NACA TM 1254 Systematic Model Researches on the Stability Limits of the DVL Series of Float Designs

7/27/2019 NACA TM 1254 Systematic Model Researches on the Stability Limits of the DVL Series of Float Designs

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FILL COpy10. 1.

NATIONAL ADVISORY COMMITTEEFOR AERONAUTICS

TECHNICAL MEMORANDUM 1254

SYSTEMATIC MODEL RESEARCHES ON THE STABILITY LIMITSOF THE DVL SERIES OF FLOAT DESIGNS

By W. Sottorf

Translation of "Systematische Modelluntersuchungen liberden tauchstampffreien Stabilitats bereich des DVL-Einheitsschwimmers ."Jahrbuch 1942 der Deutschen Luftfahrtforschung .


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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

TECHNICAL MEMQRANDUM 1254

SYSTEMATIC MODEL RESEARCHES ON THE STABILITY LIMITSOF THE DVL SERIES OF FLOAT DESIGNs*"

By W. SottorfSUMMARY

To determine the trim range in which a seaplane can take off withoutporpoising, s tab i l i ty tests were made of a plexiglas model, composed off loat , wing, and ta i lplane, which corresponded to a ful l-s ize researchairplane. The model and ful l-s ize s tab i l i ty l imits are in good agreement. After a l l s t ructural par ts pertaining to the a ir frame wereremoved gradually, the aerodynamic forces replaced by weight forces, andthe moment of inert ia and position of the center of gravity changed, nomarked change of l imits of the stable zone was noticeable. The l a t te r ,therefore, is for pract ical purposes affected only by hydrodynamicphenomena. The stabi l i ty l imits of the DVL family of f loats were determined by a systematic investigation independent of any par t icular seaplane design, thus a seaplane may be designed to give a run free fromporpoising.

SYMBOLS


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2

vFf

0,*

NACA TM 1254

speed, meters per secondFroude numberfre


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Our researches confirm. those made in England which show that a l lseaplanes have a definite zone of stable at t i tudes similar to tha tshown in figure 1. The position of the upper and lower l imits ofthis s tabi l i ty region varies from ai rcraf t to ai rcraf t , but thereare several features common to a l l ai rcraf t . The l imits divergewith increasing speed. The lower l imit i s highest near the hump -where the stable zone is narrowest - and a seaplane having too

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high or too l:lW an at t i tude there wi l l be almost certain to porpoise.Just before take - off, crossing the upper l imi t may lead to severeporpoising causing the seaplane to bounce clear of the water. On theother hand, the amplitude of porpoising may be l imited by the influenceof the aterbody. The rea l danger point occurs a t high speed in thelower l imit , where a porpoise, building up rapidly, may cause the bowto dig in . This usually leads to to ta l loss of the a ircraf t . Sucha case has been encountered on the l a tes t English flying boat -Short ' 'Empire.''

As stated above, German seaplanes in general are in no dangerfrom porpoising provided they d6 not encounter a large disturbance.This ' s tab i l i ty i s dependent on(a) The position of the s tab i l i ty l imits(b) Any factors which may- affect the at t i tudeOf par t icular significance is the determination of s tab i l i tyl imit s for the DVL family of f loats giving the most sui table


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4 NACA TM 1254of two f loat families with keel angles of 1300 and 1400 to determinethe s tabi l i y l imits over the attainable a t t-tude range. Finally anexamination was made of the effect of the afterbody by tests on aseries of forebodies alone.

II . RESEARCH PROCEDURE

The apparatus used in the tests is i l lustrated in figure 2. Themodel i s carried forward and under the carriage in order to eliminateas far as possible the effects of air-flow interference from thecarriage (reference 5).The model is constructed of plexiglas throughout. Wing and t a i lsurfaces for the f loat under t e s t are attached to a framework on the

f loa t . Movable wei_ghts are used to change the to ta l weight and momentof inert ia . The f loat i s diviotble into two parts at the step, thusallowing variat ion of the forebody-afterbody combination and stepheight. Plexiglass construction offers the following advantages:(a) Being transparent i t allows observation of the flow over thebottom.(b) I t compares favorably with balsa construction for weight and

strength.(c) I t i s not subject to distortion and is water res is t ing.


