7 AD-A103 950 DAIO TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CE--ETC F/6 13/10
HYDRODYNAMIC PRESSURE MEASUREMENT ON THE SONAR DOME OF A CSN-38--ETC(U)MAR 81 L E MOTTER
UNCLASSIFIED DTNSRDC/SPU-0991-0 NL
III
L m 0
-4
DAVID W. TAYLOR NAVAL SHIPSRESEARCH AND DEVELOPMENT CENTER
Bethelda, Maryland 20084
HYDRODYNAMIC PRESSURE MEASUREMENT ON THE
SONAR DOME OF A CGN-38 CLASS MODEL
Co
rn Lewis E. Motter
z
0
Cz APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED
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z0
SHIP PERFORMANCE DEPARTMENT O T IC17;' r -" " 1 '"
D
0 March 1981 DTNSRDC/SPD-0991-01
U!
NDW OTNOSRDC 56021304 Q80)(spU~d39016)81 9 09 1 2,8
MAJOR DTNSRDC ORGANIZATIONAL COMPONENTS
S DTNSRDC
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-- ' HYDRODYNAMIC PRESSURE MEASUREMENT ON THE . FinalSONAR DOME OF A CGN-38 CLASS MODEL 0--ptRti. ORO. REPORT NUMBER
7. AUTHOR(&) 9. CONTRACT OR GRANT NUMBER(d)
Lewis E./Motter
9. PERFORMING ORGANIZATION NAME AND ADDRESS 10 PROGRAM ELEMENT. PROJECT, TASKShip Performance Department AREA & WORK UNIT NJMBERS
David W. Taylor Naval Ship R&D Center Work Unit 1730-105Bethesda, Maryland 20084
I I CONTROLLING OFFICE NAME AND ADDRESS 12 REPORT DATE
Marah 1981Naval Sea Systems Command I&.-.M "dRM0IMAGESWashington, D.C. 20362 26
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SQS-26 Sonar DomeCCN-38Hydrodynamic Pressure Measurement
1,1 Seakeeping
20 ATRACT (Continue on reveree side if nceemary aid Identify by block number)
The hydrodynamic pressure distribution has been measured on the SQS-26sonar dome of a CGN-38 Class ship model. Experiments were conducted primarilyin head regular wave conditions; however, some data was collected in irregularhead waves and in regular and irregular waves at 45 degrees off the port bow.Regular wave responses are presented in the form of response amplitude opera-tors and the irregular wave results are presented as significant values ofresponse. -
DD , O 73 \ OITION OF I NOV 6 iO OBSOLETES 'N 0102.LF-014.6601 UNCLASSIFIEDI SECURITY CLASSIFICATION OF THIS PAGE (US~lan Date Entered
SECURITY CLASSIFICATION OF THIS PAGE (When Date Entered)
S rUP ITY CLASSIFICA I".N rif HI D G t'. ?, Pll . +,++
o
TABLE OF CONTENTS
Page
LIST OF FIGURES ............... ............................... iii
LIST OF TABLES ............. ............................... ... iv
ABSTRACT ................. .................................. 1
ADMINISTRATIVE INFORMATION ......... ......................... . ..
