A 11ractical alJIJrOac11 to rucI.dc.r c1l'sig-n fIltl,t.-r fo r To will will (1I11i (1I11ilthe lthe'' service service
a shi ship p whkh whkh rt:qni"'l rt:qni"'lI\l I\l''lIts a 1111al 1111all}" l}" olher olher l'arti l'articlI clI!! :tr "wun's requir quirem emel ellt ltss c:l! c:l!L L oftl oftl''lI . be a 1'1' 1'1'0 j.- l '..L..iu . itse itself lf.. ;\Ia ;\Ianv nv Illl Illlll llee tl'~ tl'~ts ts with with 1I\1 1I\111 11kl klss and partic,;larly Oil h el elanl shi!,,; in serv serviice, ce, will he I\( I\('n'ss ss;l ;ll\ l\'' tll tll ('st ('stah ahli lissh or l1Iod 1Iodif ify y th •. Illt Illt''or i,'s' ,'s' lIpo Ipon which hich rudd rudder er dl:s dl:sig igll ller erss Ikp Ikp"nd so lI lIlllch. It is Ilot Ilot wilh wilhil illl tIll tIll'' SclI SclI!' !'e: e: of thi thi ,; arli arlicl cl,: ,: to cover all tYl' e,; of nlll nllld" d"rrs, thc'r hc'ree{ore {ore ~iil ~iilgl glee ane ane! twin twin--suI' uI'''''''- ships ships wit wit h rudder rudder:; :; at till' sti: sti:1'I1 ..\· ..\·ill l,,~ cOllsidl'l'ed_ cOllsidl'l'ed_ - The The auth author orss have have sift siftL' L'd d thro throug ugh h lllt llltl\ l\::h of t1w ;i\-aila ailahte inf' l( nl nlal jll jlln on this his . subj subjeect am! snll snlllH lHiit tit\ tit\.' .' r" r"llo llowing ing as their sugges gestiol tiol!! for for a prac practica ticall appr approa oach ch -liiiT( liiiT(Tcr-(ri: r-(ri:.~igll. Th\'le arc many argu argull llle lent ntss for for an anll :I;: :I;::J :Jin inst st the the ......-ad adou ou,; ,; melho melhods of ta tackling this problem an\1 it llllIay he worlh noting at this slage that that this this applicatio application has has pW\' pW\'eu succ succcs csssful ful OWl OWl' a PCri PCriO OI! of ycar ycarss with ith .••. .••. arious \I vess vessels els larg largee and and !>!I !>!I!~ !~..!1.. !1. . The per perform forman ance ce re'l e'luirr uirrt! t! from from the !l wh ~hjp hjp is tlte tlte ba~i~ ba~i~ U~""!l which we mw:t select lhe type of r m!der m!der . A ship whic which h sJle sJleil ild d s n ws wst 'Jf it;; life in the "l'rn sca ami whi(;l, when it is in harb harbou our, r, is llI:l llI:lno no,,'u\red tugs,, will will br tugs 1l"l 1l"lui uir\ r\'' good good cour cour s" !;; ;;(('l'ping l'ping fJuali fJualitks tks with with lill lill k .colTecti'· colTecti'·'n f"Hit the! helms· helms· man. man. The The tllg tllgs whic which gnide this .••es': es' . :e1 \T :l· will will rc. rc.qllir qllir (' a high dct;-Il'\ dct;-Il'\.'.' or Inal1<)(,' Inal1<)(,'11 11 bilily. bilily. A warshi rship p Ill Illay be re reqnired tl.> llavc lavc a cert certaain minim inimum um tacti actica call ('ia_ i a_ .mrtc mrtcrr ami ami turn turnin ing g ·cir cir e!l e!l'. An ap apl'ro:'.: '.:i. 'mate guide to the anlount of rudlhor . area area usua usuall ill ill sing single le :\I\ :\I\ccl twinin-scre screw w ship shipss is giv given en ill ill Tabl Table 1 (ref (ref.. I). I). :l
To
which ich woul ould r~su r~sult lt in loss loss of of pro propu puls lsiv ivee in~ in~'csti cstiga gati tinl nl\\ once nce again gain into into th~ th~ lll lll'st 'st . . cHic i\' i\'IIl: r. :nr3 :nr3nl nl;~ ;~", ",~n ~ntt for for op"r op"rat at ing ing cond cond it i,JII i,JIIS. S. It is n:colIIlII\'!H(n (. Figmcs colIIlII\'!H(nl t h at at for ~ lt ltil'-; wi tl\ t to 6 show some of the bdt\'r known typ"s of ru;lders. SOllie (",twanl turllin~: prope prop elll'rs (I hat is OWlI OWlIl' l'rS rS hay\ hay\!! ddil ddilli lile le prdl prdl'r 'rll'lIccs, hut st;uho: st;uho:inl' inl'c1Ol:kwis c1Ol:kwi se, purt :mtic mticlockwise it is geul geul''ral rally :lccl lccl'p 'pttnl toto-dar dar tha that if I,,( I,,(,,king king forw forwaard) rd), the the I1ll 1llldn ldns lH~ l"',.,i , .,i--II; II;)' co~ co~;t . will P\'llllit, the .
