Analysis and storing of ship propulsion data

FRAN

STATENS SKEPPSPROVNINGSANSTALT

(PUBLICATIONS OF THE SWEDISH STATE SHIPBUILDING EXPERIMENTAL TANK)

Nr 73 GÖTEBORG _f974

ANALYSIS AND STORING

OF SHIP PROPULSION DATA

BY

AKE WILLIAMS

Paper presented at the

TFIP-IFAC-JSNA Joint Conference on Computer Application in the Automation of Shipyard Operation and Ship Design,

Tokyo, August 1973

Distributed by:

Liber Distribution P.O. Box

S-162 10 VÄLLINGBY Sweden

PRINTED IN SWEDEN DY

One irportant research activity in the field of merchant ship propulsion is to find functions between hull form and propulsive quality. The present

paper deals, firstly,

with the problem how to establish significant

coefficients and parameters for hull form and propulsive quality and,

secondly. how to analyse and prepare these data so that accessible

information can be gained.

For the description of the hull form, draft functions of the waterline geometrical parameters (area and boundary conditions) are used. The propulsive quality of an actual hull form is expressed by the relation between required engine SHP for the actual ship and a corresponding

standard ship meeting the same practical demands.

All prepared hull form and propulsive data are transferred to a

computer data bank giving possibilities to predict propulsive qualities of

arbitrary ship projects as well as indications of optimum hull form for

given ship and engine particulars (within the limits set by the amount and

4

2. Introduction

Over the years a large amount of ship propulsion data has been collected,

mainly by towing tanks and ship research institutes. This material,

representing a great deal of work and money, ought to be so penetrated that present and future ship projects can take advantage of the experiences concealed therein.

Systematical data prepared by towing tanks often appear as design handbooks for approximate calculation of required engine SHP and

propeller particulars [II. 'In connection with hull form and propulsion it is

common that also economical paraments are treated [2].

When analytically handling only part of the ship's total performance

there is a risk for sub-optimization which must be avoided. Procedures for integrated ship design. often created by shipowners' technical staff [3], consider every kind of technical, economical and market parameter, thus

making a total optimization of the project possible. However, a most evident risk is here that a small, incidental mistake in, for instance, a

market parameter cannot be balanced by a great effort in estimating, for

instance, a technical parameter.

Why analyse and store ship propulsive data? - Like all general

technical and economical investigations the result of a ship propulsion examination must be analysed and questions as: Is the attained result

favourable! Could it be better? How could it be better? must be answered. Are the conditions at hand which can give the ship a good performance? If the conditions are changed slightly, what will the outcome be regarding

propulsion? This is a part of the optimization of the whole ship, a

characteristic of which is the required freight rate (RFR) for a standard economical return.

Regarding cargo capacity and installed engine power, merchant ships embrace very large intervals compared with other commercial vehicles,

landbased and aerial, Fig 1.

Also the relations between the main

dimensions, propulsion alternatives, etc can be selected more

inrestrictedly than, for instance, for a truck or an air freighter. This does not facilitate the characterization of a ship. The need for consistent and non-dimensional parameters is evident.

L'd;,::C1iT Tous lo 1,ediun-ized Carao Shio

w

Lr Tankers arid Bulk Oarrcrs N ontainer-and ro-ro ships Coastal and Continental Ships EICISE SHP

6

3. The procedure in general for analysis and storing of ship hull form and propulsion data

The way to make the

raw material", mentioned above, useful for

subsequent investigations can be described by four stages of activity; (1) collection of available significant data for hull form and propulsion, (2)

analysis and reduction to suitable numerical form, (3) storing of the

prepared data in a computer data bank and (4) programming the

procedures by which information is transmitted from the data bank to general statistical calculations, ship

initial design and judgment of

domestic and foreign ships projects. Fig 2.

In the first instance the analysis has to be carried out with regard to

speed and power versus hull and propeller particulars. This dependence is considered as most important. Each figure for required engine SHP of the

ship in question is compared with that of a corresponding ship with

standard hull form and standard propeller design interpolated from

systematical series. Also registered steering, cavitation and vibration

properties. seakindliness, etc may be related to standard and then

transferred to the data bank. However, it is difficult to give simple and

significant figures for these last-mentioned characteristics.

