Instructions for the field use of the Pratt project hull measuring device

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Report No. 77-6

'±NSTRUCTIONS FOR TEE FIELD USE OF

THE PRATT PROJECT

HULL MEASURING DEVI

by

--- -'ii

.j

-

_ --

-Deift UniversitY of Technology

Ship BydromeChan'

LaboratOlY

Library

Mekeiweg 2. 2628 CD Deift

The Netherlands

Phone: +31 15 2786873 ax. +31 152781

-'..

Owen H.

ak].ey, Jr.*

May 1977

i

H. Irvin g Pratt

(2)

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Report No. 77-6

mSTRUCTIONS FOR T FIELD USE OF TEE PRATT PROJECT

HULL MEASURING DEVICE by

Oren H. Oakley, Jr.* May 1977

This research was carried out in part under the H. Irving Pratt Ocean Race Handicapping Project, M.I.T.

OSP No. 81535. The generous support of the ndividua1

dönors to this program is gratefully acithowledged.

*Massausetts Institute of Technology

(4)

AB STRAC T

A device far measuring and recording the offsetS ft a boat hüll

is described.. _{Instructïons for its use in conjunction with a series}

of computer programs desïgned to interpret the recod.ed _{datá äre given.}

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-1-TABLE OF CONTEN'S

iii

Pag

ABSTRACT

PRATT PROJECT REPORTS LIST - -il

TABLE OF CONTENTS

A. STJ*ARY ISTRUCTIONS i

B. DESCRIPTION AND PRINCIPLES OF OPEEATON 2

C. I&STRTJCTIONS

I. What to Measure 9

tI. Setting Up the Device 13

III. Cenerai ConsidëratiòflS 18

IV.

Tkirg

the Measurements 22

V. Last Steps 24

VI. Codes 25

Figures

-29

D. EQU CBE LIST 32

E. TROUBLE SKOOTINC 33

(6)

A

SUMMARY INSTRUCTIONS

SETTING UP THE DEVICE

1. Establish the Baseline

Select y0 (Fig. 5)

Place targets and tape measure (Fig. .4

2. Hook up and record identificationdata

Advance tape (Fast Forward)

(Fig.)

Measure R0 (Fig. 8)

Record: date, sail number, and R0.

Adjust the aligrmient meter range. (Fig.11)

3. Zero th buflters with the string in the reference position

by pushing the RESET button.

-TAKING THE MEASUREMENTS

1. Ain device With targets (preliminary) and Level case (Roll

level). (Fig's. 9 and 10)

2

Read X-distance from tape and Enter with thumb wheels. (Fig's.

Sand il).

3. Select and enter thé. CODE (Fig. 11).

-

4. Final alignment with string in tension and level check.

Record data: 3 centerline points (min.)

3 waterline " (min.)

5-25 station points (avg.) 15 stations (avg.)

After measuring the freeboard mark (Code 0040), enter the actual freeboard value, if known, in the X-wheels and "0041"

in the Code-wheels.

Check Code and X-distance, then move to next station END OF MEASUREMENTS

If the EÓT light is not on, push FAST FORWARD to "zero unused

portions of the tape; then remove the Wafer and Label it with the boat namé and data.

(7)

-1-DESCRIPTION AND PRINCIPLES OF OPERATION

This section describes the Pratt Project Ex1.l Measuring Device which

is use4 to obtain the offsets of a yacht hull. The device permits data to

be taken at arbitrary stations in polar coordinate format by extending a

string to the desired points on the hull. The offsets are recorded on

m4ni

ature cassettes by a digital tape recorder and are transmitted, with

suitable interfacing, over the phone lines to the computer for processing Additional discussions of the design philosophy and something of the

his-tory of yacht hull measurements is given in the Pratt Ocean Racing Handicap Project Report No. 76-1,. *

DESCRIPTION

Data is taken at arbitrary stät-ions in polar coordinate fôrmat by extending a string to desired points on the hull as illustrated in Figure 1 The distance along the hull is measured simply by using a metal tape

starting from some arbitrary reference point. The longitudinal distance

and a code designation are recorded by first setting two sets of thtb

wheels on the case to the appropriate values at each station. When the

string is extended to the hull and the record button pushed, all four

numbérs are recorded sequentially by a digital tape recorder. The four,

four-cháracter numbers are:

a code number indicating the boat and/or the nature of the offset being recorded;

the distance along the hull of the station being measured; an angle proportional to the string extension;

the angle made by the string and the case reference angle or horizontal.

Repeated recording of the second item is presumably redundant if many

points are taken at each station sequentially. However, for automatic

analysis of the data by a computer program or f ör.the recovery of data

after a recording error, such redundancy may be of great value. Further

details of the prototype are given in the following subsections Mechanical Syst

The. string being used -s made of Kevlar and has essentially zero stretch. It is stored on adium connected to a Neg'ator Constant tension

-2-* Oakley 0.3. Jr. & J. Arrison "Design Development of a Hull Meásuring

Device," Report 76-1, H. Irving Pratt Ocean Race Handicapping Project, January, 1975.

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Level Alignment Scope *-A4-j.

3ead/'

Power S trin a Offset Locations Display Cable

FIGURE i Section Tiew of Aaratus

spring yielding approximately a two pound pull, and virtually no catenary (cf. Fig. 3). The angle made by the string with the horizontal is sensed by a light weight arm with a small hole only slightly larger than the

string diameter. In order to avoid the use of scaffolding, the string is

connected to the end of a wand to facilitate reaching to the deck and the

hull. The wand has a Delrin tip .to reduce wear on the string and damage

to the yacht. _{The record button is located at one of the hand grips for}

ready access. _{Digital readouts of the data and an alignment meter, to be}

described below, are provided on the wand for constant monitoring by the

measurer. The instrument itself sits on a tripod with an adjustable head

having five degrees of freedom. A sighting scope, mounted on top of the

case, is used for alignment. Alignment

Two types of alignment are required. The first calls for the

instru-ment to be positioned, squared and levelled at successive stations along

a fixed line in space, called the instrument baseline. The height and angle

of the instrument are adjusted so that the attached sighting scope becomes aligned with two remote targets, one of them being a set of cross hairs. The second alignment requires the string to remain in a place perpendicular

to the longitudinal axis as illustrated in Figure 2. This is accomplished

by strain gaging the string sensing arm for longitudinal motion. The

string is first aligned in the reference notch on the case and the strain

gage bridge is zeroed. Any longitudinal motion of the string is sensed

by the strain gages and is displayed by a meter situated on the wand. The

measurer need only refer to the alignment meter while holding the string

(9)

-3-Fiure2

lnstrutneñt A1iarueñt

The data storage system is a single channel, mineature tane recorder made

--bv--Mieo C

ilcations ,-Wàltham.-- Mass Da a- is-.t-ten-onto

a miniature loop of magnetic tape, called a "Wafer", which is toughly the

same size as a book of matches and can be sent through the mail in an

ordinary envelope The recorder contains the clock that regulates the

digital circuitry The logic circuit keeps a continuous count of the

pulses emitted by the shaft encoders Counts are added as the string is

extended, and subtracted as it retracts The power must therefore be

left on during the measurements. If the power is interrupted the circuit

-4-to the hull and moving down the sta-4-tot. This procedure has proven to

be accurate and exceedingly simple to follow in practice The tripod for

the prototype is rather complex, having adjustments in five degrees of freedom. A patient measurer may be able to perform the same adjustments with a simple tripod at a considerable savings in costj, however the fine adjustment features appear to be necessary for rapid and precise alignment.