l
lOe
m'J ,
, i.:-:-'~
~r,.
I
)
)
~ .. ,I ( I
r '!
,
I
,
l.
/
. .----- ../
,,--.
C f·-----
' 8 A t A N C £ D
I
)
. . •/
_.'~
--t·_-----
B A L A N C E D W I T H SPILL PlATES
-~JlL_ !I
f\
1:*,.J - ~-~3=3 V S EM EM II-B AL AL A AN N CE CE D
Fig,(. 1-6.
B AL AL A AN N Cm Cm SIITIl/!
C AN AN TI TIU VE VE R
S PA PA DE DE
S EH EH II- BA BA LA LA flfl C CW W
O N H O R tl
oj oj the bettcr bettcr lm. lm. ,m· ,m·1l t)PCS t)PCS oj rudders
be used as these gi\'(~ the ImaximulIl acid!',! al!vantage in this being' easier thick hickn ncss css at :llJ :llJ per cent ent o{ the the rudder l-eml emll"'-:. '-:.!! of prope ropell ller erss anti nti stcr stcrll llttube ube liHC'n High SflN' SflN'd Atblltk Atblltk liHC cho ch o rd frol fr olll ll tlle tl le lead le adin ing g e\li; e\ li;e, e, als al s f ) t h e i r s h a f t . i n g . \ V h e l l t w i n f l l I l < !crs !c rs a rc pnt pnt ~~O'.i~ i~-< ~:lnl1d shi ps ps (·(.,3,2 leading cdges arc not too !lllllit and over to their maximum all~le there !,hl('s .• . • ••• •• L:ut:" L:ut:" c.ur,o ur,o aod P;\~" ~"4 4"Itg "Itg"'r "'r ~hir ~ 1"-2· -2·1) will tllcrcCore not ir irnprdc propulsion. 5hou1.d Hot h e any protrusion beyolHl J;}~sC"II~; }~sC"II~;r r r r ships ~11\.'11r aq;o :lnd lJ; t'Wl1\-srrew IIfC ' p.al1 vIew 0 {Itie s Il'ip a t tlIe Ioau.1 I''or 2 ·J r /'. (O.utrJc; .• .• .• •• •• t If 2t··7 0-·, ·,J·J J·J s Iu"ps wit II wl'!\g 'Ssds . :a.nd frrry bu:)l~ Tu~s. rih>l v C ' 'Ssds. )l~ 2's-(' -('O L rfuu rfuuli lil' l'rs rs.. a mini minill lllu lulI lIll of 30 per cent watl'![ line ine ;L<;indicated hy Z. Fir,. 7 - . j j ---------------------of tlte dep depth of thll hll rudde udders rs is rccol rccol!\ !\-Oa. Oa. hoU hoUII sill sillgl glee ;\nl ;\nlll twin twin scre screw w S'dp5 SOll\e ll\e owne owners rs m:lY m:lY sI'c sI'cccif,. if,. good good tIla Ilallll1II 1IIl'IH l'IHllell to exlel xlell( l(!! hcl0 hcl0w w th~ th~ sha shaft the top top or root root chord hord of the rudo rudole ler( r(s) s) "'alalo\\' alalo\\'11 of tlllW. ocellI'S at ' ; •..rv rv often often Iii ie'l. [( ihii ;;iiii:- allth"r ':' ':' know there is no 11\1 to llatc I . . i;' III III\\(' \\('r :ill :ill!: !:It It!so !soff atta attack ck,, The The hrea hreat, t,do down wn'', i;'d:d:-\I. \I.1C'·'! il. il.ll' st.'\lek cI _ ' _ lIi. lIi.r.c. r.c.iillc ...'