An Investigation of Hydrofoils in the NACA Tank 1: Effect of Dihedral and Depth of Submersion Page: 7 of 36
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assemblies employing .struts of lo wer drag 'than the .bi.con-
vex st'rute. The procedure used in'determining tares makes
no allowance for interference effects - In most .practical
applications, however, the same type and the same.. order of
magnitude of interference will most likely be present.
The accuracy of the basic measurements is believed to
be within the following limits:
Speed, feet per second .. ... . . . . . . ., . .:. 40.2
Cavitation speed, percent. . . . . . . . . . . . *2
Depth of immersion (below free water surface),
inches . . . . . . . . . . . . . . . . . . , 0.2
Angle of attack, degrees .. , . .. . . * * * 0.1
Drag, pounds . . . . . . .l.O below cavitation speed
t5.0 with heavy cavitation
Lift, pounds . . . . . . .10.0 below cavitation speed
20.0 with heavy cavitation
As the amount, of cavitation increased, the accompany-
ing vibration caused the force measurements to be less
The experimental results of tests of hydrofoils with
the NACA 16-509 section are presented as curves of lift and
drag coefficients plotted against speed in figures 4 to 15.
Similar results obtained for the hydrofoils with the modi-
fied section are not given in their entirety but are dis-
cussed later in this report. Each figure shows the varia-
tions of the coefficients with change in speed for constant
values of the angle of attack and a constant depth below
the undisturbed water surface. The lowest speed at which
cavitation was observed on the upper surface of the hydro-
foil, for a given angle of attack, is indicated: on the
,.-." corresponding curve by a small arrow. With the test set-
up used, it was impracticable to determine the speed at
which cavitation occurred on the lower surface.
..... .. Curves have not boop faired through overy set of points
at constant angle-of attack w'itlb.the hydrofoil partly:. sub-
merged, because the grouping of points representing the
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Benson, James M. & Land, Norman S. An Investigation of Hydrofoils in the NACA Tank 1: Effect of Dihedral and Depth of Submersion, report, September 1942; (https://digital.library.unt.edu/ark:/67531/metadc61720/m1/7/: accessed May 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.