Each propulsion test series (at SSPA about 5 000 for ordinary merchant ships, 900 of which for large tankers and bulk carriers) will form a set of

numerical data to

be entered

in

the data bank. The main files

are:Identification. hull and propeller geometrical particulars, special hull characteristics, special propulsion and test arrangements, analysis results

and special notes regarding propulsive performance. The data may be

stored on punched cards, magnetic tape or otherwise in the outer memory

of a computer.

The output data may be presented type-written or on a data screen. The last-mentioned manner is useful for a rapid scanning of a narrow sector in the data bank. Some of the information may be codified in order not to

Collection of data.

Selection of

signifi-cant data for hull form and propulsion

Analysis of data. Reduction of hull form and propulsion data to suitable form for storing

Storing of data

Data Ban2a

Hull form roist-r hull geometrical da-ta including pro-peller, special hull characteristics and propulsion arrange-ments. Arbitrary and standard

Pronulsion registr

Ship propulsive da-ta including

re-sults of special investigations re-garding cavitation, seakindliness, etc.

Arbitrary and stan-dard

Transmission of in-formation.

From data bank to

statistical

calcula-tions, ship initial design, etc

Fig 2. Main block diagram for analysis and storing of ship hull form and propulsion data.

4. Collection of suitable data

A careful selection of significant data to be analysed and stored is most

important. Much of the material to be treated comes from foreign

investigations, the results of whic1i may be interesting but are usually presented in an unfamiliar way, Fig 3.

It is essential to point out that the present account deals with the

propulsion economy and performance of the hull form. In order to treat

this problem properly, factors influencing the transport capacity and service economy must also be included in the analysis.

8

Donestic ships aad ship pro-jects. Full data

Selection of signifi-cant ororulsion data

Selection of signifi-cant hull form data

To analysis

Fig 3. Collection of data.

In connection with the collection of data some information which

cannot be directly expressed numerically is to be classified according to a code dictionary. This is due to information regarding customer, ship type, special hull form and investigations. The dictionary embraces about 500

code numbers systematically arranged. An example of part of a

sub-section in the dictionary is discussed in Chapter 6.1.

5. Analysis of data and conversion to numerical form

5.1 Analysis of propulsion data

A general method to characterize a ship's propulsive properties. approved by everybody, does not exist. A number of procedures can be mentioned using different parameters as a basis for the judgment. As indicated in the previous chapter the analysis is carried out for the hull form itself without

any considerations regarding the choice of hull main dimensions, hull

fullness, engine SHP and propeller RPM. In special cases. however, also an opinion regarding the selected main dimensions and fullness is asked for. In such situations it is necessary to distinguish between judgment due

to (I) hull form only and (2) hull main dimensions and fullness only.

The extent of installed engine SHP for normal merchant ships is very

large, Fig 4. Engine SHP can therefore not be used as a basis for

comparison and judgment. Even if two ships are of about the same size and speed the ship with higher required SHP need not be less favourable.

Foreif!n ships and Ship projects.

Arbitrary data

Check of reliabi-lity.

SlIP va

(]

stand

0.01 0.1 10 100

Fig 4. Extent of various capacity and propulsive parameters.

The specific engine power is usually defined as engine

SHP/displacement speed. This figure is more suitable for judgment as it is non-dimensional (in a free sense) and can thus be applied to ships with different size and speed. The engine SHP is here related to the transport capacity (including the ship itself). However, the extent of the coefficient

is rather large and, further, a low figure does not necessarily indicate a

favourable ship.

As a measure of a ship's propulsive quality the Admiralty Constant has

been used for a longtime. It is defined as 427.1 . engine SHP/displacement

2/3 speed 3, The expression is non-dimensional if water density is also included, which is. however, not the case. For the ship hydrodynamicist the Admiralty Constant means the same as the specific engine SHP for the transport technician; an appropriate manner to reduce the required engine

power to a characteristic figure for the ship's propulsion.By use of the

Admiralty Constant the hull form itself cannot be judged; the constant is

influenced also by a number of other factors, for instance,

hull

dimensions, propeller RPM and Froude's number. Thus, a low Admiralty Constant may indicate a good hull form but means, just as often, that the hull dimensions and fullness are chosen favourably for the propulsion (but possibly uneconomically for the building) of the ship.

