Note: Descriptions are shown in the official language in which they were submitted.
13~53~;9
vescrip~iol~
VESSEL ~ITI~ PROVED llYDRODYNA~IIC PEI~FOal~NCE
Technical ~ield
This invenlion relates ~o navigable vessels and one of its principal objec~s is to
pruvide a vessel wi~h Improv~d p~crformance, par~icularly a vessel thal creates
10 less turbulence, has less l`ric-lonal resislance, and performs he~ler in disturbed
wa~er and heavy seas, while main~ainin~ stability and operaling capabllity The
result of such improvemen~s is Increased fuel economy and/or speed smoother
opera~lon, less s~ruclural demands on Lhe vessel and improved operation ln
d~s~urbed wa~er
15 A vessel movin~ lhrou~h waler experiences frictional resistance al the wettedsurrace below lhe wa~er llne As ~he speed of lhe vessel increases ~he turbulencecrealed by ~he hull movin6 Ihrough the water increases rapidly usllil friclionall`orces bocome the practical barrier lo hi~her speed The energy requir~d to
propel the vessel increases correspondin~ly lmprovin~ speed and efficiency
20 are reco~nized as tbe primary ~oals and activities in ~he naval arls and
decreasin~ frlclional reslslance is seen as ~he key to these goals An addilionalgoal ha~ been lo impr(ve lh~ abilily ~o operate ln dislurbed wa~er, including
heavy seas, where pitchin~ and slammin~, spray, yaw and roll severely limil
navi~abllity .
75 Anolher impor~ant fac~or in addilion ~o speed tha~ influences the efficienc~- of
~h~ vessel is i~s ability ~o rnain~ain trim Trim is the attitude at which ~he vessel is
desi6ned ~o lie when al resl For displacement vessels this will usually be lhe
same altitude that lhe vessel assumes at speed ~l is importanl both ror
convenience and prac~icali~y ~ha~ ~he decks, working, areas, equipment, elc be
3Cl at lhe same relalionship lo lhe horizontal (ie be horizontal~ bolh when the
vessel is at rest and when underway
However planmg vessels normally are designed ~o ~and musl) opera~e al a
posl~ive ~rim an~le usually ~wo lo len degrees so lha~ lhe stern remains In the
water enough lo main~ain ~he s~abilily of ~he vessel, nol only a~ains~ roll and
~5 yaw bul also a~ains~ yilchin~ l`orces ~ha~ could la~e ~he bow under, and ~o l;eep
the propelling mechanisms submerged (Loss ol` lrim is usually measured as an
angular devia~ion Or the vessels horizon~al cen~er of Rravily line from ~rue
horizonlal, zero degrees being perfecl lrlm ) Such devlation l`rom lrlm imposes a
$
~3~53~9
subsl3ntial penal~y of increased fric~ion and drag due to sinkin~ of ~he s~ern
increased pi~chinR slamming and yaw wind action a~alns~ and air en~rainment
under ~he upraised how and a subs~an~ial spray root a~ ~he bow en~rance as well
as a decrease jn ~he el`ficiency of ~he propelling sys~em in mos~ cases Thus
S main~ainin~ trim is an addilional objec~ive in the arl ~o further ~he primary goal
of improvin~ speed and efficiency
Bac~ground Arl
Numerouj vessel desl~ns have been proposed for reducing resis~ance Planing
I l) hulls are widely used in modera~e size and smaller vessels The planin~ surfaces
on ~he hull cause the vessel Ul rise in the water as speed increases ~hus
decreasin~ ~he wet~ed surJ`ace area and thereby decreasin~ the frictiorial
resis~ance and drag This decrease can be substantial Never~heless a subs~an~ial
amoun~ of lhe wet~ed surl'ace remains ~oge~her wi~h its associated fric~ional
1~ resis~ance and drag and ~he ~rim limila~ions impose ~he subs~an~ial penal~ies on
efficiency men~ioned above Aside from the efficiency problems associa~ed ~vith
~rim as speed incrèases water flow past even the mos~ s~reamlined planing
surfaces becomes ~urhulen~ This ~urbulence has been yel ano~her barrier lo
increased speed and ef'f'iciency l'or which a solu~ion has lon~ been sought
20 Hydrofoils like airf'oils (e ~ win~s) in lhe aeronau~ical arts are streamlilled
bodies which crea~e a useful reac~ion ("lif~ing force") from a fluid s~ream
rnovin~ rela~ive to ~hem In prac~ice hydrofoils are ~iven a different curva~ure
(camber) a~ ~he opposed surl`aces The resul~in~ unbalanced profile is designed ~o
crea~e an efficient lif~ing force in ~he wa~er a~ ~he selec~ed angle ~f a~ack of ~he
25 hydrofoil i e the angle be~ween the chord (straigh~ Iine connectin~ ~he lea(ling
and ~railin6 ed~e) ol' Ihe hydrofoiJ and ~he direction ol` movement of the vessel
The hydrofoils ar~3 secured to lhe hull of lhe vessel and usually extend
~ransversely amidships a~ and/or below ~he bot~om of ~he hull
Hydrofoils are capable of liftin6 the vessel almos~ comple~ely from the wa~er
30 ~hus reducing friclion and draB to ~hat impar~ed by ~he remainin~ rela~ively
mlnor amount of we~ed surface (principally por~ions of the propulsion sys~em
and the rela~ively hydrodynamically efficien~ rudder and hydrofoils) However
~he formidable s~ruc~ural and o~her design problems involved in lifting an
enlire vessel on~o hydrofoils and conlinuin~ lo propel it limi~s lheir use lO
35 smaller vessels These vessels have addi~ional serious shor~comin~s They have
poor s~ability and are difficul~ ~o handle They haYe limi~ed service speed
Hydrofoils are highly vulnerable ~o floa~in~ debris Moreover hydrofoils as
desi~n~d and posiliolled can only impar~ a lif~ing ac~ion and ~hey serve nn
3 13C~5;~9
appreciable func~ion of heaYe or trim control, of coun~erin~ yaw or pitch or of
decreasing ~he friction or turbulence of the water on ~he vessel hull when a
por~ion of the hull is under wa~er at slower speeds Indeed, the foils li~ely add to
turbulence and drag when lhe hull is in ~he water
Hull design el`forls have been directed at lhe use of dynamic forces crea~ed as a
planlng vessel moves through ~he water to reduce settlin~ or sinking of the
s~ern due to upward inclina~ion of ~he bow during planing In particular, foils
have been sugges~ed for impar~ing a lif~ing force on a vessel to affec~ its ~rim In
U S Pa~en~ No 4,569,3()2 a lif~in6 foil is a~tached to the st~rn skegs of a bar~e,
and in this posi~ion would ~end ~o lif~ ~he stern This could compensa~e for ~he
uplif~ of ~he bow of the bar8e by a ~ow line and ~hus help ~o main~ain trim
Hvdrodvnamics of Ship Desi~, a ~hree volume treatise by Harold E Sauders,
published by The Socie~y of Naval Archi~ects and Marine Engineers, 74 Trinity
Place, New York 6, N Y, 1957(referenced hereafter in this background as
J 5 "Hvdrodvnamics" ) reports, at Vol, 1 pages 428-431 and 563-4 on e~pedients for
~rimming a vessel by lif~ing ~he slern, These include angled propellers that lif~
the s~ern, liftiDg planes in lhs propeller wash, downward spray deflec~ors a~ ~he
s~ern which impar~ an upward force by deflec~ing spray from ~he propellers,
wide s~ern wa~erplanes and stabilizers or submerged s~ern hydrofoils ~hal
2CI similarly impar~ upward force ~o brin6 a planing craf~ in~o a more nearlyhorizontal running aUi~ude Ano~her proposal, in U S Pa~en~ 3,138,130, is to
channel ~he bow wake ~hrough a cen~ral cavi~y ~hroa~ ~o ~he slern of ~he vessel,lhereby generating upward force However, ~o ~he ex~en~ any of ~hese expedien~s
succeed in impar~ing upward force(lift) ~hal raises the s~ern to improve trim,
they create lhe offsetting problem of reduced stability and control,
Diving planes or foils are utilized bolh at the bow and the s~ern of submarines,By adjusling the angl0 of attack ~hese planeswill create an upward or downward
force a~ ~he bow and s~ern, as ~he submarine moves in water, to change lhe
attitude of lhe vessel from ~he horizontal to dive or rise lo lhe surface(see
Hvdrodvnamics Vol, 1, p, 569) However, these foils are mainlained in a neutral
or no lift posilion for surface travel,
Downward and laleral forces have been imposed on sailing vessels, by means of
foils under ~he hull, for lhe purpose of counlering yawing and heeling forces on~he vessel, as described in U S Pa~ents 4,193,366 and 4,0~8,076 Al~hough this was
no~ recognized, ~he downward force may also have some affect in maintaining
longi~udinal ~rim of ~he vessel, in the sense of dampening pitching forces
created by the water and the wind, However, the amoun~ of downward force ~hat
13¢;~5;~Ei9
can be imposed and amount of benefi~ derived would be quite limi~ed A
downward force oJ` a subs~antial magni~ude on a displacemen~ vessel would beave
il substan~ially helow design ~rim aDd ~hus bo~h de~rac~ from design efficiency
andcreate the danger of faundering Addilionally unlike a planing vess~l the
5 hull of a displacement vessel normally retains i~s ~rim and stability at speed so
the addi~ional force impar~d would be of limited benefi~ particularly as
comDared with the a~lditional fric~ion and drae created
Hidhel~ ~peed displacem~nt v~ ls such ~ d~Lr~yer~ crui~rs b~t~ hip~ ~nd
o~h~r military craf~ ~r~ pro~ided with sharp or "fine" and deep drafl b~w
10 sections usually with concave ~o straight bu~ocks at the en~rance and a full
forefoot( junction of the stem and the keel) The profiles of ~hese and similar bow
sections are illus~rated in Hydrodynamics at Sec~ion 2610(pp 394-5 of Vol 1~
Such low volume and ~hus low buoyancy en~rances are highly efficient but ~heir
surface configura~ion ~ends ~o genera~e suc~ion at ~he buttocks and bouom thus
15 imparting subs~anlial nega~ive lif~ to the bow Due ~o the limi~ed buoyancy and
lack of surface to genera~e compensaling upward force this en~rance design can
imparl a d~gr~e of inxlability ~hat can endan~er a vessel However with
displacement vessels of ~his design fore-~o-af~ stability agains~ pitch and yaw is
no~ a major problem bo~h because of ~heir normally lower speed compared to ~o a
20 planing vessel and because of the stabili~y provided by their much greater
we~led surface suppor~ed by buoyancy lhroughou~ their length However for the
s~ability problems indica~ed h is cus~omary ~o drastically cut away ~he forefoo~ of
a planing vessel so ~ha~ Ihe bow wave comes under the hull to lessen yaw and
pi~ch tha~ can cause the bow lo di8 in and capsize the vessel(see Section 30 4 of
25 Hvdrodvnanlics p ~26 of Vol 1)
As indicated at Sections 7715 and 7716(pp ~35-7 of Vol 2) of 8Yg~gm~
bows having a hieh rise of floor forward(ie a narrow~r or finer bow) and
concave to s~raight but~ocks at ~he en~rance have been suggested for planing
