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Патент USA US2127475

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Aug. 16, 1938'.
" $127,475
'1 Filed Aug‘. 2, 1955 " '
Patented Aug. 16,1938
' .
srnr’s s'rEa'N
Vladimir Yourlrevitch, Paris, France ‘
Application August 2, 1935, Serial No. 34,331
In France December 6, i934
2 Claims.
(Cl. 114—-5d)
This invention relates to the hulls of ships and
is directed tov novel con?gurations in the stem
or aft portion thereof and more especially below
nal movement of the hull is- thus lessened and
the speed materially increased without change in
~ persistency of vibration becomes, with time,
them which seek to direct the ?ow of water to
the waterline.
One object of the invention is to stiffen the
aft portion of propeller driven ships in such manner as to minimize vibration resulting from the
operation of the propellers and from other
causes. This vibration, which is particularly no;
10 ticeable at certain speeds, is very annoying and
uncomfortable because of its persistency and this
driving horsepower of the vessel.
Another object of the present invention, de-,
sirable in all hulls, but particularly in hulls of
fast moving vessels, is to increase the efficiency of
the propellers by properly directing the flow of
water past the hull in such manner that it is
fed to the propellers in the most emcient way.
Various expedients have been resorted to in hull 10
construction to this end, but the majority of
prejudicial to shell plating and structure of the
My experiments and research in this connec-
the propellers counteract any increased e?icienc'y
thereof by the building up of increased resistances
to forward movement of the hull. For example, 15
tion have convinced me that this di?iculty is
largely due to the inherent properties of hull
construction as heretofore designed and which
result in hull forms having appreciable overhang
‘l0 at the stern, making it impossible to properly
brace said stern portion or incorporate therein
the desirable inherent buoyancy or displacement.
As a result, the stern portions of ships, in the
great majority of cases, project in an aft direc-
it has been proposed to fit all sort of fins guid
ing water towards propellers or to broaden the
hull directly forward of the propellers in various
waysyin order to cause the water to be drawn
inwardly back of such enlargements and into 20
the grip of the propellers, but these expedients,
although tried in various ways, have not proven
satisfactory and they tend to slow down the boat
due to increased resistance.
‘:5 tion beyond the buoyant body of the hulls and
this constitutes an ideal condition for vertical
The present invention accomplishes eiiicient
propeller operation in a thoroughly satisfactory
and lateral whip, particularly in overhang por- _ way and through the formation, within the con
tions of the hull.
With these considerations in mind, the present
3" invention provides for materially increased lon_ gitudinal and lateral sti?ness and rigidity of
the stern portion of the hull, so as to properly
reinforce the same against lateral whip as well
tour of the hull below the waterline, of channels
which extend fore and aft and are of convergent
divergent contour, so as to produce, in effect, a 30
substantially Venturi contour channel at each
side of the hull, so that, as the hull of the ship
moves forwardly, the water streams ?ow smooth
as vertical vibration. ‘
ly through these channels with a minimum width
35 _ Another object of the invention is to increase‘ of hull cross section between them. These 35
the speed of ships of the faster type, through the‘ streams unite back of the rudder, which is‘in'
employment of novel stern construction. This
object of the invention, has to do,-more particularly, with naval destroyers, cruisers and the
40 like, which travel at express speeds, although
this feature will also be of advantage in fast
ships, other than naval vessels. For example,
when a destroyer is traveling at high speed, it
has a pronounced tendency to “squat” at the
‘ 45 stern. In other words, the bow appreciably rises,
terposed between said streams, in long ?owing
lines, so as not to ‘set up eddies or result in ap
preciable resistance.
The propellers are mounted to partially pro- 40
iect within said channels and are preferably 'jux
taposed with contracted section of the above
channels so as to cause the propeller tips to
operate sensibly within the channels’ gullets and
so as to receive the water streams in a most e?i- 45
while the stern correspondingly lowers in the
water, thus causing‘ a partial up-ending of the
hull which, in case of an exaggerated squatting,
cient way. Contraction of the water'?ow by these
Venturi-like channels produces sidewise an in
jector action on’ the adjacent water streams
increases its resistance to passage through the
which are drawn in a wide flow towards the pro
QM) water. The present invention, when adapted to
hulls of this character, serves to so increase the
buoyancy of. the stem or aft portion of the hull
pellers, the emciency of which is materially in- 50
creased because of this accelerated ?ow of water.
