Idaho semi-weekly world., 1893-12-05
IRON AND WOOD SHIPS
MATERIALS USED IN sHIpeulLpINc
AND THEIR VALUE.

S@soty OF All Ainds OF Vessels.
The three materials used in the cop
struction Of ships in general are wood
Iron and steel. Wood has been in uec
from time immeinorial 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
ana last wood. Noticeably Is this SO in
the construction OF swift steamshinn
Tor wood is unsuited to the great engine
power nowadays put into ships; II 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. IL
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 30 to 4O per cent. Of
the weight is thus taken up. For in.
stance, in q wooden armored warsbjp
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 hull
is only 40 per cont. leaving 60 per cent.
for weights to be carried.
The tensile strength Of iron is from
10000 pounds to q. 900 pounds per square
inch, and this strength can be secured
throughout all the metal used, 80 that
the material worked into the ship is mi.
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 abont 10000 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
scarfing 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 rlveting or welding or 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 a 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 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
a ship will last longer extensive repairs
will have to be made that will cost con
siderable money
STEEL BETTER THAN IRON
1t 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 % 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 sub
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 required 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 vir
tue Of its greater strength is of lighter
weight The strength of steel is from
10000 to 1000 pounds per square inch
Steel is as strong lengthwise rs it is
broadwise; iron is one-fifth stronger
lengthwise than it is broadwise. The
elastic limit of steel is about 25 per
cent. greater than that of iron. SO steel
may be trusted with working loads
nearly % per cent. greater than the 9th
er material Lloyds estimate that by
building ships of steel there is "a saving
in weight over iron of about l5 per cent
or. to put the same thing in another
way. steel ship of the same dimensions
as an iron ship would have an increased
cargo capacity in weighD of some Is or
20 per cent.
In the matter of cost, steel ia more ex
pensive at first, but the best proof Of its
ultimate cheapness is found in the in
6isDuta blp fact that mOdarn marchant