vessels However ~he limi~a~ions of ~his design for navigation in dislurbed water30 in regard ~o pi~ch and yaw are acknowledged Moreover ~he suggested bow
designs are ac~ually rela~ively broad a~ ~he en~rance and rela~ively shallow (i e
shor~ in ~he vertical direc~ion below ~he waterline) This is consisten~ wi~h thewidely held view ~hat a planing vessel must carefully avoid generation of forces~hatwould cause the vessel to ~rim ~o ~he s~ern (assume a ne~n~ive trim angle~
35 and thus create ~he danger of the bow digging into disturbed water and possibly
capsizing For ~his reason planing vessels are conven~ionally provided with
~53~i9
subs~an~ial volume and la~eral surface al the bow for buoyancy and upward
planing force
Pitching, yawing, slamming and spray resulting from sea action has been a
fur~her hinderance ~o vessel performance, creating severe fric~ion and
5 turbulence and hinderin8 con~rol of the vesssl Various means to coun~eract this
affec~ of sea aclion have been proposed Modifications of ~he bow sec~ion of a
vessel below i~s wa~erline have been sugges~ed ~o decrease wave pounding on the
hull bo~tom due to pilchin~ of the vessel in heavy seas, such as the torpedo-like
budy below ~he keel line disclosed in US Pa~en~ 3,8~5,514 However, such
10 modifications as ~hese resul~ in considerably increased fric~ion and dra~ on ~he
vessel and their desi~n is inefficien~ for effectively dampening pitch of the
vessel
Skegs, which are proj0ctions or appenda~es on the underwater hull, have long
been employed at the afterbody of vessels for various purposes including
15 dampening of s~win~s ~o thus impar~ s~ability of route, Hydrodvnamics a~ Sec~ion
2515(pp, 379) also suggests that a skeg may be applied ~o or worked in~o the
entrance---, al~hough the type of ~essel and particular purpose in mind i9 not
revealed So far as is known the employment of skegs at the forebody of a
planing vessel, and in parlicular a planing vessel designed to operate close to or
20 at ~rim, has nol previously been addressed
Steps on the planing surfaces of a planing vessel have long been known in ~he
art A s~ep is a vertical discontinuity, usually sharp, across the bottom of the
vessel Typically they are straigh~ or V-shaped in plan form However, owing to
the grea~er complexities arising from incorporating s~eps inta vessel design and~5 uncer~aintiw as lo ~he effecl lhey will have in a particular desi&n, practically all
vessels olher ~han racing craf~, now have s~epless hulls
Disclosure of Iho Ill~enlion
This invenlion relates to improving the performance capability of planing
30 vessels, both as to el`riciency and speed and as to their stability and operating
abili~y, par~icularly in disturbed water, and methods of operating vessels to
achieve improved performance In accordance with this invention planing
vessel performance may be substantially improved by imposing on the vessel
during its movemen~ a dynamic downward force which is generally aligned with
35 the longitudinal verticaJ centerline plane, a~ a location or locations along the
lenglh of ~he vessel Dynamic force is intended to mean force generated as the
vessel moves through ~he wa~er as con~rasîed to sta~ic force, such as the
~L3~3~9
gravilational furces caused hy Ihe weighl of the vessel cargo ballast, etc, which
severely impede efficiency during naviga~ion and which can create difficulties
in establishing and maintaining a sa~isfac~ory ~rim to ~he vessel both at rest and
during navigation
A fur~her important aspec~ of this inven~ion is that the dynamic downward force
is posi~ioned ~o coun~er ~he tendency of ~he planing surfaces to increase ~he ~rim
angle and to heave ~he vessel into an unstable condition as speed increases and to
coun~er l`orces crealing yaw and pi~ch, thus generally improving the trim of ~hevessel during operation By appropriale placement of Ihe dynamic force, trim
may be maintained during operation of tbe vessel which approaches or equals
that of the vessel a~ rest particularly in the case of vessels specifically designed
for the application of such force
More specifically, ~he loca~ion and magni~ude of ~he dynamic downward force
and/or lhe olher upward and downward forces ac~ing fore-and-aft on the vessel,
bo~h static and dynamic are adjusled relative ~o each other to bring the locus of
all such upward forces and the locus Or all such downward forces closer to each
o~her and, ideally, ~ have such loci coincide al any given speed, parlicularly as
speed increases from displacemen~ mode ~o planing mode al around len to ~wen~y
knots In practice, this may include no~ only posilioning of lhe poin~ or points of
application of th~ dynamic downward force bu~ also vessel desi6n to provide and
position weight buoyancy planing and other lifting surfaces, propeller
downward pull or suction a~ ~he but~ocks and bo~tom, e~c which will coopera~e
most effectively wi~h ~he dynamic downward force ~o maintain trim through the
en~ire speed range of ~he vessel Desirably the downward force applied is
generally 1 to 5~% or more and preferably 5 ~o 25% of the displacement weight ofthe vessel,
Anolher aspecl of lhis invenlion relates ~o configuralion of the wetled surface in
specific ways lbat cooperate in a unique fashion wilh ~he dynamic downward
force of ~his inven~ion and which, additionally may be beneficially used
independen~ly, These include a deep draft, fine bow a bow skeg, a bow win~, a
fore-and-af~ planing surface and keel configura~ion, an aft flow separation zoneand an afl chine seperation fins and double stern arrangemen~
The bow of ~his inven~ion for a planing vessel is bolh deep and fine, as compared
~o conventional planing vessel bows, and is generally fla~ to concave at ~he
3S entrance ~esirably for vessels wiih a V-bo~lom planing surface, the bow
entrance at points 10% and 20% Or ~he distance from ~he fore perpendicular to
lhe aft perpendicular have a ratio of the design chine beam to keel line draft no
7 ~3~S3~9
greater lhan 3 and 4, respec~ively Similarly ~he mean draft oYer lhe distance
from ~he fore perpendicular ~o points ~0% ard 20% of ~he dis~ance ~o ~he aft
perpendicular is desirably a~ leas~ S0% of the deepest drafl af~ of lhe en~ranceand may be equal lo or greater lhan ~he aflward drafl
5 Unlike cnnven~ional planing vessel bows, lhe en~rance of lhis invention
genera~es only limi~ed lif~ing force due i s shape Ins~ead tha~ shape will
generale predomina~ing suclion forces as vessel speed increases which will bias
~he bow downward, ~hus prevenling lhe bow from "planing up" ~o a posilive trim
an~le as do conven~ional planing vessel bows This downward force wilJ
10 coopera~e wi~h a dynamic downward force applied af~wardly of the pressure
poin~ of ~he vessel planing surfaces to facilitate the dynamic trim of this
invenlion The downward forces a~ ~he en~rance and af~ will toge~her "balance"
~he vessel ~o trim about the "fulcrum" of upward planing force acting
~herebe~weenThe aftwardly dynamic force, addi~ionally, has a biasing effect
15 againsl downward pilching at lhe bow, aBain acting through the "fulcrum" of
~he upward planing force ac~ing in be~ween, ~hus iJnpar~ing s~abili~y for a bow
thal could otherwise be dangerous in dislurbed wa~ers when operatin~ at zerG
~rim,
Another feature of ~he islvention comprises a vessel equipped with a forward
2n skeg and a forward wing for purposes which will be described Bolh lhe skeg and
~he wing are loca~ell forward of midships, preferably ex~ending aft from ~he bow,
cen~ered on the longitudinal cen~erline of ~he vessel The skeg is a~tached ~o and
extends downwardly from ~he boltom of lhe vessel alon~ the hull line As
compared to cor,v~n~ional afLward ske~s the bow skeg's positionin6 will be more
~5 effec~ive in main~aining lhe vessel in ils palh Or ~ravel(direc~ional stabilily) a~ld
in decreasin~ yaw in heavy seas Ulilized in this invenlion in which ~he ,vessel
may operate at zero trim, lhe forward ske~ carries Oll~ the imporlant func~ion Or
spli~ing ~h~ ol~coming flow which be~ler dis~ribu~es and par~ially relieves ~he
pressure of lhe flow on lhe aftward wet ed surface, thus helping IO rel~in
30 laminari~y of ~he flow and ~hereby reducing lurbulence and fric~ion This is aunique func~ion which would have little or no affect with prior ar~ planing
vessels which plane up a~ ~he bow lo essen~ially"ride" on ~op of lhe water
Adva~ageously, ~he forward win,g may be a~ached ~o ~he underside margin oî
~he forward skea and suppor~ed ~hereby The forward wing in general aspect is
35 designed to have a s~reamlined and low resis~ance profile in ~he vessel direc~ion
and a relatively hi8h fric~ion and dra8 profile in the heave(vertical) direc~ionIl is lhereby capable of providing a lifling force and dampening pitch
8 13~5~69
dynamically with minimum added fric~ion and drag, particularly as compared ~o
s~a~ic dampeners such as ballas~ ~anks Advan~ageously, a swep~ back or "delsa"
win~ is employed ex~ending al ~he entrance af~ward from i~s leadin~ vertex five
~o 30% of the wa~erline leng~h of ~he vessel along ~he skeg This wing desirably
5 has an angle belween ~he leadin~ surfaces lo ei~her side of I lo 15 degrees,
Advantageously when appropriately designed and posi~ioned relative lo the
waler l`low, ~he win~ may also be u~il~zed ~o provide a dynamic lif~ing or
depressive force on ~he vessel foreward of midships for purposes of adjusting
heave or ~rim of ~he vessel, ei~her independen~ly of or in coopera~ion wi~h ~he
10 o~her fea~ures of ~his inven~ion involving ~rim and heave con~rol
Ano~her fea~ure of ~he inven~ion is ~he design of ~he planing floor af~ midshipsto enhance stabili~y of ~he vessel for opera~ion a~zero ~rim Conven~ionl planingvessels which are "trimmed a~ ~he slern" i e opera~ed at a substantial trim angle,
are designed to have a draft af~ midships of a similar magni~ude as ~hat at
15 midships, and frequen~ly even a ~rea~er draf~ Con~rary ~o this prac~ice, in ~his
inven~ion ~he rloor rises from midships ~o ~he s~ern a~ leas~ 25% of midships draf~
and may rise as much as 5d~ ~o lOOYo or ~reater of midships drafl
Ye~ ano~her fea~ure of ~he inven~ion is a design for a vessel trimmed in
accordance wi~h ~his inven~ion which will minimize ~he dra8 normally
20 experienced at the s~ern of planing vessels A pressure release zone or floor is
provided on ~he hull we~ted surface at the s~ern extending ~o the transom
