J-Boat investigation for H.S. Vanderbilt, ESQ. relating to the design of Ranger

(1)

TOTT( TMTK

Storens Ins-ttu±e of Techr.ology

Bloljoken, Iie

_Jersey

PEPO?T rTo.

JBOAT InV1STIGATION

for

E. S. VMTD:RBILT, ESQ.

relating to the design of

fl A T G E R

by

W. STÀRLIG BURGESS, ESQ.

and

SP.RKiAN STEFTIETJS, IITC.

Deift University of Technology

Ship HydromechaniCs laboratory

Library

Mekelweg 2

26282 CD DeIft

Phone: +31 (0)15 2786873 E-mail: p.w.deheer@tudelft.fll

(2)

-

i-Index

PART I

Basic InIoimatjon und Test _Results

PAGE

ScriDtiofl

of Hodels

3

General Order of Procedure

5

Vertical Fesistances, All Boats

6

Final Close-Hauled Comparison, _{All Boats}

9

Hull Characteristics at Fixed Lateral Forces, All Boats - ₁₅

Final ReaohinT Comparison

17

PART II

Detailed Tests an _{SDecial InvestiGations}

Preliminary Close-Hauled _{Comparison (vrith JEETANOE)}

21 Effective fetted Area

23

Preliminary Study of Function _{of Centerboard, EfDEAVOIJR I}

. 25

Reliability of Calculated Best _{Values of V5, PAINBOVI and}

YA!TIE 27

Kinetic Stability

29

Further Study of Function of Centerboard, 77-C ₃₁

Detailed Comoarisons of Hulls

36 77-C iith 77-D at 30° heel

77-02 and D2 vith 77-C and D

. Encountered 'iaves 40 Balance of RAIiTflOT 47 Preliminary Balance of 77-C 52 PART III RANGER

Final Balance of 77-C, Effect _{of Centerboards}

55

18, _{Selection of 77-C for RMTGER}

63

APP DIC ES

A _{Test Points of Close-Hauled SDeeds, RAINB}

64 B _{Correlation of Stevens an-I}

7ashinton Vertical Pesistances, _77-C ₆₆

C _{Estimates of Centerboard Pressures, 77-C}

74

NOTE: - A Dreliminary consideration of pick-up, _{made on the}

six-meter boats TOOD and IIDIAH _{SCOUT durint' the}

course of this

in-vestigation, is discussed in _Technical

emoranchnn No. 20.

(3)

ç

2--PAJ' I

(4)

*

_{An inaccurate model}

of 77-B, designated

_{77-X, was tested}

_{for vertical}

re-sistance only.

_{It is not considered in this report.}

R-34

scrirition of "ocls

This report

_{considers the tests of}

twelve* modele

-TTEETÀMOE, with 1936

_keel.

_{Data from Report No.}

12

DEAVOUJ I, with

_{estiriated centerboard}

AflTBOVT, with 1936

_keel

T7-A,B, C, D, the

_{first group of}

_{new 87 ft. designs}

77-C2, D2, the originAl C and D models with the rudder

_extended

_profiles

the C model with fortvard sections reduced to avoid

over-displacement, and counter lat7ered.

a new wide model

77-CE, a cmb'tion

_{of the forebody of C, with the afterbody}

of E.

Particulars are given

_{in Fig. 1.}

(5)

-5-2. Genere]. Order of Procedure

TACE had been tested previously, and was referred to only for

pur-poses of comparison.

77-A, B, C, and D, were designed while the tests of FEÏDKAVOtTR I and RAITTBOT were in Progress.

77-C

and D were tested before

77-A

nd B,

end were altered to 77-C2 and

D2 while the tests of

77-A

and B were in progress.

On the basis of the test results through and including those of 77-C2 and D2, it was concluded

-- that the 87 ft. L.W.L. was desirable.

- that the extension of the rudder profile, as in 77-C2

and. 2, was undesirable.

- that 77-C was the most promising of the new models, and that attention miht vieil be concentrated on the possibility of improving her.

- that the widest model, 77-A, was undesirable, but that another model of comparable width ought to be tried.

77-E and CE were then designed in an attempt to improve 77-C without departing materially from her lines, and 77-F in an attempt to provide a better wide model.

On test, 77-F was not found superior to 77-A, nor were 77-E or CE found

superior to

77-C.

77-C was finally selected for RANGER.

(6)

6

3. _{Vertical Resistances, All}

Boats

Tabulation

Fig. 2 Curves for PAIfl3C)TT, EUDEAVOUR I _{and RANGER} _{Fig. 3}

For all of the tests considered in this paragraoh, the centerboards

were removed from the models1 and the slots filled in with wax. The

cal-cula-tod wetted area of each boat _{was used in expanding its measured model} resistances. _{The sand corrections, sho'm in Fi. 2, were determined (in} most cases) from two runs, with strip widths of 1/2" and 1" respectively.

The fact that ENDEAVOUR I has the _{lowest sand coefficient of all the}

models may mean that her calculated resistances are a little on the high side. _{There is evex-,r reason to}

suppose, hovrever, that the resistances of 77-C are in general less than those of either RAIHBO{ or ENDEAVOUR I.

It will be noted that the resistances of 77-C compare very favorably

with those of all the other boats at all speeds up to about 9 3/4 knots,

and that they are lower than those of any other boat for the range 8-9 3/4 knots. _{They are appreciably higher than those of several other boats at}

high speeds, and this fact led to _{the low counter profiles adopted for}

77-E and CE. _{The lower counters helped the hi'h-speed resistances to some} extent. _{But these resistances were not considered of sufficient}

moor-tance to influence the final selection of 77-C for RANOER. A difference

of 500 pounds in the vertical resistance at speeds of the order of 12 to 13 knots, corresponds to about i/io of a knot difference of speed.

(7)

-9-4. _{Final Close-Hauled Ccnarison, All Boats.}

Curwes of best V vs. VT Fig. 4

Tabulated values of (F cos o), )., and C.L.R. Fig. 5

tta.iled Calculations for

vou I Fig. G

Fig. 7

77-C, RA1GER Fig. 8

For all of the tests considered

in

this oaragraph, the centerboards

were dropped 7 ft., and their wetted areas were added to the calculated wetted areas of the boats in exoandinr the heeled model resistances.

The tests were r with (in most cases) a 3/4" sand strip, the sand

cor-rections being consistent with those in Fig. 2.

Referriig to Fig. 4, it will be noted

-- that 77--C is the best boat at all wind steeds less than about 16 Imots and that she is only slightly

Inferior to 77-A at very high wind speeds.

- that the next best boats are 77_CE and 77-E in that

order.