Judgment versus standard ship is the procedure used by SSPA for

analysing arbitrary hull forms regarding propulsion, Fig 5. The

characteristic figure "SHAFT HP VS STANDARD", which is to be found in the register, is the relation between the propeller SHP for the

actual ship and the standard ship respectively. The standard ship (or the

comparison ship) is a hull form interpolated (or possibly extrapolated)

from a systematical series af standard hull forms. The comparison ship is

to have the same main dimensions and fullness as the actual ship to be

r Deadweight capacity

r Engine SlIP

Adm cons t

lo

judged. The screw propeller is not included in the judgment and therefore, at the calculation of the propulsion of the standard ship, this is fitted with a screw propeller similar to the actual one and running with the same RPM.

Standard ship

series Standard

pro-peller series

Collected propulsion and hull form data

Resistance analysis

Propulsion analysis

HHull form_analysis

F- I-To data bank

Fig 5. Analysis of data.

Table I. Computer output of standard propulsive data. Data in frames refer to ALT

V-SHAPE AFT.

SSPA STANDARD PROPULSIVE DATA FILE: 1395

PROGRAM SHIPYARD: S102 SHIP MOD: 1165F

730321 HULL NO: ALT V-SHAPE AFT

LENGTH PP M 237.0 PROP SERIES SSPA

BREADTH M 3L.86 NO OF PROP i

DRAFT FORE M 12.91 NO OF SLADES

DRAFT AFT M 12.91 BLADE AREA RAT .60

LENGTH ML M 2LO.1 PROP RPM 10.0

DISPL M3 85330 PROP DIAM: OPT FREE RUNN-5

BLOCK COEFF .8000 CORR FOR TRIALS: SSPA STANDARD

SHIP EFF PROP PROP THRUST MEAN PROP- RELA- QUASI TRIAL

SPEED HP DIAM PITCH DEDUCT WAKE ELLER TIVE PROP SMP

KNOTS (METR) M RATIO FACTOR FACTOR EFFIC EFFIC EFFIC (MEIR)

1.0 8382 6.1e57 .703 .188 .5i L73 1.010 .706 10087

15.0 10369 6.69k .715 .189 .IE8 .85 1.010 .719 12261

16.0 12793 6.950 .72k .190 .444 .494 1.010 .727 14955

17.0 15951 7.240 .733 .192 .440 .502 1.010 .732 18513

18.0 20106 7.570 .739 .193 .436 .508 1.010 .734 23273

The extent of SHAFT HP VS STANDARD is very small compared with

earlier mentioned propulsive parameters. Fig 4. The figure

is also significant for hull form goodness with regard to propulsion. Table I shows the propulsive data for tanker with V-shaped afterbody.

The figures for V-SHAPE AFT are written manually on a computer

output sheet on which are printed standard propulsive data. The

propulsive quality of this alternative of afterbody is evidently better than

the normal standard as the SHAFT HP VS STANDARD is

17 450

HP/18 513 HP = 0.943.

5.2 Analysis of hull form data

Analysing the hull form means, in the first instance, to get a numerical

description. Many attempts have been made to systematize ship hull

forms. Guldhammer has made extensive graphical presentations in this respect [4]. Others have reanlysed existing systematical data [5] as well as non-systematical material [6]. Kuiper [7] has further developed the use of draft functions for defining the hull form based on principles indicated by

the present author [8].

The differences between a considered hull form and its corresponding

standard cannot be directly expressed numerically. The afterbody of the ship, the propulsive properties of which have been accounted for in Table

1, is shown graphically in Fig 6 together with the corresponding standard hull form.

A "reduction" to draft functions, defining the hull form sufficiently, will facilitate the numerical description, Fig 7. In this case the draft

functions are limited to the waterline fullness and angle at stern frame,

faired in the vertical direction. The differences between the functions

(actual versus standard) at certain drafts can be expressed numerically and

thus make the input to the hull form register of the data bank. 6. Storing of data in the data bank

6. I Data input to the ship propulsion register

As mentioned earlier numerical as well as non-numerical information is to to forwarded to the data bank. A general rule is that the information must be as condensed as possible and that each figure entered is fully significant

for the property it is used to desribe.

