Model tests of a stepped planing boat with an adjustable ster stabilizer

:1 H 'N

NAVAL SHIP RESEARCH AND.DEVELOPMENT CENTER

Washington, D.C. 20007

MODEL TESTS OF A STEPPED PLA1'TDG BQA.T

u.s. i1

L 4, 0 p4 r.

I

:'

WITif AN LDIJUSTA.BLE STERN ST&BTT.T1

I

I

by

Eugene P. Clement

!DROMECHANICS LABORM'ORY

RESEARCH AIW DEVXEZOPNXrTT REPORT

This doci.uaent has been approved, for public release and sale; its distribution is unlimited.

MODEL TESTS OF A STEPPED PLANING BOAT.

WITH AN ADJUSTABLE STERN STABILI ZER

by

Eugene P. Clement

HYD ROME CHANIC S LABORATORY

RESEARCH ANI) DEVELOPMENT REPORT

This document has been approved for public release and. sale; its

distribution is unlimited.

II

TABLE OF CONTENTS

Page

ABSTRACT 1

INTRODUCTION 2

THE PLUM-TYPE STABILIZER 3

TEST PROCEDURE 5

RESISTANCE AND ANGLE OF ATTACK OF 5

THE VARIOUS CONFIGURATIONS

WETTED LENGTHS AND WETTED AREAS 12

CONVERSION OF MODEL RESISTANCE TO 15

FULL SCALE

LCG LOCATIONS AND WEIGHT CARRIED 16

BY STABILIZER

DESIGN DATA SHEET 16

LIST OF FIGURES

Figure 1 - The Plum Stabilizer and Actuating Mechanism Figure 2 - Lines of Model 4124

Figure 3 - Plans of Afterbodies of Models 4l24A, 4124B, 4124C, and 4124D

Figure 4 - Resistance of Model 4124A at a Weight of 142.6 Pounds before and after Adding Spray Strips to the Afterbody

Figure 5 - Resistance and Angle of Attack of Model 4l24A

Figure 6 - Effects on Resistance of Model 4l24A of Varying the

LCG Location

Figure 7 - Effects on Resistance of Changing the Weight of

Model 4124A.

Figure 8 - Effects on Resistance of Changing the Depth of the

Figure 9 - Views of Model 4124C

Figure 10- Effects on the Performance of Model 4124C of Extending the 1/8-Inch Square Forebody Spray Strips from 1 Foot Forward of the Step Back to the Step

Figure 11- Comparison of the performances of Models 4124B and 4124C.

Figure 12- Effects of Various Spray Strip ConfIgurations on the

Performance Cf Model 4l24C

Figure 13- Effect of the Final Spray Stip Configuration on the

performance of Model 4124C

Figure 14- Effect of Different LCG Locations on the Performance

of Model 4124C

Figure 15- Comparison of the performances of Models 4124C and

41 24D

Figure 16- Effects on performance of Rounding the Afterbody Bottom

and of, Adding a Wedge to the Aft Step

Figure 17- Wetted Lengths for Model 4124C, Test 22

Figure 18- Half-Girths of Forebody Bottom, Model 4124C

Figure 19- Wetted Area of Forebody Bottom Back to Step, Model

4124C

Figure 20- Half-GirthS of Afterbody Bottom, Model 4l24C

Figure 21- Wetted Area of Afterbody Bott9m Back to Trailing

Edge of Stabilizer, Model 4124C

Figure 22- Wetted Length.s and Wetted Areas during a Representative Run

Figure 23- Comparison of Résistance for the Stepped Design and an

Effthient Stepless Design

Figure 24- LCG Locations for a Number of Tests

Figure 25- Weight Carried by the Stabilizer for Some Representative Runs

Figure 26- Design Data Sheet for Model 4124C (Test 22).

LIST OF TABLES

Table 1 - Suuunary of Tests

NOTATION

A Projected bottom area, excluding area of external spray strips

(area bounded by chines and transom in plan view)

B Beam or breadth over chines., excluding external spray strips

BPA Mean breadth over chines,

BPT Breadth over chines at traüsom

Bpx Maximum breadth over chines, excluding external spray strips

B.L. Baseline

Cf Coefficient of frictional resistance

EHP Effective horsepower

Froude .numbe based on volume, in any consistent units.,

vlJgv

1/3

g Acceleration due to gravit.y

L Overall length of the area Ameasured parallel to the baseline

LCG Longitudinal location of center of graity

R Total resistance in pounds

S Area of wetted surface (the actual wetted surface. underway

including the wetted bottom area of external spray strips; however, the area wetted by spray is excluded)

v Speed in feet per second

V

Speed in knots

w Weight density of water (weight per unit volume)

Solid-water vetted length of forebody chine, measured from step, in feet

WLK Wetted length of forebody keel, measured from step, in feet

Intersection of forebody chine with spray, measured from step., in feet

Angle with horizontal of tangent to straight. portion of

fore-body keel, in degrees

Deadrise angle of planing bottom in degrees; this angle is obtained by approximating each body plan section by a straight

line

X Linear ratio, ship to model

Displacement at rest, weight of

p Mass density of water

V

Displacement at rest, volume of

Subscripts ab Afterbody fb Forebody 0 Zero speed

m

Model s Ship

ABSTRACT

The Naval Ship Research and Development Center is developing a

stepped hull having an adjustable planing stabilizer at the stern for

balance, stability, and control of trim. At high speed, this craft

planes on a small area forward of the step (which is located approx

itnately at midlength), with the stern supported by the adjustable

stabilizer. Since the afterbody wetted area is eliminated at high

speed, the frictional resistance, and accordingly the total drag also

are considerably lower than for the conventional planing boat.