INTRODUCTION ............. ................................ . .. I
DESCRIPTION OF PROTOTYPE AND MODEL .......... ..................... 1
RESULTS ................. ................................... 2
OSCILLATORY RESPONSE IN REGULAR WAVES ......... .................. 2
OSCILLATORY RESPONSE IN IRREGULAR WAVES ........ ................. 3
CONCLUSIONS ................ ................................. 4
LIST OF FIGURES
1 - Body Plan of CGN-38 Class ........... ....................... 5
2 - Location of Pressure Gages on Sonar Dome ........ ................ 6
3 - Pitch Angle and Dome Pressure as a Function of Wave Height ... ....... 7
4 - Pitch Transfer Function for 10, 20 and 30 Knots in Head Waves .. ..... 8
0!5 - Heave Transfer Function for 10, 20 and 30 Knots in Head Waves ...... 9
6 - Relative Bow Motion Transfer Function for 10, 20 and 30Knots in Head Waves ............. .......................... 10
7 - Sonar Dome Pressure Transfer Functions for 10 Knots inHead Waves ............. ............................... ... 11
8 - Sonar Dome Pressure Transfer Functions for 20 Knots in
Head Waves ............... ............................... 12
9 - Sonar Dome Pressure Transfer Functions for 30 Knots in
Head Waves ............... ............................... 13
10 - Pitch Transfer Function for 10 and 20 Knots in Bow Waves .......... ... 14
11 - Heave Transfer Function for 10 and 20 Knots in Bow Waves .......... ... 15
12 - Yaw Transfer Function for 10 and 20 Knots in Bow Waves .. ......... ... 16
iii
Page
13 - Relative Bow Motion Transfer Function for 10 and 20 Knots
in Bow Waves ............ ... .............................. 17
14 - Roll Transfer Function for 10 and 20 Knots in Bow Waves . ........ ... 18
15 - Sonar Dome Pressure Transfer Functions for 10 Knots in
Bow Waves ............... ............................... 19
16 - Sonar Dome Pressure Transfer Functions for 20 Knots in
Bow Waves ........... ............................. ..... 20
LIST OF TABLES
1 - CGN-38 Class Ship Particulars ........ ...................... ... 21
2 - Significant Amplitude Responses from Irregular Wave
Experiments ............ ............................. .... 22
EJJSA-ccession For
Una : ou ced
Avili biIity Codes j
, Avai anid/or ''t
-Dist Special
iv
ABSTRACT
The hydrodynamic pressure distribution has been measuredon the SQS-26 sonar dome of a CGN-38 Class ship model. Ex-periments were conducted primarily in head regular wave con-ditions; however, some data was collected in irregular headwaves and in regular and irregular waves at 45 degrees offthe port bow. Regular wave responses are presented in theform of response amplitude operators and the irregular waveresults are presented as significant values of response.
ADMINISTRATIVE INFORMATION
This work was funded by the Naval Sea Systems Command under Work Request 02940,
dated 11 November 1980. The work is identified at the David W. Taylor Naval Ship
Research and Development Center under Work Unit Number 1730-105.
INTRODUCTION
The hydrodynamic pressure acting on a ship is the result of several components
including effects from the incident waves, the diffracted waves, and the ship motion
in six degrees of freedom. As part of an effort to better understand these effects
and to improve hydrodynamic pressure prediction capabilities, model experiments were
conducted with a model of the nuclear powered cruiser (CGN-38). The steady and the
oscillatory hydrodynamic pressure on the sonar dome was measured and is presented in
this report for future use in verifying computer predictions.
DESCRIPTION OF PROTOTYPE AND MODEL
The experiments were conducted using a 23.27 ft (7.09 m) wood model, number
5201, to represent the CGN-38. Particulars of the ship and model are listed in
Table 1. The body plan is shown in Figure 1. The model was fully appended with
bilge keels, twin propellers and rudders.
The model was instrumented to measure pitch, heave, roll, yaw, sway, and the
vertical motion of the bow relative to the water surface. The relative bow motion
(RBM) was measured near the nose of the dome at Station 0.5. In addition, the
SQS-26 dome was instrumented with six pressure gages at the locations indicated on
Figure 2. As shown in Figure 2, four gages were located on the intersection of the
dome and the waterline 4 feet below the baseline. The center of the sonar transducer,
located on the ship centerline at Station 0.85, was used as a reference to locate
the gages. The gages are identified in this report as P1 through P6, as indicated
on Figure 2.
1
RESULTS
All results presented are for the full-scale 560.0 ft (170.7 m) CGN-38 Class
ship. During the experiment the model was self-propelled and automatically steered
by using a rudder control system with feedback from the yaw and sway motions. It
was free to move in all six degrees of freedom. Video tape records provide profile
views of the bow and sonar dome during each run.
Regular wave experiments were conducted at 10, 20, and 30 knots in head waves
and at 10 and 20 knots in waves 45 degrees off the port bow (referred to as 225-
degree waves and bow waves). Irregular wave experiments were conducted in long-
crested head waves at 10 and 20 knots in Sea States 5 and low 7 (nominal signifi-
cant wave heights of 10.0 ft (3.0 m) and 23.0 ft (7.0 m)), respectively, and at
30 knots in Sea State 5. Also, irregular wave experiments were conducted in bow
waves at 20 knots in Sea State 7.
At no time during any of the experiment did the sonar dome leave the water. On
a few occasions, pressure gage P3 appeared to be at or slightly above the plane of
the surrounding water surface. However, the flow around the dome was such that thL
gage was in contact with the water at all times. No indications of impact loading
was observed on any of the pressure gages. Therefore, all measured pressure was
sinusoidal and suitable for harmonic analysis.