configured and posi~ioned ~o gradually reduce the pressure on the flow along thehull planing surface withou~ itself at ~he same ~ime crea~ing undue additional
~urbulence and friction The pressure release floor cons~ilutes a planar or
25 concave, upwardly ex~ending ~erminal porlion of lhe pliming surface 011 ~he
hull bot~om which intersects aftwardly with the stern ~o form a ~ransverse
trailiQg edge The pressure release floor, fore-to-aft, desirably extends between5~ and 25% of the waterline length of ~he vessel and rises be~ween 10% to 50% ofmidships draft of the vessel A lransverse s~ep may be positioQed af~midships
30 near and advanta~eously may form the leading portion or edge of the release
zone to enhance i~s effect The trailiQ~ edBe of ~he pressure release floor is
strai~ht, extends across ~he stern parallel with ~he base line plane and
perpendicular lo ~he vertical longi~udinal cen~erline plane of ~he vessel, is
elevated from the step and is posi~ioned approximately at ~he design waterline of
35 ~he vessel, desirably a distance of less than 15% of midships draft above or below
the design wa~erline
~3C~S~69
(~
Another as~ect of the invention is th~ provision oî a double s~ern construction
havin6 a rearward and upward fin extension of the chine at each side of the
vessel which efl`ec~s a smoo~h and gradual flow separation al ~heir aft
~rmina~ion thus avoiding drag tha~ otherwise occurs
5 By utilizing ~he princip~l of ~his invention vessels may possess larger planing
surface and have a broader beam and a lar~er stern section wi~hou~ problems of
s~ability~par~icularly as ~o pitch and roll) and control or an unacceptable
incre~ce in fric~ion and dra6 thereby permitting lar~er payloasls and improved
performance Thus ano~her a~pecl of ~his invenlion are vessels having a
10 planing surface configuration which would be unstable for conventional
planing vessels and vessels havin~ a planing surface confi~ura~ion which is
unique wi~h respec- ~o amounl of such surface and/or its dis~ribulion on the
vessel's hull
An impor~an~ aspec~ of ~his inven~ion is ~he èmploymen~ of foils under or beside15 the hull a~ a position or posi~ions alon~ the hull to create the appropriate
dynamic downward force The foils are disposed with ~heir leading edges in ~he
Yessel travel direc~ion and are orien~ed ~o present an angle of a~tack ~o the water
flow ~o generate ~he desired downward force at the vessel speed Conventional
foils either with a symmelrical profilè or dominant camber on the lift direclion20 side! may be employed Howe~rer special foils particularly adapted for ~his use
are provided ~o optimize the benefits the inven~ion and comprises ano~her
feature thereof
The conven~ional foils referred to above have a characteristic little considerednor of any moment in ~heir conventional use namely they divert flow as i~
25 passes the trailin~ edge in the direction opposile lhal of ~he liftin~ force
imparted Howèver as they arè used in lhe present invenlion "upside down" lo
create a downward force i e ne~a~ive lift such conven~ional foils will diver~
flow upwardly
This can create turbulence alongside the vessel hull and at the stern thus
30 limiting to some degree the benefits otherwise available from lhe use of thisinvention This drawback is avoided by use of a foil which is cambered in the
leading section to exert a force downwardly but which is also specially
configured in the trailing section so as to divert flow at the trailing ed6e in the
same direction as lha~ of the force impar~ed by Ihe foil A foil havin~ an uppsr
35 surface at the trailing pos tion lhat is convexely curved downward to the lrailing
edge The downward l`low which results from ~his design also will have the effec~
I () 13~5~g
of neulraJizing ~o some exlen~ the pressure on the flow al the trailing edge,
I`ur~ller reducill~ dra~
Novel foils havin~ Inw induced drag, particularly a~ hi~her speeds, are also
provided which have a lower surface from ~he midsec~ion of she foil to lhe
5 railing ed8e which is curved upwardly a substan~ial distance loward the chordol` ~he l`oil For very hi~h speed applica~ions ~he foil is providin~ a relatiYely fla~
upper surface ex~ending from lhe lhe region of Ihe leadin~ ed~e towards the
midpoint 11` the l`oil To provide a force thal is non-linear wilb speed, a s~ep may
he provided in either ~he upper or lower surface exlendin~ in the span direction,
10 on lhe upper surface ~o decrease ~he rise in force a~ higher speeds and on lhe
lower surface lo increase ~he rise ol' force
It will be seen that when implemented lo the fulles~, this invention appears to
convert a planin~ vessel par~ially inlo a displacement vessel, in the sense that in
planing ~he d~crease in wetted surface is significantly less than, and
15 proportionally perhaps only a small fraction of lhe decrease in wetted surface in
a convenlional planin~ vessel This appears an anomaly and contrary ~o the very
purpose of planing surfaces, i e ~o decrease we~led surface lo the e~tenl
prac~icable However i~ has been discovered ~hat in praclice of this inven~ion,
lhe efficiency of ~he vessel is improved over convenlional planing vessels and
20 this improvement is even significanlly grealer lhan mighl be expected by the
increased performance due ~o maintenance of at resl lrim and consequenl lower
fric~ion and draR at ~he s~ern and along ~he planinR surfaces Wi~hout intending
to be bound by any parlicular lheory as lo lhese results, it is poslulated that al
zero lrim angle the narrow, deep bow surfaces coact wilh the gradually flaring
25 planing surl'aces exlending aflwardly lo smoolhly guide the flow principally in a
fore-to-afl flow line in a manner lhat minimizes lurbulence and, in particular,
avoids enlrapmenl or enlrainment of air bubbles under the hull and greatly
supress and, perhaps, complelely eliminates lhe spray root or roots lhat normally
occur in conventional planing vesseJs Al the a~t section the gradual and
30 uniform release of pressure due lo ~he arrangement of planing surfaces
described addi~ionally minimize lhe fric~ion and drag usually experienced al thestern
Brief De~eriplion of Ihe Dra~in~
35 FIG I is a plan view in outline form of a vessel with a superimposed force
diagram to demonstrate ~he action of forces longiludinally on a vessel, as lhey
relale- lo the present invention
" 3L 3 C~ 5 ;~i 9
FlG.2 is an isome~ric view nf a vessel embodying the presenl invention taken
from the s~arboard side
FIG.3is an elevational view of the vessel of FIG. 2 taken from the starboard side
FIG.4 is a bo~tom view of ~he vessel of FIG 2
FIG,5 is a cross-sectional view at the aft section of the vessel of FIG. 3 takenaftwardly along lines 5--5
FIG 6 is a cross-sec~ional view a~ the aft seclion of ~he vessel of FIG. 3 takenaf~wardly alonæ lines 6--6
FJG.7 is a cross-sec~ional view al the fore seclion of ~he vessel of FIG. 3 taken
10 af~wardly along lines 7--7.
FIG.8 is a cross-sec~ional view aL the fore sec~ion of the vessel of FIG. 3 taken
forowardly along lines 8--8, And, in dotted line, a cross-sec~ional view of Ihe fore
section forewardly of lines 8--8 a~ station 1/2(half way between slations 1 and 2
marked along Ihe len~th of ~he vessel in FIG.3).
FlG.9is an isome~ric view of the how forward of sec~ion lines 8--8 of FIGURES 1-3
~ken from below and showing ~he skeg and forward wing mounted alon~ the
bo~tom thereof
FIG.I0 is an enlarged fragmentary view of the lower porlion of cross-sec~ional
view of FIG.8
FIG.llis ~he isome~ric view of FIG. 9 bu~ showing an al~ernale form of a forwardWiDg on the bow
FIG.12 is a fragmen~ar,v view of the bow of FIG. 2 but showing an alternative
form of the forward win~ mounted thereon
FIG. 13 is an enlarged cross-sec~ional view taken along lines 13--13 of FIGII
25 showing the cross-seclion of Ihe forward wing
FIG,14is a s~ern view of the vessel of FIGURES 2-4.
FIG,15is a fragml,n~ary cross-sectional view taken outwardly along lines 15--15
of the stern of FIG, 14 showing a foil and its connection with the vessel,
FIG. 16 is an enlarged cross-sec~ional view taken along lines 16-16 of FIG.15
30 showing ~he foil in cross-section
FIG,17 is an enlarged cross-sectional view showing, in cross-section, an
alternative foil configuralion forming a parl of this invention,
FIG, 18 is a plan view in outline form of a vessel showing the planing surface
configuration ~hereof and the rela~ed positioning of downward force generating
35 means,
1 2 ~3~5369
is a plan view in ou~line form of a vessel showing another planing
surface configura~ion and ~he rela~ed positioning of downward force ~enerating
means,
FIG 20 is a plan view in outline form of a vessel showing another planing
5 surface configuration and the related positionin~ of downward force genera~ing means
FIG 21 is an outline view taken from the stern of a vessel showing an
alternative foil configura,~ion and mounling arrangement
FIG 22 is an enlarged isometric view, from below, of ~he s~ern of ~he vessel of
10 ~IGS 2-4~with lhe foil and s~ru~s not shown) bu~ showing an allernative floor,
step and chine fin configuration on lhe trailing porlion of lhe vessel floor
BesL ~aode of Carrying Oul The Invenlion
Planing vessels contempla~ed in the practice of this invention are vessels for
l 5 which at design speed dynamic lift is appreciable, equaling at least five percent
of the weigh~ of Ihe vessel and,when operated conventionally, which have ~heir
cen~er of gravity at leas~ as hi~h as i~ is with the vessel at rest This includes so-
called semi-planing vessels which generate a a lif~ing force smaller in relationto displacement wei~h~, on the order of ~en or, perhaps more typically twenty or2U forty percent of ~he displacemen~ weight, and full planing vessels for which
dynamic lif~ at speed may equal one half to ~wo thirds of the weight or as hi8h as
nine~y percen~, Opera~ed conven~ionally, a full planin~ vessel a~ design speed
will have a center of gravity higher than at rest and a wetted surface which is
may only one ~hird of the at rest value, or even less, It should be understood tha~
25 benefits of this inven~ion may be realized for semi-planing vessels which maybe as greal as for vessels wi~h greater planing force potential rela~ive to vessel
weighl.