Further-more, at high speed the trim angle of the main forebody planing surface

can be adjusted to the value for minimum drag by adjusting the vertical

position of the stabilizer. This report gives the results of tests of

several variations of the first model of this type of craft which was

designed and extensively tested at the Center. The effects on

perform-ance are shown of changes in the following: spray strip configuration,

INTRODUCTION

For a number of years the Naval Ship Research and Development

Center has been working on the development of a stepped planing boat

with an adjustable planing stabilizer at the stern. The main step

the craft is located at approximately midlength. The stabilizer,

which is utilized for balance, stability and control of trim, is of

the type devised by Mr. John plum of the Center staff. At high speed,

this craft planes on a small area forward of the step, with the stern

supported by the adjustable stabilizer. Since the afterbody wetted

area is eliminated at high speed, the frictional resistance and,

accord-ingly, the total drag are considerably lower than for the conventional

planing boat. Furthermore, at high speed the trim angle of the main

forebody planing surface can be adjusted to the value for minimum drag

by adjusting the vertical position of the stabilizer.

The first model of this type which was designed and extensively

tested at the Center was designated Model 4124. The results of tests

of various modified versions of this model were previously reported by

letter to the Bureau of Ships. The results obtained with the different

variations are reported here to make them more generally available. A

list of the configurations tested, and the test conditions, is given in

Table 1.

-2-THE pLUM-TYPE STABILIZER

The stabilizer and actuating mechanism devised by Mr. Plum are

shown in Figure 1. As can be seen, the stabilizer is connected to a

pneumatic piston (located inside the hull) in such a cày that its

vertical position can be controlled by compressed air. At low speeds,

the stabIlizer is held in a retràëted position close to the hull with

its bottom surface approximately parallel to the line of the afterbody

keel. It is held in this position by a spring inside the cylinder and

below the piston. At high speed, with the stabilizer retracted., the

craft will be planing on an area ahead of the step and on the stabilizer.

However, the trim angle will be tOo high from the viewpoints of

efficien-cy and of pounding in head seas. At this point, accordingly, the

sta-bilizer is lowered by admitting, compressed air to the top of the

cyl-inder. This pushes piston and stäbilizét dowt against the combined

forces of the spring under the piston and the hydrodynamic lift on he

stabilizer. As the stbi1izer moves down, it rotates about a pivot

near its trailing edge in such a direction as to increase Its angle of

attack. When' the stabilizer has been lowered far enough to be free of

the

hull,

it will le against the "foot". The lower surface of the stabilizer will then be approximately parallel to the line of the

fore-body keel. The trim of the craft can. be regulated to the value for

minimum total drag by adjusting the vertical position of the stabilizer.

The reason for the forward tilt' of the axis of the cylinder and

piston is to keep the stabilizer horizontal when the craft rolls. If

the attachment of the stabilizer were such that it assumed a heeled

'attitude when the craft rolled, then there tqOuld be sidewards component

tend to put the craft into a dangerous outwardly heeled turn.

Further-more, the flow Of water over the top of the stabilizer would

substan-tially increase the drag Such unsat:isfactory behavior is obviated,

however, by the suspension method indicated. With this manner of,

attachment, when the craft rolls, the stabilizer will initially begi.:i

to roll in the same direction. The lower side of the stabilizer will

then experience an increase in hydrodynamic drag, which will produce a

rotation of the stabilizer about the piston-cylinder axis. (It can be

seen thit the ball bearing inside the piston permits a free rotation

of piston rod and stabilizer about the piston-cylinder axis.) This

rotation about a forwardly titled axis will also produce a roll angle

change in the attitude of the stabilizer, the direction of which will

be opposite to the direction of roll of the hull. Accordingly, the

stabilizer will tend to remain horizontal, and the detrimental effects

TEST PROCEDURE

The basic model (4124) and several variations were tested using

the following general procedure. A curve of minimum resistance was

established over a range of model speeds up to approximately 23 knots

(67 knots full scale). At model speeds up to approximately 10 knots,

minimum resistance was obtained with the stabilizer in the retracted

position. As speed was increased beyond this point, minimum resistance

was obtained with successively lower positions of the stabilizer. At

the highest model speeds, minimum resistance was obtained with the

stabilizer lowered about 1.3 in. (corresponding to 11 in. on the

full-size boat-). A sufficient number of stabilizer positions was tested at

high speeds to define the curves of minimum resistance.

RESISTANCE AND ANGLE OF ATTACK OF THE VARIOUS CONFIGURATIONS

MODEL 4124

The hull and stabilizer were built to represent a 78-ft, 100,000-lb

boat to a linear ratio of 8.5. The form of the model as originally

constructed is shown in Figure 2. The depth of the step in the original

configuration was 1/16 in. It can be seen that the step was formed by

the addition of a 1/16- by 2-in, wedge to the hull bottom. Tests

indi-cated a large hump in the drag curve at intermediate speeds for this

hull configuration. Several successive changes were made in an attempt

to improve this condition.

MODEL 4124A

The bottom of the stern extension was made parallel to the

after-body keel, and the model was designated 4124A; see Figure 3 for the body

-5-plan of the afterbody. Spray strips (1/8 in. sq.) were installed on the

forebody, and two 9/32_in._diaeter air ducts were installed; these led

from inside the hull to the face of the after step. These mDdifications

proved effective in reducing the drag hump. Later, the addition ot

1/8

in. sq spray strips to the afterbody also proved beneficial. Figure

4 shows the resistance of the model at a weight of

lLi.2.6 lb,

(corres-ponding to a full-scale weight of 93,000 ib) before and after addition

of the afterbody spray strips. (The tails on some of the symbols

in-dicate test points for which the stabilizer was in the retracted

posi-tion.)