An important feature/of this invention resides
as to minimize this settling e?ect at high speeds. - in the formation of what may be termed ‘a bui
in order that the hull may be maintained at “bous cross section at the keel, in the vicinity of
55 a more even keel. Resistance against longitudi- the propellers, and extending forwardly and aft 55
therefrom and. tapering off in both directions
into a substantially torpedo shape. Such a bul
bous formation at the keel produces several of
the advantages to which I have hereinbefore re
ferred. When made of the tapering form, simu
lating a torpedo shape, instead of materially in
creasing the resistance to forward movement of
the hull as all other water-guiding protuberant
devices, such as de?ectors, ?ns, nozzles, etc., in
10 variably occasion, this bulbous keel formation
reduces on the' contrary the resistance. At the
same time it increases the buoyancy through in
creased displacement of the stern portion of the
hull. It reduces the so-calied squatting. It al
15 lows of proper reinforcement of the stern por
tlon'of the hull by providing backbone at the
keel, so as to minimize vertical or lateral vibra
tion or whip. It permits of the narrowing of
the hull in the vicinity oi’ the water line, in view
of a further reduction of the resistance, the de
?cient displacement on the water line being
counterbalanced by the additional displacement
of the bulbous keel formation. It provides a con
venient means for the formation'of the converg
26 ent-divergent channels to which I have referred
and it provides additional fuel or cargo space if
this is desired. It also may be utilized to serve
as a water ballastltank, through the regulation
oi’ the contents of which the hull may be proper
30 ly "trimmed" in a fore and aft direction. Fur
thermore, when so used, the ballast is at the
keel where it is most efficient in preventing roll
ing or wallowing in a heavy sea or cross swells.
Another important feature of the present in~
35 vention, as‘will hereinafter be more fully de
scribed, resides in the reinforcing of the keel
at the stern, as hereinbefore explained, so that
the lower end of the stern post may be properly
anchored and an enclosed rudder used, which
40 rudder may be either of the balanced or un
balanced type.
Features of the invention, other than those ad
verted to, will be apparent from the hereinafter
detailed description and claims, when read in
conjunction with the accompanying drawing.
The accompanying drawing illustrates one
practical embodiment of the invention, but the
drawing is to be understood as illustrative, only,
and not as de?ning the limits of the invention.
- Figure 1 is a side elevation of a stern of a
present day conventional construction, and I
have accordingly illustrated, in the accompany
ing drawing, conventional hull construction and
by comparison have shown the hull of the pres
ent invention. It- should be understood in this
connection that the two hulls here compared re
late to boats of the same class or kind and that
the present invention may be modi?ed in adapt
ing the same to hulls of various types.
Referring ?rst to Figures 1-6, these ?gures 10.
represent a conventional hull of a fast vessel in
dicated by the reference character i0, and the 4
contours of which hull are not only. narrowed
in the vicinity of the load waterline II, in view
of reduction of the resistance, as will be apparent
from the successive equidistant transverse sec 15
tions or frames indicated at I, 2, I, 4 and 5 in
Figures 1-3, but also are tapered upward aft in
vertical plan for the same purpose.
When a hull is thus narrowed and formed as
shown, it will have an appreciable overhang at
the stern and in practice, it may be likened
structurally to a spring l2, as shown in Figure
6. This spring has superimposed leaves l3, l4,
l5, etc. rendering the same vertically resilient
as it extends from its zone of anchorage IS. The
overhanging stern of the hull of Figures 1 and 2
possesses the same broad peculiarities because
the ship construction is unavoidably of a more
or less resilient nature and possesses some "give”
when made as described, as the overhang stern
portion must be of a light construction and does
not allow of sufficient internal bracing to make
it rigid. As a result, the stern of the ship of
Figure 1 will vibrate vertically under the action
of the propellers‘ indicated at I‘! and under
buffeting of the seas. Similarly, since the stem
is relatively narrow, particularly below the
waterline ii, this portion of the hull will have
an inherent tendency to weave or whip laterally
due to the operation of the propellers and to the 40
passage of water streams past‘the rudder.