A clearer understanding of this inven~ion may be ob~ained by first illustra~ing
~he forces normally acting upon a planing vessel during movement and then
30 describing ~he in~erac~ion of the forces applied in accordance with ~his
invenlion, FIG l shows the nature and directionality of the various forces acting
upon a planing vessel la These include the weight W of ~he vessel and its
conten~s acting through the center of gravi~y, and lhe upward buoyancy force
B of the water on ~he wetted surface of the vessel, ac~ing collectively through
35 the center of huoyancy The centers of gravity and buoyancy normally coincide
when the vessel is at res~
1 3 ~30S3~9
When the vessel i~ al speed, pJaning force P F will act upwardly along the
planlnR surt`aces 2a and collectively ~his force will ac~ through a locus calledthe prèssure poin~ Also in the case of conven~ional planing vessels in the
planing mode the vessel will rise in ~he water ~heave up) un~il the planing
5 force is coun~erbalanced by ~hè loss of buoyancy force due to the loss in wetted
surface ~or lowering of ~he wa~erline) due to ~he rise Typically a conven~ional
planing vessel will rise un~il the we~Led surface decreases to one ~hird or less of
~he a~ res~ we~ted surface (when all of ~he vessel's wei~ht is borne by the
buoyancy of the vessel ) Hence buoyancy force is decreased in ~he planing mode
J () with the subsli~ution of planin~ force The locus of ~hese planing forces, as well
as lheir magnilude can be adjusled fore-and-af~ by dis~ribu~in~ more or less
surl`ace fore or af~ by changing ~he inclination or angle of attack of such
surfaces longiludinally andior in the case of V-bottom vessels, by changin,g
~heir ~ransverse inclina~ion ~ called "raising or lowering the floor" )
15 To a varying exlent depending upon ~he vessel's design, o~her forces will acl fore
and af~ ~o influence bolh ~rim and heave, An impor~ant force is the do~rnward
forc0 of suc~ion caused by negative differential pressure (negative lift) 1) P
8enerated along Ihe bo~om and sides of the vessel below the waterline tbu~tocl~s)
by flow alon~ ~hese surfaces Generally ~he more wet~ed surface, par~icularly in
20 the ver~ical direclioll ~he more nega~ive lift from downward suc~ion a~ the
bouom and bul~ocks Too much ne~ative lift from foreward surfaces may cause
~he vessel ~o incline ~oward the bow, i e assume a nega~ive ~rim angle A vessel
in this condi~ion, called "trimmed at the bow" is susceptible to submergence a~
the bow and capsizing
25 The trim of lhe vessel in ~he planing mode will vary in accordanco with the
relative distribution fore-lo-aft, of ~he various forces, par~icularly ~he dynamic
forces which may vary wi~h the speed of the vessel For example, by changing
the confi~uraLion of the planing forces to create rela~ively more planing force
a~ the foreward section (forebody) of the vessel in ~he planing mode the
30 increased forward force will raise or heave the bow rela~ive ~o ~he s~ern and thus
increase the trim angle of the vessel Increasing the fineness and vertical wetted
surface a~ ~he bow (deepness~ will increase the suction f'orces alon~ these
~urfaces and the nega~ive lift crea~0d ~hereby and ~hus lower the bow relative to
the s~ern
35 In accordance with this inven~ion additional forces fore-to-aft are superimposed
on the vessel for affecting trim and for other purposes to be discussed These
include the dynamic downward force N L (nega~ive lift) supplied by a foil 3~
1 4 13C~5~
shown a~ ~he slern of ~he ~essel in FIG I and the upward force L (lifll of the
forward wing 3~a illustrated a~ Ihe bow of ~hat vessel These forces may be
adjusted fore-to-al`l in accordance wi~h this invenlion as will be described
In designing planin~ vessels the essential coDsidera~ions of directional stability,
5 fore-and-afl stability and abilily to cope with lhe roll, pitch, yaw and surgeforces in disturbed wa~er musl be taken in~o accoun~ As a consequence, the
vessel forces are conventionally arranged so that al planing the vessel will "trim
al ~he s~rn" ~ypically be~ween two and six de~rees to maintain stability in
disturbed water a~ainst di~ginB in of the bow and directional and lransverse
10 slability As previously explained ~he resul~ is a large penal~y of friction and
dra~
By contrast in the practice of this invention the trim angle may be maintained
less than two degrees, and, advanta~eously, zero de~rees or even at a minor
negative angle such as up to minus five degrees, if desired for example ~o reduce
15 pitching in heavy seas, while s~ill maintainin8 vessel s~abili~y Con~rary to
convenlional praclice which is ~o eleva~e the vessel to the maximum by upward
forces, in Ihis invenlion downward force is applied lo the vessel bo~h lo bring i~
closer to trim and to improve i~s s~abili~y Appropria~ely designed, ~he vessel will
be capable of operatin ~ in disturbed wa~er with stability agains~ bow
20 submergence and direc~ional and transverse slabili~y More conventional
planing vessels may also benefi~ from use of ~his invention allhough in some
cases to a lesser de~ree
As il applies lo all planin~ vessels, of special design or not, the dynamic
downward force is applied slrategically fore-to-aft along the lorlgi~udinal
25 vertical centerline plane in relation to the o~her forces acting on Ihe vess~l, and
par~icularly the planing forces, so as lo bring Ihe vessel closer lo zero lrim,
FIGURES 18 and 19 illustra~e ~his principle, focusing only upon the upward
planing forces of the vessel In FIG,I~ the planing surfaces 2b al the forebody of
vessel Ib, as shown in trim, have a pronounced convexily ~hus presenting to the
30 oncoming flow a subslan~ial rise a~ the bow which will generate strong planing
forces forward and only lesser forces af~ward of the convexi~y, Thus, th~ locus of
planing forces will be foreward such as a~ F-1, To balance ~hese forces to
maintain ~rim, a dynamic downward force, preferably genera~ed by a foil 3b, is
posilioned more forward, as shown, at or slighlly forward of midships In
35 contrast, the planin~ surface 2c of vessel lc in FIG 1~ has a much less
pronounced convexity and a smaller rise at the bow so the locus of planing
1 5 13~53~;9
forces will be more af~ such as al F-2 Accordingly ~he downward force,
genera~ed by loil 3c, is posi~ioned more aît, i e somewhat aft of midships
A more complex balance is illustra~ed in FIG 20, a~ain focusin~ only on the
planing forces Vessel kl has a forward planin~ surface 2d resembling that of
5 FIG l~, which will generale a planing force having a locus or pressure point
more for~ward, as well as a step cooperating with a stern pressure release zone
(fully explained at a la~er point~ which will also ~end to concentrate planing
force forwardly of ~l~p 4d To balanc~ ~h~ upward planing forces in order to
maintain lrim al planing ~he downward dynamic forces may be divided into ~wo
10 componen~s a forward component Benerated by foil ~d-1 fore midships and a af~componen~ genera~ed by a foil 3d-2 located a~ ~he s~ern The force and exac~
loca~ion of each compon~n~ may be rcgula~ed rela~ive ~o each other and,
colleclively, rela~iv~ ~o the planing and o~her forces ac~ing on the ve~sel, in
order ~o main~ain ~rim and s~ahili~y during planing
15 The magnitude of downward force to be applied will vary primarily with Ihe
weight, volume(buoyancy) and weued surface of the vessel and the amount of
planing force lhe ~essel ~enera~es a~ planing speed In accordance with this
invention i~ is desirable, a~ planin~ speed to maintain she actual decrease in
wetted surface at less than two thirds of the decrease(from lhe amount of wetted2() surface at res~ the vessel would experience without the downward force
S~abilily and trim should continue to improve with greater downward force tha
will maintain the weued surface increase al less than fifty percent and
preferably al a level of belween five and twenty five per cent of the normal
reduction of weued surface(when ~he force is no~ applied) If desired, enough
25 downward force can be applied ~o increase the wetted surface even as high as
150% orl75% beyond ~ha~ a~ rest which can be an advantage for vessels at hi8h
speeds or operating in heavy seas
As a convenien~ guide for full planin~ vessels the force may be related to the
displacement wei~hl of lhe vessel, i e the ac~ual weight of the vessel ou~ of
30 water Desirably the downward force equals one ~o fifly percen~ or higher and
preferably belween five and ~wen~y five percenl of the displacemen~ weight For
semi-planing vessels Ihe downward force would be generally less, desirably al
leas~ five percenl of lhe displacemenl weight of the vessel and preferably
be~ween eight and twenly percen~
35 The forgoing general ~reatment of vessels wi~h various configurations of
planing surface keel lines, elc illustrates how employment of the dynamic
downward force concepl of this invention can be applied to conventional vessels
~3~5~69
to obtain i~s advanta~es to varying extents However, for new vessels it may wellbe desirable to to specifically design or "tailor" the craft ~o take full advantage
~hereof, par~icularly by incorpora~ing one or more of ~he o~her features tha~
form a par~ of ~his inven~ion
An example of a specially designed vessel is shown in FIGURES 2, 3 and 4 in
which a single componen~ of dynamic downward force is pro~rided located at the
~he siern to accrue special advant~ges of efficiency and structural design whichwill be described Vessel I comprises a hull 5 having a fore pe~pendicular 6 at
the bow which demarca~es ~he poin~ on the apex of the bow that is a~ waterline
when loaded in accordance wi~h the vessel design, and an aft perpendicular 7 at
the aftmost point where the s~ern meets the design waterline, The distance
be~ween these p~rp~l~diculars constitu~s the leng~h of the vessel at wat~rlin~
The wa1erline l~ng~h of Ihe Yessel in this example is 150 feet (305 m) For
purposes of describing ~he hull, ~his distance is subdivided in~o ten equidistant
stations as shown (including each perpendicuar as a sta~ion) each equal to ten
perccn~ of ~he ~rcssel leng~h
The sidewalls ~ of hull 5 ex~ending above ~he waterline meet a~ the prow 9 and
diverge aftwardly ~o a maximum width at abou~ station 6 The sidewall con~inuing
parallel to the stern 10 Each sidewall at its lower margin meets planin~, floor 11
at the bottom ol` the hull to form a chine line 12 which is desirably raised by
providing itwilh a small projection or fin 13 (seen more clearly in FIGS 14 and
22) to channel flow along planing floor 11 Projection 13 desirably is less than
one foo~ (30 5 cm) in dep~h and preferably between one eighth inch (3 mm) and
three inches (75 mm) Raised chine line 12 extends along the length of vessel I
from approximately sta~ion I ~o the stern and forward of about station 2, the
raised chine line essentially serves as a spray strip to divert upward spray A
knuckle 14 above the wa~erline also extends alon~ each of sidewall 8 fram
approximately station I to the stern
Planing floor 11, which extends essentially the full waterline length of the
vessel, is of generally V configura~ion wilh the apex at the keel line As can beseen particularly from FIGURES 5 through 8, beginning with a very sharp V at
foreward perpendicular 6, the planing floor gradually flares outward until by
station 6 it is at a rise of floor angle of 15 25 degrees The rise of floor angles at
stations 7 through 9, respec~ively, are 13 5, 9 75 and 5 25 Af~wards to
approximatelystation6, keelline 15hasadesigndraftof517inches(132cm)
and is substantially hori~ontal, ie parallel to the base plane of the ~essel,
although it may be somewhat concave if desired
17 13~S3~;9
From its apex at about s~lion 6 a ~rian~ular and planar central 100r 16 exten~1s
aftward al a sli~h~lY rising angle ~o the base plane of ~he vessel Central floor Iv,
in the ~ransverse direc~ion is approximately parallel to Ihe vessel s base planeThe base plane ol` the vessel is lhe plane a~ ~he e~treme draf~ of ~he vessel which
5 is both perpendicular ~o the lon~i~udinal vertical centerline plane and parallel
to ~he design walerline of lhe vessel
~esirably, the leading apex t)f cen~ral floor 16 is at or somewhat aft of th~
