Sacrificial Propeller Blade Tip for Marine Erosion

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Solution Overview

Problem

Marine hovercraft propeller blades suffer frequent damage due to blade tip erosion and 'green water' events, leading to costly and time-consuming repair procedures, with existing protective measures failing to effectively mitigate these issues.

Innovation Solution

A blade system featuring a thin sacrificial tip attached to the base blade assembly, designed to break off under stress, minimizing damage to the propeller and supporting structure, and allowing for quick and inexpensive replacement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a protective layer is attached to blade tips to protect from erosion, then blade tip protection is improved, but attachment difficulty increases and aerodynamic disruption occurs

Engineering Contradiction:

Improveblade tip erosion protectionVSAvoidattachment difficulty

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The blade tip is segmented into a removable sacrificial tip portion and a main blade portion. The sacrificial tip can be attached and detached independently, allowing easy replacement without affecting the entire blade. This segmentation resolves the attachment difficulty by making the protective element modular and interchangeable.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sacrificial tip is designed as a disposable or replaceable component that can be easily attached and detached. When the tip becomes eroded or damaged, it is replaced rather than repairing the entire blade, reducing maintenance costs and time while eliminating the need for complex protective layer attachments.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Weight of moving object

If the blade tip is made thin to reduce weight, then weight reduction is achieved, but structural strength decreases making it susceptible to damage

Engineering Contradiction:

Improveblade tip weightVSAvoidblade tip strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The blade employs local quality by making the tip portion thinner and lighter while keeping the root and main body thicker and stronger. The sacrificial tip is designed with appropriate local thickness to provide aerodynamic efficiency and reduced weight, while the main blade retains sufficient strength to handle structural loads.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The sacrificial tip acts as a cushioning element that absorbs impact loads before they reach the main blade structure. In green water events or when hitting debris, the tip breaks or detaches first, protecting the expensive main blade and hub assembly from damage.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Strength

If the blade tip is made thicker to increase strength, then structural strength is improved, but aerodynamic efficiency decreases and weight increases

Engineering Contradiction:

Improveblade tip strengthVSAvoidaerodynamic efficiency

Core Design Contradiction:

StrengthVSUse of energy by moving object

Solution Approach 1:

The blade design applies local quality by varying the thickness distribution along the blade span. The tip portion is optimized with thinner sections for aerodynamic efficiency, while the root section has greater thickness for structural strength. This gradient design eliminates the need for uniformly thick blades that would compromise aerodynamic performance.

Inventive Principle:

Principle #3Local quality

4Reliability

If the entire propeller blade is replaced when damaged, then complete blade replacement ensures structural integrity, but repair time and cost increase significantly

Engineering Contradiction:

Improveblade structural integrityVSAvoidrepair time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The blade is segmented into a main blade assembly and a separate sacrificial tip. This segmentation allows the tip to be replaced independently without replacing the entire blade, reducing repair time and cost while maintaining the structural integrity of the main blade through proper fastening of the new tip.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sacrificial tip is designed to be discarded when damaged and replaced with a new tip. The main blade assembly is recovered and reused, eliminating the need to discard and replace the entire expensive blade assembly. This approach significantly reduces maintenance costs and downtime.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS8118562B2Sacrificial blade tip

Publication Date: 2012.02.21 HAMILTON SUNDSTRAND CORP

AI summary

A propeller blade device used in environments where a propeller system is subjected to blade erosion and wear and may also be subjected to an axial force from water. The propeller blade includes a blade tip mounted on its outer end using a mounting device such as nuts and bolts to form a junction there between. The tip may easily be replaced when worn or damaged without removing the blade. The tip is designed to fracture upon impact with an axial force before transmitting the force radially inward to the propeller blade.