Graphically, the cross section of the hull, at
the section line 4--4 of Figure 3, may be com
pared, for practical purposes, to a girder sec
tion, such as shown in Figure 5, in which the
upright web i8 corresponds to the vertical di
mension of the hull, while the ?anges i9 and 2|
correspond to the decks or other internal brac
conventional hull.
Figure 2 shows plan traces of the stern portion
and waterline contour of the hull portion of
Figure 1.,
ing. This section is taken in the vicinity of the
propellers but aft of this the vertical dimension
of the hull decreases rapidly until it is relatively
shallow. Thus a girder of the kind shown will be
Figure 3 shows the so-called “body plan” or
vertical traces of several transverse frames of the
hull indicated in Figure 1.
susceptible to_ appreciable vertical de?ection as
well as appreciable lateral de?ection, particu
larly in the lower portion of the web I! thereof,
Figure 4 is an outline cross section taken at
the section line_4—4 of Figure 1 and showing
60 deck lines, shell plating and waterline.
Figures 5 and 6 give a simpli?ed image of
the mechanical properties of the stern section of
the hull of Figure 1.
Figures 7, 8, 9 and 10 correspond to Figures
1, 2, 3 and 4 of the drawings of a conventional
hull, but show a hull embodying the present
Figure 11 corresponds to'Figure 5 but gives
a simpli?ed image of the mechanical properties
70 of the hull of the presentinvention.
Figure 12 is a comparative graph of the areas
of cross sections of the hull and of the weights
. or loadings of different hull constructions.
It is felt that the present invention may be
best understood if explained in connection with
under the actionof the propeller and the other .
forces to which I have referred and this de?ec
tion will of course increase progressively aft.
This is one reason for pronounced vibration in
the stern of ships as now constructed and, prior
to this invention, no adequate solution has been
found to minimize the same to a point where it
will not be uncomfortable to the passengers or
where it will not produce undesirable strains on
the hull structure. The present invention solves 65
this problem in a simple and e?lcient manner.
Thus, as shown in Figures 7-11, the rear
frames, at the successive transverse sections i,
2, 3, 4 and 5 are formed with appreciable hollows 70
accentuated in the region of the load waterline
ii and end in the region of the keel in pro
nounced bulbous contours formed by club-footed
frames and indicated generally at 2|. The
"traces shown result in a bulbous keel portion in- ‘(8
28 of the present invention are positioned in
dicated generally by‘ the reference character 22, ’ substantially right angular relation to one an
which tapers fore and aft from its greatest ver
other and at the same time substantially normal
tical and horizontal dimensions, so that it may be to the surfaces of the=portions of the hull to
said to be substantially torpedo shapein a longi
tudinal direction of the hull. This so-called
bulbous portion may vary in cross section with
out departing from this inventiombut I prefer
ably make the same substantially in the shape
of a waterdrop, as shown in Figure 10, whereby
10 the superimposed portion of the hull is joined to
the bulbous keel portion 22 by a relatively thin
intervening submerged section 24' producing a
substantially hour glass section to form, at either
which they are fixed, so as to more effectually
support the shaft bearings. This arrangement
is made possible by the rugged bulbous portion
which is su?lcientlystrong to withstand the lat
eral thrust and constitutes in effect the back
bone of the ship at this point.