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6 NACA TM 1254IV . EFFECT OF ALTERATIONS TO THE MODEL

(a) Alteration of Moment of Inert ia

By displacing the trim weights on the model balance arm, themoment of inert ia J y was increased in two steps by 42 percent and97 percent to find the influence of an excessive moment of iner t iaon s tab i l i ty .In figure 5 the nondimensional coefficient

iy= v / ~

has been plotted as a function of weight G for a number of ai rcraf t ,and it can be seen that the moment of inert ia of the ful l -scale V85 isrepresentative of moCiern practice and that an increase of 97 percentbrings the moment of inert ia well above normal.Comparison with the preliminary t es t s shows that the stableconditions are unaffected by these changes in moment of inert ia . Inthe unstable region the amplitude of osci l la t ion increases with increase


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8 NACA TM 1254

elevator d eflection. The above loads are influenced by the tai lplanel i f t ; a correction has been made for this and the l imits reduced toconstant ca*.Figure 8 shows that with increasing load both upper and lowerl imits move towards higher at t i tudes by approximately eClual amolUlts.I f , as in figure 9,

A*coeff ic ient cB = -----2'ClbSta* is plotted against the hydrodynamic l i f tdetermined in reference 6, i t is apparent that

the highspe2d lower-stabil i ty curves, where the stern is not wetted anda t which the influence of Froude number is negligible , coincide. Thespreading of the stable zone below the hump appears in figure 9 as abranch curve deviating from the direction of the mean l ine .

The l imits for the preliminary research have been interpolatedfrom figure 8 and they agree with the l imi ts obtained by directmeasurement, figure 10.

V. COMPARISON BEIWEEN MJDEL A.Nl) FULL SCALE

Comparison between model and fu l l scale is given in figure 11.Since, as has been shown already, the l imits are sensitive to load onthe water, the model scale resul ts were corrected for increase in l i f tdue to propeller thrust component and sl ipstream.


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NACA TM 1254

plotted in figure 15. The constant loadings chosen - uncorrected fort a i l l i f t - correspond to those given in figure 22 fo r the f loats ;the speed range covered was also similar .

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At f i r s t glance i t is obvious that the character of the lowerl imits and their sensit ivi ty to load confirm the results alreadyobtained. At low speed there exists - depending on the length of thesurface and provided a sufficiently great nose-down moment can beachieved - a second l imi t below the primary one. The two l imits meeta t a speed sl ight ly below the hump speed. But, since a t this speed thel imits are greatly dependent on the effect of the afterbody, th i ssecondary l imi t i s of no practical significance.

There is no upper l imi t . The atti tude of the planing surface a tvarious loads and speeds was increased to 200 - in which case the wettedlength vras 20 to 30 llIDl - without encountering porpoising. However, thef l a t surface was very sensitive to a disturbed water surface and a purevert ical osci l la t ion occurred at att i tudes from 30 to 90 - depending onthe loading - above the stable at t i tude. The amplitude of this osci l lat ion increased with increase in atti tude (fig . 17); a t low weight andhigh speed the t rai l ing edge is thrown off the water. With perfectlyundisturbed water the oscil lat ion does not appear. The surfaces withdeadrise showed no tendency to osci l la te under similar conditions.

Figure 16 gives the l imits interpolated for dimensionless speedand load coefficients (corrected for t a i l l i f t ) .

The surfaces with deadrise gave similar resul ts to the f la t surface.


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10 NACA TM 1254hul l and (2 ) f l a r e a t the chine . The influence of these factors ons tab i l i ty i s c learly shown in the comparison between planing surfacesand forebodies .

As with the planing surfaces, there is no upper l imi t (at t i tud er ange cover ed = 200 ) ( f ig . 21). With the shortes t fo r ebody - DVLf i gure 19 - t he l m.;re r l imi ts ar e f r om 0. 50 to 20 higher ' over the wh ol es peed r ange j the smaller the a t t i tude the longer is the ,.;retted surfaceand more of the s trongly warped bow is subject to pressure . At lowloads and high water speed, the difference is accentuated . The warp inghas obviously the greatest influence since , the change in deadrise hasalre ady been shown to be of comparative unimportance and the chinef lare reducing as i t does the pre s sure area is an ameliorating f acto r .

The forebody of intermediate length - DVL 18 - which was testedonly over a l imited speed r ange a t high load shows that for = 1.25and F = 4 the l imits are coinqident and tha t a t higher load theforebody is somewhat bet ter than the corresponding planing surface.This tendency was also apparent in the tes ts on DVL 17 where thedifference between forebody and planing surface l imits is decreasedas the load increases .

As would be expected, the long forebody - DVL 19 - shows aneven greater improvement at high load. At low load and high speedthe p laning surface i s s t i l l the more stable but the difference betweenthe two i s much less than with the shortest forebody .


