MIL-HDBK-1025/5
Lift slips.
d)
Marine railways.
e)
Mobile cranes.
f)
Overhead rail launchers.
g)
Stiff-leg derricks.
h)
Straddle-truck boat hoist.
i)
Vertical-lift platforms.
j)
2.6.5.2 General Characteristics.
Davits are for smaller craft and lack the versatility of other
a)
launching devices.
b)
Marine railways entail high cost and waste of space, and lack versatility.
versatility.
c) Mobile cranes, either truck-mounted or crawler-mounted, are
justifiable only where used in conjunction with some ancillary operation
requiring this equipment.
d)
Vertical-lift platforms are used mainly for craft larger than
25 tons.
2.6.5.3 Functional Characteristics of Different Types
Forklift truck has a fork ladder with the capability of
a)
hyperextending down over a bulkhead wall to the depth required to place the
forks under the hull of a floating boat. Forklifts are best suited for small-
craft harbor basins with small water level fluctuation.
Jib-boom cranes have relatively short reach of the boom and
b)
are geared to a slower operation.
Three types of lift ships are in use:
c)
1) The elevating work slip that raises the boat out of the
water so that the hull may be washed or minor damages to hulls, rudders and
screws repaired. The boat remains on a cradle or in a sling in raised
position above the water only until the operation is completed.
2) A pair of hoists that remains as part of the berthing
facility holds the craft above the water while not in use.
3) A fixed-framework hoist that will allow the waves to pass
through the supporting legs without overturning. It is used for berthing
sites along large lakes or bay shores that cannot be protected easily against
wave action.
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