-

that the second wide boat, 77-F,, has much the same

deficiency as the first wide boat, 77-A, at very low wind speeds.

Because it was argued that wind speeds of less than 16 lniots were much more likel'r to be encountered than wind speeds greater than 16 knots, it was concluded from Fig. 4 that the choice for BÌJJGER lay beLween 77-C and

Photographs were taken

of

_{the weather side of all of the models at}

Speed o. Knots Heel Angle

19 9.631 200

21 10.40 30°

with correct lateral forces. These hotograohs (copies of which are

avniJable) show _{a cicaei- ouarter wave for 77-C than for any of the others.}

(8)

R 34 - Fig. 5

StaMlfty, Lee-ways and Lon.

_C.L.R.

FINAL CLOSE-HATJLED COTPARIS0

_{(All floats)}

Víith Centerboards

100 _Heel

_{Sp. No.}

Caic.

No.

(F11 cos e)

13 X

Degrees

14 15 15

C.L.R.

% L.W.L.

14

15 Rep.

12

EETAH0E 3

EDAV0UR I

_VIII

₆₄₁₀

_2.51

_2.22

_1.97

46.21 46,07

46.00

RAIJflOEY _V

₅₇₆₄

_2.45

_2.20

42,57

77-A

_II

₇₂₆₉

_3.02

_2.70

2.43 48,00

46.60

48.60 77-B

_II

_f665

_2.89

2.62

2.37 _47.00

_46.64

_46.84

77-C (PJdTCER)

III

₆₄₉₅

_2.67

_2.45

2,24

45.01 4483

44,69

II

6225

_2.53

_2.26

_1.98

_46.44

46.44 77-C2

_VII

₆₃₆₇

_2.80

2.55 _44.21

_44.21

V

₆₃₂₅

_2.74

_2.45

45.63

45.63 77-E

_II

₆₅₆₅

_2.74

_2.49

2.27

46.71

46.71 77-F

_II

₆₉₇₅

_2.92

2.61

2.31

46.34

46.33

46.33 77-CE

IV

6508

_2.61

_2.35

_45.91

_45.47

200 _Heel

_{Sp. No.}

19 20 21

19

20

21 TfEETK0E //r 3

₉₆₄₀

_2.47

40.60

EHDEAVOTTR I

₁₂₁₈₀

_2.57

_2.30

1.98

46.90

48.17

49.79 RkIHB07

₁₁₄₀₀

_2.68

2.41

2.14

44.45

45.71

47.26 77-A

As

₁₃₈₁₁

_3.14

_2.79

_2,47

49.45

50.51

52.16 77-B

₁₂₉₀₀

_2.99

2.73

2.49

48.81

49.73

50.85 77-C (RJ:GER)

₁₂₄₇₀

_2.80

_2.49

2.20

46.57

47.52

49.56 77-D

₁₁₈₄₀

_2.61

2.30

2.00

49.29

50.78

52.53 77-C2

₁₂₃₅₁

_3.03

2.74

2.45

44.62

45.43

46.51 77-D2

_Above

₁₁₆₈₀

_2.78

2.47

2.18

47.49

48.52

49.86 77-E

₁₂₆₂₀

_2.88

2.54

2.21

48.48

49.95

51.75 77-F

₁₃₂₂₀

_2.92

2.57

2.24

47.95

49.09

50.58 12530

_2.73

_2.35

_2.14

_47.66

48.78

50.30 30° Heel

Sp. No.

₂₀ ₂₁ ₂₂ 20 21 22 WEETACT J! 3

₁₃₁₅₀

_3,63

_3.08

2.46 _45.04

_47.65

_52.56

EDEAV0TTR I

₁₅₉₄₀

_3.54

3.07

2.70 _49.93

_51.48

_53.36

RA1I507T

₁₅₁₃₀

_3.81

3.37

2.98

47.55 49,93

52.66 77-A

_As

₁₈₂₃₅

_4.30

3.88

3.54 _50.85

_52.44

_54.46

77-B

₁₇₁₁₅

_4.42

3.97

3.55

51.05

52.75

54.98 77-C (PACER)

₁₆₅₉₀

_3.05

3.d2

3.00 _49.36

_52.07

_54.73

77-D

₁₅₈₁₁

3.72

3.37

3.05

51.30 _53.22

_55.10

77-C2

₁₆₆₃₃

4.12

3.62

3.15

48.28

50.85

53.95 77-D2

_Above

₁₅₉₄₀

_3.91

3.44

3.02 _51.47

_54.39

_53.02

77-E

₁₆₇₁₃

3.99

344 _2.94

_51.86

_54.23

_57.23

77-F

₁₇₄₀₀

3,95

3.49

3.07 _50.77

_52.80

_55.50

77_CE

₁₆₇₄₀

_3.73

_3.31

2.90

50.14

51.82

55.29

(9)

Calculations for Wind and Boat Speeds

E1DEAVOUR I 0

Sp. No.

100 With Centerboard

20°

Calo. No

VIII

30°

12

6.947

13

14

7.329

7.711

15

8,098

19

9.63].

20

10.02

21

10.40

20

10.02

21

10.40

22

10,79

R5

1212

1317

1424

1565

2685

2955

3388

3530

3900

4465

(F11

6410

12180

15940

F11

6508

12962

18408

COO

.1891

.2055

.2222

.244].

.2205

.2427

.2783

.2215

.2447

.2001

S 13.4-0

14.30 15,19

16.38

13.40

14.55

16.46

11.83

12.91

14.56

KR

.877

.952

1,023

1.120 .750

.822

.943

.529

.578

.657

VA

13.57

13.58 13,62

13.65

21.85

21.89

29.83

30.00

0.11 (p + x)

19.95 20,84

21.71 22.9].

20,95

22.20

24.10

21.55

22.61

24.5

Y

38.54

42.00

45.65

49.91 35,90

38.94

43.00

31.72

33.70

36.58

VT

7.435

7.220

7.030

6.948

13.34

13.15

13.10

20.85 20,80

20.75

V

5.438

5.445 5,390

5,214

7.800 7,790

7,600

8,520

8.645

8.663

X

2.80

2.51 2,22

1,97

2.57

2.30

1.98

3.54

3.07

2.70 Lon:. C.L.R,

46.43 '16.21

46,07

46.00 46,90

48.17

49.79

49.94

51.48 53,36

(10)

Calculations for Wind and Boat Spood

PA IN BOW -0

Sp.

o.