OSCILLATORY RESPONSE IN REGULAR WAVES
As evidence of the applicability of superposition to this data, the data
linearity with respect to wave height was examined for a 20-knot speed in waves
with length equal to the ship length. The pitch and pressure measured on gage P4
are shown in Figure 3 as examples of the linear relationship observed between wave
height and each motion and pressure measurement.
The transfer functions for pitch, heave and motion of the bow relative to the
water surface (RBM) for head waves is shown in Figures 4, 5, and 6, respectively.
The pressure at all six dome locations is shown in nondimensional form in Figures
7, 8, and 9 for 10, 20, and 30 knots, respectively. The pressure measurements are
arranged on each page for ease of comparison. The results from pressure gages P1,
P4 and P5 (located along the stem at the 0, -4 ft (-1.22 m) and -8 ft (-2.44 m)
waterlines, respectively) are lined up down the left side of the page. Note that a
similar pressure magnitude is measured at each of the three stem locations for the
2
20- and 30-knot speeds. At the 10-knot speed the most severe pressure was at the
P4 location.
The results from pressure gages P2 and P6, located at a 45-degree angle from
the centerline to port and to starboard, respectively, are lined up on the top
right side of the page. As expected, assuming symmetrical flow around the dome in
head waves, a similar pressure magnitude was measured at each of the locations.
The results from pressure gage P1, located at 67 degrees off the centerline to
port, is shown in the lower right corner. Potential flow theory has indicated that
this location is near the point of minimum static pressure on the dome. As shown
in the figures, the oscillatory pressure at the P1 location is only slightly less
than that measured at the other gage locations.
The pressures measured at each location are nearly the same for both the 20-
and 30-knot speeds. As expected, this agrees with a similar trend between relative
bow motion at 20 and 30 knots shown in Figure 6.
Figures 10, 11, 12, 13, and 14 show the pitch, heave, yaw, relative bow motion,
and roll, respectively, for regular waves at 45 degrees off the port bow. The yaw
motion is highly sensitive to steering. From Figure 12 it can be seen that, with
only a few exceptions at 10 knots, the yaw was very consistent.
The pressure at all six dome locations from the experiments in bow waves is
shown in Figures 15 and 16 for 10- and 20-knot speeds, respectively.
As was the case for head seas, the pressure measured at location P4 was similar
to the pressures at P3 and P5 at 20 knots but slightly higher at the 10-knot speed.
As was anticipated, the pressure at the P2 location, facing the incoming waves, was
greater than at the P6 location, on the opposite side of the dome, for both the
10- and 20-knot speeds.
OSCILLATORY RESPONSE IN IRREGULAR WAVES
The significant values of the ship motions and dome pressures measured during
the irregular wave experiments are shown in Table 2 for all sea states, speeds, and
headings considered. The values for the heave at 30 knots in Sea State 5 head
waves, the sway at 10 knots in Sea State 7 head waves, and the sway at 20 knots in
Sea State 7 bow waves were omitted from the table. Errors occurred in the measure-
ments as a result of an occasional improper position of the model. The model
position did not affect other measurements.
3
Trends observed between the pressures in the regular wave experiments agree
with those observed in the irregular wave experiments. The pressure magnitudes
measured at locations P3, P4 and P5 are nearly equal (within the accuracy of the
experiment) to each other for a given speed. Also the pressure magnitude at any
given location is nearly equal for both the 20- and 30-knot speed. As was observed
in regular waves, the pressures at the P2 and P6 locations are nearly equal for a
given speed in head waves. However, the pressure is slightly less at the
P6 location than at the P2 location in bow waves. Finally, the magnitude of the
pressure at all locations appears to be directly related to the relative bow motion.
As the relative bow motion changes so does the dome pressure.
CONCLUSIONS
Model experiments in regular and irregular waves and in calm water have been
conducted with the CGN-38 Class. The motion of the model and the pressure at six
locations on the dome were measured and analyzed. Transfer functions from the
regular wave experiments and significant values from the irregular wave experiments
were presented. From the results the following observations have been made:
1. At no time during the experiment did the sonar dome leave the water or slam.
2. For the 20- and 30-knot speeds, the pressure at the three stem mounted
gages was nearly the same in both head and bow wave conditions.
3. The oscillatory pressure appears to be proportional to the relative bow
motion.
