IDI- PROVEMENTS IN THE CONSTRUCTION OF SHIPS' MASTS, YARDS, BOOMS, AND IN SPARS
Year: 1853

page_text: LETTERS PATENT to Robert McGavin, of Glasgow, in the County
. of Lanark, North Britain, Merchant, for the Invention of "IDI-
PROVEMENTS IN THE CONSTRUCTION OF SHIPS' MASTS, YARDS, BOOMS, AND
IN SPARS
Sealed the 29th September 1858, and dated the 31st March 1853.
PROVISIONAL SPECIFICATION left by the said Robert McGavin
at the Office of the Commissioners of Patents, with his Petition,
on the 31st March 1853.
I, ROBERT MGAVIN, of Glasgow, in the County of Lanark, North
Britain, Merchant, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE CONSTRUCTION OF SHIPS' MASTS, YARDS, BOOMS,
AND IN SPARS," to be as follows:-
This Invention relates to the so combining wrought iron and timber
in the construction of the masts and spars of ships, that great strength
may be secured, in combination with lightness. In building a mast or
spar on this principle, the core or main centre is made of malleable iron
of cruciformi transverse section, by taking one long plate of iron of a

page_text: breadth equal to the required diameter of the spar, and attaching two
other plates at right angles thereto, one on each side along the centre.
These two plates are each of half the breadth of the main single plate,
the attachment being effected by rolling a double angle on one edge of
each of the two narrow plates, so as to be able to rivet the whole
together.
The four spaces left between the plates are then filled in with pieces
of timber, glued up together with marine glue or other substance; and
the whole being hooped together, a light and strong structure is pro-
duced at an economical cost.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Robert McGavin, in the Great Seal Patent
Office, on the 29th September 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
ROBERT MCGAVIN, of Glasgow, in the County of Lanark, North Britain,
Merchant, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent; bearing date the Thirty-first day of March, in the year
of our Lord One thousand-eight hundred and fifty-three, in the sixteenth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Robert McGavin, Her special license that I,
the said Robert McGavin, my executors, administrators, and assigns, or
such others as I, the said Robert McGavin, my executors, administrators,
or 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 Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN THE CONSTRUCTION
OF SHIPS' MASTS, YARDS, BOOMS, AND IN SPARS," upon the condition
(amongst others) that I, the said Robert McGavin, by an instrument in
writing under my hand and scal, should particularly describe and ascer-
tain the nature of the said Invention, and in what manner the same

page_text: 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.
NOW KNOW YE, that I, the said Robert McGavin, do hereby de-
clare the nature of my said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by
the following statement, reference being had to the accompanying Draw-
ings, and to the letters and figures marked thereon, that is to say:
My said Invention relates to the so combining wrought iron and
timber in the construction of the masts and spars of ships, that great
strength may be secured, with economy in first cost, and a reduction in
weight and bulk. In building a mast or spar on this principle, the core
or main centre is made of malleable or wrought iron, of cruciform
transverse section, by taking one long plate of iron of a breadth equal
to the requirements of the intended spar, and attaching two other plates
at right angles thereto, one on each side, along the centre. These two
additional plates are each of half the breadth of the main single plate;
the attachment or combination being effected by rolling or shaping an
angle on one edge of each of the two narrow plates, so that the whole
can be riveted together. The four spaces thus left between the four
projecting edges or wings of the skeleton mast or spar are then filled
in with pieces of wood glued up together with marine glue or other
adhesive substance; and the whole being hooped round with malleable
iron hoops or rings, a light and strong structure is produced at a mode-
rate cost.
Figure 1, on my Sheet of Drawings is a side external elevation of a
portion of a ship's mast, constructed according to my improvements.
Figure 2, is a horizontal section of the same, corresponding. Figure 3,
is an elevation of the wrought-iron plate core, detached; and Figure 4,
is a cross section of the core, showing the separate parts, as in the act
of being put together in making the mast. Figure 5, is an external
elevation of a spar or "yard" of a ship, as made on the same principle;
and Figure 6, is a transverse section to correspond. Figure 7, is an
elevation of the skeleton core, detached, showing the increase in the
breadth of the metal plates towards the longitudinal centre of the spar,