100 With Conterl)oflrd

200 Calo. No, V

30°

12 13 14 19 20 21 20 21 22 iT

6.947

7.329

7.711

9.631

10.02

10.40

10.02

10.40

10.79

1153

1241

1355 2670

2930

3363

3555

40.23

4678

co

e)

5764

11400

15130

5852

12132

17471

co

0)8

.2000

.2153

.2351

.2342

.2574

.2950

.2350

.2659

.3092

14.00

14.81

15.87

14.09

15.28

17.20

12.48

13.91

15.93

hR

.926

.995

1.079 .793

.870

.990

.557

.625

.720

12.60

12.89

12.94

21.19

21.21

21.28

29.17

29.29

29.43

(

+ x)

20.53

21.34

22.41

21.71

22.90

24.83

22.16

23.60

25.62

Y

41.46

45.06

49.26

37.93

40.94

45.09

32.90

35.48

38.99

V

6.815

6.627

6.510 12,75

12.61

12.51

20.26

20.18

20.25

V

5.207

5.180 5,035

7.596

7.565

7.340

8.412

0.470

8.386

X

2.72 2,45

2.20 2,60

2.41

2.14

3.81

3.37

2.93 Lon. C.L.R.

42.64

42.57

44.45

45.71

47.26

47.55

49.93 52,56

(11)

o

Sp. ITo.

Ca1ou1tion

for Wind and goat Speeds

_{77.-C (RANGER)}

WiIh Centerboard

100 20°

Calo, No. III

30°

12 13 14 15 J.9 20 21 20 21 22

6.947

7.329

7.711

8.098

9.631

10.02 10,40

10.02

10.40

10.79

R8

1097

1178

1282

1409

2535

2787

3158

3523

3914

4529

(FE cas

6495

12470

16690

FE

6594

13270

19273

co

o)

.1690

.1814

.1975

.2171

2033

2235

.2532

.2110

.2346

.2713

12.29

12.97

13.86 14,90

12,47

13,53

15.04

11.33

12.46 14,18

.785

.841

.913

1.000 .691

.758

.855

.502

.554

.639

VA

13.65

13.56

13.68

13.70

22.11

22.14

22.19

30.59

30.69

30.74 + x)

18.81

19.50

20.39 21,43

20.08

21.13

22.66

21.03

22.13

23.88

Y

36.41

39.44

42.98 47,04

34.27

36.85

40.28

30.60

32.68

35.69

VT

7.419 7,178

6,988

6.838

13.48

13.32

13.22

21.53

21.40

21.36 5,591

5.660

5.641

5.519 7,960

8.015

7.935

0.615

8.750

8.765

X

2,96

2.67

2.45

2.24 2,80

2.49

2.20

3.85

3.42

3.00 LonG. C.L.R. %

45.43

45.01

44.83

44.59 46,57

47,52

49.56

49.36

52.07

54.78

(12)

15

-5. _{Comparison of Hull C}iaracteristics}

at Fixed Lateral Forces, All Boats

Tabulation (EETMOE omitted) _{Fig. 9}

This table shows the heeled _{resistances and leevtays which}

would occur,

at given speeda and heel angles, if all of the boats had the _{stability of}

77-C. _{It, therefore,}

comoares the hydrodynn.io characteristics of the

hulls, quite apart from their _stabilities.

It is interesting to note that this comparison indicates higher

Wj_

herentN resistances _{for 77-A, as cornoared with 77-C,}

in every case, and0

that these are reflected _{in the lower values of best V}

for 77-A at 10

and 200, in Fig. 17. _{In other uoids, the greater stabiity of 77-A does}

not offset her greater inherent _{resistances until hih heel angles}

are reached. _{An additional calculation for the values of best Vm}

for 77-C, in which she was arbitrarily assimied

to have the stability of 77A (see

Fig. 17), indicated an improvement in 77-C at every heel angle. Thus it

my be concluded that the higher inherent _{resistance, and not the greater}

stability, is responsible for the relatively poorer performance of 77-A at moderate heel angles.

It appears, then, that within reason, for boats of this class,

- inherent resistance is more important than stability* at lavi and moderate heel angles.

- stability* is more important than

inherent resistance at high heel angles.

* _{This refers to stability}

obtained by altering the hull form. The 77-C

calculation on 77-A stability,

as well.as numerous similar calculations for boats in other classes, sho;rs

the desirability of the lowest possible center

of gravity, whatever the hull form.

(13)

Heeled Reietance

and Leeway Angloo at Stability

of 77-C, RANGER

With Centerboard

Bed

An1lc

Speed ro3.

c

Calo.

12 100 13 14

6495

15 13 200 19 20

12470

21 19

300

20 21

16690

22

Fes s±anco

DA7C'UR I

VIII

1232 1323

1436

1558

2493

272].

2978

3429

3359

3593

3981

4544

V 1209 1278 1389

2532

2558

3018

3435

3526

3776

4296

4925

77-A

II

1161

1243

1347

1482

2480

2637

2821

3287

3425

3730

4015

4680

77-II

1137

1249

1392

1472

2463

2631

2853

3213

3523

37G8

4163

4759

77-C ÇRAJGDR)

III

1097 1178 1282

1409

2358

2535

2787

3158

3257

3523

3014

4529

77-D

II

1177

1267

1382

1504

2466

2689

2920

3296

3415

5014

4166

4699

-VII

1205

1267

1385

2816

3092

3459

3959

4379

4359

7 7-D2 V

1082

1247

1365

2625

2007

3206

3751

4141

4090

77-j

II

1068

1220

1297

1524

2544

2632

2929

3407

3362

3639

4018

4597

77-F

II

1134

1272

1371

1469

2495 2618 2966

3209

3306

3616

3981

4560

77-Iv

1117

1197

1295

1493

2446

2560

2858

3204

3493

3645

4±:)7

Leeivay Anle

EiDEAVOUR I

VIII

2,80

2.55

2.26

1.99

2.88

2.59

2.28

2.02

4.15 3q62

3.17

2.32

RA I ECW V

3.00

2.69

2.53

3.21 2,96

2.57

2.37

4.69

4.20

3.76

3.37 77-A

II

3.02

2.71

2.45

2.14

3.09

2.69

2.35

2.06

4.46

3.93 3,52

3.17

77-13

II

3.11

2.88

2.61

2.26

3.29

2.96

2.69

2.41

4.79

4.34

3.85

3.48 77-C (rxcER)

III

2.96

2.67

2.45

2.24

3.13

2.00

2.49

2.20

4.28 3,35

3.42

3.00 77-D

II

2.96

2.67

2.39

2.08

3.06

2.78

2.39

2.14

4.40

3.95

3.50

3.23 77.-02

VII

3.10

2.82

2.61

3.06

2.76

2.49

4.24

3.64

3.11

7 7-D2 V

3.11

2.82

2.53

2.92

2.59

2.32

4.15

3.60

3.25 77-E

II

2.92

2.65

2.43

2.26

3.15

2.00

2.43

2.26

4.36 3,93

3.52

3.06 77-F

II

3.04

2.74

2.54

2.14

3.13

2.74 2,9

2,04

4.15

3.97

3.41

2.02

IV

2.94 2.6].

