SSC-164

M -[1””::; j_;~i;z,3,;/y

Results From Full-Scale Measurements

of Midship Bending Stresses on

Two C4-S-B5 Dry-Cargo Ships

Operating in North Atlantic Service

by

D. J. FRITCHF. C. BAILEY

and

N. S. WISE

SHIP STRUCTURE COMMITTEE

SHIP STRUCTURE COMMITTEE

MEMBER AGENCIEY

BUREAU 0. S.?,,, D,?,. OF NAVY

Ml,,,,, ” SE. 1?+.. s,’0.,.7 (0. SE FW8CE, D,,,. 0. N.v”

U.,,,. S,.TES C..., GUARD, T, . . ...” DEPT.

MA.,,, M. A. M>N,,T.A7 )0., D..,. 0. Co..,..,

A“..,... B“.... o, SHIPPING

ADDRESS CORRESPONDENCE TO:

SECRET..”s,,, ,TR”.T.. E co..,,,,.

U, S. COAST G“.!?. HFAOOUARTER5

WA, H, N. TON 25, D. c.

September 1964

Dear Sir:

The Ship Structure Committee is currently sponsoring a projectat Lessens and Associates, Inc. , that is measuring the vertical bendingmoments on ocean-going ships.

Herewith is a copy of the fourth progress report, SSC-164, &suits from Full-Scale Measurements of Midship Bending Stresses on TwoC4-S-B5 Dry-Cargo Ships Operating in North Atlantic Service by D. J.Fritch, F. C. Bailey and N. S. Wise.

The project is being conducted under the advisory guidance ofthe Ship Hull Research Committee of the National Academy of Sciences-

National Research Council.

Please address any comments concerning this report to theSecretary, Ship Structure Committee.

Sincerely yours,

/’

p< ~

John B. OrenRear Admiral, U. S. Coast GuardChairman, Ship Structure

Committee

SSC -164

Fourth Progress Reportof

Project SR-153“Ship Response Statistics”

to the

Ship Structure Committee

RESULTS FROM FULL-SCALE MEASUREMENTS OF MIDSHIPBENDING STRESSES ON TWO C4-S-B5 DRY-CARGO SHIPS

OPERATING IN NORTH ATLANTIC SERVICE

by

D. ~. FritchF. C. Bailey

andN. S. Wise

Lessells and Associates, Inc.Waltham 54, Massachusetts

under

Department of the NavyBureau of Ships Contract NObs-88349

Washington, D. C .National Academy of Sciences-National Research Council

September 1964

ABSTRACT

Records of wave-induced midship bending stresses have

been obtained on magnetic tape during the past three years using

an unmanned instrumentation system . The reduced data cover

thirty-four round trip voyages of two instrumented C4-S-B5 (ma-

chinery aft) dry-cargo vessels on the North Atlantic trade route.

The data represent about 12, 000 hours at sea out of five ship-

years Of Operation. Each data point is based on a one-half hour

record representing four hours of ship operation. According to

past experience, better than 807, effectiveness can be expected

from the unattended data collecting system. An automatic Proba-

bility Analyzer is used in the reduction of data.

All available data have been reduced and are presented

as plots ofrms stress variation and maximum peak-to-peak stress

variation vs. sea state (Beaufort Wind Scale ). Statistical

methods are presently available for the prediction of extreme

loads from the data.

The data have been shown to be representative of a class

of ships exposed to sea states corresponding to Beaufort Numbers

3-7. More data are needed at the higher sea states, on other

ship types, and other trade routes.

The reduced data and tapes are available to interested

groups through the Investigators or the Secretary, Ship Structure

Committee.

CONTENTS

I.

II.

III .

IV.

v.

VI.

2Q!i!s

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . ...1

A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

B. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Results ofData Reduction . . . . . . . . . . . . . . . . . . . . 7

Discussion of Results of Data Reduction . . . . . . . . . . 7

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Acknowledgements . . . . . . . . . . . . . . . . . . . . . ...21

References . . . . . . . . . . . . . . . . . . . . . . . . . . ...21

APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Description of Data Reduction Technique . . . . . . . . . . . . . 22

A. System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

B. Techniwe of Data Reduction . . . . . . . . . . . . . . . 26

C. Model PA 102 Probability Analyzer . . . . . . . . . . . 26

NATIONAL ACADEMY OF SCIENCES-NATIONAL RESEARCH COUNCIL

Division of Engineering & Industrial Research

SR-153 Project Advisory Committee

“ Ship Response Statistics”

for the

Ship Hull Research Committee

Chairman:

C. O. DohrenwendRensselaer Polytechnic Institute

Members:

J, P. Den HartogMassachusetts Institute of Technology

N. H. JasperU. S. Naval Mine Defense laboratory

E. V. LewisWebb Institute of Naval Architecture

R. L. McDougalLockheed Aircraft Corp.

Wilbur MarksOceanics, Inc.

I. INTRODUCTION

A. General

This report represents the completion of the second phaseof Ship Structure Committee Reject SR-153: Statistical Studies ofSeaway Loads Aboard Ship. Phase two has involved the recording, reduc-tion, and preliminary analysis of midship bending stresses from twoC4-S-B5 dry-cargo vessels* in North Atlantic service. During the periodfrom November 1960 to January 1964, the averaged o“tp”t of electricalresistance stress gages mounted amidship on the port and starboardgunwales has been recorded on a single charnel of a magnetic taperecorder aboard each ship. Data are automatically recorded for thirtyminutes each four hours, and centinuously whenever stresses exceed apreset level.

The recorded signal results from a combination of bendingmoments produced by still water loading, waves, slauming, and diurnaltemperature variation. During reduction of the data, al1 componentsare removed by filtering except the signal representing the stress inthe fore and aft direction induced at the gage location by the verticalcomponent of the wave-induced longitudinal bending moment; i.e., thestresses resulting from hogging and sagging.

At the end of 1963, after approximately five ship-years ofoperation on the two instrumented ships, the collected data representedabout 12,000 hours of ship operation. At this point, the instrumenta-tion was removed from one of the ships (S. S. HOOSIER STATE) forreinstallation aboard a different type of dry-cargo vessel, and theequipment remaining aboard the second vessel (S. S. WOLVERINS STATE)was converted to record the outputs of the port and starboard stressgages separately. The port and starboard records may then either becombined during data reduction, to simulate the previous data, orexamined individual 1y. Thus, a relationship between the averagedstress and the individual port and starboard stresses may be determined.

