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REPORT N. 766

AERODYNAMIC AND HYDRODYNAMIC TESTS OF A

FAMILY OF MODELS OF FLYING!BOAT HULLS

DERIVED FROM A STREAMLINE BODY

NACA MQDEL 84 SERIES

By JOHN B. PARKINSON, ROLAND E. OLSON, EUGENE C DRALEX and ARVO A LUOMA

Langley Memorial Aeronautical Laboratory Langley Field, Va.

ThCt4J48CHE UNIVERSITEIT

SiIT

LUCHNAMT EN REVMMT IBUOThZ

Kluyverweg I 22

MB LPT 1b1itHeet. TU 1111111111 lii EO75SB

Dclft

LR

National Advisory Committee for Aeronautics

Headquai'tei.s bOO .Vew hampshire Avenue NW.. ThaJiingfon .2.5. D. C.

Created by act of Congress approved March :3. 1915. for the supervision und direction of the scientific study of the prob'ems of flight (U. S. Code, tide 40. sec. 241). Its membership was increased to 15 by act approved

March 2. 1920. The members are appointed by the President. and serve as such without conipeusation.

JEROME C. HuNssKs. Sc. D., Cambridge, Mass.. Chairman LYMAN J. BRIGGS. Ph. D.. Vice Ohuirnuin. Director, National

Bureau of Standards.

CHARrEs G. ABI1OT, Sc. D., Vire CI ,ir,iu,n, Exeulive Committee, Secret;i ry, Smithsonian Institution.

HF.NRV H. ARNOLD, General, United States Army, Commanding General Army Air Forces, War Deparrnieiir.

\VIr..uAM A. M. BURDEN. Special Assistant to the Secretary of Commerce.

VANNEriE BUsH. Sc. D.. Director. Office if Sciejìrifi Research

and Development, Washington. D. C.

WIr.LIAM F. DuaiND, Ph. D.. Stanford University. California. Or.IvER P. ECHOLS. Major General, United States Army, Chief of Maintenance. Matériel, and Distribution, Army Air Forces, War Department.

GEORGE W. Lewis. c. D.. Directo, of .1erona,,/icai Research JOHN F. VICTORY, LL.M., Secretary

HENRY J. E. REIn. Sc. D.. Engineer-in-Charge. Langley Memorial Aero,,:,nrii;il Lubirimtory. Langley Field. Va.

SMITF J. DEIRANCE. 13. ri.. Emriimeer.in-Cltarge. Ames Aeronautical Labormltol'y. \lifftt Full. I ;ilif.

titi R. Sui e t', LL.B...\ Em na er. Airera ft Erigi ne Reie, elm Limb rit tory. I leveli md A irji r. Cl evelmi iI. iii io

Cimir..rox KEmpEIm. B. .. Executive Engineer. Aircraft Engine Ilesemrh Lirbormitiry. Cleveland Airport. Cleveland, )hio

TECHNICAL COMMITTEES

AERODYNA HICS AiRCRAFT STRUCTURES

POWER PLANTS Fila AIRCRAFT Om'ERiTINI; PROIILEMS

AIRC'R.FT MATFRIAT.S .1 ET PROPULSION

Coordina lion of If eare'li Needs of Jiilita rif and Ci iii . I vin t ion

P1(1)1110t ion of Research Pro gro uts .4 llocn lion of Problems Pr"r,i lion 0f Duplir'rtiofl

JOHN C. McCiix, Rear Admiral, United States Navy, Deputy Chief of Operations (Air), Navy Department.

GEORGE .1. MEAD, Sc. D., Washington, D. C.

ERNEST M. PACE. Rear Admiral, United States Navy, Special Assistant to Chief of Bureau of Aeronautics, Navy Department.

FRANCISW. REICHELDERFER, Sc. D., Chief, United States Wear hi.'r Bureau.

Enwian WARNER, Sc. D., Civil Aeronautics Board, Washington,

D.C.

ORVILLE WRIGHT, Sc. D., Dayton, Ohio.

THEODORE P. WRIGHT, Sc. D., Assistant Chief, Aircraft Branch, War Production Board.

Laxr.î.i.:m 1,le\IogI.\r.AF.RONAUTICAT. L.\rtoRATORY A.\IES AERONAUTTC.mr, L.\RorìAToiiY

Lmmngley Field, Va. Miffi'rt Field. C 'alit. AiRCRAFT ENGINE RESE.\1rUU J..mRoit.\TORY. Clevela nil Airpoi.t. Cleveland. (Chi,

Conduct. ululer un tfieci COn tru,i. fumi ill Q/d'llli1.S. of sCiemi,tiif rc-se,, reh on tIr e I und,' nr en lit pu'ibluruu i of fi i,1/it

(Thyic ir' AERONAUTICAL TNTEt.ur,ENCR. WnshinGton. D. C.

Collection, class 91ra lion. ruIn pilrttion . Iii rl di.sprn inn t irin of seien lifte rzrut lee/i nicol informal ion 'in ,,nr0,l,l iiI ic-s

AERODYNAMIC AND HYDRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT

HULLS DERIVED FROM A STREAMLINE BODYNACA MODEL 84 SERIES

By JOHN B. PARKINSON. ROLAND E. OLSON. EUGENE C. DRALEY, and ARVO A. LUOMA

SUMMARY

A .erie. ?f r(klte(l for,n. of flying-boat h.u11. representng

za,,zou. (1eçJree Of COÌTl])/()'i ¡e between aerodyn ainic an(l

/tJ/(Iro-(Iyna7nic requiteinenf. wax te.'çted in Langley tank mo. i and in.

ilìe Laìigley S-fwit hjqh-.'])(ed tun.ie.1. The J)?Lt])oÑe of the iflre..9tifJatU)fl WO .' (( J)r()luIc information regarding the ])enaltiex

in wate, »eríwìna.ncc re.ultingfron? further aerodynamic

re7ne-meni a 11(1. a. a coiolia.ry,. to proiu/e information ref/ar(ijIì(/ the

re7?a.f1.ie iM r(lfl(/C (11 _{j)a.i/ /0(1(1 re.1.Jlti?ì.g} the retention ûf

certain (/(.jra.b1( /1J(l,.(ri/fl(1ìfleC Ch(1iaCt.eI?t.iCS. The

informa-t(Iè .'/.Q./(/ fo;ìn ci baxi.fo, (),eì-aI/ ?mn])7(ne.1nen t. / i/I for?n

T/ì.e ,elate(I 1fl(J(/C1.' of flu

... ((

ba..ed ()1 an arbitrary

.tIea.1n1j?l( bol1 qf 7Cl'(,I11t()fl . ?'/LC ra.ia.tu)r in form were

(Ie.eelnpe(1 in .ic/ a wa?/ a. Io NhoW (learly (1« effect of coì-yen/lanai (IepartIJIe. from t/e (/C(ti .'treaIfl/.ifl( bnl.ìj made in the

(le S f/O 01177/jog-boat hvll..

The ?1u/el. 114.S5 U1ell.( long an1 I/u (liamete,' of the

ba.ic .'treainlne form I 592 inc/,e.s. In t/U hydad.yoa.?nic

(ests, TCN?4UVC( and tri in or triln.Ìniiig moments were inea.ured

at ail speeds and loads f interest and the spray patterns were

photographed, In the orrori )/na.nr c tests, lift, drag, and pdch -ng moment wire measured with tra nxitioi ed at 5 percent of

the length. at speeds U to 420 mi/ex per hour, and a.t Reynolds

numbers up to 30000,000.

