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NATIONAL

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IJ?VtiST IGATIONS

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TECHNICAL ‘imtomiimuhis

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ADVISORY COMMITTEE FOR .-4ER0NAUTIC!S ,:

NO. 892

AND TESTS IN THE TOWING BASIN AT

By C. Cremona

GUIDONIA

fiirHauptversarnmlung’ der Lilienthal-GesellschaftLuftf,ahrtforschung, Berlin, October 12-15, 19343

.

WashingtonApril 1939

.. !.,’ ,.. . . . .. .

,..

NATIONAL ADVISORY COMMITTEE

TECHNICAL MEMORANDUMG-

FOR AERONAUTICS

NO. 892

,,, ,, ... . ...,:, INVESTIGATIONS AND TESTS IN THE TOWING BASIN AT GUIDONIA*

By C. Cremona

I. INTRODUCTION

The Hydrodynamic Section forms part of the researchequipment directly concerned with the development ofItalian military aeronautics the laboratories of which aresituated in a locality near Rome, bearing the name Guidonia.

The principal object of the Hydrodynamic Section isthe investigation of the forms and the study of the be-havior of the hulls and floats of seaplanes..

Naturally, side by side with this experimental work,corresponding theoretical investigations are conducted forclarifying and defining the still somewhat vague conceptsof hydrodynamics, which even today must be considered asthe %ranch of fluid dynamics in which the most uncertain-ties and unknowns are to be found, and that still is themost difficult to express by precise laws and simple for-mulas.

The experimental activity of the section has beenoriented so as to obtain results most nearly approachingactual conditions and most adapted to the special techni-cal requirements of the seaplane designer. In particular,as regards tests on the hulls and floats of seaplanes, forexample, the system of testing models at specific scaleshas been discontinued because it could offer only the al-ternatives of acceptance or rejection, acceptance beingsubject to the particularly determined and restricted con-ditions of the designer, It is impossible to predict thebehavior of a hull even if only slight changes are obtainedin load and trim, however great the competence and l~artis-tic intuitional of the designer. In conformity with otherhydrodynamic testing laboratories, nondimensional coeffi-cients have been adopted, defined as folloWs:

*“Le Ricerche e le Esperienze Presso la Vasca Idrodinamicadi Guidonia.11 Reprint of paper presented at meeting ofLilienthal-Gesellschaft fflr Luftfahrtforschung, October12-15, 1938, Berlin.

2 I?.A.C.A. Technical Memorandum No. 892. . .. .. ..’. . ,.,.,.’ .,.,:

Load coefficient..cQ ~.’Q/p~3

,,. . .

,+CR .= R/p ‘b’3 “’;’Resistance coefficient, -,-,.,,

‘Speed”coefficient. ‘G~ =v/fi:

Moment coefficient Cij = M/p b4

where p is the specific weight of the water and b areference length of the hull (beam at step).

A model hull is tested at a series of loads, Q, andat various fixed trims, $, and at speeds, V, and theresistance” and moments are obtai,ned. A series of tests oftliis kind requires about 200 runs of the towing carriage.

iV-nen, as a result of the designers study of the non-dimensiontil’’”hydrodynamic curves, the hull assumes a finaldimensioned form a dynamic model is constructed at suit-able scale. The purpose of this model is to overcome theuncertainties that result from the combination of the hy-drodynamic forces on the hull, the aerodynamic forces onthe wings, the interference effects and the inertia ef-fects from accelerated motion. This model is constructedwith corresponding weight and distribution of ,mass, withmovable “surfaces (flaps)’ and in some ,cases with movablecontrol” surfaees (elevators) (fig. 1).

. .,By towing the model at variable speed from zero up.

to the theoretical take-off the reliability of ‘the assump-”tion{ inade and the degree of appfoxi.mation of the calcula-tions’ may be checked. It is furthermore possible to de-termine unsuitable constructions in the general. structureof the seaplane (attachment of.t’he wing struts to thehull , position of the horizontal tail plane, position,ofthepropellers, etc;, in relation to the.s~ze of the wave.,formation). “ . ~~ .;

. .,.

II. EX?ER’IMENTAL METHODS.. .

.’The .towingtankat Guidonia ,wa.s,designed on the’~a’s~sof the above considerations,... It posse.’sses two towing’”car~riages, each, of:,different characteristics and designed fordifferent purpos,es.,running over a tank.’4SO.@eters (1,518ft.)long.i6.meters .(.19..8.ft.)mide.,apd 3.’5Qmeters, (11.55ft..) db:e.y.

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N.A. C.A. Technical Memorandum No. ’892 .3

h,A) The Bridge !Cowing Carriage. ‘ “ “

p>9 ,. ,...”,,,=,.~ “- ‘ - ,,,;

The first of these of “bridge-type’”cotis’truction:(ref--erence 1) has been designed and built so that in addition

; to tests on seaplane hulls it can also be used for tests)’~

on models of ship hulls partly or fully submerged. (fig. 2).

The metal structurbis of electrically welded steeltubing (airplane tubes) the tubes being covered with afairing to reduce the resistance to motion and the aero-dynamic disturbances produced by the structure on the mod.

> el. The carriage rests on four wheels fitted with pneu-matic tires to give the necessary adhesion in starting so

t as to attain “high speeds in the shortest possible distance.Each of the four wheels is separately driven by a directcurrent electric motor. The measuring apparatus is locat-ed at the center of the carriage.

The total weight of the carriage ready for testingand complete with crew (six persons) is 6,000 kilograms.17ith a power of 100 horsepower, the carriage can attain amaximum speed of 20 meters per second and has a minimumspeed of 5 centimeters per second. The intermediate speedscan be varied in small steps.

B ) The Side Towing Carriage.

The second carriage, of a new and original design, isentirely enclosed in a fairing and runs along the side ofthe tank. It has one or two parallel cantilever arms whichextend to the center line of the tank and at the end ofwhich is suspended the recording apparatus (reference 2).

