Mainsail Reefing Drum Assembly with Levelwind and LeverDisc
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Solution Overview
Problem
Existing sail reefing systems require crew members to leave the cockpit, handle long lines, and concentrate mechanical loads on a single line, posing safety and efficiency issues, especially in harsh weather conditions.
Innovation Solution
A mainsail reefing system that uses a drum assembly with coaxial drums and a levelwind mechanism to split the mechanical load between two reefing lines, allowing a single control line to operate the system from the cockpit, reducing line length and load, and incorporating a LeverDisc for increased leverage during outhaul tensioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If slab reefing is used, then the mainsail can be reefed manually, but crew members must leave the cockpit and go to the mast which is hazardous in rough conditions
Solution Approach 1:
The reefing system is divided into two separate coaxial drums: one for the luff-end reefing line and one for the leech-end reefing line. This segmentation allows independent control of each line while maintaining a unified drum assembly, enabling the crew to reef the sail from the cockpit without leaving the safe area.
Solution Approach 2:
The patent introduces an intermediary mechanism (the dual-drum assembly with levelwind) that translates the crew's single-line operation into coordinated action of both reefing lines. This intermediary eliminates the need for direct manual handling of the sail at the mast, serving as a safe mediator between the crew and the hazardous reefing task.
2Ease of operation
If conventional single line reefing is used, then the crew operates from the cockpit, but long lengths of line (almost 100 feet) must be hauled
Solution Approach 1:
By segmenting the reefing function into two separate lines handled by two separate drums, the system reduces the amount of line that needs to be hauled. Each drum collects its respective reefing line independently, allowing the crew to operate with shorter line lengths compared to single-line systems that require hauling nearly 100 feet of line.
Solution Approach 2:
The patent adds a dimensional element by using two coaxial drums rotating in opposite directions. This dual-drum configuration creates a new operational dimension where both reefing lines are managed simultaneously through a single control mechanism, fundamentally changing how line length is managed compared to traditional single-line systems.
3Device complexity
If conventional single line reefing is used, then the system is simple, but the entire mechanical load is placed on a single line which may fail
Solution Approach 1:
The mechanical load is segmented and distributed across two separate reefing lines, each handled by its own drum. This segmentation prevents the concentration of entire mechanical loads on a single line, thereby improving reliability and reducing the risk of line failure while maintaining relatively simple system architecture.
Solution Approach 2:
The patent changes the load distribution parameter by transitioning from a single-line system (100% load on one line) to a dual-line system where the load is divided between two lines. This parameter change fundamentally improves the reliability of the reefing system without requiring complex multi-component mechanisms.
4Device complexity
If in-mast reefing is used, then the sail can be rolled inside the mast, but sail battens must be eliminated which causes performance loss
Solution Approach 1:
The patent extracts the reefing mechanism from within the mast structure and relocates it to the boom area with the drum assembly positioned at the aft end of the boom. This extraction allows the mainsail to retain its full structure including battens, thereby maintaining optimal aerodynamic performance while still achieving effective reefing capability.
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 system enables safe, efficient, and cost-effective reefing by minimizing line length, distributing mechanical loads, and providing increased leverage for proper sail shape maintenance, enhancing crew safety and sail performance.
Implementation Method 1
A levelwind mechanism is provided including a cam shaft converting rotational motion to reciprocating motion
Implementation Method 2
a larger diameter threaded disc coaxially attached to an end of the third drum. During the reefing process a cockpit line is pulled off the third drum and then transitions to the larger diameter threaded disc, providing extra leverage during the outhaul tensioning of the mainsail
Data Source
AI summary
A mainsail reefing system comprises: a drum assembly including first and second coaxial drums for collecting luff-end and leech-end reefing lines, respectively; a drive mechanism for rotating the drum assembly; and a levelwind mechanism including a cam shaft configured to convert rotational motion to reciprocating motion, and first and second line guides mechanically coupled to the cam shaft, where the line guides are configured to move in a reciprocating motion across the width of the first and second drums, respectively, for guiding the reefing lines onto their respective drums. The levelwind mechanism is mechanically coupled to the reefing mechanism for coordination of movement of the line guides with rotation of the drum assembly. A preferred drive assembly comprises a third drum attached coaxially to the first and second drums, and a larger diameter threaded disc coaxially attached to an end of the third drum. During the reefing process a cockpit line is pulled off the third drum and then transitions to the larger diameter threaded disc, providing extra leverage during the outhaul tensioning of the mainsail.