Prof. L. A. Baier, Member:

About two years ago the writer was privileged to test a model of a typical "Canaller" in the University of Michigan Naval Tank for the author. The vessel was to be powered with a 1600-hp Diesel at a shaft rpm of 325 using a 9-ft-diam wheel. These tests disclosed certain characteristics which are probably common to this type of vessel:

1 The extremely high wake value at normal speeds of 8 to 9 knots.

2 The low propulsive coefficient due to a combination of low speed, high rpm, and excessive wake.

The PC was lower than many of the river tunnel-stern towboats. The high wake likewise adversely affects the steering qualities, necessitating large helm angles, which in turn causes a reduction in speed. The above conditions are further exaggerated in restricted waters.

The writer proposed the installation of two 24-in. pipelines to feed water to each side of the upper wheel disk. These pipes were to leaf forward and outboard to a side-shell intake. Model tests indicated a material decrease in wake with a corresponding gain in wheel and rudder efficiency. The improvement in restricted channels would be even greater. The loss in displacement was about 10 tons. As these vessels face the competition noted by the author when the Seaway is opened, the foregoing suggestion might well be considered.

Fig. 37 Feed-Pipe Installation on River Towboat

A similar twin-pipe feedwater supply was designed by the writer and fitted in the City of Joliet, a twin-screw, fort-nozzle towboat. This vessel's performance was satisfactory on the Ohio River. However, when operations were transferred to the Illinois River where the channel is considerably restricted, the RPM and speed dropped and the maneuverability pushing a flotilla became dangerously impaired. After installation of the feed pipes shown in Fig. 37, the foregoing characteristics returned to normal.

The Society is indebted to Mr. Gilmore for this valuable history of a unique fleet of busy little vessels.

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This paper was presented at a meeting of the Society of Naval Architects and Marine Engineers and is reproduced with permission.