Resistance and angle of attack (o'.) of model 14l24A at a displacement

of

158.5

lb are shown in Figure

5.

Figure 6 shows the effects on the

resistance of Model 4.l24 of positioning the LOG at various fore-and-aft

locations. The forward position of the LCG corresponds to an initialcK

of 0 deg and the aft position to an initial OC of +1 deg. Note that

mov-ing the LCG forward caused a slight increase in resistance at model speeds.

up to 9 Imots but that the effects on resist.nce of either a forward or

an aft location were negligible at higher speeds.

Figure 7 shows the resistance of Model L.12A at displacements of

lL.2.6,

158.5,

and l7LI..)4. lb (corresponing to full-scale weights of

90,000, 100,000, and 110,000 ib). In each case, the initialc was +0.5

deg. Except for the region from 10 to li-i. knots, increasing model weight

from 158.5. to l7-.4 lb did not decrease planing efficiency (ratio of

load to resistance). Moreover, the model was satisfactorily stable

MODEL -i.12+B

The depth of the main step was decreased from 1/16 to 1/32 in. and

the model was designated LI12L.B. Resistance of the model with the two

different step depths is shDwn in Figure

8.

The resistance was less with

the 1/32-in, step up to a speed of 12 1/2 knots, and slightly greater at

higher speeds. Figure

8

also shows the resistance obtained when Model

was tested at speeds up to 16 knots with the stabilizer retracted.

MODEL 12+C

The model was designated 14l2C after hard chines were added to the

afterbody and the stern extension sections were rounded so that the rear

step extended some distance up the sides. At the same time, also, the

1/32-in, deep step was replaced by a machined metal step of the same

depth. A body plan of the afterbody of Model 4.l24C is shown in Figure

3, and. photographs are shown in Figure

9.

Figure 9b shows the stabilizer

both on shore and underway at high speed. Model -l-124C was initially

equipped with 1/8 in. sq spray strips which extended from the bow to

1 ft forward of the main step. Resistance and trim of the model with the

initial spray strip configuration are shown in Figure 10. The model was

tested up to high speeds with the stabilizer retracted as well as lowered,

and the data are given for both cases. The forebody spray strips of

Model -i-l21#C were next extended back to the step. The resistance and

trim for this case are also shown in Figure 10. It can be seen that this

spray strip change reduced the resistance for all model: speeds above

about ₇ knots. Figure 11 compares the resistances of Models 1l-l24B and

4.l22C.

-7-Figure 12 shows the effects of various spray strip configurations

on resistance in the hump region. For Test 15, there were 1/8 in. sq

spray strips on the forebody only, from bo to main step. It appeared

that spray strips of such square cross section which extended right up

to the main step would result in the formation of spray at the outer

ends of the step which would wet the afterbody and also tend to seal off

the flow of ventilating air. Therefore, before Test 17, the forebody

spray strips were cut off so that they ended 1 5/16 in. forward of the

step. At the same time,

1/8

in. sq spray strips were added to the

after-body, extending forward from the aft step to within 1/2 in. of the main

step. The resistance was measured for this configuration at the lower

speeds where the afterbody was in ontact with the water.

The afterbody spray strips were then shortened so that they extended

forward from the aft step to a point 10 in. aft of the main step. This

was the configuration for Test

18.

Since the resistance was essentially

the same for Tests 17 and

18,

only the results for Test

18

are included

in Figure 12. A comparison of the results for Tests 15 and 18 in Figure

12 shows that the first spray strip changes (removing the forebody spray

strips in the immediate vicinity of the step and adding 1/8 in. sq spray

strips to the afterbody) reduced the resistance humps.

Next, the

1/8

in.. sq afterbody spray strips were replaced by strips

made of 1/1-i. in. sq material, but with the lower surfaces cut horizontal.

Figure 12 shows that this change (Test

19)

produced a further reduction

in the low speed drag. Several runs were also made during Test

19

with

chief effect of sealing the vent pipes was to introduce a small drag

hump at a model speed of about 8.5 knots.

Some further alterations were made to the spray strips after

ob-serving the model during Tests 18 and 19. The aft ends of the

fore-body spray strips (located 1 5/16 in. forward of the step) were filed so

that their bottom surfaces formed a continuation of the line of the hull

bottom. This alteration was faired into the original 1/8 in. sq sec

tion 1 3/4 in. forward. The afterbody spray strips were replaced by

1/4 in. sq strips. The square section was maintained from th aft

step forward for a distance of 2.7 ft. The spray 1strips were then

tapered in width from this point to zero width at a point 2.9 ft forward

of the aft step. Figure 13 compares the resistance of Model 4124C with

the rudimentary spray strips (1/8 in. sq spray strips on the forebody

only, bow to step) with the resistance obtained with spray strips

de-veloped as a result of extensive testing and. observation.

Figure 14 shows the performance of Model 4124C. for three different

LCG locations. It can be seen that at high speed change in LCG location

has a negligible effect on resistance. At low speed, the resistance is

lowest with an aft LOG location (this is the opposite of the trend in the

case the conventional planing boat). The data on stabilizer position

(at the top of Figure 15) show that as the LCG is moved aft, the

stabi-lizer position for minimum resistance becomes progressively lower.

MODEL 4l24D

After the tests of Model 4124C, a further modification was made to

the afterbody. The change consisted of rounding the afterbody sections

-9-in the manner -9-indicated -9-in Figure 3. This was done, in effect, by

incorporating a portion of a cone in the middle part of the afterbody.