Measurement Signals

The distance to the hull is obtained by sensing the number of turns

made by the string storage drum using a shaft encoder. This is an electronic

device that outputs a series of square wave pulses, many times per

revo-lution, that are counted

_by

the digital logic circuit The angle made

_by

the string änd the case reference (or horizontal) is sensed by another en-coder. These are shoWn schematically in Figure 3. As noted earlier, the longitudinal distance obtained from the tape measure and a code number are entered

by

setting a group of thumb wheels located on the front of the

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Cônstant

Tension Spring String Arm Strain Gages String Angle

Encóder

(e)

Guide..

_String Storaàe Drum Distance Encoder (R) I f

f

FIGLIBE 3 _{Schematjc.Vjewof the Neas'j±jcD9vjce}

-5-Code

X-Dis.

DIGITAL CIRCJfl' R*CORDER

automatically rezeroes itself. It is therefore essential that the string

then be allowed to retract to the reference position on the case and the

system rezeroed Otherwise, the reference point and angle will be at an

unknown wand position. As long as the length of. the string, is not changed,

the calibrations remain fixed. The circuit continuously samples the

thumb wheel inputs, displays the current readings at the wand, and writes

them out in series on the tape when the record button is pushed Ample

power is provided by a twelve volt car battery insuring stability and ready access in remOte measuriñg locations.

Write/Read System

The prototype configuration calls for the instrt ment to contain a

write-recorder only The principal element of the digital circuitry is

the random access memory (RAM). tt stôres the current value of the

shaft encoder positions The PAM is four bits wide (every access

refer-ences four bits), and 16 words long.. Only the first eight words are. used. These eight are divided into two goups of fbur, one for the angle count,

and one for the length count Each of the words is a binary coded

deci-mal (BCD) digit This allows direct readout for the display For ease

of adding, the first digit (word zero) is the least significant digit of the first word.

At 500 z, every digit is read, incremented or decremented as

nec-essary, and written back into the RAM At

1/16 of

this speed (31 KBz)

the shaft encoders are examined to see if they have changed If they

have, an increment or decrement of the least significant digit is called

for The remaining digits are incremented or decremented depending on

the carry f-rom the previous digits.

The display works on a multiplexing scheme. Of the twelve

light-emitting-diodes (LED) segments, only one is active at a time At

ap-proximately i KHz, the digit being displayed is changed Specifically,

the digit number and value are sent serially from the main electronics

box to the display Serial transmission is used to keep the size of the

cable to a minim The display contains all of the logic necessary to

decode the BCO digit, and to drive the seven segment LED.

Thwth

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Writing to the tape recorder is initiated by presaing the record

button on the wand There are three phases of the write operation

First, the tape recorder is turned on, and a delay occurs while it comes up to speed. Second, each grOup of four words is loaded into a shift register, in reverse order of position, then sent serially to the tape

recorder. The reversa], of the digits converts the digits to logical

order, with the least significant digit last The third phase consists

of letting the motOr in the tape recorder corné to a complete stop. Th

principle, if the record button is pressea too rapidly in succession, the tape will not be read correctly as there is too short an inter-record gap. This has not proven to be a problem

in

practice.

The Wafer or tape is read by a separate read-recorder with the

inter-face circuitry for the digital computer. The real electronics are also

organized around a RAM Each data point of the tape causes the read

system to cycle through four states. First, the tape recorder is turned

on and the ready system waits for it to come to speed. The 64 bits of

data are then read, formed into four bit word (digits), and stored in the ram The third phase loads a ten bit shift register with the

e-qw.valent of the digit After the computer indicates that it is ready

to receive data, these 10 bits are shifted out at the bit rate (currently 300 Rz) This is repeated for each of the 16 characters.

After

the characters are sent,, a special character follows t indicate that the line is complete.

METROD 0F OPERATION AND ANALYSIS

The measuring procedure is as follows. After assembling the

equip-ment, the two targets are set up so that the instrument base line is approximately parallel to the centerline and the water line, but need not be precise. The device is located at the first desired Station and al-iged with thé targets with the aid of the fine adjustment screws o-n the tripod head. The station location is measured with the tape and

entered onto the thumb wheels along with the boat/station code. The

string is centered in the reference notch and the strain gage bridge and

counting circúits are zeroed. Using the wand, the string is then

ex-tended to the hull, keeping the alignment meter centered. If the measurer

is content with the displayed coordinates at

a

selected point on the

station, the record button is pushed and the data is automatically

written onto tape. Between fIve and fifteen offset points are usually

sufficient to define any station. At the completion of each station,

the tripod is moved down the hull a short distance, realigned, the new longitudinal distance and code are entered, and the process repeated. The canoe portions of most hulls rarely require more than 12-15 stat-ions

(12)

-7-adequate definition: However, as many as twenty may be necessary to

define the profile, lumps, and chines It usually requires less than a

minute to tke. the data at each statiön. Positioning and aligning the

tripod at successive stations takes more time,

but

_{the entire process}

requires less than five minutes per station

In addition to the standard offsets at each station., some additional

information will be required It is important to identify a few points

defining the waterline and the centerline These are indicated

by using a code designation for easy computer recognition This

--information is used to transform the offsets troni the arbitrary

instru-ment base line coordinate system to a standard reference system. The

first step in the data analysis is to read the offsets from the tape After scaling, the offsets are generally inspected for inconsistencies

and bad points A typical mistake is to forget to reset the

longitudin-al distance after moving to the next station. This fact is usually

noticed after the taion readings are taken and an error code, along

with the proper x-distänce can be. recorded. The data must then be

cor-rected 4uring the computer processing.

Sincé the instrument coordinate system 'is centered some distance away from the centerline plane, it is convenient to translate and rotate

the offsets to a more' usefül örigiu A convenient scheme is to assume,

unless otherwise indicated by the code ni.ber, that the first point on

every station is on the centerline A least-squares fit can then be

used to shif t the offset 'to the revised, centerline Obviously only three points, as a minimum, are requrred to define the centerline plane, but multipole readings and the least-squares fit reduce the importance

of any one centerline measurement Figure 4 is a straight line plot of

the data points, shown by triangles, taken off a thirty-four foot yacht

in under two hours. The missing 'points were caused by cover and support

interferences and the data was tàken at unequal station spacings. While

it does not appear that any smoothing of the raw data would be required,

spline fit routines are available. The visual inspection of a body plan

is probably t-he fastest and mst reliable type of checking procedure.

