Marine Rudder Assembly Separate Casting Interference Fit
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Solution Overview
Problem
Conventional rudder assemblies face challenges in achieving a precise wake-adapted shape and maintaining structural integrity due to issues with fairing compound failure, bond degradation between composite and steel components, and copper-contamination-cracking in bronze alloy casting methods.
Innovation Solution
A design where the rudder stock and blade are manufactured separately and assembled with a high-strength stainless steel and bronze alloy, featuring a tapered and twisted configuration with an interference fit and epoxy-like cement injection for enhanced bonding and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If fairing compound is applied to achieve smooth wake-adapted shape, then surface smoothness is improved, but reliability deteriorates due to cavitation erosion and bonding failure
Solution Approach 1:
The patent removes the fairing compound layer entirely and instead achieves the wake-adapted shape through precision casting of the metal rudder blade itself. The casting process directly forms the twisted, wake-adapted contours without requiring any external fairing material, thereby eliminating the bonding interface that would fail under cavitation and cyclic loading.
Solution Approach 2:
The invention changes the material state from composite (metal + fairing compound) to monolithic metal casting. By utilizing precision casting techniques, the rudder blade is formed with the exact wake-adapted geometry directly in the metal substrate, transforming the surface finish achievement method from post-manufacturing fairing to in-process geometric control.
2Ease of manufacture
If composite materials are used to achieve wake-adapted shape, then manufacturing flexibility is improved, but reliability deteriorates due to bond degradation under cyclic loads and vibration
Solution Approach 1:
The patent employs a homogeneous metal construction throughout the rudder blade, eliminating the composite structure that creates bonding vulnerabilities. The entire blade is cast as a single piece of metal with consistent material properties, removing the interface between different materials where bond degradation would occur under vibration and cyclic loading.
Solution Approach 2:
While the patent ultimately rejects composite materials for the final structure, it acknowledges the manufacturing flexibility they provide. The solution is to achieve the same geometric flexibility through precision metal casting techniques, thereby obtaining the wake-adapted shape without the reliability penalties of composite bonding.
3Reliability
If direct casting of bronze alloy is used to eliminate copper-contamination-cracking, then reliability is improved, but manufacturing precision deteriorates due to cracking during casting and cooling
Solution Approach 1:
The patent changes the material composition by using a stainless steel rudder stock instead of bronze alloy, thereby eliminating the copper-contamination-cracking issue entirely. The stainless steel material properties allow for precision casting without the cracking problems associated with bronze alloy cooling and contraction.
4Manufacturing precision
If rudder stock and blade are manufactured separately and assembled, then manufacturing precision is improved, but device complexity increases due to additional assembly steps
Solution Approach 1:
The patent divides the rudder assembly into separate castable components (rudder stock and rudder blade) that can be manufactured with high precision through casting. The segmentation enables each component to be optimized and manufactured independently, then assembled through a controlled interference fit process that maintains overall precision while benefiting from modular manufacturing.
Data Source
AI summary
A system for designing and assembling a ships rudder that allows for the manufacture of the rudder components, namely a rudder stock and rudder blade independently, and assembling them into a completed rudder using retaining bolts and injecting an epoxy like cement or grout in order achieve the required strength characteristics.