Variable Pitch Propeller Blade Notch Design
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Solution Overview
Problem
Conventional variable pitch propellers face inefficiencies due to blade interference and difficulty in replacing damaged blades, as they lack a notch in their trailing edges, leading to compromised performance and maintenance challenges.
Innovation Solution
The design incorporates a notch in the trailing edge of each blade to prevent interference between adjacent blades during rotation, allowing for a more optimized shape that balances performance and ease of maintenance, with a larger rounded tip area for better water flow control and a more balanced blade design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If blades are designed with larger chord at hub and larger tip area to maximize surface area and thrust, then thrust production is improved, but blade interference between adjacent blades occurs during pivoting
Solution Approach 1:
The blade is segmented by adding a notch in the trailing edge that creates a discontinuity in the blade profile. This notch allows the leading edge of an adjacent blade to pass through during pivoting without interfering with the main blade structure. The segmentation enables larger chord and tip area while preventing blade interference through the created opening space.
2Strength
If threaded screws are used to secure blades to hub, then secure attachment is achieved, but blade replacement becomes difficult requiring hub disassembly
Solution Approach 1:
The attachment system is segmented into separate components: a hub aperture and a corresponding blade insert with engagement features. The blade insert can be removed from the hub aperture without disassembling the entire hub, allowing easy blade replacement while maintaining secure attachment during operation.
Solution Approach 2:
The blade attachment mechanism extracts the blade securing function from the hub structure itself, using separate inserts or fasteners that can be independently removed. This allows the blade to be detached without removing hub components, significantly simplifying replacement procedures.
3Productivity
If propeller diameter is reduced to less than 40 inches, then boat acceleration and fuel consumption are improved, but available blade surface area is reduced
Solution Approach 1:
The blade design applies local quality optimization by concentrating surface area where most effective: larger chord at the hub portion for thrust generation and optimized tip area for flow control. The notch placement and overall geometry are designed to maximize surface area utilization within the constrained propeller diameter, achieving both acceleration performance and adequate thrust surface.
Data Source
AI summary
A variable pitch propeller comprises a plurality of blades pivotally connected to a hub. Each of the plurality of blades has a base having a leading end and a trailing end. The trailing edge has a notch therein forming a discontinuity in a profile of the trailing edge. The notch is sized and shaped so as to accommodate passage therethrough of a portion of the leading edge of an adjacent blade when the blade and the adjacent blade are pivoted. A blade for a variable pitch propeller is also presented.