The development and evaluation of the TMB knotmeter type 205A

THE DEVELOPIflENT AND EVALUATION OF THE TMB KNOTAETER TYPE 205A

by

Leo F0 Fehiner

and Thomas Gibbons

RESEARCH AND DEVELOPZENT REPORT

January 1956

: Report 1026 I Lab

v.

Scheepsbouwkunde

Technische Hogeschool

Delfi

NAVY DEPARTMENT

THE DAVID W. TAYLOR MODEL BASIN

TI

PEVLQP!1

AI1D EVALUATION OP TI

iQTMETERTYPE2O5A

by

Leo F. Fehiner

and

Thomas Gibbons

ii

TABLE OF CONTENTS

LIST OF ILLUSTRATIONS _iii

Kfiotmeter Installation, Matntenance and Adjustments

REPERENCES 12 INITIAL DISTRIBUTION. . ABSTRACT INTRODUCTION DETAILS OF DESIGN 3' 1 2 .Body ₂ Wing ₂ Tall Surfaces k Tow Point 6 Impeller . . . 6 INSTRUMENTATION 6 Transducer . 6 Speed Indicator . 7 EVALUATION TESTS . Basin Tests ₇ Sea Trials 7' ACKNOWLEDGMENTS . . 7 APPENDIX ₈

iii

LIST OF ILJUSThATIONS

Figure 1 Towed Body for the T Knotmeter

Type

205A. 15

Figure 2 Schematic Diagram of the Body for the T .. 16

Knotmeter Type 205A.

Figure

3 Cable Tension at the Body as aFiinction of 17

Towing. Speed. .

Figure k Depth Of T Knotmeter as a Function of Spied 18

and Scope of Cable. :

Figure 5 Assembly Drawing of Towed Body0 19

Figure 6 TMB Knotmeter Type 205A Instrumentation Cabinets 20

Figure 7 Block Diagram TMB Knotmeter Type 205A. 21

Figure 8 Circuit DiaErarn TNB Knotrneter Tje 05A. 22

THE DEVELOPMENT AND EVALUATION OF THE TMB KNOTMETER TYPE 205A

by

Leo F. Fehlner and ThomaB Gibbons

ABSTRACT

The design and evaluation of an instrument to measure the speed of a ship relative to the undisturbed water is

pre-sented. This device consists of a towed body and associated

instrumentation and is known as TMB Knotmeter Type 205A. The

knotmeter towed satisfactorily in the "high-speed" basin at

speeds up to 30 knots. Although 15 knots was the top speed

attained at sea due to limitations on other towing gear, it is not anticipated that difficulty would be encountered in

reaching higher speeds. The body was launched and retrieved

from the side and stern of the towing vessel with no difficulty.

INTRODUCTION

As a result of previous sea trials aboard naval surface ships, it became evident that the previous methods of measuring

and Indicating ship speed were inadequate. A specially

de-'signed towed body and its associate electronic equipment, known as the TMB Knotmeter Type 205A, was therefore developed and

constructed. This knotmeter was designed to be towed from a ship

at speeds up to 30 knots and at depths of approximately 100

feet so that it would tow out of the pressure field of the

tow-ing shi,p. The knotmeter indicates the speed of the ship, in

knots, relative to the undisturbed water. Also, it was

de-signed small enough for two men to launch arid retrieve at. speeds of 3 to 6 knots.

2

This report presents an account of the design procedure and the results of evaluation tests of the TNB Knotineter Type

205A. Additional data are provided for installation,

main-tenance and adjustments of the knotmeterand associated

equip-ment.

DAILS OF DESIGN

BODY

To provide an adequate streamline housingfor the pulse

generator and magnetic pickup, a body of. revolution with a fineness

ratio of 5 was selected. A photograph of the body is shown

in Figure 1. The body is composed of several sections,

consist-ing.of a 2-tL. ellipsoidal nose, a cylindrical center body and a conical tail section. The housing and its components were made of brass to prevent sea-water corrosion.

WING

From the results of cable calculations based upon the

tables given in Reference 1, it was determined that the

knot-meter body would have to produce a total downward force of 900

pounds at 30 knots. The weight of the body and its internal

parts were expected to be approximately 100 pounds in water,

leaving 800 pounds to be supplied by a depressing wing.