The results of the in ve.stigatun aie .sw,nrnarezed as follows:

Effect of varyiig height f tow

Increasing the height of the bow bi1 warping the form decreaÑes

the trim and increases the resistance at low speeds. A low bow runs cleaner in smooth water than a high bow of the saine length because of the increased fore-and-aft curcat'u.re of the hqh bow.

Increasing the height I a well-faired bow by warping the form.

has only a small (l.drerse effect on the aerodynamic drag. Effect of varying height q,f stern

Increasing the height of tire stern by warping the basic form.

but holding th.e afterbo'di ])OSltO?,ì ed i lcrea,seÑ resistance and

trim at xjweds below the hump. (lecreaxex the hump speed. aoci

does not affect the value of the m(Uiinu.mn resistance at th.e hump.

A low .9tern runs awash (i/ill requil...s higher position of the

tail sur face. relative to the deck. Increasing the heiqht of the stern hij warping the basic orm but holding the afterbody

posi-tim, ñxe.d h.a.s a large adverse e_ffect on the aerodynamic drag: earying the height I the stern of the ,strea.m,line body alone has

REPORT No. 766

Oc) adce,'se effect on the d,'ag but ii,creases the angle of minimum di'a.g as would be expected.

Effect of increasing angle of (leali rise a.t bow

increasing the angle of (leCl(/ liSe at tite bow by dropping the

keel line reduces only slightly tite resistance at low speeds but results in a large improvement in cleanness nf running. The

modification. is out of the water at the hump speed and for a

well-fairedform. /1115 little or no effect on the aerodynami.c drag. Effect of decreasing angle of dead rise on afterbodij

Deci'easing the angle nf dead iise on the afterbody decreases tite triut at speeds up to and including the hump speed. The

decrease in trim reduce the resistance at. these .sjueed and tends

to increase t.h.e clearance of the tail extension .

Effect of inc,'easi.ng depth of step

Increasing the dept/c of the .'utet by raixin.g tice afteibocly parallel ti) itself has oii.l.j a email effect on. re s ixta,n,ce and. .smi'a.y

at low speeds a,n(l (iec,'ea.ses iesi.stance at p/airing speeds. Too

shallow a step results in a violent 'i,,.stahilit cit big/c s])ee(l.5 that

i most pi'on.ounced when the ofte,'bod?/ keel apnoaches the

iu,ru.zontai. Increasing the dept/i of step fi'omn. 2.5 to 4.4

per-cent of the beam increases the aerodynamic drag only 2 perper-cent. Effect of increasing angle of afterbody keel

Increasing the angle of afterbody keel results in large increases

in trim and resistance at the hump speed. most of the increase

in m'esista.mt.ce. being attributed to the increase in trim: it lowers

tite resistance at planing speeds. A low angle of aft erbody keel results in the cleanest running at low speeds. increasing the angle of afterbody keel increases the trim at which tite violent

instability resulting from too shallow a etc]) will be ei count cred.

Effect of addition of chine fiare

C'hine fiare added exterior to tice straight bottom sections of

the forebody has o'iciy a small effect mt. the resistance and trim

up to amt.d including the hump speed but results in a marked

improvement in cleanness of running. ('hi 'ne fiare added to tite afterbody reduces tice resistance at the hump speed amid slightly incì'eases the resistamcce at planjng speeds.

Effect qf addition. of third planung .sumfa.ce

The addition of a third planing surface om,. the model with. thr

lowest stern, has a negligible eect on the trim and resistance-a remresistance-arkresistance-able result becresistance-ause the ,ster....ectiomis without the planing surface are circular and heavily wetted. The addition

Effect '.f rounded chine.' at bow

Rownding the chines at the bow results in very poor spray characteristics in smooth water and probably would be

ioprac-ticable in rough water. Design charts

The results of general free-to-trim and fixed-trim tests of a

model incorporating the most promising of the forms tested are

presented in theform of design chartsfor estimating static wafer lines and take-off performance. The aerodynamic data, be-cause of the-jr unique character, are presented completely for

use in estimating the effect of the variables investigated on

aerodynamic performance.

It is concluded that the aerodynamic drag of a planing type of hull need not be 'more than 25 percent greater than that of the streamline body from which it is derived. This difference might be reduced by the development of aform of afterbody that has less influence on thefiow than does the conventional pointed

type.

INTRODUCTION

The aerodynamic drag of hulls is an important factor in the design of long-range flying boats, not only because of its effect on speed -but also because of its influence on pay load, which is more important. Because of the long

dis-tance involved in transoceanic routes, the fuel load must be

a large part of the useful load carried. The pay load on

such flights is small and its size is largely dependent on the magnitude of the fuel load, even in cases of the largest craft

now built or contemplated.

Under these conditions of

operation, the weight of the fuel required for power to over-come the drag of the hull is large in terms of pay load. The

further development of the planing type of hull for long-range flying boats, therefore, should he toward forms that combine the lowest possible aerodynamic drag with

satis-factory hydrodynamic qualities.

Tite first step by the NACA in furthering this

hvelop-meat vas the investigation of two forms of hull in which the fore and after planing surfaces vere shaped to follow as closely as possible an arbitrary streamline body derived

from a solid of revolution (reference 1). The forms vere generally satisfactory in

tite tank although they showed

some evidence of "sticking" anti high water resistance at

high speeds and some "dirtiness" at low speeds.

Their

aerodynamic drag vas low enough, however, to warrant the acceptance of a certain degree of poor water performance.

It vas evident from the tank tests of these models that

the limitations on reductions in aerodynamic drag imposed

by the hydroclynamic requirements were not deffnite enough to provide simple guides for the most favorable compromise.

It was therefore decided to obtain hydroclynamic and aero-dynamic information on a series of related forms of hull representing various degrees of corn promise between the

requirements in the air and ou the water. These data would

make it possible to obtain an idica of the cost in vater

pet-formance to he paid for further aerodynamic reFinement and of the cost in range or pay load to be paid for certain desirable

hvdrodynamic characteristics and would be further guides

for over-all improvements in form. The NACA model S4 series of hulls was designed for this purpose.

The models of the series were macle generally similar to

model 74A (reference fl except that a V-section was adopte.d for tite planing surfaces instead of the section with rounded

keel incorporated in that model. The use of the V-section

restdtedi in slightly greater departure from the form of the basic streamline body than was the case with the earlier models but seemed to be preferable for operation in waves. In the design of the series, the plan forms of the streamline body and the planing surfaces were held constant. The variations of form included in the scope of the investigation are as follows:

Height of 1)0W Height of stern

Angle of dead rLe at bow Angle of dead rise on afterhody Depth of step

Angle of afterbodv keel Addition of chine flare

Addition of third planing surface on tail Rounding of chines at bow

Depth of streamline body

The models of the series were tested in Langley tank no. i

to obtain the effects of the variations in form on the water resistance, flow, and general bdhavior. The aerodynamic

tests were made in the Langley 8-foot high-speed tunnel and

provided an unusual opportunity to obtain the effects on

the aerodynamic forces at high values of the Reynolds

num-ber. The tests in both the tank and the vincl tunnel were

made with models of tite hull alone anti hence do not include the effects of interferences between the hull and the aerodlv-namic surfaces or the possible effects of the changes in form on time dynamic stability.

DESCRIPTION OF MODELS

The lines of the NCA model S4 series, illustrating time

mutual relationships of time variations in forni, are shown in figure 1. Enlarged body plaits showing the shape of the transverse sections in dletail are given in figure 2. The numerical values of time offsets used in tite construction of the models are included iii tables I to III for misc in reproduc-ing the detailed form of the sections.