For the identification of customer and ship type and also for the

classification of special hull form (of interest in the propulsion register).

12

C W L

-1/2 0 1/2

Fig 6. Stern contour and sections. Dotted lines indicate standard sections. Stern contour same for actual and standard hull forms.

CWL

Fig 7. Draft functions in afterbody. Dotted lines indicate standard hull form. I .5 CWL 1 (dy/dx) n

I

/1/

₁

/1

¡I

/

/

/

.25 CVL / /

I

J f AW .LPP/2 .125 CVI /

I,

_/

/

I

,

I I .5 .6 .7 AW _.9 BLPP/ 0 .2 .4 dy/dx .8

Table 3. Example of basic data input to the ship propulsion register of the data bank, O indicates nothing to note.

SSPA SHIP PROPULSION REGISTER BASIC DATA INPUT TO REGISTER

SSPA FILE 1305

CUSTOMER CODE S102

SHIP TYPE CODE 300

SHIP MODEL NO 1165F LENGTH LPP H 237.0 DISPLACEMENT MS 85330 BLOCK (OEFFICIENT _.8000 LENGTH/DISPL 1/3 5.5L BREADTH/DRAFT 2.700

SPECIAL HULL FORM <3 CODES 122

NO OF PROPELLERS

1-SPECIAL PROPELLER ARR <2 CODES O

SPECIAL INVESTIGATION <3 CODES 150

SHIP SPEED KNOTS _17.00

RESISTANCE VS STANDARD _.9250

SHAFT HP VS STANDARD _.91430

STANDARD SHIP SERIES CODE Ti

propeller arrangement and special investigations, a code dictionary has been set up. Some 500 different codes can be used for the expression of

data which is not alphanumerical from the beginning. Table 2 is an example

of a minor sub-section in the dictionary.

The investigated tanker with V-shaped afterbody. Fig 5 and Table 1, will be identified by a set of data like Table 3. The hull form cannot be considered as special except for a larger stem radius than normal. which is therefore noted as code 122 after SPECIAL HULL FORM. The ship has normal single propeller propulsion, thus O after SPECIAL PROPELLER

ARR (nothing to note). The code TI after STANDARD SHIP SERIES

indicates one of the systematical tanker hull form series at SS PA, from

which the comparison ship has been interpolated.

Table 2. Codified classification of special forebody form.

SPECIAL FOREBODY FORM 100

BULBOUS BOW 110

RAM 80W 111

HORISONTAL CYLINDRICAL BOW 112

BOW WITHOUT RAM 113

VERTICAL CYLINDRICAL BOW 120

LARGE RADIUS R > 0.3 8/2 121

SMALL RADIUS R < 0.1 B/2 122

ICEBREAKING STEM 1l0

BIG FLARE 160

FOR RAIL CRANE 161

EXTREME SECTIONS 170

V-FORM 171

14

6.2 Data input to the hull form register

The ship propulsion register described above is often used at a primary stage of an investigation to find interesting ships for propulsion studies and for comparison (see Appendix B). The hullform register is normally used at a secondary stage. What are the hull forms of those ships which have been selected for further studies? What are the significant differences in

hull form parameters which possibly can explain the deviations in

propulsion performance?

Table 4. Example of basic data input to the ship hull forni register of the data bank.

SSPA SHIP HULL FORM REGISTER BASIC DATA INPUT TO REGISTER

The input data, some of it codified, have about the same appearance as the input data to the propulsion register, Table 4. Most of the data are the

values of the draft functions at certain drafts also used for the further regression analysis, see Appendix C. Figures in parenthesis are draft function values in relation to standard. In this case the actual forebody form is identical with that of standard tanker series TI.

7. Transmission of information from the data bank

A large variety of information can be requested from the data bank. Some examples can be mentioned:

L Data for ship initial design, see Appendix A. Comparative judgment of ships, see Appendix B.

Statistical analysis of resistance data, see Appendix C.

