Surfboard Fin Shear Bolt Design for Damage-Free Detachment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fin designs for surfboards and boats fail to securely detach from the board or boat without damaging when subjected to excessive forces in any direction, particularly during normal travel, leading to potential damage and time-consuming repairs.
Innovation Solution
A shear bolt with predetermined breaking points is used to couple the fin head and fin blade, providing a form-fitting, rigid connection that allows non-destructive separation under excessive forces while maintaining stability during normal operation, and a safety cable ensures the fin remains attached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an elastic connection is used between fin head and fin blade to allow pivoting under lateral forces, then damage to fin and surfboard is reduced, but the fin pivots sideways during normal surfing losing steering function
Solution Approach 1:
The connection between fin head and fin blade is segmented into a rigid portion and a detachable shear bolt portion. The shear bolt acts as a separate sacrificial element that can break under excessive force, while the main structural connection remains rigid to prevent unwanted pivoting during normal operation.
Solution Approach 2:
The shear bolt is designed as a disposable sacrificial element with predetermined breaking points. It is intended to break under excessive lateral forces to save the expensive fin and surfboard, while the main rigid connection structure remains intact and reusable.
2Object-affected harmful factors
If a hinged coupling is used to allow fin to pivot sideways under transverse forces, then some damage protection is achieved, but diagonal forces prevent the fin from being lifted upwards
Solution Approach 1:
The connection system is segmented into a rigid structural connection and a separate shear bolt with breaking points. This segmentation allows the structure to respond differently to various force directions - rigid against diagonal forces while allowing controlled failure under excessive lateral forces.
Solution Approach 2:
Different parts of the connection have different mechanical properties. The shear bolt has localized weak points with lower strength, while the main connection structure maintains high strength and rigidity. This local quality difference enables selective failure modes based on force direction and magnitude.
3Object-affected harmful factors
If attachment methods effective against direction of travel forces are used, then fin detachment without damage is achieved, but these methods are not effective for forces in other directions
Solution Approach 1:
The shear bolt connection provides universal protection against forces from any direction. The breaking points are positioned and oriented to withstand lateral forces, while the rigid connection structure handles diagonal and longitudinal forces, creating a multi-functional protection system.
Solution Approach 2:
The connection system combines materials and structures with different mechanical properties - the shear bolt material is designed to fail at a predetermined load, while the fin head and fin blade materials are designed to be stronger and more damage-resistant, creating a composite protection system.
4Reliability
If a rigid connection is used between fin head and fin blade, then steering function is maintained during normal travel, but damage occurs to fin or surfboard when excessive force is applied
Solution Approach 1:
The rigid connection is segmented by introducing a shear bolt with predetermined breaking points. This creates a weak link in the otherwise rigid structure, allowing controlled failure under excessive force while maintaining rigidity during normal operation.
Solution Approach 2:
The shear bolt with predetermined breaking points serves as a pre-prepared sacrificial element that absorbs excessive forces before they can damage the expensive fin or surfboard. This cushioning effect is built into the design beforehand.
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 fin effectively detaches from the board or boat under excessive forces without pivoting or causing damage, ensuring easy repair and maintaining control during normal travel, while preventing loss of the fin blade.
Implementation Method 1
A shear bolt with predetermined breaking points is used to couple the fin head and fin blade, providing a form-fitting, rigid connection that allows non-destructive separation under excessive forces
Implementation Method 2
a safety cable ensures the fin remains attached
Data Source
Figure 1~2b
Figure 3~4
Figure 5~7
AI summary
The fin for surfboards has a fin head (2) and a fin blade (3), which are connected to one another by means of a shear bolt (4) inserted into bores (14, 15, 23) of the fin head (2) and the fin blade (3). The shear bolt has at least one predetermined breaking point (27, 28). The fin head (2) and fin blade (3) are rigidly connected to one another with positive locking.