The basic forms in ail cases were derived from the arbitrary body of revolution, having a fineness ratio of 7.22 and

maxi-mum ordinate at 30 percent of tite length. described

in

reference 1. Because of the anticipated use of supetchiarged hulls for long-range seaplanes, tite basic forms tvere

consid-cred to represent the circular shell under internai pressure

and tite modifications for water performance 'vere, in getters1, made exterior to them.

Tite basic cross section of time planing surfaces is a straight V having ami angle of dead mise of 20°. Time sides of the V

were drawn tangent to or as close to the circular section of

t-lic basic form as tite proper longitudinal form of the planing

stufaces would allow. Typical relationships between the

sections of the planing surfaces and those of the basic forms are indicated on the body plans.

Bow 3-- Bow 2'--- Bow I Bowl - Bow-I

Wil/,ouf chino flo,-o

k/,tI, chine

C.C. all models

- 720

Heiq/,/ nf 1)0W. wi/i, and wi/hoyt chine flare _{/lciqh/ o( o/Orn, wi/h and wi/h,out chine f/ore} Angle of dead rise of how. wi/h and wi/h out cloue flare

Hiq/ bow

Basic form ond pioui of o/I models

---Steru' 3

Bowl

-.-5ferr' 4 5/orn 3 S/er,, 2 Stern 3 Sler,i 3

Bow / - Bowl Bow I

Angle of al/erbady keel, c/,ine (lare on forebody oii/y Dep/Ii of etep, chine flare on loréhody only

Stern 4

Chine o,, low fail, no c/i/n e llore

S/er,, 4 _{-Sterfl 4} Stern 2

'-Stern ¿'C

A,,q/e of dead rise ot bow, with ond wi/houf chine fiai-e

Angie of dead rise on aflerbody. chine fiai-e on torebody only

Medium bow

Chi,,e flou-e on ollerbody

Chine faded ouf of -bow, no chine f/ore

I Lirici, nl N A C A u,,eI,I III serio).

--Ch,neno f/are

8ow/

Chine wi/h fiat-ei

- Tafi9ency of chine

rOdhi5, bow /4

Chi,ie, no flore Ch/pie wi/h f/are

ßae line

Ch,no f/are

Chine wi/h f/are

(c) (el l4, os 01111 1.-t. (I.) Ilov 2. (b) (e) flow 2)4. ii e A 4 A 10041e) 84 soies. Ilcoty IllollS.

Chino, no f/ore Chino wi/h f/O/E2

CdC

ose line-:

Chine, n o f/ore Chine wi/h lloro

FjuuIu. 2.Couttiuiued.

(r) Sleruis 2

St.

Chine, no flore Chine with f/ore I Stern

2 Stein 2C (1) (il) hou' (e) (e) Row h

Chae. rio f/ore Chine wi/h f/are

(g) SItrui 3.

(h) $krui 4.

tilt

2.-COlÌCItltI4tI.

Chine no f/ore Chine wi/h f/are

N o H p Q Q H o (I) o N H (-3 o H H t'i N "i o N N o r) H ri (ii

(g)

In all tII(' I11O(IelS, the axis of the body of revol] tion vas taken as tIi base lilie. The variations in height of bow aiìcl in !wight of stern \VcÌ'c obtained by beiiding the axis (center of radii) vertically ul)\var(1 from station 10, 'hic1 is at tut'

mzlxirflurfl oid iiiatt. tovti.id the ends. In the variations of

tut' 1)0W, tIfl S('CtiOlIs of hovs i , 2. and 3 and tue sections of

bOWS 2B and 3B are tli sanie, the differences being in their vertical position.

The axis of bow

i is horizontal and

coincides vit1i the base lifle. Tue chines at the bow are located in a plaite passing through the axis of revolution of the basic

form. Tite curvature of the axes of bows 3 and 3B is such as to give a horizontal deck line forward. The heights of

tu1( axes of bows 2 and 2B are one-half those of bows 3 and 3B ; thus the variations in height of bow sections in the sexies are linear. In the variations of the stern, the height of the basic form was changed but that of the planing surfaces

was held constant. The axis of stern i

is horizontal and

COiflCi(l(5 With the base uiiie. This stern was not included

in the liti!! models because the tail obviously is too low for a

suitable support for tail surfaces and for proper location of

tlìe after planing surface exterior to the basic form. The

curvature of the axis of the basic form of stern 3 is such as to give a lìoiizontal (teck line aft. The heights of the axes

of sterns 2 and 2C are one-half those of stern 3 and the heights of tuìe axis of stern 4 íuc 1.5 times those of stern 3; thus the variations in the height of the basic form aft and in the

verti-cal distance between the basic form and the after planing

surface are linear.

In bows 1, 2, and 3, the V-bottom sections arc tangent. to tlìt' basic streamline förm and have; a constant angle of dòad rise of 200. These sections result in a developable bottom surface and a minimum departure, from the basic form for

V-sect-ions exterior to it. In bows 2B and 3B, the original

keel line was dropped to give a progressive increase in angle of dead rise from 200 a-t station 10 to 600 at the bow. This

modification result-s in greater departure from the basic

forni but provides a sharper entrance for the immersed

portion of the hull.

The chine flare- is exterior to and tangent to the straight

V-sections and therefore slightly reduces the effective dead

rise. Forward of station 10. its width is one-fifth the

half-breadth and it is curved to be horizontal at the chine. Aft

of station 10, the width of the chine flare is arbitrarily

re-duceci to 18 percent. of the half-breadth at the st.ep and the

angle of tue clime is slightly above tue horizontal. In this region, the width inboard of the -flare is constant. On the

afterbody, the- forni of the flare at- each station is the Sanie

as at the step. The models were originally matit' with the flare, which was removed during the tank tests by planing

itoff.

-The models of the series were made wit-h a cOIflfl)Ofl depth

of step of 2.5S perce-lit of the- beam a-t the step and an angle

of afterbodv keel of 5.500. These values result-ed in the

highest. posit-ion of the afterbody planing surface for stern 2 without- cutting into the basic- form aft and represented t-lie

lowe-r limits of depth and angle used iiì practice-. Higher values were obtained with removable bloc-ks fitted in stern 4,

7474''-47.-which liad sufficient clearance between the highest aft-er-hotly position and the basic form to avoid cutting into it.

Fi ve l)lo(ks we-Ic provided as follows:

Block 4 was made v'itli chine flare, which w-as subsequently

removed. For simplicity, the remaining l)lÓcks were made

with straight- V-sections and the models vere tested with

chine flare ou the forebodv only.

An additional block, block 4H, having straight V-sections

with the angle of dead rise decreased from 20° at the step t-O 0° a-t the stern post was provided for stern 4.

In this

block, the depth of step was 2.58 percent of the beam at the step and the angle of afterbody keel was 7.25°.

Stern 2C is the saine as stern 2 except that the shape

of the basic form was altered

to provide a third planing

surface tinder the tail for cleaner running d uring immersion

at low speeds. The surface lias straight V-sect-ions with 20° angle of dead rise and fades out- above the afterbody

planing suface in the usual niaiiiiei.

In this case,

the

surface cuts into that of the basic form; it is unlikely that this part of the hull would be supercharged. Stern 2 was chosen for this modification because of the additional dirti-ne_ss expected with the low tail, which voulcl not be so

marked iii the case of the higher tails.