Because of the above mentioned change of ship type and thechange in the data recording practice on the remaining C4, this wouldseem an opportune time to report on the experience and results of datacollection and reduction to &te.

The first phase of this project, covering the period fromNay 1959 to November 1960, involved the development and installationof an unmanned system for recording stresses aboard shi

r“It has been

documented in Ship Structure Comnittee Report SSC-150 ( ).**

A secor,dShip Structure Ccmmittee Report, SS~-153 (2) reportssome early experience in employing manual reduction techniques on thetaped data.

A third Ship Structure committee Report SSC-159 ‘3) covers a

period, tiay 1961 to June 1963, during which the Office of the Chief ofTransportation, Department of the Army, participated in an extension of

*The particulars of C4-S-B5 vessels are presented in Table 7. (appendix)

**See List of References, Section VI

-2-

the project to record wave-induced accelerations at several locations onone of the C4 Vessels (S. S. WOLVERINS STATE) for the purpose ofdetermining seaway-induced loads on shiphorne cargo.

B. Background

Studies of the seaway loading on ships have been pursuedintermittently since the beginning of iron and steel shipbuilding.However, the present project, SR-153, represents the first systematiclong-range study of seaway loading on operating merchant dry-cargovessels of the United States. Similar studies on a more llmited basishave been performed in other countries - notably in England, France,Japan, and Sweden. An attempt is being made to integrate the programsand results of these studies through The Conraitteeon Response to WaveLoads of the International Ship Structures Congress (4).

Tbe irregular character of the seaway has dictated a statis-tical approach to the analysis of ship response to seaway loads and theprediction of extreme values of loads on ship structures. The firstmajor step in the statistical interpretation and analysis of seawayloads was the result of the work of Dr. Norman H. Jasper in the earlyand middle 1950’s while he was at the David Taylor Model Basin (5).

In order to provide background data for the application oftheee statistical methods, data must be collected over a long period oftime. To meet this requirement, Dr. Jasper and the David Taylor ModelBasin developed equipment which simultaneously measured and analyzed thewave stresses into number of occurrences at preset stress levels right onthe ship.

It was expected that Project SR-153 would continue with thecollection of analyzed data by applying Dr. Jasper’s method and equipment,which had previously been used mainly with naval and Coast Guard vessels,to operating cormnerclalvessels on various trade routes. However, indetermining the philosophy under which the project would operate, it wasrecognized that the data should be recorded in analog fono so that asnew analysis techniques developed, they could be applied to the datawithout requiring another long-term program. Magnetic tape recordingoffered a means of accomplishing the desired result. It provided ❑ eans

of recording and storing data in a convenient form which would beaccessible in the future for digital computer and power spectrumanalysis if these types of analysis should become appropriate.

An American Bureau of Shipping project current1y active

at Webb Institute of Naval Architecture (6) has provided the first

opportunity for application of the collected and reduced data. The

reduced data have been furnished to the Webb group as they becomeavailable.

The work of R. Bennet of Sweden at Webb Institute duringthe fall of 1962 and the spring of 1963 (9, 10) has represented thefirst extensive application of full-scale ship data, including thatfrom Project SR-153, in the prediction of extreme values of seawaloads. JIn Bennet’s approach, presented in detail in Reference (9 ,data collected on a given ship type operating on a specified traderoute may be used to derive the response of the same ship operatingon any other trade route for which statistical data on seaway

-3-

conditions are available. Utilizing the stress and seaway datacollected aboard ship on the given trade route, a generalizedstatistical response characteristic is developed. This character-istic represents the average response of the ship to each sea stateon the Beaufort Wind Scale.* Combining this general ized responsecharacteristic with the observed statistical distribution of seaconditions for another trade route provides an overall responsecharacteristic for the same ship operating on the other trade route.The derived characteristic thus permits expected extreme values ofseaway loads to be determined for the given ship operating on any

specified trade routes.

The investigators have cooperated with The Society ofNaval Architects and Marine Engineers in their effm-ts to encouragethe operators of ocean-going tankers (7s 8) and Great Lakes orecarriers to participate in the collection of long-term data onseaway loading of these types of vessels,

Ouring 1963, all available data were reduced using theSierra Research Probability Analyzer which became operational early

in the year. The method of data reduction utilizing the ProbabilityAnalyser is described in the Appendix.

As a resdt of the work at Webb Institute and at the SwedishShipbuilding Research Foundation it became apparent early in 1963 thata simple and direct method of handling bending moment data would involvecorrelations between the root-mean-square stress variationwrepre senta-tive of each data interval and sea state encountered during the interval.All data from both ships were placed in this form (see Figures 1-6) andthe pattems observed were general 1y similar to those found for severalSwedish ships studied in a like manner (11). The total data represented

4968 hours at sea for the S.S. HOOSIER STATE and 6828 hours at sea forthe S. S. WOLVERINE STATE.

Data reduction and presentation will continue. An investiga-tion of digital computer technlques is under way to determine the

applicability of these techniques to the calculations involved in thefinal stages of data reduction after the basic output is obtained fromthe Robability Analyzer, and the compilation of these results withpertinent information from the data logs for use in future analysis.If the results of this investigation are satisfactory, the investigatorsplan to switch to the use of machine computations with a resultant savingin man-hours and an expected increase in accuracy over present manualcalculations. An added advantage is that the accunmlated reduced datawill then be available in punched card form for various analysis tech-niques which can be performed rapidly on a generalized digital computer.

**The term stress variation 1S defined as the vertical distancefrom crest to adjacent trough or trough to adjscent crest onan oscillographic record of stress signals. See Reference(2),

—

*The use of the term sea state thro”gbo”t the remainder of thisreport will refer to numbers on the Beaufort Wind SCale (see“table6). (appendix)

-5-

4.,

b,.0

2.,

11111~,,,,,64

0NSw

,7 -,4 5,,8 ,,. ,,, ,

SEA ,,.,, ,BEAUEO,T w,..SCALE)

FIG . 3. RMS STRESS VERSUS SEA STATE (COMPARISON OF 4TH ORDER CURVES FOR

EACH SHIP AND COMBINATION OF BOTHj

-6-

FIG .5. MAKIMUM PEAK-TO-PEAK STRESS VS. SEA STATE (S.S .WOLVERINE STATE)

8,,*

7.0/

/

6.0 ,>

v,X” ,/:/” e

i! ,.. XY “g

,,6“

A “

J */’ ,,. ~,/~ 4,0 / .,.-; / ~,/

,. ./.~,,a /b*

/

< ‘.. @ “.. AVERAGE,0,.,sa .J--”- ~, x “OOS,E.~ z,. ---- 0 wOLvuvlm

..+ ~. ==. A COMB,...● .—.