The lift force developed by a wing can be expressed as

2,3

'L= PU?SWCL (1

(b/2)2) (1]

where

p is the fluid mass density,

U is the towing velocity, .

S is the projodted area of the wing,

CL Is the lift coefficient,

23

_{References are listed on page}

3

is the span of the wing as shown in Figure 2,

R is the effective radius of the body (equal to

'D/2), and

.Ii

K2

1 isa factor which approximately

ac-L (b/2)2 J counts for the wing-body interterece,

By substituting in. Equation [1] for the wing span In terms

or the wing-aspect ratio, it follows that the wing area Is

L

pU2C a.

where

a is the wing aspect ratio,

b2

If the values,. CL = 0.11., U = 50.7 feet/second (30 knots), R = 0.25 feet,

a =k,

L =800 pounds, and 2 slugs/cubic foot

are substituted in Equation [2] the area of the wing, &,, is

o.8M. square feet.'

k

The lift coefficient of a wing of finite aspect ratio

can be expressed according to lifting-line theor72 as

a

_2fllsina

L

_a+x

where

a

is the angle of attack of the wing,

K

is correction factor to the section l2ft

curve slope of 2fl .whioh. accounts for the

section thickness (K = 0.9').

Assuming a lift coefficient of 0.11, an aspect. ratio of 11, and

that for small angles. sin' a is equa.l to a In radtans, EqVtion

[3] gives the required wing angle

t attack

5.8

5.8 degreea.

TAIL URFACES

Using the approximate method described in Reference 2,

the hydrodynamic moment produced by the, tail surta.ce

can be

written, as

MT = SlpU

_a

211K sin a

[k]

The Mtlnk or ide1 xflometit4prodtced ....the'.body is

MB = '

(K

-

K1) *pU2 Sin2a

[5]

where

18

the volume of body.

Equating Equations (k]. and

(5]

for equilibrium and assuming

for small angles sina is equal to a in radians,the total tail area, 5T for the case where the tail surfaces are 25 degrees with respect to the body axis is

is the moment produced by tail surfaces,

MB is the moment produced by the body,

ST is the total area of tail surtaces,

2T is the distance from center of pressure of tail surface to center-of-pressure of body

and tail surfaces combined,

aT

(K2 - K1)

is the aspect ratiO of tail surfaces based on total area and equal to _b!,

isthe virtual..masa:..tactor, and

(K2

-l.k2rli

aK

(6]

where l.k is a fáctbr to allow fo the.k5...degree

orientation of the tail surfaces For an e]Upàoid of

fineneRs ratio

_5,

the vIrtual- mass factor (K2 - K1)equals

0.836. 5

Assuming

=

0.75

feet

= 0.296 cubic feet

aT = 1L0 .

then from Equation [6.] the required tail area, 3T' is 0.12. square feet.

No correction was made to the lift to account for the

sweep backof the tail surfaces. The tail surfaces were swept back to protect the impeller when the body

i8

on the deck and

to allow sea weed to slide off the surfaces. There was no

correction made to the Munk or ideal moment to account for viscous effects as shown in Reference

7.

TOW POINT

To facilitate handling of the body in air and to orient

the housing advantageously for its entry into the water, the body should hang horizontally from its tow cable in the air.

The center of buoyancy was selected as the towpoint and the body ballasted so that its center of gravity was located below

the towpoint and on a vertical line containing the towpoint

and quarter chord of the wing. Experience obtained in towing

previous towed housings indicates that it is necessax9 to

provide a rigid towstaff to avoid chafing of the cable cr cable

fairing at the intersection of cable and body2. The towstaff

was extended out of the body approximately 6 inches when ver-tical, as shown in

Figur9111..

For spee4s up to 30 knots the towstaff was given freedom to pivot forward about 15 degrees.

IMPELLER

A three-bladed impeller was designed, which rotates at

approximately

66I

revolutions per minute per knot. This im-peller drives the transducer which is used to generate pulses. The blades of the impeller, as shown in Figure 2, are swept back ₁₅ degrees to prevent sea weed from gathering on them.

