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National Advisory Committee for Aeronautics, Technical Notes - The Aerodynamic Drag of Flying Boat Hull Models as Measured in the NACA 20 Foot Wind Tunnel - I

Measurements of aerodynamic drag have been made in
the 20~foot wind tunnel on a representative group of 11
flying—boat hull models. The models were originally con-
structed for the N.A.C.A. tank and the results of tank
tests on 9 of them have already been published.

Four of the models were modified to investigate the
effect of variations in over-all height, contour of deck,
depth of step, angle of afterbody heel, and the addition
of spray strips and Windshields.

The results of these tests, which cover a pitch—angle
range from ~50 to 10°, are presented in a form suitable
for use in performance calculations and for design pur—
poses.

The scarcity of aerodynamic drag data on flying—boat
hulls has been brought to the attention of the N.A.C.A.
through repeated requests for such data. At the present
time practically all of the data on the aerodynamic char-
acteristics of flying~boat hull models that have been pub—
lished are to be found in reference 1. The tests report~
ed therein were made on models of which the greatest num~
ber are at present obsolete and of which the dimensions
were less than one half those of the models in the pres~
ent tests.

The present tests were greatly facilitated by using
the models that had been constructed for hydrodynamic re»
search in the N.A.O.A. tank. These models formed a repw
resentative group of recent hull lines and were of such
size as to permit a Reynolds Number (based on hull length)
of about 7,500,000 to be obtained.

The main purpose of this investigation is to make
available to the designer useful information with regard
to the aerodynamic drag of various types of flying~boat
hull models. The present report is the first in a series
covering an investigation in this field. Through close
cooperation between the hydrodynamics and aerodynamics
divisions it is hoped'that results leading to improvements
in hull design may be obtained.