ex~reme draf~ of ~he vessel Cen~ral floor 16 intersec~s and truncates ~he ridge
line or apical portion of planin~ floor 11 ~hus formir"g two projec~ion lines 1710 diverging aftwardl,v Both ~he V shaped floor 11 and central floor section Iv
termina~e a~ ~ransverse step 4 a~ s~ation 9 exlending betweer. chines 12 By
appropria~ely adjus~in6 ~he slope~of floor 11 and floor ID rela~ive lo each other,
floor 16 may be posi~ioned so as ~o complelely ~runca~e floor 11 a~ transverse s~ep
4, if desired, as shown a~ 16a in FIC 22 At step 4 the draft of floor 11 is 11 ,h inchex
15 (31~cm),
Thus, overall, I`loor confi~ura~ion from midship~ in ~he lon~i~udinal direction
becomes generally llat and rises ~radually to ~he s~ern, desirably by at leasl 25~/o
of lhe draf~ a~ midships and, for improved stabili~y for operation a~ ~ero trim, by
at leas~ 50~s and preferably 75~ of midships drafl In ~his e~ample the rise to the
2() s~ern from midships draft is lOu% and i~ may be even somewhat greater li,e
above walerline) if desired From midships to the s~ern the rise of the floor
longitudinally desirably is ~enerally linear or somewhat concave and with Ihe
avoidance of a lar~e degree of convexity, If convex, ~he af~midships pl;ming
floor desirably has a mean draf~ ~ransversely between chine lines a~ ~he
25 Iransverse ver~ical plane half lhe dis~ance be~ween midships and ~h~ slern
trailing edge no m~re lhan 5I~ ~real~r ~han the drafl al a linear proleclion
belween lhe poinl of grealest draft a~ midships (station 5) and ~he pbin~ of
greatest draft a~ the slern trailing edge, and preferably is no more ~han 25%
~reater
30 Transversely from slation 5 af~ward the chine beam for vessels of this
inven~ion advan~ageously may be relatively large and, desirably, as large or
larger than that al midships In ~he vessel Or ~IGS2-4 lhe chine beam a~
midships is 322 inches (hlh cm) and from sta~ion 7 lo the stern trailin~ edge, 3414
inches (~67 cm)
35 As best shown in FIG 2, s~ep 4 tapers linearly in heigh~ from i~s higbest point at
~he lon~i~udinal centerline line of the vessel toward each chine 12 to become
flush with lhe fins 13 Alternatively ~he step may horizontal from chine to
~3~S~9
chine as shown in FIG 22 and, in ~his case, a bridging fin 18 is provided which is
con~oured ~o conduct across the step 19 the flow which moves aflwardly alon~
the chines The dep~h of the step (measured al ~he cenlerline), in this e~ample
~ 4 inches (8 6 cm), will be chosen wi~h rela~ion lo ~he size of the vessel but can
5 vary widely, desirably from 5 lo 500 millimeters or, in proporiion to Ihe ~,ressel,
be~ween 0 001% and 15% of ~he vessel s draf~
Propellers 20 are Posilioned bila~erallY of lhe keel line immediatelY below
planing floor 11 desirably at or within a distance equal lo 50% of lhe chine beam
in advance of slep 4 Wi~h ~he propellers so posilioned, ~he discharge Iherefrom
I () will tend ~o sweep ol`f eddy curren~s and turbulence ~hal ~ends ~o form, at s~eps,
particularly a~ slower speeds ~hus improving ~he efficie~cy of ~he step
Addi~ionally, the s~ep will ~end ~o remove ~urbulent flow from lhe propellers
away from the af~ward planin~ surfaces, lhus fur~her decreasing friction and
~urbulence normally associa~ed wi~h propellers under a planing vessel
15 A pressure release floor 21 ex~ends aftwardly of s~ep ~ In Ihe ~ransverse
direc~ion pressure release floor 21 is perpendicular lo the lon~i~udinal verlical
cen~erline plane and i~ ex~ends ei~her convexely or, as shown, as a flal plane ~o
its hi~hest poin~ which is ils ~erminus at ~railing ed8e 22 localed at lhe af~
perpendicular 7 Trailing edge 2~, which is parallel wilh the base plane and
20 transvers~ lo Ihe k)ngitudinal centerline plane of the vessel, constitutes Ih~
junclure of release floor 21 and transom wall 23, For maximum effecl, ~he
surface of pressure release floor 21 is a~ or above a plane extending behveen s~ep
4 and trailing edge 22 and, intermediate Ihe slep and lhe ~railing edge, such
surface remains below the horizonlal level of trailing ed8e 22,
25 The rise of release floor fore-lo-arl is desirably equal lo al leasl one lenlh of the
vessel s drafl al midships and il may be as much as one half of the draft, The
verlical lacatian of lrailing ed6e 2~ should be a dis~ance less lharl fifty percenl,
d~sirably less lhan lwenly five percen~ of ~xlreme draf~ of ~he vessel above or
b~lo~ lh~ design walerline of Ihe vessel and preferably wilhin len percenl
30 ~telease flaor 21 should exlend fore-lo-aft far enough to gradually and uniformly
release ~he planin~ pressure imposed on ~he water prior to lhe slep, thus
markedly r~ducing ~he ~urbulence and drag usually experienced a~ the stern of a
planing vessel l)esirably ~his is al leasl a dislance horizonlally of five to twen~y
percenl of Ihe wa~erline leng~h of the vessel, In this example release floor
35 extends fore-to-af~ ten percent of ~he wa~erline lenglh and rises from a draft of
15,4 inches (391 cm) lo lhe 3,4 inches (8 6 cm) below Ihe waterline, 23 2% of
midships drafl
19 13~i3E;9
Twin stern counlers 24 ex~end aftwardly of the aft perpendicular 7 at ei~her side
of the hull 5, each wi~h a heel 25 extending af~wardly of transom wall 23 above
trailing edge 22 Each heel 25 is sligh~ly culwed upwardly both aftward and m
~he inboard direc~ion and is posi~ioned sligh~ly above ~he design waterline in
5 order ~o provide additional fore-~o-aft s~ability against pi~ching by ib "push"
a6ainst ~he wa~er when ~be bow heaves,
The chine line l`in 13 al eilher side ex~ends aflward beyond lrailing edge 22,
cur~ing upwardly along ~he ou~er margins of each heel ~o a point above the
design wa~erline ~o smoo~hly seperale a~ the s~ern lhe flow along ~he raised
10 chine lines
Inner walls 26 of each stern counter 24 is parallel ~o the longitudinal centerline
and each connec~s wi~h transom wall 23 to form an inboard notch for rec~iving
moun~ing s~ruts 27 for foil 3 S~ruts 27 may have pivot bearings (not shown)
mounted in inner walls 26 of the s~ern counter 24 for pivo~ing around an axis
15 which is horizontaJ to lhe base line plane and transverse to the vessel's
longhudinal cen~erline As shown in FlG 16, s~ruts 27 are foil shaped in
transverse cross-seclion with equally cambered surfaces, with the chord
generally parallel to the vessel's longitudinal direction Stru~s 27 at their lower
ends are attached to and support foil 3 Means, no~ shown, may be provided, such
20 as hydraulic pis~ons ~o connec~ s~ru~s 27 ~o transom wall 23 to adjust the
ro~ational posi~ion Or ~he s~ru~s and lhereby ar~iculate foil 3 to different angles
of at~ack Alterna~ively foil 3 and its supporting struts may be permanen~ly fixed
at a predetermined posi~ion for the particular vessel
Foil 3 extends ~ransversely of Ihe vessel's longi~udinal vertical centerline plane
25 and substanlially equally ~o each side thereof The fure to afl posilion of the foil
rela~ive ~o the vessel is desirably with its leading edge al and a distance b~low
trailing edge 22 lo avoid lurbulence therebelween, preferably a dis~ance equal to
a~ least six inches ( 15 cm) bu-, if possible, no~ so far below as to increase the draft
of the vessel If there is a slep, as in the case of step 4, the foil should be
30 posi~ioned horizon~ally below ~he bottom most edge of the step Fore-to-aft, the
leading ed8e Or lhe foil is posilioned vertically a~ ~he trailing edge of the vessel,
as a~ ~railing edge 7
As will be described in more detail ~he chord of the foil 3 is ~enerally parallel
with or at a slight angle to horizontal By changing the rotational position of
35 s~ru~s ~7 the attitude of the foil to the horizontal (and thus to the flow direction~
may be adjusted within a ranBe desirably Or plus or minus ~en to twenty degrees
3L3~ 9
The foil or foils may be posilioned la~erally to the Yessel's longitudinal cen~erline
in various ways as may be desired, so ~hat ~heir resultani force at a particularfore-to-aft loca~ion is a~ ~he cen~erline Thus as in ~he illus~ration above a single
foil may span across lhe cenlerline, one half to ea~h side Alternatively, a
5 separale foil may be pla~ed lo ei~her side of the centerline and equidis~ant
~herelo as shown in FIG 21 'The foil moun~ing in this embodimen~ is
par~icularly useful for localions forward of ~he s~ern Each foil 3e is fi~ed lo ~he
hull by a hydrodynamically shaped slruls 27e in a predelermined orienlalion
(angle of allack) to the flow
10 The foil is ~he preferred means of generatin~ downward force in accordance
with ~his inven~ion For ~his purpose ~he foil may be symmetrical and ~hus
generale downward force by presen~ing an angle of aUack with the flow, with
~he trailing ed8e above the leading edge as viewed Iransversely to lhe flow
direc~ion F'or greater efficiency the foil may be cambered more highly on the
15 downward side ~o provide nega~ive lift (downward force) and is ~hen presen~ed a~
;m angle of a~ck ~o augmen~ Iha~ nega~ive lif~, as needed I)esirably, the profile
of ~he foil is such as to maximize downward force while minimizing induced dra8
over a wide angle of auack range in ~he nega~ive direclion ~wi~h ~he leading
ed8e lowered rela~ive ~o ~he ~railing edge) of up to 10 degrees and over a wide
20 ran8e of speeds Addi~ionally il is desirable for the foil to operate efficien~ly in
the posi~ive direc~ion(wi~h the leading ed~e raised) up ~o 5 degrees or mora to
produce an upward force, ~Such upward force capabili~y may be useful in some
cases in for vessels of this invention for countering pitching farces in heavy
seas ) For these purposes special foils, which form another par~ of this
25 invenlion, are advantageously employed to minimize induced draB and, at Ihe
same time, contribu~e in a novel manner to ~he main~enance of trim and
avoidance of ~urbulent interaclion whh lhe flow passing the hull surfaces
particularly wi~h ~he flow separa~ing a~ ~he slern trailing edge
To avoid ~urbulent interaction with flow passing ~he hull, foils are
30 advan~ageously configured so ~hat lhe flow passing lheir ~railing ed8e (the
"downwash" ) is diverted downwardly, ~he same direclion as ~he force 8enerated
by the foil, as contrasled to conven~ional lifting foils or wings for which the
downwash is in the direclion opposite Or the Benerated force When suitably
configured a~ lheir ~rail portions foils which are cambered forward of a ~railin~
35 portion ~hereof (preferably differentially cambered wi~h an overall greater
camber on the underside) to Benerate a downward force when the leading edge is
presenled to the flow al a negalive angle of a~tack may achieve such diverled
2 1 13~S369
flow The trailing por~ion of such foils, desirably at least the trailing 15%,
preferably a~ least the ~railing 20~o and up to about the trailing 40% of the foil
length, measured along the chord are configured with the upper surface
e~ending convexely downward to the trailing edge and the under surace
5 ex~ending ~o ~he trailing edge wi~h at leas~ substantially less convexity and
desirably is subs~anlially linear and preferably concave
To minimize induced drag the foils of îhis invention, are configured with a
lower surface beginning from a poin~ between about 25 to 55% of ~he chord
dislance from ~he leadin~ edge, which, ~oward the lrailing edge, curves upwardly10 to a point 8~% of the chord length from the leading edge which is a distance
from the chord less than 50% of the distance be~ween the chord and the lower
surl`ace at the be~inning point Addi~ionally the foils may have a relatively
narrow profile, desirably with a maximum thickness to chord length ratio of 0 15and preferably between 0 03 and 0,09
15 Advantageously, for very hi8h speed opera~ion, such foils may be fur~her
modified as to lhe configura~ion of the upper surface and by ~he addilion of a
step or s~eps on ~he foil. The modified upper leading surface configuration
comprises a substantially flattened or linear surface extending from a fine
leading edge between 30~ and 50% of lhe chord distance toward the trailing
2~ edge Steps may be posilioned on lhe foil at a point along either the upper orlower surface a~ or ~oward the Irailing edge preferably at a location where the