INSTRUMENTATION

6

TRANSDUCER

The transducer consists

spaced iron slugs around it. disk past an. electromagnetic

and carried up the tow cable

of a brass disk, with 90 equally-The impeller wheel drives the

pickup and pulses are generated

SPEED INDICATOR

From the electromagnetic pickup, the speed indicating

8ystem counts and di'splays the pulses on a Berkley Counter. These pulses are prodticed at a rate of 200 per, second per

knot, _{Therefore, counting for 1/2 second, a speed of 10}

knots produces 1000 pulses on the Berkley Counters and with. proper placement of the decimal, the resulting reading 18 10'

knots. _{This calibration is the same over the speed range}

since the impeller RPM varies linearly with speed.

EVALUATION TESTS BASIN TESTS

The knotmeter towed satisfactorily:at.speedsup to 30

knots in the "high-speed" basin. The instrumentation was

calibrated with the high-speed towing carriage.. 'The

variation of the àabie tension at the.bddy with' spëéd. ..s

presented in Figure

_3.

SEA TRIALS

The TMB knotmeter was used sucessful].y on sea trials.

Over a period of approximately four months at sea, minor troubles were discovered and corrected such as, excessive

cable vibration at the towstaff, bearing failure and'

cor-rosion of tow cable. A variation in the indicated readings

due to pitching and rolling of the ship was noted. ' This may

be minimized by increasing the uunting period' and indicating

the average speed over a' longer time interval, Although,

15 knots was the top speed attained at sea 'due 'to limitations

on other towing gear, it is not anticipated that difficulty would be encountered In reaching higher speeds. The body was launched an4 retrieved from the side aüd stern of the' towing vessel with no difficulty.

.ACIQ0WLEDGMTS

The design and development of the'electronic instrumenta-tion was carried out by Mr. J, F. Hunt with the assistance of

Mr. G. N. Metsel, '

8

APPDIX

Knotmeter Installaticn, Maintenance and Adjustment From the results of previous sea trials, it appears that the location of the knotmeter launching site on the deck of the

ship need not be restricted. It is recommended, however, that

the location of the launching site be such that the ship

motion is a minimum. The ithotmeter cable used in all sea

trials was a l-H-0, 0.185-inch diameter stainless steel

cable, number 18 AWG conductor, Kel-F insulation, manufactured

by American Steel and Wire Company.

Figure k, presents the variation of the towing depth of. the knotmeter as a function of speed and scope of tow cable.

Greater.towing depths may be obtained by installing a cable

fairing on the tow cable. These towing depths may be

calcu-lated u8ing the procedure of Reference 1.

The special instructions for connecting the tow cable to the towataff are given in Figure 5 which also shows the assembly of transducer, magnetic pickup, impeller, and

bear-ings. The modification made to the .towstaff to reduce the

effect of vibration, is also shown in Figure 5. This

con-sists of the addition of a six-inch section of rubber fairing whose shape is given in Reference .6. This rubber fairing

substantially reduces the ef1fect of cable vibrations at the towataff and prolongs the life of the tow cable.

The instrumentation is housed in a cabinet, as shown in

Figure

6.

This cabinet may be located in some convenient

plac and connected to a standard 115 volts 60 cpa a-c source.

The lead from the cabinet is plugged Into the connect3r from the tow cable and the operation is automatic when the power

is turned on. The followIng figures show the electronic

instrumentation; Figure 7-block diagram, Figure 8-circuit

diagram, Figure 9-power supply. A parts list of the

instru-mentation and power supply' are included0 Additional

infor-mation on the design and construction of the electronic instrumentation may be obtained from the preliminary report by Mr. HDBOO. Davis, entitled "The Circuitry of An Aecurate High Resolution Knotmeter TMB Type 205", October

195k.

