretical speed in feet per minute using RPM and pitch? • After finding feet per minute, how do you convert that to knots using nautical miles and minutes in an hour? • Once you have the theoretical speed in knots, how does a -3% slip change that number: do you increase or decrease the speed, and by what factor?
• Be sure to convert feet per minute to knots correctly using 1 nautical mile = 6076 feet (or 6076.1) and 60 minutes per hour • Apply the -3% slip to the theoretical speed, not to the RPM or pitch directly • Compare your final speed in knots with the answer choices and check which one is closest to your computed value
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