Improvements in Screw Steamships.
Year: 1891

page_text: Date of Application, 3rd Mar., 1891-Accepted, 2nd May, 1891
LEV
COMPLETE SPECIFICATION.
Improvements in Screw Steamships.
37ER
I, CHARLES HARRIS, of Number Fifty Clifton Street, Brighton, in the
County of Sussex, out of business or employ, 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 :-
Sheet represents the longitudinal section, and deck plan, of a small vessel
seventy six feet in length, overall, by twelve feet six. inches beam, amid, with a
moulded depth of nine feet; having, for the first improvement, a central outward
bulge, just above the water line, designed to ensure greater immunity from excessive
rolling than is usually experienced in this class of steamship. The principle upon
which this bulge line is arrived at may be thus described:-Having laid down the
outline of an ordinary deck plan, as indicated by the line A. A, a start is made, in
the bows, from the centre of the section C, and also from the centre of V, astern;
from these points are drawn two lines B B,-segments of the arc of a circle whose
radius is about equal to the extreme length of the ship, which widen apart until
they reach the maximum spread of the bulge previously determined upon by the
designer, in this case one foot six inches beyond the outside of the deck line amid. In
the plan the bulge is shown of an ovoidal, or egg-shaped form; but, if the sides of the
vessel whereto this principle is being adapted run parallel with each other for any
distance amid, it will be advisable to let the bulge line follow the same contour. The
bulge line may commence, within board, at any sites the designer pleases, and may also
extend from stem to stern if preferred. In the longitudinal section, (the uppermost
drawing on Sheet 1,) the graduating level of the bulge line B B is shown, as it rises fore
and aft with the lines of the ship; this line therefore, where it intersects the vertical
lines CD &c. to V, indicates the exact level of the maximum bulge at each and
every one of such vertical sections.
It will be noted that the curve of the bulge, on the longitudinal section, follows
a similar shape to the curve on the plan, aud this rule should obtain in all cases of
building on this principle. The designer, when planning this line, will need to
have carefully before him the length, breadth, and depth of his vessel, taken in
conjunction with her estimated draught, because the lowest parts of the bulge
amid, between K and O, should always be just above, or at least about on a level
with the water line. This bulge line principle is, in its application, obviously
capable of manifold variations, affording wide scope for the taste and judgment of
naval architects, and engineers.
Sheet 2 depicts the vertical sections of the same vessel, from the stem at C, to J ;
and stern P, to V; while Sheet 3 gives the central sections K, L, M, N, O, these
being represented in duplicate according as the ship is designed for single or
twin-screws.
Although these sections are shown entire, by way of better illustration, it cannot
be too strongly impressed upon the reader, that, below the limit of the bulge level,
every builder is free to follow his own bent, and moreover even the boundary limit
of the bulge line he defines for himself, thus himself fixing his own confine. One
other point however the designer must not overlook,-that the sections J and P
have to meet and blend with K and O; and these last named, together with L, M,
and N, as a reference to Sheet 3 will show, cannot be materially altered save in
the accidents of breadth and depth, as their form is an integral part of the second
improvement whereof the invention consists, and it is by their aid and shape that
the centralised location of the propellers is advantageously perfected.
Attention is directed to the circumstance that nearly half the wash of water from
the revolving screws will escape at once at the sides of the ship between L and N ;

page_text: of the remaining portion a small part will continue escaping between N and O,---
or, when reversing, L and K,-while the remainder will be thrown down the sloped
cavities provided for that purpose, and that consequently no part of the back-wash
is thrown against the ship. These currents, uniting themselves to that already
flowing by the ship's sides from the cutwater, all of which must re-unite at the 5
stern, will, it is believed, tend to an acceleration of speed, assisting as they do in
the vessel's propulsion, instead of being cast uselessly away in the wake of the ship.
In vessels of large size and great length, and where excess of speed is the great
desideratum, the number of propellers may be duplicated, or even triplicated, being
placed behind each other at suitable distances apart, eacli propeller in its own
separate sloped cavity, constructed in the form already described in this Specifi-
cation; this end is attained by duplicating, or triplicating, sections K, L, M, N, O.
Lastly, this style of build will adapt itself, in an especial degree, to double ended
boats, stem & stern alike.
The advantages claimed for this invention are:-
1. Diminished rolling, by reason of:-
(a) The central bulge acting as a counter-balancing weight on either side.
(b) The increased stability caused by the cubical feet of displacement, and the
superficial area covered thereby, being both greater than the cubical feet of
stowage, or area, contained in the superimposed space above.
2. The shortening of the propeller shaft thus reducing friction area,—dead ·
weight, and cost of construction.
3. The double bearing for the propeller shaft, at L and N.
4. Lessened vibration, by reason of:-
(a) The shortened shaft, and,
(4) Its dual bearing conducing to greater firmness.
5. Adaptability of engines to both ends of propeller shaft.
6. The screw propellers, surrounded as they are, in their central position, by the
improved shape of hull, are safe-guarded against external injury, fouling &c.
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7. Continuous action of propellers in a heavy sea, i.e. not lifted out of water when 3
pitching, as is often the case with stern screws.
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. The central outward bulge, as hereinbefore described.
2. The centralised location of the propellers, including the double bearing for the
shaft, and the adaptability of engines to both ends of the said shaft, as designed by
the shape of sections K, L, M, N, O.
3. As it is evident that my invention is to be carried out with various linear
modifications, I also claim any such general construction, or arrangement, of the
several parts, or sections, which constitute my invention, as heretofore described in
this Specification, and shown on the drawings.
Dated this Second day of March 1891.
3
CHARLES HARRIS,.
Applicant.