International Shipbuilding Progress - Volume 8, issue 82

Authors: Gerritsma, J. | van den Bosch, J.J. | Beukelman, W.

Article Type: Research Article

Abstract: With a model of a combined passenger and cargo ship extensive resistance and propulsion tests were carried out in still water, as well as in regular and irregular longitudinal waves. The results of these experiments indicate that the mean increases of resistance, thrust, torque, r.p.m. and power, for constant speed and wavelength, vary with fair approximation as the square of the waveheight. The experiments confirm that the mean increase of power due to irregular head seas can be determined when the wave spectrum and the mean increase of power in the regular wave components is known. The …increase of ship power in seawaves, as predicted from model test results is in good agreement with service performance data. Show more

DOI: 10.3233/ISP-1961-88201

Citation: International Shipbuilding Progress, vol. 8, no. 82, pp. 235-247, 1961

Authors: Swaan, W.A.

Article Type: Research Article

Abstract: The behaviour of 15,000 tons displacement vessels in unidirectional irregular head- and bow seas has been determined with the aid of experiments in regular waves. With an assumed wave spectrum the heaving and pitching motions, and the power necessary to obtain a speed of 15 knots, have been calculated. The effects of changing the block coefficient, the length-draft ratio and the length-beam ratio are presented separately as a function of the ship length.

DOI: 10.3233/ISP-1961-88202

Citation: International Shipbuilding Progress, vol. 8, no. 82, pp. 248-254, 1961

Authors: van de Voorde, C.B.

Article Type: Research Article

Abstract: Observations of the cavitation phenomena on a full scale propeller and rudder and noise measurements have been carried out on board a ship. The results of these tests are compared with those of model tests in the cavitation tunnel with flow regulator. A description is given of the apparatus for photographing underwater the full scale propeller and rudder.

DOI: 10.3233/ISP-1961-88203

Citation: International Shipbuilding Progress, vol. 8, no. 82, pp. 255-266, 1961

Authors: Baier, L.A.

Article Type: Research Article

Abstract: The familiar type and proportions of Great Lakes cargo vessels differ from ships operating on ocean waters due to dimensional limitations peculiar to inland water transportation. Lock sizes; available dry dock capacity; river, channel and port depths; maneuvering ability in harbors and rivers; seasonal operation averaging about 245 days per year; are all restrictive factors forcing the designer to adopt dimensions somewhat abnormal for optimum construction costs. Length overall of 730 ft. and beam of 75 ft. are the present maximum dimensions specified by the St. Lawrence Seaway operation. Draft, which is the least costly dimension, is currently limited …by project channel depths of 27 ft. The effect on construction costs by the above restrictions is reflected in the ratio of hull block cubic to hull surface, i.e., cargo capacity to hull structural cost. For example: Ocean ore carrier … Relative bulk/surface = 14.94 Great Lakes ore carrier    „    „    „ = 12.50 A further direct handicap affecting the operating costs on the Great Lakes waterways is the continuing diversion of water from Lake Michigan by the City of Chicago for sewage disponal. Surveys indicate Lake Huron is ultimately lowered 1 inch per 1000 cu.ft./sec. diversion to other continental drainage regeons. Lakes Erie and Ontario suffer about ( 5 / ( 8 inch level drop for the same unit diversion. The above artificial loss of water results in a corresponding decrease in loading drafts for the larger Lake carriers. The tons/inch of lighter draft, and hence cargo, runs from 50 to 113 long tons per ship. The potential loss in operation income equals: tons/inch of a given ship × inches of lowered lake level × number of trips/season × freight rate/ton, and represents a potent factor unfavorable to the economy of lake transportation. Show more

DOI: 10.3233/ISP-1961-88204

Citation: International Shipbuilding Progress, vol. 8, no. 82, pp. 267-275, 1961