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NACA TM 1254 11

For the short and long hulls the freQuency of the porpolsillgosci l la t ion a t each experimental point has been plotted in additionto the stabi l i ty l imi ts ( f igs . 23 and 25). I t can be seen that onthe lower l imi t the f r e Q u ~ n c y a t high speed is almost double that a tthe hump. On the upper l imit the difference i s not so great . ThefreQuency also increases with increase in weight and length, and isgreater a t the upper l imit than a t the lower. These resul ts confirmthe contention made ear l ier that the freQuency of porpoising oncei t has started i s greatly dependent on the moment of iner t ia . Forease of interpolation the l imits have been plotted nondimensionallyusing aT as a function of ca* with F as pa r ameter and aT asfunction of F with ca* as parameter (f igs . 26 - 28) .

In figm"es 29 to 31 i s given the relationship between the l imitsand cB*. At high speed the curves of lower l imit can be collapsedwith a scat ter of less than 0.5 0 For the upper l imits the scat teris less than 10. This resul t indicates that a t high Froude numberwhen the planing condition has been reached the t ransi t ion from thestable to the unstable sta te occurs a t a given value of ~ and

Qbs t2wetted length and is independent of Froude number .

Although, as is already established, the afterbody in i t ia tes theupper l imi t , i t has a stabi l iz ing effect , on the lower l imit . Inf igures 23 to 25 the l imi ts for the forebodies can be compared withthe l imits fo r the complete hulls . The afterbody lowers the l imits


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12 NACA TM 1254

VII . METHODS FOR WIDENING THE ST.A13ILITY RIDlON

The foregoing s tab i l i ty diagrams wil l give information for anyprojects based on the DVL f loat family. Even for designs somewhatdifferent from this series the resul ts wil l give sufficiently accurateinformation; for example, the deadrise has l i t t l e effect , and thestrength of the afterbody affects only the upper l imit .Widening the s tab i l i ty l imits in cases where the at t i tude approachesthe l imits and fo r various reasons cannot be altered may be accomplished

by the following means:

(a) Upper Limi tTo make a short take- off the seaplane m ~ be pulled off sharplythereby running into the upper l imit . By using afterbody auxil iarysteps from 0.01 to 0.02bSt deep ( f ig . 34), this l imit can be raised asmuch as 30 The optimum condition is reached when the tangentialflow from the forebody is deflected by the auxil iary steps producinga stabi l iz ing force (fig. 35). In addition there is a considerablereduction in resistance confirmed by ful l-scale t es t s .

(b ) Lower Limit


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NACA TM 1254 13

hydrodynamic l i f t i s moved nearer the step, the running at t i tude isreduced. Hence, by a supplementary investigation a suitable combinationof camber, step posi t ion, and center- of-gravity position must be found.In figure 36 the s t a b i l i ~ l imits from three cambered hulls (a s shown)are compared with the corresponding resul ts for an uncambered hul l(keel angle 1300, ca* = 1.5 and 2). I t can be seen that l imits aremoved in proportion to the angle a t the step (50 441 and 20 521investigated) while the radius and length of the hook (R = 10, 20and 40bSt and 2 = I and 2bSt ) affect the l imits only insofar asthey change the angle a t the step. As the , load i s reduced or thedynamic pressure increased, the change in att i tude approaches thevalue of the step angle. Further research i s required on thissubject to determine a suitable camber.

VIII. CONCLUSIONSPorpoising is an osci l la t ion which occurs during the landing andtake-off of a seaplane and which may lead to to ta l loss of the aircraf t .An in i t i a l investigation was made with a plexiglas model, comprisedof a f loa t , wing, and t a i l , which was dynamically similar to theVought v85 f i t ted ~ t h a DVL-family f loat . The model and ful l -scalegive similar resul ts for the stable regions. The l imits of th i s r e giondiverge with increasing speed.


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14 NACA TM 1254

A seaplane with forebody alone has no upper-l imit ins tabi l i ty upto the maximum practicable at t i tude. I f a f lying boat shows instabi l i tya t the upper l imi t , this can be cured by al ter ing the afte rb ody only -increasing the afterbody keel angle. For the lower l imi t the a f te rbodyis stabi l iz ing near the hump, that i s , so long as it is wetted, andas a resul t the lower l imi t , which r ises sharply with decrease in speedt i l l i t reaches the hump, fa l l s away again.

