ISHEEWOOD SHIPS

479

Et transverse bulkhead stiffened by horizontal angle bars, closely
spaced, and further supported by widely spaced heavy vertical stifEeners

F, sides of expansion trunk. The space between this longitudinal
bulkhead and the side of the ship is called the "summer" or side tank.

The trunkway, which extends the whole length of each tank, is
about 7 or 8 feet in height and must not exceed in width 60 per cent,
of the -vessel's breadth. »

The Isherwood system lends itself more readily to modifications
in structure to meet special requirements than the transverse system,
especially in offering economy in the work of construction, great longi-

Fig 79 —Isherwood Framing Cargo Vessel,
tudinal strength, convenience in subdividing the ship, and in providing
clear holds for cargo. The rules of the classification societies are sufii-
ciently flexible to allow of various modifications in the details of ship
construction so that combinations of transverse and longitudinal
framing; web frames, deep frames and ordinary frames; deep and shallow
stringers; rolled section beams and built beams; solid pillars, tubular pillars
and built pillars, etc., may be introduced into various parts of the
same ship. The longitudinal frames of Isherwood ships converge towards
the bow and stern and come too close together so that the transverse
system of framing is introduced at the ends.