2.35

2.26

3.11

2.72

2.34

2.14

3.73

3.29

2.88

(14)

. 17

-6,

_{Fil Reachin Corison}

Curves of' V5 vs. VT fors 90° _{FIg. lO}

fl1DEAVOUR I

RAINB7

77-C (WIGER)

Based on

- special heeled

tests without

_{centerboards,}

- o o

at 10 and 20 _{heel, and at high}

_speeds.

-

an extension of the GTMCRACK sail

coeffi-cients

to the higher S _{anc-les which}

corre-spond to reaching with VT abean.

Because the tests did. not

_{cover heel angles}

_{of less than 100, the}

curves in Fig. 10 cover

reaching at high speeds only. _{The shapes of these} curves aro consistent with the full

range curve for 77-C shown in Fig. 11.

(15)

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(16)

q

PART II

(17)

- 21

7. Preliminary Close-au1ed Comparisons.

Curves of best Vmcj. vs. VT for TAHOE, RAINDO7,

ENDEAVOUR I, ad 77-C Fig. 12

The calculations on which these preliminary curves were based,

fol-lowed the Drecedent set in the WEETAOE work (Ret,ort

12) by iorin the

wetted area of the centerboard in the calculation of the heeled resis-tances. Subsequent investi-ation indicated the oropriety of inc1udin

this area (see par. a), and it wa included in all later work. By

orit-tin it, the curves for the other boats are strictly comparable vrith those

for YEETAIOE.

As the addition of the board area tends to reduce the calculated

heeled resistances, the values of Vng are in general lower in Fig. 12 than in Fig. 4.

(18)

23

-8. Effective Yletted

pj-Chart of vertical resistance differences _{Fig. 13}

This chart shows

the effects on the vertical resistances of three

different types of alteration, each of which _{increased the wetted area.}

Bo&t _Alteration _{% Increase of}

Wetted Area

RAflBOW loading from 84 to 87 ft. L.I.L. 4.4

77-C _{rerrular centerboard dropped 7 ft.} _4.6

77-C _{small centerboard dropped 4 ft.} _1.2

77-D extendin rudder profile 5.0

It will be noted that, except for the addition of the small board to

77-C, the percentae increases of wetted area were almost identical. The

effects on the resistances, _{as shown in Fig. 13, were, however, very}

dif-ferent. _{In all cases the increase of wetted area was included in}

calcu-lating the resistances for the altered _condition.

It was concluded fron Fig. 13,

- that the wetted area added to 77-D by extending the

pro-file aft did not increase the skin _{friction, and may}

pos-sibly have reduced the eddy-n-ing. _{(The model}

resis-teneco of 77-D2, comoared with those of 77-D, were about the sane at low speeds and slightly lower at high speeds.)

-

that

_{nothing definite could be deduced from} _{the RITB07}

testo because of the _{enera1ly different form which}

re-sulted from loadin her dovm. (The orders of magnitude

of the resistance changes are consistent with those found

for SEVE. SRAS (Report Ho. lo), and _{for WEETANOE (Report}

No. 12).

- that the calculated resistances of 77-C with the regular

board were largo enouh, _{even with the board area}

in-cluded, and would have been unreasonably _{large with the}

board area omitted.

The last conclusion is the justification for including the centerboard area

in all subsequent calculations of heeled resistances with centerboard.

(19)

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(20)

25 -9.

_{Preliminarv Studî öf the Function of the Centerboard,}

EîDEAVOR I.

Curves of V

_{vs. VT, at particular values of V8}

_{Fig. 14.}

In Report !o. 12, it was concluded that the centerboard damaged the

close-hauled ahilit' of WEETAMOE.

_{It was, therefore, desirable t.}

_et

further data on the fimction of the centerboard as early as nossible in

the present investiation.

_{EIDEAVOTJR I offered the first opportunity.}

Instead of best

_{1Tmg' Fig. 14 shows actual V}

_{vs. VT, for definite}

values of V, with and vrithout the centerboard. TIe tvo curves 1yin

farthest to the rirht represent values

_{of V5 which correspond closely to}

the best

_{values (see Fì. 4); the other}

_{curves represent values of}

V8 tiTo speed rnmibers (about 3/4 imot)

_loner,

ThIs chart indicates that the centerboard

_{does little good when V8}

corresponds to the best Vm,., as sho

_{by the calculations,* but that it}

becomes important wheneverV3 is

_{reduced (that is, whenever the boat is}

pinched).

_{The question then arises cf the}

_{accuracy with which the}

cal-culations reflect the best values of V5 at n±iich to sail.

*

_{thereby confìrmin}

_{the TEETACE conclusion.}

(21)

27 -10.

_{Reliability of' Calu1ated}

Rest Values of , JIi3c, YJHtEE.

Curves of

and V

vs. 9

Fig. 15

Fig. 15 shows Professor Fay's curve

of V5 for best Vm, vs. 9, based

on sailin data from YiEE in

_1935.

Aainst this arc shown the

calcu-lated values of V

for best 7

for RAINBOW (see Fig. 4), and test points

from RJJfl13T in

1936.*

There is little doubt that Professor

Fay's

curve shoots off too much

to the right at hih heel angles.

e1ow about 22

heel, hovrever, his

curve is in very ood agreement vrith the calculated values for

JNBO'J.

Further,

the RAINBOW

test. noints, a1thouh sewhat scattered, do not

sug-gest any systemrna.tic error in the calculated

values.

*

_{Detailod notes}

recarding the individual test

points

are

given in

(22)

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(23)

No

sin O coz O

₌ ₁₀₀

2.803 _{X 101}

EA

20°

5.270

10_3

30°

7.098 x 10

WEETALOE 3

10°

Lbs.

Ft0

338.3 Lbs.

Lbs.

'J _o Lbs

_.

.4-) Cri OC) E- O E-c 4) 20 ₉₆₄₀ ₉₈₇₅

_.9762

30°

₁₃₁₅₀

₁₃₁₉₀

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E1ÎDEAVOUR I

loo

_328.2

₆₄₁₀

₆₈₃₅

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200

1218G

12820

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300 ₁₅₉₄₀

16760

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RAINBT

100

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₅₇₆₄

₆₂₀₅

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20°

-

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11710

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30°

₁₅₁₃₀

77-A

100 _366.1

_7.66

₇₈₆₀

₇₂₆₉

_.9274

200 14777

13811

.9346

30°

19903

18235

.9162

77-?