The bulbous keel portion 22 preferably extends
substantially to the stern post 25 which‘, instead
of being composed of assembled 'pieces ~of cast
~ side thereof, channels 24 which extend longi
tudinally of the hull. By virtue of the formation
of the superimposed structure and the underlying
iron of complex design and shape as heretofore,
may be conveniently formed, according to the 15
present invention as shown in Figure 7, with the
bulbous portion, these channels converge rear
wardly from their forward open ends to a point
of minimum dimension, indicated generally by
the region 23 in longitudinal ‘view, and aft of
20 this‘ region the channels ?are out rapidly so as
to produce, in each, a divergent-convergent lon
stern post carried around and anchored to the
aft end of the bulbous portion which constitutes
a firm anchorage therefor. The rudder 26 may
be mounted, as shown, within the confines of the 20
stern post and properly contoured in the usual
Another advantage of this stern post arrange
ment is that it ties together the aft end of the
bulbous portion and the extreme stern of the 25
outer half is removed. The propellers, shown as hull and assists in producing an efficacious rein
25 twin propellers, and indicated at I], are posi
forcement of the entire stern of the hull. It will
tioned in the region of minimum dimension of of course be understood that the stern post may
these channels and are so mounted, as illustrated be ‘shaped otherwise than as shown in Figure '7,
in Figures '7 and 10, as to project into and oper
but it preferably is carried well down to the keel 30
the channels.
and anchored to the bulbous portion 22 as stated.
30 ateItwithin
will thus be noted ‘that the hollowing out
When the hull is formed, as shown in Figures
and club-footing of the frames as stated pro
‘7-10, it will be noted that a mechanical result
duces the two convergent-divergent semichan
illustrated in the girder form of Figure 11, is
nels leading to and from the propellers and these produced as compared to the structure shown 35
function after themanner of nozzles for the
35 induction of water to the propellers and the in Figure 5. In Figure 11, the web 18’ of the
girder is deeper and in addition to the decks l9
discharge of water therefrom. In practice, the and 20, the web of the girder is provided at its
said channels smooth out the water streams and lower edge with additional lateral ?anges 21,
lead them to the propeller from a point below,‘ which are of appreciable width and indicate the 40
so as to permit the propellers to operate with
'40 the greatest efficiency and at the same time ‘ structural strength or reinforcement factor of
the bulbous part 22. This additional ?ange 21
gitudinal-contour, somewhat similar to a\longi-_
tudinally sectioned Venturi tube of which the
minimize the drag of surface water into the
propellers with resulting absorption of air bubbles
and fall of efficiency of propellers. In fact, it
is found that the propellers tend to suck the
45 water longitudinally of the channels and produce
a pronounced suction therein which materially
decreases resistance to the forward passage of
V the hull, while the water leaving the propellers
‘is discharged through a rapidly diverging space
This directed water flow
produces an increased reaction on the stern of
the hull and contributes to forward progression
of they ship. .Thus, instead of increasing the re
sistance to the movement of the ship, as has
50 directly to the rudder.
manifestly not onlylincreases the strength and
rigidity of the increased web height, but it also
very materially increases these factors in a lat
eral direction. In other words, it gives the ship
backbone in its aft end at the keel andpreciudes
lateral whip of this part of the ship and at the
same time reinforces the same against vertical,
vibration. This vibration is due to a great ex 50
tent upon the operation of the propellers as
stated, but when the streams of water fed to and
from the propellers are controlled as described,
this also minimizes vibration.
of directing water to the propellers, the structure
of the present invention decreases this resistance
considerably, so that I‘ am able to fullyutilize
It should be further noted that the bulbous 55
portion 22 results-in additional displacement 'well
below the waterline and consequently increased
buoyancy at this, point which, as shown in Fig
ures 7 and 8, is directly forward of the stern post
vthe increased efficiency of the propellers for the
or as far aft as possible. This I have found to
55 heretofore been the case with all known means
60 forward movement of the hull." -
By positioning the propellers above the bulbous
portion, so as to project into the channels, I fur
ther produce a condition particularly propitious
for the support of the outboard ends of the pro
peller shafts. Heretofore the outboard ends of
these tail shafts have been carried by propeller
struts forming parts of brackets which are rivet
ed exteriorly to the hull in depending position
and generally each comprises two V shaped arms
be of pronounced advantage. For example, in
conventional ship design for fast ships, there has
invariably been ‘a narrowing of theafter portion
with the object of decreasing the resistance to 65
forward motion; This naturally decreases the
buoyancy of this aft extremity, so that there is a
tendency of the ship to squat or lower in the
water; particularly when the ship is traveling at
high speeds. With the additional buoyancy how 70
ever ai’forded by the bulbous portion 22, this does
occur and the ship is, in contradistinction,
relatively acute‘ angle, as shown in Figure 4 'not
on a more even keel. ‘This holds good
at 28'. This‘ arrangement does not produce a
not only for a vessel traveling in smooth ,water,
rigid mounting. By reference to Figure 10, how
but also cutting through the seas in which'case 75
70 arranged in angular relation to one another at a
ever, it will be noted that the arms of the struts
the torpedo shaped bulbous formation acts as a
kind of anti-pitching device.