4“ LXDELJIT~ ---- ,omlER

,.0_,_, -woLvERm,— c 0.,1.,.

,,,,,64m o NSw

‘Z, , ,6, ,, ,, ,, ,,

SEA STATE ,BEAUFORT WIND ,..,.,

FIG .6. MAXIMUM PEAK-TO-PEAK STRSSS VS. SEA STATE(COMPARISON OF 4TH ORDERCURVES FOR EACH SHIP AND COMBINATION OF BOTH)

-7-

11. RSSULTS OF DATA IU3DUCTION

Reduced data which have been collected during approximatelyfive ship-years of operation of C4 (Machinery-aft) vessels in NorthAtlantic service are now available. The data cover fourteen round-tripvoyages of the S. S. HOOSIER SIATE between November 1960 and June lg63and twenty round.trip voyages of a dst er ship, the S. S. WOLVERIN8 STATEbetween December 1961 and January 1964. Tables 1 and 2 entitled “CurrentTape Data” indicate the disposition of the reels of magmtic data taperecorded aboard each of the ships.

The results of data reduction have been accumulated by theInvestigators on work sheets similar to Figure 17. These work sheetsalso include selected information on ship operation, weather, and seaconditions from a data 10S maintained for the project by the ship’sofficers. The parauw ters of particular interest for each reducedinterval (one half -hour record for each four houre of ship operation)are the rms stress variation ( ~E) and the maxfmum recorded peak-to-peak stress variation ~). These quantities are particularly usefulfor the prediction of extreme values of seaway loading when plottedasainst sea state in a procedure proposed by R. Bennet of Sweden ( 9).Figures 1 and 2 present all available rms stress data from each chipvs. sea state. Figures 4 and 5 present all available maximum peak-topeak stress data ve. sea state. Each point on these figures correspondsto the reduced data from a half-hour record representative of four hoursof ship operation. The average values of all the data points withineach sea state have been calculated and are shown on the plots.

Curves of the best fourth order least square polynomialfit to these average values were determined in a digital computerstudy. The result ing curves for the individual ships and for thecombined data from both ships are presentad in Figures 3 (zms stress)and 6 (maximum peak-to-peak stress). The average points for eachship and for the combined data are indicated on these figures.

A similar fourth order plot, Figure 13, was made earlierin the projecc of data from an approximately equal nuaber ~fvoyages of both ships.

Figures 7 and 8 are combined plots representing the beatvisual fit through calculated average values of rutsstress variationand maximum stress variation respectively as a function of sea stateunder different ship headings based on data from 11 voyages of theS. S. WOLVERINE STATE.

Figures 9 and 10 are graphs indicating the distribution ofthe time spent by each ship in various sea states during the totaltime represented by the reduced data (4,964 hours of operation of

S. S. HOOSIER STATE, 6,828 hours of S. S. WOLVERINE STATE). Figures11 and 12 give similar data on ttie spent at various ship speeds.

III DISCUSSION OF RESULTS OF DATA REDUCTION

The reduction and preliminary analysis of the tape recordeddata take place in the Investigators’ Laboratory using the equipment

pictured in Figure 14. The data tapes consist of half-hour s8mplesof bending stress signals recorded once during ,each four hours of ship

operation at sea with extended records during heavy sea conditions.

(Manuscript continued on pg. 15)

ImtrwntVowKe N..

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

S15Vo,aEe No. ~

1231124

125/126

127/128

129/130

131/132

133/134

1351136

137/138

139/140

161/142

143/144

1451146

147{148

1&91150

151/152

153/154

135/156

1571158

159/160

161/162

123H12411

No hp.,

NO Tap,

129-130H

NO Tq.e.

No T.p a

no T.*e.

137.138H

139-140H

141-142H

143- lUH

MS-146%

1&7-148E

149.150H

151-152H

153-154H

155-156H

157- 158tI

159-160S

161-162H

TASI.E 1. CURRENT TAPE DATA(S. S. HOOSIER STATE)-riti ,b n=gfk~

- Jcak No. ~t Tam Data and Remarks

1

2

3

4

5

9

10

8611

12

13

22

22

?.4

25

41

31

28

29

11/18160 12119t60

12125160 1119161

1131/61 3/5/61

318/61 S17161

5112161 6/14/61

6/16/61 7I1OI61

7111161 8111161

8/16/61 918161

9115161 10I1OI61

10I17I61 1118161

11tL2\61 1216161

12/12/61 115162

1I1OI62 2J8162

2112162 3112162

3J17162 4114162

4119162 5120162

617162 6129162

117162 11’29162

8116162 917162

9113162 10IIOI62

8

8

8

8

8

8

8

14

M

16

14

14

14

14

14

14

14

14

14

14

OK

OK

OK

w

OK

OK

OK

OK

OK

OK

07.

m Osc Failure. No data; had tape dagaussed 313161

Stress Xduc, trouble early in voyaze. No data( 10 hours).

Co”Id mot rqw,ir Xd,wr until ,.,.,. 517.(corroded c.arpensation gages. ) (5/8-5/9Xd”cr repairs. )

13 mitt. titmr trcable. Date to Norfolk (no “,1,. )ran continuously. officers shut dc..nl system

x. data. No calibration. Fuse failure SCMtm &ys before arrival W“ York City.

Relief M“, M-C ,et trouble (over spaed) . Speedcontrolre,i.torown 8/8/61. Repatred ,.s1s,,?,replaced strain gaze aqlifier. Installed tramistcmelec. and 16 track head.

Noise, ml.sin2 calibration. Data o“ Ch 1-2 only,few g-d ir,,erval, but cemot match 1%.

Installed new Video l“, trumcmt# A@ifler Model602A, Serial N&r 189,

Noise, carrier .Utting m,.

cc-+.tereturntripmissir.z.

D@ta on chanwl 1-2 only. Noi,e, m3, siw ,alibra.tima; relief w“; .amt Mtch e.trie, in 102book. Not .aF..re,.d on return voyqe.

I.strm.,Voyaw N..

21

22

23

24

25

26

27

28

29

30

31

TABLE1. (CONTINUED)

$m ~ Record HeadVOyage NO. Reel NO Log 3.wk NO. ~ - ‘ITaek, TaPe Data and Remarks.

