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m) with a scale significant wave period of 5.8 sec-
onds. Sea state 5 is defined as having a scale sig-
nificant wave height of 8.0 – 12.0 ft. (2.4 – 3.65 m)
with a scale significant wave period of 8.25 sec-
In addition to all of these other features, the hull form pro-
duced has excellent stability characteristics in keeping with
a good roll period in a seaway and with sufficient range of
stability to make the vessel safe for long range ocean cruis-
ing. This hull not only exceeds the minimum requirements
of international authorities, it has a good, healthy range of
stability even in steep seas (Fig. 8, previous page).
Extensive studies were done on stability parameters and the
effects of hull and superstructure forms on the range of
positive righting arm. Every effort is made to keep weight
low in the vessel as the design develops. During the design
process as features are incorporated into the overall form
they are placed and planned to produce a good overall
movement of the center of buoyancy in relation to the cen-
ter of gravity. The resultant vessel has excellent stability
parameters without having to resort to anything more than
minor amounts of trimming ballast.
“Amnesia IV”
This is one of the first large fiberglass motoryachts to take
advantage of some of this technology. The vessel is 86 ft.
(26.2 m) long with a 23 ft. (7 m) beam and 6 ft. (1.83 m)
draft. With a single 1300-hp MAN diesel, a top speed of 15
knots has been attained. At 210,000 lbs. (95.3 tonnes)
displacement (half load), it is considered to be a medium-
weight vessel. It has a 7000-mile range at 9 knots on 6000
US gallons (22,680 liters) of fuel. As reported by the cap-
tain, on a trip from Vancouver, B.C. to San Diego, CA the
vessel easily averaged 9 knots in big seas and high winds,
burning less than a gallon per nautical mile in comfort
(including generator run time).
This vessel is an all-steel 76 ft. (23 m) ocean trawler with a
22 ft. (6.7 m) beam and a 6.5 ft. (2 m) draft. Fitted with
twin 330 hp diesels, the vessel has a top speed of 12 kn
At 225,000 lbs. (102 tonnes) displacement (half loaded)
is considered moderately heavy. It has a 3500 mile rang
at 9 knots on 3300 US gallons (12,500 liters) of fuel. Th
owner reported that on her first trip from Vancouver, B.C.
Mexico she easily averaged 9 knots in reasonable weath
Although the initial intention was not to cruise that fast, t
started out at that pace, found it comfortable and just ne
throttled back. They burned about 1 US gallon of fuel per
nautical mile including running the generator 3 hours per
The latest project was extensively tank tested at Vizon
Scitec Ocean Engineering at the University of British Colu
bia. Much of the data in this paper is taken from that tes
report. The Fox Sports 86 is an 85.75 ft. (26.14 m) long-
range sportfish with a 24.5 ft. (7.47 m) beam and 6.5 ft.
(1.98 m) draft. Built with a steel hull and fiberglass supe
structure, the vessel displaces 250,000 lbs. (113.66 tonn
half loaded. Twin 550 hp diesels will push it up to 15 kn
with a range of 7000 miles on 5500 US gallons (20,790
liters) of fuel.
Model runs for Fox 86
Both the wave train and resistance numbers were very g
for this hull and typical of this technology. Seakeeping
showed no water coming on deck and the bulb never co
pletely emerged from the water despite the shorter than
typical wave train tested.
Continued next p
Amnesia IV (Cape Scott)