. s.ho s.holl lli\ i\ii info inform rm::" ion as :I1'l1!i":Ih'e 'to "hil'S. !I . 111\\\ rvt'r .' )10\'; reC01I1I1I\'IHk,1 , ", (c :wcd to lal~'( 'r rllcl,kr h,: :-. -.llllut llllut :!I lHlH-r ..cc ..ccll lltt (.Jf the. the.lllaxillllllll .. 1~l'· 1~l'·W:lr ·..h in avi aviiltillll )10\' .( -. -., nlll· nlll·) ••• •••, '1>" tl I ' • Ie Illl 1l\'l\ 1l\'l\et et:: or the the JIl. JIl.:: pelln pelln dill"!. fill' fill' h'llll llll st"\ st"\'I 'IT\ T\!! ':es ':essd sd :l, so, a~ to' to ' the II"·,: of of ~pill plall's on the "1'1,,!r 1\'l'e\'t. l'e\'t. r at atlll!\ or 1·:1· :1·'2·;:; arc fic slIre it i~ no not o\'('r-bal :tll( tll(,( ,('" '" alll! lll! sudan' udan' of the the will willl: l:ss ,.• ,.•f cert certai ain n tyl" tyl"'''';; of 1.\, ,'. I f ,:1\.· ••,1 airc ';" ';'; Il'llol,t """\11;1' ""\11;1'11111" 11111 " 1.' 1. ' / V,'ss V,'s s " h w i t h I l " ; l r i r t q l \ \ ' i.iil, i.iil , ! n o l 1 1 I , mll-l ml l-lI I the th e helmsm hel msman an. . hi",1t ai rcra rafl fl. . a nll n llta tabl ble e , ::'(: :'(:lIl1!,lc t. '. . . . , .•.. 1 ' " f ,,' I'; o{ prim "1\l "1\l1l 1l"~ "~!, !,\' \'Cl Clal al rl'l rl'lll slIlt-r lIlt-ral, al,"", "", iii:ii iii:iiiu' iu'lln llnalt alti!i i!ity ty primcc impo impo,, tann tann:: Iwil Iwilll ll:: the the COII COIII< I<:\ :\ Hoy Hoyal al Air Air Forc Forcee , . p,.,"d\1"1 \1"1'1 '1<<-.a .a tlll tlllll lll\ l\'.'1 h~ Iow thnl thnl twill ill 'rlld rlldd dns ill th the raCt raCt:: ot ot twin twin Tra Tran'. n'.I_ '-·'lt <:Oll1l1 Oll1l11al 1all'\ l'\.. EXl'< EXl'<:ri :rill\ ll\"lI "lIt~ t~ "t'" - I " S('.f('W .. ~h~l .lIow •.J ' ."111 "'d .. ( r d , . by T . 2 ) . ••.•." 1 ,, ,1 .1 ,· , ·s" WIlI WI lIII II,l ,l It" It " !uin: !uin : :I' :I ' s h o r t s e n ' w " is i s . rt'(: rt'( : ()ll\Il . . W!l<'lh\ W!l<'lh \ ·l' ·l ' tlll:s tlll: s c lI:-. lI:. Ahd . t illdic;'. illdic;' . It! It ! that .\ . . . . , I . . ." ,••. ,••. I ,,'t.II,· all,l all,l I'O" I'O"'l 'llo loll lle, e,1 1 slI slI arl! arl! tll tll 11\: 11\:),o ),o :; :;iti itioll oll"d "d illhll illhllald ald Ill' Ill' llI1ll llI1ll"' "'::lr
,~i?:u'tto
:ar
" r
3to
wa tl'r tl,)willl; O\'cr tite rOllt chord Oil to the luw pressure ~ide of the rud.lc-r :SWill bc ;lvoidc,! al1crcclIlal:e chord balauce recollllllellllt-
a
s ; ; : , i''''
1
•••• '
~~:~s.~~~~·~ ~;~~~~. --J'.,,;III'l'H:
~t.