The carriage is constructed of a large steel tube towhich are electrically welded other pieces of tube for thesupport of the cantilever arms and the flange on which ismounted the single direct current motor which is coupledto the drive wheel. To attain the necessary adhesion, thiscarriage also runs ‘on pneumatic tires (three wheels). Witha 100-horsepower motor it can reach.a speed of 40 metersper second within a minimum interval of 10 seconds, inter-mediate speeds being obtained by Iine regulation (fig. 3).The weight of the carriage when fully equipped (2 persons)is 2,000 kilograms.

~) The Catapult Installation

For special experimental requirements, when it is de-sired to attain very high speeds in the shortest possible

4 N.AOCCAO Technical Memorandum No. 892. . . . ..”’ ..

t ime , the Section can avail itself of a compressed-air cat-apult , With a maximum pressure of 50 atmospheres, a speedof 100, meters per second may be attained.

~ b)”The Auxiliary Laboratories ~,’. ..

. The equipment is completed by machine rooms for theconversion of electr~c energy, research laboratories, of-fices, storage rooms; “machine shop, records, etc.

. ..III.” THE DYNAMOMETER

Particular care and spec’ial attention have been givento the solution of the problem of the dynamometer. Becauseappreciable progress has been made in tnis field,’ I believeit of interest to call attention to the development inItaly and I hope to be able soon to present the results ofour studies.

,.

AS has been said above, in order to present the re-sults obtained on t’he hulls in’”nondimensional form, it isnecessary to make the tests at fixed trims. Under thesecoziditions the measuring of the md,ments “is very difficult(and hence only approximate) because it is practically im-possible to bring the scale back to the zero position dur-ing the test. It is necessary to utilize the deformationof an elastic material in order to determine the value ofthe moment. The deformation although’ reduced by suitallemeans is nevertheless large enough to bring about a changein the trim o so that a careful measurer~ent ‘of this an-gle is necessary.

It is known that hydrodynamic tests do not have a con-tinuous and stable character and hence in order to measurethe angle d, “it’is necessary to record it. All this ap-preciatily complicatest hecozistruction of the dynamometer,the plo’tting of the” curves, and the computation, and makesthe results very largely approximate. It was thereforenecessary to find an elastic inateiial that could indicatethe forces to be measured over a sufficiently large range(from O to 100 kg) with sufficient sensitivity and withoutappreciable deformation. Investigations were thereforecon”duc’ted by Prof. L. Crocco any myself on the methodsavailable for this purpose but all had to be rejectedeither because of the poor sensitivity to small loads, be-cause of the difficulty in” calibration, or because of thedelicacy of the measurements which took on the character

. . ,,

N.A.,C..A. Technical Memorandum No. 892 5

of laboratory operations (reference 3) poorly adapted to,s= . the us.e,,o$the. no_t ent~rely technical personnel available

at Guidonia.” ,., ,..,.,.,, --

The choice fell kpon a new technical method that firstappeared in Germany and is known today all over the worldand isused to a large extent also in Italy, namely, ~bel-lows-type springs. When the latter are filled with liquidthey assume an extreme rigidity and when connected to amanometer tube suitably proportioned possess a truly ex-ceptional sensitivity capable of indicating a change ofonly one gram when loaded to several hundred kilograms al-though the, load may be rapidly varied (fig. 4). At maxi-mum load the deformation can be reduced to a few hundredthsof a millimeter if the dimensions of the spring body remainwithin fixed limits. When the load is removed there is anaccurate return to the zero position .(referen.ce 4).

This device offers not only the advantage of permit-ting the reading or recording of the forces or of theirvariation at considerable distances from their point of ap-plication but also eliminates the mechanical complicationof the transmission members (parallelograms, etc.) of tilenormal balances, with the unav~idable difficulties arisingfrom the friction and inertia of the oscillating masses.

The method of operation of the mechanism is based onthe well-known principle of converting the force to bemeasured into hydraulic pressure. The spring body replacesthe cylinder-piston system and eliminates the difficultiesdue to friction and Leakage,

,,Figure 5 shows a sc~emat,ic diagram of the mechanism.

The force to be measured., I?, acts on one of the covers ofthe spring .(in.the sketch the force and spring are verticalalthough th~.,direction may be arbitrary). The spring isfilled wi.tha fluid which by means of tube T communicatesthe manometer M. The same liquid that fills the springmay be used,as the liquid in the manometer but it i,s conven-ient to adopt a liquid of greater density in order that achange in the height of the manometer tube may correspondto a greater increase in pressure and thus the advantagegained of a decrease,in the variation of the volume of thebody C and hence of the displacement of the force FtiThe liquid used to fill C and that of the .manomete.r Mcome in contact in t“he vessel V whose cross section isregulated S.O as to reduce the oscillations of the level ofthe contact surface of the liquids.

6 N.A.C.A.. ‘Technical Memorandum No.- 892

Under theaction of the force “F, there is set up onthe fluid ”in. C’ a pressure p, which.is propagated overthe tube T and the vessel V and raises the height Hof the liquid in M. Tne point of application of the forceF is displaced ‘by an amount h, which is inversely pro-portionalto the ratio’ of the cross sections of C and ofthe tube M. with suitable dimensioning of these crosssections and corresponding choice in themanomQter liquidtthe displacement h can be maintained at a negligiblevalue. There is thus eliminated also the effect of the me-chanical rigidity:of the spring.

Since we are ~ealing with the case of a liquid en-closed in pipes, it is convenient to keep the unavoidableoscillations down to a small value hy the aid of suitallethrottle valves.

In this connection a description will be given of thearrangement of the one-, two-, and three-component dynamom-eter for the towing carriage. The other apparatus of threeor “six components is based on the same principle. Thethree-component balance (reference 5) is schematically com-posed of:.

a) A mechanical system consisting of a ’vertically mov-able rod A to which the model is attached. The rod iscounterbalanced by weights and flexible bands, which passover pulleys 3. Oashpots C damp any pendulum oscilla-tions of the rod. To this rod are attached two groundsteel bars, which support “guide rollers carried on the hor-izontal members of two linkage parallelograms D, whi chresolve the hydrodynamic forces and transmit them to theindicating apparatus E (fig. 6).

