Propeller Design Research Part 2

Date: 09/17/24 

 Meeting goals 

 

 Calculator for approximate propeller thrust given motor specifications 

 Learn how to use a simulator to simulate propeller performance 

 Compare calculator results to simulator results 

 

 Meeting Notes 

 

 Propeller thrust can be calculated using:

 

 Thrust = (Motor power * Propeller efficiency) / Flow velocity 

 Source: Propeller Performance: An introduction, by EPI Inc. (epi-eng.com) 

 

 

 Flow velocity can be calculated using:

 

 Speed (inches/minute) = Pitch * RPM * (1 - Slip) 

 Source: http://dunnritepropellers.co.nz/images/prop_tips_03.pdf 

 Factors contributing to propeller slip and how to reduce propeller slip :

 

 Boat weight and design: The weight and design of your boat can affect how much resistance the propeller encounters in the water, which can impact prop slip. 

 Engine power: If your engine is producing more power than your boat can handle, it can cause the propeller to slip in the water.  

 Propeller size and design: The size and design of your boat’s propeller can impact how efficiently it moves through the water and how much resistance it encounters. 

 Water conditions: Rough water or strong currents can increase the resistance your propeller encounters, which can lead to higher prop slip. 

 Source: How To Reduce Prop Slip: Tips and Techniques For Better Boat Performance - Waves Weekender 

 A slip of 1 or 100% means that the propeller will not advance in water. 

 "Calculated propeller slip within the 

 range of 5% to 25% is typical and acceptable. If slip is greater than 25%, there is likely an issue with the propeller."  Prop Bite: Understanding Propeller Slip | Mercury Marine 

 

 

 

 

 Propeller efficiency is related to propeller diameter. The greater the diameter, the more efficient the propeller (The propeller will be able to move more water/ produce more thrust per revolution). But the greater the propeller diameter, the more drag. So for low-speed craft, a higher diameter propeller is preferred whereas for a higher-speed propeller, a smaller diameter propeller is preferred. How Propeller Pitch and Diameter Affect Boat Performance (citimarinestore.com) 

 

 "The main opportunities for propulsion efficiency improvements are in hull efficiency (typically 0.95–1.3), propeller open water efficiency (typically 0.55–0.70) and relative rotative efficiency (typically 0.98–1.07)" Propeller Efficiency - an overview | ScienceDirect Topics 

 

 

 Selected motor: APISQUEEN 70167 7.5KW internal rotor brushless waterproof motor for hy – Underwater Thruster 

 

 What was completed? 

 

 The calculator: https://docs.google.com/spreadsheets/d/1fZU8p28u3xLca4Ge9oelJ2ioDH1f_wty5EOEaINy_YU/edit?usp=sharing 

 

 What is in progress? 

 

 Learn how to use a simulator to simulate propeller performance 

 Compare calculator results to simulator results 

 

 What is the goal for the next meeting? 

 

 Simulate a propeller and compare results with the calculator 

 

 

 Images