This also means that a hard copy of the body plan. is generated With

experience, most of the analysis process can probably be automated

ACOWLEDGNTS

The design and cnstuction was aided by the asSistance of J. Arrison

(13)

Figure 4.,Straight Line.Plo ofRtated, Raw Data

(14)

-8-C.

INSTRUCTIONS

I..

WHAT TO MEASURE

Number of Points and Stations

There is no need to take any more data than necessary. HOwever, how

much is necessary depends on the use that will be made of it Until specific

requirements are determined, the following guidelines are offered:

1) Measure the boat at enouqh statiOns to adequately define the

profile and any special 1umps,bumps, etc A rectangular

barge would need only two stations. A normal, separated

keel/rudder hull probably requires 12 to 15 stationS A

complicated hull may require as many as 20 stations Suggested station locations are indicated below

-'9.!

An additional station between 4 and 5 wOuld improve the keel

definition. These locations can be adjusted to coincide

with special freeboard measurement points or additional

stations can be obtained. (See Speia.i Pointsu below.)

) The number of points per station will depend on the station

shape Five to fifteen points per station are usually

sufficient. The spacing of the points shquid follow the

philosophy of a straight line approximation Points

should be placed close together in regions with a large amount of curvature and farther apart in flat sections.

This is il1u5tted in Figure 1 of Section B..

The computer analysis progÑms are currently designed

for a maximum of 25 points/station If this number is

exceeded., the fact. should be included with the tape when it is sent in for analysis.

(15)

-lo-Special Points

The computation of displacement and other rating rule ingredients froth the offsets demands that the yacht be trimed to her proper lines of floatatióñ. This is accbmplished by rotating the ineísured offsets to the desired trim on the basis of the location of certain points. Special points that are useful to flag (using the code numbers discussed below) are centerline, watérline, and freeboard points.

1). Centerline_Points: If only one side of the yacht is to be measured, the centerline of the hull must be determined Despite the best intentions of the designers and builders, most yachts are probably somewhat asynu tri c. Keels,

rudders, and mold lines are nöt likely to be particularly accurate indicators of the centerline In order to determine an approximate location of the center plane, the best fit to selected centerline paints is computed. Uséful points for establishing an approximate centerline are typically available on the stan and just fOrward or aft of the skeg/rudder Keels, skegs, and rudders should

be avoided A minimum of three good centerline estimates

should be taken, preferably more, and they should contain as great a vertical spread as possible. Unless otherwise noted, the.first point on each station is assumed to be a centerline point. It is usually not even possible to reach the centerline under the keel and in-way-of cradle

suppOrts. These statiQns are flagged accodinly.

ReferenceCentèr1iñe Points: If both sides of the hull are

tó be mMsured, thé bides will be joined by matching

threé or more "reference centerline points" that are connon to both sets of Öffsèts. They will normally be on the centerline, though possibly on the keel, and therefore the first point on a station (See the discussion of

Section III.)

Waterline Points: During the measurement of the boat, the trUe waterline is not known. Thé bottom of the

boot top, however, can be usefúl forpreliminary analyses. It is reconanended that the boot t6p be includéd as a

regular point on all stations, but flagged only twice, once near the bow and once near the stern.

(16)

Freeboard Points: The actual trim of the yacht cannot

be determined until it is afloat Freeboard measurements

need to be taken from specific points. The actual trim

of the measured offsets can then be detErmined and the

desired calculations made Two approaches are possible

select and mark new freeboard measurement points OR use

existing

(laR?)

freeboard measurement points.

The first case is the easiest for the measurer. When a

station is measured in the desired neighborhood of the freeboard mark, the final point recorded can establish the freeboard point. A pin or other appropriate mark should be put in the toe rail and the freeboard measured from this point when the boat is afloat.

The second dase requires that the IOR freebòard mark or

pin in the toe rail be measured accurately This suggests

that the instrument be positioned iteratively until the point on the rail is indeed aligned before the data can

be recorded However, repositioning the device two or

three times in order to achieve an accurate alignment with the targets and the pin is time consuming and nOt worth the effort if the toe rafl is relatively straight.. The analysis programs can easily interpolate beiween

Stations if they are relatively clOse to the IOR mark

in question. Note that this method requires the measurer to détermine the origin of the IOR longitudinal coOrdinate

axis relative to the X-axis of the HMD. The IOR defined

bow location measured as a station would supply the necessary data for positioning the freeboard point.

No boat between., points: If a station l's taken that

inter-sects the trailing edge of the keel (cf station 7, p 9)

or is in way of the propeller aperture, there may be no

boat between successive station points. In order tO

indicate this fact without having to return to the case and change thé code, puh the wand well beyond the centerline and record a clearly erroneous nuffiber. Once the data has been scaled, this point will have a large negative y value

and can be easily identified For automatic recognition,

be sure that the fake point is at least six inches beyond the centerline.

(17)

GREATER THAN 6 INCHES.

5) Bowañd Stern Points: The bow and stern locations may be

reqiédtbbèlate previous data, stich as

IORfreé-boards, with the urrent measurements They should be

obtained as the first and last station for completeness

in any event Since aligning the MMD to a precise location

may require an excessive number of iterations, an

approxi-mate procedure may be used An attempt should be made to

position the HMD as close longitudinally as possible to

the bow (stern) point The longitudinal discrepancy

between the device and the point in question should then

be noted If the station falls beyond the end of the

boat, shifting and realigning the device can be avoided by correcting the X-distancé, holding the tip of the wand to the correct height and length (though at the wrong

longitudinal station), and recording the point.

(18)

SETTING UP THE DEVICE

This section outlines the detailed steps in the setting-up process.

General considerations relevant to this phase are also discussed in Section

1. select the minimum distance y so that the deck can bé reached at the

maximum beam location as

_{showR in}

Figure (5)..

2. Measure out (approximately) the

centerlines and place a marker

line".

Place the Instrument at one end opposite end approximately as shown (A large object e.g. boat or car, being moved during the measurements

-13-Figure 5: Section View

at BMAX Station.

distance y from the 'bów and stern (e.g. a rock). This defines the "base

(bow or stern) and the. targets a.t the

in Figure (6) See also Figure (9)

(19)

Ráse Li ne

3. Set the sighting direction of thè

shown in Figure (10),

The view through the

"Far "Near

Targetñ _Target"

--i

I

k1

scope ii its locati

targets. Level the

then adjust targets sighting scope will L = length of the boat

2. should be small, e.g. 10 feet. It is limited by. the minimum föcus

d1stance of the scope.

should be as larce as possible, e q t2=t1+L The minimum practical value is L/2

Fjqure 6: To View of Baseline RánäeMarker Set Up.

on pins on the case. tò point in the

instrument, using the Pitch Level to be closely aligned to the scope.

resemble Figure (7).

