Force measurement runs were made on a model MK 13-2 Torpedo

to correct previously reported results for the discrepancies which were attributable to the interaction of pitching moment on the force measuring

apparatus. The plain body, the body with fins, and the body with a shroud ring tail were tested at yaw angles of -10 degrees to +10 degrees. Drag-force coefficients, cross-force coefficients, and yawing moment

coefficients were calculated and are presented in this report

Waid, R. L.

Caltech Authors - Main

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HYDRODYNAMIC COEFFICIENTS OF THE 
Report No. E-40 
August 28, 195 2 
MK 13-2 TORPEDO 
By R. L. Waid 
Hydrodynamics Labotatory 
California Institute of Technology 
Pasadena, California 
, , 
J. T. lv;. cGraw 
Project Supervi-sor 
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. Copy No. 19 
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HYDRODYNAMIC COEFFICIENTS OF THE 
MK 13-2 TORPEDO 
ABSTRACT 
GANFIRSNTB Ie 
Force measurement runs were made on a model MK 13-2 Torpedo 
to correct previously reported results for the discrepancies which were 
attributable to the interaction of pitching moment on the force me"!-suring 
apparatus. The plain body, the body with fins, and the body with a 
shroud ring tail were tested at yaw angles of -10 degrees to +1 0 degrees. 
Drag-force co\!fficients, cross-force coefficients, and yawing moment 
coefficients were calculated and are presented in this report. 
INTRODUCTION 
The results from experimental force measurements made in the 
High Speed Water Tunnel in the past have shown considerable variation 
when the model was supported at different points along its length. 
The Experimental Towing Tank of the Stevens Institute of Technology 
has recently compiled the results of force tests on the l\IJK 13-2. 1 
The Stevens report contains results from the David Taylor Model 
Basin, the Wind Tunnel of the Naval Torpedo Station at Newport, and 
the Experimental Towing Tank. Discrepancies arr.ong the various 
sources are very obvious as well as the discrepancies in the results 
presented by this laboratory. The interaction of pitching moment on 
the force measu-ring apparatus has been shown to be the cause of the 
discrepancies in our data. 2 An internal pitching moment balance has 
been fabricated to allow determination of the pitching moment so that 
the other forces can be properly corrected. The laboratory's 2-inch 
diameter models of the lVlK 13 have been tested by this technique to 
correct the previously published data. 
are given in this report· 
The results of these tests 
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Fig. 1 - Two-inch diameter models of the MK 13-2 Torpedo 
MODELS 
Three models of the MK 13-2 were tested, Fig. 1. 
follows: 
1. A plain body without fins, (upper). 
2. A body with fins only, (center). 
They were as 
3. A body with fins and a shroud ring, (lower). 
The models were 14. 37 inches long, and they were supported at 
42. 45% of the model length aft of the hose. The center of gravity used 
for the calculations (0. 44 L aft of the nose) was based on data published 
3 by the Bureau of Ordnance. 
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PROCEDURE 
The tnodels were tested at yaw angles from +10° to -10° at a 
velocity of 30 fps. Drag forces, cross forces, and yawing moments 
were obtained. Fitching moment readings were taken to obtain correc-
tions which were applied to the other forces. 
The model with the shroud ring tail was tested above, at 20, 30, 
and 40 fps to observe the effect of velocity upon the force coefficients. 
Drag forces were measured at zero degrees yaw for velocities 
from 10 to 70 fps. 
A duplicate run was made for each test incorporating a dummy 
image shield to provide the support interference corrections. 
RESULTS 
Figures 2, 3, and 4 show the effect of velocity on the force 
coefficient~ of the MK 13 with a shroud ring tail. The drag coefficient 
curves, Fig. 2, vary as expected at small angles of yaw. Beyond 8° 
yaw the curves seem to approach a common curve. The cross-force 
coefficients, Fig. 3, show a small increase over the velocities tested. 
The moment coefficient curves, Fig. 4, show no definite velocity 
trends. Based on a study of these graphs, the remainder of the tests 
were conducted at a velocity of 30 fps. 
Figures 5 through 7 show the curves of force coefficients for each 
individual model. 
pari son. 
Previously reported data is also included for com-
Drag coefficients at zero angle of yaw are presented in Fig. 8 
as a function of Reynolds number. The difference that occurs between 
the new and the old data can be entirely accounted for by the pitching 
moment. 
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Fig. 2 - The effect of yaw on dr a g coefficient at several velocities 
for the Mk 13- 2 torpedo with shroud-ring tail 
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Fig. 3 - The effect of yaw on the cross-force coefficient at several velocities 
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Fig. 4 - The effect of yaw on the moment coefficient at several velocities 
for the Mk 13-2 torpedo with shroud-ring tail 
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Fig. 5 - Hydrodynamic coefficients v s yaw for the Mk 13-2 bare hull 
Reynold s number {based on length ) 3. 6 x 10 6 
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F ig . 6 - Hydrodynamic coeffic ients vs yaw for the M k 13 -2 with plain fins 
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Fig. 7 - Hydrodynamic coefficients vs yaw for the Mk 13-2 torpedo 
with a shroud- ring tail 
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REYNOLDS NUMBER 
Fig. 8 - The effect of Reynolds number on the drag coefficient for all three 
configurations of the Mk 13-2 torpedo, yaw angle 0° 
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BIBLIOGRAPHY 
l. Jacobs, Winnifred R., "Correlation of Fluid Dynamic Experi-
mental Data for MK ·· 13 Torpedo", Experimental Towing Tank, 
Stevens Institute of Technology, Report No. 424, January 
1952. (Confidential) 
2. Kermeen, R. W., "Pitching Moment Balance for the High 
Speed 'Hater Tunnel", Hydrodynamics Laboratory, California 
Institute of Technology, Mem.orandum Report, No. EM -12. 4, 
April 15, 1952. (Confidential) 
3. "Torpedo, Mark 13 Type", Ordnance Pamphlet 950, November 
30, 1944. (Restricted) 
4. Knapp, R. T., "Water Tunnel Tests of the MK 13-1, MK 13-2, 
MK 13-2A Torpedoes'', Hydraulic Machinery Laboratory, 
California Institute of Technology, Report No. ND-15, 
November 9, 1943. (Restricted) 
6 U24£ lb£141lf? I 


Hydrodynamic Coefficients of the MK 13-2 Torpedo

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Hydrodynamic Coefficients of the MK 13-2 Torpedo

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