Bow lA is the same as how i except that- the chines are

rounded forward of station 7 using an expanding radius

as showii on the body plan (fig. 2 (a)) .. This modification

vas applied only to the low bow because the hydrodynamic

effect of the rounded chines would be less marked in the

case of the higher bows.

Figure 3 shows profiles of the models test-ed in the wind

tunnel in the present investigation.

Nose 1

and tail

i

reproduce tite body of revolution from which the models of the series were derived and the combination represents the streamline body of lowest drag with which the drags of the hull models ma-v be compared. In -the second form, the depth of the original body is arbitrarily increased 50

percent by inserting a uniform space-i at the axis of

revolu-tion. Tins modification does not affect the hydrodynamic characteristics and therefore was not- included in the tank

Series. The rest of the forms investigated are the-- same as

those- tested in the tank.

The inotlel of the series are, icleiìtiFied in the data from tIn tests according to table IV. Tise models vere made of lan(inated whit-c pini' in sections, divided vertically at sta-tion 10 (maximum beam) anti horizontally along t-lie axes of

the basic. forms.

The bow and the- stern sections were

bolt-cc! together internally and the top and bot-tom halves were held together by through bolts; the recesses for the nuts of these bolts vere filled with beeswax an-d plasticine.

Depth of

BIcS Step, percent

beamst step ArtCk 01 alterhod y keel, tice 5.50 5, 50 5. 50 7. 25 9.00

AE1ODYXA\11C AND HYDRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HULLS ₇

41) i. 55

4E 4.52

4F

Sow 3 Bow 2 Boii I 5ow I Sow I o) 8ow2--Sect. A=A"0e êß

NoeI""

Sos/c streamline Shapes

1/4.35"

50./O ><-33.23"

F. /0 /3 2i/ 4f'.

Sos/c form ond p/on of o/i mode/s

&" ,Cenier of rot of/on - a/I mode/S

Cen/er of momenrs - o/i mode/s Height of bow. No chineS f/ore.

b/eïght of stern. No chine fiOre.

Angle of dead rise at bow. Medium bow. No chine f/or e.

A

Depth of step. Noch/ne f/ore.

F,' L n E Lines uf NAC A niodid S4 series. SIn)s' ing forni> te>ieiI in wind Lun nel.

Tail 3 Tail / .---To,./ / _.Stero 3 Stern 4 Stern 4 St orn 3 Stern 2 ç Sect. A-A

8 REPORT NO. 766NATIONAL ADVISORY COt\IÏ'rTEE FOR AERONAutICS

This arrangement provided the variety of forms .escribed with tue minimum of component parts and a means of

in-creasing tue depth of any model by spacers, as in model 84-1.

For the tank tests, the models were filled by several coats

of thinned varnish and finished with three coats of gre\-

pig-mented varnish rubbed between coats. Special care vas

taken to prevent, swelling of the pieces because of moisture,

and the slight ledges at the joints found on assembly were

sat.isfac torils- faired with beeswax.

For the aerodynamic tests, from 14 to 20 coats of lacquer

were sprayed on the models and the lacquer was sanded be-tween coats.

The final coat of lacquer was finished by

sanding in the direction of air flow with No. 400 carborundum paper until the models were aerodynamically smooth.

Un-fortunately. the photographs indicate a degree of irregularity antI roughness that did not exist.. This apeaiance of rough-ness was caused by the variation in siracles of the filler and the paint that were used.

HYDRODYNAMIC TESTS

APPARATUS AND PROCEDURE

Langley tank IR). I , in winch tire niodels vete towed. is

described iii refererue 2. 'fIre niost cornpiehensi-e diescrip-tion of thic 1)1t'Se!ut eqt1iJ)flent arid of methods of testilig

niav be fou un i ii e fe re rice 3.

\lost of tin' \aiia lions iii [lie series ar.e of such a nat u re that tin' J)arts ehia.irged are clear of tue '\vater except at

10-Sl)eedS \vhl(Il tire models are deeply ininlersedl \.t these

Sl)ee(lS. tiri' vater forces J)rcdonhirlat' anti tire trini is noi

greatly iIiílu(riee(l by the position of the center of gravity

or by external moments applied by the propellers audi aero-dynamic surfaces. lt was therefore considered adequate to

investigate tire effect of the variations by general free-to-trim tests up to tire speed at which tire afterboci plamrg surface

was first clear of tite water. This procedure provided

representative information oir resistance arid flow about.

thd models at trims corresponding to those encounteredi in

practice At the samt time it gr(atl\- reduced tire testing

required to obtain similar inforfna.t.ion by ger1(r-a1 tests at. fixed trim.

Irr tire case of variations irr tin form tira t are normally

vetted lt piarririg speeds, the usual general tests at fixed

trim were niude over a wide i-ange of speed- load, and trim

to determine tui' effect' of tire variations in forms on the

re-sistance arid beiravior at' speeds and ini addition to provide data for- design purposes. All tire models testet! by tire general fi-ee-to-trim metirod at low speeds and

models S4AF, S4EF-1. 84EF--3, 'and S4EF-4 \verc tested

by tire general Iixed-ti-im method

-Irr tire free-to-trim tests. the model wa.s fred' to ¡)iVOt about

u ri asstrrned center of gravity aridI balanced about this'

point. For' coin venileuce. tire pivot was located above tire

tuck irrt r on tire assumption tirai small changes irr vertical

position would have small eth'et oir the t rim Model S4EF.

iìrivirtu.r tin.' low bow arid high stern, w-ris tested first. '.vi'tir

three longitudinal positions of the center of gravity. Fi-orn

the results of these tests, the position 7.20 inches forward of the step was chosen as a stdtable common position for all tire models and as the center of moments foe the tests at

fixed trim,

The appearance of excessive dirtiness amid spra\ 'at the

bow at low- speeds was assumedi to iñdicate tire maximum

practical load and was found to he that. corresponding to a

load coefficient of 0.8 at the hump speed, It Was not

conid-cred advisable. to go to higher load coefficients with the length-beam ratio' used in the series even in the case of the higher bows,

Iii jirdiging the effects of the vamiations on water perform-allee, the' flow andl spray were considered the most important

'hydirodivnamic. ciato because of the small effect of most of the

variations in forni on the mesistance at the hump speed. A lange number of photographs of tire spray patteruis were

ol)tai'fled to record

the effect on the spray pattern of the

changes in foi'rli ariel to aid in determining suitable

eom-l)romses with tire aerodlynamic properties as determined in tire wind-t.winic'l tests.

Tests iniolving variations in the

forni of Ì)Ow generally were photographed from ahead of the

niodel in order' to obtain indications of the relative heights

of the' l)OW 5i)r'aY ; anti tests involving variations iii th form

aft were J)lrOtOgiaphiedh fmom behind to' record the spray pattern in the megion of the tail extension.

RESULTS AND DISCUSSION

The results of the model 84 Series tests were reduced to

the astral coel'hicients based on Froudle's law to make them

irrr.iepencient of size, In this case, tire maximum beam was'

chosen as the eli-a racte.r'istic. diunension. _{Tire nondimensional}

coefficiinrts arc defined as follows:

('

loa cl coefficient. (/wb3)

C resistance coefficient (R/wb3)

Cv speed coefficient. (T7-/qb)

C,11 trinhmmg-moment. coefficient (JI/'wb4'

Cd draft. coefficient. (d./b)

where

load on writer. pounds

w Specific weight of water. pounds per cubic foot (63.3

for these tests; usually taken rs 64 fon' sea water')

b maximnuni beam, feet

R resistand'e. pounds V speed, feet. pen' second,i

g acceleration of gravity. 32,2 feet per secondi per second

JI

trimming moment, pound-feet

d. di'aft. at main step, feet

Any consistent system of units may he used. Tire moment.

data are referred to the center of moments shown in figure 1, Tail-lrerrvy moments are considereti positive. Trim is tile

'angle between tire base line of the model and tire lron'izontal,

Selection of the longitudinal position of the center of

gra-c'ity.----Tiie results of tire general free-to-tm-mr tests of

model 84EF it three fore-and-aft positions of tire center

of gro vitv ore shown in figure 4. Moving

the center of gravity from 5.7 inches to

7.2 inches forward of the step caused a small

decrease in trim and a small reduction in

resistance. Changing the position from 7.2

inches to S.7 inches forward of the step

produced a negligible variation in resistance.