Near Target Cross-Hair-s

Scope Cross-Hairs

Figure 7: View Through the Sighting Scope of Targets and Pôsition Error Far Target Grid Readings (Y,Z).

(20)

-14-If the yacht has a significant pitch angle, the targets should be adjusted

so that the sighting line is approximately parallel to the waterline _Once

the sighting line is established, the targets should not be moved during _the

measurnents If the ground is not level, check that the tripod heave adjust range is adequate.

Aim the scope to the point on the ground at the opposite end of the

boat marked AA" in figure (6). Attach one end of the steel measuring tape

to this point and stretch it along the ground to the device _{The x-distance}

will be obtained from this tape.

4. (a) Be sure the instrument is off. _{HoOk up the battery to the}

instru-ment (white lead is (+) and black is neg (-) ) and insert the tape

cassette or "wafer", label to the left Turn on the device.

Advance to the beginning of the tápe (push FAST FORWARD: Tape

will advance at high speed to the first End of lape (EDT) mark It will

then automatically advance at low speed to the second EOT mark The EOT

light will come on).

Record the data, sail number, and Ro as follOws:

(i) Enter the dàte üsing thé thumb. wheels as directed on the

side of the case.

Example: November 5, 1976 would be entered as

-15-Push the record button. [If this is the first time, the tape wii

take upwards of one second to advance beyond the second EDT mark Subsequent data records will be recorded virtually instantaneously

Since this is the beginning of the tape, push the record button again a few times.

(ii) Enter the last four digits of the Sail Number identifyirg equivalent) in thex-thumb. wheels and 8000

thumb wheels Push the record button a few times If

enter the remaining digits in the x wheels and 8001 in wheels and record once or twice.

(or suitable in the code-necessary, the code O 5 X i 9 6 code

(21)

(iiI) Attach thé hook on the string of the wand (the tail) to

the string at the case (Inspect the tip of the wand and the string

for wear. Replace if necessary.)

Measure R0, the distance from the case to the tip of the wand, Figure R, with the string in the retracted reference position

X

CODE

X

CODE X CODE i 6-Figure R Measurement-Distance froM wand tip to the case

Set R in the x-thumb and 8090 inthe C0P ad push he record

button a few timés. Exámple: Rb = 1.15 ft.

1

8 0 9 D

Exam1é: Sail Number 12830

2 8 3.

8 O O O

o O O i

(22)

-17-5. Check the range of the alignment meter (see the discussion of Section

11.5 on page 5) by wiggling the string in the slOt at both high and low angles. Range adjustment can be made using the METER RANGE ADJUST knob on the case.

(23)

ru.

GENERAL CONSIDERATIONS

The following observations concern the method of data identification

and some specific reconnendations on what to measure. _{The detailed}

step-by-step procedure is continued in Section IV.

Clearances and Lével i ng

En order to measure the side of a boat, adequate clearance for the device

to pass a few feet away from the maximum beam is required. A clear sighting

line in one direction is also necessary for the erection of the base line. Note that the targets can often be attached to some object, set on the deck or cradle of a neighboring boat, etc. if there is ño room fOr the tripods.

The boat need not be level, either in roll or pitch, nor does the base

line have to be parallel with the centerline or the waterline The

base-line should be roughly parallel with the centerbase-line and waterbase-line, but only

within about ten degrees The measured offsets will be rotated and

trans-lated so that the final result will be as if everything had been perfectly

trimmed For analysis convenience, it is recommended that the baseline

be inclined in pitch so that it is approximately parallel with the

water-line if theboat has much more than the usual few degrees of pitch. If

both sides of the boat àre to be measured, the baselines on each side need not be parallel (see the comments below).

Recordinq Information and Codes

Every time the record button is pushed, the following steps are executed automatically:

the tape recorder motor is turned on and the tape advances at low speed

four, four digit numbers are written onto the tape: two from the encoders and two from the thumb wheels.

-18-the recorder's tape driver is turned off and it awaits -18-the next record comn and.

Thé information recorded may be interpreted as i) valid offset data (R,G,X)

R

R RR

-i

ri î

X X X X

C

C CC

R

set by the shaft-encoders G

X

1set by the thumb wheels

(24)

-1

9-and code identification (C), òr ii) it may constitute a special message, Such as the month and day (X) and the year (C).

Recording infOrmation multiple times, in general, does _{no harm.} _In

fact, the identification data at the beginning of the tape should be entered

a number of times There are error CODE's that should not be repeated unless

specifically needed (see Section VI) _{Recording the same data point more}

than once will not affect the processing other than to say that it is more important than a data point that was recorded only once.

The CODE number associated. with each data potnt is available to identify

that offset Normally, the CODE number is "0000" If the offset is a

particular point that needs to be singled

Out

for later identification,

e g a waterline point or freeboard measurement point, a special _CODE _can

be set intO the CODE thumb wheel on the. case For example, it is

con-venient to identify the waterline points in order to make an initial

rotation of offsets to level the boat _{The bottom of the boot top is}

usually selected The CODE would normally be changed from "0000" to "0020"

for the recording of the waterline point _{It could then be reset to 0000}

for the remaining pOints on the station Section VI contains a list of

reconnended CODE's, both for normal data point identification and _for

error flagging The meaning of each CODE should be self-explanatory If

more information needs to be recorded, additional CODE's can be used and

their meaning transmitted along with the tape for analysis The most

conunonly used codes are noted with an asterisk (*).

Measuring One Side Only

In order to determine an approximate location of the center plane the following procedure is suggested.

The first point of every station is assumed to be on the centerline,

to the best of the measurer's judgement, unless otherwise indicated by _a

non-zero CODE number in the lowest digit, e.g. "0001". Keels and rudders

should not be included as a valid centerline point _{If one wanted to flag}

a particular station, it can be given a special CODE, e g "2100" All

recorded points would have this identifier in their CODE number The

exceptions might be an invalid Q point, CODE "2101", a waterline point, CODE "2120", or a freeboard point, CODE 112l40t1 Since three points define a plane, a minimum of three station locations should be selected

so that reliable centerline points, with reasonable separation vertically,

can be obtained _{If more than three Q points are obtained, the best}

Q

(25)

Measuring Bóth Sides

If both sides of the hull are to be measured, extensive centerline

jints are not needed. On the other hand, few points common to both sides re required. Normally these common points could only occur on or very

ar the centerline. If three offset points on each side (port offsets and

tarboard òffsets) are known to correspond to the same points, then the

ffsets in the Itwo different coordinate systems can be matched. For this

eason, the base line used for the port side measurement need not be )arallel to the baseline used for thé starboard side measurements.

The only reason to measure both sides is because the boat may be

asym-aetric or a more accurate estimate of the maximum beam is desired. An

idequate number of stations in way of BMAX, etc. should be considered.

