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National Advisory Committee for Aeronautics, Report - Aerodynamic Characteristics of a Refined Deep Step Planing Tail Flying Boat Hull with Various Forebody and Afterbody Shapes

Because of the requirements for increased range and speed
in flying boats, an investigation of the aerodynamic charac-
teristics of flying—boat hulls as affected by hull dimensions
and bull shape is being conducted at the Langley Aero-
nautical Laboratory. The results of one phase of this
investigation, presented in reference 1, have indicated that
hull drag can be reduced without causing large changes in
aerodynamic stability and hydrodynamic performance by
the use of high length—beam ratios. Another phase of the
investigation, reference 2, indicated that hulls of the deep-
step planing-tail type have much lower air drag than the
conventional type of bull and about the same aerodynamic
stability; tank tests, reference 3, have indicated that this
type of hull also has hydrodynamic performance equal to and
in some respects superior to the conventional type of hull.

In an attempt to improve the aerodynamic performance of
hulls still further without causing excessive penalties in
hydrodynamic performance, several refined deep~step planing-
tail bulls were designed jointly by the Hydrodynamics
Division and the Stability Research Division of the Langley
Laboratory. It was behaved that improved aerodynamic
performance could be facilitated mainly by refinement of the
forebody plan form and by a reduction in the volume and
surface area of the, afterbody. This report presents. the
results of the tests of these hulls.

In order to make a preliminary study of overall flying-
boat configurations, tests were also made on models incor-
porating a typical engine nacelle and an engine nacelle
extended into a boom which is to function as the afterbody
and reduce the size of and possibly eliminate wing-tip floats;
the nacelle and nacelle ‘boom were also tested without the
hull models. For comparing the drag and stability, tests
were made on a streamline body simulating the fuselage of a
moderntransport airplane.