page_text: as well as the superior thickness of the plates at the same part where
the greatest lateral strength is necessary. Figure 8, is an elevation,
and Figure 9, a section, of a mast or spar, shewing the manner of
applying additional plates of iron where great strength is required;
Figure 10, is an elevation of the iron skeleton of the same; and
Figure 11, is a section, shewing the pieces slightly separated. Figures
12, and 13, are an elevation and a section of the iron skeleton,
as constructed slightly different from the last-mentioned modification.
In constructing a mast in this way a long main central plate A, is first
rolled and prepared to suit the required dimensions of the mast, the
width of the metal being considerably less than the diameter of the
finished mast; B, B, are the two additional side pieces, necessary to
make up the intended cruciform section of this wrought-iron core.
Each of these pieces B, has an angle C, rolled along one edge, so that
when the two pieces are disposed on opposite sides of and at right
angles to the main plate A, rivets can be passed through the angle
pieces B, and through the main plate, along the centre line of the
latter, to combine the three pieces into one frame piece or core. The
four spaces or divisions D, are now filled up with wood E, so as to
form a mast of completely solid cross section. The wood so filled in
is not relied upon as a direct means of supporting strength, its essential
office being the filling up of the divisional spaces to form a solid mass,
and prevent the buckling of the plates of the core. For, as the pre-
sence of a solid body between each two divisional pieces or wings
A, B, prevents either of such wings from swerving out of its normal
plane, it follows that each plate A, B, is disposed in the best possible
manner to rect lateral strains; that is to say, all lateral strain is
directed through each plate, in a line parallel with the plane of
such plate where there is the greatest resisting depth of metal.
Hence, the filling-in wood may be in short small pieces, as, pro
vided the wood is sound, such short pieces; when well joined by
amarine glue or otherwise, so as to leave no objectionable openings
along their contact surfaces, are quite as efficient as longer ones.
Various means may be adopted for effecting the junction of the
constituent pieces of the wrought-iron core. For example, a double

page_text: angle or Tedge may be rolled or formed on the edge of each of the
side pieces, instead of the single angle or flange, which I have shownr
in Figures 1, to 7, on my sheet of drawings; or the pieces may be left
entirely without flanges, separate angle irons being riveted or attached
to one edge of each separate side piece, such angle, irons being then
riveted by their other free flange 'to the main plate, as represented in
Figures 12, and 13, on my sheet of drawings. Where very great strength
required the core of the mast or spar is constructed as represented
in Figures 8, to 12; the central plate A, having narrower plates F,
riveted to each side of it, together with the angled plates G, between
which the side plates B, are riveted.
In making the yard, Figures 5, 6, and 7, the longitudinal central
portions of the plates A, B, are made of a superior width, as at C, so
as the better to resist lateral strain; or, instead of this widening of the
metal, its thickness may be increased, as shewn by the gradual swell
D, E, either rolled in the plates, or made by the addition of separate
tapered pieces. It will be obvious to the practical man, that this
system of constructing masts and spars is suitable for a variety of
works, and especially for the, jibs of cranes, where a combined lon-
gitudinal and lateral resistance is required. The filling-in wood may
be made either to fill up the divisional spaces entirely or partially;
but, when filled up throughout, as in Figures 1, and 2, metal hoops H,
are passed upon the structure, to bind the whole well together.
Having now described and particularly ascertained the nature of my
said Invention, and the manner in which the same is or may be used,
or carried into effect, I may observe, in conclusion, that I do not
confine or restrict myself to the precise details or arrangements which
I have had occasion to describe or refer to, as many variations may be
made therefrom without deviating from the principles or main features
of my Invention; but what I consider to be novel and original, and
therefore claim as the Invention secured to me by the herein-before
in part recited Letters Patent, is,
First, the general arrangement and construction of ships masts,
yards, booms, and spars, as herein-before described.

page_text: Second, the system or mode of constructing masts and spars for
various uses, with a central malleable iron core.
Third, the application and use, in the construction of masts and
spars, for various uses, with metal cores or central pieces of cruciform
transverse section.
Fourth, the system or.mode, herein-before described, of constructing
masts and spars for various uses, wherein metal plates are so disposed
as to receive lateral strains in lines parallel with their planes of width..
In witness whereof, I, the said Robert McGavin, have hereunto
set my hand and seal, this Twentieth day of September, in the
year of our Lord One thousand eight hundred and fifty-three.
ROB MCGAVIN (S)