4
400* W)4Q*
280 2
20 5' D* L
120' 'A0 ,
40" L .. . .S
,4" 'A.
2 2 4 4 '- T - - BA T -
2E' ED'~-
-. - ..9 402*.s -A6-*
BUTT
120 W L
Figure I Body Plan of CGN:-38 Class
5i- .--.-... ..- _ --
STATION 1
W. L.
P 3B. L.
P2 P1
-4 FT 4
-8 FTP5 __-
CENTERLINE PROFILE VIEW
STATION 1
P 6 - - ----- --- ----- -- -----
P4
44
SONARTRANSDUCER
6 7V
P1
SONAR DOME CROSS SECTION AT-4 FT WATERLINE
Figure 2 - Location of Pressure Cages on Sonar Dome
6
20 KNOTS IN HEAD WAVES
NIL 1.0
3 -.01
LU
clo
.1_z 101
I-I
t 0
P4
P4-
U, - --
2 0
Zw
i)
x 1 - 1000.
o II II
0 5 10 15 20 25
WAVE STEEPNESS, (WAA) x 10- 3
Figure 3 - Pitch Angle and Dome Pressure as a Function of Wave Height
7
10 KNOTS IN HEAD WAVES 20 KNOTS IN HEAD WAVES
1.0- 00 0 0O
0 0 0
0.8- 0 0
0
40.6 -0
0.4
o.O°10 O
0 O
.0
0 0.5 1 1.5 2 25X/L 1.2 1 0I
30 KNOTS IN HEAD WAVES 0 0 0
1.0 0
0.8
0
>!0.600
.4
0.4
000.2
0
001 0 00 0.5 1 1.5 2 25
X/L
Figure 4 - Pitch Transfer Function for 10, 20 and 30 Knots in Head Waves
- |l . . . ._. - • .. .
20HEAVE HEAVE10 KNOTS IN HEAD WAVES 20 KNOTS IN HEAD WAVES
1.6
I.-..J0.
Lu 1.2
0.8- 0 zo : 0 )
CL 00
000I I t _ _00_ 0 _ __I
0 0.5 1.0 1.5 2.0 2.5A/I .zo1
HEAVE30 KNOTS IN HEAD WAVES
w 1.6
> 00.0
.0.8-
75
4
0.4- 0
0
0 ._ __ 00O I . .0 0 5 1.0 15 20
Figure 5 Heave Transfer Function for 10, 20 and 30 Knots in H~ead ave.,- -- ... .. . . . .. ' " ' " " . .. . ' " ' .. .. . ' .. . . . . . .. . ... .. . . i - - ... , .. .. . ... -- . . . = . . .
r4.0
10 KNOTS IN HEAD WAVES 20 KNOTS IN HEAD WAVES
C3.2 - 0
-J 0a.o
w0 0>2.4 -
rt 00 0
o 0 0CD 0o0 0 0
0~ 0.
000 0.5 1.0 1.5 2.0 2.5A/L 4,0 1I
30 KNOTS IN HEAD WAVES
3.2
0'U
2.4
2 00 00 0
1.6
0
- 0 00.8
'U
I I I I0 0.5 1.0 1.5 2.0 25
'/L
Figure 6 - Relative Bow Motion Transfer Function for 10,20 and 30 Knots in Head Waves
10 -__ _ __
10 KNOTS IN HEAD WAVES
2.0
P3 P2
1.6-
1.2
0.8 000
0.4 - 0
00
0
2.0
' P4 0 P6
16
"00
000
IF 0 0
0 00 0 0
0.4 0
0 00g 00 I I I 1 I 1
2.0 I
P5 P1
1.6
1.2 -&
0. -0 0o ~ o 0
12o
0.4- 0 8 0 00
0~
0 0 o 0 O
0.4 0
000 10I I1 .20 I2.5
0 0.5 1.0 1.5 2.0 2.5 0 0.5 1.0 1.5 2.0 2.5X/L ALt
Figure 7 - Sonar Dome Pressure Transfer Functions for
10 Knots in Head Waves
11
20 KNOTS IN HEAD WAVES2.0iI
P3 o P2
1.6- 0
01.2 -- 0
0 00 0 a
0.S 0 0 0
0 000.4 00J
00
00
0 I I I I i
2.00
o P4 PB
1.6 -
0
1 .2 0 -0 0
0 0 00 0
.0000 00
aOz 0
0.4 0 00
0 0
2.0000
01.6 -0
0 0.2- 0
0
000.6 - %
0 00 0 0
I I I I I I I0.s 1.0 1.5 2.0 2.5 0 0.5 1.0 1.5 2.0 2.5
A/L A/L
Figure 8 - Sonar Dome Pressure Transfer Functions for20 Knots in Head Waves
12
.. . . .,. . . . . . . . . . . . ..4, . .. .
