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i

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

IrllRTIMlt REPi)RTORIGINALLY ISSUED

September 1942 as

Ad.'v_e Confidential Report

AN INVESTIC_ION OF _ROFOIIS IS THE _

I -- EFFECT OF DIhEdRAL A_D DEE_ OF SUBME_31C_

By James M. Benson an_ l_o_nan S.

I_ley Memorial Aero_utical Laboratory

l_ugley Fle.lcl, Va.

..... i i i ii!iiiiiiii ii : ! ! iiii!i iiiii!i iiii i i i i iiiiiiiiiiiiiiiii! ! iiiiiiiiiiiiii i i ii!i!J"' ::::iiiililiiiii!iii!iliiiiii!iii!iiiii::"":':"

WASHINGTON

NACA WAI_TIME REPORTS are reprints of papers originally issued to provide rapid distribution ofadvance research results to an authorized group requiring them for the war effort. They were pre-viously held under a security status but are now unclassified. Some of these reports were not tech-rdcally edited. All have been reproduced without change in order to expedite general distribution.

T._ 7_8

NATIONAL ADVISORY 00MMITTEE FOR AERONAUTICS

ADVANCE CONFIDENTIAL REPORT

AN INVESTIGAT.10N --OF.HYDI_0.F01LS. IN .T-HE NA.CA: .TA_NK. . . ..

.;.- - ........... - ....

..... ..... .I.-- ..-EFF.EC.T0.F DIHEDRAL AND DEP:T.R..0F ..SUBMERSION

.... -., B_r S:am.es M..Benson and Norman S.-_nd: :

SUM_ARY

• • ,, ,,

...:. E-f-forts _,t;oemploy i!ydr.o.fails .on se_p!a.nea and surface

b.oat.s hav.e frecue_tly been .handicap.pe'd _by the lac_ .of in-

.form.a.h:ion ..on the characteristic.s of; tl_e hyd:rofoils _ when

nea:r the surf.ace ,of the .watBr or ,when hreaking _he surface.

ln.the present tests, a serie-s bf hydrofoils,-ea'ch _upported

by two struts, was towed _.t various depths ranging-from

oartial submersions to a depth of 5 chord lengths. Results

are presented s.h:owing th:e._lift ahd drag of hydrofoils hay-

. !ng a .chord. of 5 inches A a so_:n: .of .30 inches, a-a@ for.angles .of dihedral af 0_., :l0°., 200, and 80 °. The tests

- . in.clu.ded speeds up to 95 fe_t pe.r second :_nd lift forces

up _ ' 0 ..:._o about .250 .pounds Th_ hy@rofoiis tested in.¢'luded

t,,vo sections, the Z_ACA-_-16-.._09.,air.foil, sec.tion a_}d: !a: section

derived from the 16-:509. by., s.h_rp:eni.ng, the leading"edge,

.At d,ept.hs, gr.e._.ter than.4 .or 5 chords the or.esence of

the free water surface appeared not to affect the lift and

drag. As the hydrofoil approached the surface, the lift

and drag decreased and the speed at whLch cavitation first

appeared on .the :hydrof.oi'!--was incre.ased. In the range of

very sha.ilow immersions (less than, say, 1/_° chord) abrupt

changes in lift and drag occu-_'red when the flow of water

over t.he uppe_ su.rface sep.ar_..ted from the hydrofoil. For

applications requir.ing that the. hydrofoil emerge from thewater, the larger angl.e,_ of dihedral (_0 °. and 80 °) appeared

desirable blecause they produced less abrupt chenges in

lift and drag..

Two major effects of speed were notedi first, a lim-

itation, of the total hydrofoil loading p.ossible (about 22.00

lb/sq., ft for the deoths tested) under conditions of com-

plete upper-surface cavitation; and second, a loss of lift

athigh speeds and law angles of atta.ck, probably due to

lower-surface cavitat ion,

2

I TRODUOTIO

To date, the use of hydrofoils on surface craft and

seaolane_..h_s_ been _ mostl'y experimental_ Although some

of the projects making use of hydrofoils may have contin-

ued. for a con_sfderable tlme, they appear to have achieved

no oractical applications that are in service today. One

difficult_ undoubtedly encountered in the ef[forts to make

use of hydrofoils has been the lack of _vailable informa-

tion on their fundamental characteristics.

Tests have be_n made at the NACA tank that answered,

in part, this need for preliminary information. The first

.NAOA report on-hydrofoils (reference l) contained data on

six zere-dihedral hydrofoils of different sections. Those

data gave lift and drag coefficients of each section as

affected by angle of attack, speed, and .depth below the

surface. Speeds a_ which cavitation first appeared were

also given.

The purpose of the tests described herein is to sup-

plement the information _iven in the first report and to

extend it to include the effects of dihedral, of partial

submersion, and of sharpening the leadin_ edge. Data are

presented to show the effect of.these variables uoon the

lift, the drag, and the cavitation speed, The hydrofoils

with sharp leading edgesw_re tested in the b_lief that,

at Partial submersions, less spray and conseguently less

drag might result than from the NACA 15-509 section

hydrofoils.

DESCRIPTION OF HYDROFOILS TESTED

The iWACA 16-509 airfoil section fs one of a series

designed for use at high speeds at which it is advantageous

to have a pressure distribution as nearly uniform:as pos-

sible.. The section is designed to have oofimum character-

istics at a lift coefficient of 0.5 and when .used as a

hydrofoil, because of its Pressure distribution, would be

e_pected to have about as high _ cavitation speed as is

possible for that particular value of the lift coefficient.