100 _368.6

_7.17

₇₄₀₈

6665

.8997

20°

₁₃₉₂₉

₁₂₉₀₀

_.9261

30°

₁₈₇₆₀

₁₇₁₁₅

_.123

77-C

10°

373.0

6.72

7026

6495

.9244

7090

1.009 .9161

20°

13210

12470

.9440

13627

1.031 .9151

30

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_.9138

ir

77-D

10°

369.1

6.60

6625 6225

.9117

20°

₁₂₈₃₈

₁₁₈₄₀

_.9223

300 ₁₇₂₉₁

₁₅₈₁₁

_.9144

Stati.c Stáb.,

X

GT sin O cos O

- Fri co

O EA

54.67 + 6.33 = 61.00

r.

r-I

O.

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r) C) o _{p .cZ} ₄₎ _p -o r-1 C 4) _{t) r-(} C) 4) ç C)) _ci L) ci _C/D O _E-) _C)ci _E-4

0

-? C)) L-' C)ci 4) 30

Analysis of' StabiiiUes

R 34

_Fie.

0 C) O 16 4 o -D 4.) o (D 4.) O r (D _{(D d} _{(D (1)} _t'- 4-) O C)Q) 1

00

o o

00

o

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00

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(24)

31

-12. Further _{tudy of Nunction of}

Centerboard, 77-C RAITGER

Curves of best V, _{vs. VT for 77-C}

Fig. 17 Curves of' RS/(FH

cos e).,, ENDEAVOUR I and 77-C _{Fig. 18}

Curves of 1ee'ay angles, X, ENDEAVOUR I arid 77-C _{Fig. 19}

FIg. 14 indicates _{that the centerboard}

does little good to _ENDEAVC%TJR

_I

when she Is sailed at the best values _{of V3 as shown by the}

calculations. Fig. 15 indicates that the calculated

best values of V3 are consistent with

the observed values _{for RATiT30T. Par. li}

raises the auestion of' whether or not the considerably

greater reduction of stability caused br the larce

centerboard of 77-C may not have an undesirable _{effect on the close-hauled}

ability of' this boat.

Fig. 17 answers the

last nuostion in the negative. It shows that the

centerboard increases the best V _{of 77-C over nearly the}

entire rne of

WInd speeds. _{An examination of tìe}

values of 1T, _{corresponding to lower} values of V5,

as show-n by this crt, indicates tat the centerboard _{is even}

more irnrortant to 77-C _{than to} _{ENDEAVOUR I}

(see Fig. 14) when the boats are

1.4

Fig. 18 throws _{some li"ht on the}

reason for the difference in the

ef-fect of' the centerboard

on these two boats. _{It shows that, particularly} at 10 , and to some extent at 200, the

unfavorable effect of the centerboard on

the ratio RS/(FH

_{cos e)}

is delayed to a higher soeed in the _{case of 77-C}

than in the case of ENDEAVOUR I. _{At 10°, with V5 enual}

ITo. 14

(corresDond-Ing aprroimate1y to best V1 _{in FIgs. 4 and 17),}

the ratio for 77-C is better with the hoard,

whilethat for ENDEAVOUR I is dist5nctly inferior.

At 30 _{, with V equal No. 22, the}

ratios are better for both boats with the board.

Fig. 19 throws additional

light on the behavior _{of the ratio}

cos e) _{just referred to.}

It brinr'-s ou-b the _{very considerably}

greater leeways of 77-C when both boats

are sailed without centerhoards, and the fact that the leewavs are made

very nearly equal when the boats are

sailed with the boards.

Reasonin _{froi Figs. 18 and 19}

together, it may be concluded that the centerboard reduces the

heeled resistance at rolativel low sDecds,vrhere

without it the leewa'r _{is abnormally hih,}

but that it increases _the

resis-tance at relatively

high speeds where _{the leei'ray is moderate}

in any case.

* The points for _{77-C on the}

stabilities of 77-A, _{shown in Fig. 17,}

are dis-cussed in rar. 5.

(25)

32 -In other z'ords, at 1071

_{peods the resistance of the}

_{board itself is less}

important than the extra

_{ros5stance caused by hiih loerray, while}

_at

rela-tively hih soeeis the resistance

_{of the hull cannot be appreciably}

af-fected by rioderate reductions

_{of loe'.'rav and the resistances of the board}

(26)

- 36

13. Detailed Comparisons of Hulls

77-C with 77-D at

330 heel.

Tabule.tion of resistances

Fig. 20

Fig. 4 shows 77-D distinctly inferior -to 77-C in close-hauled ability.

This is partially e

_{lamed by the lower stability of 77-D but principally}

by the higher heeled resistances.

To isolate the cause of the hih heeled resistances, special tests

of

77-C and 77-D were made at 30

heel with no lateral forces.

The results of'

these tests ccmbned rith the basic resistances (oars. 3 and 4) oeruut

sea-arate evaluations of the added resistances due to heel alone, and of the

so-called induced drags.

These are given in Fig

20. Fig. 20 shows Lwu sets of induced drag values for 77-D,

_one

correspond-ing to the actual stabiliti of this boat

and

the other to the stability of

77-C.

_{The higher heeled resistances of 77-D}

_{are brouht about both by}

higher induced drags and by higher resistances due to heel alone.

77-C

and

vrith 77-C and D.

Tabulation of

characteristics Fig. 21

This table gives detailed figures showing the effects

_{on the various}

hull characteristics of extendia.g the rudder profiles

_{of 77-C and D to mce}

77-C2 and D2.

It will be noted that the alteration

-- caused an increase of leevray in every case.

- moved the CL.R. forward in every case except for the D

model at 30

- had minor effects on the stabilities.

- imroved the resistances of the C model slightly at 100

but injured them at higher heel angles.

- improved the resistances of the D model at all heel

angles.

(27)

37

-The vreather side photographs at 300 heel, speed number 21, Indicate that the alteration caused some increase in the quarter-wave disturbance in both eases.

(28)

38

Coarison of Searate Effects _{on Resistance}

of

Heel and Leeway

77-C and 77-D at 300 Heel R 34 - Fig, 20 o) 77-C Speed ITo. ₁₉ ₂₀ 21 22 30°, 30°, 00, (FE o) 16690 (FE = 0

(Fif cos o) _{= O (Vertical)} Induced Drag 3257 2238 1979 1019 3523 2511 2248 1012 3914 2951 2608 963 4529 3646 3160 883 (III) (y (I

Resistance due to Eec]. ₂₅₉ ₂₆₃ ₃₄₃ ₄₈₆

Total Added Resistance ₁₂₇₈ ₁₂₇₅ ₁₃₀₆

1369 77-D 300, 300, 00, (FE cos e) 15811 (F11 ₀₎₃ ₀

(FE cos = O (Vertical) Induced Drag 3350 2358 2050 992 3665 2658 2289 1007 4018 3088 2633 930 4742 3740 3167 1002 (II) (iii) (I)

Resistance due to Heel ₃₀₈ ₃₆₉ ₄₅₅

573

Total Added Resistance ₁₂₉₂ ₁₃₇₆

1385 1575 77-D 30°, 30°, 0°, (FE cos e) 16690 (F11 cos o) - 0 (F11

003 e)

= _{O (Vertical)} Induced Drag 3415 2358 2050 1057 3814 2658 2289 1156 4166 3088 2633 1073 4899 3740 3167 1159 (Fig. (III) (I) on 77-C stab.

