Improvements in and connected with the Hulls of Ships or Vessels, and in Means for Reducing the Skin-friction thereof.
Year: 1895

page_text: Date of Application, 13th Apr., 1895
Complete Specification Left, 13th Jan., 1896-Accepted, 15th Feb., 1896
PROVISIONAL SPECIFICATION.
Improvements in and connected with the Hulls of Ships or Vessels,
and in Means for Reducing the Skin-friction thereof.
1, JAMES ATKINSON, of Amherst, Fallowfield, Manchester, Engineer, do
hereby declare the nature of this invention to be as follows:-
This invention relates to the form of ships or vessels intended for high speeds,
more especially when driven by steam or other motive power.
Existing forms of vessels when driven at high speeds pile up a bow wave, up which
they are subsequently forced, the bow rising and the stern sinking. The object of
this invention is to prevent, so far as possible, the bow wave, and also to lift the
stern at high speeds.
The form of the vessel at and below the water line is constructed in such a manner,
that when at rest in still water the draught continuously and practically uniformly
increases from nothing at the bows, to its greatest depth at the stern, the floor of
the vessel being practically flat both in a fore and aft direction, and in a transverse
direction.
The sides of the vessel below the water line are vertical (more or less), and
the plan on the water line is such that at the bows the full width is attained, and
this beam continued practically parallel for about half, or more than half the
length, of the vessel; the after portion tapering towards the stern in the usual
manner.
Where the vertical sides meet the flat bottom, the corner may be slightly rounded,
and this cutting away of the corner increased towards the stern, more particularly
when a screw propeller, (or propellers), are used.
A suitable projecting bow is carried forward above the water iine, either flat on
the bottom or spoon shaped.
Instead of the floor of the vessel being quite flat in cross sections, it may be a
little rounded, or rise up from amidships towards the sides, more particularly in the
case of sailing vessels.
Slight ridges may be formed on the bottom running fore and aft, so as to prevent
any air which might get under the bows of the vessel, when driven at a high speed,
from escaping side ways. Such air spreading in a film and reducing skin friction.
In some instances air may be pumped or otherwise forced under the bottom of the
vessel for this purpose.
:
Dated this 11th dow of Anvil 1905
Improvements in and connected with the Hulls of Ships or Vessels,
and in Means for Reducing the Skin-friction thereof.
I, JAMES ATKINSON, late of Amherst, Fallowfield, Manchester, and now of The
Woodlands, Marple, Cheshire, Engineer, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This invention relates to the form of ships or vessels intended for high speeds
more especially when driven by steam or other motive power of ample amount.
[ Price 8d 1

page_text: Existing forms of vessels when driven at high speeds pile up a bow wave, up
which they are subsequently forced; the bow rising and the stern sinking. The
object of this invention is to prevent, so far as possible, the bow wave, to give a
tendency to the vessel to rise so that its actual displacement is less when running
at high speeds than when at rest and to reduce the skin-friction in a manner which
will be hereinafter explained.
The improved form of the vessel at and below the water line is such that when at
rest the draught, continuously and uniformly, or almost uniformly, increases from
nothing at the bows to its greatest depth at or near the stern, the floor of the vessel
being both in a fore and aft direction and in a transverse direction practically flat.
The sides of the vessel below the water line are vertical (more or less) and the plan
on the water line is such that at the bows the full width is attained and this beam
continued practically parallel for about half the length of the vessel, more or less,
according to the degree of fineness desired; the after portion tapering towards the
stern in the usual manner.
n
To enable this invention to be clearly understood I append a sheet of drawings
in which Figure 1 is a half plan, Figure 2 is an elevation, Figure 3 is an end view,.
showing various transverse sections and Figure 4 is an enlarged transverse section
of a portion of the floor of the vessel. Figure 3 is drawn to a scale of twice the
size of Figures 1 and 2.
The sections shown in Figure 3 are numbered in accordance with the numbered
dotted cross lines on Figures 1 and 2. They show the vertical sides running into
the flat floor with a slight rounding at the corners. This rounding is preferably
uniform until the after body lines begin to decrease the beam when it is gradually
increased. Also when screw propellers are used the cutting away due to this
increased rounding may be carried still further so as to allow free access of the
water to the propeller.
A suitable projecting bow is carried forward and also the after part may be flared
outwards above the water line so as to increase the deck space and give increased
fullness as shown.
It will be seen that the forward movement of the vessel teuds in the first instance
to displace the water downwards for the full width of the vessel, as however the
depth of the vessel increases only very gradually the equivalent of a very fine
entrance is obtained; also as the stern lines in plan may be commenced much earlier
than in an ordinary vessel a very fine run aft can easily be secured.
With an ordinary vessel driven at high speeds the water must be divided by the
bows and displaced; the power required to displace it increasing very rapidly as
the rate at which it has to be displaced increases and this is one of the chief causes
of the present practical limits to the speed of vessels. With the improved form, if
the water has not time to be displaced the vessel rises more or less, as much in fact
as may be necessary for its forward movement. The sides are made vertical so
that there is no tendency to draw the stern down.
I prefer to form slight ridges on the flat bottom running fore and aft as shown in
Figure 4 with the view of preventing any air escaping sidewise. With a vessel
driven at a very high speed some air may get shut in at the bows, also air may be
pumped or otherwise forced under the bottom, this air spreading in a film between
the bottom of the vessel and the water will materially reduce skin-friction.
this connection the upwards slope of the of the bottom of the vessel gives the air a
tendency to escape at the bows, whilst the forward movement of the vessel tends
to overrun the air, the combined result being favourable to the retention of
the air.
In
In some instances it may be necessary to have a small keel near the bows to
enable the vessel to keep a steady course in which case the projecting bow and
the lines of the entrance may be worked into this keel. Otherwise a sliding
keel may be fitted and used as occasion may require.
I wish it to be understood that this invention is only intended for vessels which

page_text: are to be driven at a very high rate of speed such as light full-powered steam.
ships.
It is not suitable for heavy cargo steamers.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. High speed ships or vessels driven by ample steam or other power so
constructed as to have a continuously and practically uniformly increasing draught
from nothing at the bows to a maximum near the stern; in plan, at the water line,
having the full beam carried practically parallel from the bows to about mid-length,
then tapering in the usual form to the stern, with vertical sides running into the
practically flat bottom with slight roundings increasing towards the stern, substan-
tially as described and illustrated.
2. In high speed ships or vessels similar to the type described in Claim I the
construction of ridges on the practically flat bottom running fore and aft for the
purpose of retaining air which may be shut in at the bows, pumped or otherwise
drawn or forced under the bottom, with a view to reduce skin-friction, substantially
as described and illustrated.
3. The general construction of high speed ships or vessels driven by ample power,.
substantially as described and illustrated.
Dated this 11th day of January 1896.