The tests of reference 1 showed the NACA 16A509 section

would be of some advantage in maintaining satisfactory val-

ues of the lift-drag ratio at speeds well beyond tliose at

which cavitation on the more conventional airfoils would

3

cause a large increase in drag. Conseq/u_ntly it seemed

desirable to employ this se,ction in the p'resent tests of

hydrofoils with dihedral.. Three hydrofoils of this sec-

tion having dihedral angles of l0 °, 1200 , _and 30.0were

constructed. In addition, three hydrofoils with the same_.dihedral angles but with .the section modif'ied to _give a

•S_arR .leading .e_ge were constructed. Sections of tl_es_e

h_(drof0ils, ,_normal to .the chord plane, are show:n in fig-

urQ, _i._.T.he .NACA .16- 50 9 section hydrofoil, with /zero di-

hed.ra_l,._which-was used in the previous tests," v/as ret-ested

to form a check between the two programs. '_All ._thesd.'-hy-

•.,drofoi!s had the same projected .arcs.,. that iS,- SO-inch

sp:an- and 5r/inch chord. They Were. rectahgular in plan.form

y(ith _qu.aro: tAps .and were machined from har'd bra-.ss and:

highly pollshod.: .

Each hydrofoil' was Suppoz.tcd by two Struts_ _` E._-c_:

strut was spaced 8_ inches from the center section of thehydrofoil. The struts are biconvex in section, approxi-mately 28 inches long, a nd..tape:red toward the hydrofoil.

At the point of attachment to the upper surface of the hy-

drofoil, the struts have a chord of 2.9 inches and a thick-

hess of 3/8 inch; at the top., .the chord of _he strut is 4

' inches and the thickness, is 3/4 inch, Thecenter l_n-e of

the strut intersects .th._upper. surfaceat the hal-f-chord

point.. T_rith' the. struts vertical, the angle of sttack of.the hydrofoil .is 80. •This arrangement (hydrofoil supp'erted

... from its upper surface• by rather large struts) is not' ideal

from censideratio_s of _po-ssibl_e interfere_-_cc effects.- This

..arrangement, h0wevez., appears _o b.e necessary-in applica-

tions employing-hydrofoils to.lift- a surf_.ce b0at.or a

seaplane.. .....-_, , - ......

TOWING APPARATUS ._ - _ _ " ....

to_,t_n_ carriage,-andA description of the NACA tank, ...._o.the'method of measuring carriage s._eed is give_ }n refer-

ence .,2._ _ .... _-.. .. "." ,!': -

.... - o-

The special dynamometer used in measuring the llft

and drag forces .is shown di_a_rammAtically in figure 2.

It is .of-.massive construction, because of the large forces

to be measured, and is supported by the main s-tructural

members of.the carriage. -This dyn_m0meter se.t-ul_ is, in

general, the sam_ as that, used for t!_e earlier tcsts_de -

scribed: in reference 1.. Changes were ma_de., however, that

improved the accuracy of setting :the deoth _nd a_gle of

4

] • attack, eliminating any,change i_ depth as the angle of

attack was shifted; Improved spring and da_shpot units

were constructed also. ,i i :_

. ,The assembl_ _ of hydrofoil an.& _supportin_' st,ru,ts is

bolte& to a! rigid floating frame in, which ,thOrpe, is _provi-

_. sion for. con tinuou, sly varying the angle of attack,and the

depth-of:.th.e hydrofoil within a wide rang.e. :This -,_floating

frame is _uspended by_,linkages from two hea_y cantilever

springs, the deflectio_ns Of _hich, are measu.red, by,dial

• gages .... Drag forces are balancedby:_ ,combination of dead

_:_e_ght_ and spring-restraint, the spring b_eing that of the

regular towing dynamometer.as describe& in reference 2.

. LSou_erbalances. are provided to minimize th_ effect of ver-

tical and horizontal accelerations. ,Guide rollers restrain

the floating frame against side motion.

•- . :, • P I_OCEDURE ' • _:- : i.'i • .... " ' ' J. -:

9, , ., 2 .

Th_ forcQ measurements were m_de at constant speed,

• .angle of attack, and,depth of,submersion. .±no range of

. .- speeds in most cases extended well beyond t.he speed at

•which cavitation s.tart_d ....At lo:,v angles,of:attack, the

range of spe.eds_extended to th.e:maximum :CObsidereal practi-

.......cable with-the apparatu;s_ , T.he dep.ths_ranged_ from 5 chords

: :below the surface ,.(mea.sUred,from the_ gua:rt.er_chordpoint

of the c_nter sectlon):to.p.artial submer.si.o.ns, with half or

mot@ of the hydro:foil ar.ea:out of:thewater,,. As.the angle

_- of attack: wa-s: changed, the, depth._.ofthe quar.t.er.-.,c.ho.rd point

at the center section was held constant. Ti'_re is;:,then a

slight error in referring to the depths of tips as constant.

This error is less than the sy',stematic errors involved in

measuring the depth. The angle of attack was varied from

-4 ° to 12 ° for most of the tests but was varied over a

• smaller range for tests at partial subme,rsions. The speed

at which ca vltation first app,eared _ on the upper surface at

each angle of attack was noted.

