SNAME Chesapeake Section Examines Propeller Design

chesapeake sname

A provocative paper was presented at a recent meeting of the Chesapeake Section, The Society of Naval Architects and Marine Engineers. Pramud Rawat of Vitro Laboratories Division, Automation Industries, Inc. presented a paper on "Propeller Geometry for Design-Production Integration and Quality Control." The author maintained that the current propeller drawings furnished to the manufacturer are inadequate and ambiguous (from the manufacturer's point of view) and, therefore, cannot be used for numerically controlled machines. The manufacturer makes it his responsibility to remove the ambiguities from the supplied geometrical data. However, because in most cases the designer does not review and approve the resulting modifications, the manufacturer is exposed to the risk of rejection of the finished propeller upon inspection.

The paper also described a method by which surfaces can be defined mathematically using the designer data. The author went through the steps of representing a path on the propeller surface and the ability of the N-C machines to follow that path. The system presented is still in the theoretical stage, and the author attempted to generate sufficient interest in the shipbuilding industry in general and the propeller design/manufacturing segment in particular so that the system can be experimented with and finally brought to production usage.

Interest definitely was generated. Under the guidance of Capt.

Wilbur Ginn, USN (ret.), as moderator, representatives of Lips, Bird-Johnson, Ferguson, Hydronautics, NSRDC, and NAVSEA voiced their comments on the subject. The majority of comments centered on the practicality of adhering to the designer data, and the adequacy/inadequacy of some of the manufacturing tolerances. The meeting was concluded by the presentation of a certificate of appreciation to Mr. Rawat by t h e chairman of the Section, James Lisnyk.

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