9

TABLE 1

Parts List for TMB Knotmeter Type 205A

Instrumentation

Ri

3M R31

100 K

R61

k.7K

R2 150 Ohm R32

2k K

R62 20 M R3 1470 K R33 214 K R63 147 K

27 'X

R314

33 K

R614

200 K

R5

180 K

R35

50 K Precision

.R65 147 K R6 150 Ohm R36 50 K Potentiometer R66 _{147 K} R7

15 K

R37

50 K

Precision _R67

_{270 K}

R8 .5M R38

22 K

R68

270 K

R9

150 Ohm

R39

22 K

R69

100 K

RiO

5 K

Rk0 2 M R70

12 K

Ru

27 K

Mi

1.8 K

R71

100 K

R12 147 K

M2

18 K

R72 1 M R13 150 Ohm R143 210K R73

220 K

Rik

150 Ohm

R1414

270 K

R714

10 K

Rik

_.5M R145

390 K

R75

,5 M

ni6

2 M n146

50 K

Potentiometer _{R76 147 K} R17

22 K

Rk7 147 K R77

100 K

22 K

nk8

147 K R78

10 K Pot.

R19

1.8 K

R1#9 14.7 K R79

500 Ohm

R20

18

K _R50

390 K

R80

220 K

R21

_270K

R5].

50

K Potentiometer R81

120 K

R22

270 K

R52 5M R82

27 K

R23

100 K

R53 147K R83

10 K

R2k

100 K

R514 147 K R814

150 Ohm 10 W

R25

20 K

R55 14,7 K C2

.1 pit

R26

25 K lOW R56

50 K

Potentiometer C3

20

D R27 R5.7

390 K

014

.01 pe

I28

100. K R58 10 M 140 pipit R29

51K

R59 14 K C6

.01 pf

R30

.5 M

'R60

47 .K

.5 pf

c8 C9

do

100 141f 100 )1f 20 !4FD Cli .01 if C12 C13

8

i'

Clk Picked to set Oscillator Frequency C15

.05

)lf Silver

Mica

ci6

.1

.if

Cii

.1 pif.

ci8 .01 if'

C19

C20

40 ppf

C21

40 pjif

C22

.0011.5 uf

C23 14Q

ijif

C2k

O3 p

C25

15 zf

C26

150 ,if

C27

50 if

C28

50 pif

C29

01 if.

C30

100 ;ipf

C31 25 .1f C32 .01 pf C33

.01 if

V-k

581k

v-S

581k

v-6

5814 10 TABLE 2 (Qon1.) V-T

5963

v-k

V-3 5727 V-9

*5814

V-].O 6Au6 v-il 6Au6 V-12

5814

_V-6

V-13

5963

58lk

Crystal Diode D-1 N63

t-2

.1N63 D-3 1N63 SI-DPST 52-DPST

V-5

TP-1

TP-2

TP-3 TP-k

TP-5

TP-.6

I-1

H-]. H-2 H-3 8 Pinconnector for D.C,VO B1

8

Pinconnector

for D.C.VC, B1

8 Pinconnector

for DSC.V. B1

Banana Jacks Banana Jacks

Banana

Jacks Banana Jacks Banana Jacks Banana: Jacks Even Pilot Light NEON 6w 110 V 6w 110 V 6w. 110 V AN3102-16S-5P V-2 _{:AN3O5_2O_16P} V-3 PtflConnector for D.CSV. B1

v-i

5814

Connectors. V-2 _.581k V-3

581k

R1

12K

10 Watts R2 100 K 1 Watt. R3

.k7X

iWatt

RLI 180 K 1 Watt R5

82K

lWatt

R6

500

K 1 watt R7 10 K I Watt. R8 kO K 1 Watt R9 10 K 10 Watts

RiO 1 Meg. 1 Watt Ru 1 Meg. .1 Wat;t R12 100 K .1 Watt R13 100 K . 1 Watt Capacitors ci k !IFD 600

VD.C.

C2 k MFD 600 V.D. C,. 03 k )IFD

600

V0D.C.

ck

.1 MFD kOO V.DOC. C5 8 NPD LI.50V.D.C,

c6

8

D

k50 v0n.00

Transformers

T1. Chicago .PV 200 R2 21FQ8 fil. .1 Amp. 11 TABLE 2

Knotmeter Type 205A Power Supply

Re si store Iiduc tore

Li

8Hen'y 150 Ma.

L2 8,Hez'y 150 Ma. .L3

8Heiary kOMa.

ValTe8 vi.

5'L.

.V2.

66&

V3 6Au6 )4. . 0A2 V5 0A2

v6

6x

Miscellaneous

SWI

S,PJ.T.

