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Naval
Historical
Center #80-G-45671
A pontoon is a flotation device. Pontoons were
used on seaplanes in place
of
wheels to allow takeoff and landing from water. Portable pontoons
were
used in a bewildering variety of ways in applications ranging from
barges to small floating dry docks.
The U.S.
Navy's Seabees were equipped
with
a mass-produced prefabricated pontoon which, when assembled at an
advanced base, took the form of a 5' by 7' by 5' (1.5m by
2.1m by 1.5m) sheet metal box, weighing about 2600 pounds (1200
kg),
with fittings that allowed it to be filled with water, pumped dry
with
compressed air, and connected to other pontoons. This became the Lego of the
Pacific War.
Joined together in lengths of two units by up to 35 units, they
formed
a portable causeway that could be towed or ported by an LST. Assembled into a platform
three
units wide by seven long, it became a 50-ton barge, which could be
propelled by an outboard motor. 48 units could be assembled into a
small floating dry dock, capable of repairing small craft such as
PT boats. Pontoons
could
even be assembled into a stable base for a 40-ton crane. Like Marson mat, a pontoon
construct
could be quickly repaired by unlatching the damaged sections and
replacing them with new pontoons. Engineers constructed pontoon
causeways at Okinawa, the
largest of which was 1428' long with a pierhead 45' by 175'.
The design originated with Captain John Laycock of
the Navy's Construction Engineer Corps in 1940. However, it was
not
obvious how to produce a metal box with sufficient buoyancy and
strength at an affordable cost. Laycock experimented with cigar
boxes
and had a feasible design by February 1941. The first experimental
models and accompanying outboard motors were tested in the spring
of
1941, and British
observers
were so delighted that they ordered 3000 units at $700 each. By
1944
production had exceeded 10,000 a year.
References
Huie (1944)
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