The apex of the cone is on the centerline at the forward end of: the

afterbody, and the directrix is a circular arc drawn in the plane of

the aft step so that it is tangent at the chines to the previous

straight afterbody bottom section. The boundary of the conical portion

which was incorporated is indicated on the afterbody drawing for Model

4124D (Figure 3) by the short-dashed line. This change increased the

angle of the afterbody keel from 3 1/2 to 4 1/2 deg. In addition, the

original vent holes were plugged and new vent holes 0.2 in. in diameter,

spaced 3 in. on either side of the centerline, were installed in the

face of the after step. The spray strips were left the same as for

Tests 20 through 22 of Model 4124C. The new configuration of the model

was designated 4124D. Figure 15 compares the performance of Models

4124C and 4124D for essentially the same LCG locations. It can be

seen that for the most part, the resistance was the same for the two

configurations but that it was slightly less for Model 4l24D at a

model speed of 14 knots. It is interesting to note for speeds between

12 and 16 knoL:s that the hull form wit-h the rounded afterbody sections

(Model 4124D) required a lower position of the stabilizer for the

optimum trim (luinimum resistance) condit:ion that did Model 4l24C.

Figure 16 compares the performances of Models 4124C and 4124D at

an initial trim of approximately 1 deg by stern. The reduced afterbody

lift caused by rounding the afterbody sections (Model 4124D) has a

noticeablz detrimental effect on drag at this LCG location, in contrast

After Test 24, a wedge 3/32 in. thick by 1 1/2 in. long was added

to the afterbody bottom at the aft step in order to restore the

after-body lifting effect. The results of the test made after this change

(Test 25) are also shown in Figure 16. The drag curve obtained was

the most favorable of those for all the different configurations of

Model 4124.

-11-Scales painted along the keel and chine of the model made it

possible to read the -forebody and afterbody wetted lengths during each

run. The wetted area underway can be determined from these readings

and, subsequently, the appropriate frictional resistance correction can

be made to convert the model resistance values to full scale. As an

example, the wetted lengths from Test 22 of Model 4124C are given in

Figure 17. In the case of the forebody, three different wetted length

readings are distinguishable (the same as in the case of a conventional

stepless planing boat). The forebody wetted length readings for Model

4l24C are given in Figure 17a. Only one wetted length is distinguishable

in the case of the afterbody of this particular stepped hull. The

afterbody keel cannot be seen, and only one wetted length can be

dis-tinguished at the chine. The observed values of afterbody chine wetted

length are given in Figure 17b.

The .wetted area End the mean wetted length of the forebody can be

determined from the data of Figure 17a together with a lines plan of the

hull. The usual practice was followed here in that only the area wetted

by solid water was considered and not the area wetted by spray.

There-fore, only the intersections of the, forebody keel and chine with solid

water (WL. and WLc) are needed in order to determine the significant

values of forebody mean wetted length and forebody wetted area.

Figures 18 and 19 were prepared to determine the forebody wetted

area of Model 4l24C at the various test speeds. The half-girths of the

-12-forebody bottom, which are given in Figure 18, were determined from the

body plan of the Iull. Next, this curve of haLf-girths was integrated

to give the curve of wetted bottom area versus distance forward of the

step which is presented in Figure .19. The two curves, together with the

experimental values of wetted length of forebody keel and chine, provide

the information needed to determine the magnitude of forebody wetted

area. The procedure to follow is to enter the curve of Figure 19 with

the experimental value of chine wetted length in orcer to determine the

magnitude of forebody bottom wetted area aft. of the chine intersection

point. Typical wetted length intersections and the corresponding

com-ponents of bottom wetted area are indicated in the drawing of Figure 22.

These are for the run at 11.93 knots during Test 22 of Model 4l24C.

The triangular-shaped wetted area forward of the chine 'intersection

point equals the product of the half-girth at the chine intersection

point (from Figure 18) tithes the difference between the keel and chine

wetted lengths. The total vetted area of the forebody bottom then equals

the sum of the above two components, and the mean forebody wetted length

for calculation of Reynolds' number equals 1/2 (WL. + WL).

For convenience, the scale on the side of the model for reading the

afterbody wetted length was starte4 at the location of the. af.t step. The

full bottom length of the stabilizer is also wetted at the lower speeds,

however, and therefore it seems reasonable to assume that the afterbody

bottom wetted length 'and wetted area start, in ef feet, at the trailing

edge of the stabilizer. Accordingly., in preparing the graph of afterbody

half-girths versus afterbody length (Figure 20), the trailing edge of the

13-stabilizer was takenas the starting point, and the half-girth values

from the hull body plan were extended by extrapolation to that starting

point. The integrated curve of afterbody bottom wetted area for Model

4124C is given in Figure 21. The length of the wetted portion of the

afterbody bottom is assumed to be equal to the experimentally determined

chine wetted length, and the area then is determined directly from

Figure 21.

It would also be appropriate to include the portion of the sides of

the hull which is wetted in the slower speeds as part of the wetted area

used in making the frictional resistance correction. However, the

readings needed to determine the side wetted areawere not taken during

CONVERSION OF MODEL RESISTANCE TO FULL SCALE

After values of wetted area -and wetted length had been separately

determined for the forebody and the afterbody, the model resistance was

converted to full scale on the basis of the following equaon:

R

= Rm

-

4

(Cf

- Cfsab) + S (Cfmab - Cfsab)l

The resulting full-scale values of resistance for the steped design

are coipared with corresponding values for a representative stepless design

in Figure 23. It can be seen that in the intermediate part of the speed

range, the resistance of the stepped hull is greater than that of the

stepless hull. This difference is at a maximum of Fv equals 2, at which

tie- resistance of the stepped hull is 12 1/2 percent greater than the

resistance of the stepped hull. At the high speed corresponding to Fv

equals 5.2, on the other hand, the stepless hull has 2-7 percent more

resistance than the stepped hull.

