Improvements in the Construction of the Hulls of Ironclads or other Vessels.
Year: 1889

page_text: Date of Application, 13th Aug., 1889
Complete Specification Left, 9th May, 1890-Accepted, 14th June, 1890
PROVISIONAL SPECIFICATION.
Improvements in the Construction of the Hulls of Ironclads or other
Vessels.
I, JAMES FREDERICK HODGETTS, of 39 Redcliffe Square, South Kensington, in the
County of Middlesex, late Professor of Nautics in the Royal Naval College of Prussia,
formerly of the Indian Navy, do hereby declare the nature of this invention to be as
follows:-
My invention relates to improvements in the construction of the hulls of ironclads
or other vessels, and is designed to provide increased resistance to submergence and
greater steadiness and stability in floatation, besides other advantages hereinafter
detailed.
Whereas the most ordinary form of sections of the hull of a vessel is round
bottomed or of a peg top shape, I have found by experiment that many advantages
accrue to a vessel, especially when required for fighting purposes, by forming the
bottom and bilge of the ship by means of a pair of catenarian curves concave to the
water instead of the usual convex bilge and springing from a central keel, dipping at
each of the outer extremities into side keels parallel to the centre keel and of about
the same depth.
This pair of curves present somewhat the appearance of a pair of extended wings
such as those of the albatross.
I have found that this particular form of bottom gives a practical grip to the vessel
of the bearing water, and thus tends to set in motion a large mass of water when the
vessel tends to roll. The inertia therefore of the gripped volume of water would
prevent rolling.
The outline of the hull in section is such by the concentration of protective armour
or packing that the transverse dimension or average beam of the hull is considerably
greatest at the water-line, the submerged portion receding back to the outermost keel
on either side, and the upper works also receding from the water line to the bulwarks,
presenting an inclined face to the impact of the enemy's shots, similar to the glacis
of a fort, and thus tending to deflect them, rather then offer a perpendicular opposing
face.
It has further been found from experiment that the special construction of the
bottom of the hull, as above described, confers a great increase of buoyance upon the
vessel as compared with its apparent external displacement.
This quality will therefore enable such a vessel to carry a greater excess of armour,
or heavy guns than is possible in ordinary designs; and such concave curvatures will
be a further guarantee of buoyancy after the external shell of the hull may have been
pierced.
Screws may be fitted to any of the said keels, either fore or aft, which, if say four
in number viz., two on each of the outside keels, will give extra assurance against
total disablement of all the propellers & will confer great self-steering advantages upon
the vessel.
The position of the propelling screws above described, will be such that they will
be situated on the quarters and near the bows of the vessel and would be thus
protected by the overhanging bow and quarters of the said vessel.
1000
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in the Construction of the Hulls of Ironclads or other
Vessels.
1, JAMES FREDERICK HODGETTS of 39, Redcliffe Square, South Kensington, in the
County of Middlesex, late Professor of Nautics, in the Royal Naval College of Prussia,
formerly of the Indian Navy 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 :-
My invention relates to improvements in the construction of the hulls of ironclads
or other vessels and is designed to provide increased resistance to submergence and
greater steadiness and stability in floatation besides other advantages hereinafter
detailed.
Whereas the most ordinary form of sections of the hull of a vessel is round
bottomed or of a peg top shape I have found by experimental trials that many advan-
tages accrue to a vessel, especially when required for fighting purposes, by forming
the bottom and bilge of the ship by means of a pair of catenarian curves concave to
the water (instead of the usual convex bilge) and springing from a central keel,
dipping at each of the outer extremities into side keels, parallel to the centre keel, and
of about the same depth.
This pair of curves present somewhat the appearance of a pair of extended wings
such as those of the albatross and although I specify these curves to be of the
character of reverse catenarian curves, for convenient geometrical definition, similar
curves may be employed, that is to say any curve which springs from the central
keel with an easy curve of sinall curvature and dips suddenly with a terminal curve
of increased curvature running nearly vertically into the side keels, and such curves
being approximately similar to a catenary curve though not an exact catenary in a
strictly geometrical sense may be used according to my invention.
I have found that this particular form of bottom gives a practical grip to the
vessel of the bearing water and thus tends to set in motion a large mass of water
when the vessel tends to roll.
The inertia therefore of the gripped volume of water would tend largely to check
rolling.
The outline of the hull in section is such that the transverse dimension or average
beam of the hull is considerably greatest at the water-line, the submerged portion
receding back to the outermost keel on either side and the upper works also receding
from the water line to the bulwarks and when protective armour is employed an
inclined surface is presented to the impact of projectiles and thus tends to deflect
them.
It has further been found from experimental trials that the special construction of
the bottom of the hull, as above described and with which may be combined spaces
or pockets, containing and retaining air, confers a great increase of buoyancy upon
the vessel as compared with its apparent external displacement.
This quality will therefore enable such a vessel to carry a greater weight of
armour and heavier guns than is possible in ordinary bulls of ships of like tonnage,
again my concave construction will provide an element of buoyancy after the external
shell of the hull may have been pierced.
Screws may be fitted to any of the said keels either fore or aft which, if say
four in number, viz. two on each of the outside keels, will give extra assurance
against total disablement of all propellers, and will confer great advantages upon
the vessel, as regards steering.
The position of the propelling screws above described will be such that they will
be situated on the quarter and near the bows of the vessel and would be thus
protected by the overhanging bow and quarters of the said vessel.
And in order that my invention may be the better understood I now proceed to

page_text: describe the same, reference being had to the drawings herewith and to the letters
and figures marked thereon.
Figure 1 is a half section of my improved vessel at amidships showing the
particular outline of the vessel at this point and showing at one side outline sections
towards the bow, and in the other outline sections towards the stern.
Figure 2 is a profile view of my improved vessel showing how and where the
concave arches gradually merge into the central keel at the stein and stern.
A is the central keel of the vessel from which spring on each side of it the curved
arches B B of a catenary or equivalent form the arches B B terminating in the side
keels c c.
The sides of the ship are formed of a glacis shape as shown at D D, the face of
such glacis being covered by armour.
The interior of the vessel is divided into water-tight compartments. The pro-
pellers are shown in convenient positions at E.
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
1st. The construction of the hull of a vessel with the bottom and bilge formed
by a pair of curves, such as reverse catenarian curves, concave to the water and
springing from a central keel with a curve of small curvature and dipping at their
outer extremities with curves of much greater curvature to side keels parallel to the
central keel, substantially as described.
2nd. The construction of the hull of a vessel so that its general conformation and
sections will correspond substantially with those shown in Figures 1 and 2.
Dated this 9th day of May 1890.
FELL & WILDING,
1, Queen Victoria Street, E.C., Agents for the Applicant.