The s_pporting_-struts _ere tolwed-alone at: different

depths and the resulting measurements, of drag were•sub -

. tracted from the° measurements Of drag obtained _vith com-

_plete assemblies of struts end hydrofoils. ,The, lift

.... tares: of the struts alone,, measured in the _ same manner,

oroved, to be negli'gitl:e, for all conditions included in

the text. The drag taros of the str'ats-(f.ig. 3,) we,re

db,ductod to f__cil:itatc use of the data in designing

5

assemblies employing stru:ts :of :iower drag _ than th2 blcon-

vex struts.: Tl_e procedure used in'determining tares makes

no allowance for interference effebts, In most practical

applications, however, the same type and the same order of

ms'gnitude of interference will most likely be present.. , . ,

ACCURACY•., , , -

The accuracy of the basic measurements is believed to

be within the following limits: • •

Speed, feet per second .... .......... .,., . _0.2

Cavitation speed, percent ...... _ e i ' " ' _3Depth of immersion (below free water surf c ) •-_0.2inches ......................

Angle of attack, degrees ......... • . . . _O.1

Drag, pounds . • . _ ..... ±i.0 below cavitation _peed, ±5.0 with heavy cavltation

Lift, pounds ........ ±10.0 below cavitation speed::20.0 with heavy cavitation

i

As the amount of cavitation increased, the accompany-

ing vibration caused the force measurements to be less

accurate.

EXPERIMENTAL RESULTS

The experimental results of tests of hydrofoils with

the NACA 16-509 section are presented as curves of lift and

drag coefficients plotted against speed in figures 4 to 15.Similar results obtained for the hydrofoils with the modl-

fied section are not given in their entirety but are dis-

cussed later in this report. Each figure shows the varia-tions of the coefficients with change in speed, for constant

values of the angle of attack and a constant depth belowthe undisturbed water surface. The lowest speed at which

cavitation was observed on the upper surface of the hydro-

foil, for a given angle of attack, is indic_ted_ on the

corresoonding curve by a small arrow, With the test set-

up used, it was impracticable to determlne, th_ speed atwhich cavitation occurred on the lower surface.

Curves h_vc not been faired through every set of points

at constant an@le of attack with the hydrofoil partly sub-

merged, because the grouping of pointsrepresenting the

J

6

• 'various angles _af a.t,tack is ra.the.r-close., far, .some.cases ofpartial subm_.rs&ons and the' ac.c.uracyof the-measuzementswas not great enough to waz_ant _xpanding the.ordinatescal e.s• "

The observed forces are reduced to coefficients anal-ogous to the usual aerodynamic form:

'/ -L" X/CL lift coefficient(

drag coefficie'nt / ----D--L_psv - j.

CD

_here . .

L lift., pounds

;-- D drag, po,unds

•- p. .mass density of water, 1.968 slugs per cubic f'oot:-'::.-_" ' " f_or these tests

..... 'V" :": speed, feet pet second

' S ' ._ 9:rojBc-ted area of hydrofoil, 1.042 square feet for_-". .... these tests

.. ?

• • - -.

The Reynolds number (R = pV%/_) for any of the data

may be computed by using the Values

%

average absolute viscosity of tank water, 2.-25 X I0 -s

slugs oer foot per second for these tests

characteristic length, or chord, of hydrofoii,

0.417 foot

R = 36,500 V

The following additional symbols are used:

geometric angle of attack of hydrofoil measured be-twe.en chord, line at center section and free water

s_rface

chord of hydrofoil

. .Vc,'- :speed at which cavitation was. first Observed on the..... _.. upper, surface:, feet per.second

" !

DISCUSSION

Effect of Depth

The effoct of _ depth on lift coefficient for the NACA

16-509 section is shown in figur_ 16 for _-anglos of attack

of 0 ° 2 o, 4 o , and 6 0 and dihedral angl_s • oT 0 °, I0O, _0o

and 80 °. This figure presents curves f_nired through

point_ taken from the faired curves of f igurc_ 4 to 15.

Points are also shown r_prosenting the f_irod data for the

section havin_ a sharp leading edge.

The flow of water Over a hydrofoil at depths greater

than _ or 5 chords is apparently not iiifluenced by the

surface of _ the water, and conditions similar to those for

an airfoil orevail.

At lesser deoths (for example, 1/2 to 4. or 5 chords),

the influence of the surface of _th_ water is evident from

the decrease in lift and the increase in cavitation speeds.

_s the hydrofoil, while mo_vi_ng _vith a cor_St_nt forward ve-

locity, approaches the_s_rface, there is a i_eduction in

the mass of vlater flowing above t_h__ hydi_ofoil. Thls change

causes a reduction in the _a_0so_lute value .of the negative

" pressures on the upper, _surface of _the _hydrofoil and results

in a r_duction in lift. ' The _ roduct_ion in the absolute, val-

u_ of the negative prsssur_ rcq_ui_es t_hat, for cavitation

to appear, the s_eed_must be greater for the lesser depth.

-(See fig._lT.) The method of computing cavitation speeds

given _n reference I r_akes no allowance for this effect

of decreasing deoth.