163/164

165/166

167/148

169/170

171/172

1731174

1751176

177/118

179/180

181/182

183/134

163-164H

165-166H

NO ?.1~

169-170Fl

171-172M

173-17f+R

175-176H

177 -178H

179-180H

181-182R

183-134H

30

53

54

55

67

63

62

64

65

66

67

10/17162 11/13/62

11/18/62 12/10/62

12/12/62 1/14/63

1116163 21 7/63

2/15163 3116/63

3122163 4113163

4120163 5115163

3122163 6116/63

6124163 7118163

1126163 81 L9163

8131163 9[22163

14

14

14

14

14

14

14

14

M

W

Noise.

Diode failure, “O record, tape revised.

Failure of port gage, “Oisy.

Maise .

4115 - Installed welded $*,s - RECIDJF

S120 . NSW imetal led correct calibrationresistor .

Noise (carrier ir,cermitte.c ) .

Noise, rq.laced cho~~r 1. Video InstrumentsI&&l 602A, Serial Nc.. 189. Rqlaeed 70 mfd.25v c+aeimr ,,lealq.”.

Noise, tape ,,.IISPWC removed at end of VOY.S,for factory servicing .

+

TABLE 2. CURRSNT TAPE DATA (S. S . WOLVSRINE STATE)

~

17mi117CW2

172w1172!42172W3

174UI174W2174!J3174W

176Wl176W2176w3

178wI178W2178!?3

18M180X218!%”3

182WI182W2

.0 tapes

18$w1186W2186w3

122ul188W2182W3

19~19Gw2190Z3

192W3192W2192!d3

194W3194!42194w3

196Wl196W’2

196W3

Ins,.mntvoyage No.

1

2

SULV.yag. No.

170/171

172/173

174!17s

176/177

17.3/179

180/181

182/183

L&l 185

186/187

188/189

190/191

192/193

194/195

196/197

Date M cord HeedLag 3oek No. ~—w Tracks lace Data and Remark,

1114162

2122162

416162

518162

14

16

OK W12 N. calibration signals, w15, W17 N. data.1. Report6661i11 (b)

In Report6661L11 (b)

12/21/61

1/23/62 OKOKOK

3 26, 27 OKOKOKOK

‘ 17 b/11/62 I& OKOKOK W31 N. caltbra, im signal,, could not anal) ..,.

OKOKOK

m

5 35

6 36 6/10/62

7/6/62

8115162

91 16/62

10/16/62

11114f62

12/9162

715162

8114162

9I1OJ62

10/16/62

11/9/62

12J7J62

114163

14

14

14

14

14

lb

14

14

14

m1 Track only W36 Only usable channel , all rest m data.

7

8

9

OKOK

w

OK

OK

OK

OKOK

OK

OK

OKOK

OK

OKOK

:m

OKOK

OK

No ta@., aq.lifiernotw.arki~ , replaced withspa,. .

W14Wz&

No data.Nodata.N9&t,.U34

10

11 50

12

13 56 lJ11163 2112J63

2117163 3120163

Nocalibrationsignals.+Iifler tro.ble.No calibration c.~nal.. (Replaced.)No calibration signal,.

No .3AU at b+ifir,g and end .af tap+. 33intervalsir,~ddle - allchanaele.T+,-,t be rewound before analy,l,.

W11W21W31

W237

I

TABLE2. (CONTINUED)

1.

I..truentVoPF.e No.

15

16

17

18

19

20

21

22

23

24

SmV..pm no.

198/199

201/202

203/20+

20512%

20712LM

209/210

211/212

213/214

215/216

217/218

Reel No.

198W1198W2

201W1

201W2

203W2203W2

2Oshl205W2

207V1207W2

209Wl205W2

Zllwl211W2211!+3

213W1213W2213W3

215!41

217Wl

217W2217W3217!+4217W3

* 2eco.d Headlug Book NO. ~

58

59

70

71

71

13

14

75

76

77

4123163

5128163

6/28163

7125163

9121163

10I19I63

11/30/63

12/18/63

4/19163

5/27/63

6/22163

7/20/63

0121163

9116/63

10/13163

11/14/63

121712.3

1I1OI64

14

14

14

14

14

14

14

OKOK

All new mtes; urable to operate equipment.Got coastwise data only. Removed acceler-ometers (both statistical and ,crain gaEe).

:

:

oxOK

OK

OK

OK

OK

OK

OK

%

OK cm. reel only. )iachine noc operated frmNeII York to Breerhaven .

QK Fiv. ,.,1s used; ,,3!4’, incorrectly supplied1.5 MU tape for 1.0 Mil tape.

:oxOK

!-1

-12-

4.0

,.5

,/’”

,,0/

/

TOTAL!+%

2.,

:HEAD \

\

{ 2’” /

/“\. . WOLLO .

: .: ./ ‘

~ l,,/“ .:s . s T \PnOAm

,~ ,/ -

./“ ../

,.0 A “</ ‘ ,0.,

/ .K/

{

/~ ‘+”

0.5 / . . . .,

/ pi- “

,< ‘

01,34 5670 9101112

SEA STATE ,BE.4UFORT WUJD SCALE)

FIG . 7. RMS STRESS VS, SEA STATE(COMBINED PLOT) (S, S . WOLVERINE STATE)

./’/

TOTAL x /’HEAD./ ‘5./

/ >/

/

>, , “-

/ < ~’0.-++

..-

,~/”,2,4 56?8 ,1 OIL!2

s,. STATE (F,EALWORT Wm. SCALE)

FIG . 8. MAXIMUM PEAK-TO-PEAK STRESS VS. SEA STATE (S. S . WOLVERINE STATE)

-13-

,600 l--

L L,0,

400

,0,El,,,,.

--+””- “0°

----1 ‘OO------1 40”

IIP!420078, ,,,,,, 0m.rmom, w, . . . . . . . .

ii,,

,.. ,,FIG. 9. NUMBER OF HOURS AT VARIOUS FIG. 10. NUMBER OF HOURS AT VARIOUSSEA STATES (S. S . HOOSIER STATE) SEA STATES (S. S . WOLVEFUNE STATE)

80,

SHm SPEED IN mom

FIG. 11. SHIP SPEED VS. HOURS (S. S. HOOSIER STATE)

-14-

,000

I

4.0

3.5

93.0

. .

,4+,,,7

= ,.5, .

& -~+.”, ,/0/ .,- ,- \.

~ ,,0/.+ +.. - .

.,-2E

~ ,.5 \r-”AVERAGEPOINTS

❑ .00s,,.

1.,WOLVERINE

:,......<- -

COMBINED

gY ‘- ..=___---- .~h0,.,, , m

----- HOO$,ER

0.,_—— —wo LvERE. E

— COMB,...