30 KNOTS IN HEAD WAVESZ.4 1 I I II
3 o P2
to - 0
2.0 00
1.6
0 0 00
1.2- 0 0
0 0 ( 000.8 -00
0 0
0.4- 0 0
1 0 00(II I I I I
2.0 I0 I I I I+ P4 PIS0
- 1.6 0
1 0000- O0 0
S1.2 - 00 o0
0.8 0 _ -00 0
00 0 0
0 I I I I L I I I I
z0 10 1 I I
2.0- 0 0
0
000
00
0 0 0
00
0s 0 0 0
00.40
000A - 0 0
OI 1 0 1 O PU ' I I I
0 0.5 1.0 1.5 2.0 2. 0 0.5 1.0 1.5 2.0 2.5
AlL X/L
Figure 9 - Sonar Dome Pressure Transfer Functions for
30 Knots in Head Waves
13
10 I
PITCH
10 KNOTS IN 225 deg WAVES
08
0 0q 0.6 0- ,, 0
0
00.4 0
CL 0
0,2 - 00
0 I I 10 05 10 1 5 2.0 2 5
f/L
10 -- - T -PITCH
20 KNOTS IN 225 dq WAVES
08 0
0 000 00
CL 06 - 00-A
04 0
4 0
002
0
0 05 1 0 1 5 20 2.5
,/LI
Figure 10 - Pitch Transfer Function for 10 and 20 Knots in Bow Waves
14
2.OHEAVE
10 KNOTS IN 225 dog WAVES
1.6 1
w 1.24
w
4w
0.8 00
00 0 0
0.4 0 0
0 00
01I I I
0 0.5 1.0 1.5 2.0 2.5/L
2.0
HEAVE20 KNOTS IN 225 deg WAVES
1.64
w 1.2-
x 0.8 - 000 000 0 0
0
00.4-
0
o 0000000
00
0 0.5 1.0 1.5 2.0 2.5
X/L
Figure 11 - Heave Transfer Function for 10 and 20 (nots in Bow Waves
15
0.5YAW 00
10 KNOTS IN 225 dog WAVES
0.4
b 0.3,.
la 00
p0.2 0000
0.1
CP0 0
0 0, 1 I0 0.5 1.0 1.5 2.0 2.5
V/L
0.5 1
YAW20 KNOTS IN 225 dog WAVES
0.4
t 0.3 -.,J(A~1
LU 00
0.2 -00
0.10
0
0 00 0 I I I,
0 0.5 1.0 1.5 2.0 2.5
Figure 12 - Yaw Transfer Function for 10 and 20 Knots in Bow Waves
16
4.0 ROM
10 KNOTS IN 225 dog WAVES
00
S3.2I.-o
-J
2.4
0
1.6 0
004 0
• 1 0.8LU
00 0.5 1.0 1.5 2.0 2.5
V]L
4.0I !
RBM20 KNOTS IN 225 deg WAVES
LU 03.2 0
a. 00
IL> .4Uj 0 0Z4
0$- 00
1.6o 0
F- 0
. 0
0I I ,I I0 0.5 1.0 1.6 2.0 2.5
VsL
Figure 13 - Relative Bow Motion Transfer Function for10 and 20 Knots in Bow Waves
17
II III I i I .. IIi ii. ..