The possibility ‘of changing the tvo linkages so as tomake possible the measurement of ‘components oblique or nor-mal to the model has been foreseen. The two linkages aremounted on a support of cast light metal. The supportrests on a large base plate that can rotate about the axisof the movable attachment rod so that the ,system may berevolved with respect to the direction of motion (drift).This angle; as well as the setting of the guide system, areread off on graduated circles provided with vernier andmagnifying glass. The base plate is capable of verticaldisplacements by means of the simultaneous rotation of fourthreaded spindles attached to the corners of the plate forattachment to the towing carriage. The corresponding foursteel precision nuts rest on the base plate.

N.A. C.A. Technical Memaandum No. 892 7

b) A recording app.ara.tus. The, forces to be determined,> ..act.up.oa,.t,h,e...luidifilleded spring that in turn communicates

by means of fluid-tight--metal tubes With pressure measur-ing mercury columns, the height of which gives directlythe value ’of the hydrodynamic forces (fig. 7). s -

. ,.The measurement takes place without appreciab-le dis-

placement of the,point of application (a few tenths of amillimeter for forces up..to..several hundred kilograms).17ith the aid of the adjustable throttlevalves, any de-sired damping of the oscillations of the manometer. columnsmay be obtained. Of the three pressure measuring elementstwo are connected to th,e l,idcage parallelograms and serveto measure the horizontal” components of thb force and ofthe moment while the third is connected at the upper endof the movable rod and is used:for measuring the’verticalcomponent. There is pro’videdthe possibility of disconn-ecting the latter pre.ssureelement so as to leave the rodfreely movable for measuring only two components. It isalso possible to remove the. upper parallelogram, and therod with the corresponding guide of the lower parallelo-gram can be substituted for measuring a single component.

c) An electric recording arrangement of the llUsiglilltype construction (reference 6) that can be mounted in anyposition on the carriage and whose readings are independ-ent of the variations in voltage o.f the feed lines of thedirect current system. The system consists of three trans-mitting elements and three recording devices, which areelectrically connected with each other across a differen-tial galvanometers (fig. 7). The transmitting elements areeach of a calibrated chromium nickel wire, which isstretched inside” the manometer tube.. The electrical re-sistance of the free end of this wire varies linearly withthe height of the manometer column and hence with the forcesto be measured.

The differential galvanometers are perfectly balancedand provided with damping and are inclosed in suitablecasings that are mounted on vibration p’roof. supports, sothat the vibrations of the. carriage can have no effect,The recording devices themselves possess servo motors thatare controlled by contacts. which, in turn, are actuated bythe corresponding differential galvanometers. The se,rvomotor not only moves the recording stylus but also regu-lates a resistance equal to the transmitting resistance sothat the differential galvavometer returns to the equi..Zib-rium position after each change in the pressure head;”

8 N.A.C.A. Technical Memorandum No. 892

The servo motors permit a high speed of the stylusand, in order to avoid overregulation and impacts, areprovided with electromagnetic brakes.

Three recording devices are provided; one for eachcomponent. If only one or two components are to be meas-ured the free apparatus may be used for recording otherqtiantities of interest to the test being conducted. Withthe aid of an arrangement of photocells and electricaltime-measuring apparatus there are also recorded the pathsand times for the determination of the speeds.

IV. TESTS AND 13TVESTIGATIONS

In this first period of its activity, the t~ydrodynamicSection has, in addition to work for the ministry, carriedout systematic tests of a general nature with regard toprob”leins of general interest. The work of collecting,, ar-ranging, and publishing the results is largely in progress.

The installing and improving of the equipment made itappear advisable to postpone the publication of test re-sults, although they will appear shortly i.n the ‘!Atti diGuidonia. ll

A. Tests,. . .:.

~) Tests .of hulls and floats.- Amont; the most impor-tant test results’ are thoseobtained from the systematicseries of tests on the twin floats of, the seaplane Cant Z595, which in its v&rious editionshas achieved 16 worldrecords (i”eference ‘7).. The tests were carried out on apair of similar floats. The di~lensions.in termsof thebeam at”the”step,. taken as tile unit and set equal to 100,are given in figure 8.

The model” was tested at five different distances dfrom the center lineof the ’floats, multiples of the beamb at th”e step; namely, 3, 4, 5, 6, and 7 times b andinfinity (singlehull). Tor each of these conditions, theload Q ‘and the trim’ $ were varied and the resistanceR. was obtained as a function of the forward velocitY v..About .1,000 runs were” made with the t“owing carriageforwhl.ch, thanks to the particular equipment available, about15 working day’s were consumed (reference 8).

An innovation was’ introduced in. that in defining

,+J.,

N,A. C..A.- Technical Memorandum No. ’892 9

the quantity b, which appears in the denominator of>. equation. (l),. this. quantity does not represent the sum of

the widths of both stepk ’of the”’pair of floats but a- meanhydrodynamic step which makes possible a logical compari.son of the characteristics of a pair of floats (for equaldisplacement, for instance) with the characteristics of ,ageometrically similar single float. Useful comparativevalues are obtained and also an extension in the choicepossibilities for the designer.

Let A and B ke”two geometrically similar bddiesresting in similar attitudes on a plane a (fig. 9). Letx be a system of abscissas perpendicular to a and withthe origin on the latte’r. If for the body A there holdsthe relation

Sx = f(x)

where s is the section of the solid cut off by a plane

parallelxto a and at distance x from it, then for thesecond solid B, there will hold the expression

1 19X = y Sx = f(x)

~iiK

where K is the linear ratio of similitude.