1 I ,0,,.,6, ,,,“

,234 5678 ?,,,,,,

SEA STATE ,BEAUFORT WIND S....,

FIG. 13. RMS STKSSS VS. SEA STATE (COMPARISON OF 4TH ORDER CURVES FOR EACHSHIP AND COMBINATION OF BOTH THROUGH JUNE 1963)

-15-

FIG. 14. PHOTOGMPH OF DATA ANALYSIS SYSTEM

In the basic data reduction procedure, a twenty minute portion of eachhalf-hour sample is automatically analyzed by the Probability Analyzerto provide a histogram of number of occurrences of peak-to-peak stressvariations within 16 preset levels, rutsstress variation ( ~E) , averagestress variation, maximum recorded peak-to-peak stress variation (~) ,and total number of stress variations which have been analyzed. Theoperation of che data analysis system a“d the technique for the reduc-tion of each half-hour sample to tabulated values of rum ar,dLreatestpeak-to-peak stress variation are prese,,ted i,,the APPENDIX alon~ withsamples of the Probability Analyzer output, a schematic of the datareduction procedure, and a sample work sheet for tabulating the reduceddata. (See Figures 15 - 17.) Peak-to-peak variations of stress arestudied in this project because of the difficulty in establishing stillwater stress level “he,, the ship is away from the dockside and becausethe statistical procedures for analyzin~ peai-to-peak values of randomvariables are well established.

Obtaining a static load calibration on each ship has becomeincreasingly fmporta”t as more data are collected. As a practicalmatter, obtaining such a calibration on a dry-cargo vessel is complicatedby limited time schedules and problems of inducing a large bending momentby shifting fuel oil and water ballast. Cargo handling does “Ot “s”allycontribute large bending moments. In the case of a tanke= or bulk carrier,the situation should be considerably simplified.

16-

FIG. 15. TYPICAL RECORD OF PROBABIL-

ITY ANALYZER OUTPUT

Q =OKF; 2,3d//

1.

z.

4.

.,..ss

. . . . . . . . . ,0.s

..0,4 .1,.,,, AN.,,.,..,c’”,,”,

,... s.”,,,,0. . . . .AN..,,.. ““,, UI

. . ..! . . ...10.

SEA . . . WIND,N, O.MAT *ON

,R.M ..,,. 1.-

FIG . 16. SCHEMATIC OF ANALYSIS OF

WAVE -INDUCED DATA

/4 2)... ,4s

FIG 17. TYPICAL WORKSHEET FOR CALCULATION AND REPORTING OF STRESS DATA

-17-

Reference is made to an earlier report (1) wherein calibration❑easurements on the S. S. HOOSIER STATE showed agreement between calculatedand measured bending moment change within 5 .5X. It is planned to makestatic load calibrations on the instrumented ships whenever the opportunitypresents itself.

Each tits point (in Figures 1, 2, 4, 5) is based on a twentyminute portion of the basic thirty minute sample record as was previouslystated and is assumed to represent four how?s of operation of the ship in

the seaway. The spread of the data points is observed to twn to aboutthree times the conap”tedaverage values in the lower sea states (l-5).This spread might be explained on the basis of the statistical mture ofthe data since the ship can operate at various headings relative to thesea and at various speeds within a given sea state. Since the reportedsea state information is based on visual observations, some spread inthese values as a result of individual interpretation is also likely. Inaddition, ship heading is not taken into account in these figures.

The number of stress variations counted during the analysisrange, in general, from about 200 to 500 per record interval.

The twenty minute record equsls one-twelfth of che four hour periodit represents. Thus, although the sample may be representative ofaverage conditions in terms of fi, there is a probability of onlyone in twelve (6%) that the greatest peak-to-peak stress variationwhich occurs will appear in the data sample. CM this basis, it ispossible that actual maximum peak-to-peak stress variations may runas much as 20% higher than those appearing in the sample record.This difference is predicted from the a roxfmate formula developedby Lonquet-I+iggin.$(~= #%!__ d where XKO is the mostprobable value of the maximum amplitude of stress variation for atotal of N variations occurring during a period when O, the rmsstress variation, remains constant (see Section 111.B. of Reference(2))) by assuming that the number of stress variations is increasedby a factor of twelve.

Although there are more data available from the S. S.WOLVERINE STATE by about 30% voyage and time-wise, a comparison ofthe fourth order curves of Figures 3 and 6 indicates good agreementbetween ships especially in the sea states 3 to 7 where most data

are available. Close agreement is to be expected since the shipsare of the same type operating on the same route. As data gatheringcontinues, more information in the higher sea states will becomeavailable to reinforce the trends of the curves in this region.

A review of reduced data available from both ships was madeto determine how the data from one ship compared with that from thesister ship. This study embraced 14 voyages of tbe S. S. HOOSIERSTATE between November 1960 and June 1963 and 13 voyages of theS. S. WOLVERINR STATE between December 1961 and April 1963; that is,all available data on the HOOSIER STATE and an approximately equiva-lent amount of data available on the WOLVERINS STATE and taken in

similar voyages. Tables 3 and k indicate the number of hours spentby each ship at various headings with respect to tbe seaway in thisseries of voyages, and Figures 11 and 12 show the number of hoursspent by each ship at the various speeds.

-18-

TABLE 3. NUMBER OF HOURS AT

VARIOUS HEADINGS (S. S . HOOSIER STATE)

TABLE 4. NUMBER OF HOUW AT

VARIOUS HEADINGS (S. S . WOLVERINE

STATE)

t“””-””--””

D,,. fr- ,,..,.8=smmi“, .,. ,,,,.,

w,,.~..““2i3-d

TABLE 5. COMPAF?JSON OF MACHINE AND MANUAL PEAK AND PEAK-TO-PEAK

STRESS DETERMINATION

31.2, 4.,, 4.68

n, ,.’, ,.7,

,,, ,.M ,,,,

4,0 ,.,0

.*.

,,,M ,,.,. ,,

Figure 13 presents the plots of average rms stress values forthe two ships individually and combined for these similar voyages andshows a very close agreement in response between the two. It was onthis basis that it was decided that both ships were providing informationcharacteristic of a class.

Table 5 summarizes a study to determine the differences whichwould result in the reduced data for Xm if the peak positive and peaknegative stress (occwring with respect to still water value) were deter-mined for each sample interval and added rather than considering the single

-19-

FI,G. 18.

