Modular Propeller with Sinusoidal Blades for Reverse Thrust
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Solution Overview
Problem
Conventional propellers, such as sterndrive and outboard props, are inefficient in providing reverse thrust, which is crucial for quickly slowing down and stopping boats, especially heavy vessels like houseboats and barges, as they are primarily designed for forward thrust.
Innovation Solution
A modular propeller design featuring a center hub with replaceable blades having a symmetric hydrofoil cross-section along a full wave sinusoidal mean camber line, eliminating localized cupping on the leading or trailing edges, and incorporating a thicker root that tapers to a thinner tip, ensuring consistent hydrofoil shape and enhanced reverse thrust capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional propeller design is used, then forward thrust is optimized, but reverse thrust is poor
Solution Approach 1:
The patent applies asymmetry by creating a non-symmetric hydrofoil shape where the leading edge has a different curvature and thickness distribution compared to the trailing edge. The leading edge features a rounded profile with increased thickness, while the trailing edge tapers more sharply, creating an asymmetric geometry that generates effective reverse thrust while maintaining forward propulsion capability
Solution Approach 2:
The patent implements local quality by varying the hydrofoil cross-section at different locations along the blade. The root portion has a thicker cross-section for structural strength and torque transmission, while the tip portion tapers to a thinner profile for reduced ventilation and improved reverse thrust. This localized variation in geometric properties optimizes both forward and reverse thrust characteristics
2Force
If localized cupping is added to improve reverse thrust, then reverse thrust is enhanced, but forward speed is reduced
Solution Approach 1:
The patent applies parameter changes by systematically varying the hydrofoil geometric parameters along the blade length. The mean camber line is designed with a specific curvature distribution, and the cross-sectional thickness is varied continuously from root to tip. This continuous parameter variation creates an optimized balance between forward thrust efficiency and reverse thrust capability without the need for discrete cupping features
3Strength
If thicker leading edge is used, then durability is enhanced, but reverse thrust efficiency is reduced
Solution Approach 1:
The patent implements local quality by creating a non-uniform thickness distribution along the leading edge. The root portion has maximum thickness for structural strength and durability, while the thickness gradually decreases toward the tip. This localized variation ensures that the thicker root provides enhanced durability and torque transmission, while the thinner tip maintains reverse thrust efficiency by reducing water resistance and ventilation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modular propeller design significantly improves reverse thrust efficiency, allowing for faster boat stopping and enhanced durability, with notable gains in reverse thrust power and reduced engine strain, demonstrated by increased speed and reduced ventilation issues during testing.
Implementation Method 1
Each such blade has a symmetric hydrofoil cross-section but disposed along a full wave (360°) sinusoidal mean camber line
Data Source
AI summary
An efficient reverse-thrusting modular propeller combines a center hub and a set of identical and replaceable blades. Each such blade has a radially and laterally symmetrical hydrofoil cross-section but disposed along a full wave (360°) sinusoidal mean camber line. The blades all feature a very strong thicker symmetric hydrofoil cross-section at the propeller root which widens with a longer sinusoidal mean camber line wavelength, and thins in amplitude moving outward, and then the blades narrow again in shorter wavelength and thin more in diminishing amplitudes progressing toward the distal tip. Localized cupping on the leading or trailing edges is ruled-out as undesirable and counterproductive.