The procedure is as follows. Select three of the stations as you go

along as centerline reference points and mark them On the opposite side,

adjust the x-position of the device to hit exactly these same (marked) centerline points. The instrument is set up approximately and the wand

tip extended to th centerline sö it is square according to the alignment

meter. The longitudinal error distance to the marked centerline point can

then be noted and the device shifted by that amount This can be done

usually with only one iteration Alternatively, exact positioning of the

KIlO on the second side can be avoided if the X-distance error is duly noted, either as a. special coded number recorded at the time of measure-ment or written in the log-sheet that accompanies the tape wafer.

Miscellaneous

Number ofpoints on a tape: Every time the record.button is pushed,

approximatelyO.25 iflchés of tape are used. The 16 digits written on the

tape are collectively referred to as a '1record". The capacity of a 20-foot

tape loop is therefore about 960 records. Figuring 15 records of

identi-fication and a conservative average of 20 records per station, then each

tape can hold approximately 47 stations.

Putting more than one side of a boat on a single tape is risky. If the

tape is accidentally advanced to the end,then the new data will destroy the

old. If extra tapes are available., their use is recommended. The loss

of data due to a bad tape will also be minimized.

Record Button: Push the record button deliberately and not too

rapidly in süccessiofl.

Warning: Do not allow the string to retract at high speed (e.g.

if the tail broke at the wand tip) Damage to the delicate angle sensing

arm is possible. This prototype is reasonably rugged but not as robustj as a production model would be.

(26)

-20-

-21-iv) Is it working? There is no guarantee with the present device

that it is working However, digital electronics generally are working

correctly if they are working at all The best way to check is to see

if the lights (LED's) on the wand are lit and, if the string is moved,

flash appropriately A good time to check this is ininediately after

(27)

IV.

TAKING TEMEASUREÑTS

After the instrthiient

is

set up and the indentification information is

recorded, the measurement of stations can begin Note that the detailed

procedure of target alignment and leveling of the case are not as important as CONSISTENCY. Each station should be ttacked in more or less the same fashion so that the end result will be to a conunon baseline For Example,

if the final alignment is done without string tension, the view through the

scope during the measurement will show some misalignment Nevertheless,

if this is done consistently, the resulting baseline will bè acceptable. Make a preliminary alignment of the instrument with the targets using the scope and the heave, pitch, yaw, and sway adjustments at the tripod

head.

The error in position can be computed using the ((,Z) values read from the far target (See Figure 4) as follows:

2.3 Vertical (z) error.= .Z x

£2

£3

Horizontal

_&)

_error = Y x

where £ is defined in Figure 2 and 2.3 is the distance from the

"near target" to the device at any time If _£ = L , the horizontal

and vertical positioning errors of the device are less than or equal to the observed errors (Y,Z) The alignment should be done in a

consistent manner and the position errors (y,z) should be less than 0.01 ft.

Level the case (with string extended) using the Roll Level of Figure (6).

read X-distance with the plumb bob from the tape measure and insert via the appropriate thumb wheels.

check the shaft-encoder reading with

the string in the

reference

slot. If they äre not zero (±one or two counts), re-zero

them by pushing the RESET button. Set the CODE to "0000"

(28)

-22-4 Make the final alignment with the scope with the string _extended.

5 _{Take the station data points, changing thè code as required, as}

follows:

Using the wand, extend the string to the bottom of the station. _If

this first point is not a centerline point of the hull, enter a non-zero

code number in the lowest CODE digit, e g "0001" The correct fore and

aft position of the string is determined by referring to the "alignment

meter" located on the wand (see Figure 7) The alignment meter display

is proportional to the horizontal angle of the string It is limited

by the width of the slot of the case _{Adequate squareness is achieved}

by pòsitioning the st-ing so that the alignment meter is centered in

the middle of its range at any given height (or vertical angle) _The

meter's range and center position is adjusted with the Range Adjust

knob on the case _{The full range of horizontal string motion in the}

slot at both high and low angles should be adequately visible on the meter.

Inspect the range of the alignment meter by moving the wand fore and

aft and locate the center Push the record button Advance up the hull,

using the alignment meter to stay on that station, recording points every so often so that a straight line fit between them would provide a good approximation to the statiön shape.

Record the waterline location, using the CODE "0020", at two (2) stations, one forward and one aft.

Continue' up the station to the deck or rail cap.

If a recording error is made, it is not possible to correct it _by

erasing the bad data. The error must be flagged on the tape by recording

an appropriate error code that can be automatically recognized by the

analysis program. A discussion of error recovery codes is given in

Section VI.

6. _{When finished with (5), allow the string to retract to the reference}

position and record this "zero" _{Normally, the R and O counts will be}

no more than (±) one or two counts The analysis program will ignore

these unless a large residual appears _{This might occur if a circuit}

component had failed or the string had been moved extremely rapidly. Check the X-distance reading and then move to the next station and repeat this procedure.

(29)

-23-LAST STEPS

-24-.

1..

It is convénient to zero un-used portions of the tape.

_{This can bé}

done by pushing FAST FORWARD which will advance to the first end of tape

mark (EOT) at high speed and then to the second at low speed

DO NOT PUSH FAST FORWARD TWICE or the data just taken will be erased

(Note that the second time FAST FORWARD is pushed it will advance at low

speed and can be stopped without too much data being lost

)

This has not

beéfl a problem, however.

AnOthér choice is to récord 9999 in both the, X and CODE five or ten

times to signal the end of information on the tape loop and dispense

with the zeroing procédure..

.2.

_{IÌiediàtely label the tape èassette With the boat-name and data to}

avoid using it again.

Retrieve all equipment or move to the opposite side and start again.

For araiysis, mall tapes and the Lo

Sheet to:

PRArr

PROJECt - HMD

ciò Professor J.. N. Newman

M.I.T.,

RoOm 5-324A

Caflibri dge, Massachusetts

02139

Office:

(617) 253-6809

It is reconunended that the tapes be mailéd in a plastic bag'(é.g. a light

(30)

VI. CODES

One of the four numbers recorded autOmatically each time the record button is pushed is a four digit code which is set by the thumb wheel

on the front of the case The code is normally "0000" The following

codes and conventions are currently recognized by the computer analysis programs. Additional codes or alternative codes can be adopted.

Conventions

The followIng conventions have been adopted to facilitate automatic computer recognition.

Available to flag special Normal codes (waterline,

points or stations freeboard, etc.)

Ex. 2000

2001

2020

NCODE =

Station specially marked with flag 1120t1

-25-Example

A typical set of X's and Codes for a freeboard point station, here noted by the measurer as Stati on 21, might look li ke the foil owing:

1. All 9NNN Codes are Error flags.

-- Ex. NCODE = 9999 -- Attention flag-othervise ignored.

2. All 8NNN Codes are for information, the latter located in the

X thumb

wheels.

--

Ex.

ÑCODÈ 8090 -- XX.XX =

3.