At very shallow aepths (about 1/2 chord_, a more or

less sudden breakdown of the. flow over th_ upper surface

occurs. Far th_ NACA 16-_09, or the modifi_d sharp-nose,

section at an angle of attack above 4 C, the breakdown of

flo_°¢ Occurs near the l_adln_] edge, th_ _ater separating

almost completely from the upper surface, leaving nearlythe whole chord ventilated. At low angles of attack, the

breakdown of' flow is les_ su(iden • and occurs at _ le_mser

depth. The breakdov_n of flov_ may occur inco_nolet_ly and

unsymmetrically spanwise, its spanwise extent apparently

depending on the augle of_ d_ihedTal _and on the roughnessof the surface of the water. Either smooth flow or sepa-

rated flow over the up pe_r surface may occur at a_given • op-

erating condition, and _lternation between the t_o t2pes

of flow may occur. (See fig's. 5, 9_, 13, an_ 14.) When

i

separation of the flow from theupper surface is definitely

established, the chang-es of lift and drag with ch_ngo in

angle of attack are very small in comparison with the

changes that occur when the flow is smooth over the upper

surface. (See fig. 18.) When the hydrofoil approaches

the free surface, the use of low an_les of attack appears

desirable in order to zeduce the severity of the transi-

tion to planing.

Total .projected areas wer,e used in computing the coef-

ficients to facilitate use of the data in design, The

abrupt change in the slope of the curves (fig. 16) as the

tips emerge therefore represents an abrupt change in total

lift and not necessarily an abrupt change .in section char-

acteristics. Fi.gur6 16(c) shews one-clot of c.oefficients

based on projected area of the submerged portion of the

hydrofoil.

Comparison of Tank. and Wind-Tunnel Tests.

.....Figure 19 shows .a compar_i.so.n of test results on the -

NACA 16-509 section from .tests in the NAC,_. t_nk and the

24-inch high-speed tunnel. The results of tcst. s in the

wind tunnel as given in _ref.crence 3 werc-,co.n_rcrtcd to an

aspect ratio of six for this _comparison. The drag coef-

ficients measured :in the tank. an,d, g.ivc.n_ in r_:cfore.nco I

included stru,t drags;, consequ.ent.ly, thel strut .tares were

deducted from t-he published values fo,z..the purpose of mak-

ing this comparison. The data from _th.e pr_slen.t :tests were

for t_ e zero-dihedral hydrofail; at _0. fe_t per second

The agreer_ent between the two series of tank tests is

good. Agreement between tank and vriz._d,:bunnel tests is.

reasonably good except for lift at high:.anglcs of attack.

One reason for the discrepancy, in the lift .curves is un-

doubtedly the presence of the relatively large struts used

in the tank tests, The agreement is, on the whole, good

enough to suppozt the belief that for preliminary design

invo,lving hydrofoils ope.rating a.t depths greater than 4 or

5 chords, and at low speeds, wind-t_nnel data may be used.

Effeo_t. of Di_hedr'al

The effect of dihedral .is shown in figure 16. The

highest dihedral angle _sed,. S0 O, gave the hi.ghest lif_t

forces at. partial s_ubmerslons for, a given emcrsion of the

tips. This result_ is undoubtedly due to the greater im-

mersed area and the greater average depth of that area

for a hydrofoil with high dihedral operating at the same

tip emersion as a hydrofoil with low dihedral. The changein lift from complete immersion to zero immersion Is more

gradual for the hydrofoil with high dihedral than for a

hydrofoil with low dihedral. If the ides is to secure a

relatively gradual drop in lift as a hydrofoil emerges

from the water, as in a flying-boat application, as high

a dihedral as is consistent with other requirements appears

desirable.

In figure 16 the points plotted at zero lift coef-

ficient for each angle of dihedral were not obtained exper-

imentally but were obt.ained by assuming that the llft would

be zero when the quarter-chord point of_ the center sectionIs at the free surface of the water. It is probable that

some planing lift is obtained from the lower surface atthis location of the hydrofoil but it would be negligible.

A summary of the effects of dihedral is shown in figure 20.\

Effect of Shape of Nose

The effect upon lift and drag of sharpening the lead-

ing edge, as shown in figure 21, varies with speed and

angle of attack in such a way tha_ neither section appears,

in gen_eral, to be definitely superior tO the other. Con-siderably more data were obtained than are included in

this report. Those in figure 21 appear to be typical ofall the data obtained and a more thorough analysis of the

effect appears unjustified except for applications some-

what more specific than may be assumed at present.

The effect of sharpening the leading edge upon the

volume and trajectory _of the spray for partial submersions

was not deter_ined quantitatively. During repeated obser-

vations of the spray thrown by the two sect ions,_no slgnif-

icant differences appeared.

Effect of Speed

The effect of speed on the characteristics of a 16-509

hydrofoil is shown in figures 4 through 15. Two principal

effects of speed may be noticed: "first, there is a limit

to the maximum hydrofoil loading that can be developed, at

the higher angles of attack; and second, a complete loss of

l0

lif.t at low angles of attack (below 40) may b e experienced

at iligh speeds wit'h this sec.tion.

"' The limitation on the maximum lift is a result of com-

plete upper-surface cavitation. (See fig. 9.) This re-

sult verifies the results fndicated in figure 3(d) of refer-

ence 1, At the depths used in the tes,ts, this maximum is

approximately 2200 pounds per squ&re foot; that is, approxi-

mately equal to the sum of the atmospheric p rGssure and the

static_pressurehead of water ab0ve the hydrofoil. (Lower

surf'ace lift may Continue to inoreas'e with speed.)

Loss of lift at low angles may be due to cavitation

on the lower • surface of the hydrof0il.' T_e speed at which

cavitatibn first appeared on the lower surface could not

be determined because the lower surface could not be seen.

