Rudder Stock Weight Reduction via Composite Segmentation
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Solution Overview
Problem
Rudder stocks for large watercraft face challenges in weight reduction while maintaining sufficient strength and flexural rigidity, particularly due to limited forging capacity and high loads from fast ships with heavily loaded propellers.
Innovation Solution
Designing a rudder stock with a lower end area made of non-metallic fiber composite material, such as carbon fiber, and optionally using a metallic upper end area, along with a support body in the lower end region to enhance strength, and potentially using a fiber composite tube design with a cavity for reduced weight and improved load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rudder stock is made entirely of forged steel to ensure sufficient strength and flexural rigidity, then the strength and rigidity requirements are met, but the weight becomes excessively high (exceeding 100 t in extreme cases)
Solution Approach 1:
The patent applies composite materials by combining metallic end sections (forged steel) with a non-metallic middle section (fiber composite material). This composite construction allows the rudder stock to maintain sufficient bending strength and torsional rigidity while significantly reducing weight. The fiber composite material in the middle section provides adequate mechanical properties without the high density of solid metal, achieving weight reduction of up to 50% compared to traditional all-metal designs.
Solution Approach 2:
The rudder stock is segmented into three distinct sections: an upper metallic end section, a middle non-metallic section, and a lower metallic end section. This segmentation allows each portion to be optimized for its specific functional requirements - the metallic end sections provide strength for bearing and connection purposes, while the lightweight middle section reduces overall weight. The segmented design also facilitates manufacturing by allowing separate production of sections with different material properties.
2Strength
If a rudder stock with large diameter is used to increase bending strength, then the strength requirements are met, but the weight increases significantly
Solution Approach 1:
The use of fiber composite materials in the middle section provides high strength-to-weight ratio, allowing the rudder stock to achieve required bending strength without increasing diameter and consequently weight. The composite material structure efficiently resists bending loads while maintaining a more favorable weight-diameter relationship compared to solid forged steel.
3Strength
If the entire rudder stock is made of forged steel, then sufficient strength is achieved, but manufacturing becomes challenging due to limited forging capacity worldwide
Solution Approach 1:
The rudder stock is divided into multiple sections that can be manufactured separately using different processes. The end sections can be produced by traditional forging methods at available facilities, while the middle section can be manufactured using fiber composite techniques. This segmentation makes the overall manufacturing process more feasible by distributing the production across different specialized facilities rather than requiring a single facility with extreme forging capacity.
Solution Approach 2:
By incorporating non-metallic fiber composite material in the middle section, the patent reduces dependence on limited high-capacity forging facilities. The composite section can be manufactured using winding or molding processes that are more widely available, thereby improving overall manufacturing feasibility while maintaining structural integrity.
4Weight of moving object
If a hybrid construction with metallic and non-metallic sections is used to reduce weight, then weight reduction is achieved, but the device complexity increases due to multiple material sections
Solution Approach 1:
While segmentation into multiple material sections does increase structural complexity, it enables the weight reduction achieved by using lightweight fiber composite material in the middle section. The segmented design allows optimization of each section for its specific function, with the metallic end sections handling bearing and connection functions and the composite middle section providing lightweight structural support.
Data Source
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AI summary
In order to achieve improved properties in a rudder stock for rudders for watercraft, at least the lower end region of the rudder stock to be inserted into the rudder and to be mounted in the rudder has a non-metallic material.