All NCODÈ < OONN are Normal point codes.

-- Ex. 00 00 Normal point (okay for centerline)

00 01 Normal point (do not use for centerline)

00 20 Waterline point

00 40 Freeboard point

(31)

s

-26-CODE X MEANING

(*)l977 MODY Date: month (MO), day (DY)

8000 XXXX

Sail number (last fOur digits)

8d01 XXXX Sail number (next four digits). Use only if necessary.

8003 1111 Starboard side being measured.

8003 2222

Poy't side being measured.

8005 XXXX

ieãsUrer nuffiber.

r (*)OO90 .XXXX R0 = XX.XX PreviOus

Stati on

1256

1256 N CODE 0001 0001 0001

jii

_100

(Okay

centerline point)

1511 2100

15l1 _21Q0 (Waterline point, unmarketh should be

obvious from the plot)

1511 2100

1511 2100 (Special freeboard point could be flagged

with 2140)

0244 2141 (Actual freeboard from certificate entered

as X = 2 44 ft The code --41 indicates

that the last point was the freeboard point.

If

the actual freeboar4 was not

known, entèr zeroes in

the

X)

1757 0000

Next 1757 Ó000

(32)

-27-CODE X MEANING

OO1N XX.XX This is a reference centerline point that is comon to

both sides of the hull and will be used to match the

two sets of offsets. If N=O, then it is a valid

centerline point If N0, then

it

is not to be used

as a normal centerline point. Normally, there will be

three such points; well separated vertically.

(*)0020

XXXX This is a waterline point.

(*)0040

XXXX

This is

a

freeboard point.

0041 XXXX

Actual freeboard XX.XX

ft. measured. (Obtained from a

certificate,

for example.)

(*)___l _XXXX _{Do not}

use this for a centerline point

_{if it is}

the first

point of

Station x = XX.XX ft.

(*)..._O _XXXX _{This is a centerline point if it}

is

_the

first

_{point of}

Station x = XX.XX ft.

Error Codes

If a recording error has been made and subsequently discovered, a

code number should be recorded so that the data set can be corrected

auto-matically by the analysis program

Typical error codes are given below,

but they can be altered or extended as desired.

CODE MEANING

(*)9999

_Attention

(*)0090

XXXX

Use R0 = XX.XX ft. from here on.

9010 XXXX Do not use Statibn x

= XX.XX ft. to supply a centerline

point.

9020 XXXX Do not use Station

X = XX.XX

ft. to supply

a waterline

point.

9lnn The last nn points are bad; disregard.

9200 XXXX Change the previous station x-distance to

the x-distance

shown, i.e. x = XX.XX ft.

93nn The last tin

stations

are bad; disregard.

9301

The last station is bad; disregard.

(33)

*

Most òften used codes.

Number ignored XXXX Numberused

NOTE: For repeated application of the same code, sêparate tht with

9999's For example, the last data point recorded is known to be bad,

so the measurer records CODE = 9101 one or more times to signal the

error tf it was then noted that the previous data point was also likely

to be bad, that point can be deleted by recording the codes CODE = 9999,

CODE = 9101.

(34)

-28-Figure :9. Instrument Alignment

TAPE.

X ST&1i ON

LO C.ÀT%ON

1T'T'

SIGI-TING

LIN

s

FR RAN

TÂRGET

_NE4R

I'ÇE

(CROSs.

R4IRS)

/ p.

6ASE.L% N:

(35)

Figure 1P. rnstrum

_{tcase and adjustment features.}

5%Qçn

_CopE

rnAL

T4

_LEVEL

2 u. CLAMP

ri

CJOTl4 S*')

S

_{JU sr}

:',

r

.1

(36)

-30-o

OFF

2EST.

AM

AA.)Jr

FW4RD

OMFF

RC

Ca6e F'wvt

X

Rp_coìt.d Bwtton

Hand GjtJp

(Ro.te.

Wand TLp)

-31-Length Enc.ode

VIA p144 AngLe. Eiw.odedt

VIA play

X-PIAtaìw..e. PIA pLay

Stg ALnrnent

Me..te..

ON/OFF

Powex 4Ltc.h:

OW £Jght and

dLepj LJgh.t

on twtd 4ko uLd

¿Lgkt

p.

ZERO

Str.utg 4Lgnmen.t Metv .'twtge. adj uA.tnie.n.t btob (t.a..ut gase

ze,wadjuA.tj.

MT[R RANGE

StA 6ha4t e.n.codex c.owttA .to ze'w.

SI.ng .4kouid be LiL The.

.e.tìw.c.ted,

tee..'e.,tc.e. po.t.on.

RECOIWER Vi..gi...taL Tape. Re.c.wr.dex

ì...vi6et nvJvca.tuA.

Lpe

a44e.t.te. oit

FAST FORWARD Aduance.

The. tipe Loop to The. end o

The. tape. (EOT tc.gk.t),

a..s

t goe

FF &gh.t ap peaìr.

h.42e. aduaiwng

RECORD

Re.c.o.'td £_h.t.

X

X-Thwnb wheeLs

u.4e.d 10 enten .the. Lo,igj.tjdjici dí_4Cance.

¿zLong The. hulL (e.g. 10.53

)

a.nd a.ddLtLonaL ¿dLLca.tI.on

paltame.tvt6.

COVE

_{Code-.thurnb wheeLs:}

u4e.d .ta evte,t a. wde. vwmbvt .to IdevtLy

the. da.ta. po.itt bei.ng

e..oitde.d and addLti.onaL LdenLLz.ton

paicaintex6.

ELgwe.

i2.

CASE ÁNV WAN V VETAI LS

(37)

D

MEASURING EQUIPMENT CHECK LIST

** _{Equipment Supplied}

Instrument

sighting scope

device héad 'and bracket

tri pod**

wand & cable battery cab le**

tattry (12v automobile type)

Other

near. target (cross-hairs) far targét (grid)**

recordér tape cassettes plumbbob

metal ,tape

target upports .(2 tripods(?))

Optional Extras

tép ladder log book

battery charger

If prOblems develop r you have questions, contact:

Owen H..: Oakley, Jr. George C1énnèr J. N. Newman J.'E. Kerwin M.I.T., Room 5-324 77 Massachusetts Avenue Cambridge, Massachusetts 02139 (617) 253-6809

(38)

-32-Problem

I. Power switch ON

No lights on case or wand

ri. Powerswitch ON

Nô lights oh the wand

IV. _{Fast Fonvading the tape}

loop to the end Of the tape

(EOTI takes longer than 15 sec. for 5 ft. tape.; 60 sec. for 20 ft. tápe.

Alignment Meter on wand reads zero intèrmittently or continuously

EOT light äppearing inter-mi ttently

Numbers do not return to

zero when string i redirected

to the reference position

E

TROUBLE SHOOTING

i(a) Low battery voltage. (check battery contacts and voltage.)