When no other means are available the l imits ca n be widened i fnecessary by. (a) The addition of small auxil iary steps on the afterbody which

wil l raise the upper l imit(b) Lowering the afterbody or hooking the rear step which wil llower the lower l imit a t the hump(c) Making a sl ight concavity in the keel immediately forward ofthe step thereby lowering the complete lower l imitThis l a s t al terat ion affects the running att i tude so tha t asui table compromise must be made between step pOSition, center-of-gravityposi t ion, and degree of concavity. .With the working diagrams of the DVL f loat families presented

herein a t hand the designer can now design a seaplane with a take-offor landing run free from porpoising.


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NACA TM 1254 15

REFERENCES

1. Perring, W. G. A., and. Hutchinson, J. L.: Full Scale and ModelPorpoising 'I'es ts of the Singapore IIC.A R C" 1936. R & M No. 1712, Brit ish

2. Coombes , L . P., Perring, W. G. A., and Johnston, L.: Th e Use ofDynamically Similar Models for Determining the PorpoisingCharacterist ics of Seaplanes. R & M No. 1718, Bri t ish A.R.C., 19 36.3. Sottorf: Gestaltung von Sphwimmwerken. Jahrbuch 1937 der DeutschenLuftfahrtforschung, p. I 309. (Available as NACA TM 860.)4. Lechner: Unte rsuchungen uber die dynamis che Stabi l i ta t vonSeeflugzeugen auf dem Wasser. Flugbaumeisterarbeit.5. Sottorf: Start und Landung im Modellversuch. Jahrbuch 1938der Deutschen Luftfahrtforschung, Erganzungsband p. 396.

(Available as Brit ish R.T.P. Translation No. 966.)6. Sottorf: Analyse experimenteller Untersuchungen uber den Gle itvorgangan der Wasseroberflache. Jahrbuch 1 9 ~ 7 der Deutschen Luftfahrt-forschung, Erganzungsband p. I 320. (Available as NACA TM 1061.)7. Sottorf: Versuche mit Gleitflachen, I I I . Teil . W e r f t ~ Reederei,Hafen (1933), Nr. 4/5. (Available as NACA TM 739.)


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16 NACA TM 1254


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Scheme of a measuring- sheet r eco rding~ " )?Xh ') ( ".c ; l ( (( "

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" , , ., ,' ", , " , ," " " ' / ." ' a ; " . ' . " . ; - ; - ~ - , \ - ,, . -,, -

Figure 2. - Measuring apparatus fo r porpoising tests.

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f-'-..:J


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14

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+0+ II~ (3')...... ~ Unsfable region"-- ............... ~ @r-- I

: ~ ~ I - -r-- (5)~ -- ----..., .,---~ ++~ +r--... +~ ~(J)~ ..sfoble reg/on+'-..... ~ -; r~ +

Sfahle cOI7e/diol7 . ...............Limdinq cOl7difiol7 --- +Ul7sfob/e C'OndifiO/7 -- Io of recording in FiCj. 4 ----.--nsfable reqion 10I I I6 7 8 9 /0 I I 12

V in 'o/sFigure 3. - Basic test. Float design DVL 18 with wing and tail plane.

(The numbers in the circles referring to parts of figure 4 were incorrect in the originalversion of this paper and have been corrected by the. NACA reviewer.)

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NACA 1M 1254

.J ao l(Keel in contocf with wader~ svrFace)- +A tTifucieIt''T0V=6.16mp, a.:#=11I.2 js fable

s//qhf PO/"flo/sing dlle 10I ..... - ~ t-rol/Med i#cder-- - ; ; t m m e r ~ / o n -! to ( K ~ e / In contacT w/lh w t 1 f ~ r sur(.Yce(a) 6 ~ / S : Photograph f i gure 4(a) shows a s t a b l e

pur

ru n fo r a* = 1 4 .2 0 A l a r g e r p a r t o f th ea f t e rb o d y still p a r t i c i p a t e s in the lift. Th eco r r e s p o n d i n g r e c ord i n g i s N o . 1 from f i gure 4 .The m os t l y i r r e g u l a r s u r f ac e waves rem ai n i ng 1nth e t ank a f t e r s e v e r a l t e s t runs in s p i t e o fwave damping th e h e ig h t o f which has beenreg i s t ered wi th 2 mm at res t cause a c or r e -spondi ng p o r p o l s i n g . Th e a t t i t u d e 15 n o ti n f lu e n c e d t h e r e b y . Th e upper unstab lerange i s n o t i n c lu d e d a t t h i s speed .

