Dr. S. T. Mathews, Associate Member:

As the other discussers have said, we are grateful to Mr. Gilmore for this very complete record of the canal-type vessel and its operation.

All developments in the canal system, from the humble beginnings in 1680 up to the present, have led to the St. Lawrence Seaway. That the canal type of vessel will be replaced by the larger vessels it will be possible to accommodate would seem to be true from the economy associated with the larger vessels.

As naval architects, when considering a ship design, we cannot, of course, neglect the hydrodynamical aspects; and that has not been emphasized too much in this paper with regard to the canallers. To a large extent these hydrodynamical aspects are independent of size, and knowledge gained, whether from models or fullscale vessels, applies providing forms are similar.

One feature in common to all canallers-and indeed lakers-is the high block coefficient of this type; and doubtless this will be perpetuated in many of the new seaway designs. The length-over-beam and beam-over-draft ratios are not so very different. And in this connection I should like to make a plea for the extension of the Taylor Model Basin Series 60 lines to include these forms.

The main problems associated with these forms are maneuvering at slow speed, and the everpresent desirability of reducing fuel costs.

Mr. Gilmore mentioned that active rudders have been proposed, but not as yet fitted. It seems to me that there is still a future for their application in the Seaway vessels. Also, in connection with Diesel drives, possibly variable-pitch propellers will be of some use to improve maneuverability.

Regarding fuel costs, I have heard it said recently that today speed and power are relatively cheap; that is, in connection with other operation costs. This may well be the case; however, many goods are cheaper today than a few years ago but, in general, people do not purchase these items from the most expensive sources.

A good design is one where the displacement is carried at the designed speed with the minimum power which is practical. Owing to their relatively slow speed and large size, lake vessels are the most economical vessels in the world with regard to fuel consumption. However, if attention is not paid to good design of stern lines - and I am sure it has in many cases, although we have tested a few models where this does not apply - large penalties will be incurred with regard to fuel cost; and generally I mean more than 20 per cent.

The reason for this is two-fold. It is not due to wake, because a propeller working at high slip can be more economical for a given thrust. Resistance and thrust deductions are high owing to the blunt afterbodies; the thrust is increased from both these causes, and the power is approximately proportional to the thrust, raised to the power of 1.5.

I will be pleased to have the author's comments on some of these matters.

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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.