At the most forward position, the low trim made the bow appear dirty and the model displayed a greater tendency toward

longi-tudinal instability. The intermediate

posi-tion, 7.2 inches forward of the step, was

used for the rest of the investigation.

Effect of varying the height of the bow.-Raising the bow, if the forebody length is

kept constant, reduces

the buoyant and

hydrodynamic lift of the forebody at low

speeds.

This reduction results in the

de-crease in trim at low speeds shown in the

general free-to-trim curves of figure 5. The

decrease in trim is accompanied by a defi-nite increase in resistance

for the higher

bows, models 84BF and S4CF.

In the

case of the higher bows, the increased con-vexity of the buttock lines produces a more blunt entrance into the water, causes a

tur-bulent bow wave (figs. S to 11) to be thrown

forward, and increases the resistance. The

approximate heights anti densities of the

spraY for the three bows may be compared in the photographs of figures 6 to 11. The

low bow, model 84AF. representing

the

smallest departure from a streamline form, not only has t.he lowest resistance but also

is the cleanest running bow.

Removing the chine flare did not change the order of merit of the bows but acceutu-atecl the increased turbulence of the high

bow. The use of any of the bows without

the chine

flare is inadvisable, however,

because of the height and the amount of

22 20 .18 .16 .14 .04 r 2 /4 /2 0 Q. 4 2

the spray at low speeds (figs. 7, 9, 11). 0 .5

It must be remembered that the curves

and plie tographs given vere ob t a i n ed

from tests matie under relatively smooth

vater conditions. If the hulls vere tested in rough water, the low bow would be rery dirty because it does not have

sufficient clearance. It is thought, therefore, that a moder-ate departure from the basic form, produced by raising the how, would he preferable for cleanness at low speeds. If

the forebodv was lengthened at the same timo the bow was raised, the entrance in the water would be less abrupt anti the spray characteristics would he improved .A higher how of this type might he more favorable even in smooth water.

C.G. forward of s1ep, '

--57

7.2

Fin tx e 4E feet of ei 1ml in,l posi t ion of the cr,ttr of gravil y Mo hl 01- E f.

8

.6

.6

Effect of varying the height of the sternA cotnparison of the resistance and trim curves for t1uce heights of the

stern is malle in figure 12. Tius investigation was made by

the general free-to-trim method because the portion of the hull that was varied is completely clear of the water just over the hump speed. The discontinuity near the hump speed, vlueh is associated with the clearing of the tail from

the water, occurs at a lower speed as the tail is raised. The maximum resistance is about the same for the three models hut the speed at which it occurs is lower for the high sterns.

lo

REPORT NO. 766NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

10 ¡.5 2.0 2.5 3.0 3.5 4.0 4.5

y

.22 20 .18 .16 .I4 .121 E -4 2 (a)

-4

.1) I'

/ 4I

Speed coefficient 'C (a) 'With chiilefinra.

C8

.22 .20 /9 /6 -/4 04 Model Bow Step-n Description 84-AF / 3 Low bow

- 84-8F

2 3 Intermedia/o bow 02/4 ---94-CF 3 3 l-119/1 bow

0I0

, - rB-- E FIG U iii

.E !Tect irjieiglit ol i,oa'.

t'

/4 I'

-/ -/

II I

-.6

,//

"IA

./

f/I

/

/

T----

-.4 .6 1.0 /5' 2.0 2.5 30 3.5 -40 -4.5 Speed coefficient, C,,

(I,) \V itliotit chitie Iltire.

'il ;0. I-, (-i -i o

Model Bow Slap-n Description "I 94-A / 3 Low bow

--84-8

2' 3 Intermedio/e bow o

----84-C

3 3 1-1/gli bow ri C!) 3.5 /0 1.5 2.0 2.5 3.0 o 4.0 4.5 o "1 ri

Q'

o' ci c ri ri w

j

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AERODYNAMIC AND HYDRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HULLS ₁₅

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REPORT NO. 766NATIONAL Abv1ouv COMMITTEE FOR _AERONAUTICS

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22 REPORT NO. T66NATION.L ADVISORY COMMITTEE FOR AERQXALTJcS

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AERODYNAMIC AND HYDHOOyNAIIC _{TESTS OF A FAMILY OF MODELS OF}

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AERODYNAMIC AND HITRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HULLS ₂₅

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AERODYNAMiC AND HYDRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HULLS

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.10 .08 a 22 _{.20 .18 .16 .14} /2 _{.06 .04} -9 E -6 -4 -2 (a) r _I., 'oae*,.L -L

r-,t

L--Model 8ow 84-0F /

--94-AP

/

---84-EF

/ -

-r.-r-I

0 .5 /0 1.5 2.0 2.5 3.0 Speed coeffic/enf C,, '. C 6

--- 4

Stern Description 2 Low stern 3 Intermediate stern 02 4 /liqh stern o

-.6

.6 2? ¿0 _.18 /6 _{.14 .04} b E -6 4 2 (b) '((E (It

12.--- E feeL of heIght al stern.

Bow Stern Description / 2 Low stern / 3 Intermediate stern / 4 h',qh stern .6 1.0 1.5 2.0 2. 3.0 Speed coefficient, Ç Ç-9 .6 .4 .6 3.5 4.0 4.5 Go 3.5 4.0 4.5 o (J' o -4 -1? -/0

(u) ',ViEl, e,iiie lI;ire.

(I,)

Below humi) speed tite model with the low stern. model

S4-DF, has the lowest resistance and trim. The decreased

trim indicates t.It tut' round tail, which is wetted at tlìese

speeds (fig. 13), instead of l)rOcluciflg hydrodynamic suction

actually deve]O1)S hvclroclvnamic lift.

The low trini is the

greatest factor in producing a reduction in the resistance

1)E'CaU5C' the model is then ruirning at an attitude. nearer the trim for lflimflfllfll \voter resistance.

The effect on the sprov produced by varying the height of tlk' stcin can be seen by studying the stern photographs

of figures 6, 7, and 13 to 16. At low speeds, the sides of

the stern of model S4-DF are wetted out to the tail, whereas the sides of tue li.igli sterns are relatively dry. The photo-graphs show that the tail extension for the high sterns is clear of tue water at lower speeds, as was indicated on the

resistance. curves. After tue ta-il extension is clear of the

\vater, the models are all at al)out the saine trim niul the

spray patterns aie simila r.

Although till low stein model S4-DF,

has the lowest

hvdroclvnaniie resistance aitci is the iiearc'st a1)I)rOfL.C11 ill the

series to a streamline form. tite p1ìotogI'a)h1s show that it

is impractical because tile deck of the tail, on which th.:

control surfaces are attached, is actually submerged at.

some speechs and loads. Provision would have to he niade to

give the tail asseinbi

greater c.heara ice if

this form of

bu li were to be used.

