Feature 1 | AdvAnced Hullforms
soft motion the full speed range;
Asv monohull –
•
Safe and reliable platform;
arrangement of
•
Low draft and good manoeuvrability;
propulsors. and
•
Acceptable complexity and low
maintenance requirements
In the soft motion monohull, the air
cushion provides support for 70-90% of
operational displacement (having a large
cushion area). Planing/dynamic support
surfaces act around LCG (support
depending on speed). Buoyancy support
is located far from vessel’s centre line
(thus suppressing rolling motions).
soft motion Asv
In calm water, the air support ratio
monohull – bow.
increases to 80% plus, with reduced
wetted surface/resistance. Trim is neutral
to 1degree bow up. The air cushion flaps
and interceptors are set to reduce hull
resistance.
In waves more ventilation is
unavoidable, and the air volume flow
is increased. There is some bow-up
trim increase, set by air cushion flaps
and interceptor adjustments, and a
semi-SWATH (small waterplane area
twin hull) bow and flared chimes start to
act to dampened pitch motions.
The design has a sharp/flared bow
section, ending in a narrow bulbous
The challenge and the design goals
•
Improved comfort and ability to bow, giving increased waterline length.
for ASV soft motion monohull were, perform core duties onboard; It is complemented by wide lower
therefore:
•
Vessel to maintain high speed in spray rails. The bow hull ends in air
•
Reduced onboard accelerations and difficult conditions for size; cushion at a sharp angle – without
unpleasant motions/impacts in waves;
•
Improved range and load carrying planning surfaces supporting pitching
•
Active use of pressurised air for motion capability; motions. There is also an air fan with
damping;
•
Improved fuel efficiency throughout high volume flow and outlet to cushion
chamber in the bow.
The propulsion bodies house the
waterjet pick ups, and an ‘air groove’
reduces air ingestion into the waterjets.
The waterjets are widely separated, and a
ride control system is adopted.
The lift fans are of a new type, a
development of the centrifugal fan
concept offering improved performance
and efficiency with dual inlet – single
outlet high volume flow (almost 20m3/s)
and pressure up to 8kPa. They are built
from a strong and durable carbon-
fibre construction and are hydraulically
operated. Locating one of the fans far
forward ensures good filling of the
estimated hull resistance at 32, 35 and 38tonnes operational displacement compared with cushion even in extreme conditions.
conventional monohull. Compared with a monohull, Effect
14 Warship Technology October 2009
p13-15_WT ASV OCT09.indd 14 17/09/2009 16:55:01
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