LCG LOCATIONS AND WEIGHT CARRIED BY STABILIZER

Figure 24 gives LCG locations for a number of tests. The air

pressure required to lower the stabilizer was also recorded for a

number of runs. In addition, calibrations were made

(on shore) of

the air pressure required to lower piston and stabilizer against

the

force of the spring under the piston. From this information,

it was

possible to determine the net air pressure required to balance the

hydrodynamic lift on the stabilizer, and then the stabilizer lift in

pounds. Representative values of the stabilizer lift are

given in

Figure 25 as a percentage of the total lift (or weight). It can be

seen that for the middle displacement, at a representative high speed,

the stabilizer carries 12 percent of the total craft weight.

The

trend of the data also indicates that the percentage carried by the

stabilizer increases with increase in craft weight.

DESIGN DATA SHEET

A complete design data sheet for Test

22 of Model 4124C is

TABLE 1

SUMMPRY OF TESTS

Bottom of stabilizer makes angle of -3.5° with forebody keel when retracted except where noted

Remarks Stern ext. parallel to forebody keel Stern ext. parallel to afterbody keel Spring installed in cylinder,.air ducts to stern ext. step Up stab. angle as -.6 deg and -3.5 deg Model No. Test No. Model Weight lb. O( 0 deg

-i-0 0 0 1.11. 1.11. 0.5 0.5 0.5 Stabilizer Angle When Down, deg.

Spray Strips Max. Test

Speed, knots

Tail Above LCG, Line A.B. Percent L Keel in Up Forward o Position, Step Forebody Afterbody 11.1211. 141214A 14l24A I1.1214A Itl2ltA 14121LA 141211.A 141214A 1 2 3 3A 11. 5 6 7 158.5 1214.25 111.2.6 111.2.6 111.2.6 111.2.6 111.2.6 111.2.6 None IT 1/8" squre bow to step It None H 11 TI

From aft step 1.7 ft fwd 15 15 17 111. 17 17 20 214 3.5 3.5 14.5 14.5 2.5 2.5 2.5 0.11 in. 7.3 Slightly Above 0.15 0.15 0.12 0.12 0.3 0.3

TPBLE 1 (Continued)

Model Test Model Stabilizer Spray Strips Max. Test Tail Above LCG,

No. NO. Weight

de Angle When

Speed, Line A.B. Percent

g.

Dawn, Forebody Afterbody knots Keel in Up Forward of

deg. Position, Step

in. tl2C 15

158.5

0.5

p.6

bow to step 23 L12LC

i6

I7+.5

0.5

o.6 " 20 l214C 17

158.5

05

/8"

bow to

1/8"

aft step 12 0.3k

1 5/16"

to 1/2" aft fwd main step main step

Remarks Large stabilizer Small stêp_i/32!' Nachined 1/32" step,rear step extended up sides, stern

sect ions rounded,

hard chines added.. to afterbody 4i21IA 8

158.5

.O:5 0.1k 23 0.31 5 L12ItA 9

158,5

0. 0. 23 0.31 " ₂₃ 0.31

I2A 10

I7J

0.5 22 0.19

4l2A 11

158.5

0.5

0 and

l7it

1 22 0.31 3 1l2I.A 12

158.5

1.0 0.

a2B 13

158.5

0.5

O.1 23 0.4l Lt.6

1l2C

1)4

158.5

0.5

o.6

1/8"

bow to I' fwd step 23

Model Test Model O( Stabilizer Spray Strips

0

No. No. Weight

cieg Angle When

lb. Down, Forebody Afterbody

deg.

Table 1 (Concluded)

H

Mar. Test Tail Above LCG,

Speed, Line A.B. Percent Knots Keel in Up Forward o'

Position, Step in.

Remarks

Tests 23-25, afterbod.y bottom rounded, original vent holes plugged, new holes

(0.2?? in dia.), 3?? on each side

wedge at aft step 14I2LC 20 158.5 0.3 22 6.8 1121iC 21 158.5 -0.1 22 8.6 1l21C 22 158.5 0.8 22 14.5

of centerline. Forebody and afterbody spray strips the same as for Tests 20-22.

Ia21LD 23 158.5 0.5 16

14l24D 214 _158.5 1.0

i6

Iji21W 25 158.5 1.0 16

3/32" by 1 1/2"

1i1211C 19 158.5 0.3

fr _{i/14u bottom 17} Some runs with

horizontal air ducts closed

Tests 20-22,, forebody spray strips filed from at aft end to original section 1 3/14" d. 1/14" square afterbody spray strips - aft step to 2;7' fwd - tapered to 2.9' fwd..