J
\:-I"bu:
_~~ #
•••••
~:\
,:)\:,. , , '-tJ~, t :~
~ Sllccif t ",! rl'quirer tll'llts: One strc:\1l1~inc,1 lJalancl'd .rudder. LX.d = !"II)X 1O
-:J
",
'}<.).:')
!
.
:.:.._--~" :J·85 ft.
Peak lorq"~
7· GG J·lte aSlwct
ratio
will therefore
7'0
_.:... = 1-99 (recollllllended 3'85
.
= 0·31;
he:-
l'eah lorq'lIe (going :lstem) Normal force Q =Q-():J5 ;< 29·5 (4 X 1 . GS!W X 35 = I,O.'iO 1\',;. =1)'7·1 tou. Centre of pressure at 35° rudder :lngle X :1-8.'i =Q':l75t = 1,·14 fL from af ter edge of. rml<.!er.: Tor que le\'cr
C()l\sideriu~ the celllrelinc of stock and the clearance from the leading' edge of the rudder which we re< prire to llllship thl' propeller. tlte maximulll of ! ft. I i n. of the chord is permissihle. This gives a p nccllta ge chort! balancc
o f:-
1.08
=2'77 - 1·44 = J -33 ft. 3-85 ; As this pl'rcenlage chonl b:dance C'-'I;l~S P':ak \orquc COilven it'll t1y with in the rall(;e (~G-30 =1-:1:1 X O· 71 --
oX
100 =28 per cent,
})er cent) we lIlay be ~atislil'd with thc = 0'~S5 tOilS ft. outlir\'~ (If the rud der. \Vt~:trc restricted Allowing a margin for frictiollal \0 a ml';\ll deplh of rudd er of 7 f t. S in. losses ill the steering gear . beariugs, etc.,. thus the ck;\I'ance betwel'Il the hull we shall requir e a steering gear capalJlc alld t he rout chord (see Fig. S) warrants of dealing wi th a maxill1ulli tor quc o! , . the fitting of a spill platc.R/eIIAI'O D.$£SJACIITf(., sa)', 2·3 tons ft. Penh io' -qrlc (I'oiu~ nheadj . , ;.:)' N 01m.1! ~ <:rce ~ _ . , =0'03;> A Y-O (3).. -----~.
= 0'0:35 X 29· 5 (II = 12.-180 Ills.
= 5'57 tons.
X
l'GS9p
As a st reailllill~'d r~~.hler was spcciliel1 wc have show n II I bg . 8the proposed ru<1tk, sktioll :II\(I oHsets. The section is basel! OIl N.A.C.A. now with leading :\IId trailinf, cdl j!'s modifieu slightly 35 tal;c :lv;lilable TOum! bars in the t~vcntlla! cOllslruct,iun. Note in Fig. 8 n torsioll . box is inclicatel!. Variolis yards havc
to
X
I
-....----
t R~commcntlet.l const3nt
• Speed ill kllf>ts x I· liSfI:- ,pred in ft. per s~c.
- - - - - .~ tt[ - t.I lU D O E R r - -· " - 1 -' · -1 1-
STOC K
~~U
I
~
,
H C O t-lH E N D E D
,__ -
TOE
~
~\
.."