PR”BABIL,T, A..,,,,,

E . ,. ,,,.,sr,~ —hi..”.. REDUCTION

E = 5. ,,(,,s,)2

JIIL

%

\l

\

L ‘.L 3

,.0

I I -,.0 4,0

O-PEAK s,..sS VARIATION (;HISTOGRAMS AND CORRESPONDING RAYLEIGH DISTRIBUTIONS (s. s.

WOLVERINE STATE)

greatest peak-to-peak variation. The results at higher stress levels(4-5 KPSI pk-pk) were found to agree within 7-87.in the worst caseand this order of difference was considered insignificant.

Figures 18 and 19 are examples of the good agreement obtainedbetween the results of machine and manual analysis.

The techniques for data gathering and reduction have provensuccessful. It remains now to continue to obtain and process moreinformation in order to increase reliability of the indicated trends,get more data in the extreme sea states, and apply the methods toadditional ship types and routes.

Iv. CONCLUSIONS

All available wave-induced stress data from 34 round-tripvoyages of C4 (machinery aft) dry-cargo vessels operating on NorthAtlantic trade routes have been reduced and are available for study.The data represent about 12,000 hours at sea recorded during fiveship-years of operation.

-20-

FIG . 19. LOG - NORMAL DISTRIBUTION OF fi VALUES (S. S . WOLVERINE STATE)

In one method of analyzing these data the rms values ofstress variation and the maximum peak-to-peak values were plottedagainst the sea state as measured by the standard Beaufort wind scale.These curves showed a consistent relationship.

The first vessel to be instrumented has provided useful datafrom 14 out of 31 round tuip voyages (45%), whereas the second systemhas provided data from 20 out of 24 voyages (82.5%). Considering thatthe shipboard instruments are, for all practical purposes, unattendedand the electronic components are operating centinuously, the performanceof the two shipboard units has been satisfactory. In the future, it

should be possible to plan on at least 807.effectiveness of the systemdepending on the interval at sea between the routine maintenance checksat each East Coast turn-around.

The Sierra Research Probability Analyzer has provided agreat savings in tfme and cost of data reduction and has permittedthe project to maintain data reduction on a current basis. A comparisonof the results of machine and manual reduction on several early voyages

bas proven the accuracy of the Probability Analyzer.

A comparison of the long-range data from the sister ships

vs. sea state indicates that the data from each are typical of the

-zl -

class of ships over the range of conditf.ons for which large amountsof data have been collected (Beaufort Numbers 3-7) with a trend con-tinuing through the higher sea states where data are sparce becausethe ships seldom encountered these higher sea states.

The fact that the data are representative of a class ofships has permitted the system installed on the first ship to beremoved for reinstallation aboard a new type of vessel withmachinery amidship. The second C4 is to continue the collection ofdata with the emphasis on the higher sea states (9 and above) .

The magnetic data tapes, data log books, and data reductionwork sheets (see Figure 17) are being stored at the Investigators’facility and are available to other wo~kers in the field. Inquiriesrelative to these items may be directed either to the Investigators,

or to the Secretary, Ship Structure Cotmnittee,U. S. Coast Guard Head-quarters, Washington, D. C.

V . ACKNOWLBDGEM?NTS

This project is sponsored by the Ship Structure Coaunitteeand is under the advisory guidance of the Ship HULL Reserach Committeeof the National Academy of Sciences, National Research Council. Theassistance of the Project Advisory Ccmmittee with Dr. C. O. Dohrenwendas Chairman is gratefully acknowledged.

The wholehearted cooperation of States Narine Lines, and inparticular, Messrs. E. P. Bainbridge, Neil Miller and the officers andmen of the S. S. HOOSIER STATE AND S. S. WOLVERINS STATE has been amajor factor in the success of the investigation to date. The con-tribution of States Narine Lines in the form of shipboard wiring andinstrument installation is particularly appreciated.

vI. REFERENCES

1.

2.

3.

4.

5.

6.

Fritch, D. J, and Bailey, F. C., f.nUnmanned System for Record in&Stresses and Acceleration on Ships at Sea, Ship Structure Counnittee

Report SSC-L50, .7urm1963.

Pritch, D. J., Bailey, F. C., and Wise, N. S.,of Bending Moment Data from Ships at Sea, Ship

RepOrt SSC-153, December 1963.

Bailey, F. c., Fritch, D. J., and Wise, N. S.,

Preliminary AnalvsisStructure Committee

Acquisition andAnalysis of Acceleration Data, Ship Structure Committee ReportSSC-159, February 1964.

Jasper, N. H., et al, Response to Wave Loads, David Taylor ModelBasin, Report 1537, June 1961.

Jasper, N. H., Statistical Distribution Patterns of Ocean Wavesand of Wave-induced Ship Stresses and Motions with EngineeringApplication, Transactions SWAf.D3,Volume 64, (1956).

Trends of Wave Bending Moments on Ship Hulls, Progress RepOrtS1-6 for American Bureau of Shipping, Webb Institute of NavalArchitecture, September 1962 - September 1963.

7.

8.

9.

10.

11.

12.

-22-

Wave Bending Moment Standards for oceangoing Tankers, Proposedproject of Panel HS-1 Hull Structure Committee SNAhl, Webb Instituteof Naval Architecture, October 1963.

ReccmcaendedProgram for Collection of Long Term Stress Data on Ocean-

Goin!zTankers - Data Acquisition System and Data Reduction and Pre-J.. sis, Lessens and Associates, Inc. Technical ReportNumber 8061 il7 (Prepared for Panel HS-1 of Hull Structure Com-mittee SW) 23 September 1963.

Bennet, R., A Comparison of Measured and Statistically CalculatedWave Stress Distributions Using Data from Four Voyages of S. S.WOLVERIIK? STATE, Progress Report Number 6 for American Bureau ofShipping, Webb Institute of Naval Architecture, June 1963.

Bennet, R., Xrends of Bending Moments in Irregular Seas:A@ysis of service Stress Data, Proqress Report Number 6 forAmerican Bureau of Shippin& Webb Institute of Naval Architecture,September 1963.

Bennet, R., Ivarson, A., and Nordenstrom, N., Results from FullScale Measurements and Predict ions of Wave Bending Moments Act in%on Ships, The Swedish Shipbuilding Research Foundation, Report32, 1962.

Lewis, E. V. and Gerard, G. eds. , A Long-Range Research Programin Ship Structural Desigr$Ship Strutture Committee Report NumberSSC-124, November 1959.