Model Scale ir Inches

IiiiiiiiiiJ I I I I 1

411 .JOinS !lver - SolIcrr

a C 0 a' Brass Plate j6rass Plates

Channel Made of ' Brass Plate

Figure Ia - The Stabilizer

Figure I - The Plum Stabilizer

_{and Actuating Mechanism}

0

+ ¶

\

Model Scale in Inches

0

I 2 3 4 5

lii

I I I

-Cornpressed ir

Foot

Stabilizer in Lowered (High- speed) Position

--This Line is 'drffliel

to the HJII bhIiñc

Figure lb - Stabilizer Attached to

Actuating Mehcnism

Plan VieW

5.64"

Sta. Spacing li.29-' 14.12"

Keel

TMB Model No. 4124 Model Scale In Inches

I I I I I

0 I 12

Enlarged, Step Profile

i/i "282"

-Keel 8

5

Main Step (at 49% L)

Lp 9.14' 2 '2

-B

0 C E 3.2" 0.76"

4124C

Model Scale In Inche.

o

I 23456789101112

I I i i I i I i I I I I I 23 4124A & 4124B 8 4124D

3 2 2 4 0 "0

H:

o Symbol

000

o

Test 5 6 No. a0 0.5° 0.50 Afterbody Spray None

From art step

forward 1.7 Strips feet A - -16 18 20 22 24

24 8 4 6 a Resi stance

Figure 5- ResIstance and Angle of Attack of Model 4124A

Weight of nodel = 158.5 1b,a= 0.5 deg,

i8

20 22 24

8 10 12 14

Model Speed, knots

28 12 8 0 6 8

A

bol

-0--V

Tost N 9 8 12

0.

0.

a0

00

1.0 50 LCG, f wd % L of step 8 .5 3 2 4 10 12 14

i6

Model Speed, knots

'4 3 32 2 0 '4

Full Size Speed, knots

10 15 20 25 30 35 40

uI..

___.__1lI__..

uI ____u

__

' Ull

.

U

UI.

.

N

___iliIi

NI__lUlL

uiiuui

___Iluuilinhl

___UIVFAU

uuruuu__

UUVA__U__UI

I U

___.._

Model

I....__U...

_UUUUUU

4124A 142 6 Full Size 90,000

sbol

Test No.

6 and 7

liii

_.

2 4 6 10 12 14 20 22 24

Model Speed, knots

Figure 7 - Effects on Resistance of Changing the Weight or Model 4124A

a)

d 12

0 8 4 cted

/

/

1 Stabilizer Retra

Symbol Model No. Test No. Step Depth

--

4124A 8

1/16

in.

0

4124B

13

1/32

in.

0

2 N) OD a) ai -4 U) a)

320

28

24

l6

10

4 8

10

12

14

16 18

20

Full Size Speed, knots

15

20

25

30

35

40

45

50

55

60

65

70

.o 1% 1.4 1.2

,-..

1L tk4 _.2

tJj

I

H

(

p.

T

-/

(Top side of sabi1izer tip is painted white)

Figure 9b - Stern or Model on Shore and

Underway

p

32 24 20 4 0

/

r4 C-' 0 0 ) Symbol rest,:N 14 15

0-Forebody Spray Strips

Bow to 1 root forward maln step

Bow. to main step

6 8 1,0 12 14 16 18 20 22

Model Speed, knots

Figure 10 - Effects on. the Performance of Model 4124C or Extending the 1/8-Inch Square Forebody Spray Strips from 1 Foot Forward or the Step Back to the Step

8

6

0

24

3 2 2 a)

d 12

0

8

4

0 A.

H.

Symbol Model

4l24B

4124C

No. Test 13 15 No.

0

2 4 6 8

10

12

14

16 1R 2(1

28

24

20

8 4

0

± **

Symbol

Test No.

Vent Pipes

15

Open

0

18

Open

19

Open

19

_Closed

33

4

6 8

10

12

14

16

Model Speed, knots

Figure 12 - Etfects or Various Spray Strip Conriguratlons

on the Performance of Model 41240

D2

rl

1

UI'.

/A

I

/

SYmbol

0

Test No. 15 20 22 6 0

6,81

45J

ep Spray Strips Forebody only, bow to step See text / / / /

0

A

A 0 2 10 12 14 1 22

32 28 24 '-! 20 U) C) aJ '.. 16 U) U) r1 12 8 4 Symbol Test No. a, LCG, % Lp LCG., % Lp twd

fud or -step or transom

o o 0

000

57.6

55.8

53.5

O 0 0 t1 00

0.

0 0.2 0.4 0.6

0.8

1.0

1.2 1.4 8 6 2 0 22 21 0.l°

8.6

20 0.3' 6.8 22 0.8' 4.5 18 14 16 20 2 4 6 8 10 12

Model Speed, knots

FIgure 14 - Effects of Different LCG Locations on the

28 4 16 12 2 4 6 8 10 12 14 16 18 20 22 24

Model Speed, knots

Figure 15 - Comparison or the Performances or Models 4124C

and 4l24D Weight of model = 158.5 lb. 0,2 0.4 0.6 0.8 1.0 1.2 1.4 0

32 28 24 20 16 12 8 4 0

10

12

14

Model Speed, knots

Plgure 16 - Effects on Performance of Rounding the Arterbody Bottom

and of Adding a Wedge to the Aft Step

8 6 .i hi U p 0 Symbol Model 4124C 4124D 4124Dt No Test No. 22 24 25 0.8° 1.0° 1.0° a j J 0 '.) 0

00

D 0 0

* 3132 Afterbody in.

bottom rounded (see Figure

by 1 1/2 in. wedge at aft step

3)

iii

liii

0 0 a B U

In. I_I

VAURIV

0

4111

16 18 20 22 0.2 0.4 0.6 0.8 1.0 1.2 1.4

1

0

-\ Li N

0

C

0

C

Lsp

2 18

20

22

14

16 4 6 8

10

12

Model Speed, knots

Figure 17a - Wetted Lengths or Forebody

..u...

...

IUIII1IIIIIIIHIIIIIIHhIIIIIHHIHHIIIU H

IHIIIIIIIIIIIIIIIIIIIIIHIIIIHIIIIIIUIIIH

_H

IIIII!IIIrnIImIImmHhIrnHrUu.

uu...