The showing of Figure 12 graphically illustrates
these distinctions _by comparison. In this figure,
A represents the graph of the areas of the cross
sections of the stern; this graph also represents,
on a suitable scale,‘ the graph of the displace
ments or the buoyancies of the corresponding
parts of the ship. The broken line P represents
10 the repartition of the weights along the ship, the
total areas delimited by graphs A and _P being
equal for the entire ship, because the displacement
of a ?oating body is equal to its weight. Finally
C is the graph of the loads which result from the
diil'erences of the ordinates of the graphs A and
P, the areas delimited by graph C representing
in each transversal part the local excesses of the
weight over the displacement, when they are lo
cated below the horizontal axis CY, and the local
20 excesses of the displacement over the weight,
when they are located above this axis. It can
be seen that at the extreme rear end of the ship
the weights overcome the buoyancy (hatched
area L, Figure 12), and, as these weights are lo
cated at a great distance from the middle of the
ship and therefore act on along arm of the lever,
they produce considerable pitching moments.
The bulbous protuberance in the shape of a tor-v
pedo, formed, in accordance with the invention
by the club-footing of the stern frames, oom
pensates for this excess of weight by increasing
the displacement and thus decreases the pitching
moments by the buoyancy oi’ the stem.
graph of the areas of the cross sections A, instead
35 of joining itself tangentially to axis OY, pro
duces an enlargement M, as represented by the
dot and dash line in Figure 12; the hatched area
K, located in this region between branch M and
the old graph A, must be equal or superior to the
40 hatched area L, representing the excesses of the
weights. Moreover, by utilizing the enlargement
or bulbous part 22 of the bow and the stern as a
water ballast chamber, it is possible to regulate,
at will, the weight of the stern part and thus the
45 trim of the ship.
The present invention is preferably built into
ships during the initial construction thereof, but
it may be also incorporated in old ships by re
moving the stem section of the hull and building
on a new section embodying the invention. This
new section may be so designed as to increase the '
length of the hull su?lciently to incorporate
thereinto- the present invention, although, if de
sired, more extensive portions of the aft section
of the hull may be remodeled, although this is
generally not desirable as it will materially in
crease the cost over and above that of the length
ening operation, which does not require appreci
able modi?cation of the remaining frames of the
The foregoing detailed description sets
forth the invention in its preferred practical
form, but the invention is to be understood as
fully commensurate with the appended claims.
‘"I‘apering" and “tapered", as used in the ap
pended claims, means a gradual diminution of
Having thus fully described the invention, what
I claim as new and desire to secure by Letters
Patent is:
1. A ship's hull provided aft of amidships and
forwardly oi’ the stern post with a bulbous keel
portion, a superimposed buoyant portion, and an
interposed upright portion of materially reduced‘
cross section having concave sides which merge
into the corresponding sides of the superimposed
portion in substantially tangential relation there
to, said bulbous keel portion tapering both' fore 30
and aft from a point intermediate its ends to
form, at both sides of said interposed portion‘,
convergent-divergent channels extending in a
fore and aft direction, propellers partially pro
jecting into said channels and juxtaposed sub->
stantially with the region of minimum cross sec
tion of said upright ‘portion, and a stern post,
the lower end of which is anchored to the aft
end of said bulbous keel portion in substantially
tangential relation thereto.
2. A ship's hull provided aft of amidships with 40
a bulbous keel portion tapering in fore and aft
directions, and a stern post anchored to the after
end of the bulbous keel portion and extending
rearwardly and upwardly in substantially tangen
tial relation to the keel.
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