~ ._ .
g
[~~POT ..h ~ IO R E H'A~:l_ '~:""-=--~l'A!IS
/
ROOT
I
~ ~ -:~ \ d '- T !'-
for ccntcc of pr~ssure C1t JS"
'
SPill PLAH\
~
: ; / . iI
x 5·57
=. 2'01 tons ft.
1·3..:.2'5)
~
"'.
Centrc of I're""ure at :;5 - ru.llier angle this being thc lIlaXimllll1 re,!uir l'd . = Q-:J75t X (h<)lll = 1),375 :< J·8.'i forwanl edge of ; ( =1,·1·/ ft. from _ rudller. . - .[ ., u J-.I i 10r'1 < .' Icver E : 141 ft.-I·OS ft. =O·3G ft. .• i
l.et us ~ay_ lur tlus eltaml'ie, th:n Iln~ltippinl.: o f tlw rudder on tlte ,;in'n aller eud !illl's allows a maxillllllll nll':1JI depth of rudd,', of 7· fLM ill. ,Tht" :In'a of tlte flllhler, :!!l·5 sq. It., ghoes a Illean choul of:-
O/OR
~
~ "~
: ' \ ' /: -j F " -TORSION
BOX\.
9 ! ~ i - - I " ' i ' r - ; ;.
.
-'-
\
4
A - ~ - ! I / ~ I ; _ . _ ~ I·
V
. _ . _ . _ . _ . _ -
~ f..
·'IP",~ L . //.
SPill PlAlE
.
L.j.:~~_._.__ ._. _ IUIOO£1l orrSETS
S ~ ~ : ~ .; ' I-~ · l j '~ j~ 1 1 u 1 L 4I 6 3 1 j~dj~4Ii~ili~It-J?1 j 5 & 1 1
r - - - - ------7------ -~:: ~: ~"~~~ K ~- -- -- ~ ~--· · · i ~'ig_
7
(lI~OI'l")_
1'lil11
l· jCIV
of nft;r ('till ( I f hI/II
' ; !·:i r ,. ll: (rig"')' EXClIII/"r. of ru.ldl'r 1/"5;'/;111'11 jor r~"ll' l·'·.
. !.--."I.I.-'-~.r ( ~_··-·-r-·-'
:·t~-,~ . - ' - ---:c - - " - - r -...- _t_r ' .:..t._J_.! l - - L _ L .. ) _ O IJT l IH E
10-
,
~
Of srILl,"
i,t R A O .T .E .
0
t.·
f~·~
6
-.-.-.
7'
.
6
--------- . _ - - . •~
5
4.
- _._ -_ .
J
2
I
".
- ·7 R A O. • -.U .
-
N I ' r ..
I
i
,
'?'-,-
-
q '"
~
5' ~ .""
v
~ ••• ••
tliHl'rt:nt l'rl'fl'wnn·,;. drop pintle \\Ollll! bot tom ·b<.'arin~,
in this c~~:::p!t: ;\ l.•e located ill the '
':. ?
Example II (twin siolls)
~
Spcdf it·tl rC{luircllIt"1lts: Twill slr {';IIIII linctl habnCl'I! rlllle kr :.. [igh Ikgrec of mallocU\'Tahilily reqllired.
~
.,.
~
~
J. X cl
: )
:) :) ~
:)
' j
'"
:)
?
::I' -:)
9G X JO <~5 ,~ !lSI
Que rudder
are:t
"J
'J :)
? ~
.
S'I.
=
5'75 2' 93
=
!
1.93
tlere again we can be s:ttisfied wilh the rudd cr outline. It 'is r ccoIHmcllc!ed Utat a s pill plate be filled to the tip ch ord (s('e Fig. 9).
Nor m a.l f orce (onc rllthler) ~
=0'0·11 AV'U (rd. 3) =O· 0·11 X 17' 2 (II xl, 6S9) s X 3S = 8,fiO O Ib5, =3· SO tOllS. Ccntre tlf pr ;,ssure at :J5~rud llcr angle
J'(III;
tC)}qul!
edge
Torque
=2,15-
., O··lf i5
tOil.