Also, if for solid A, the volume is

x

‘1D

Vx =“ f(x), d Xt,o

then for solid B the corresponding volume will be givenby

Denoting by n the ratio between the weights, thesolids being assumed “homogeneous and of the same density6, we.may write

. . .. ..,,.. ....

10. 3J.A.C.A. Technical Memorandum No. 892.,.

,.,..,: ., .....,... 6’VX -’ “’

.,. -=n,. =K3&vz ~~

“K

i.e.,

Thus, body A i~ equivalent to n bodies B if thelinear ratio of similitude K“ is equal to the cube r,ootof n. In particular, in order that a body be equivalentto two equal bodies similar to it and of the same density,it is necessary that the ratio of geometrical similitudebe

K’=z= 1.2599

In equation’ (1) the value of b has been assumed as1.26 times the beam b, of one of the steps of the floats.

The results obtained may thus “be applied to a singleas well as to twin floats if in the relations

R = CR P b3

the above equivalence is taken into account and if as afirst approximation, there is neglected the hydrodynamicinterference (reference 9) of the two floats or the re-quired corrections are made.

The first set of results that are presented in tablesI to V gives for d=3b the variation in CR as a

function of V for d= 0°, 2°, 4°, 6°, 8°, and C =1.575; 1.260; 0.945; 0.630; 0.315. $The other sets re erto d = 4b, 5 b, 6 b, 7b, and @b, applicable to thesame conditions and are given in table VI to XXX.

An examination’ of these results is very interesting,particularly if in order to facilitate comparison of thevariables under consideration, tilere are observed the var-ious combinations of these (figs. 10, 11, 12, 13, and 14),

N.A..C.A. Technical Memorandum No. 892 11

With the aid of these, data the design er, -i.f; for ex-..m ample,..he..i.s.restric,t.edin his choice of the ,characteris-

tics of the power plant (reference”’ICI’)”’”’rand-the-aerod,ynamiccharacteristics, is in a position to fix the. maximum valueof the hydrodynamic resistance that he desires to attainin getaway, as a function., for example, of the getaway,time and from this derive the most favorable distance be-tween the two floats as well as the most favorable arrange-ment of the wings (reference 11), so that the aerodynamiclift of the airfoils (for the most favora%lo. speedCV(CR —~min. ) and hence of trim O given by the experim-

ental curves) corresponds to the value ofCQ’

which givesthe least CR. There are thus fixed the structural dimen-

sions of the hull and the floats in relation to the designdata. .....

With the assignment of dimensions, the model assumesthe character of a definite seaplane (fig. 15). The modelis then attached to the side towing carriage and is sub-jected to a series of test runs in relation to wave forma-tion, etc. With the aid of a family of curves, it is pos-sible to calculate, for example:

a) The get-away characteristics for various usefulloads.

b) The maximum admissible useful load for definiteget-away characteristics.

In these cases the computed results can be checked byineans of the side towing carriage.

The large number of best loads for the seaplaneI!Cant Z 505~1 clearly shows the technical usefulness ofthis procedure.

A further group of systematic tests was conductcilforthe Caproni Firm on the model of an amphibian hull withretractable landing gear. The results of these interest-ing investigations are being assembled and will be pub-lished as soon as possible,

b)Tests on motor boats.- The Section was also en-trusted with tile task of investigating several types of..motor-boat hulls for the group of personnel of the M.V.S..N., taking part in the Gold Cup races in Detroit and the. “.‘~resident$s Cup races on the Potomac (U.S.A.).

12 N.A.C.A. Technical Memorandum No. 892

The tests already conducted made it possible to ob-tain very appreciable advantages in -regard to the resist-ance and the stability; and the boat selected, hearingthe name of ltAlagi,1’has obtained the world~s best perf-ormance in the 12-liter class ofboats and took secondplace in both races because of interruptions in the fuelsupply to the engine - although it.made the fastest roundin both races.

The Hydrodynamic Section has also studied a type ofplaning boat that in the previous year won the classic”race on the Danube and this year won the Pavia - Venicerace, making the distance in half the time employed by theothers.

.,

These tests on motor boats were extended to very highspeeds, making use also of the side towing carriage andvery interesting findings were made in relation to thestudies and other tests of Sottorfj Perring and Johnston,and Sokalov, etc., and I have undertaken to publish thesedata at “the first opportunity as soon as I have made somecheck tests.

g~ Tests on torpedo-shaped bodies.- In connectionwith the tests” on immersed floats’, the Hydrodynamic Section.,in cooperation with the Minister of the Navy was much oc-cupied with the problem of the motion of spindle-shapedbodies. with insufficient control “surfaces (torpedoes), car-rying out several series of systematic tests with the ob-ject of improving the behavior of these bodies particularlywith r’e’ga”rdto their stability (reference 12) .

I believe that the method adopted for the determina-tion of the resistance is of interest. The determinationis always rendered sol~ewhat uncertain b.y the difficulty o’festimating the interferences of the suspension rod whosedimensions and strength make it necessary to limit thespeeds to very 10V va’lu~s far removed from the velocitiescorresporl~ing to desira31e Reynolds Numbers.

Torpedoes ~eneral?.~ have insufficient control surfaceor none at all. Thfiir stability in trim depends on thesetting of the depth rudders. The clotermination of thetrim is relatively si”mpie and r;eziabl’~,” Durinq the ,motionwith a given angular setting in the instantaneous directionof the speed V, there is set up a lift which must balancethe centrifugal force. If m denotes the i~ass of the body,L one of its linear dimensions, p the density of the

N.A.,C.A. l?echnical Memorandum No, 892 13

medium; R the instantaneous radius of curvature, and. k a .coefficient-of.pr,oport$o.nalj~ty a_e,a function of the

trim. ,, -, ,,,,.. ... ..

from which is obtained

which shows that the trajectory is circular and independ-ent of the speed. If this body is projected into the wa-ter along a known direction and with a known velocity andthere is measured the time required until it comes upagain, it is possible to measure the uniformly retardedmotion and then to determine the resistance. For thispurpose, there is employed the catapult apparatus whichpermits the variation of V and the angle of entry intothe water. These tests are now in progress.

