CERTAIN IMPROVEMENTS IN PROPELLING VESSELS
Year: 1855

page_text: LETTERS PATENT to Dean John Hoare, of No. 10, Salisbury Street, Strand,
in the County of Middlesex, Esquire, for the Invention of "CERTAIN
IMPROVEMENTS IN PROPELLING VESSELS."
Sealed the 3rd August 1855, and dated the 6th February 1855.
PROVISIONAL SPECIFICATION left by the said Deane John Hoare at
the Office of the Commissioners of Patents, with his Petition, on the
6th February 1855.
I, DEANE JOHN HOARE, of No. 10, Salisbury Street, Strand, in the County of
Middlesex, Esquire, do hereby declare the nature of the said Invention for
"CERTAIN IMPROVEMENTS IN PROPELLING VESSELS" to be as follows:-
My improvements consist in the novel arrangement of the screw propeller
in whatever part of the vessel the same may be placed, whether it be in the
stern, as ordinarily applied, or at the sides of a vessel in "the run," or
elsewhere.
Instead of working the screw propeller on a perfectly horizontal shaft, I
place my driving shaft at an angle inclining upward, at the inboard extremity
thereof, at such an angle as may be best suited to the conformation or build of
the vessel, and varying with the lines and displacement thereof. Upon the end

page_text: of the driving shaft may be affixed in the ordinary way any form of screw pro-
peller, and the blades of such screw will of course work at right angles with
the shaft, although they may be curved, to give the proper pitch and form for
propelling. By this means I obtain a better and more uniform resistance from
the water, have less slip or loss of power when at work; I can insert a screw of
larger diameter in the dead wood without weakening that part of the vessel; it
also permits of a stronger heel being formed to the rudder post. The angle of
the shaft will enable the engine to be applied directly to the end thereof more
conveniently than heretofore, and a short driving shaft only need be used; from
which circumstance, together with the angular arrangement of the shaft and
screw, the vibration and tremulous motion may be entirely prevented.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Dean John Hoare in the Great Seal Patent Office on the
6th August 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DEAN JOHN
HOARE, of No. 10, Salisbury Street, Strand, in the County of Middlesex,
Esquire, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixth day of February, in the year of our
Lord One thousand eight hundred and fifty-five, in the eighteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Dean John Hoare, Her special licence that I, the said
Dean John Hoare, my executors, administrators, and assigns, or such
others as I, the said Dean John Hoare, my executors, administrators,
and assigns, should at any time agree with, and no others, from time to
time and at all times thereafter during the term therein expressed, should
and lawfully might make, use, exercise, and vend, within the United King-
dom of Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "CERTAIN IMPROVEMENTS IN PROPELLING VESSELS," upon the
condition (amongst others) that I, the said Dean John Hoare, by an
instrument in writing under my hand and seal, should particularly describe
and ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after the date
of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said Dean John Hoare, do hereby declare
the nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement :-
Hitherto screw propellers have been fixed upon horizontal shafts working
parallel with the water line of the vessel; or, in the cases where screw shafts
may not have been laid down perfectly horizontal, they have been so fitted
to suit some peculiarity of construction of the vessel to which the propeller is
applied.
Now, my Invention consists in applying the screw propeller in all cases at an
angle; for example, when one screw is used in the dead wood of a ship, the
screw must be placed with its axis at such an angle as may be produced by
drawing a line from the centre of propulsion in the boss of screw along the
centre line of the keel up to the centre of gravity or motion in the vessel to
which the screw is applied, and inasmuch as this angle will vary in vessels
of different forms or models, and as the position of the screw shaft is seldom
the same, an unvarying angle cannot be defined for laying down the screw
shaft according to my Invention, but it must be fixed at an inclination or
angle suited to the form or build of the ship or vessel and the position of the
screw, and varying with the lines, model, and displacement thereof.
In the Sheet of Drawing hereunto annexed, I have shewn at Fig. 1 a
portion of the stern of a very long vessel of light draught, with a screw pro-
peller applied in the dead wood; but a long vessel of light draught is not the
best example in illustration of the feature of my Invention, for a short vessel
of considerable draught would illustrate it better; but, in the application shewn,
the angle of the screw shaft does not, on reference to the Drawing, appear as
striking or remarkable, although the inclination of the shaft, when it is prolonged
and contrasted with the line of keel, would more readily exhibit to the eye the
extent of divergence from the horizontal line; and I must here remark, that to
a certain extent the motion of the vessel through the water alters the line of
resistance to the screw. As a fast vessel, driven at a high speed in its passage
through the supporting fluid, will alter this line, say about one-half, therefore
the surface of resistance exposed to the screw is at a point about one-half the
angle made between a horizontal line, and one in a line with the shaft.
The advantages which I obtain
described are,
applying propellers in the manner I have
1st, the slip or loss of power is less, the water fulcrum for the screw being
better the further below the surface at which the screw can be applied without
mechanical disadvantage. By placing the screw shaft at an angle with the