Removing the flare from the chines of tite models did

1101 change the relative performance of the tail extensions.

Effect of increasing the angle of dead rise at bowThe

effect. of increasing the angle of (lend Íise of the intermedia te bow, model S4-BF. and of the high bow, model S4-CF, i

shown in the general free-to-trim curves (fig. 17). With

the angle of dead rise increased forward, a slight reduction

in the resistance is obtained before the hunip speed, whereas

the change in trim produced by this variation is negligible. With the chine finie remOVed, the reduction in resistance

was slightly greater. At the hump speed, tile portion of the hull affected by this change in forn is completely clear of the water.

The main effect. of tile vai'iat.ioii in dead rise at the how

is the change produced in the flow and the spray originating

at the bow. A coiparison of figures S with iS, 9 with 19. 10 with 20, and 11 with 21 shows that the finer entrance

(finer water lines) of the hull, obtained by increasing the dead rise, definitely improved the cleanness of running at

low speeds. Instead of a heavy turbulent wave being shoved

forward, niodels S4-BF, 84-CF, 84-B, and 84-C, the bow wave is highteú and most of the watr is thrown laterally,

models S4-FF, S4-CF, 84-F, S4-G. The removal of the

chine flare probably accentuates this improvement in spray

characteristics. The bow of model S4-FF appeared to be

tite best in the series.

Effect of a decreasing angle of dead rise on the

afterbody.-The results of the general free-to-trim

tests of model

S4-EF--4 aiìd nioclelS4-EF-6ar. cOlflI)aIedl in figure 22. The

decreasing dead tise aft increases the lift. of tite aft.erhody

nudi tiierefore rechices the trilli. A reduction ui trim of 2°

is obtained at. the hump. The (orrespondlmg ielucLion in

resistance is about 15 percent .

\tost úf the reduction in

resistance is clue to tite low-er trini.

The effect of angle of dlCì(h lise Oli the aftcibodv is shown ill figures 23 and 24. Model S4-EF-6 runs a. little cleaner than IflOd('i S4-EF--4 because of tIn' dhecreased triai that

tenls to briiig the oft.eibodv auch tail extension clear of the

water.

vIodel 84-EF-O 5hiOwedl the

least. tendency toward a

lateral iiist.abiiit.y at low speeds that seemed to be utherent

in thid Sirius. In the photographs of moçlel84-EF-4 (fig. 23)

at a SPe(d coefficient. of C,-=2.13 and a. load coefficient

of C=O.4. a laterally

)rOjected jet of water originating under tild afterbodv is seen striking the side of tite wake.

\Vitii the heavy loads. O=0.6 and C.=O.8,

this jet lias a

high enough velocity to bounce baák, hitting the sidle of tite

Iili)dlcl foI\\ard of the sterit l)Ost. This flow is generally

unsymmetrical arid COUSeS tite model to swing laterally on the suspension. The instability is accompanied by a

discon-tiiiuitv in the resistance. \Vith a diecreasing dead rise oi the afterbodv. model S4-EF-6. the unsymmetrical flow

appar-ent.lv was reduced arid the lateral instability was negligible. It. is doubtful if this instability is selious, inasmuch as it is

l)1e5('flt in Iflost fl)O(lelS with 1)011) tech aft.erbodies that are

tested ill the tank. The method of towing probably niagni-fies this characteristic.

Effect of increasing the depth of the stepAt low speeds, tite variation of, cieptht of step lias only a small effect on

either hie resistance or tite spray (figs. 25 and 20 to28). At.

the hump speed with the heaviest load on tite models,

in-cteasing tite depth of step from0.40inch. modelS4-EF-1. to

0.70 inch. model S4-EF-3, resulted in i maximum increase

in trim of about 10 aridi a corresponding increase in resistance of approximately 5 percent. The greater prirt of titis change

in resistance is clue to the change in trim. Titis fact is

evident if tite resistance for model 84-EF--3 is determined

from tite generai test data (sec fig.40) using tite saIne trims

obtained for model84-EF-i in figure 25.

Tite only visible effect on the spray at low speeds is the

clearing of tite afterbody front tite water at a lower speed for

tue greater depth of step. (See figs. 26 to 28.)

In figure 29, the resistance coefficients at high speeds for

0.40-inch and 0.70-inch depths of step are compared at

attitudes of the hull (trinti r for minimum water resistances

for 5°, and for 6°) which are practical for tite operation of the

hull and

presumably can be obtained with the control

momcit. available at these speeds. The effects of increasing the depth of step were similar to those.reported in reference 4. Increasing tite depth of the step by raising tite afterbody

provides greater clearance amici reduces tile resistance.

30 _{REPORT NO. 766-NATIONAL}

ADVISORY COMMITTEE FOR _AERONAUTtCS

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4274O-47---5

AERODYNAMIC AND HYDRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HULLS

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AERODYNAMIC AND HYDRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HULLS 33

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AERODYNAMIC AND HYDRODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HYLLS

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-p-REPORT NO. 766-NATIONAL ADVISORY COMMITTEE FOR AERONATTICS

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22 20 _{.18 .16} i? ¿74' _3? o 4f -2 (a) 0 .5 -/0 1:5 2.0 i5 .7o Speed coefficient 6 (ai Iirir'riti liai,' hai,. wj ii chue liii .6 .4 Model Bow Sie,-,, 095cr/p//on 84-8g 2 3

Ca,,5 font onqie of decid rise

84'-FF

28

3

An9/e of dead rise ,ncreäs,nq fo,'svord

3,5 4.0 45 .22 ¿'0 /8 _.16 ci .04 .02 -/4 ,/2 0 :10 -6 ¿7 2 (b -l'lr;r'i,s: IT,

- Eli 5-Iii trigle ei (torti! risc il'

unti,

/

/

/

/

lciodet Boo., -Sieri, ûescr,,ot,on 84-8 2 3

Coi,i.tont onqie of dead

- 84-F

28

3

4hg/e of decid r,s _{Increase,9 íort-o.,,'d}

1.0 1.5-¿Q 2.5 30 Speed coefficient C,. liti

Itiirrinir',lj,ii,-ritte'. nvItlOiitl /hijjri

liii i,. t. 8 .6 .6 4 3:5 4.0 -4.5

N o z H o o, at H o i-' .'t. (1/ o z C.) o Li' L.' H H _t'i N t'i o z N z o z H r)CI)

/

/

>-/

A'bde/ Roiv 5/,-n IJecrip1ion 8'1C 3 3

(o/f angiò

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84G

38

3

¿Ingle of dead rise increasing forward

/6 _.10

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o8' e 06 0 /0 U' 8 G

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.ip"rI ro': f'I,cier/, (.

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Ii,r,i, i: h-i (i,,,'Ili,I,',h.

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/

/

AdeI Bow S/em

De5crlption

/

81-C 3 3 Cons/on! onglé

/ /

of dead rise 84-G 38 3

Angle of dead rise

p 'ì

/

. , »icreos,iig forward /2

/

.4 .6 /0 /5 ' 20 ' 25 30 35 40 4. 5pe'd coe(/',c,pn/, c ('I) II (0 i ((((' (S'il hioili 'hill, ¡Ir.

