AN IMPROVED FORM OF STERN FRAME FOR SCREW STEAMERS
Year: 1883

page_text: LETTERS PATENT to Charles John Denham Christie of Tynemouth, in the
County of Northumberland, Iron Shipbuilder for an Invention of AN
IMPROVED FORM OF STERN FRAME FOR SCREW STEAMERS
PROVISIONAL SPECIFICATION left by the said Charles John Denham
Christie at the Office of the Commissioners of Patents on the 15th December
1883.
CHARLES JOHN DENHAM CHRISTIE, of Tynemouth in the County of
Northumberland, Iron Shipbuilder, "AN IMPROVED FORM OF STERN FRAME FOR
SCREW STEAMERS
"
"
My invention relates to an improved formation of the stern frames of screw
steamers in which the following advantages are combined, viz; a more simple form
of the forging, or of the casting (when of steel or other cast metal), lightness with
strength and better water lines at stern, giving a finer "run" to the propeller and
improving the steering, with increased strength of the vessel at stern portion.
According to my invention the forward post is curved aft from the
"boss"
(through which the propeller shaft projects) toward the rudder post at the keel
and toward the "transom " on rudder trunk (merging into the rudder post) at the
upper part, thus giving a better support to the "boss," carrying the propeller shaft,
and shortening the keel portion at foot of aperture while at the upper portion of
aperture the arched connection between the posts is avoided, the "frames" rest
upon the post, the "floors" and "transom " plates are of considerable size and
strength and the rivetting is much more easily and efficiently executed. The shell
plating is attached to the post by simple flanging, avoiding twisted plates, as in
one mode of construction, or "tuck" plates as in the other mode at present
adopted. The curved form of the forward post makes the aperture specially
adapted to receive the best form of propeller viz: that in which the blades are
thrown back. The forging of a stern frame made according to my invention is
very greatly simplified while a stronger frame, with less material, is obtained and
the structure of vessel at stern is greatly increased in strength,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles John Denham Christie in the Patent Office on the
14th June 1884.
CHARLES JOHN DENHAM CHRISTIE of Tynemouth in the County of
Northumberland Iron Shipbuilder AN IMPROVED FORM OF STERN FRAME FOR
SCREW STEAMERS;
"
My invention relates to an improved formation of the stern frames of screw
steamers in which the following advantages are combined namely; a more simple
form of the forging, or of the casting (when of steel or other cast metal) lightness
with strength and better water lines at stern, giving a finer "run to the propeller
and improving the steering, with increased strength of the vessel at stern portion
According to my invention the forward post is curved aft from the "boss"
(through which the propeller shaft projects) toward the rudder post at the keel,
and toward the "transom" at rudder trunk (merging into the rudder post) at the
upper part, thus giving a better support to the "boss," carrying the propeller shaft,
and shortening the keel portion at foot of aperture while at the upper portion of
aperture, the arched connection between the posts is avoided, the frames rest upon
the post, the "floors" and "transom " plates are of considerable size and strength
and the rivetting is much more easily and efficiently executed. The shell plating
is attached to the post by simple flanging, avoiding twisted plates as in one mode
of construction, or tuck" plates as in the other mode at present adopted. The
curved form of the forward post makes the aperture specially adapted to receive
the best form of propeller namely; that in which the blades are thrown back.
The forging of a stern frame made according to my invention is very greatly
simplified while a stronger frame, with less material, is obtained and the structure
of vessel at stern (always a weak part in large Ocean Steamers of great engine
power) is greatly increased in strength
"
The drawing accompanying this specification illustrates the form of a stern
franie made according to my invention and requires no further explanation to
shipbuilders or nautical men. It will be seen that the arched top of aperture is
entirely done away with the frames and "Hoors" resting on the forward post upon
which also the plating finishes in the same manner as at the bow on the "stern "
post by simple flanging without twisted or "tuck" plates. The forward post
curving backward to rudder post in lower portion of aperture avoids the long
straight connection at keel, between the two posts, while the aperture leaves ample
space for the working of propeller in a solid body of water.
Having now fully described and illustrated my invention I desire to have it
understood that what I consider novel and therefore claim as secured to me by
Letters Patent is:
The construction of the stern frames of Screw Steamers in such a form that the
forward post curves backward and merges into the rudder post at top and bottom
of aperture in order to obtain the advantages set forth substantially as shewn and
described
In witness whereof I the said Charles John Denham Christie have hereunto set
my hand and seal this thirteenth day of June in the year of Our Lord one thousand
eight hundred and eighty four
CHARLES JOHN DENHAM CHRISTIE (L.S.)