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CATWALKER
Although this work took
place 10 years ago, it still serves as a good example of how
minor oversights can have a major impact.
The “CatWalker”
is a 30’ x 13’ aluminum asymmetric catamaran operated
in BC waters and is used for transport of personnel. The basic
stipulation for the vessel: 33 knot cruise in sea-state 3
with 12 passengers.
Several months after delivery and subsequent re-powering to
improve performance, J. Simpson Ltd was called in to address
several matters:
- The boat was very heavy.
- Even with twin 370 hp diesels,
performance was unsatisfactory with a top speed of about
35 knots.
- At any planing speed, the boat
was very wet with excessive spray being thrown in all
directions.
- At speeds over 23 knots the boat
had a tendency to ‘chine walk’. Heel could
go to port or starboard and would start with a gentle
5 degrees and quickly terminate to a violent 10 to 15
degrees. In some cases there was an indication that the
boat might broach to. At speed, this could lead to a very
rapid capsize.
The above ‘characteristics’
did little to instill confidence and were sufficient reason
for the operator to not accept the boat. The owner did start
some modifications that showed some promise but it was obvious
that this boat might need more than a quick fix.
After a thorough assessment
of the vessel and the problems, J. Simpson Ltd prepared some
drawings and guidance instructions. Among the changes, the
hull was extensively revised with sponsons and strakes added.
After the above changes
were made the boat had a top speed of 43.5 knots (50 mph)
and a cruise of 34 knots. The handling, while not perfect,
was vastly improved and more manageable: the operator was
no longer terrified.
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