SSPA FILE SHIP MODEL

1395

1165F

PART OF SHIP FOREBODY

AWF/B LPP/2 AT CML (VS STAND) .861 (1.000) AWF/B LPP/2 AT .5 CWL (VS STAND) .853 (1.000) AWF/B LPP/2 AT .25 CML (VS STAND) .828 (1.000) AWF/B LPP12 AT .125 CWL (VS STAND) .790 (1.000) (DY/DX)F AT CML (VS STAND) -.699 (1.000) (DY/DX)F AT .5 CWL (VS STAND) -.6614 (1.000) (DY/DX)F AT .25 CML (VS STAND) -.580 (1.000) (DY/DX)F AT .125 CML (VS STAND) -.1468 (1.000)

PAR 'W SHIP AFTERBODY

AWA/D LPP/2 AT CML (VS STAND) .912 (1.015)

AWA/R LPP/2 AT .5 CML (VS STAND) .788 (1.018)

AMA/B LPP/2 AT .25 CML (VS STAND) .720 t .960)

AMA/B LPP/2 AT .125 CML (VS STAND) .665 ( .966)

(DY/DX)A AT CWL (VS STAND) .622 (1.01e6)

(DY/Dx)A AT .5 CML (VS STAND) .337 ( .768)

(DY/Dx)A AT .25 CML (VS STANO) .263 ( .732)

(OY/DX)A AT .125 CML (VS STAND) .250 ( .805)

Data for ship

initial desiçn.

Propulsion and hull form data

for adjoining

standard and

arbitrary ships

Data for statis-tical calcula-tions. Propulsion

and hull form

data for arbi-trary ships Output program. Search of deman-ded information within specified intervals or restrictions

-Data for compa-rison and .lud-ment. Standard propulsion or/and hull form data

Fig 8. Transmission of data from the data bank.

8. Conclusions

The present account has given points of view upon the creation of a data bank for the collection of available ship propulsion and hull form data, systematical as well as arbitrary. The maintenance of the data bank is a continuous process. It is essential to widen also the standard material and make it more adaptable and homogeneous.

Data properly transmitted from the data bank and arranged in a

consistent way by the output program make it possible to predict

propulsion qualities of arbitrary ship projects. The reliability of the

prediction is, however, limited by the amount and quality of the stored data. In any case, a ship project can start on a higher quality level than

otherwise possible.

Much data of a small number of ships may be requested as well as little

data for a large number of ships. The searching process of the output program must therefore be flexible. The output program picks out the demanded information from the data bank according to a specification given to the program, Fig 8.

To and from data bank

Specification of demanded data

16

The ship propulsion register of the data bank seems to work well and has

proved to be extremely useful for judging model test results at SSPA. The

data bank has also provided the ship project section of SSPA with

appropriate first information of suitable hull forms. Another important

application is the possibility to get consequtive series of propulsion data

for sensitive analysis of, for example. hull main dimensions.

The hull form register has not been finally established. A number of

alternatives have been studied, the task is hard. The selection of hull form data according to Table 4 has been chosen for the further work but the set

of data does not embrace all parameters for a complete analyticai

description. As hull form identification in connection with statistical

analysis of propulsive data the present set of parameters seems. however,

to be sufficient.

9. Acknowledgement

The author wishes to thank Dr Hans Edstrand, Director of the Tank, for having been given the opportunity to carry out this work. Thanks are also due to Mr J Olofson, Mr H Olofsson. Mr R Râwall and Mr K Svensson for their valuable assistance.

References

Williams A: SSPA Cargo Liner Series. Resistance. Propulsion. SSPA publications 66 and 67, 1969 and 1970

Holtrop J: Computer Programs for the Design and Analysis of General Cargo Ships. Report No 157 Netherlands Ship Research Centre TNO. Deift

Ekholm S. Ahlqvist T: Technical - Economical Ship Design by Use of Computer,

NSTM Copenhagen 1969 (in Swedish)

GuldhammerHE: Formdata (and followingcomplementary volumes). Danish Technical Press, Copenhagen 1962

Sabit S A: A Tabulated Analytical Procedure Based on Regression Analysis for the Determination of the Form Coefficients and EHP for Ships Designed According to Series 60. European Shipbuilding No 2 1971

van Oortmerssen G: A Power Prediction Method and its Application to Small Ships. ISP Vol 18, November 1971

Kuiper G: Preliminary Design of Ship Lines by Mathematical Methods. Journal of Ship Research. March 1970

Williams A: Mathematical Representation of Ordinary Ship Forms. SSPA publication No 55. Schiff und Hafen. May 1964

Rwall R: Statistical Analysis of Resistance Data for Ship Body Forms Represented By Draft Functions. SSPA publication in preparation (1974).