B. Theoretical Investigations

a) Pressure distribution on geometrically sinplebodies.- In the field of theoretical investigation, theHydrodynamic Section is conducting pressure-distributiontests along the surface of a sphere at various velocities.These tests, of great theoretical interest and quite corn.mon in the field of aerodynamics, are far rarer in numberin the field of hydrodynamics. It was found necessary todevelop a special differential manometer for these finemeasurements. These tests are in progress at the presenttime.

3) Propagation of small wave motions.- Also in thetheoretical field, tests are being conducted to determinethe law of propagation of small waves that are produced bya perfectly geometric body (sphere) dropped into the materfrom various heights. The method is based on the changein resistance of two plates of suitable cross section im-mersed in water, the change in resistance being indicatedby the change in light intensity of a cathode ray oscillo-graph.

14 N,A.C.A. Technical Memorandum lJo.“892

~Planinr and su%merged surfaces.- Finally, with the.—cooperation of Crescentini, a collaborator of ProfessorForlanini, tests are being conducted on lifting surfaces. .moving below or on the surface of the water. The possi-bility of obtaining greater experimental speeds will pro-vide important means of study.

v. CONCLUSION

I regret that I was unable to present at this meetingall the results of the work conducted but I hope to beable to make them public as soon as possible and I wish toexpress the desire for a closer cooperation among the fourhydrodynamic testing institutes that particularly occupythemselves with aeronautical investigation, in Germ&ny,”The United States, England, and Italy. There will thusresult a greater and more rapid development of this branchof aeronautics for which, with the ever-increasing weightsand dimensions of seaplanes, a brilliant future may be ex-pected.

Translation by S. Rpiss,National Advisory Committeefor Aeronautics.

. .

N.A. C.A. Technical Memorandum No,. 892 15

RE3’ERENCIOS “. .,..”, ,,. . ... .. .

1. Cremona, Co: 11 carro-ponte dinamometrico.. Atti. diGmidonia No. 1, Sept. 1938, XVI.

2. Crocco, G. A.: Llavvenire degli idrovolanti. Confer-enza tenuta a Parigi alle Journees Techniques In-ternationals de llAeronautique - LIAerotecnicaoJan .-l?eb. 1933, XI.

Cremona, C.: 11 carro laterale dinamometrica. Attidi Guidonia (not yet published).

3. Sacerdote, G.: ivietodielettrici per la misura di pres-sioni. e di spostamenti. LIEl~ttrotecnica, J~iy 5,1932, X. .,

4. Cremona,” C,, and Crocco, L,: L~Dispositivo manometricoper la misura di forze senza spostamento apprezzabiledel punto di applicazione. Privativa IndustrialNo. 345,696.

5. Cremona, C., and Crocco, L.: Ltapparato dinamometricoad uno, due e tre component dells Sezione Idrodi-namica di Guidonia, Atti di Guidonia (not yet pub-lished).

6. Usigli, B.: itioderni strumenti elettrici di misura reg-istratori e loro impiego. LllIlettrotecnica, vol.,XIV , 1929.Une solution du probleme de la mesure et la totali-sation a distance. Conference International desGrands Reseaux Elec a i-it. Paris, Session 1931.

7. Cremona, C.: Sul progetto degli idrovolanti - Criteridi indagini e risultati sperimentali circa la ricorcadells variazione dells resistenza in funzione dellsvelocita per varie condizioni di assetto e disloga-mento in relazione alla distanza fra le mezzeriedegli scafi, di un idrovolante biscafo. Convegnodi Aerotecnica delllA.I.D.A. , Naples, May 1938.

8. Cremona, C.: Gli smorzatori dlonda dells Vasca Idro-dinamica di Guidonia. Atti di Guidonia (not yetpublished) .

9. Cremona, C.: Llinterferenza idrodinamica fra gli scafidi un biscafo. (Not yet published.)

16 N.A.C.A. Technical Memorandum No. 892

10. Cremona, C.: Moderni problemi di adattamento dei pro-pulsory. LIAerote~nica, March 1936, XIV.

11. Verduzio, R.: Hydrodynamic Tests for Determining theTake-Off Characteristics of Seaplanes. T.lh. NO.

204, N.A.C.A. , 1923.

Hermann, H.: Seaplane Floats and Hulls. T.M. NOS.426 and .427, N.A.C.A. , 1927.

Durand, W. F.: Aerodynamic Theory. vol. VI, Div. 5,Julius Springer (Berlin), 1934.

Crocco, G. A.: Tempi e spazi di partenza e di attera-mcnto dei velivoli. LIAerotecnica, .Lug.-sept.1937, xv.

12. Cremona, C.: La stabilita nel moto dei corpi siluri-formi insufficientemente impennati. Atti diGuidonia (not yet released).

,.”

.,

●

Memorandum No. 892 17d=.+b TabellaVI ti=o”

N.A.C.A. Teohnicald=3b TabellaI tv=o”