page_text: water line the increase of power is considerable, the screw acting on the water
at right angles to the blades, or in a line with the shaft; and as the column
of water displaced by the screw points downward, and as the resisting medium
cannot give way or readily escape at the surface from the top blade, there is
less slip, and the power applied to drive the screw gives better results. The
effect of the alteration in the position of the screw, by giving an angle to the
driving shaft, would be understood by seamen as similar to a ship angling to
the wind with her square sails when she is forced ahead, although the wind is
"before the beam." Moreover, the advantage of placing the screw so as to act
upon deep water is illustrated by the trials of H. M. S. Duke of Wellington
and Agamemnon, and the French line of battle ship Napoléon, which ships
exhibited higher results with a smaller proportion of power, as compared with
vessels of less draught of water.
2dly, that sailing ships can be more readily converted into screw-propelled
vessels than heretofore, inasmuch as the angle of the opening to be made in
the dead wood better accords with the configuration or lines of the stern, and
the rudder post, keel, and stern frame, which can be made or left much stronger,
and better suited for carrying the propeller without straining.
3dly, the trunking and length of driving shaft in most cases need not be
nearly so long as at present, as the inboard extremity of the screw shaft rises off
the floor. The engine and connecting gear may be placed much nearer to the
stern and screw; a great advantage, desirable in every case.
4thly, the screw having a better grip, and acting more uniformly and directly
against a denser and more unyielding body of water, the vibration or tremulous
motion is materially reduced, and wear and tear to the vessel and machinery
is consequently thereby also reduced in proportion; and thus, in working the
screw according to my Invention, a considerable saving of steam power will
be effected, and an economy in the working expenses and cost for repairing
machinery and vessel.
5thly, from the screw shaft inclining upward inboard, the liability to leakage
through the stuffing box is reduced, and when the trunk is carried up to a
line level with or above the load water line, no damage can ensue from leakage
at the stuffing box.
6thly, from the diagonal position of the trunk less vertical depth is required,
and therefore a larger screw can be placed in vessels of small draught of water;
a great advantage in river and coasting navigation.
7thly, it may be placed in vessels with fine lines in the body of the after
section, as, from the downward action of the screw, no obstruction or loss is
caused by the dead water or wake. This will quite obviate all danger of the

page_text: screw being thrown out of the water in a sea way, as is now continually the
case in screw vessels of light draught of water.
Fig. 2 is an end view of a vessel fitted according to my Invention, but with
two three-blade screws; Fig. 3 is a side view of Fig. 2; Fig. 4 is an end view
of a vessel similarly fitted with two screws, one on each side aft the midship
portion of the vessel, angling outwards.
In witness whereof, I, the said Dean John Hoare, have hereunto set
my hand and seal, this Sixth day of August, in the year of our Lord
One thousand eight hundred and fifty-five.
Witness,
JOHN WILLIAM TIBBERT,
10, Salisbury St., Strand.
DEANE JOHN HOARE. (L.S.)