surface in both the leading direction and the trailing direction extends parallel
with or inwardly tnwards ~he chord The step may extend at a right angle toward
the chord for a dislance of 01 to lO'Yo or more of the maximum thicknsss of the
25 foil The affec~ of the foil is lo provide a non-linear response At hi8her speeds
flow separation will occur at the step, For a step on the lower surface, this results
in a decrease in force iD the downward direction and fnr a step on the upper
surface, an increase in the force in the downward direction For application of
this these foils in vessel in accordance with this invention a step on the lower30 surface is particularly advantageous in order to provide a less increase in ~he
downward force at very high speeds
In FIG 16 foil 3 has a leading edge 43, a trailing ed8e 44, an upper surface
45 and a lower surface 46 A base or reference line 47 is shown extending from
trailing edge 44 ~owards leading edge 43, at the attitude or, angle of attack at35 which foil 3 generales no lift either upward or downward The leading edge 43
comprises a generally streamlined nose Upper surface 45 af~ward from the nose
is convex with maximum convexity at a point be~ween 7 and 20%, and preferably,
22 ~3~5~69
as shown at 10% of lhe chord dis~nce from the leading ed~e Surface 45 is
concave from ~he indica~ed poinl of maximum conYexi~y to æno~her node poinl of
maximum cont~exi~y 48 and then is convex downwardly to trailing edge 44
Lower surl`ace 46 is convex l`rom leading edge 43 to the point of m~ximum
5 distance from the chord located at 49 and curves from there to trailin~ ed8e 44
~radually up toward the chord and becoming sli~htly concave At 85% of the
chord dis~ance from leading ed8e 43 the distance of ~he lower surface 46 to ~he
chord is approxima~ely 3u~ of that at ~he poin~ of maximum dis~ance 49 The foil
chord len6th of this example is 495 inches (1257 cm) and the thickness to
10 leng~h ra~io is U.04n The perpendicular dis~ance in inches of ~he surfaces from
base line 47 a~ each of s~a~ions l ~hrou~h 33 are found in TABLE 1 The spacin~
be~ween stations is 15 inches (3 8 cm)
~3 ~3L3~)S~9
TA~LE I TABLE 11
Distance be~ween B~seline Dis~nce belween BaseliQe
and Foil Surfac~s in FIG. 16 and Foil Surfaces iQ FIG. 17
STATION UPE~El~ LOWEE~ STATION UPP;~ LOWER
~Ul~l~'A~::E SUF~E'ACE SUkFACE SU~:E'ACE
=============__========== :=====_=======_=======_====
0 0.~00.11 0 0.00 0.11
1 ~.2'70.13 1 0.2'7 0.13
2 0.520.15 2 0.5.j 0.15
3 U.'7~0.~1 3 0.72 0.21
4 u.Bgo 30 4 0 89 0 30
1.~00.3~ 5 1.00 0.38
6 1.10Ij.46 6 l.lU 0.3~1
7 1 . 16O. ~:i 7 1 . 16 0 . 46
B 1.180.63 8 1.18 0.~2
9 1.180.71 9 l.lB 0.58
1.1'10.7'710 1.17 0.65
11 1.15~.84 11 1.15 0.7
.Y0 1~ 1.13 0.77
13 1.10 ~ 1.10 0.~4
14 1.091.~3 14 1.0~ 0.89
16 1 . 06~1 . 09 15 1 . ()8 0 . ~16
16 1 . Ot~1 . 13 16 1 . 06 1 . 00
MIDLIN~ 5 1.15 MIDLINE 1.06 1.04
17 1.051.15 ~TEP -- 1.15
18 1.~51.19 17 1 . 02 1.15
19 1.051.~2 1~ 0.9~ 1.19
1.0~1.23 19 0.89 1.22
21 1. 051 . ~4 20 0.~2 1.~3
2~ 1.061 . ~4 ~1 0.76 1.24
~3 1.0~ 4 22 0.70 1.2~
24 1.~ 3 ~3 0.6~ 1.24
~5 1.. 08 1.19 24 0.57 1.23
2B 1.091. 17 ~5 0.51 1.19
27 l.101.15 ~6 0.44 l.17
2~ ~.. 10 1.10 ~7 0.38 1.16
2~ 1.101.04 28 0.32 1.10
1.091.00 29 0.25 1.04
31 ~.~70.90 30 0.19 1.00
32 U.170.71 31 0.13 0.90
33 0.430.3~ 32 0.08 0.71
33 0.00 0.3B
24 3L3~5~69
In FIG 17 foil 3 is shown wi~h ~he modifica~ions described above for high speed
opera~ion and o~herwise is iden~ical ~o Ihe foil of FIG 16 Specifically the leading
portion 50 of lhe upper surface is substantially linear be8innin8 from leadin8
ed~e ~3 a dis~ance ~owards ~railing ed~e 44 equal lo 45~ of the chord leng~h The5 nose a~ leadin~ ed8e 43 is considerably finer îhan for the embodiment of FIG 16
The forward por~ion ~1 of the lower surface 46 retains generally the same
curva~ure bul ~oward and up lo ~he midpoin~ of ~he fdll is spaced more closely to
the cho~d A s ep ~2 is loca~ed a~ the midpomt having heigh~ equal o 5% of Ihe
maximum ~hickness Or lhe foil The dis~ances ol` ~he surfaces from the base line at
s~a~ions 1-33 are found in TA13LE 11 similarly as for ~he embodiment of FIG 16
The lhickness to chord leng~h ralio is 0 ~45
As best seen in FIG 9 a~ ~he bow 2~ ex~endin~ downwardly from a poin~ ab)ve
~he wa~erline to a curved and s~reamlined leadin6 portion of lhe forefoot 29
foreward of ~he ver~ex (leadin~ edge ) ~0 of ~he bow is bow foil 31 for the purpose
lS of decreasing fric~ion and ~urbulence a~ lhe bow Bow foil 31 is a foil havin8surfaces wilh e~lual camber and having a maximum thickness to chord ra~io of
0 ~63 wi~h the maximum ~hickness al a~ a point 45% of ~he chord len~th from the
leading ed~e The chord length(21 inches or 53 3 cm~ is 6 4 2 of the vessel s mean
chine beam
20 The bow foil is employed uniqllely in ~he presen~ inveniion in cooperation u~ith
he fine and deep bow en~ranc~ The bow foil spli~s ~he water confronling lhe
bow (i e impar~s ou~ward momentum ~here~o) and to maintain the laminarity of
this flow as il passes lhe bow which ~rea~ly enhances ~he ability of ~he en~rance
~o further spli1 ~he flow and conducl it aftward along ~he planing floor wilh a
25 minimum of lurbulence
The bow foil as util~zed in accordance with this invention is confi~ured to
minimi~e lurbulellce and friction holh by slreamlinin~ Or i~s shape and by
providing i~ with a smoo~h and polished surface The foil desirably is neu~ral
Tha~ is confi~ured so as lo exerl no substanlial net force in either direclion
30 perpendicùlar ~o ~he direc~ion of movemenl of ~he foil in water when its chord
exlends in lhe direction of movemenl Preferably ~be camber or contour of the
foil on one side of ~he chord subs~anlially mirrors tha~ on the o~her so that the
foil is balanced or symme~rical relalive ~o i~s chord In i s simplest form for
small vessels ~he foil may be a ~hin flat plate rounded a~ ~he leadin~ and trailing
3S ed8es Generally however ~he foil will vary ir. thickness throu~hout its chorddirec~ion in as streamlined fashion The leading section of the foil extends
forward alon6 Ihe chord from the ~hickest poin~ of the foil ~o the leadin~ ed~e
13/3S3~i9
The ~railing section of ~he foil extends along ~he chord from Ihe thickest poin~ of
~he l`oil to lhe trailing edge
In general, ~he foil is desirably big enough in chord length and in thickness,
relative to ~he size of ~he vessel to impar~ sufficient outward momen~um to the
5 water at serYiCe speed to materially decrease the fric~ion on the vessel hull The
thickness of the foil (at i~s ~hickes~ point) in rela~ionship to its length is
desirably 1% to 40% of Ihe chord leng~h, with the thickest poinl loca~ed aft of the
leading ed8e a dis~ance equal lo 20'Yo to 80~7o of the chord length and preferably
20~ IO 60'7o. ~n relalion ~o the vessel, the principal variables influencin~ thel O choice of thickness of the foil include the design speed of the vessel, its beam and
drafl and the distance between Ihe bow and the foil In general, for fas~er
vessels, ~he "angle of a~tack" of che foil (~he rela~ive sharpness of its leading
edge) is desirably narrower
The foil is desirably posi~ioned on the vertical longi~udinal cen~er plane of the
15 hull of the vessel, wilh its chord coincident wilh such vertical center plane The
span of Ihe l'oil ex~ends a substan~ial dis~ance below the waterline of the vessel,
and, desirably, from ~he walerline down to ~he keel line, Along i~s span below the
waterline ~he trailing edge of ~he foil confronts and is spaced forwardly of ~hebowpeak a~ any point horizonlally adjacent thereof The term "bowpeak" is
20 intended lO mean lhe forwardmos~ point of Ihe vessel a~ any given elevation
above or below the wa~erline In mosl cases a~ mos~ or all eleva~ions ~his will be
the leading edge of the bow buI it can also be other s~ructure such as a bulb, keel
or the like
For besl performance the foil is posi~ioned with its trailing ed8e parallel to the
25 bowpeak throughout its lenglh below the waterline However, if desired, the foil
may be at a different angle ~o the bowpeak, for example, vertical Desirably, also,
the foil is pnsitior,ed with a forward rake, ie inclined forwardly in the upwarddirec~ion
The spacin~ of the foil from ~he bowpeak is important for optimizing the
30 benefits of this inven~ion, The most appropriate spacing will vary with a
number of factors wilh lhe distance generally increasing wilb Ihe service or
design speed and wi~h Ihe beam of ~he vessel and wi~h ~he ~hickness and chol d
length of the foil and vice versa While the spacing may ~hus vary, the foil
should be posilioned close enouRh ~o the bowpeak tha~, at the vessel's desi~n
35 speed, a useful amounl of outward momentum the foil impar~s to the water
remams when that water passes ~he vessel's bow,
;3~;9
2~
Usllally ~he trailing edge of the l`oil should be spaced from Ihe bowpeak in order
to obtain ~he full benefi~s of ~he invention Tha~ spacing may vary not only in
accordance wi~h ~he fac~ors already men~ioned above bu~ also with the degree of
sharpness ol` the bow ~he sharpness of ~he trailing sec~ion of the foil and other
fac~ors influencing ~be de8ree of friclion and turbulence ~hat is genera~ed at the
region of ~he foil trailing edge and the bowpeak However lhe bowpeak and the
foil trailing ed8e should desirably be spaced apart a distance such that a
conlinuous s~rean~line condi~ion is maintained in ~he water as i~ passes adjacent
lhe foil lrailin~ ed~e and the bow The more full or bluff the bow or ~he trailing
I n sec~ion of lhe foil the wider lhe spacing that is needed ~herebetween to maintain
slreamline flow in the adjacent region, In practice, lhe foil is desirably spaced
I`rom the bowpeak at any horizonlal point at a horizontal dislance equal to or
grea~er Ihan ~he maximum lhickness of the foil (measured from the ~railing edge
of the foil) Particularly for higher speed vessels a spacing of be~ween 12 and
302 of beam widlh of the hull is desirable
The en~rance of a vessel is thal por~ion of lhe forebody where lhe seclion areasare increasing, i e ~o Ihe point of maximum seclion such as al the beginnin8 of a
parallel middlebody For ~he embodiment of FIGS 2-4 this is approximately at
slation 4 However lhe novel en~rance nf lhis invention may be conveniently be
described by reference IO sections thereof extending 10~ and 20~ of ~he
wa~erline leng~h ol' lhe vessel al`twardly from the fore perpendicular In the
vessel of ~IGS 2-4 this constitu~es the forebody portion e~tending from the foreperpendicular aftward to slations I and 2 By reference lo FIG 8 the entrance 32
isseen ~o be fine, ex~ending outwardly, bolh upward and aflward~ aL a relalivelynarrow angle A1`l of lhe fore perpendicular 6 the bullocks 11, as shown in do~edline a~ s~ation 1/2 in FIG 8 are slightly concave in vertical cross-sec~ion but, if
desired, may be straight In Ihe ver~ical direction lhe entrance is exceptionallydeep for a planing vessel, wi~h the lower margin 33 lhereof aftward of
perpendicular 6 to slalion 2, a~ a drafl of approximalely 69~ inches (177 3 cm)
31) abou~ 135% of lhe deepesl draf~ aftward of entrance 32 The lowes~ extremity of
~he entrance is consliluled of forefoot 29 connecled aflwardly ~o and forming
par~ of a skeg 34 bearing forward wing 35 which will be described in detail
subsequently However, ~o be noled here is tha~ lhe skeg wilh its narrow profile
and small volume together wilh forefoot 29, forms the lowermos~ portion of ~he
en~rance Aflwardly of stalion 2 of enlrance 32 planing floor 11 continues to
drop gradually lowering in angle closer to the horizont~l, 'dS shown in ~IG 7
~7 ~ 9
As may be s~en ~he fine deep en~rance 32 has a relatively low volume and hence
low buoyancy Also i~ has a lar~e wet~ed surface disposed at a high ver~ical angle
which can engender subslan~ial nega~ive lif~ The amoun~ of surface disposed in
~he horizon~al plane which could ~enerate positive lift is relatively small
S The effec~ive dep~h of this novel enlrance for a planing vessel may b~
charac~erized by the mean dep~h or dral`~ over its leng~h or a forward por~ion
thereof Mean drafl may be es~ima~ed by dividing ~he area on the longitudinal
ver~ical cen~erline plane ~hat falls wi~hin ~he en~rance by the length of the
enlrance .