..t aD_______ ____ l - - - - __--

~ t". (0

19

Figure 4 (a)


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NACA 'I'M 1254

I I f 2 . 22I I Io v=/Om/s, c t ~ " , / O . 9 I Lim/!I I I IS v p e r i m p o ~ e d 05ClllofiO/lS 01' 9"tlllielC>'rJn I(c ) 10m/s: Photograpg f i gure 4 (c) shows a s t a b l e

ru n fo r al',l = 10.4. The s t ep 1s no l ongerloaded to i t s fu l l width (b n a t < b s t )' th eaf te rbody i s the re fo re under s p ray e f f e c t . Th erecording No . 4 , a(.c. = 10 .90 t 1s an example fo ra l i m i t i ng c ond i t i on . Th e a ~ p l i t u d e s o fporpo is ing and p i t c h i n g o s c i l l a t i o n remainc o n s t a n t . Th e f r e q u e n c ie s o f both o s c i l l a t i o n sare the s a ~ e ro r a l l t e s t s ; l a rg e s t at t i tudean d h ig h e s t p o s i t i o n o f th e c e n te r o f gravi t .yalways co inc ide .

21

Figure 4 (c )


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NACA TM 1254

(e ) 6m/s: Record ing No . 6 shows an u n s t ab l ec ond i t i ono in th e r ange o f th e hump fo rao = 10 .9 ; th e a f t e r b o d y i s still loaded .Since th e uns ta b le r ange here ex tends tohigh a t t i t u d e , an a i r p l a n e which overcomesthe huap with a c om pa r a t ive ly low a t t i t u d enay in t h i s r ange be e xc i te d porpo i s ingwhich i s damped o n l y when th e a i rp la ne ,under fu r ther i n creas ing speed , enters th es ta b le range .

23

(f ) 8111/S: Record ing N O . 7 shows an u n s t a b l ec ond i t ion fo r a o = 6 . 7 , g l i d i n g c o n d i t i o np r o p e r . The a f t e r body l i m i t s th e a t t i t u d efo r maximum p o r p o i s i n g .

(g ) 101l / s : Recording No. 8 shows Once more al i l l i t i ng co n d i t Io n ; the model i s i n g l i d i n gc o n d i t i o n proper ; th e a f t e r b o d y i s in c o n t a c tw i th th e water dur ing th e o s c i l l a t i o n .


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3

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/

o I I , I/

9 7 % ~ "IIII Mod 5842%: 1 08+V222000 18 oJ u 9000024

+ I oJu 87 I I0 OYouqhf of}w 110 000/8 00 0 ~ 6Br- I09 Y85 oAr 19S oWa:l 08+V 138o B+V139 oH e 177

I . I I I , I , I . I ,I 1 1 1 1 11 --2 3 4 5 6 7 8 9 10 20 .(30 40 .50 60G i n fons

Figure 5. - Coefficient of the moment of inertia as a function of the flying weight.

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~ k..I ~ ~ ~ ~. ~ r--. ~ ~f ' ~ --r--..K ~ ~

I ' ~ t'--~ +,~ v ~" ~ ~ I'-... ~ ~- Floaf alone (Model 58 I ---- ---- i-11M , Withl"""qI nd(O"i 'I ( . # t ~ r--- -

5 6 7 8 9 10 I I 12V in mJs-

Figure 6. - Float design DVL 18 without wing and tail plane in comparison to the basic test.

~f;:x>I- 'f\)'v l+"

f\ ),-n


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26 NACA TM 1254

..... "'=:: ...1' ~ k h ..~ ~ ~ N~ ~~ -=tS ~(' ,~ ~ ~ c .~

~ ~ ~ - +~.. ~ ~~ ~

,.... .-0 f' -' Yz bSf before sfep , ~"" ,."0 + y.; b II II t r--- 'S f ."h ':\.r - - )( OYer sfep (iiJferpolafed from fir] 8 a' -


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NACA 'I'M 1254 27........- I t A" I- Ca =r6T. 185........ --r12 ' ....... . ...... --- r--r-!:i!!-. -. 0.17'1 (/h ',r J'f alJfldy /il71i1.rc--- .

~ r - .- 'r- ' - - 1 - - - . ---- -'"

-...... 1 - '- 0.97. -.... t- - _ _ -10" ......... ' ... ---......'-. ............. ..... ..... 1.81' .... '" '-... ''t ..t-....1'-. ........... -......!,.P9'. ' r-- -..1- Lower Sf q!Jil ifj !tin/Is'-- :!If. r - -i - -f " -- - 0.37 '- , --- --,.:. - "" ---1'-4 5 8 I I 8 9. 6 7 8 9 10 / I I12v In m/sFigure 8. - Influence of the loading.

