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Rafts
Rafts
permit the transportation of large loads on slow moving natural waterways.
The Chinese bamboo raft shown in the top sketch illustrates two propulsion
modes being used in concert. A tow rope to a person in the water or on the
shore permits the raft to be towed, with the resistance increasing as the square
of the speed. The other on-board crew member is using a pole to punt the
raft forward and to control its lateral motion.
The lower photograph
shows a contemporary inflated-skin raft in Pakistan. The skins are held in place
by a lashed pole "deck" and the raft is propelled using oars held
in vertical struts at the bow for oarlocks. A vessel of this size may be
able to carry loads of about 500 kg. Inflation of the skins stabilizes the
hull of the raft.
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