Resistance due to heel 308 369 455 573

Total Added 2esistance ₁₃₆₅ ₁₅₂₅

(29)

Comparison of Hull Charactori8tic

77-C2 and D2 with 77-C and D.

Heel An1e

Speed No.

10°

20°

12 13 14 19 20 21 20 30 21 22

X - DoroeB

C

2,96

2,67

2.45

2.80

2.49

2.20

3.85

3.42

3.00 III

C2

3.07

2.60

2.55

3.03

2.74

2.45

4.12

3.62

3.15 VII

D

2.34

2.53 2,26

2.61

2.30

2.00

3.72

3.37

3.05 (ii)

2

3,04

2,74

2.45

2.78

2.47

2.18

3.91

3.44

3.02

(V)

C.L.R. - % L.'T.L.

C

45.43

45.01

44.83

46.57

47.52

49.56

49.36

52.07

54.78 (iii)

C2

44.21

44.21 44,62

45.43

46.51

40.28

50.35

53.95 (viI)

CA to D

46.44

49.29

50.78

52.53

51.38

53.22

55.10 (Ii)

2

45.63

47.49

48.52

49.86

51.47

54.39

58.02 (y)

(F

008 o),

C _C2

(Iii

(vii

6495

12470

16690

6365

12350

166û0 D

(Ii)

6225

11840

151310 D2 (V) 6325

11880

15940

Roostanoo .. Lbs.

C 1097 1178

1288

2535

2702

3158

3523

3914

4529

(III

C2 1083 1166 1258

2595

2862 3216 3676

4077

4631

(vii

D

1152

1252

1361

2622

2861

3266

3665

4081

4142

(ii)

CA D2

1111

1225

1363

2556

2798

3148

3595

3985

4552

(y)

I-J.

(30)

40

14. Encountered V'avos

Estimates of pitching period of RAINBT Fig. 22

Table of excess resistances due to encountered

waves Fig. 23

Curve8 of vs. VT Fig. 24

RAI BC

77-A

77-C

Observation during the strnmier of 1936 led to the conclusion that the

pitchin of J-boats which is accompanied by en occasional heavy pound and

a noticeable reduction of speed, is caused by the comarative1y large seas

which are likely to sveep across the iewport race area. These seas

apar-ently ori'inate off shore; they are in general distinguishable from the shorter, steeper seas built up b.- the local winds, and they seem to have a much more pronounced effect on the boats.

As a background for an attempt to evaluate their effect by means of model tests, the followin" data were obtained, during August, 1936, on

several occasions when important pitching

occurred.

Average Averac-e Average

wave length, X

wave height, crest to trough, h

pitching period, RAIB07 (84')

!A1uE

EETA"0E (84') WEETAMOE (87') 80-90 ft. 2.5-4 ft. 3.8 sec. 3.9 sec. 4.0 seca 3.6 seo.

The pitching amplitude was observed

to

be

irregular, building up

pro-gresslvoly until killed by a heavy pound.

Assuming, for these average data,

V5 9.5 knots

l)i:iig:ii 7.5 knots

(31)

41

-the period of encoimter, T0, 18

'I - 9.5 x 1.669 - 16.05 VTa!

-

20.90 36.95 85

--

_{- 2.30 secs.} 36.95 if the raves were being taken head-on, and

- 7.5 i 1.689 12,67

as before 20.90 33.57 85

Te 2.53 secs.

if the raves were coming from the direction _{of the wind.} _{In either case}

(or with any reasonable values of V3 or Vm) it is evident that the

encoun-ter period, Te, is considerably less than he observed pitchin _{eriods, T.}

Fig. 22 shows preliminary and revised estimates of the natural

pitch-ing period, T, of RIITBC'T. _{The preliminary estimate was rade before the}

observed data viere available, the _{revised estimate afterwards, and with the}

object of determining whether or not the assumption that T = observed T,

would lead to absurd values for the individual radii of gyration, k, of the

several divisions of the total weight. _{fly far the most imorant item in}

the estimates is the value of k for the hull weight. _{That necessary in the}

revised estimate looks high, but perhaps not unreasonably so.

From the foregoing data and calculations, the most obvious conclusions are

-- that the pitching is initiated by the encountered waves.

-

_{that the encountered waves are not regular enough to}

per-mit a steady-state pitching in the _{encounter period to become}

established.

(32)

42

-- that the nitching ceriod is about ocual to the natural -

per-od, and that both of these _{are greater than the encounter}

period.

- that the natural period is not so much greater than _the

en-counter period as to nrevent a succession of enen-counters from

building up the amplitude of natural _pitching. _{with the}

gradual change in the phase which this _{imlies, successive}

encounters evidently build up the artlitude until an an-proach to phase onposition causes a heavy pound dth a defi-nite tendency to stop the pitching.

10 means of avoidiñg this situation suggests itself. The oitching

would probably be reduced òy a substantial increase in the natural

_erod.

But there is no obvious means by which this period could be increased _by

enough to cause a noticeable change, even if the stability of the boat were sorously impaired by shifting weichts to the ends.

The increase of length from 64 ft. to 87 ft. L.W.L. appears to he in the right direction, but its effect on the natural period is too small to be important.

With eQuivalent construction weights T o

)'TT

Fig. 23 shows the excess resistances _{due to waves encountered}

head-on, as determined by model tests of RAITB0W, _{77-A, and 77-C.} _{The tests}

were nade at 20 _{heel, with the proer lateral force}

for each model (par. 4), and in waves of the following sizes.

A h

Long Vaves _{98 ft.} _{2.5 ft.}

Short llaves 68 ft. 2.5 ft.

The natural pitching

_{periods of the models wore adjusted,}

_before

_{test, to}

0.8 sec.