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28 NACA TM 12541-1 0

12 0 " ....., ~"- ""'-10ot'"

'"K., "" --... ......." ~ ~ " ,8 0 ~ ,'"' " ~

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1_ vf " l f 9:K bs+ e 9II6 7 8 9 10 I I

V in m/sFigure 10. - Limits for direct and indirect towing method.-- r l l i lscCile des '71J- - Mode!, withovi sIJp.sfream inf'luence- ._. wifh 1/' ./11f" I I 1 r


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NACA 'IM 1254

Figure 12. - Planing surfaces with 130,140,160, and 1800 keelangle.

29


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NACA 'I'M 1254 31

12.5 .I-J6

liZ.$"+ IZ.5 iy'2.5+ G c - - I--". 12 .5 -V'GJ;./4 ' ." /7.5 ~ r 1.8 / - I--'11 I 12.5 2..14+j I ~ +12,5 7.5 2.89 - I--i 5.0 2.89/2 + 2.5 2.89 - I--I ~ + 12 5 ' \ I' J..-..+( .1 1,,\ O + o - ~ - > ! p I10 +,2.5

+\ \ ~ t - 2 . 5 L 2 + I t ~+/2 .5t-- ~ + +2..5+.(. t--- \ e" ~ ~ G = I 7 . ~ l r q 12.5f- 8+ r-. "" ~ ''''-r--. Ir: r0 +"\ ....... +2.5 N:---.-.. ~ +f '

1"-' ') ~ ~ f"-..+ ............ ~ l r q I ' < + ~~1?5

+ f'-.. /It .... ........... ~ I r- r-- -I' r - r - ~~ b r--~ ~ II>- ........ r----.. ~ 2.;5 -r--r--t" - r - ~~ --..""" -...... I"'- r- 5.0119 -... r -2 r-- t :=-r-- ~ 2.51r9r--h ~ v In mls -.-... r - -5 6 7 8 9 v/ o // 12I I ..1

Figure 15 . - Stability limits of the flat planing surface.


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NACA 'I'M 1254 33


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NACA 'I'M 1254/6I, t; - 1800 ::.-;?14 0I 160 0 7'-:; / 'I --' ~ = ~ ~ , / 'I- /2 - -I - '- ' - ' =1300 ~ P' ./ f"'7I . . ;7 ./V- 10' ~ 7=1 . /"I -I ./V" / .....-::V V- 8 - ~ ~ V'I / V ~ , -, V / " " ~ ~ ~ ~_6 -' - =6 - ~ V ~ p- . . . . - ~ ~ I.--:~, I ~ / P ~ '""':....a V , ~ ~ ~ 7 e 8 ~I- 4I ~ V ~ / .- ~ ~ ~ I - - ~ -,&o.l ,..:;:; --- # - ~ V' ...,,& V ~r- 2 0 ~ It A*I . ~ ~ ~ ~ 1- ~ = rx 1. 3JII 0.5 1.0 I{ I 2. ()

Figure 18. - Influence of the deadrise angle for planing surfaces.r - /6

I/ ~

35


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NACA TM 1254r - 16-

I1 "r- / 4 ...... . .....I "- 'N" --,...... 1-"" ~ k Efrt!'cf of cdter60djI1 , ... " 'I' l"t...... ~ ~ I I t"b.. Ca =3.012 0 II f\:' I"--. ............ 1.... 1 iJ.f h.... ......f'::: r--.... r-....I (\ I'N ....-f-: ~ ~ ' I ' ~- 10" I r-.. - Fore/Jodj /9 -I ( -l l-- IY .......,; ~ -.....; ~ " ...... ~""-..' ~ ~I . , DR ~ ~ ~ f'-.. - on. /9 -8 - r-J r-.:::::: ~ b.. I" -- P/oninqsvr/oce,- I. 1,1< -....:: ~ .......... - Ir-... ~ r......, '.5 ~tS ~ I"" ~ f;;.::, t'---..... -- 6 Ib .It ~ :::::::::: ~ ~ .......... ............r --'"

.......::: ~ 1"-0-. ~ f::::==,.4 - r---... ~ ~I .... -...... ~ "- 0 .5. -- - ~ 0. 22 ' --+- F= v '- - J--", 5 Vgy bSf 7I I I

Figure 20 . - Long fo r ebody DVL 19; comparison with float DVL 19 andplaning surface with 1300 keel angle.

