US NAVY'S - Incat

Water Resistance:
Keeping your underwater hull coating in good
condition will decrease resistance through
the water. This can be achieved by correct
application and maintenance of the coating
at dry dock and also by removal of any
underwater growth from time to time by using
underwater scrubbing machines. SpeedOne
was recently scrubbed mid season by Burgess
Engineering Divers during a night layover and
gained circa 1 knot in speed. Shall we call
that a 3% fuel saving between a dirty and a
clean hull
Routing:
Correct routing can achieve fuel savings by:
• Routing through the optimum depth of
water. Shallow water is generally faster for
an HSC and the extra speed gained may
more than offset a slightly longer route.
• Avoiding or taking advantage of local
tidal streams or areas of greater flow rates.
Change your route to one appropriate for
the tide.
• Otherwise, taking the most direct safe route.
Save an average of half a mile on a 50 mile
route and that’s a 1% fuel saving.
Engine Power:
Depending on schedule constraints the
optimum speed for fuel economy has been
found to be just above normal hump speed.
After pushing through hump speed engine
power can then be reduced to the minimum
required to maintain the speed and this is further
adjusted to allow for the positive and negative
effects of different depths of water. In general,
shallow water, provided it is entered at above 28
knots, will have a positive effect on SpeedOne’s
water speed and deep water will also help
when at lower craft speeds. Careful monitoring
and regular adjustment is of course required.
Note that a fantastic by-product of running at
reduced power is of course reduced engine
wear/stress, in itself a saving.
Finally, in rough weather, particularly with a
quarter or following sea, manual steering is
far more efficient for directional stability than
the autopilot system, which tends to overwork,
chasing the yawing of the vessel caused by
the following seas. In these situations, careful
application of manual helm ultimately results
in fuel savings, by achieving a straighter course
and less application of helm reducing drag.
Adding all of the above together, savings of 10%
have recently been achieved at SpeedFerries
from consumption in 2005. Potential savings
could also be achieved by additional
investment in fitting a better autopilot such
as an adaptive type and / or fitting fuel
consumption meters to give the Master a realtime
readout of economy. Previously these
were cost prohibitive but may now be worth the
investment.
Fast Ferry Benefits
How Fast Ferries Rank: Shipping produces fewer greenhouse
gases per tonne-mile than other forms of transport, as ships need relatively
little energy to push huge loads through the water that supports them.
Some large ships are more responsible than others for a significant
percentage of worldwide emissions of nitrogen oxides, particulate matter,
sulphur, air toxics and greenhouse gases. These ships are increasing in number and size, while
the residual heavy fuel oil they use is degrading in quality.
High speed ships, currently burning significantly cleaner Marine Gas Oil, are already part of the
solution in the task of reducing emissions of carbon dioxide.
Incat THE Magazine Issue 36 23