More About "Developable" Surfaces

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  • Pub No.: 7047
Clarence E. Werback/Understanding stresses and curvatures of plywood in boat building.

by Clarence E. Werback

During the past two or three years various articles have appeared discussing the methc of designing "developable" surfaces as applied to hull form.
The intent of this discussion is to acquaint those interested in this design principle with further possibilities of its application and procedure. At the outset we should like to say that so far as we know, C. P. Burgess presented the first paper explaining the principle and method of geometrical projection involved in the development of this type of hull lines. We wish also to acknowledge the great amount of research done by Bruce N. Crandall*, who has possibly expanded the possibilities of this design principle more than any other designer and at the moment is giving the Navy Department the benefit his skill. To those not familiar with the principle let it be said in simple terms that the surfaces of the sides and bottom forms of boats designed on the principle, are segments of either cones or cylinders or combinations of both. Surfaces so developed will be free of compound curvature and hull forms will be such as to permit the application of plywood in full lengths without buckling or the necessity of steaming. In the case of steel hulls the plating can be applied cold without furnacing or working. It can seen at once that a tremendous amount of labor is saved on hulls designed around this principle. In the use of plywood there is no dress down, no seams to caulk and no sanding. Priming, and even finish coats of paint, may be applied on both inner and outer surfaces before the plywood is fastened on. Also, since there are certain stresses built up in the plywood skin because of the curvature induced as it is warped around (which should be kept within minimum bending radius set up the plywood manufacturers), frames can be more widely spaced without affecting the overall strength, of the hull structure.

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