Fuse

3 Amp,

12

REFERENCES

Pode, Leonard, "Tables for Computing the Equilibrium COn-figuration of Flexible Cable in a Ur.Uorm Stream",. TLVIB

Report

_687,

March

_1951.

Fehiner, Leo F, "The Hydrodynamic 'Properties

Of the

Air-Towed Sonar Housing". CONPID1TIAL Report -76 April.

1911.8..

Joers, J. E. "The Development of the Air 'rowed Scanning

Sonar Housing". T CONFIDENTIAL Report 0-351, July

_1951.

Munk1 Max, "The Aerodynamic Forces on Airship Hulls", NACA

TR 15k, 1923.

Lamb, H., "Hydrodynamics", Sixth Edition,

Dover

Publications,

New York,

19k5, page

155.

Drawing E-929-lO.

Johnson, J. L. "The Static Stability

:oerivat5.esof a

Series of Related Bodies of Revolution , 'iB CONFIDENTIAL

1

13

INITIAL DISTRIBUTION

Copies

11 _{Chief, Bureau of Ships, Technical LI-.}

brary (Code 312) for distributIon:

5 -

Technical IIbrary

1 - Technical Assistant to Chief o the

Bureau (Code 106)

Chief, Bureau of Aeronautio8 (Aeronautics and Hydrodynamics) Washington, D. C.

Naval Research Establisbinent

Halifax, Nova Scotia

Attn: Mr. Michael Eames

1 _{Commander, Portsmouth Nàv1 Shipyard}

Portsmouth, New Hampshire

.1 Commanding Officer, Surface Anti-Submarire

Development Detachment, Key Florida

1 Commanding Officer and Director .IJ. S. Navy

Mine Defense Laboratory, Panama City, Florida

2 Commanding Offiôer and Director, U. S. Navy Underwater Sound Laboratory, Fort Trumbell,

ew London, ConnectIcut

1 - Attn: Mr. Don Nicols

1 Commander, Naval Ordnance

]Aboratory

White Oak, Silver Spring,

_Maryland

2 Commander, CharlestQn Naval Shipyard Charleston, SQJ1

OaróUna

1 - Attn: E. D. Bigger8taff

1 _{Conunandng. 0ffieer and Director}

U. S. Nva1 Electronics Iaxatory,

San Diego, Califez'nia

1 Commander, Naval Or4nanCe Ltet Station,

continued: Copies

1 _{Director, Bureau of tanda±"ds,}

Washington

16, D. C.

Director, Naval Research Laboratory, Washington 25, D. C.

Mr. L. Fehiner, John Hopkins, Applied

Physics Laboratory, Silver Spring,

Maryland

Commanding Officer and Director, Engineering Experiment Station,

Annapolis, Maryland

Director, Georgia Institute of Technology,

680 Cherry Street, Atlanta, Georgia

1 - Attn: Mr. Ward Sachs

Commander, Noi'Thli..N4ya1 Shipyard,.

Norfolk, Virginia

British Joint Services Mission (Navy stáf)

P. 0. Box 165,

Benjamin Franklin Station,

Washington, D. C0

Naval Member

Canadian Joint Staff

2450

Maa3achn5étt Avenue, Washington, D0 C 1 1 2

9

3

5

I I - L

400

100 80 40 20

A

Its

15 Its

25 Its

30 Its

20 Its

Scope. of Cable in feet.

Figure 4.-Depth of TMB Knotmeter as a Function of Speed and Scope of Cable

£ iGI%C-2TAP A%% oN 346C, A SNowI% %N PC '-S ft%-4 T #S5'r.Tq TPPP"6 L%OJ ONPC%4 H6fl %L PC %-4 0%N..' ro RodS .%DS 4-SEE SuB-flCM&y OF FAIRINO E-959-I I. Gl.N I'Ft -

-i1

0 lP1iI

M. VENT HOtES LOCATE AS cHowNOil YCATICAL S

/.

j

Figure 5-Assembly Drawlng.of Towed Body

005- SAAi C.A.wkAC

NOTE.

riMs s,ioww 450.?T or PoSrTi.,il

(TO HE SC Al TA wING.)