J .j[lH 7
Fig. 10 (lc fl): Single pl,,' e
Norma.l edge of rudder
0··155 =0·468 tons ft.
TIle
pea!;: torque f or twin r ud clers 2·28 tOilS ft. Steering gear manufacturl'rs ar c always w jllill~ to give :!cl\'ice on thc selectiou of lhe most suit;tbJc g~ar fer e:1.ch. p~rticuJar jo b. w :] be
screw,
saLlle dimen·
d =9ti
X
Oile
si,ngle
10·25 =9S·1 sq. ft.
Front T:lble I per cent L X d {or single screw tug is, say, 3 JleF cent. 3 per cent of L X d =3 per ccnt of 9 84 = 29'5 =ar ea of r udder O U f
mean depth
Chord
in s q. ft.
(see Fig. 10) is j ft. Gin.
length
29· 5 = 8.5 = 3·47 ft.
Aspect
ralio
Pcak torque (g()in~ al\ead)
Normal
force
l)'0:l5 X 29·5 (II
X
X 35
(-I X 1'639)1 X 35
tOil.
of pres5ure
at 35' rud , jer
angle
. =1/3rcl X 3,"7 =I ·1ti ft. from a it Cli= ;o : 0 f ::-u, juer Tdrquc
lever
=2·IOft. Peak
=
torque
2·10
X
0'74
=1·55 lons ft.
will r etluire a si.eer illr, gear c:1l'ahle of dealing with a maxilllulll tor qu l' of a bout 5·-1 tou~ ft. FWIH Ex;trnples I, 11 and III 'it is evid ent th:tt for single screw ves~cls Example I w ill fullil the requirt~lllCllt. For thc twin-scr ew vessel Example II will also be satisfactory. Ex:tr nple II r will also fulfil the par ticuJ:tr oWller 's requir ement, although Example I would he a mor e u p to date arrangement. _ The cust of Examples I all(l I I I would }lTobahly be a bout the s:tIl\c :lft(~r the two l'teering gear s and constr uction have ),cell considered, but Example I '\\"oul,1 he mon~ efficient. The rudder desir,nr:r has no ca talnl;ue from which lie call sek ct a rudd er to suit his particular ship. I Ie I IlU~t seek out availablc inlormatiun. decide on its v aluc and apply it, using his experience :tS a guide. RJt'U'F.HC~J
• "!:hi," anti Mar ine P;1I~lltc~. U. Rr ~l1.t=lnclt, It-tOI",!·.It,,, :JIlIl Slt'f'tiut: 0.1 ~ h il'''''' l.>r . Ir . )\'. ". A.
t
"~Ofll<"
m,,,I,·1 ""I'f'ril1l~1I11011 r11l1.lr (l r,l1n. ,ul'ut tJ nf the
• It.
\'i. L. G~wn
llll,lllllllon
of N~v~1 Archll
19.:') .
3 "17 forwanl
eclsc
of
;;tock .
ill,)
0'21 ft. =0'95 ft.
torq uc
••• 0·95 X 5-57 •." 5-~S tOll5 Ct.
--_ ._-- _ ...:._--------t Jbr UIUUlf 'u",J.·,' rOil' Lane Illr lo.'nhe 01 prtlltue at t it Oat I,t.lle
T. II .•
,' t'l'hlwl a 1,1.11":,1"".1\\"0".1." IL,tituhpn of N.lv;,. Ar I·hill·d ~. 10:1.1. f J.\Cr
lever
35· I' 'I'VIl(d
0'7-1
I Alt.-n.
a~ :JS~ruuclel" an!::le
= 0 I, Hi r..s~half di:l. stock (say 21 Pcnk
X 29'5
Van 1..ltuUtt·nn.
of pr essur e
=1- Hi It. •.
HJ8!»)' X 35
tOilS.
rudder H.
X
=12 •.IHII Ills.
()f Centre
r u elder:
Thi:" rud der
Specificc} requir cll\euts: plate ,unbalancell rudder .· X
IlllbCll"/Iep.tl
I w ill'
force
= 0'035 =
f ur
(going astern)
Pe lll< t o rq ue
angle
Pcaktorquc
L
.ll' sigllcll vessel
= 1.650Ih5.