I tCg

= o,63a

0:0205’0.10000.14000.15100.14650.15600.17650.19600.2390

Cq C@= 1,260 = 19575

Cv

0.827x.6542.48 I3.3084.1354.9625.7896.61674’43

cq—= 0,315-

0.015’750.058260.066150.06940.08190.09760.09760.13860.1701

Cg= 0,315

‘0.01580.05360.07100.07300.08820.11000.12300. x6400.1825

Cq= 0,945

0.02550.13920.21400.25800.23000.21100.21400.22800.2650

Cq=’ 0,630

o.0204z0.09140.13080.13220.1339?14010.X5740.17480.2042

Cq= 0,943

0.022050.11970.2110.22930.19830..19520.20150.21410.2457

Cq= 1,260

Cq= 1,575

-.~;82”7

1.6542.48 z3.3(284.1354.9625.7896.6167443

‘0.01260.15750.25800.32100.30600.287o0.265o0.26800.3211

0.0315”0.i5420.2770.3310.29250.2580.25040.2520.2707

0.03.620.17320.32750.40350.38750.3310.30230.30550.315

d=db Tabella VIId=3b Tabella II

CRCB

Cq= 0,945

0.02460.11280.2000.20460.17630.1590.1637o.L89

Cq= 0,315

Cq= 0,630

Cq= 0,945

Cq= I,26c

Cq= 1,575Cv

0.8271.6542.4813.3084.1354.9625.7896.616

cq= 0,315

0.015750.058270.06870.06770.08450.09450.0976

Cq= 0,630

Cq= 1,260

Cq= 1,575

0.03900.1860.3340.4130.3960.3120.308

0.8271.6542.48 I3.3U84.1354.9625.7896.516

0.015740.06570.06150.06050.07250.0630.06930.1040.1291

0.022040.089750.13080.11020.1165o.II80.14180.14320.170

0.009450.09450.18840.2420.16370.1700.16380.1890.2267

0.009450.13220.2770.28020.2300.21730.22640.24870.255

0.029930.1560.36850.37640.31020.2770.2580.2710.299

?J=4”

0.03080.1480.2680.3030.2610.2300.228

0.020420.09140.13860.13540.11970.13860.1418

7.443

Tabella VIIId=zibd=3b Tabella 111

Cv Cq Cq= 0,315 = 0,630

CR

Cq= 0,945

0.03120.12600.20300.18250.16700.17650.2015

lla Iv

Cq= 1,260

0.0370.16050.26800.27100.233O0.22800.2580

(0.268)

Cq= 0,945 =

Cq1,260

Cq= 1,575

1

Cq= 0,630

Cq= 1,575

0.04720.22050.33700.372O0.30200.27700.2995

t?=6°.—

0.8271.6542.48 I3.3084.1354.9625.7896.616

0.01260.05990.06930.07560.10090. I 04

0.02520.09450.12760.12430.13540.176

0.02835 0.03620.126 0.15120.195 0.280.192 0.2680.1794 0.2330.192 0.2250.2237 0.27080.234~ 0.274

Ila 1X

0.0630.17630.362o.36a50.3240.29450.3150.310

?9=6°

0.827 0.01833.654 0.06232.481 0.07403.308 0.07784.135 0.09764.962 0.12605.7896.616

0.01260.09450,13250.12300.12600.13920.1765

Tabd=3b - d=db Tab

~

CRCv Cq Cq Cq Cq Cq

= 0,315 = 0,630 = 0,945 = 1,260 = 1,575 ~

CRCv Cq Cq Cq Cq Cq

= 0,315 = 0,630 = 0,945 = 1,260 = 1,575l—

0.827 0.0157 0.0192 0.0284 0.04101.654 0.0598 0.1040

0.04980.1385

2.48 I0.16?0

0.07500.2205

0.1390 0.2080 0.293O3.308

0.3560.0882 0.1420 0.1985 0.277O 0.362

4.135 (0.1135) 0.1575 0.1985 0.26004.962

0.3370.1950 0.217,5 0.2640 I 0.321

d=3b Tabella V @=8°

0.8271.6542.48 I3.3084.1354.9625.7896.6I6

0.03150.06930.08820.10230.1370.1670.20460..2495

0.03780.11330.14650.1542o.l~o0.19670.230

0.05045 0.061450.129 0.15750.2017 0.28950.208 0.2800.214 0.26450.2265 0.2740.2423

0.07560.3720.39070.3750.3460.3370.3370.35 I

d=.+b Tabella X fi=8eCR

Cq Cq Cq Cq Cq= 0,315 = 0,630 = 0,945 = 1,260 = 1,575 Cv Cq Cq Cq Cq

= 0,315 = 0,630 = 0,945 = 1,260Cq

= 1,5750.0249

0.06460.07590.10900.13550.14200.13550.14500.1609

0.040950.11300.13900.16100.18300.21800.255

0.04570.15140.224o0.235O0.24400.2550

0.0630.20170.3090.3090.3057

;0.3340.356

0.06930.2460.3940.3810.3720.384

0.8271.6542.4813.3084.135,4.9625.789,6.6167.443

■ II

0.8271.6542.4813.3o84.1354.9625.7896.616

0.28350.06770.08820.11330.13850.13850.13220.1511

0.04410.11650.1511o.I670.19650.22030.252

0.063 0.07720.1574 0.208.0.222 0.30550.233 0.3120.236 0.30S60.2645 0.3180.3005 0.3460.3435

0.09760.2360.39050.3940.3860.38730.403

892 18d=6b Tabella XVI 0=0”

N.A.C.A. Technical Memorandum No.

d=~b Tabella XI ?9=0”

CRCv Cq Cq

— 1,260. = 1,575—Cq Cq

= 0,315 = 0,630

0.022 0.0280.044 0. I 040.065 0.140O.oyI 0.1390.085 o.I380.101 0.1480.096 0.1570.142 o.I92

Cg Cq= 0,945 = 1,260

,,.. 7-

Cq= 1,575>. . . . .. . .—

0.8271.6542.48 I3.3084.1354.9625.7896.616

0.0080.0500.063

0.027,.0.120

0.479O.qoo0.0800.9200.840

(:%)

0.8271.6542.48 I3.3084.1354.9625.7896.6I6

0.038 0.0380.151 0.1890.22 I 0.3280.340 0.3850.290 0.3850.265 0.3430.266 0.3180.309 .0.309

0.035 o.o~~0.088 0.1400.208 0.2680.236 0.3390.205 0.2950.205 0.2660.224 0.2630.236 0.268

0.0530.1470.3300.630.0.3970.3530.3340.350

0.09 io.I29o.I320.1390.1510.1580.164

0.07:0.0880.1070.1010.155

d=6b Tabella XVII 0=2”d=sb Tabella X11 ?9=2”

