The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1892-03-14
iron and WOOD SHIPS.
Materials Used in shipbuilding and
Their Value. @ as +

| The Points in which Iron and Steel Are
Superior to Wood-Their Lightness
and Durability and the Comparative
Safety of All Kinds of Vessels.
The three materials used In the con-
struction of ships in general are wood
iron and steel. Wood has been in use
from time immemorial. Iron is only
about fifty years old, and steel is easily
within the memory of every man OF
moderate years. The Importance of the
three materials are inversely as stated
steel being the most valuable, then iron
and last wood. Noticeably is this so in
the construction OF swift steamships,
for wood is unsuited to the great engine
power nowadays put into ships; it can
not properly stand the strain.
Iron ships are superior to wooden ones
in the following particulars: Lightness
combined with strength, durability when
properly treated, ease and cheapness of
construction and repair and safety when
properly consI lcted and subdivided. In
wooden ship; IL has been found that
about one-hal Of the total weight of the
ship is required for the hull, whereas in
iron ships only from 80 to 40 per cent. of
the weight is thus taken up. For in
stance, in IA wooden ar1nored warship.
the weight oi the hull being so per cent
Of the displacement leaves 30 per cent.
for the weights to be carried. In an iron
armored warship the weight of the hull
is only 10 per cent, leaving so per cent.
for weights to be carried.
The tensile strength Of iron is from
40 900 pounds to so, 900 pounds per square
inch, and this strength can be secured
throughout all the metal used, so that
the material worked into the ship is uni
form and homogeneous. These are quail
ties wanting in wood; the greatest care
cannot eliminate such weak spots as are
due to the presence of knots, crossgrain,
hidden defects, etc. Generally good
sound timber may be said to have
strength to resist pulling apart (tensile
strength) of about 10, 900 pounds.
IRON FAR SUPERIOR TO WOOD.
When in shipbuilding it comes to
fastening pieces together, as, for in
stance, in making ships keel or her
deck beams, the weakness caused by
soaring the pieces of wood together be-
comes an element Of strength in riveting
the iron. No matter how it may be nee
esssary to treat the pieces of metal
whether by r1veting or welding or by
angle irons, the iron stands far above
the wood in resistance to tensile strains
It is only when resisting strains of COM
preston that there is tendency Of iron
plates to buckle, and this is guarded
against by making the plates thicker
than is required for other strains or by
reinforcing them.
Durability is quality of iron that is
not yet thoroughly determined. In gen.
eral, wooden ship may be said to last
about fifteen years. Some last longer
but there will be much patching and re-
newing to be done. The rules of Lloyds
allow about fourteen years as the aver
age durability of the best built timber
vessels
Iron is not subject to the internal
sources of decay to which wood is liable.
Worms and marine animals cannot in
jure it, nor will it rot from imperfect
ventilation. Neither can the parts work
loose from the motion and straining of
the ship, allowing water to get in and
cause decay. The danger to iron lies i'll
the rusting or corrosion, especially in
the under water parts-outside from the
sea water and inside from the, bilge
water. The only prevention is careful
watching, cleaning and painting, and
even with all this supervision galvanic
action is likely to do some damage.
Therefore the life of an iron ship is lin
tied, and in the present state of knowl
edge of the subject may be set down as
approximately thirty years, for. though
snip will last longer, extensive repairs
will have to be made that will cost con-
siderable money.
STEEL BETTER THAN IRON.
It is also easier to repair an iron Ship
since the necessary shape can be turned
out at once. The rapidity with which
an iron ship can be built counts for
much. In the present day the ease with
which iron is obtained and worked con-
stitutes another element of cheapness.
for the final cost today must amount to
nearly 25 per cent. less, especially when
the time, preparation, saving of weight
and life Of the ship are considered.
AS to the safety of ship when prop
erly constructed and subdivided, it is
only necessary to say that when the in
ternal space Of an iron ship is SUBJ
divided into many compartments by
longitudinal or transverse partitions
rising to sufficient height, or by hori-
zontal platforms, or inner skin, and all
such divisions are made water tight, then
that ship is safer than any wooden ship
would be against laundering, for the
space equired for these bulkheads can
not be found in timber built vessel.
The subject of steel may be briefly dis
cussed by remembering that steel is sim
ply superior kind of iron, and by viz
tue of lis greater strength is of lighter
weight. The strength of steel is from
10000 to 100000 pounds per square inch.
Steel is as strong lengthwise as it is
broadwise; iron is one-ffth stronger
Ienpthwisa than If is broadwise The