18

Appendix. The development of a data bank at SSPA and some examples of its use

Most of the ship propulsion register is completed. Efforts have been made to finish special sections of the data bank, which are of immediate interest. The register of large tankers and bulk-carriers is thus complete and has

been in use for some time. Another section under development is fast

reefer, container and ro-ro ships. Each of these special registers comprises

about 1/10 of the total amount of propulsion data.

The hull form regi ster has not yet been given its final form and relatively

little data has been collected and analysed up to now. Below are mentioned

some examples of use of the data bank and its state at present. Appendix A. Data for ship initial design

In connection with the initial design of a large single-screw bulk-carrier,

about 270 m in length. it is interesting to know if there are any hull forms in

this class which are better than standard regarding propulsion. Therefore

SHAFT HP VS STANDARD is set less than I in the specification of

demanded data from the register. Table 5.

It

is also in this case

presupposed that the hull

is

to have a moderate block coefficient

Table 5. Example of input to register for demanded data. 00 indicates no information needed.

01 indicates demanded information without specified restrictions.

SSPA SHIP PROPULSION REGISTER

SPECIFICATION OF DEMANDED DATA FROM REGISTER

SSPA FILE INTERVAL 11400-1699

CUSTOMER CODE 00

SHIP TYPE CODE 300

SHIP MODEL ND INTERVAL 00

LENGTH IPP M INTERVAL 2140-300

DISPLACEMENT M3 INTERVAL 01

BLOCK COEFFICIENT INTERVAL .80-.82

LENGTH/DISPL 1/3 INTERVAL 5.0-5.14

BREADTH/DRAFT INTERVAL 2.14-3.0

SPECIAL HULL FORM <3 CODES 110 120

NO OF PROPELLERS INTERVAL 1

SPECIAL PROPELLER ARR <2 CODES 00

SPECIAL INVESTIGATION <3 CODES 00

SHIP SPEED KNOTS INTERVAL 00

RESISTANCE VS STANDARD INTERVAL 01

SHAFT HP VS STANDARD INTERVAL .5-1.0

SHAFT HP VS STANDARD .8600 .9200 .8230

STANDARD SHIP SERIES Ti Ti Ti

Appendix B. Comparative judgment of two reefer ships

Two fast reefer ships A and B are to be judged regarding hull form

propulsive qualities and also compared with each other from that respect. Ship A is from the middle fifties, ship B was built during the late sixties. There are some differences regarding main dimensions and hull fullness.

The difference in hull form is significant.

A comparison based on specific engine power, Fig 9. gives misleading

information as expected, because this figure has no hydrodynamical background. It is, however, interesting to note that ship B, for a certain

transport work, consumes about 50% more fuel than A.

The Admiralty Constant, Fig 10, gives a relatively good idea in thiscase

(0.80-0.82) but a rather small length/displ 1/3 (5.0-5.4) due to length

restrictions. All kinds of bulbous bows and vertical cylindrical bows will be considered, therefore codes 110 and 120 after SPEC IAL HULL FORM

in

the input data. Ballast load cases are not requested, therefore

breadth/draft interval is not set higher than 3.0.

The output sheet from the computer appears as Table 6. There is

evidently 8 test series that meet the demands specified in Table 5. In this

case customer, ship model, special propeller arrangement are of no

importance and have therefore not been printed.

Table 6. Example of computer output from the data bank. Demanded data as per Table 5.