Cv —.Cq

= 0,315

I

Cq Cq= 1,260 = 1,575

0.063 0.0820.151 0.1750.248 0.3560.273 0.3900.268 0.3370.262 0.2900.238 0.2760.235 0.271

Cv

0.8271.6542.48 I3.3084.1354.9625.7896.616

Cq= 0,630

0.0280.0880.1320.1170.1170.1290.137o.I61

Cq= 0,315

Cq Cq= 0,630 = 0,945

0.032 0.0500.088 0.1130.133 0.2020.113 0.1890.113 0.167o.I26 o.I720.129 0.173

o.I92

Cq= 0,945

Cq= 1,260

Cq= 1,575

0.044o.I480.3970.4040.3400.2930.2680.289

0.0360.1350.2900.2860.2430.2220.2400.236

0.0250.0570.0610.0690.0730.0820.088

0.8271.6542.4813.3084.1354.9625.7896.616

0.0220.0580.0630.0690.0760.0690.0730.088

0.0360.1120.2080.1980.1750.1700.1860.198

d=6b Tabella XVII1 l?=~”Tabella XIII ??=4”

Cv Cq —= 0,315

Cq= 1,26c

Cq= 0,315

0.0220.0610.0770.08 I0.0980. IOy0.131

Cq= 0,630

0.0250.1010.1340.1260.1310.151o.I87

Cq= 09945

0.0350.1200.2150.2000.1840.1920.2270.240

Cq= 1,260

Cq= 1,575

0.0540.1790.3780.3820.3180.2900.3120.305

??=6°

Cq= 0,63c

Cq= 0,945

Cq= 1,575

0.0760.1890.3880.3750.3220.2900.3080.296

0=6°

0.8271.6542.48 I3.3084.135;;;;

6:616

0.044o.I480.2840.2760.2460.2330.2610.270

0.8271.6542.48 I3.3084.1354.6925.7896.616

0.0220.0550.0660.0740.0880.0950.095

0.0340.095o.I29o.I26o.I270.1400.161

0.0410.1260.2050.1950.1730.1810.214

0.0600.1570.2240.2770.2460.2330.2520.263

d=ib Tabella XIV d=6b Tabella XIX

ICv Cq Cq Cq ‘Cq Cq

= 0,315 = 0,630 = 0,945 = 1,260 = 1,5751

Cv Cq= 0,315

Cq= 0,63c-

0.0380.1130.1330.1420.162o.I83

Tab

Cq= 0,945

Cq= 1,260

Cq= 1,575

0.8271.6542.48 I3.3084.1354.9625.789

0.022

0.0630.0790.0950.1280.1400.180

0.0290.1170.140

‘0.1510.1650.1880.205

0.0390.1450.2060.2050.2030.2250.261

0.0540.1700.2280.2840.2770.2740.312

0.0610.2050.3690.3790.3500.3340.359

0.8271.6542.48 I3.3084.1354.9625.789

0.0220.071

0.0820.095o.I23o.I42

0.0410.1400.2050.2140.2140.2300.265

la xx

0.054o.I8o0.2270.2860.2710.2710.315

0.0720.2050.3720.3790.3470.3290.365

d.= Xb Tabella XV 7?=8°

I CRd=6b ‘0=8°

CvCR

Cq Cq= 0,945 = 1,260

CT — Cq Cq Cq Cq Cq= 0,315 = 0,630 = 0,945 = 1,260 = 1,575 Cq Cq

= 0,315 = 0,630Cq

= 1,5750.8271.6542.48 r3.3084.1354.9625.7896.616

0.0300.0690.0880.123o.I420.1350.1390.157

0.0410.1200.1540.164o.I920.2080.214

0.0500.1580.2270.2360.2490.2800.2910.350

0.0600.2020.3150.3180.3230.3400.3720.407

0.0690.2330.3950.3970.3890.3940.4280.460

0.8271.6542.48 I3.3084.1354.9625.789

0.024 0.0410.063 0.1120.076 0.1390.098 o.I42o.I26 o.I620.142 o.I830.120 0.164

0.044 0.063o.I32 o.I830.207 0.2320.207 0.283‘0.211 0.2690.226 0.2750.265 0.325

0.0630.1860.3780.3690.3440.3300.356

892 19

d=m Tabella XXVI ti=~o

N.A.O.A. Technical Memorandum No.

d=7b Tabclla XX1 0=0”

t

Cv @ Cq—.,,. ,.,= 0,315 = 0,630

0.827 0.0204 0.02201.654 0.0614 .0.07242.48 I 0.0646 0.13393.308 0.0756 0.13704.135 0.0929 0.13864.962 0.107.1 0.15125.789 0.0819 0.167

d=7b Tabc

I

J-Cv Cq= 0,315

I

Cq cq= 1,260 = 1,575

T

0.024o.I480.2680.3300.2740.2400.2250.224

cq Cq Cq= 0,945 = ,1,260 = 1,575

0.0252 0.04.41 0.04720. I 307 0.1481 0.17320.2111 0.2772 0.23780.2237 0.3591 0.523002111 0.2868 0.3780.2063 0.2647 0.33080.2173 0.2678 0.3088

la XXII 0=2’

-. Cq Cq=.0>630 =,9?945

T

0.024 0.0240.091 0.117

0.123 0.195

o.I23 0.2130.120 o.I890.120 0.1730.117 0.1730.132 0.181

0.827 0.0181.654 0.0412.48 I 0.0473.308 0.0504.135 0.0554.962 0.0655.7896.616

d==

Cv

Tabella XXVH +=~o

Cv I Cq Cq= 0,315 = 0,360

0.827 0.0157 0.02521.654 0.0583 0.09132.481 0.0551 0.1323

3.308 0.0614 0.1172

4.135 0.0709 0.1213

4.962 0.0819 0.1291

5.789 o.148I

6.616 0.1591

d=yb Tabe

Cx

Cq= 0,945

0.0320.1070.189o.I8I0.1510.1340.1290.132

Cq Cq= 0,945 = 1,260

0.0283 0.03620.1197 0.15750.208 O.277Z

0.1906 0.2803

0.1686 0.2347

0.1701 0.2205

0.1827 0.2362

0.1985 0.252

la XXIII

Cq= 1,575

0.05040.2237Q.34330.38280.323

0.27720.2857

0.2898

‘7?=4”