-


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l2.0 t;;T = 6.042.I

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c, :. 12.5 kg CJ=IS62I.S I [ I I J I 1.5

1.0

.5

5I3

I{OJ) 1.250J 0.938I

5.0 0.62!i1I2.5 0112

6+Vin m/s

f! I456F

c:1.0

0.5

10 '2,7 [3

5 6i3 4

ICST 7.50I I IG.n", (,.2.,86/5.0 1.875

I I1.2.5 1.562T I10.0 1.2500.. 0.625

},- I0.312Lv,,.,Im/sT I5 6F

107

2,8

305 11 I i I I I If =9./9sr I ..'0 1 1 1 I f : I ~ [ I II2.5 II I II I

II rtt--i--ir52.0

C-rex

1 1 ~ 5 6 2!.S

10 II tit 7[ t O'''it I a5 .0 0.625

0.5 II I II 2.1 II ~ . 3 1 1 1 I I5 6

3 .,. ~ I 110.5 6r 7 12I8Wldih of 's iep Figure 22. - Scheme of investigation fo r the series of DVL float families.


39/50

NACA TM 1254

I ......... . ......- 16'I -...... r-.... ............ ......... - -uP/,((' sfabilli), l imifsI ~ ~ ............r-_ - . . . . ! ~ =1' l .Skq - Lower " "f - /4 2.68 II 1.62 .... r--- r--- 10.0 "9.. r-- _ ~ ~ ~ 7skg -I .... t- -t- _r-n 2.08 1- - r- [ - Q _ ~ . 7 8f- /R ' -= l


40/50

NACA TM 1254

I "- . 1':1J .,f'..,. G c'/*Tr" /. 56I ...... ......... 0 t--.. /5 .0 1.7 1.. /7.5 1:


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40 NACA TM 1254

I) - ... l.,....o~ I F"4.!!,.I-)....- .1)0 v v 15.0 ~ 10- Q ~ a s ~

......V .... ;;; .. . .... ... I--I , . / ~ ,- ?:P I-- with F . s ptII'qmdtlr12" ~ .......' ~ ... I - ~ .... 9. 0 ~ ~- ~ -I-....1. .... ~ ~ : : : - - ~ ~ ~ I- 'o! - -~ ..... ~ ....V ~ VJ.:Y --""1 V ~ l.,....-v V ...."'" .... 6.08 V V I.,....- .... V .......V V 6.s - - - VIper .Nq/J///fy limils6H 0V.......V ~ ~ I / r;;- 7. 0 f - - I-- - I--V V - ower " "Ih V V -- ~ ~ u~ . ~ t:::::: ~ ~ !?,O;;;;iii ' .S,.....

It A", - t - ~ C ~I 0.5 I.t) . 1.5 1 I If RiO 2 .5I I

f-16j ..... I-r-_ .1 * r t - - + ~I - r- - - ... l- t:/4 ' with c: as / X 1 r g l J 7 ~ f t rI- ... -f. r-- r-- r- ...- - ... ~ C::: I.UI - r -1 ... r--- -r- r- r-: r-::I.c." be2' l- I - I ...-r-: ....... t---.b... -I- r-r- l- t-- !J!_ I- r- 1- ..... ...


42/50

NACA TM 1254 41

I I I16 u F= 4;0-I v i ....... ...1-- I-I ... ~ }O ~ - o{..- as f ( c ~ )14 0c1 / " ~ - I - -~ 6. 0 .... :- wdh f as fK/rdl1lder

12;0 ._ ...V .... f...- :fa.- --

'v

~ l - t:::: - -1---I-- 8. 0.... 4. 5 L--~ . . . . . : ~ ~ e:;- ~ ~ I- 8.5 ; : .40 .......; ' - - ~~ ~ v ,,' . /V V ........ V I- - . f . ~ V8 0 '"" V ......V V ~ ~ L V ....." If V V ./ V ".... ,.-V~6 ... / V V ........-I.-' ".... ... 6.5"-" - V / V V V "....V V ::::.- ".... V-' " - - - tJl'l't'1' J!qbildy limils~ r/" -" V V -:::: t:::-::4 -:;"'8.0~ ~ ~ ~ ~ ~ ~ ~ ~ 8.5 -- Lower II /II~ ::a ~ ;;;;- 111 A- I-- cQr-;:;pO./i 1.0 1.5 . 1 2.0 2. 5/6 ......." ". i'--- .. ... r-... L,I 1 " (1$f{F)+......I 1- ... l"- I"::'1 t - I"-Co =2.01140 r-- _ 1.7S' with c ; 115 p q l ' d / l J ~ / ~ r'I ~ - -- -1- ....1 r- f- -I - ~ _-t-- _ r- I - I - I-- 1.,012 - i - - 125