SSPA SHIP PROPULSION REGISTER DATA OUTPUT FROM REGISTER

SSPA FILE 11435 11435 11435 15141 1560 SHIP TYPE 310 310 310 310 300 LENGTH IPP M 252.0 252.0 252.0 266.7 2146.0 DISPLACEMENT 113 107700 107600 1071400 11414500 108300 BLOCK COEFFICIENT .8200 .8190 .8180 .8230 .8230 LENGTH/DISPL 1/3 5.3814 5.386 5.390 5.217 5.225 BREADTH/DRAFT 2.920 2.920 2.920 2.668 2.989

SPECIAL HULL FORM 111 111 111 110 120

NO OF PROPELLERS 1 1 1 1

SHAFT HP VS STANDARD .9500 .9300 1.000 .9620 .91400

STANDARD SHIP SERIES Ti Ti Ti Ti Ti

SSPA FILE 1576 1681 1681 SHIP TYPE 310 300 300 LENGTH LPP M 2146.9 24.8 243.8 DISPLACEMENT M3 118200 115130 1114960 BLOCK COEFFICIENT .8170 .8210 .8200 LENDTH/OISPL 1/3 5.146 5.122 5.125 BREADTH/DRAFT 2.867 2.7014 2.7014

SPECIAL HULL FORM 110 110 110

20

of the difference in propulsive quality as the ships are not too far from each

other regarding dimensions and size. The indicated difference of 6% is, however, not completely significant for reasons mentioned in Chapter 5.1. The engine power in relation to standard for each of the ships is shown in Fig Il. In the present study ship B is considerably better than A and also holds a good position in the accumulated material in this limited sector. A number of other fast cargo ships are indicated in the diagram. The study is a clear illustration of 15 years research work on hull lines for fast cargo liners. It should be noted, once again, that the level lin Fig Il represents the comparison (standard) ship of every analysed ship which is indicated in the diagram. 1.2 1.1 1.0 .9 I I I 20 .24 28 FROUDE NO

Fig iO. Comparison by Admiralty Constant. .36 .06 04 .02 I I SPFC. ¿iGItE PO:TR I

1/

4

B 52 I I

-% worse than A

J

/

Z

/A

B

/

18 20 KNOTS 24 Fig 9. Comparison by spec. engine power.

.8 1.2 ENGINE SHP VS STANDARD + a)

.

s

s.

1.1 -

. s a).

_,

A

1.

o.

B.16

better

s than A s 1.0 -d s o _s s _{s s} s .9 4-, a, o a) .0 a) a)

.

's

e s B 100 125 150 LENGTH LFP M 200 Fig Il. Comparison by SHP vs standard.

Appendix C. Statistical analysis of some resistance data for

medium-sized tankers and bulk-carriers

A short investigation of the applicability of the expressions for resistance

and hull form to statistical analysis has been made by SSPA (9). The

analysis has covered some 50 medium-sized tankers and bulk-carriers.

In due order, when regression analysis is

to be carried out, an

introductive partial correlation analysis

is performed regarding the

independent variables (different

hull form parameters). A test of

significance (F-test) decides if the value of the correlation coefficient

(RSQ) differs significantly from O. If it does, one of the variables

considered is dropped. Thus the program investigates stepwise every variable and approves or drops them. After each step the correlation

coefficient, standard errors and residuals can be calculated by the

computer program.

The distribution of the residuals, that is the differences between the original values of RESISTANCE VS STANDARD and those values

calculated from the regression equation, is a measure of how successful the analysis has been. It is to be noted that the number of variables in the regression equation must not exceed about 20% of all the ships included, otherwise the RSQ will be misleadingly high. It is also to be observed that the result regarding mean error and confidence is only valid for hull forms

included in the analysis. However, if these are representative for a

22

considered

class of

ships,

the confidence will not be too much

overestimated.

According to the above the present regression analysis has been

interrupted after 8 steps and the result is seen in Fig U.

By use of the regression equation the RESISTANCE VS STANDARD can be calculated with an accuracy of less than 3% at a confidence level of

80%. The form parameters included in these 8 steps and which have

proved to have the strongest correlation to the resistance are among others (DY/DX) F AT .5 CWL, AWF/B . LPP/2 AT CWL, (DYIDX) A AT .5

CWL and (DY/DX) A AT .25 CWL, see Table 4.

CONFIDENCE LEVEL % 1 00 _I I 80 60 40 20 O t I I O 2 4 )iEAN ERROR % 8

Summary 3

Introduction

The Procedure in General for Analysis and Storing

of Ship Hull Form and Propulsion Data 6

Collection of Suitable Data 7

Analysis and Conversion to Numerial Form 8

Storing of Data in the Data Bank Il

Transmission of Information from the Data Bank 14

Conclusions 15

Acknowledgement 16

References 17

Appendix. The Development of a Data Bank at SSPA