Cq= 0,630

Cq= 0,315

Cq= 1,260

Cq= 19575

0.0520.167Q.3430.3700.3120.2570.2280.220

o=~”

0.8271.6542.48 I3.3084.1354.9625.7896.616

0.00950.0440.0470.0460.0530.0520.0440.044

0.0210.0680.1170.1050.096

0.0950.0870.088

0.0410.1350.2590.2620.2150.1950.1700.170

d=m Tabella XXVH1l——— CR

Cv – Cq Cq Cq Cq Cq= 0,315 = 0,630 = 0,945 = 1,260 = 1,575

, 1 1 1

~v Cq= 0,315

I

Cq Cq Cq Cq= 0,630 = 0,945 = 1,260 = 1,575

0.03620.10710.12760.12440.13070.16060.1417

0.04090.12760.208o.I890.17640.19540.2001

0.04410.15750.2630.2740.24580.23310.26470.2662

0.05360.17640.36220.36850.30560.2867Q.334o.3i5

0.827 0.02201.654 0.06142.48 I 0.07093.308 0.07724.135 0.09454.962 0.10713.7896.616

0.827 0.0191.654 0.0492.48 I 0.0573.308 0.0544.135 0.0654.962 0.0575.7896.616

d=m

0.0300.09 I0.1I70.1070.0960.1060.113

0.0380.II80.1800.1760.1420.1420.169

0.0290.1420.27 I0.2500.211o.I870.1990.202

0.0440.1700.3650.3530.2900.2040.2040.247??=6°d=7b Tabella XXIV t?=6° Tabe a XXIX

-

Cv

0.8271.6542.48 I3.3084.1354.9625.7896.616

——Cq Cq

= 0,315 = 0,630

0.022 0.0330.057 0.1010.063 0.1290.073 0.1280.097 0.1340.088 0.145

..

Cv Cq Cq= 0,315 = 0,630

0.0283 0.03620.0583 0.10080.0740 0.13390.0929 0.14020.1197 0.15750.1370 0.18270.1465 0.1733

0.2269

Cq= 0?945

0.03620.14490.20790.20790.20320.21580.26150.2882

Cq Cq= 1,260 = 1,575— .

0.0504 0.05670.1733 0.20790.2882 0.37180.2788 0.37180.2662 0.33080.3023 0.31820.3134 Q.3340.3182 0.356

Cq Cq Cq= 0,945 = 1,260 = 1,575

0.038 0.044 0.0490.142 0.170 0.2110.199 0.277 Q.3750.191 0.269 0.3560.188 0.249 CI.3180.186 0.241 0.296

0.265 0.3120.290

0.827x.6542.48 I3.3084.1354.9625.7896.616

d=7b Tabella XXV ?9=8” d=m Tabella XXX fi=8°-

Cv,CR

Cv -Cq

= 0,315

0.02366.05980.08190.11340.13070.12130.1370.1402

Cq= 0,315

0.0250.0570.082

0.0940.0910.0760.0820.069

Cq Cq= 0,630 = 0,945

Cq= 1,260

Cq= 1,575

Cq= 0,630

Cq= 0,945

Cq= 1,260

0.0570.2110.2330.2250.2220.2300.246Q.335

Cq= X*575

0.0790.2460.3880.372Q.3570.3570.372Q-397

0.0362 0.04720.1071 0.16060.1465 0.21730.1591 0.3200.1874 0.24270.2205 0.2647o.225z 0.2882o.296I 0.3433

0.8271.6542.48 I3.3084.1354.9625.7896.616

b.8z71.654

2.48 I3.3o84.135

4.9625.7896.616

0.06620.19220.29920.30230.30090.33080.33550.3843

0.07870.23620.39080.39080.3780.38750.40950.441

0.0410.1170.1450.145o.I72o.I89o.I85o.I6I

0.0470.1640.2190.2090.2180.2400.2240.246

“’==

.

I

N.A.C.A. Technical Memorandum No. 892-...”.

t ,Fs’

..*

r............

vFigure 5

-1

,

1

IiI,I8

J

Figure 7

xt A

Figure 10

Figs. 5,6, ?,8,9,10,11

c

c

Figure 6

Figure”8L+70--9I

(z’-#d_ c~

\* /t-@-z5

@u

\-.“:iJ-,>:/,//——-@f5

Fig.11

—.

N.A.C.A. Technical Memorandum No. 892 Figs. 12,13,14

0.4@o =2 ‘ d: = 4-) gv

.F,. -. ,“ # 3

‘, & /“0.3 - /,.-,/ 4.:)

c -..R /“ “— >

/“, K )

0.2 /.L ~,’.

(// k

~ F / 1.:i

0.1 -~--

T“ /,,I ./4J”- ‘– ‘--

0 0.4 0.8 1.2 1.6 -Figure 12

1.6d~4” El

-- 4

% “ b’s CR

1.2 - .0.30-.--- — ,—- ._ --10.24/- -

0.8 ‘- - ~ - — ‘---’ 0.18

‘Q ‘--’ –,-. —.

~ ,- “ -

-..0.4 – -- — ‘-–;0.12

—.--.—--- “---. .-—— .-—- .10.06

0 I

Figure 13

0.4

0.3

0.2

0.1

.

d = 4bCQ ‘“ -’2( ‘0 C.r

\——. . _ —--\ 7-.\ . / /

/

I - 7--- .~. .-,... .- -,-

—..-

..,

●

o 2 4 6 80°

Figure 14

. .

1.’:-,.,..

.

,.. ,.’,

,,

.,,.,,!

.!’

,.,., ,:., --J,,.

,,, -.,

,,

1