P14032: Skipper's Chair
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Systems Design

Table of Contents

SLDR_Documents directory.

Benchmarking

The following pdf was sent from Piers Park Sailing. It contains information on currently implemented adaptive sailing devices:

Piers Park Adaptive Sailing Devices

The following chart contains a comparison between current Adaptive Sailing Devices at Piers Park and RIT's Skipper Chair:

Piers Park Comparison Chart

The main purpose is to compare functionality of all alternatives with the P12032 Senior Design Iteration. The reason these weren't compared to P13032, was because that iteration could not steer the boat, eliminating an important function for a successful design.

Concept Development (generation, improvement, selection)

Feasible concepts were brainstormed during the concept developmental stage. From the various ideas, only a few are presented below. These represent designs from which the final model was built:

Concepts
Sonar Figure 1: Rope Course Concept

Sonar Figure 1: Rope Course Concept

Figure 2: Tiller Strut Rope Course Concept

Figure 2: Tiller Strut Rope Course Concept

Figure 3: Jack Concept

Figure 3: Jack Concept

The 'Jack Concept' was one that was considered when looking into alternatives for the bolt sub-assembly that had kept the pedestal base secure. Ideally, these jacks would be lightweight/portable, making them easy to install and remove for each use. This option would also allow us to cut down on the size of the current plywood portion of the pedestal base.

Figure 4: Chair Securement Concept 1

Figure 4: Chair Securement Concept 1

Figure 5: Chair Securement Concept 2

Figure 5: Chair Securement Concept 2

Figure 6: Chair Securement Concept 3

Figure 6: Chair Securement Concept 3

Figure 7: Steering Design Concept 1

Figure 7: Steering Design Concept 1

Figure 8: Steering Design Concept 2

Figure 8: Steering Design Concept 2

Figure 9: Steering Design Concept 3

Figure 9: Steering Design Concept 3

The pictures above show the securing and steering concepts that were considered.

In terms of securing the user, customers at Piers Park desired a minimally invasive form of individual securement to safely constrain the individual in the seat. With this in mind, Piers Park Sailing can implement readily-available attachment straps. Systems with over-engineered securement methods give a sense of imprisonment, thereby, preventing the user from enjoying the sailing experience. This design will constrain the user, while still allowing them to experience a sense of freedom. This is part of the experience that Piers Park wants to sell, therefore, this would be a good fit for that philosophy.

The 5-point harness and 'double-strap' concepts were either too bulky or limited the individual's range of movement.

Figure 10: Tractor Chair

Figure 10: Tractor Chair

For the steering device, implementing the currently used Tractor Seat Design (seen above) was the best course of action. This design stood out due to the following:

Functional Decomposition

The main purpose of this Chart was to help identify the means by which an individual would steer the boat as well as how that would be accomplished with the proposed design.

From top to bottom, the chart represents the primary function of the design, "Allow Disabled Sailor to Steer Boat." Each sub-function represents how the sailor will accomplish the tasks above. The deepest levels support why the previous functions are necessary.

Figure 11: Functional Decomposition Chart

Figure 11: Functional Decomposition Chart

Feasibility

Jack Compressive Forces


The primary purpose of the Jack Compressive Force analysis, is to determine how much force the Jack systems will need to exert on the Sonar sides to prevent the system from moving bow-to-stern.

Using a dynamics approach, Skipper Chair System and Sonar FBD's were evaluated. Two equations were derived from the FBD's. Combining them, the equation was solved for the compressive force.

The following image shows the FBD's and calculations, as well as the final dynamic equation:

Figure 12: Jack Compressive Force Hand Calculations

Figure 12: Jack Compressive Force Hand Calculations

Analysis was done for a dry condition situation and a wet condition situation. For the dry condition, a static coefficient of friction between rubber and dry concrete (0.6) was used. For the wet condition, a static coefficient of friction between rubber (0.45) and wet concrete was used. These coefficients estimate values of rubber against fiber glass.

The following assumptions were made:

Compressive Graphs
Figure 13: Jack Compressive Forces onto Dry Sonar sides

Figure 13: Jack Compressive Forces onto Dry Sonar sides

Figure 14: Jack Compressive Forces onto Wet Sonar sides

Figure 14: Jack Compressive Forces onto Wet Sonar sides

The following image shows Matlab's compressive force output for each jack under a dry and wet condition analysis. For both the ideal and slippery conditions, the force is ~192 lbf:

Figure 15: Matlab Numerical Force Values

Figure 15: Matlab Numerical Force Values

The red lines on each graph represent compressive load values under average accelerations. A rough approximation of this acceleration determined the force exerted on the Sonar. Assuming a Sonar takes 15 seconds to accelerate from 6-7 knots, the acceleration is 0.0686 m/s^2. Multiplying this acceleration by the Sonar mass (950 kg), results in an average 65N acting on the Sonar.

The following shows the Matlab code used to obtain the graphical results:

Figure 16: Matlab Code

Figure 16: Matlab Code

An prove the validity of the jack system, an Ansys software analysis is completed on the Detailed Design page.

Risk Assessment

Figure 17: Risk Management

Figure 17: Risk Management

Figure 18: Risk Management Severity and Likelihood Key

Figure 18: Risk Management Severity and Likelihood Key

Systems Design Review

System Design Review (ppt)

System Design Review (pdf)


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