4,0
ROLL10 KNOTS IN 225 dog WAVES
3.2
2.4
LU 00
0-J .6- 0
00
00
0
0 0000.5 1.0 1.5 20 2.5
2.011
L
ROLL20 KNOTS IN 226 deg WAVES
1.60
0
9L0 1.2(A 0
4 0 0. . . . .LUL
0
0
0.4
00 0
00 0.5 1.0 1.5 2.0 2.5
VR
Figure 14 Roll Transfer Function for 10 and 20 Knots in Bow Waves
18
10 KNOTS IN 225 deg WAVES2.0 C
P3 P2
1.6 -
0 0
01.2 00 0
0 0
0.80
0 0 0000
0.2 - 0 0
0 0
2.0 0S P4 o"P6
o0
- 1.8 0
-14
-0
0 0
00.4
000.8- 0
0z 00
0o
0o I I 1
P5 P1
1.6 -- -
00
1.2 00 0 0
0 0
0.8
0 0 00
0.4 0 0 0
0 1 1 1 1 1 1I0 0.5 1.0 1.5 2.0 2.5 0 0.5 1.0 1.5 2.0 25
XIL Alt
Figure 15 - Sonar Dome Pressure Transfer Functions for
10 Knots in Bow Waves
19
20 KNOTS IN 225 do9 WAVES2.0 T I11 I
P3 P2
000
1.2 0 0 00
0 0 00.8 0- 0 0
0 0 00
0 0
P6o P4 000
1.2 0 000
000
0 0 00.- 0 0
a000
0.4 - 0
Q C0 0i
0 I I I I I I I 2.0 F - -
P5 0 P1
001.6
0
1.2 -0 000000
0.6 - 000 0
0 o °00.4 0 0
C 0
o" I -- I I -L- - I I 1 .0 0.5 1.0 1,5 2.0 2.5 0 0.5 1.0 1.5 2.0 25
XIL. A'
Figure 16 - Sonar Dome Pressure Transfer Functions for20 Knots in Bow Waves
20
TABLE 1 - CGN-38 CLASS SHIP PARTICULARS
Parameter Value
Ship Model 5201
Displacement 12,031 long tons, S.W. 1885.6 lbs F.W.(12,224 tonnes) (855.3 kg)
Length Between Perpendiculars 560.0 ft 23.27 ft
(170.7 m) (7.09 m)
Draft 22.7 ft 0.94 ft(6.9 m) (0.29 m)
Beam at Midship 61.90 ft 2.57 ft(19.07 m) (0.79 m)
Longitudinal Center of Gravity, 8.16 ft 0.34 ft
LCG, aft of Midship (2.49 m) (0.10 m)
Vertical Center of Gravity, KG 2.32 ft 0.10 ft(Relative to Waterline) (0.71 m) (0.03 m)
Transverse Metacentric Height, GM 4.84 ft 0.20 ft
(1.48 m) (0.06 m)
Scale Ratio 24.064
21
H- L) c OD -4 -4
o ~ ~ ~ c C14A A~ 0 -) A* It A Ln CN H4
>~ 0 -r =- -2 -Ln
o0 r -4 n 0 -4 0T C 0
0Q 01 (N-4A U-
4) U) ON 00 1 Ln C
0 0 'H (N ' * -4.0 ' LA)
V), %-- ON. r, r 0N H0 co C 4 % 'D LA% Ln
H 0 0 (N
to~ C) C
> -Li a -4 Do -q H en
C) 0Q-4 - -T o r 0 -*
04 C14 H A .4 .. - O 4
a) (h H- H) -It - 0 I C 0
mi 0 y C4,n 0 C. 50) -4 -Z
to0 Ci) H 0 *A %a It *) %D %
>~u ul** CO 0 C -4 U- C
0 0 (.'4 (N m.' CSJ m- - - 4 (
tAU- LA -.T r L o a 00 Hl -4 .C CA co c-
c0 0l H4 01 OD r0H - 4 A ' -4
0' C4 Ci) U-i CO4 CO 04
m~ 04 -- CN .r- , m. S... Ul 1- m
0 0 0 0 0) (N4 LA 0'. c-i Ui .4 -4 U
0 N
bec- (n (n m- (YN m- -. ~ C A H
Aii LA o- -
H) H4 H 4 -
wU) (a t
cc ~~4) .4 min %
a. >4. .- P- 0
22 ' Ui Ui -
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3. TECHNICAL MEMUHANDA, AN INFORMAL SERIES, CONTAIN TECHNICAL DOCUMENTATIONOF LIMITED USE AND INTEREST. THEY ARE PRIMARILY WORKING PAPERS INTENDED FOR INTERNAL USE. THEY CARRY AN IDENTIFYING NUMBER WHICH INDICATES THEIR TYPE AND THENUMERICAL CODE OF THE ORIGINATING DEPARTMENT. ANY DISTRIBUTION OUTSIDE DTNSRDCMUST BE APPROVED BY THE HEAD OF THE ORIGINATING DEPARTMENT ON A CASE-BY-CASEBASIS.