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PACIFIC CROSSING
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The
unit you see here is a direct drive mechanism with just two
moving surfaces - a bevel top and bottom - to turn the drive
through 90 degrees. With an 8:1 ratio, every revolution of
the cranks will turn the 14-inch diameter stainless steel
propeller 8 x. So at 50 rpm (revolutions per minute) on the
cranks the propeller will complete 400 rpm, moving the boat
through the water at an average speed of 2 knots – a
fast walking pace.
The
size and dimensions of the unit meant we had to chop a hole
through the keel and fabricate a stainless steel box to clamp
the unit in place and prevent water from pouring into the
boat. The advantage of having the unit in the middle of the
boat is ease of servicing or replacement in the event of mechanical
failure. If something goes wrong, we just pull the unit up,
replace failed parts or replace the whole unit with one of
two complete spares. No more dangerous operations under the
boat with a mask and snorkel in freezing cold water.
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An
unusual feature about this system, and one that is frequently questioned
by nautical types, is the efficiency of propelling the boat from
the middle rather than the stern. In practice we’ve found there
to be very little difference. If anything propelling from middle
is slightly more efficient because thrust is being directed along
the horizontal line rather at a slight upwards angle as with stern
propulsion. An added advantage for us was to be able to cut off
the skeg thereby reducing overall drag.
The unit was originally designed for use
in recreational pedal craft sold in the USA and Europe. The company
Micromarine that makes it kindly agreed to sponsor the expedition
with 3 x units customised specifically for our use. For more information,
look up www.micromarine.com
on the Internet, email sales@micromarine.com or call (1) 508 634
0269.
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back to THE
PEDAL BOAT
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