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