In response to Henry, I disagree that cats can not be more efficient at
displacement speeds. Hull fineness or beam to length ratio of the hulls is
definitely a factor at displacement speeds for a given length. Wave making
drag does affect displacement speeds. Mono hulls are pushing a wall of water
in front a max displacement speeds unless they are extremely narrow, usually
requiring more horsepower for a given speed then a high efficiency
displacement catamaran with narrow hulls. When you think of it a very narrow
displacement beach cat like the old Hobie 16, has very high theoretical hull
speeds in the displacement mode for a given length. The Manta 44 ,full gear
with half tanks, flat water routinely sees 8 knots burning 2 gal/hr or less.
Most trawlers in our size range would be hard pressed to do that, and with
much less cockpit, interior and deck space. Of course displacement is a
factor, I would say fully loaded the average Manta is pushing close to 30,000
lbs. Attached is a photo showing fuel consumption per engine, at 16.5 knots on
a Manta we recently launched with the 225 D-4 engines, carrying 200 gals of
fuel, the flow meter comes with the Volvo engines, based on some of our owners
calculations these meters are on the high side by over a 1 gal/hr of actual we
are still collecting data to confirm that. But the numbers in the photo are
pretty impressive as they are for a boat our size. A Grand Banks 44 would be
hard pressed to compete at any level of speed.
[demime 1.01d removed an attachment of type image/jpeg which had a name of PC 10.JPG]
In response to Henry, I disagree that cats can not be more efficient at
displacement speeds. Hull fineness or beam to length ratio of the hulls is
definitely a factor at displacement speeds for a given length. Wave making
drag does affect displacement speeds. Mono hulls are pushing a wall of water
in front a max displacement speeds unless they are extremely narrow, usually
requiring more horsepower for a given speed then a high efficiency
displacement catamaran with narrow hulls. When you think of it a very narrow
displacement beach cat like the old Hobie 16, has very high theoretical hull
speeds in the displacement mode for a given length. The Manta 44 ,full gear
with half tanks, flat water routinely sees 8 knots burning 2 gal/hr or less.
Most trawlers in our size range would be hard pressed to do that, and with
much less cockpit, interior and deck space. Of course displacement is a
factor, I would say fully loaded the average Manta is pushing close to 30,000
lbs. Attached is a photo showing fuel consumption per engine, at 16.5 knots on
a Manta we recently launched with the 225 D-4 engines, carrying 200 gals of
fuel, the flow meter comes with the Volvo engines, based on some of our owners
calculations these meters are on the high side by over a 1 gal/hr of actual we
are still collecting data to confirm that. But the numbers in the photo are
pretty impressive as they are for a boat our size. A Grand Banks 44 would be
hard pressed to compete at any level of speed.
[demime 1.01d removed an attachment of type image/jpeg which had a name of PC 10.JPG]
