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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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