40 _{In:p)RT \Q 7töNATIQXAL ADVISORY cOSI I iiTr:i: FOH .AEHt)yAUII('S}

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42 REPORT NO. 766-NATIONAL ADVISORY COMMiTTEE FOR AERONAUTICS

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44 REPORT NO. 766-NATIONAL ADVISORY COLM ITTEE FOR AERONAUTICS

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Epoli'r NO. 76ilx..vrIONaL ADVISORY O2l M i'i't ER EOII EROXAI."l'ICS

In hgiire 2P. model S4E1" no data are. shown for the light loads at 5° and 6° trim because of a sticicing and ac-companying vertical instability not present at tue trint for

minimum w-ater resistance. A simihu' sticking and instabil-itv is reported in reference I. When the trim of tue hull is

such t-ha t the a.fterhodv keel is neaPly horizontal. the linie

front the main step suddenly covers the entire afterhody

planing surface and the resistance and draft. a re suddenly

in-creased. The flow then changes, permitting the model to rise

again. Often the model jumped coniphetelv clear of life

Sow Srerri Oesòpip'ion

4 Cor,stcnf' angle cl

dead rise cri oft et-body

4 AngIe of dead rise

decreasing cfi'

o-.6'

.4

FLiiE.--EllOcL ji Ineri',iuiiiiz linie uf cuit nun un ,itnrho,ii-. I.)ef,lh i iu. 'lu inch: iurf :,(i,rhuiv keel. 7.2.'. hin, file w f,nrnhwfe uiilv.

w:fter 'flic instability did ìmt appii:if. ft the trito hit uiui-mum vatet' rcistance because tite attitude of the hull ivas

he!ov the range in which tite aftethody surfaces are tirallel

to the ivatci'. At- a ti'im of 8° ut high speeds. the forehody

of the toilet is cleaP of tite ivat-er for light loads and the

resistance autl 51)01V u tli sattie as obtained when a 111111 is lfI!lflillg Ofl the ffterhltdv univ. lIl(reasin the -depth of

step t-o 1)7(1 inch (4.4 percent of thie heatu hv raising

the-t'!Itit'P afterhodv apparently remoi'iai tue tendency toward

T1Stfhuit y.

LO 1.5 ¿.3 ¿.5 3.0 3.5 4.0 45

AERODYNAMIC AND HYDRODYNAMIC _{TESTS OF A FAMILY OF MODELS OF} FLYING-BOAT HULLS o 4 L 49

k

r

f

AERODYNAMIC AND HYDRODyNA.IIc TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HULLS

ç-L

=

52 REPORT NO. 766NATIONAL ADVISORY COMMITTEE FOR AEROXAur1cs

It vas difficult to interpret. the sticking and

instability in terms of full-scale performance because no ottempt was made to obtain

dy-fl4lflhiC siniilûritv. _{The. mass moving vertically}

inclu(lecl the heavy niodel, the towing gote,

aI]d count.ervcjthts used for adjusting tile load on tue model. The model was also being towed

at fixed trims 011(1 any changes in moment had

no effect on tile attitude of the hull.

Later experience with dynamic models indi-cates that tile depths of step used in the series were too small for present-day take-off speeds.

Depths of step from 6 to 10 percent of the

beam are now- considered necessary to avoid dangerous instability at high-water speeds in-duced by the sticking observed in the present

tests.

Effect of angle of afterbody keel.A

coni-parison of the low--speed performance for three angles of afterbody keel is presented in gure 30. As the ongle of afterbodv keel is increased,

the buoyancy and the hvdrodvnamic. lift, of the.

afterbocly are reduced for any definite trim.

To compensate for this decrease in lift the

model tends t.o assume a higher trim. At. very

low speeds. this increase in trim is small and the change in resistance is negligible. The.

maximum effect is found at the hump speed at which an increase in angle of aft.erbody

keel of 3° caused a maximum increase in trim of about. 4° and an accompanying increase in

free-to-trim resistance of about. 25 percent.

_\'Ios.t of the increase in resistanc.e is due to

the change in trim, the higher trim causing a

greater departure from the trim for Iflinirnum water resistance.

The spray photographs for tile varioions of angle of afterbodv keel are given infigures 23, 26, and 31. With tile high angles of afterbody

keel, the roach from the after planing sur-faces continues to strike the tail extensions

at slightly higher speeds. _{The greater c1car}

ance provided by the high angle of

after-body keel causes the afterbodv to come out

of t.he water at a lower speed.

_{From observations and}

photographs it. is concluded that at low speeds tile model with tile low angle of afterbodv keel,

_{model S4EFI. \vs}

the cleanest running.

In the investigation of the effect of this variation on

high-peed performance, angles of afterbodv keel of _{5.50° arid}

7.25° were used. Using a

higher angle is nat advisable

)ecause it obviously causes too great an increase in the

.22-.20 .18 /6 14 .04 -.02-14 -/2 0 /0 r4 -2 LO 1.5

O

¿.5 30. 5 4.0 Speed coefíic,e,t C

F.fTeCL 01 Septti of s,ep. Angi, of allerbodv keni----5, Chi,- lure lnrehdy only.

hump resistance.

_{The results of the tests are compared}

(flg _{32) at the trim for minimum vater resistance a.nd at}

0

and 6° fixed trim. The. sanie conclusions may be drawn

fÍoin these tests

as were reported

in reference 5.. By

increasing the angle of afterhodv keel

a greater

clear-ance is obtained for the aft.erhoclv and the area of the

after planing surface struck by water from the main _{step is}

reduced

-AERODYXAI1c AND HTDODYNAMIC TESTS OF A FAMILY OF MODELS OF FLYING-BOAT HLLLS ₅₃

.5

n.-54 REPORT NO. 768-NATIONAL ADVISORY COMMITTEE FOR AERONATTICS

r-t

Y

y .

o

o

56 REPORT NO. 766-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

t

e n o ..t _¿

--o R

-'a

AERODYNAMIC AND HYDRODYXIIC TESTS OF A FAMILY OF MODELS OF

FLYINGBOAT HULLS

;À

58 REPORT NO. 766-NATIONAL ADVISORY COMMITTEE FOR _AERONAUTICS

k:

-o 0 o

08

0

08

f_R.

I!

_iRR.RR

-<T

E" R...

#IIP

R.R.

-

----.---

.__1__ .__1__ .__1__

--

I

:1"

_0.

_{. -}

111U1111

1-

-.

IRR.RR

_{R.I ---r}

4-cr, step T-3.7 84-EF- depth step depth - 84 Io

::

02 (h).-1

H

r

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60 REPORT NO. 766NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

45 5.0 5.5 50 55

70.

75 80 55 Q

Speed cae fi icier,t, C

Trim (or minimum crater resistance. ,.3°..

(e) c-=6°.

Comparison of the carves shows that a

greater diffi'rence in resistance is obtained .24

at 6° trim than at 50 trim. A greater

differ-ence is also obtained at. 5° than at the. trim

for minimum water resistance, which is _gen- .22

eraliv lower than 5°. The higher trims cause the afterbodv to approach the horizontal anti consequentl to be in a position to be wetted .20

by the flow from the main step. The model with a higher angle of afterbody keel in

com-bination with a shallow step displayed the

saine vertical :instabiit noted in the inves-tigation of the effect of depth of step. The

angle a t which the instability occurs is changed /6

to correspond to the angle at vhiicli the

aftér-body keel is parallel to the water surface.

For model S4EF-4 with a 7.25° angle of

''

afterbodv keel, this insta hilit.v first appeared

for a load of C= 0.05 at a trim of 70 At

a

trini of 8°, c=0.i0 was also unstable. The vertical motion was very slight at a trim of 9°.

These tests indicate that ah angle of

after-body keel from 50 to 7° is the most. suitable

compromise for satisfaétorv resistance at

th

hump speed and at planing speeds. A

form of hull with a decreasing dead rise on

the afterbodv in combination with _{a Iminlier} angle of afterbody keel as in model S4EF-6

might be used.