I I

IIIIIHIHHHIHHHIIHHHII!IIIIIII1UIII1UI

R..U....IUU....U...rU. WR...U..

IIIHIOIIIIHIIIIIIIHIPJJIIiIIUIIHIOIIIHUIj

...

...

OIIHOHHHHHHII!HUIIIIIIIIIIIIIIII1FU

IIIIIHHHHHHI!IIHIUIHIIHHIIHIIIIIHIIIU

uiiuiiiiiiniiiiuiiigrnuuiiiuiiuuiiiiiinuiui

....uuu.ua

UUUU.R

...

U r4

0

'.J

;o

2p

mo.z;

st4u9'j PGO,9M

39

c'z (-4

1.2

1.0

0.6

E

0

4-) 4-,

0

0.4

0.2

0 0 1 2 3

Distance Forward of Step, ft

0

/

0

1

2

3

4

5

Distance Forward of Step,'ft

Figure 19 - Wetted Area or Forebody

Bottom Back to Step,

Model 4124C

8

1.0

4., '4-I

0.8

E

0.6

0

4., 4-,

0

0.-0 1

2

3

4

5

Distance Forward of Trailing Edge of Stabilizer, ft

Figure 21 - Wetted Area of Afterbody B3ttom Back to

Trailing Edge of Stabilizer, Model4l24C

0.

₁

₂

₃

₄

₅

Distance Forward of Trailing Edge of Stabilizer, ft

Figure 20 - Half-Girths of Afterbody Bottom, Model

4124C

Test 22

Speed: ii .93 knots

Percent Lp 0 6O

iO

BO 9O I?O Lp 9.I4'

MODEL 4124C _{Model Scale In}

Inches

0 2 4 6 0

10 12 14 16 lB 2022 24

Figure

22

-Wetted Lengths and -Wetted Areas during a Representative Run

0 20 0.18 0.16 0.14 0.12 0.10 0,. 08 0.06 0.04 0.02 0 / / / / / /

/

/

/

-'VI

Design Model No Lp/Bp Ap/V218 Test No Symbol

Stepless 4667-1 4.09 7.00 1

Stepped 4124C 4.57 22

Resistance corrected to 100,000 lb displacement and salt water at 59F, using 1947 A.T.T.C. Model-Ship Correlation Line with zero ronghness allowance.

/

10

00

2

0

Model Number

o

4124

4124A and 4124B

4]24C

_10

-4

-2

0

10

LCG, fh L

forward of Step

Figure 24 - LCG Locations for a Number of the Tests

Weight of model

158.5 lb.

12

14

8

4-.1 a)

0

a)

0

a)

20

16

Model Speed, knots

10 Test

0

0

Displacement, Full 90,000 100,000 110,000 lb size

5

16

17

18

-

19

2fl

21

l0

Kei

Stern Extension

8.q

Enlarged Step Profile

J_i!0uH

_{Keel and}

i__s 5 41/2

Main Ste,ot 49 % Lp

]

9 heir

Rear Step

F i4.i2

Lp '9.l4'

TMB MODEL No. 4124C

Model Scale in inches

O 2

4 6

8 10

12

I I I I I I I I

O b- U4

_{82 84 86 88}

O.76

Sheer

Figure 26a - Lines or Model 4124C

5.64"

-Sta. Sping li.29

F

0 C

MODEL PARTICULARS, TEST CONDITIONS, AND RESULTS

Boat. xoerirnenta1 Steoned

Design Model Number 4124C

Appendages Plum Stabilizer and Spray Stripe

Remarks: Model was towed in the shaft line shown in the profile drawing.

Planing Bottom Dimensions

and Coefficients 9.14 ft 2.00 ft 1.35 t 12.29

ft

Lp Bpx Bp4 Ap/V2'3 6.59 Lp/V"3 6.69 LP/BPA 6 .80 W,lb 158.5

Laboratory DTMB . _{Water Temperature}

Basin High-speed! Specific Weight 62.3 it)/rt ...

Basin Size 2698'X21'X(10'416 Model Material Wood -

-Model Length 10 ft_ Model Finish Paint

Test 22 Date 21 Mar 950 Turbulence Stimul NO?1

LCG location2 .07'orward of Station....5..

(LCG location

4.50

percent L

fwd of step)

Model Test Results

LWL Dimensions and Coefficients L B H L /B L/ V '3 CB CP CW

Model Test Condition

0.8° x stern 0.8°

20.90 25.65 1.9

O.If 1.1

_{---l2oL12 L_Lz.04J..5.33.}

V, knots Rt, lb

Solid water wetted Spray at Chine fwd step, ft Sfb, t2 wetted length,ft rear step Sob,ft2 Stabilizer down, Chage trim, deg CG rise, Fv Keel Chine 2.00 0.9 4.7 --- -- --- --

5.10

_{0 0}

-'3..

. "

3.00 3.1 4.8 3.0 -- 7.55 --- 5.10 0 -0.05 -:j n.' 3.99 7.25 5.0 --

7.Q

---

5.10 0 0.10

-0.41

1.fl'

4.99 12.00 4.7 --- 4.7 --- s ic 0 1.75 -.n.4n 1 5.96 15.85 4.6 --- 4.6 7.55 --- 5.10 0 2.75

-0.1

1

F'

6.95 18.5 4.3 3.1 4.4 7.15 3.0

4.fl

0 3.25 0 7.95 21.1 4.0 2.6 4.1 6.30 2.4 3.70 0 3.85 0.41

2.3?

