Towing Tests of Models as an Aid in the Design of Seaplanes Page: 4 of 26
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N.A.C.A. Technical. Memorandum No. 676
Hence, it .4as. necessary to develop a method of re-
search which would make" it possible to conduct the tests
in such a manner that they would be independent of the re-
quirements of a special airplane design. Such tests could
be made before the completion of the work of designing the
aircraft and would then be just as 'much an aid to the air-
plane designer in the design of the seaplane as would the
aerodynamic model tests, which no designer to-day would
forego.
The making and evaluation of a towing test of. a sea-
plane float system, which answers the requirements just
mentioned, is the subject of my present remarks. The ex-
perimental data presented have been taken from the tests
of the transoceanic airplane designed by Dr. Rumpler,
which were made by the.H.S.V.A. only a short while ago.
II. THE MAKING OF THE MODEL TESTS AND
THE PRESENTATION OF THE RESULTS
Because of practical difficulties in obtaining meas-
urements, we cannot simulate the accelerated take-off run.
Instead we select a number of definite speeds and tow the
model at each with constant speed. The model-must be
towed at each speed at several trim angles because the re-
sistance in general depends very much on the angle of trim.
Besides the speed and angle of trim, the lift which is de-
veloped by the water must also be prescribed. Then only
does the question of resistance have a single meaning.
As the load which must .be carried by the water is strongly
influenced by the wing cell and power plant, even for a
given definite flying weight, runs must be made at differ-
ent loads for each speed and trim.
In each case, besides the resistance., the trimming
moment necessary to produce the trim angle must be measured.
In the later computations these moment measurements form
the point of departure for the determination of the trim
position which the float system would assume under a given
aircraft.
Figure 1 shows in graphic form a part of the schedule
of te-st runs for the study of the Rumpler model. In this
manner the model is towed at all od angles of trim up to
110. For each of the parallel abscissas indicated, we ob-
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Schröder, P. Towing Tests of Models as an Aid in the Design of Seaplanes, report, July 1932; (https://digital.library.unt.edu/ark:/67531/metadc63586/m1/4/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.