If _{(Tn)m = 0.8}

then (Ta) = 0.8

xf

_{3.9 secs.}

Tests of 77-A were included in _{an effort to discover whether or not her}

wider ben '«oul.:l have _{a noticeable effect on the}

excess rocisaucs. The

(33)

-

43--Fig. 24 shorTs best V _{vs. VT calculated from the unfaired total} re-sistances in the iOfl encotntcred wavec. It ill be noted thr.L, for all

three boats, the hiher resistances do not materially alter _{the calculated}

values of V5 for bec-L V, from those calculated for still water (see Fia. 4). The best value of V _{are, however, anoreciably lower, which} means that the calculations iniicate the decirabilit'T of 1:eeoin the boat

movinr well, throu-h encountered waves. _{The principal reason for this}

in-dication is the fact that the excess resistances in

ri'.

_{23 decrease, in}

general, as V5 increases.

The losses of V indicated by

Firs. 24

are

RAIflBO1T .96 knots

77-A .80 "

77-C .84

(34)

44

-Natural Pjtchn Period

RAINBOW

Restor.n _{Torcue rer Radian, Q.}

Taken from the lines, _{for small displacements}

from equilibriwn, in still wate r

Q - 25 z _ft.-lbs.

Natural Pitching Period, _{(ConDlete cycle).}

T=21TJí.

_21JL

-

3.39 secs.

R 34 - Fig. 22

= 3.80 secs. Radius of Grration, k.

Pro]. 1rni nary

Es t iniat e Second Est iriate (tons) x (ft.)2 _(tons-ft.2) ee1 so x io2 ₈₀₀₀ _{84 x 112 =} ₁₀₂₀₀ RIg 4 x 602 _ioaoo ₌ hull 70 x 352 ₈₅₇₀₀ _{GO Ï 41.8 = 104900}2 154 ₁₀₄₅₃₀ ₁₄₈ 132000 2 k - 104500 679 _k2 132000 - 892 154 ₁₄₈ k - 26.05 ft. k = 29.87 ft.

(35)

X h

Loxg Waves 98' 2.5'

Short Waves 68' 2.5'

R 34

- Fjr. 23

45

-Eicess Pesis-tarices due to _{Encountered Waves}

20° Heel

- _{3,9 sec.}

Speed Tb. 16 17 18 19 20

R&IÎt30VT Lonr! Waves ₃₅₄₉ ₃₆₀₃ ₃₆₇₇

3769 4110 (viii) No ïavcs ₂₂₃₄ ₂₄₄₀ ₂₆₇₀ _2q36 (V) Wave Resistance ₁₃₆₉ ₁₂₃₇ ₁₀₉₉ ₁₁₇₄ Short Waves ₂₅₄₅ ₂₆₂₀ ₂₇₂₁ ₃₀₂₃ ₃₃₇₂ (vili) ITo Waves ₂₂₃₄ ₂₄₄₀ ₂₆₇₀

₂₃₆

(y) Wave Resistance ₃₈₆ ₂₈₁ ₃₅₃ ₄₃₆

77A

_{Lon: 1Taves} _361B ₃₅₇₇

3702 3992 4145 _(III)

No ïaves 2500 2633 2732 3010 _(II)

Wave Resistance ₁₀₇₇ ₁₀₆₄ ₁₂₁₀ ₁₁₃₅

Short ;7aves 3150 3189 3132 3370 3606 (iii)

No Waves ₂₅₀₀ ₂₆₃₃ ₂₇₀₂ 3010 (II) Wave Resistance 639 494 8 96

77C

_{Long waves} ₃₃₅₆ ₃₄₅₉ _351]. ₃₅₇₀ 3769 (VI) To Javes ₂₀₉₇ ₂₂₂₀ ₂₃₅₈ ₂₅₃₅ ₂₇₈₇ (iii) Wave Resistance 1259 1239 1153 1035 982

Short .raves 2580 2699 2933 3092 3308 (vi)

No waves 2097 2220 2353 2535 2737 (iii)

(36)

(37)

47 -.

Balance of RAIfl3OT

Tabulated balance data

Fig. 25

Balance layouts

_{Fig. 26}

In the balance diagrams, the C.E. i

_{taken 32.60 ft. aft of the}

for-ward end of the 84 ft. L.T.L.

_{This firuro results from vTei-hting 85}

_of

the fore triangle at tvrice the mainsail weicht.

_{Vïarnei-'s PAPOOSE tests}

are the basis for this wei-htin, (see Tech.

emo.

o. 16).

The following

ratios are interesting in this connection.

85

Fore Triangle

Total Sal Arca

PAPOOSE

_0.17

JILL

_{o 27}

lUDIAN SCOUT

_0.31

SEVEN SEAS

_0.27

RA III B

_{O 35}

PAUGER

_{O 36}

Recause the unbalance arms detei-raìned with the

_{rudder contre.l}

an-peared to im1y hi'her rudder post torques than

_{were Iovm to exist, a}

rudder post drncmoneter was built, and tests

were made to cletenrinc the

torques reouired -to hold the heLn at the angles

_{required to effect}

Der-fect 'balance.

_{These, and a f eiv measurements of the torques reuired to}

hold the heLm central, are

_{iven in Fig. 25.}

Th

_{original estimate of the torque requIred to effect balance}

_at,

say, 20

heel end speed To. 16 vías

Rudder

Orce =

2.40 x 11400

_{40 x 3.94}

= 730 lbs.

730 ft.-lbs. torque at 1 ft. radius

where

2.4-0 = unbalance arm with board, Fig. 25

114-00

F11 cas O from Fi. 5

40 = asswned arm for rudder couple

0.94 = cos 20°

(38)

48 -The measured torque for th

_{same case (helm angle = L 2.700) is 374 ft.-lbs.}

(Fig. 25), or about 1/2

_{f the original estinate.}

_{This result suests}

that a lare part of the force

_{set up by the rudder is exerted}

_{on the}

dead-wood ahead of lte

Considering the gear ratio of

_{the steering gear,}

_{, and the size of}

the wheel, about 4 ft. diari.,

_{it may be concluded that}

_{none of the measured}

torques shown in FI. 25 involve

_{excessive holdin}

_{forces on the nart of}

the helmmnan.

_{'fhis conclusion removed}

_{ono Question regarding the validity}

to the balances deduced from the

_tests.

Concerning these balances

_{as a whole, It Is interesting to comoare the}

follovring excerpts from

_{corresDondence carried on while the tests were in}

progress, with the data in Fig. 25.

From

_{r. Olin Stephens, October 9, 1936.}

-WWe

_{are anxious to hear anything further in regard to}

your

balance figures.

Rod, Like and Starling all

aTree that RAflTfl0T

carried some weather helm without

_{the centerboard but that the}

ten-dency is to have slightly too much lee helm when the board ìs

low-ered."

From Mr. Olin Stephens, October 12,

_1936.

