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Towing basin

Modeling ship resistance is done by towing a model in a towing basin. The basin, located in the basement of Norris Hall is made of reinforced concrete painted with a chemical and moisture resistant enamel. The width of the basin is 6 feet and the maximum water depth is 4 feet. The overall length of the basin is 98 feet but the first 4 feet and the last 24 feet are used for braking the carriage. The usable test length is then approximately 70 feet. There are two glass walled observation pits along the side of the tank, one located approximately in the middle of the test region and the other pit located at the starting end. The observation pit at the starting end is intended for use in the study of wave reflection and absorption.

The carriage and rails were designed and constructed by the firm of Kempf and Remmers of Hamburg, Germany and were shipped in sub-assemblies to Virginia Tech. The allowable tolerance on rail height was 0.1mm. Wedges were used to give final straight alignment of each rail. The allowable tolerance on alignment was 0.2mm. Final alignment was done optically. After final adjustments in height were made, the space between the bearing plates and the bottom of the rail was filled with concrete.

A 400 V DC motor drives the carriage through a gear reduction box. The DC power is supplied from a 220 V AC motor-generator set. A maximum speed of the carriage of 3.0 meters per second can be obtained.

The carriage braking is done automatically using trips installed at both ends. An emergency brake button is also on the console. The brake is of the magnetic clutch type and brakes the DC motor directly. The brake is applied if power to the carriage is interrupted. Braking deceleration is 0.7 meter per second per second.

Ocean Engineering undergraduate students perform two experiments in the basin. They test the resistance of both a surface ship and a submarine.

Students operating carriage and data acquisition equipment.
View from behind carriage, visible waves are reflections from side walls.