T'he presence of low-pressure areas on the under surface of

the h2ErQfoil was indicated by f_int st.re_mers of cav'_ta-

tion bubbles., which could be seen le_ving the lower surface

at the trailing edge during tests _'t high speeds and low

.... ahgles Of attack. If a 16-509 section hydrofoil is used

on a high-speed surface craft, it may be necessary to avoid

the use of angles of attack less than about _o. This ef-

fect of speed up'on the lift at low angles of attack appears

more striking when the total lift in pounds (for the model)

_:rhther than the lift co_fficien.t is plotted, as in the

das'hed curve of figure '13. If the loss of lift at high

_ 8.peeds and low angles of attack is caused largely by cavi-

tation on the lower surface, a section having less camber

than the 16-509 section may prove to be much better for

some applications.

Th_ biconvex sections use& for struts in the present, _ °- o

tests, while requiring relatively simple machining for

manufacture, evidently are not the best sections for use

in supporting hydrofoils below a seaplane or surf/ace boat.A better form such as the 16-009 section (sSr_ninetricalo 9

percent thick) designed to have L a nearly flat oressurQ dis-

tributi0n at zero lift would be better. Also, the form of

intersection of strut and hydrofoil used in the. tests may

be improved upon. Observations of the cavitation that ap-

peared during the tests at high specds _nd low anglos of

attack were of considerable interest in showing the exces-

sive drag contributed by the struts and by interference.

Cavitation first appeared in the region of i_[terference be-

tween struts and hydrofoil, next on the struts, and lastly

on the hydrofoil itself. In the development of an efficient

assembly of hydrofoil and s:upporting struts, observations of

ll

the cavitation at high speeds should prove very valuablein rapidly locating the regions in which modificationswould be desirable.

CONCLUSIONS

The conclusions listed below are based on tests ofan assembly approximating an arrangement foz use under aseaplane or a surface boat.

1. At depths greater than 4 or 5 chords, the influ-ence of the surface of the water is small and a hydrofoiloperating at low speeds will have characteristics similarto those of an airfoil of the same section. Preliminarydesign estimates, including estimates of cavitation speeds,may be made on this basis, in the range of depths betweenabout 4 or 5 chords and approximatel_r 1/2 chord, lift anddrag forces decre_se and cavitation speeds increase as thesurface is approached. In the region of very shallow im-merslons (less than i/2 chord), sudden changes in lift arelikely to occur and the exact conditions under which theabruot change will occur cannot be safely predicted.

2. For applications, such as a seaplane, in which thehydrofoil must emergQ from the water, it appears that largeangles of dihedral (80 °) and low angles of attack _ill bedesirable, as they afford smoother change from comDletesubmersion to zero submersion.

3. If a shard leading edge seems desirable for some

reason, no gre_t penalty in lift or drag is necessarily

paid for a slight modification of a section such as the

16-509.

4. Two major effects of speed may bo no_ed,:

(a) A limitation of total hydrofoil loading

under conditions of complete upper-

surface cavitation. This limit is ap-

proximately 2200 pounds oct square foot

for depths testod (25 in. and less).

(b) Loss of lift on the 16_509 section at high

speeds if low angles of attack (below 40 )

are used, probably due to lower-surface

cavitation.

IS

5...-Additional tests ..would be _.esirable.to .-investigate

the charecteristi.cs-of ..hy.%F.ojfo.ils.at h_g.he.r .SD.eecls and

.. e___._.e_.ct.of modify--vith lower ;cambers and _.0-._nyestig fat.e"t,h.e ' _

ing the section of the struts and tl_e foTrn Of the !rite.r-

section between a hydrofoil and its supporting str.uts.

Langley _iemorial Aeronautical L'aboratory,

National Advisory Committee for Aeronautics,

, Lan_<ley Field, Va.

REFEREN CE S

• 2.

,i__'•__i_.:[_}_,ar:dl,Kernn_eth E. , and Land, Norman S. : Preliminary

_ _"_?__'<"_-_ _Te.s,ts in the NACA Tank to Investigate the Fundamental

<_.i_T_r'_sC6_'_t, Starr; The En!_rged N A.C.A. T_:nk,• _%% Some

" ._. ,- of its Work. NA.CA TM.No, 9i8, 1939. .:- "

3. Stack, Jol_n: T_sts of Airfoils Designed to D_!ay the

Compressibility Burble. NACA R,ep. No. 76_, A94_.

.i..... •

ITAO_ Pig. I

j_J

16-509 nose -7 ./_.I/ /

/ --.- Sharp nose/ /

,//

%

Enlarg_& nose sections

hA_i 16-509

Fi_ro I.- Sections of hy&rofoils tcoto_.

L=758

A HTdrofoil

C f/O_ting frame

Z_ Lift _/_,/n_X .D_hlbot_

F _ial _aae$G l_7q ¢oun/erwe/jl_tjH Re_ri_tance dyn#momete:d C_a/'_ _/:-a_leyer,,/O:l K,K Coa:_e dt'a_ wei:h/s "

/ I "/ /I I .D i :_

l

I

A _

N

National Advi _'7Com_ttee for Aeronautics

/

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JB

\A

Fig. _..-Dtagra_tlc sketch of hydrofoil dyD£mometer.

\,H

o

ooLO

..L _-

I

NAOA

_.0_o

0

'_ ILl_0C

0

3

0

0

_ .02

,_ --

Qo )1

3

;2, _,

0

f-A A

s_ _.A -,4

i I I_,A.( ,A. _ANK

Na_ion_ 1 Adlriso]mmit_.ee or Ai_ron_

/

Fig. 3,21b

mtic__

/

/

d',_ \

I _ __

zo _) 3o qo 5o 6o

J!_i., / !