II(a) Same as I(a).

(b) Brokéh wire in the cable

to the wand. (Check electrical continuity.) V (a) VI(a) VII(a) (b) Same as I(a)

Too cold forthe.elec-tronics, i. e. temperature is significantly below freezing.(Wait

for

_spring) Cassette or Wafér flOt properly engaged. Bad tape. (check tape loop for driver wheel contact and see that it is properly iñ the

cas-sette..)

Zero position not set correctly. (Adjust. zero

knOb on case.)

Broken wire in cable or connection.. (Inspect wire). Broken strain gage or wire on the arm.

Too much light on tpe recorder which is trip-ping the EOT photo cell. (Close door)

Encoders not zeroed in-itially.

String is not winding up

consi stently.

III. Power switch ON

Flickering lights on the _111(a)

wand _(b)

(39)

F

DATA ANALYSIS

The data recorded on the tàpe cassetts cannot be used without saine interpretation. The numbers need to be converted to physical units

(e.g. decimal feet), corrected for an internal shift of the string _away

from the case origin, and transformed from polar to i-ectangular

coordi-nates. 'The offsets then undergo a coordinate transfòrmation from a HMD

centered systemto a boat axis system. The above operations are performed

with the aid of a series of computer programs. The various steps in the process are shown in Figure F-l. Briefly, after the interactive terminal session is initiated., the tape cassette is placed in the tape reader, and the recorded infOrmation is played into the computer which stores it in a data file, here denoted as "BOAT.DATA". The file may include bad data that needs to be corrected or deleted! Such data could be due to a transmission failure or simply a measuring error. Step (3) allows the

raw data to be edited for any known or obvious errors. Figure F-2 shows

the first few lines of an edited, raw data set. The raw data is then scaled and the offsets converted from polar to rectangular coordinates. If sufficient waterline and centerline points are included, the offsets are rotated from a ildevice centered't coordinate system to a consistent

"boat axi s" sys-tem

An example of the rotated offsets is given in Figure F-3. A plot of

the body plan, such as the One shown in Figure F-4, can also be produced

as a quick check to see that everything is working properly. If the data

is in order, it is then fed into the "lines processing program (LPP)" in Step (6) which compútes various hydrostatic properties of the hull that may be of intered. Preliminary LPP output for the. port and starboard sides of yacht nuff ber 3686 are shown in Figures F-5 and 6 and the body plans in

Figure F-7. The data in each of the four columns of. Figures 5 and 6 are

for the four conditions of (1) datum waterplane or determined from freeboard measurements, (2) ibid, two degrees heel, (3) ibid, 25 degrees heel, and

(4) upright, "sunk condition" with a waterplane elevated by 2.5% fOrward and 3.75% aft. For éach of the above four conditions, in addition to the

(40)

-34-

-35-hydrostatic quantities listed at the top half of the page, three lengths are determined including the conventional waterline length

(LWL), the length based on the second-moment of the sectional _area

curve (L2M) and a new length (LSM) based on the second moment of the square root of the sectional area curve.. A further discussion

(41)

Scale and Rotate

the Offsets

BOAT.ROT.DATA

plot the Résüits

LPP

BÒAT.I.PP.bATA

4

.4

'i,.

Figure F-1

Data Processing Sequence

INPUT/QUTPT

STEP t

(1) Initiate Compüter.

Session

Tape

eader

-

(2) Read Data and Store

In File set

BOAT. PATA

I

;'

j

(3) Edit Data for

Errors

Corvert iotated

Data to LPP

(42)

N

4-i . O id

li,

Pi ai u (.1 U) a, ai

k

t'

OOO00000Ot

OCJOOOO( OOOOODOOOCQ

OOQr,

Q

o jçj(C

I. -4O 00 0

1 ) b

Uìbti )

!a U ) Li b -O. (:

c c'- c

o. C

__%

Oooc'l-0000

ra oeeJm

oq-r

O)I C

tk1k1i

o o o o

c o o o o o o o o

o o o o o 0 0 0

O

CS o o o c' 00 0 0 0 0

0 0 0- 0' 00 0 0 010 00,0

000 (

c ci ii)

ri

O}N w.o OErlOE o ct

0'4O N in

N k) riti ON 't 0e1

M CtO FsC) Ü

' )M ¡

r

-t k)

3'N' l,

-'csr4- icor5.

o a

rC 0300 0000000000000000

lOO 0000 OE0

000000 O.O.o) O li oOoo,o

O C'O 000000 00 0 0

4 bi 'ON C) O. O '-i ti q

WO 00 M

in o 'O rs o 0.0 '4 tIM

lJ Co Co 0.0.0

rl ti 'r In 'O Nc 0.0 '-I r4t'

In 'O N W 4

00 ,,-i '4v-i'4

-i '4 tI ti ti ('4 (414 Citi

('ICiti

MMr,tirq M M

i

'r 'r 'r it 'r hi in in in lo in bib-ibik)

'o 'O..O 'o 'oo'o

l_O 000 0 00 00 00 00

00 00 OOO

00000000000000000000000000.000000000000

0000 00 00 OC' 000

0000000

(43)

t

t t t t t e e t

t

-cl is.iJ our:. ti '-i on cow o ti o ui

-o .4t I.)

. NC) O Ui C'io ocp co - c' '0 0tn-o Cø-Cp. CI '00 '0

I.)

l. -.5-. I.l- ll

)*-l-e

I-il'.F

F-'1-' P'i'P' t) 00000 )0Q')

1 () Q00O0',"'.-' .

ru rn o ti) O (4 w 1!

i-

-I-?))(,ZZ

'Cr-. O- D'O- 0' 0' 0' ().Th O-O' D'-O' (Ji-Ui (JI UT 'UI UI (fl'UI Ui

b b .

b .b.b -b b

(4 C'I (I L4(4N N C'lt.) tjt. M

-e -<1C)

i.. I-' ê-' 1-' i-.

o

t --4 --',

rr

-II-4

*

O-IN

":12 --I--I

--r wu

'-"i.-'

-p-i--l-41-' I- P5

1--'l-F-:l--'i-'

ê-I.. I-' I

i-i 7 e.

0' 0' (. C.. 0' Ci. 0-0-0' 0'. 0.0.0' C4N14 N (ti N (.4W C'I 'O '0 '0 '0'O'O '.1 CO (i- 0-Ct. D--0- Cr'

Cr' D-. N N N W o

z -< rn

t t t

t

t t -t . t t t t e e .

t

s s e e e s e . e s

t

s

t

.-.4,..

il pp

'J 'J 'J '-J '-J'.J'-J

J-Nl 'J '-J "J "J 00

i-'i-' F-P' P-F-' 1

'0 '0 '0 '0 0 '0 -0 0 0 'J '-J NI "4 '-J

J "J '-'J I-J 1-J M M O -z O 1 F-' f) C'I Ji. (-1(4 C'

C.') (i! O'- 0- CU '-00- " '" F- t) N- N 0' '40) '0 '0 '0 '0 0 F-' O -i-'

t'.) N (1 (.4 .A b (J)

(r' "-J (0

(tI-o

i--'

(44)

Figure F-4,

Body plan from the sc4led and rotated

data.

