The propeller on your vessel has a pitch of 18'09". If the observed distance for a day's run was 399.4 miles and the average RPM was 86, which statement is TRUE?
• Propeller pitch as theoretical advance per revolution (in feet) • Converting feet per revolution and RPM over 24 hours into theoretical distance in nautical miles • Formula for propeller slip % based on theoretical vs observed distance
• First, convert 18'09" of pitch into feet, then into nautical miles per revolution. How many feet is 9 inches? • Over one day (24 hours), how many total revolutions does the propeller make at 86 RPM, and what theoretical distance does that give? • Compare the theoretical distance from RPM with the observed 399.4 miles: is the vessel going farther or shorter than the theoretical distance, and what does that say about slip sign and approximate percentage?
• Be clear whether you are working in nautical miles and use the correct feet-per-mile conversion consistently (check your exam standard: often 6,000–6,080 ft per NM). • Check that your total revolutions use 24 hours × 60 minutes × RPM (if RPM is in revs per minute). • After computing theoretical distance, compute slip as (theoretical − observed) / theoretical × 100% and see which answer choice matches both the sign (positive/negative) and the magnitude (about 5%) or the corresponding "day's run by engine RPM".
No comments yet
Be the first to share your thoughts!