=-_

7O 8O 9O

Speed, V, fps

Fig. 3 .- Tare drag coefficients for struts used in tests.

_9

E-

----4

: _ • - _ .L ,¸ .

'iii'i::_:_i!_¸..... i...... • 4 ¸ -. i • " _

J

L-768

-. _. -

1.0

.9

.8

.7--

F !

i(I _ _a_

/6°x_I /

__-a

.6-- _i_'-I--_---_-- _ _

0"-_-5--

0

u .3

.2

.I

t L 1 lI

20 30 _ 50 60 70 80 90Speed, V, fps

Fig. 4.- NACA 16-509 section hydrofoil.

.2O N_tlo_al Adv snrw

[ Col_niltee fo] Ae 'onautlq:s

•12

o. 08

_H

8.06

.0L_

0° dihedral.

/+

J t -Mde_"

• / q.x lq-+6,_ 16x

/

/.

/ot//

o+ J I , _ *---_ --

o'k_ & JL,. !.o-_

i I I _'2o 3o .o 5o 6o 7o _ 90

S_ed.v,_psDepth_5 inches to cl_.

,,. \

<i

0

',,,..

I ,,,i=.

iO

©.

.fI/"

0_ 0

/]/

!f

I

i t+

t,

0

C_0

,J

/i

d d

00

0

_o

/

I

0

&

ill

• " _ i._ _ _,,ii _ !! ii.,,¸

> -

..k - .

0 ___

"I

0 P/ -

-- p-T_ .....

0

0

o0

o

m

_ _-- _;_-__ -

_I_ _-

--l .....

I

I¢

..... --4----

!

I

-.4 _-

Lift coefficient, CL

l

-- _--4-- --

i

q J _1

.... -Jal-

/

m __

m

m _

I

I

I

i

_ t--'- --

I

I

__ +______ __

I

Drag coefficient, CD

:4

|

W

\.

-- m

__ m

y;-

I

1--4-----'--

l___

t---

+____

1--

4---

/ a;

.-- I I

/\

--FF-;I__ _4 --0-----

• i _

-- --__ -____'_ -- t---- --

_-.-- _._

_.,_°

--4-- _

I

__ _+_____ _

__J__ __

¥o_

01OO

L-758

.3

.2

.I

oO

_.2

00

0

.2

.1

0

L

I

"----.__ ._.

L3o _ 50

_,+

c _

Oo 6"2+ 8__

6O 7O 8O

Speed V, fps

o r _+_¢'Z._._x _-

a_ 30 _o 5o 7o 8oSpeed V, fps

I2O 3O _0 5O 6O 7O 8O

Speed V, fps

Fig. 8 ,-NACA 16-509 section hydrofoil. 20 ° dihedral.

o

.-4O

b.4

00

.06--

.O4

.02--

0

.04

.02

_L ' n I III

)o.

--_ jo_._-_Z;7-_

20 3o uO

F" '"---_×

50

,_ I±l--T--_._,

_,f.,

20 3o uo 50

.o.r

.o2

X + _ m

I I20 3o _ .50

Depths,C/_ at tips above water line,

N.A.C.A. Tank

National Advisory

6O 7O _oSpeed V, fps

e ¢

6O 70 80Speed V, fps

I

°i

6o 7o _oSpeed V, fps

.t46, 2.7, and 3.7 inches.

co

L-758

1.0

.9

.8

.7

j/+l

___-L

i_ _"-/o_

r.D

..6 /.__i_._ ./ \

Q

t "-4,

• 3 ---2q _"_ _ + _- ..---..___- "_'*--u _.

_e

Y.i ----,_._-"- "7" --

3O qO

Fig. 9 -- 16-509 section hydrofoil.

.2O

.is

.16

Cf_f

A _ A rT'_'_lr

Na'_ion_l )dvi 3or__It",ee For Ae_ ,nm tlr._

\ .06xx

\

.0_

_' \ .02

o70 80 90

Speed V, fps

C:I0

" i/ /.io

O _-_

•08 --.._ v I /

,_'__ _ _//

(x: de__u, v '6=-2 _ 84)0 e 10"2+ 12eq.x i_+

-- ; -'_ ,#_

_ __L.w_. I-_,,=! _----:_ __

j-2O 3O _0 .5O 6O 7O 8:) 9O

Speed V, fps

200 dihedral, e/W tips at water line.

• • . -

1[,-758

":_ ...."

. _ .J_

-:- -7 • •

1.0

.9

.8

.7

,-]

ID

C_,¢g00

._

.1

lO',d

()

/

x _ w

4,0-

o.o.__ _- -_ r-_._..."-4

20 3O L_O 70 SOSpeed V, fps

Fig. _0 - NACA 16-.509section hydrofoil. _D° dihedral.

._0

•18

OOZ

,16

e-s0

QO_3

Q

.lt,

.12

I0

.08

.06

//

//

6"D -----m.-._ ___a _

I

I-'i50 ¸ 60

Depth _.5 inches to C/W at tips.

Nal_ior_iti_ee

C.A Tsal _dvJfor Aez

o_ , deg __

0 •X

6_S_i012 e

7o SoSpeed V, fps

nkSOl

ona ,tic

0

I

m

o

o

0

0t-,,-

o L

B0

B

c+

L_

0=r

0

4=

m

W

7

,a

/

/-/

%/

j" /

oI

__ _ \_

• ,.

t_ _.

Lift coefficient, CL

_ •

/

o

+

+

/

Jx j

I

/7/-- ,

,u 1 _-

B i

\r

1.