8.95 21.5 3.4 2;0 3.6 5.15 2.1 3.25 0 5.00

0.R5

2P 9.96 22.0 2.9 1.6 3.0

----...--.-

1.7 Q_ I -0 5 60 : 2 54 C . I ., 10.94 22.6 2.9 1.4 2.9 .

0 UI

11.93 23.15 2.8 1.3 2.7 I I . I 4.95 1.71 3.04 12.92 23.85 2.6 1.05 2.3 5.00

2.10

3.Q

13.97 24.25 2.4 0.9 2.05

!I

.

4.70

2.9

3.F.

14.95 23.4 2.4 0.8 1.8 4.50

2.53

3.l

U

18.91 24.3 2.1 0.3 1.4 . 0.20 1.2 3.75

2.9

4P2

19.92 24.7 2.0 0 2 1.2 I 1.2 3 8 .99 5.08 Fbrebod After bbd

I0 9 8 7 6

V5

4 3 2 0.2 0.I CG Rise 0 -0.1 2

PERFORMANCE CHARACTERISTICS

Figure 26c.

49

5 6 0.20 0.18 0.16 0.14 0.08 0.06 0.04 0.02 0 111111111 lIlIIIH I

ofC

R w

/

/

//

fleslstance corrected displacement usIng 1947 Correlation allowance. Length, displacement and salt A.TT.C. Line with Lp

77.69

to 100,000 water at Model-Ship

zero

roUghness-lb 59°F lb

rt

, for 100,000 2 3 4 5 0 8 0.12 0.10 6 a, deg 4 3 2 0

l60 l40 120 C

I

o. 60 40 20 100 80 60 40 20 Ilirillil liii BPA Mean Buttock 0 10 0

FORM CHARACTERISTICS

20 30 40 50 60 Percent of Lp III 111111 Notation

As far as pOssible,the notation used is consistent withtheSNAIIIE S"Explanatory Notes for Resistance and

Propulsion Data Sheets (Technical and Research Bulletin No 1-13) Exceptions and additions ore listed below The subscript P designates the planing bottom which is the portion of the bottom bounded by the chines and transom.

Ap Projected planing bottom.area,excluding area of external spray strips Bp Beam or breadth over chines, excluding external spray Strips

8PA Meón breadth over chines, Ap/Lp

Bx

Maximum breadth over chines, excluding external spray strips Lp Projected chine length

S Area of wetted surface(The actual wetted surface ónderway including the area of the

sides which is Wetted at low speeds and the wetted bottOm area of external spray strips; however, the area wetted by spray is excluded)

a

Angle of attack of stern portion of planing bottom in degrees

J3 Dead rise angle of planing bottom in degrees. This angle is obtained by approximating each

body plan sectiOn by a straight line

A Displacement at rest, weight of

Trim angle of hull with respect to attitude as drawn in degrees V Displacement at rest, volume of

A subscrlDt Thdicatlng value when hull is at rest in water 0 100 80 -16 70

-14

0 U'.)

-i

0. C --50

-I0

U'

40 .-

8 E 30

-6

_cO.

20 0 I0 2

I

90 80 70 tOO 90 80 70 60 50 40 Percent of L 30 20 10 0

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20 DDC

-UNClASSIFIED

Security Classification

DOCUMENT OI4fROL DATA R&D

(Security classification of title, body of abstract and indexing annotation must be entered when the overall report is classified.)

I. ORIGINATING ACTIVITY (Coorate authorS)

Naval Ship Reseaich and Development Center Washington, D. C. 20007

2a. REPORT SECURITY CLASSIFICATION Unclassifiei

'2b. GROUP

3. REPORT TITLE

Model Tests of a Stepped Planing Boat with an Adjustable Stern Stabilizer

4. DESCRIPTIVE NOTES (Type of reporl and inclusive dates)

-Final

5. AUTHOR(S) (List ñe. fiist name, ihitial)

Eugene P. Clement 6. REPORT DATE

May

1967

7a. TOTAL NO. OF PAGES 57

7b. NO. OF REFS

0

8a. CONTRACT OR GRANT NO.'

b. PROJECT NO. S-F 013 01 13

c. _{Task 11274} .

d.

98. ORTGINATORS REPORT NUMBER(S)

24l4

9b. OTHER REPORT NO(S) (Any other numbers that may be assigned this report)

o. a..VA IL ABILITY/LIMITATION NOTICES

-This document has been approved for public release and sale; its distribution

is unlimited.

II. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY

Naval Ship Systems Command

13. ABSTRACT

The Naval Ship Research and Development Center is developing a stepped hull

hav-ing an adjustable planhav-ing stabilizer at the stern for balance, stability, and

control of trim. At high speed, this craft lanes on a small area forward of the

step (which is located approximately at m.idlength), with the stern supported by

the adjustable stabilizer. Since the afterbod,y wetted area is eliminated at high

speed, the frictional resistance., and accordingly the total drag also are

con-sid.erably lower than for the convent-onal planing boat. Furthermore, at high speed

the trim angle of the main forébody planing surface can be adjusted to the value

for minimum drag by a&justing the vertical position, of the stabilizer. This report

gives the results of tests of several variations of the first model of this type

of craft which was designed and extensively tested at the Center. The effects on

performance are shown of 'changes i±i the following: spray strip configuration, LCG location, weight, step depth, and afterbody shape.

UNCLASSIFIED

Security Classification

14.

KEY WORDS

Stepped planing hulls Planing boats

Trim control for planing boats

Adjustable planing stabil:izer

Spray strips LINK A ROLE WI ROLE LINK B WT LINK C ROLE WI

t ORIGINATING ACTIVITY: Enter the name and address of the contractor, subcontractor, grantee, Department of De-fense activity or other organization (corporate author) issuing

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