(45)

-3g-MIT - H IRVING

PRATT OCEAN RACE HANDICAPPING

_PROJECT

LINES. PROCESSING PROGRAM

MAY 1977

YACHT NO. 3686

MEASURED ON

5/26/1976

PORT

_{WITH PRATT tIEV}

FREEBOARDS FROM: bR CERI 1/23/72

STEMHEAD' LOCATION,:

XMEAS= -2.13

_{XRLWL(1)= -4.27}

!F901 2.27

1LBG=33.85

_{FF(1)= 4.03}

_{FA('l)= 2.92}

* i

*

2 * 3 * 4

* . * * * *

HEEL

tIEGREES *

0.0

*

_{2.000 * 25.ÓO0 *}

_0.0

_*

FREEBOARD Fut' (AT 0.0

F1) *

3.892 *

4.006 *

3.154 *

FREEBO.Rt AFT

(AT 30.676 FT) *

2.889 *

2.893 *

3.520 *

1.800 *

DISPLACEMENT

CUBIC FT

*

276.9 *

277.0 *

488.8 *

DISPLACEMENT

POUNDS SW

*

17723 *

1772? *

31281 *

LCB Z AFT OF FUD END OF LWL(1)*'

51.18 *

51.15 *

52.83 *

VCB ADOVE WAT'ÈRPLANE(1)

FT *

-.1.03 *

-1.03 *

-0.70 *

-0.39 *

VCG AEOVE LJATERPLANE(

FT *

-0.01 *

-0.01 * -0.01 *

RM/t'EG HEEL LBS-FT/t'EG * 0. *

1064. *

833. *

0. *

WETTED SURFACE

SO FT

*

289.7 *

289.5 *

279.1 *

373.9 *

LATERAL PLANE AREA

SG FT

*

39.5 *

89.4 *

723 *

1.18.1 *

PRISMATIC COEFFICIENT

*

_{0.503 *}

_{0.514 *}

_{0.542 *}

LWL

*

30.63 *

30.68 *

30.32 *

32.60 *

LSM

. *

29.04 *

28.80 *

32.38 t

L2 .*

27.66 *

27.65 *

31.41 *

AVERAGE LENGTH

30.05 SECTION AREA CURVES - AREA

I

SO FT AT GIVEN POSITION IN FT AFT

INPUT -

REF LWL(i)

* 1 t 2 * t

4'

t.

3

3.803

1.659

*

0.37 *

0;57 *

0.47 *

2.20 *

4

5.862

3.718

*

2.36 *

4.29 t.

5.49 *

5

8.642

6.498

*

5.54 *

5.55 *

5.84 *

10.69 *

6

11.019

8.875

*

10.53 *

17.88 t

17.88*

17.66 *

27.67 *

10

20.903

18.759

*

16.09 *

15.99 *

26.06 *

11

23.278

21.134

* .13.51 *

13.32 *

13.54 *

23.27 *

12

25.450

23.306

*

9.65 *

9.66 *

10.02 *

18.82 *

13

27.368

23.224

*

6.03 *

6.17 *

14.20 *

14

49.50

27.406

*

1.73 *

1.53 *

7.98 *

15

31.424

LPP output fo

the port side

(46)

41SECTION AREA CURVES AREA IN SQ FT AT GIVEN POSITION IN FT AFt

-INPUT

NOTE

_{TRAPEZOIDAL DISPLACEMENT IS}

_{0.18 PER CENT LESS THAN SPLINE}

Figure 'F-6

tP

òutput

fór the s-tarboard

side of the

' *

9.28 *

9.2.9 *

9.46 *

15.82. * B

13.463

10.23-7 *

12.42 *

12.42 *.

12.55 *

20.10 *

9

14.962

11.786

*

14.91 *

14.36 *

24.05 *

14

25.640

22.464

*

11a07 *

11.08 *

11.21 *

20.24 *

15

27.450.

24.274

_{0.42 *}

_{0.35 *}

_{4.18 *}

19

34.412

MIT - H IRVING PRATT OCEAN RACE

_{HANDICAPPING PROJECT}

LINES PROCESSING PROGRAM - MAY 1977

YACHT NO. 3686

MEASURED ON

_{5/26/1976' STARB WITH}

PRATT tiEV

FREEBDARDS FROM: IOR CERI 10/23/72

'STEMHEAD' LOCATION:

_{XMEAS= -1.10}

XRLWL(1)= -4.27

'FGO'= 2.27

_'LBG'-338

_{FF(i)= 4.03}

FA(1

2. * i * 2 * 3 * 4 * * _*

HEEL

DEGREES

*

0.0

*

2.000 FREEBOARD FWD

(AT

0.Ö

FT) *

3.962 *

3.862 FREEBOARD AFT

(AT 30.713 FT) *

2.898 *

_2.903

DISPLACEMENT

CUBIC FT

*

274.0 *

274.0 DISPLACEMENT

POUNDS SW

*

17534 *

i734

* * * * * * * 25. 000 *

3.979 *

3.310 *

274.2 *

17547 *

0.0

3.120

1.806

481.3 30801

* * * * * * C. i

LCB Z AFT OF FUJD END OF LWL(1.)*

-iv. *

50.89 VCB ABOVE WATERPLANE(1)

FT *

-1 .04 *

-1.04

VCG ABOVE WATERPLANE(1)

FT *

-0.25 *

-0.25

RM/DÈG HEEL

_{LBS-FT/trEG *}

0. *

_1064,

WETTED SURFACE

SQ FT

*

284.3 *

294.2

LATERAL

PLANE AREA

SQ FT

87.6 *

87.5 PRISMATIC COEFFICIENT

*

0.508 *

0.508

* * * * * * *

50.90 *

-0.72 *

-0.25 *

'855. *

274.3. *

71.4 *

0.515

52.32 -0.39

-0.25

0.

367.0

116.6

0.540

* * * * * *

LUL

_*

_{30.71 *}

_30.72

LSM

*

28.97 *

29.97 L2M

_*

_{27.85 *}

_27.83

AVERAGE LENGTH

30.10

* * *

30.30 *

28.68 *

27.72 *

32.74 7-,

_{- . -.}

.7

31.27

* *

(47)

o

o Q o o Q Q o a a a

VRCNT NC. 3685 HEASUR(Q CN. 5/26/1976 PORT 510E

JQ .5.0 -i.00 -2.Q0 0.00 2.00 1.00 0.00 B.6Q

TRCIIT NC. 368a MRSuP.E0 CN 5126t1976 5TRfieCa0 5OE

Figure F-7

EMD body plans of KATRINAo

a

o a a Q o

a

o