Cataraft Rowing System Proposal

Team River Rats

Team Leader – Jacob Etter

Client Liaison – Matt Ulrich

Document Coordinator / Web design – Mark Gallegos

Presented to Mr. Mark Alexander

Dec. 8, 2000

Northern Arizona University

College of Engineering and Technology

ME 476

Capstone Design

Executive Summary

Mark Alexander, a copy machine repairman and private river rafting contractor, has asked us to redesign the current rowing system for a cataraft. The cataraft allows only one person to row and so the operator is subject to fatigue. The cataraft utilizes three different strokes, forward, backward, and a combination of the two. Our goal is to design a mechanism to improve the efficiency of each stroke thereby improving operator endurance.

Problem Overview

The problem presented to us by Mark Alexander is to improve the current cataraft rowing system to improve stroke efficiency. The current cataraft design uses traditional oars mounted to the aluminum frame, and only allows for one person to row at a time. For long river trips fatigue becomes a serious factor. Our job for this project is to design a mechanism for the rowing system that will help to reduce that fatigue.

Requirements

To achieve the goal of improving the stroke efficiency of the cataraft rowing system many factors must be taken into consideration. These factors are taken into account in the requirements. The cataraft rowing system must:

· Be able to operate on waters from still to whitewater class 5

· Be reliable and have low maintenance requirements while on the water

· Reduce operator fatigue during extended periods of use

· Accommodate the forward, pulling, and counter-strokes. Improvement of the pulling stroke has been given top priority, although the other strokes cannot be compromised.

An additional project requirement is the building of a prototype for testing purposes.

Scope of Work

The work for this project will be split into phases. Research, design, build/ test are the three phases that this project will encompass. During the research phase we will conduct state of the art patent searches in order to find current designs of rowing systems. We will also interview people involved with aspects associated with our problem. For example, we will interview people in the health professions to research the muscle groups used in rowing. We will get a working idea of the current rowing system by testing the boat on water. The design phase will begin by analyzing the different designs that have been researched and created. These designs will be evaluated according to how well they meet each of the requirements. Choosing an optimal design will bring us to the build/test phase. With a frame supplied by our client we will build a prototype of our design and again test it on the water to compare it to the current system. The results of our testing will be documented and delivered to the client.

Design Philosophy and Approach

During the course of this project we will stress simplicity and reliability in our design. We will attempt to minimize the amount of moving parts that may break and disable the system. We will emphasize client communication, requesting feedback at each step of the design and build/test phases.

Proposed Design

Through research and client discussions we have found several potential solutions that we will further analyze and developed. A solution for increasing the power of the pulling stroke is to have a sliding seat like that of the Olympic sculling boats. This will enlist the use of the legs, a much stronger muscle group. This will effectively reduce the fatigue in the arms and shoulders of the operator. A possible solution for improving all strokes may be to find the optimal angle that the oar is swept through. Often times while rowing a “sweet spot” can be found where the force exerted is maximized while the resistance is minimized. We believe that we can keep the blade of the oar in the sweet spot by finding the optimal angle. This may be accomplished by a combination of a moveable seat as well as moveable oarlocks. The oars will move with the operator as he/she slides back and forth in the seat keeping the oars locked in the sweet spot. Yet another potential solution for improving all strokes is a variable pitch oar. This may be achieved by jointing the oar shaft where it meets the blade. We will then restrict the movement of the blade attempting to keep it perpendicular to the water. This may also require the use of an actuator located at the handle that the operator can trigger to restrict blade motion.

It is possible that the best design solution will be a combination of all three of the proposed designs. We feel that these designs offer the most potential for successfully meeting all of the requirements of the system. In order to analyze the design we will model the system. Modeling these designs will give us the proper knowledge of how to construct a working prototype. Success of the design will be determined by attaching the prototype to a frame and comparing it to the existing rowing system on open water. It is also our understanding that we may soon have access to computational fluid dynamic capabilities. Should we be able to effectively utilize this software we will also verify our results analytically.

The majority of the research that will take place for this project is the state of the art research. Having already accomplished the bulk of this we have been exposed to several ideas that may aid us in our design phase. Through patent searches we have found a pedal assisted rowing system that will mechanically advantage the strokes, thereby adding power and efficiency to the stroke. Another current invention is a gear train that will reverse the direction of your stroke. Through this mechanism the pulling stroke of a forward facing operator becomes the forward stroke. This adds efficiency to the forward stroke by using the stronger muscle group that is associated with the pulling stroke. A simpler idea found through this search is changing the shape of the blade. This invention is comprised of a curved blade with dimples located at various places on the blade. This effectively catches the water on the blade and increases the efficiency of the stroke. Abstracts and drawings associated with these ideas can be found in Appendix A.

Budget

The estimated amount of costs that we will accrue over the course of this project will be minimal. The costs associated with this project and the responsible parties are listed below:

· Materials for modeling, building, and testing (Cataraft frame, oars, PVC pipe, etc.) – Supplied by Mark Alexander

· Copies and phone contact – Supplied by Team River Rats

· Software, documents, e-mail contact – Supplied by Northern Arizona University

Additional negotiations can be made at later dates to accommodate for any unseen expenses that might be incurred.

Schedule

The schedule on the following page has been set forth by Team River Rats in order to outline specific tasks and dates of completion. These dates are subject to change only through unanimous agreement between Team River Rats and Mark Alexander.