from www.Hobiecat.com

Design of a Tow Tank Dyno for Foil Efficiencies

Background:

The University of Maine’s Mechanical Engineering Department has been working since the Fall of 2001 on a submarine for a national student competition. Design groups from previous years have purchased two MirageDrives from Hobie, a famous sailboat manufacturer who has been building kayaks for a number of years. Each drive consists of two pedal-powered oscillating hydrofoils. This project is the first attempt to consider the efficiency of the hydrofoils and to help to predict the performance of the human powered submarine. Because this is a design competition, the prediction of the efficiency is a critical aspect of the overall project.

The University of Maine owns a medium size research tow tank which is located in the basement of the Aquaculture Research center building behind the Maine Bound Barn. This is a quite unique opportunity to have access to a facility such as the tow tank since it allows students to have unfettered access to a unique facility. However, some of the instrumentation is a bit dated and may not be sufficient for the required testing. The first order of business will thus be to develop the components of the two tank needed for the testing, with additional work focused on the use of the tow tank for other projects to develop the skills needed to test the foils.

A new set of foils will then be used to provide the oscillating system that can then be used to characterize the efficiency of the drive system. The foils are shown below removed from the boat from the Hobie web site. The primary goal will be to measure the thrust at several advance ratios in order to determine the ideal pedaling frequency. Parameters to be investigated include frequency, forward speed, and foil sweep angle. Torque and foil position should be measured as well so that efficiency can be computed. The torque and position measurements are more difficult but allow the comparison of the Mirage Drive with conventional propellers and existing data on oscillating foils.

Milestones

-Design specifications including range and sensitivity of sensor thrust: September 28^th-Design specifications including range and sensitivity of sensors for torque and position: October 5th
-Instrumentation selection for foil carriage: October 12^th-Website up and running: October 12^th-Design specifications for torque and rotational rate for motor: October 19th
-Run ball on stick in tow-tank: October 24th
-Drawing package for dyno mechanical components and parts list: October 26^th-Purchase order requests submitted for instrumentation on foil mount: October 31^st-Purchase order complete for foil drive motor: November 3^rd-Drawing package for foil mount & drawing package for foil drive motor with gear assembly and linkages: November 14^th-Purchases order requests for mechanical parts complete: November 16^th-Build dyno: December 7^th-Dry test dyno mechanical parts: December 14^th

Proposal for modified milestones and initial deliverables: September 15, 2006
Design specifications for dynamometer includes determining range of sensor and sensitivity get thrust, torque and foil position: :
Instrumentation selected for dynamometer: September 26, 2006
First web page goes live with introductory page and menu on left. Page must include resumes, individual photos and milestones: October 12, 2006, 2 pm.
Drawing package for tow tank dyno : October 19, 2006
Drawing package for the foil mount to the carriage and motor linkages with instrument list: October 20, 2006.
Instrumentation purchase OK'd for tow tank dyno: October 26, 2006
Milestone review: November 7, 2006
Tow tank dyno dry test completed: November 16, 2006
Drawing package for foil mount completed: November 23, 2006
Tow tank dyno installed and operational: November 30, 2006
Draft Midterm Report: December 5, 2006
Material orders completed for foil mount.
Lab Cleanup: Maine Day, May 2, 2007
Open House -- Review of Projects, May 3, 2007

Hard Milestones (more to be added):

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