This combination would

improve the resistanc.e at. the hUmp and auto-maticaflv maintain increased clearance of tIme afterbody for good high-speed perfbrman ce.

Effect of the addition of chine flare.-=--In

order to investigate the effeét of the c.lune flare, the original models were tested with

th flare removed. The results of the general

free-to-trim, tests are. summarized in figure33,

and the effect of the addition of chine flare

on the

spra characteristics i's shown in

figures 15, 16, and 26.

In figure 33 a comparison is made of the effect of adding cuñe flare to the forebody alone, model 84EF1, and to both the

fore-body and afterbodv. model 84EF.

_The

following comparisons are made with niodel 84E, on which the flare was removed. _The

addition of the chine flare ôn the' forebodv

alone resulted in a small increase in trim

before the hump, the resistance remaining_{about. tEsame. At}

the hump, the effect on either the ttim or the Ñsistance is

negligible. The influence on the, spiav _{cb'aracteristic}

was very marked.

_{It is dicult to determin. the effect}

of the flare

_{on the spray from the stern photographs}

(figs. 16 and 6). _{At. speeds near the huni, the xnoel without}

the flare has a higher and

more dense bow blister. _The

observations indicated, however,that a chine flare on the

fore--6 -2 '5

-'s, /ili I i II! /0 1.5 20 _{2.5 3.0} Speed coefficie,,i, C, 6'

_f

'ii / fv__ " 3.5 .o :

Ficuoz 30.Effect o( angle oLatterhodv keel. _{Depth oI step, 04e luth. Chinef1ac on (orebody only.}

body is desirable throughout the how-speedrange. This con

clusion is similar to that drawn from the results

_{of tests}

reported in reference G. for corresponding widths and _angles

of flare. _{The addition of chine flare to both the forebody}

and afterbodv, model' 84EF, not only improved the spray characteristics but also caused a decrease in trim

_{at the}

hump of 1° and a decrease in resistance of S percent. Most

of the change in resistance is due to the reduction in trim.

.6 .4 Mo 001 84-EF-! 84-6F-4 84-EF-5 BD / Stern 4 4 4 '4ri9Ie of offerôody heel, de9 550 Z25 500

AERODYNAMIC AND HYDRODYNAMIC TESTS _{OF A FAMILY OF MODELS O}

62 _{REPORT NO. 766-NATIONAL ADVISORY COMMITTEE FOR}

74274-47---.-f

.7

k =

64 .1 .0 .0 .0 C o .0 .04 .02

REPORT NO. 766NATIONAL ADVISORY COMMITTÉ _{FOR AERONTJTICS}

a.

Load coeffic-ìent,

_.-'L'4.5

. J

____ _

¡ J 8. . 6

---4

iuuu

H

-. - / 05'--

---.

H---j

_.... I '

L

_H 84-5f-J, 84-fi-4, 5.5' 725'

an/e

onQ/e of fteòody 0/ _olterbody heel - _keel

()

I5

i -

dllll

im

--- c - - - - t

-- -

1- r 6.0 6.5 70 75 8.0 85 0 Speed ccel'(icetir, L',

(n) !r:m far k aire urn seater resistance.

(b) =.i°.

(C)

The presence of the flare on the afterbodg

increases the lift of the afterbody and

causes the hull to assume a more

favor-able attitude. _{The photographs (fig. 15)} show the spray and thewave form. The

chine fiare on the afterbody apparently

has little effect on the spray produced by

the afterhodv. _{The curves (figs. 5, 12,}

and 17) show the same reduction in trim and resistance. The bow photographs

(figs. 6 and 7, 8 and 9, 10 and 11) may be compared to see the effectiveness of flare

on both forebocly and afterbody in con- .14

trolling the spray.

The relative effect of the flare on the

'afterbody at high speeds may be seen by

comparing the fixed-trim tests of model

S4-AF and model 84-EF-i

(fig. 34).

These models are similar except for the tail extension which does not affect _the

performance at high speeds. The effect

of the flare on the afterhody at planing

speeds is to increase the resistance. Effect of the addition of a third planing surface...-.In order to investigo te further tile effect. of the flow around tile stern, _a planing urfacc with sharp chines vas

-added to the original round tail.

The

results of the general free-to-trim tests

are given in figure :3.5. _{The effect of}

add-ing the chines and the planadd-ing surface to

the tail, model 84-H. is' small, indicating - I.?

that the rounded tail, model S4-D.

pro-duces no tendency toward sticking. There is a negligible decrease in trim_just before the hump if the third planing

sur-face is added. The discontinuity

_{at the}

hump, associa ted with the clearin of the

tail from, the water, occurs at a higher

speed for model 84-H with the

_added

planing area. L? .10 .08 r o 0-10 o

The photographs (figs. 14 and :36) show

very little difference in spray for 'tile two

models.

_{The amount of loose water}

thrown vertically, when time roach

_{strikes the tip of the}

tail, is greater for the round tail.

_{With a low afterbody}

this effect may be very important. _{Time water striking the} tip of the tail seems to have no effect on the trim.

Effect of chines' on the bowThe

_{general free-to-trim}

results with the chines on the. bow, model 84-A, and' with

the chines rounded, model 84-J. _{are presented in figure 3'.}

Although the chines on the how llave little effect on either

time trim or the resistance, tIme photographs (figs. 7 and 38) show very large differences in the spray. Instead of having

the spray deflected downward, the model with rounded chines

has a large amount of loose water thrown up and fòrward. These photographs indicate that a fading out of the chines

.6

-q

C/,,ne f/o,-e on hrebody

Und fre,-L,ca\'

Cñ,ne flore on forebody only

iWithowl c-h,-,e fícr

ov .Stcrr,

/ 4

/ 4

/ 4

AERODYNAMIC AND HYDRODYXAMIC TESTS _{OF A FAMILY OF MODELS OF FLYING-BOAT HELLS}

65

/0 1.5 _{2.0 5 3,0}

Speed coeff,c,c,-,t C,

.3.5 4.0 4.5

F,cm1,E i3.-Et1ect of chine flare.

at the bow is cicuinitelv undesirable _{even in smooth water.}

Design charts.Comple.te data for model

S4-EF-3 are

presented for design purposes. The detailed general

free-to-trim curves are included in figure 39 _{The results' of the} fixed-trim tests are presented in the form of charts (fig. 40).

The use of these charts is explained in reference 1. _The

trims and drafts at rest, covering a practical range of loads, are given in figure 41. Tvpical.sprav patterns at highspeeds

near time trim for mininjuni water resistance _{are shown in} figure 42. The low-speed

_{pilotographl are presented in}

figure 28. _{Because of the large amount of other data}

pre-sented in tins report., corresponding designdata _formodels S4-EF-4 and S4-AF have been omitted.

.10 .08 .06 .04

1.::

.04 I) n 0, o .10 .08 .06 .04 ca I. 1

-I

H______

iíÍìlRL

.11.

()

I

H

.84-5-F-b, 84-At no w,f h flore f/ore on af/erbody on c'fferbody

---(b).

--H

.

(ì

-66 _{REPORT NO. 766NATIONAL AD\ISORY COMMITTEE FOR AEONAUTICS} Load coefficient,

45 5.0 5-s. 6:0 6.5 Z0 75 8.0 - 8.5 s. o

5,oeed coefficient. c

Trim for ii tiniurn water resistance. v.5°.

(e)