The Dalles daily chronicle. [volume] (The Dalles, Or.) 1890-1948, 1892-06-29
IRON AID WOOD SHIPS
MATERIALS USED IN sHlPsuiLDlNe
AND THEIR VALUE.

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 inyersely 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 constructed and subdivided. In
wooden ships it has been found that
about one-half of the total weight of the
ship Is required for the hull, whereas in
iron ships only from 80 to 20 per cent of
the weight is thus taken up. For in
stance, in a wooden armored warship
the weight of the hull being so per cent
of the displacement leaves so per cent.
for the weights to be carried In an iron
armored warship the weight of the huh
is only 40 per cent, leaving go per cent
for weights to be carried.
The tensile strength of iron is from
10000 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 a
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 a ships keel or her
deck beams, the weakness caused by
scarfng the pieces of wood together be-
comes an element of strength in riveting
the iron. No matter how it may be nec-
esssary to treat the pieces of metal,
whether by riveting or welding OF by
angle irons, the iron stands far above
the wood IN resistance to tensile strains.
1t 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 a 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 win 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 in
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
ship will last longer, extensive repairs
viii have to be made that will cost con-
siderable money.
STEEL BETTER THAN IRON.