Force Tests of the Squid with New Afterbody, Tails and Noses

Abstract

Various modifications of the external shape, but not of overall length or diameter, of the British squid, Type "C" Projectile were tested to determine an acceptable shape having materially reduced drag and no other characteristics which would be objectionable. The best modification obtained was the simple substitution of a special nose, previously designed by Mr. A. L. Kitselman, who was then employed by the Hydrodynamics Laboratory. The contour of this special nose was determined by the formula (X/1.5)^3 + Y^2 = 1. This model appears, by extrapolation, to have a drag coefficient of about 0.106 at R = 15 x 10^6 which would correspond to a terminal velocity of about 53.6 ft/sec. Calculations indicate that this might be raised to 55.0 by using four (strengthened) vanes in the tail instead of eight. The cross force coefficient is about 10% less than that of the production model, and the stabilizing moment coefficient about 11-1/2% greater. It is believed a bourrelet could be provided without materially affecting the hydrodynamic characteristics. The tendency to cavitate with this nose is somewhat reduced but its effect on performance during the bubble stage is not known at present, or even that it may be adverse. If so, it is probable that it could be within acceptable limits.

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