Example In- (siugle sions).
V
1'
~~~R~'':J
5crClV
1·12 =1·03
X
! .
Fig. 9 (ObUL'I'). Rud,[a
Centre
=t ·03
\\\', J '
I\* t- ". . - f 2 : - \ " ; : ; - 8
lever
l'III ft. from
(goin,,(astcrn)
•., 1,1l~lI II ".;.
/
=0·375 X 2·98 =I· 12 ft. front aftcr
Torqn e
,~ n'0:17 A V 'O (I C :£ ' :1 ) ~ <. 0·t1:l7 :.; \7'2 (I X 1·6S!})'
i ;""i.~·"
'..
.
of preS5tlre at 35 " rlltkler
Centre
1/3nl dlOrcl
NIIl'ma! f"r{'(~ (OIH' .rtttleler)
-\
c t - - , · - - - - " ._
Iprel
• ·14 tons
I U i I\
STOCK
."ROO t ,;;- L _
-~.:::::::.c/
)1
I
=5'57
Pm/{' torq:1 1 '
X 3'80
[,'
' - " ~ I \ '- "
-. 1'12 - 0'83 =0·29 ft.
"', 0'29
" 'f~
~t
r"~···il'
8' 5 =3.47 =2·45
(going ahead)
forward
I,'
-..; "
:q..• -_ .-- =17· 2 sq.r t. 2
2'~8
~ 0'375 X 2·93 =I·I:!' It. from rUlltlcr .1'o!lllIe lever
I ,, - - - - ~
1
- - .~
rt.
The maximum clearance between 11wl'l'l1er <\nd lealiing cdge 'with rmlLler s 5et 1ft. 0 in. inboar d uf shaf t centrclines (inward tur ning pr o pellers) allow!: :t l\1e<111balance f mm 5lock to leading ed ge of 10 in. l~iving a percentage mean chord balallc'~ of:0· 83 . X 100 =27 'Sper cent
?Prall ""que·
---":':-'yHEt;
;',1 -. '
uimclI-
In this exalll pll' ·kl ns say that the r oot chord can he q uile dose to the hull as there are f ew constrllctional limitali,)(\s. Th c s haft cClltr elinc is pr oduced tu our a ppro:-:il11ate centrelim: \\"1' sholl III have of stock (sce fig. 9). :It least :J< ) per cent l'f till: depth of thc rmleler below this liJll' (X to he :lO 1wr cenlY, Fig. 5). Folluwing the lille of the hull and k ee pil1!-: the root chord at miniJJlum pI'rmissi bJc distancc frulll it, it follows ther ef or e, that we shall r equire a m ean lle plh of 5 ft. 9 in. to satisfy this requirelllent. Thus we have :I mean churd of; 17·2 ' =2·98 ft. 5·75 .. Tlle as pect ra tio will therefore be:-
,
~.
same
, - - .·- ·: : : i'u ·
Fr om Tahle I per cenl L X tl for tug (lwill screw), say :1·5 pcr I:cnt. 3·5 per n'nt of L X d "" 3·1'" sq . n. (comuincd f1Hld er ar ca).
'5 ':J
=
screw,
• 5~.:W '
-.---
tUlhlrr
Nc\y hc:u!lluarttrs
for D.S.I.IL
. Th~ !Jc;\clfluar!l'l's clf the Du p:tr tJllel1t of Scientific anti Ind ustr ial HeSt'all:h ha~ llIovecl to Stato II(Jwlt~, IIigh 110(· burn, Lond oll, W.C.I (tclcl'hollu: Clpllct'ry 17.02). Stall; i.1oll~c i~· a new I!j'!Itor ey hlocle abo'l1t thr ru ' JIIinlllt-~;" wallr flolll 1101 · horn lInclngr\lund slation Oil the nor th
sido
(\f
Ilinh 1 1 0 1 '0 0 1 1 1 .