43/50

42 NACA 'I'M 1254

/6 "I I

a'*as I(e:)I 1- with Fas pardlJ7efl?1 f- -I r;.f.O ... f..- 112" -I -"""6k j::::I::: - - iI-:.- .5.0 -l- I- - t..-V I,..- 1,...-==101- ...... ~ ' - r - r - 1 . ~ ~ ~ ~~ ~ ~ 8 P ~ ;;..... -...-- , .... , .... I-- ~ . 5 ~ 1--po 1..- ~.. ~ 1.,.....- v 6. 0 v - , / V ~ 4 . 0 ~ ~ ~ " 6 . ~ ~ ~ 1..-I--'8 . / ...- I - - J..- -. V V . /V .... ~ " ..-V ~ ~ 70 ~ V- 't!

6 0 r / ,/ V V V ..... ~ ~ V ....... 1,,,,/ ' ..,.- ~ ---,/V / ' . /V ......-V ....V --- --l-I - - f..- 8.(,/ .V /'V V V ~ ~ :.- I - -V .... ~ ::;...-4" ~ ' /V ' , / ::-- ~ t:::;; ~ ~ .... - - - l/l'fJ t' r sfcr/Jildy' lim;' fs...: ~ ~ ~ .......-:::::;;;::,; IOii""' - -L ower " /I* Alt I- ~ Car nO.S 1.0 1.5 I \ 1'.0 2 .5I16

1 a* as f(F)I with as JJ(Yiamelei_. 14( I I'- r L : = ~'- c ~ 3 . ( } ( ) - r- - -- 1.2 1-


44/50

NACA 'I'M 1254

I- /6 - :::::: I::::;:::: .5 0,:::::::: .25I k::::;:: .;::::::::. ~ O ; --14\

A ~ ~ 8 . 7 5I ~ ~ - I -i- 12r 0.50 C ~ ~ / . O-.....:a. / : . ~ -- --- -;'"; '7 ,.............-: ~ --- ---..!:,::10 ' / 0.251\ ~ .;:? ~ O0. 75:I ~k7R, ~ b:?'./1 / '0.5 0 - - Upper slob/lily !;ilJ/ls1- 6

4"- \,Z

1 1.00 ~ - L ow e r .. "l a ~ a5P

: ' : : : ' ~ 2 5AltC -::i /,/2n- 2 .b;,

0.05 O.{O 0.15 0.20

Figure 29.- 0.* as f(cB) with C * as parameter for DVL 17.I I I_ /60-+ - -+ - f - -+ - -+ - l - -+ - -+-l--+-+-l---+--I-1.7S 2 0 0 -___ ~ S O

43


45/50

44 NACA TM 1254r /6 "

1I I I I. .l I 1 I I I I I- 14 ' Conddi/J1J5 r a r y / / 7 ~ 70IYOrd O"f"leroody1 ~ - r1 ~ . ~ ~ \/,-'0.' 1.25 ?7S- 12 ''I ,...-: ~ ~ 7 $ C a ~ ~ 3 . ~ ~ ~ - -I--- -....


46/50

NACA 'I'M 1254Fc/Yl//y A Famtly 8

DVL la, 8 , 7 ) ~ = = / 4 0 DVL 17,18, /9 , 5=/3014r I ~ l o a ~ n q ~ / i n Jf\." "- - I ~ ' . ~ JL oadti?q Ilm;l ,:r;: ~ ~ . O O2" ~ 2 . 2 5I "- " D J - - ~ " " ~ r ' - ~ ~ , . 5 0 -"-. i'--..:: 's.!?-'-f!.!. r-- t- . ~ J I . 5 2.00I I'---- i ' - - - ~ r - - - '- +... - - r - - - ~ ~ 1"0 -

I......... ~ - "- -- r - - Q ~ r - : : -- ~I ~ Q) ~ ~"- I~ ~ , ~ >;! ;;t :;;! ~ - -


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NACA TM 125 4 47


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Date post:	14-Apr-2018
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NACA TM 1254 Systematic Model Researches on the Stability Limits of the DVL Series of Float Designs

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