APPENDIX

DESCRIPTION OF DATA REDUCTION TECHNIQUES

A. System

The data reduction system as shown in Figure 14 consists ofthe Nagnet ic Tape Reproduce Unit, the Probability Analyzer (a specialpurpose computer) , and a Recording Oscillograph.

The tape reproduce unit accepts the 10% inch reels of oneinch wide tape which have been recorded on the ships using FM record-ing techniques. The data are played back at speeds up to 200 tf.mes(60 ips) the recording speed (0.3 ips), using 14 track IRIG headsand FM demodulation techniques.

The Probability Analyzer accepts the output signals of thetape reproduce unit, changes the latter’s analog signals to digitalform, performs tbe analysis, and translates the results back toanalog form for readout. In operation, the output of the tape unitis filtered by the probability analyzer’s input filter. This eliminatesall but the wave-induced data. These data, for a given record interval.

are then sorted by magnitude and stored as counts in one of sixteen levelcounters. Analysis is completed at the end of a preset time interval,a predetermined number of total counts, or when the storage capacity of

one of the level counters is reached. At this point, the system auto-matically stops the analysis and provides a readout cycle directly onthe recording oscillograph. The readout provides a histogram (bar

-23-

TABLE 6. TABLE OF BEAUFORT NUMBERS

Force Wind Speed

o Less than 1 kt

1 1-3 kt, mean 2 kt

2 4-6 kt, mean 5 kt

3 7-1o kt, ,nean 9 kt

b

7

11-16 kt, mean 13 kt

17-21 kt, mean 18 kt

22-27 kt, mean 24 kt

23-33 kt. mean 30 kt

8 34-40 kt, mean 37 kt

9 41-47 kt. mean 44 kt

10 48-55 kt, mean 52 kt

Description of Sea

Like a mirror,

Ripples , with the appearance, ofscales, are formed; but withoutfoam crests.

Small wavelets , stillshort butmore pronounced - crests have

;rgel~:.syappearance and do not

Large wavelets. Crests beginto break. Foam of glassy appear-ance. Perhaps scattered whitehorses.

Small waves becoming larger.Fairly frequent white horses.

Moderate waves, taking a morepro”ou”ced long form; many white

horses are formed. (Chance ofsome spray. )

Large waves begin to form, thewhite foam crests are more exten-

sive everywhere. (Probably somespray. )

Sea heaps up and white foam frombreaking waves begins to be blownIn streaks along the direction ofthe wind.

Moderately high wat.es of greaterlength, edges of crests begin tobreak into the spindrift. The foamis blown in well-marked streaksalong the direction of the wind.

High waves. Dense streaks offoam along the direction of the

wind. Crests of waves begin totopple, tumble and rcll over.

Spray tmiy affect visibility.

Very high waves with long over-hanging crests. The resultingfoam i“ great patches is blownin dense white streaks along thedirection of the wind. On thewhole, the surface of the seatakes a white appearance. Thetumbling of the sea becomes heavyand shock-like. Visibility affected

-z4-

TABLE 6 (Continued)

Force Wind Speed Description of Sea

11 56-63 kt, mean 60 kt Exceptionally high waves. (Smalland medium sized ships might befor a time lost to view behind thewaves. ) The sea is completelycovered with long white patchesof foam lying along the directionof the wind. Everywhere the edgesof the wave crests are blown intopath. Visibility affected.

12 64-71 kt, mean 68 kt The air is filledwith foam and

sp~a,y. Sea completely, white withd.lv~ng spray. Visibility veryseriously affected.

Note: The Beaufort Scale extends to force 17 (118kt.), but force 12is the highest which can be distinguished visually from the sea.

TABLE 7. TABLE OF PARTICULARS OF C4-S-B5 VESSELS

A, General

Original Name: MARINE RUNNER

Type: C4-S-B5 Machinery-Aft Dry Cargo Vessel

Builder: Sun Shipbuilding and Drydock CompanyChester, Pennsylvania

Date: September 1945

Hull Number: 359

Length Overall:

Length Between Perpendiculars:

Beam, Molded:

Depth, Molded:

Depth, Molded to Poop Deck:

Depth, Molded to Upper Deck:

Depth, Molded to Second Deck:

Depth, Molded to Third Deck:

Load Draft, Molded (Design):

Load Draft, Keel (Full Scanting):

Gross Tonnage:

5201-01’

4968-011

71r-6!1

54’-0!!

52]-011

43’-611

35’-011

26’-011

30’-0”

32’-9 7[8,1

10,747

-25-

TABLE7 (Continued)

Net Tonnage:

Official Number:

Block Coefficient:

Prismatic Coefficient:

Water plane Coefficient:

Midship Section Modulus(with deck straps):

B. Light Ship

Light Ship Weight:

Center of Gravity:

Light Ship Drafts:

6,657

248,740

0.654 (30! Molded Design Draft)O.61 (18’ Typical Present Operation)

O.664 (30’ Molded Design Draft)O. 628 (18’ Typical Present Operation)

0.752 3010.685 181

45,631 in.2 ft. (to top of Upper Deck)

6,746 L.T.

30.40 ft. above keel24.20 ft. aft of amidships

3’-711forward19’-9 1/2” aft11’-8 1/411mean

Dead Weight at 32t-9 7/811(Cargo Capacity): 15,348 L.T.

c. Machinery

Propulsion System: Steam Turbine with Double Reduction Geai-

Normal Maximum

H.P. Turbine, Design R. P.M. 5,358

L.P. Turbine, Design R. P.M. 4, 422

Propeller, Design R. P.M. 85 88

Propeller, Normal Operating R. P. M. 80

Shaft Horsepower, H. P. Turbine 4,500

Shaft Horsepower, L. P. Turbine 4, 500

Shaft Horsepower, Total 9, 000 9,900

First Reduction Gear, H. P. Turbine 9.096

First Reduction Gear, L. P. Turbine 7.508

Second Reduction Gear 6.93

.26-

graph) of number of occurrences in each of the sixteen levels. Inaddition, the total number of data variations analyzed, the magnitudeof largest stress variation, a calculated average stress value, andthe mean-square value of the data record are supplied. A typicalreadout is shown in Figure 15.

Following the readout cycle, the machine will proceed auto-mtt icaLly (or manually as desired) to analyze the next data interval.The specifications for the Probability Analyzer are given in Section Cof this Appendix.

The recording oscillograph accepts either the analog outputof the tape reproduce unit (thus reproducing the originally recordedinformation]or the output of the probability analyzer (the reduceddata) to produce a strip chart record.