_ b

.-,..--

II [

e.

\

i

_,.@

Drag coefficient, CD-• e-

i

",,1

L..768

1.0

.8

,7

_..6f..%..

0

.,.4

_I .W.

.3

,2

.I

-,i

I

V, fps

6O 7O

t

FiE. iE.--NACA 16-509 section hydrofoil. 200 dihedral. Depth 19.5 inches to ¢/_t at tips.

C,-!

i IIL_;_,_ i

;_, , ii i:_

_iAOA

|

, ,,,-O |

"t

+

C2

H_

I io o

d_ Id

x

. _ -.hi--

11

XD

i!)¢), m

p

E-

ra

. -- +_.s

i IF, xl_

_-- -

i!

+___

+

04 _ 0

"I0 'q.UOTOT._eoo "TST"I

-8

+

__ > _.,,.-F--_

. -4 e_A

____=:__.__. _-

_. ......... m-_.,_aJe- ---1

_x___+

)<

.4 0Od

ri o 'q.UeTOT,_,,T:_ooq.,TT"I

S_

09

o_., ..-,

,.8

o,"

,.-I

¢,,,

8O-,

O

O.

e.-I

_D °

0

I

i

Fig. 1_

• :L..

• h .

- , ":z k.b,_

L-758

_Spee_ 8OV, fps

Flg.l_ .- NACA 16-509 section t_drofoil. 30 ° dihedral.

r I i

//

Depths c/u, at tips a%_ter l_n_.

I _N_A_ C A

' Na hior_aiC_ ml t h_elf_P Ae_n_tl _i

I ]

_, deg-_v _x --

-2 • 6" --0 ® 802 + i0_

12

po _o_v, _'p_

#,.a

L-758

J b j,V

v_ j

, • = J

•8 -- --8= ,.. __

•7 --_"_'_i _'-_-- "

.3

2"-'--

.e,...,,

.2_Z?_..I =,---,----- Ii,.---- E.--- ....._

.1

0

,f_,._- --v --..._ _

. P "_m__

/6.3"

_L--

,....

,.,,,, \

20 3o _o 5o 60

Flg.J_ .-NACA 16-._ section hydrofoil.

7O 80Speedv, tpB

30 ° dihedral.

r_

O_4O

Q0O

.20

• 18

.16/

J/

.12 /

lo- '_ '/

.O6

_t/',lrf

'.A.

Na' ton•n4 _ ee

zl t dvt _r_

.06

i

/

/1/

", dQ --•-._v 6 ._ __-2L 8 $

0 e IOA_ __2+ 12 •_x 1_÷ .__

16x

Depth,16._ inches to e/_ at tips.

oR

ka

/ / _ ii_ % i_ i_

L-758

.32_D

U

C 2

-8

I.-, 5

" 2t.)

C.%-t@

o L0 •

/-i8 _:8

}

i

,

i

/

-6

/30_./ iI_

x� /,I

/;/

/

J

i/

//

/

/

-2

Tips out -----

I

.,....

/

II

i

[E

II

4

//

I IDihedral

0o

i0o200

30o

16-5o9

0

X

I_I l_I

//_._.._..I

/

I I (tailed points)Sharp L. E. _CAT_

Cr_nitt eel fo_-_

_ ._.._._..__.__...____...._..._...._...._22.._ __--_....

[so]_

i

!

i --

I

!

2 _ 8 i0 12 i_ 18

!

v - 9D_p5I L ,_ I

22 2_

f/

/

2 _ 8 I0

Foil submerged

_, -Z------_i_-----__--__________-- __.-,_--- ________

Depth of clW at tips, in,

Fi_ 16a, b.- Effect of depth on lift coefficient.

i v 5olf_.

_ 22 24

g_

O¢D,.4

.=

ZZ

sd._ 09 = A

.%_ =,10l

O_ _T

II

•F_nu,+uo,.9"_ueIoI,_]eoo '_J:_Tuo q_dep _o ",,oo_.,-"S-"oSl "s'..4

•u_ "=_.1.'4'_s _/o _o q,_d_

9I nT _T OI

.._..--I "-''" I

.. I

I

!pe_,I_uJ:l__ [_o$ I0

JI

//

/ /i

// /I

fd'

j /f

.I - _i_ "j

j-

_no sd_z--------__- t_- 9" _" 0[-

I/ .* / T"/

,._ ,_ /I /t( _"

/-_/I/ £"

/ /" I/ l_p_q,,o,_,--

"_ -_o._d_op_ "O-

e

t-'

0

Q

t-'

V J'/,_

p_r m/¢

V.T. rmrs(_uTo# P_TW_)

I)¢

] 60;-9'[, I I

i Ioo;

oOtoO

t_,zpeq1:(lI I I

gg&-'I

L-758

k

nq

Dihedral 16-9090o

i0o o

_o --:

(_,7eJ/_'_/_) I_.A.,:.A. TalkSharp L.E. Nation_ll Idvilcry

Cr_v,ittee 'or ter¢nm_hin,

X.

o

_D

0

0

/

//

/X

/

,-8 -6

/

// i

/

t i i

,'ill

/ lj

-_ -2

/r

/{-/i

f%

i

i

i

II

//

(a) = -' 6_-v = 9o fps.

iI

0 2 _ 6 S i0 12 iw 16 iS 20 22

----Tips out IFoil submerged----Depth of c/% at tips, in.

Fig. IGd.- Effect of dt_bh on lift coefficient. ConGJuded.