The mean draf~ thus es~ima~ed may be compared with ~he deepes~ draf~ of the
vessel afl Or ~he en~rance lypically at around s~a~ion 4 ~o 7 Desirably in ~he
prac~ice of this aspec~ of ~h~ inven~io~ ~he entrance is de3i~ned relative o ~heres~ of ~he vessel so ~ha~ ~he mean draft of the entrance por~ion extending a~
leas~ 20% or even 10% of the wa~erline leng~h of ~he vessel aft of the fore
perpendicular is al leas~ ~n% of deepesl draf~ aft of the entrance and desirablyeq~ al o and even up ~o 175% ~rea~er ~han deepes~ draf~ aft of ~he entrance Forthe embodimeDt of FIG I the mean draft of the forebody from the fore
perpendicular ~o sta~ion 1 is 117% and from ~he fore perpendicular ~o s~ation 2 is
126% of ~he deepes~ draf~ afl of entrance 32 (48 1 inches or 122 2 cm a~ about
2t) station 2 to sta~ion 6 ) Meall draf~ is es~ima~ed by first determining the area of ~he
longi~udinal c~nIerline plane below ~he design walerline and between ~he fore
perpendicular ard sta~ions 1 and 2 respecIively ~ha~ is bordered on the
downward and foreward jides by ~he line of ma~imum extension of Ihe entrance
(including askeg or equivalent keel extension)
The narrowness or fineness of the forebody and the rela~ive absence of effec~iveplaning surface a~ the entrance may be characterized by ~he raLio of mean chine
~eam ~o draft (excluding the dep~h of any skeg or wing) Eleginning from the
fore perpendicular even up lo station 2 ~hal ra~io will change greatly in ~he
transition towards the dras~ically smaller raise of floor aftmidships However ~he
ratio of mean chine beam to keel line draft (no~ including ~he depth of a skeg or
olher projection below the keel line in determining draf~) a~ the reference plane
a~ each of sta~ions I and 2 is a convenien~ measure of the overall fineness of Ihe
en~rance both for characteriza~ion and design purposes Desirably ~he ra~io of
mean chine beam ~o keel line draf~ a~ sta~ion 2 (20% percen~ of ~he vessel s
10ngth af~ of the fore perpendicular) is less ~han 4 and less than 3 at station 1
For the vessel of FIG I ~he beam to keel line draf~ ra~io a~ sta~ion 2 is 3 06 and a~
station 1 1 6
28 ~)53~;9
1~ is ~n be understood lhat lhe foregoin~ are essen~ially useful conventions forease ol` characteri~alion and understanding of an enlrance uniguely suitable foruse in this invention Expressed conceptually, a planing vessel in accordance
wilh ~his invenlion will follow the general principles of providing lower volumeand buoyancy forward, providin~ less lifting (planing) surface forward and
providing a greaser amount of welted surface forward lha~ may generale
negalive lif~ forces, which toge~her coopera~e uniquely with lhe dynamic forces
provided aftward to crea~e an efficienl and slable vessel Looked a~ in anolher
way a highly efficien~ entrance is prnvided, which for a planing vessel would
I () olherwise be of ques~ionable slabili~y and possibly dangerous, that in addition to
providin~ i~s efficiency will cooperale wilh af~ward dynamic forces lo trim ~he
vessel and develop ~he imporlan~ additional efficiency which accrues Namely,
~he ~hin, d~ep en~rance ~hus permi~led, avoids ~he build up of pressure under ~he
bow and consequen~ spray r oo~ ~hal so decr0ases the efficiency of con~rentionalplaning vessels
The foreward ske~ of lhis invenlion is localed forward of midships desirably
exlending alorAg ~he longitudinal centerline plane of ~he vessel af~ward from lhe
re~ion of lhe fore perpendicular Il may usefully ex~end as far af~ as 30 to 40
percenl of ~he distance to ~he af~ perpendicular The skeg is attached to and mayextends down from ~he keel of ~he vessel along lhe hull line a distance typically
of belw~en three inches (7 cm) and as much as fif~een fee~ (460 cm), depending
on lbe size of lbe vessel and ils drafl Desirably this dislance is equal to between
one fourlh of a percenl of mean chine beam and preferably lhree quarlers of a
percent or ~realer, even as high as fiv~ percent of the mean chine beam
distance In proporlion lo lhe drafl of lhe vessel lhis dislance downward from lhe
keel line desirabJy is al leasl 10% of ~he extreme drafl of ~he vessel wi~ho~l lhe
skeg,
The skeg will be conslructed to meet the s~ruclural demands imposed by the yaw,
turnin~ and other forces it will encounter and the s~ruc~ural demands of
3() carrying as forward wing or plane if moun~ed lhereon as will be described The
skeg will be streamlined ~o minimi~e lhe friction and ~urbulence it creates and il
is advantageously foil shaped with relalively sharp leading and trailing edges
in lhe embodimenl of FiGURES 2 lhrough 4 skeg 34 is a downward conlinuation of
the bow Fore-to-afl skeg 34 exlends 261 inches (663 cm), from the fore
perpendicular to approximat~ly stalion 2 and is 20 inches (50 8 cm) deep As
be~ter seen in FIG 9, skeg 34 is foil shaped with lhe same curvalure on each
surface and the chord direclion fore-lo-af~ The maximum ~hickness is
~9 ~L3~53~9
approxima~ly 9,4 inches or 239 cm (0027% of the chord dis~ance) and this
occurs ~0% of ~he chord dis~ance from the leading edges 36 It can be seen ~hat
the depth of sl;eg 34 is substantially ~rea~er ~han its thickness
The foreward ske~ wi~h or wi~hou~ a win6 moun~ed ~hereon because of its
5 positionin~ is more effeclive in counterin~ Ihe forces acting on ~he bow and
o~her forward por~ions of ~he vessel to move it off course, par~icularly yaw
forces A foil shape will enhance ~he effec~ of skeg in impar~ing direc~ional
stability ~o ~he vessel as ~he la~eral pressure of lhe flow along its leading ed8e
will lend ~o bias ~he jke8 a~ainsl la~eral movement in either direclion
10 Importantly, when i~ is u~ilized toge~her wi~h the other aspects of ~his invention
~he skeæ also act~s as a downward extension of ~he en~rance which adds to ~he
ne~a~ive pressure differential and hence downward suc~ion force a~ the bow
This force will cooperale wi~h an af~ward dynamic downward force and upward
planing forces acting be~ween ~he skeg and ~he aft downward force ~o maintain
15 vessel ~rim,
The forward wing or plane is also ~o be loca~ed forward of midships and for
maximum effec~ will also ex~end af~wardly of ~he re~ion of the fore
perpendicular Depending upon its shape ~he wing may usefully extend
aftwardly as far as 30 ~o 40 percen~ of ~he dis~ance to ~he af~ perp'endicular
20 In general ~specl Ihe forward wing is desiæned ~o have a s~reamlined and low
resis~ance profile In ~he broades~ sense Iha~ ~he term wing is used herein, it
need not be foil shaped or have a lifting capacity or capabili~y However the
wing may he advan~ageously provided wi~h a liftin~ capabili~y and ~hus be
u-ilized to also provide a dynamic lifling or depressive force on the vessel
25 foreward of midships for ~rim con~rol ei~her independen~ly of or in cooperation
wi~h the o~her trimming forces in accordance with ~his inv~n~ion
The forwald wing ac~s efficienlly because of i~s ~lesign, posi~ionin6 and its
orienta~ion relative ~o the vessel travel direc~ion Also since its mode of opera~ion
in decreasing pilch is dynamic, i e by its fric~ion, pressure and drag in the water
~0 ver~ically it is more efficien~ as compared ~o static dampers, such as ballast
lanks, which increase the weigh~ and ~hus ~he wet~ed surface which, in turn,
increases Ihe fric~ion on ~he ship
Advanta~eously as shown in ~he embodimenL of FIGURES 2 through ~, the
forward wing 35 may be a~ached ~o the underside margin of ~he forward skeg 34
35 and supported ~hereby Al~erna~ively, ~he wing may be fixed ~o ~he sides of ~he
hull at some forward posi~ion, desirably a~ or close to the bow, and extend out
~hereÇrom moun~ed somewha~ similarly to roll suppressor fins or wings which
13~15;~9
are con~rentionally mounted on vessel hulls amid~hips The forward wing may
also be moun~ed in a similar fashion on opposile sides a~ the lower end of a bowfoil a~tached at lhe bow of the vessel as previously described,
The wing desirably has a dimension in ~he ver~ical direction (wi~h respect to the
5 vessel's orien~a~ion) ~hat is smaller on average ~han i~s chord distance (width),
which ex~ends generally in ~he horizon~al plane, usually by a ra~io of a~ least I ~o
2 and preferahly of I lo 10
The wing desirably is bilaterally symme~rical about a longitudinal median axis
and is posilioned wi~h ils longiludinal median axis coincidenl with the vertical10 longi~udinal centerline plane of ~he vessel and its la~eral axis perpendicular ~o
such cen~erlirie plane, The wing is moun~ed on the skeg both for ease of
positioning relalive lo the vessel and lo space ~he wing l`rom lhe keel so there is
an adequa~e head of wa~er above ~he wing to impede i~s upward movement
The wing advanlageously has a generally swep~ back configuration, preferably
15 of a delta design as illuslra~ed in FIGS 1-4, wi~h the leading apex 37 in ~heforeward direc~ion of lhe vessel ~o the poin~ where the keel line meets ~he bow,although it may projecl a dis~ance in advance of the bow ju~clure or begin a
dis~ance af~ ~hereof, The anale of sweep black of ~he leading edges 36 of the wing
35 from ~he perpendicular ~o lhe vessel ver~ical longiludinal cerl~erline plane is
20 desirably a~ leasl forty five degrees ~or the advantageous longer wing between
5~0 and 3~0 Or lhe vessel lenglh al walerline~ the angle he~ween lhe leading edge
on ei~her side of ~he longi~udinal ver~ical cen~erline plane is desirably be~ween
1 and 15 de~rees (i e an angle of sweep from the longiludinal vertical centerline
plane for each leading edge of ~2 1/2 ~o 89 1/2 degrees) and in lhe illuslrated
25 embodiment 2 degrees The wing surl`aces 37 for ~his ~ype win~ are preferably
subs~anlially planar and dihedrally disposed, i,e, an~led wi~h respect to ~he
horizonlal l()ward lheir oulboard margins a~ leading edges 36, downwardly,
preferably 2 lo 15 degrees, This is for the purpose of channeling the flow alonglhe center of lhe win~ ~o fur~her enhance direclional s~ability Preferably ~he