B. Techniques of Data Reduction

The steps in the reduction of data are presented in Figure 16.

The tapes from the ship are played back at 200 tf.mesoriginal speeddirectly onto the recording oscillograph running at slow speed. Thisproduces a greatly compressed record with the record intervalsseparated by the calibration signals (Figure 16 - 1). From this

“quick-look”, the entire voyage may be assessed as to quality ofrecorded data and intervals of especial interest may be determined.In addition, the quick-look is correlated with the log book entriesand the corresponding log book interval numbers are marked directly

on the oscillogrem. The taped data are then played through theprobability analyzer. The probability analyzer output is recordedas shown in Figure 16-2. A typical intexval of probability analyzeroutput is shown in Figure 15. Each interval, consisting of a sequence

of pulses, is then marked with a sequential “record interval” number.The pulses corresponding to Greatest Peak-to-Peak Stress, Total Number

Of Stress Variations, and the Mean Square value ( 4X ‘i) for eachinterval are read off in terms of machine counts and entered on thework sheet (see Figures 16-3 and Figure 17). The necessarymathematical calculations are performed to transfer the machine countsinto naximum peak-to-peak stress (xJ in RPSI and mean square stress

(E) in KPSI 2. These values are the” recorded on the work sheet (seeFigure 16-4 and Figure 17). Log book intervals (Index Numbers) arecorrelated with machine intervals (Record Interval) and these areentered along with the pertinent data log book entries to completethe work sheet.

The completed work sheets represent a compilation of thereduced data for each voyage. The work sheets, magnetic &ta tapes,and data log books for each voyage are retained on file by the Investi-gators, and can be made available to interested parties o“ request totbe Investigators or to the Secretary, Ship Structure Ccxmnittee,U. S.Coast Guard Headquarters, Washington 25, D. C.

c. Probability Analyzer: f40delPA 102

Manufacturer: Sierra Reseazch CorporationPost Office Box 22Buffalo 25, New York

-27-

SDecificatiOns

GENERAL

Input Voltage

Input Impedance

FILTER 3 Selectable Filterswith a mid-band gainof 5.

Output Voltage

Output Current

Frequency Range

PEAK-ENCODER

Input

Output

h.v. d.c.

21,000 Oturls

High pass of about 1 cps com-bined with low pass of about66 Cps.High pass of about .5 cps com-bined with low Dass of about33 Cps.High pass of about .25 cps com-bined with low pass of about17 Cps.High pass filter is first-ordertype; Low pass filter is secondorder, approximately 0.6 criti-cally damped.

O to 10v. d.c. to pen recorder

10 ma. maximum

o to 100 Cps

~5v. into 5,000 ohm Load

7-bit binary number for c to Peak7-bit binary number for O to Trough

These two encoders determine and store inbinary form the greatest positive valbe,occurring between successive positive-going zero crossings and the most negativevalue, occurring between successivenegative-going zero crossings.

Accuracy ~1 count, ~ 1%

Response O to maxfmum in less than.0026 seconds

PEAK TO PSAK DETECTOR

The sum of counts corresponding to the readingsin the positive and negative peak-encoders areread out into the level occurrence counters atsuccessive positive-going andlor negative-going

zero crossings. This is an 8-bit binary number.

-28-

ZERO CROSSING DETECTOR

Positive and negative-going zero crossings areextracted, and are used to operate the readoutinto the level occurrence counters and to resetthe encoders.

LEVEL-OCCURRENCECOUNTERS

Number of Counters 16

Maxfmum Count 255 (8-bits)

Digital to Analog Conversion IOV. full scale, k 1% accuracy

The 16 counters will register a count when theencoded peak-ro-peak values are: 1 to 11, 12to 23, 24 to 35, 36 to 47, 48 to 59, 60 to 71,72 to 83, 84 to 95, 96 to 107, 108 to 119, 120to 131, 132 to 143, 144 to 155, 156 to 167,168 to 179, and 180 to 255 respectively.

CO~ROLS

Mode Switch Peak-to-PeakPositive PeakNegative Peak (Trough)Positive and Negative Peak

Readout Gain

Counter Readout 10v. = full scale = 32, 64, 128, 256,512, 1024, 2048, or 4096 counts

Auxiliary Readout lfhr.= full scale = 128, 256, 512,1024, 2048, or 4096 counts

Stop Mode Overload of any level-occurrence counteror one of the following: External com-mand, predetermined ttie, predeterminednumber of cycles.

Readout Form

Analysis Duration

AuxILIARY COf-fPUTATION

Moments

Between thresholds, below thresholds.

2, 4, 6, 8, 12, 16, 24, 32, 48, 64,96 seconds (derived from 60 CPS line. )50, 100, 150, 200, 300, 400, 600, 800,1200, 1600, 24oO counts into leveloccurrence counter.

VO1 tages proportional to total numberof counts and first and second momentsare recorded. lov. = 128, 256, 512,1024, 2048, 4096 counts.

-29-

Greatest Peak-to-Peak value Encodes and stores the greatest Peak-to-Peak value during a given analysiscycle.

ADXILIARY CONTROLS

Relay Relay Closure to Turn Tape Recorderoff and Paper Recorder on at end of

analYsis cycle. Turn Paper Recorderoff and tape recorder on after readoutis completed.

Delay

DESIGN

Approximate Size

Approximate Weight

Temperature Range

Fewer Required

Incorporate selectable delay of 1, 2, 4seconds k 207.after start of tape recorderand before start of analysis cycle.

100 pounds

50% to 100°F

Approximately 70 watts, 115v ~ lm. 60 CPS.

Panel mounted for inst.allation in standardrelay rack.

SHIP HULL RESEARCH COMMITTEE

Division of Engineering & Industrial ResearchNational Academy of Sciences-National Research Council

Chairman:

RADM A. G. Mwnma, USN (Ret. )Vice PresidentVI orthington C orporat ion

Members:

Mr. Hollinshead de LuteAssistant to Vice PresidentBethlehem Steel Co. , Shipbuilding Div.

Professor J. Harvey EvansProfessor of Naval ArchitectureMassachusetts Institute of Technology

Mr. M. G. ForrestVice President - Naval ArchitectureGibbs & Cox, Inc.

Mr. James GoodrichGeneral ManagerTodd Shipyards, Los Angeles Div.

Professor N. J. HoffHead, Dept. of Aeronautics & AstronauticsStanford University

Mr. M. W. LightnerVice Prw sident, Applied Re searchU. S. Steel Corporation

Arthur R. LytleDirector

R. W. RumkeExecutive Secretary