-"In the first place,

_{RAI1BOW without her board carries}

_a

fairly stronr' weather helm under

_{windward conditions which is}

re-cluced as her soeed increases under

_{reaching conditions, so that she}

is considered very well balanced

_{for reaching except that}

_{on a}

close roach at really high speed

_{I believe she carried a slight lee}

helm.

T1VIith the board down

_{the tendency is to}

_{cariy slightly too}

much lee helm but this is not

_{as strong for windward conditions as}

the weather helm which she

_{carnee under the same conditions with}

the board up.

"VIith working hoadsails

_{and the board dovm I believe that}

she is almost oerfct1'r balanced but with the quadrilateral

_iihs

ordinarily used the lee helm is

_{picked up.}

_{I think you must bear}

in mind this fact, that

_{a change in size of the headsail used}

_vri11

(39)

n 49 n

-alway-s alter the balance.

_{Lare quadrilateral or}

_{enoa jibs willi}

always move the C.2. forward thus increasing

_{ay tendency toward}

leo helm.

Rod rnows PÄPBOT'S balance

_{venT well and if you have}

any particular nuostions you could Drobably get an answer by

call-Ing him on the 'uhone.

'I think that :'ou are probably riTht in ju'iring that the

C.E. for RPJIIOT has been taken too far ionrard.

PerhaDs the

weighting of the fore trianle at 1.7 tines

_{its actual area maY}

very well bring this about and if this is the case in general it

will show up more in these boats which

_{carry a relatively largo}

fore triangle.

"I think we should also remember

_{that in comnaring the}

imbalance arms in thesc bir boats

_{we are necessarily dealins in}

large nunhers.

_{A comnarison vrith any of the smaller boats such}

_as

the

sixesTT or 40 ft. waterline

_{cruising boats mibt be easier if'}

the imbalance arms were divided in all casos by the waterline

length.

FreIn

_{Tre W. Starling Burgess, October 14, 1936.}

Your letter of the 13th interests

me very much indeed.

The large lateral force that

_{appears to be exerted with a}

comoara-tively small rudder torniie is undoubtedly owing to thc building up

of pressure on the deadwood well ahead of

_{the rudder itself.}

The

three dimensional models of forces of

_{this nature as most}

care-fully measured on dirigible rudders and skags

show an enormous

peal: ahead of the rudder and forces rapidly

_{falling aray on the}

rudder itself.

agree entirely that your balance diagrams are

consis-tent with observations aboard ship."

(40)

.. 52

-16. Preliinar 3alariee of 77-C

Tabulated balance

data Fis. 25

(80e

par. is)

3a1nee layouts Fig. 27

The data and charts considered in this pararaph _{cover the sarre cases}

as those for RAITBOW, with rudder central, in par. 15. The model of 77-C

'as not fitted 'b'rith adjustable rudder.

With the C.E. 36.92 ft. aft of Sta. O, 'the

_unbalance

_arms

- with

the

_{centerboard are lee-acting, as for RAflTBOW, and}

have appreciably smaller marnitudes.

- without centerboard all of thn are veather-acting, arid have eneraliy larger magnitude5 than those of RAIllBG'T.

(41)

Nol1CsN0ER) 2Ot1ti Nolkt FEACMlt.1G ALAN(.I LA',out

3U2.l

5pMo Wor. A,.. 21 12.11 1.15 CAcl'1n Xfl(a)

: ws

L[ ,, ', tJjt.92 - i-i...._._.__

-Lor,a,C.L.ft5l.7LWL No.ÎÎC ÇJ'1GEt) O-it. NooRo

REACtING I3ALAPCE LAQ.,1

&.c O.2I SeNo. tÇNOr Ut0AHM5 8 9.249 W 840' 25 11.16 W508 C*a ('Io fl (a) 549LWt. r' lt 4)Af)%L.W.L. (ie W840'-I25) W,50Ô'

C.t.Ar.o;A05t9a

-2

I-z :JO'1EcLWTH OAItL) _{Ho.1 IC FrEi)}

3At,Nc.1. LA'UU F &Al.t 0?' S,N0. t(r.oîs Ut.l,t,_APMb l 24q Ll.54 21 (019 L460 LCLR41267.LWL, LONG.C.L.R. 4.SO7.UtLL.

i-.'

h

:2O'tEELWIm oftw BALANCE LANOUT -5t..t 02-'l' :5rNo. Kwors UNe.AL.AR.-n ) Ç)41 L 2.82' -ô 4ô0 L 0.66' 20 0.02 L I. G.-'-c.I'lo. No.77C çg'(

O'H Et L WITH X)Att D

eLANcL LAYOUT 02')' SeNo NNOT Un.ARM II 8560 LIôO 14 11)) L020' G'a,.t'Io. C.E.Art or STA. "0" (viz) L2.ö2 ('16) L0.86' (20) L ISO' C EAr! o 5g.., 'D S(92' CE Art or SA'O" 36.92' (n) L 1.60, (4) 1.2. 1 G.C.LU. 456.SZL.W.L Io,.0 CLR. 47.WX L.W.L. Lc.C.?.41.60ZL.W.L. --Lo,.O.C.L.R 44.SO/.LW,L. Lo. C.L.i. 45.607. L)N.L.

(42)

54

-r

PART III

(43)

_ 56

-17. F'1 Palarices of 77-C.

Effect of Cerx.terboards. Tabulated balance data

Close-hauled speeds

Reaching speeds

B1ence layouts

Fig. 23 Fig. 29

Close-hauled speeds FIg. 30

Reaching speeds Fig. 31

To si!rnlify the fine.]. analyses of the balance of this boat, the follow-Ing ccrabinations of speed and heel angle were selected as typical,

and it 'as asstrnied that balance

should be

effected, as far as possible, without he1n angles.

The follovrinz excerpt is fron a letter fron Mr. Olin Stephenz, dated October 12, 1936.

In reard

to the C Desin, the C.L.R.

moves over a

longer fore en-! aft ran:e than inthe case of RAIIIBO7T. VTe must not for-et reaching conditions and I think that a cood wa:,r of

lccatin' the board

7ould

be to first put the rig at the best

possible point for

balance

under reaching

conditions

without

the board ani then to nut the board where it

Trill

properly

cor-rect the balance

for windward work. I think our next desim ith a lower stern than 77-fl mar have a still longer range of

n

C.L.P, positions.

Fron the point of ew of reachin, without centerboards, the most

outstanding differences between the balances of PÄIN2O and. 77-C, in

R-3

O So. Ho. Knots

Close-hauled 100 14 7.711 200 ₁₈ _9.249 300 10.02 Reaching 100 ₁₈ _9.249 200 ₂₃ _11.16 30 ₂₅ 11.94