30 leading edge 36 to either side is linear The swept back wing design has the
particular advantage lhaL only a minimum amounl of roundling or streamlining
is required of ~he leading edges in order ~o present a low resistance profile in the
vessel lravel direclion ~hus permi~ing more blun~ profile in ~he vertical
direction for drag or resis~anc~ ~o pitch The swept back wing located at the
35 entrance foreJnidships desirably extends between 5 and 30 percen~ of the
waterline lenglh of lhe vessel In ~he example of ~IGS, 2-4, wing 35 extends
3, 13~)S3~9
~w01ve feel (366 cm) from af~ of ihe fore perpendicular 6 aflward ~o abou~ station
The swept back wing may be modified is shown in FIG 11 by lhe bilateral
addition al leading edges 36 of swept forward wing ex~ensions 38 which extend
5 ou~board a~ an acu~e angle lo ~he longi~udinal cen~erline of the vessel in ~he~ravel direction and are disposed in the same plane as the wing surface to either
side i e at the same dihedral an~le as shown As seen in FIG 1~ forward winas
are foil shaped and have symme~rical surfaces, bu~ ~hey may be differentially
cambered ~o provide lift e~en a~ a zero angle of attack As well as providing
addi~ional lir~ forward win6 ex~ensions 38 will conduc~ flow from ~heir ~ips 39
inboard to skeg 34, thereby enhancing ~he direc~ional stabilization of the vessel
The al~erna~ive skeg moun~d forward wing illus~ra~ed in FIG 12 has leading
~nar~ins b~ginning a~ leading ed8e 36b,which connec~ ~o in a generally
ellip~ical configura~ion ~o lrailing apex 42, and a planar surface 37b
15 If lifling force on lhe wing is no~ desired, the wing surfaces are positionedaccordin~ly~ which l`or a fully planer wing would be horizon~ally This may be
approximated by making sucb surfaces parallel lo ~he baseline plane of the
vessel However, as is expIained in more dctail, the forward wing may serve
another imporlaQ~ func~ion in ano~her con~ext of this invention, ~hat of
20 providin~ a positi~e or negative lifting force on the forward sec~ion of the
vessel, ~or Ihis func~ion ~he forward wing may be se~ at an angle of attack lo
provide lhe desired lift in the desired ver~ical direc~ion To thus util~ze the
forward win8 to create a ver~ical force on the bow, ~he win~ may be positioned at
an angle with Ille horizontal, or by approximation, wi-h the base planc of the
25 vessel, For a relatively long win~, e g extending aftwardly between 15 to 30 per
cen~ of lhe waterline leng~h of ~he vessel, a minor angle of up to five degrees in
the desired direction from lhe horizonlal may ~enerale an adequate force, For
shorter win~s lhe angle may be correspondingly wider, If desired, the wing may
be mounted so lhal the an61e of lhe wing surfaces to the horizontal may be
30 rapidly adjusted durin~ operation of the vessel For example a planar del~a wing
may be pivotally moun~ed on Lhe skeg at i~s forward apex and the trailin6 end ofIhe win~ secured ~o ~he skeg by hydraulically operated jacks for vertical
adjustmenl
Th~ forward win~ will perform an important function in cooperalion wi~h lhe
35 fine and deep entrance of lhis inven~ion lo compensate for the lack of planing
surface at this enlrance and for ~he negative lift ~enera~ed by suction forces a~
this entrance which can o~herwise impart instability to the vessel, particularly
~2 ~36)5;~S9
in disturbed wa~cr The a~ ude of ~he for~ard wing may be se~ to provide an
upward force desirably a one to len degree angle downwardly a~ the trailin~
ed~e in the case of Ihe swep~ back wing This upward force will supplemen~ ~he
dynamic f()rces ac~in~ aflwardly in supporting lhe bow lO maisltain Irim and,
5 impor~dn~ly to counler downward pi~ching forces which ~end ~o submerg~ ~he
bow In ~he embodimen~ of FIGS 2-~ ~he wing 35 is fixed at àn average angle of
two degrees downwardly at ~he afl lo provide a dynamic upward î`orce for ~hi~
purpose Oplionally, if desired ~he forward wing may be utilized in this
inven~ion lo provide a dynamic downward force compunenL ~G supplemi;nt a
10 downward force at an aftward loca~ion
ln o~her embodimenls particulally ~hose in which ~he span direction ex~end~
~enerally outboard Or ~he vessel Ihe wing may comprise a foil to each side ol' ~he
longitudinal ver~ical cenlerline plane wi~h lhe span of each, or a portion
thereof, exlendin~ ~tnerally ou~wardly of such plane If no lifting force is
I 5 desired, ~hen a neu~l al or symmelrical foil shape may be s~lec~ed and ~he foil
posi~ioned wilh i~s ~hord parallel ~o Ihe vessel lravel direc~ion Or if lhe foil h~s
an unbalanced or liftin~ profile it would be positioned with an an~le of a~tack
which would cancel ou~ the lif~ing force o~herwise crea~ed ~y ~hal
profile Al~ernalively the win~ may be fi~ed ~o Ihe sides of the hull at some
20 I`orward posi~ion. de jirably at or close ~u ~h~, bow and extend ou~ ~herefrl)m
mo~ln~ed somewhat similarly lo roll suppressor ~ins or wings which are
conven~ios~ally moun~ed on vessel hulls amidships
However, ~o provide a lif~ing or depréssin~ forcé on thé forward sec~ion of the
vessel ~his lype of forward win~ may be sel a~ an an~le of altack lhat gives thè25 desired lift in ~he desired veltical direction Either a neulral or a camhered foil
may be employed and posi~ioned appropriately to give ~he desired vertical force
on ~he vessel If desired, lhe foil may be mounled so thal the angle of attack iseasily adjustable during opera~ion of the ship, in order to vary ~he vertical force
it imposes al any particuJar speed ol~ ~he vessel
30 The amounl of liftin~ or dampening force provided by ~he forward wing will also
vary with its posiliuning al ~he en~rance antd wi~h ~he amounl of planing
surface, measuréd as the area sub~ended by ~he wing in the horizon~al plane For
maximum affect, Ihe win~ is posilioned in ~he forew~rd ~hir~y percent of ~he
vessel's wa~erliné leng~h and preferably in ~he forward ~wen~y percellt as
35 shown in the emodimen~ of FIGS 2-4, In that region, the area in the horizontal
plane sub~ended by ~he wing deslrably is al leas~ two and less Ihan seventy
square inches per foul ~u 4 to 15 sq cm/cm) of the vessel's wa~erline len~th and
33 ~3C3~3&9
preferably between fiYe and fif~y square inches (1 and 10 sq, cm/cm) The area
of ~he planin~ surface 37 on the ullderside of wing 35 of FIGS is approxima~ely 9
square fee~ (~361 sq cm)
Ei~her lhe forward ske~ or the forward wing may be employed on a vessel alone
5 Ol ~ogelher and wi~h nr wi~hou~ lhe olher fea$ures of lhis invention However,
each is of parlicular advan~a~e in a vessel in combinalion with lhe basic trim
and heave con~r()i rea~ures of this inven~ion because of cooperative
rela~ionships d~scribed Addi~ionally, since ~he trim and heave control features
will tend ~o main~ain ~he bow in ~he waler more constanliy in heavy seas, ~he
10 skeg and forward win~ will ~hus be more constanlly under wa~er to make their
con~ribu~ion in reducin~ ~ ~w and pilch
It will be seen ~hat in employmen~ of ~his invention wi~h a mul~iple hull vessel,
for example a ca~amaran or Irimaran, having planing surfaces lha~ each hull
may embody one or more of Ihe described fea~ures, e g, a narrow and deep
15 en~rance, forwal d ske~, fol waI~d wing, bow foil, planing floor rise ~o lhe s~ern as
described, a slerl~ pressIlre reluase zon~ and associa~ed ~ransverse step, and flow
separa~ion chine fins al the stern Preferably al leas~ the outer hulls are
iden~ical lo each o~her as ~o ~hese features A ~ransverse foil or group of foils for
~eneralin~ a downwal d furce as previolJsly described, would still desirabl~ be
20 bila~erally symmeIrical of the lon~i~udinal centerline plane of ~he vessel
However, ~he centerline plane would be central ol` the entire vessel and lhis
would be in ~he case ol` a catamaran, equidistan~ between the two hulls
The operalion of lhe vessel of ~he embodiment of ~he invention as shown in FIGS
1-4 wilh ~he loil se~ al a ne~a~ive angle Or 5 degrees (leading ed~o horizonlally
25 below the lrailing edge) from a standard lank ~ust of a model of a scale of 24 lo I
pulled throu~h the wa~er will now be described At l~es~, vessel I will ride in ~he
wa~er al zero lrim A~ low speeds, up ~o around ~ knols, Ihe vessel will be in
displacemen~ mode As speed increases ~o ~he 30 knot ran8e planing forcs will
increase and, at the same ~ime lhe downward force impar~ed by foil 3 and ~he
30 suc~ion forces a~ the bow will also increase These forces will ~enerally offset
each o~her lo maintain a dynamic fore-~o afl balance of ~he vessel The vessel
will continue generally in ~rim throu~h a speed ran~e up kl appro~imately 60
kno~s wi~h no si~ns Or ins~ability even in disturbed water equi~ralen~ to 3 and 6
foot waves wiIh wave periods from 4 to 16 seconds The heave of the vessel
35 throu~hout the speed ran6e is sligh~ly ne~a~ive, i e the draft and, hence, ~he
we~ed surface is increased wi~h ~he vessel below ~he a~ rest waterline as much
as 5 inches or 12 7 cm (appro~ 10% of draf~) The maximum rise of the bow al all
13~5
34
speeds is approximalely ù 6 degrees and a~ hi~her speed the bow is at a ~ega~ive~rim angle of ~s much as û 3 degrees.
The lack of planing surface at îhe enîrance (other than Lhe forward win~) and
the downward suction force bias the bow downward to prevent the rise of the
5 bow normal to a convenlional planin~ craft. At the same time. the upward forc
of the forward wing 35 and of the aftward "lever arm" of ~he downward force a~
~he stern and ~he midshiDs uDward Dlanine force bias the bow uDward to Drevent
the bow trom digging in Throu6hout ~he spe~d ran~e the usual large spray root
and bow and s~ern wakes of a planing Yessel are a~sent. Wi~h increasing spee
I () ~he s~ern foil 3 and the forward wing 3~ and skeg 34 ~end ~o hold i~ to trim in a
highly stable and straigh~ course
2~