GMv_wA_ 4O -I- MOUSiM, WIR8. ROiM y .4MTt

PC i-i ow o,i i -2%_NiM IIIbWIOiJL wiw ow vi

MOV CU%_.

3- CLAAH T%wN%o viiwos , ow

WDqOcNLoiMtc ACID.

4.-T%bI W1iM5j5 WITh PUH TIN (pwo-r,.., lA-*CI$(.

CA%, FiMOM r1w. VHI%%C.VI W5.LT8 Al LID 2)

3-DiMiM iOII.D wi INTO 6OC.IItT,

WHIC.14 AN %%S% T0 350p

I -POU,i ISoCcvr_{M&5. ct to % rI*}UL.I.. WIlbH 2CIN.

Si.. VO7 3WJ3TVi $'( VowOly 1W' L%.C.TIHIC. CKSi%. CI.WT53I.pou

A1

1 _{t4T$ MdØ%.}

3oIAE5Aj$f5-AIAP11tNL CDNNSCTOJI. CLCTRIC PRObOcfl_{LAB. IMC.} 45 6% tAVtW$IiIH MW. - CiMII!.4a 41 IlL.

MU5T BE TRIMMED ZERO IN WATER

LLECTRICAL CONNEc .TO iM

KEYS I8OAIINJIT

II AND MM.D5. WAI !.

LOCATE A1 ASSEMBLY

PROOp G.Y CO 23$

CL 4 FIT IN NI.

Sit 5LI?O RSSWJLY

c-rn-s

46 S4GSWW 2VD 7 4WXCZ. A:I IP

NP21..5].22

11-5-53

MPi3P4ET%C PICK UP

(4)

0Sc

(2)

WAVE SHAPER

(3)

DOUBLER a' GATE

(5)

SCALER

+500

Figure 7 Block Diagram TMB Knotmeter Type 205A

COUNTERS

(9)

IMPULSE GENERATOR N) H

(6).

GATE CONTROL

C)

AUTO RESET

(8)

BLANK

UI

O5CILLATOI

SIGNAL S GNAL WAVE

AMPLIFIER AMP IFIER SHAPER

OSCILLATOR TANK OVEN I 4110 4140 IWpIfl. yO 8c.A&i l__F1L_. FAN MOTOR

WAVE AD,JUST IST ADJUST 2-ND ADJUST 3RD GATE

SHAPER SC.IG SCALER SC.IO SCALER 5C. SCALER CONTROL.

WE

+ 300

+

RESET DECIMAL COUNTING UNITS

LB-V AC ALL. FILAMENTS 22, RIS .5M N SF1114 MUL METAl.

m.Trn

HI HZ 143'

I

I'

-I 4-S V AC - DECIMAL. COUNTING UNITS FiLAMENTS-BLANKING

Figure 8-Circuit Diagram TMB Knotmeter Type 205A

(ID VAC TO COO. DECiMAl. COISIrING UNITS 1.1040!. NOTE PRECISION RESISTORO.

ALL VOLTAGE MEASURED WIN- H.P UCOEL. 4108 -VLM

WITH SI IN lEST-POSITION.

ENCIRCLED N" REFER TO BLOCK N" OF'DLOCI( 8(!AIA

-KNOTMETE,R TYPE 2054 NAVY DEPARTMENT MECNGTCII,O. 229 SMElT I CF

-3A FUSE

swi

AC. INPUT

fl.

CHICAGC I C. pv200

T2

2 I FO 8 I AMP

23

63-v L3 20052 BR845.

VI

5V4 G TNAD 6040 CL ThJAD 604Q C3, RI 12K ISO

y

° S 6X5

R7

Figure 9-Power Supply Diagram TMB Knotmeter Type 205A

0

-+300 R 10 114 4O0V UNREGULATED C.

0

0

E [DRAWN CHECKED& REVIEWED.L -150

POWER SUPPLY

FOR USE WITH

K NOTMETER.

TYPE 2O5 NAVY DEPARTMENT WASHINGTON, D.0 DAVID W TAYLOR MODEL BASIN %ITONIO

z C

DIAGRAM SHEET I OF

_TI

+ C5 + 0 B D 0 -4---3105-20-16 S