24

L-758

I

I

_i L'x ---c/_-

•_c/g tips 1 _ .

in. below/<_k_

0

o3o 1

--I

7o

0

0

Fig.lf

i0

I 7 l! N.A.

G_m_ _i°zi T __ee._

tips at W.L.

tips 9.5 below W.L.

I

C.AL T;_nk t'_al Edvlsorlf_ _ ___ a

I

tips W.5 in. below W.L.__

-,p-

iI

I

2 _ 6 8 I0 12 14 16Angle of attack_, deE•

.- Effect of depth on cavitation speed. NACA 16-509section hydrofdil. 20° dihedral.

.......7-- --I I19_i) NACA Tank

) Depth = 25 in.

_-'is "9I--i _ _ NACAI24 --1938)in•tunnelqO1] [_ _'_6g/ "d//1 Tests.R.N.-l.W x I0 --_/

¢

-2

M

to,9

6:>

I)

90.°

.,-.B

-_. t,-,-_.7 _ /-CL\\Z \ i

o /\,,/ ,-_.12_.6 \\ , /

°@° / X<,/\_ \ /.10o.5 / '"

-_ ¢. ' vc _'

.os ""-_7 -" .... t/ ,

06 / /• . / -_ .p.-

// // CD _,----L/.'/ "_'"_ -"

,iI_ i ;// -I

'/,.' /"_ N_A C_J_ T;nlc/ .: /. f._

- _ i I_ C,,_,',m'l tlt.ee fnt', Ae_ ,nn_ It.t

n0 2 _ 6 8 i0 12 I_

Angle of attack,_,d¢KFig. _9 .--Comparison of NACA tank and wind-_unnel

tests on 16-509 section foil• "_

L-? 58

-1.C

c

-.S

o .7

G)

-* .6

))

_ .5

-.2

-W -2 0 2

_A_ _.A T_nk

Na 4on_l _visormit ,ee .?n_ A_r.nn_j,t_C2

Fig. 18a.

/c/_ tips 19.5 in. below_i

f

c/_ tips 9.5 _n.bllm_/// / /_

w.L. _ _/, ///

W

//

A/

//

/_, / in. below W.L.1 I

/r/ ,_"

._ / _-0/_ tips at W.L.V/

/

, /

/_ tips .W6 in.\ a ove W.L. _

fc'/_ tips 2.7 ir

" ab tore W.t.

_ _c/% tips "h7 i_Iabove W_ L,6 8 I0 12

Angle of attack, or, deg.

Effect of depth on llft coefficient. NACA 16-509 section hydrofoil. 20 o dihedral. _O fps.

;.A.13.A. T_k

Na" ion_Ll Idvi _or_Go, nit' ee or Aer _nathim,

16

c_ .1_

__ 2tD

oo 10

//; /h

C/_ tips 19.5 in. / /

below W.L. __/I I

clW tips 9.5 in. _ /._ below W,L._

C/% tips %.5 in. _f /

below W.L.--%/4 ,._ _ _cl_ tips at W.;

" _ -- C/_ t ip 8 " _ in..'_ _ a_oveW.L.

_.-c/W tips 2.7 in_02

, ,,ov.,.,._cl_ tips 3.7 in

_ .7..._ Y abo_e W.L._

0 2 % S i0 12

Angle of attack, V=c_, d_tg.

Effect of deoth on drag coefficient. NACA 16-509 _

section hydrofoil. 2_ ° dihedral. UO fps

L-758

C_

-L

• 2O. 10

,16 .8

c __,.o_ ..

_.OUP .2

0 0

I

!

\

0 w S 12angle of attack,_, deg

Lol l,/c _

//. /// c_

/

O _ 8 12angle of atta&k,_,deg

2

1

/i\J

/,-/

.Z) "17

.8

[.)

{. 2_.6

_"_7 /

• _-q" 0

I

\\

\

\., \

\ \\ \

2o'_'/_#m/, I I I

8 12an_le of atta¢

/ I

<_/_///

8 12angle of attack,_, dee

D

_5

LO

5

I

i t i

I

t'_./\

//--

./_u, ,)

.2O 1.O

• 16 .S

_D r,D

Z.z2 "_ .6

!.)

'_._ _ ._,° _

-- 0 '_

/¢-

//

Naior_,l _dvi,o_ [Ct_'r nil.' ee !ro_-!ker ,,', ._._!c,_

I\ \i \ \ .

i i i

' D,, .#._.a.< l;,_ _W"

cen _e_ secfi_,_

_'/_e/_ -

I

I Is 12

angle of attack,a, deg

/-¢

/?/

s-

I8 12

angle of attaek,c_, deg

Fig.20 - Characteristics of 16-509 section l_drofoils with dihedral angles of 10,20, and 30 degrees at two depths. V - _0 fps• p_

m_

0

+,

L-788

.S

.7

.6

_,5,ID0

¢.)

.3

.2

.1

0

"-.t

2O 3O u,O

Fig. 2/a. - Comparison of test resultsc/_ at tips.

NalComnitl

[.A.3.A, Tm tk

ion_l dvi _ory

N"

"" ,-.

\\

x\

\7o

\\

90 \

Speed V, fps

/

-_-L'/ /

_-___ _.-J/I

=_-_,- __-5_-bo.2_ - ____-_._-- - -- =-=--'=-_:_.

20 30 qO 50 60

200 dlhedral.on normal and sharp leading edge hydrofoils.

_Normal leading edge.... Sharp leading edge __

Depth, 19.5 inches to