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Solid shipbuilding

Say you want to build a yacht and, since you’re a competitive person, you want to be able to
gloat at Larry Ellison the next time you run into him in Cannes. That means your yacht
needs to be bigger and better than his — or, according to Wikipedia, have at least 82 rooms
on 5 levels (including a gym, wine cellar, private theater with a giant plasma screen), 3,300
square meters of teak deck, and a basketball court that can be used as a helipad. All of it
powered by diesel engines that give an output of 36,000 kW (50,000 hp) and four propellers
that enable your yacht to reach a cruising speed of 28 knots (just over 30 miles per hour).

How do you engage with a naval architect to begin the design? One word: hydrostatics.
Relatively boring, unsexy stuff that calculates bouyancy and stability, and allows the
designer to begin to assess how the vessel will trim, how efficient it will be to push her
through the water, how a helicopter landing will affect people sipping champagne in the
theater and many other factors. This information is also often used to provide a preliminary
estimate for the cost and timetable of construction.

It used to be true that much of the preliminary work in naval architecture was discarded once
the job was won, but this has changed as modern design tools were added to the traditional
toolkit. AVEVA (formerly Tribon) Marine, Intergraph’s SmartMarine and now Dassault
Systémes (DS) are working to smooth out the design process and enable the re-use of
earlier work in each step of the iterative design process. DS last week announced that its
business partner CENIT had released CENIT NAVAL ARCHITECT, a CATIA V5 add-on that
integrates hydrostatic and stability analysis into the CATIA solutions for yacht and ship

CENIT’s solution is based on the MAAT Hydro+ volume-based computation engine,
developed by Sistre. According to CENIT, MAAT Hydro+ is the first 3D hydrostatic
calculator based on the direct integration of water pressure fields on float faces. Traditional
hydrostatic calculations rely on a 2D representation of the Navier Stokes equations; modern
compute horsepower makes using 3D calculations possible. DS believes that, since 3D
solids modeling is the most efficient way to create accurate and reliable models, why waste
time and possibly compromise accuracy converting existing high level hull models into 2D

Getting back to our yacht design: The naval architect likely begins by adapting an existing
design that has proven to have many of the desired characteristics — say Ellison’s, if those
plans are available. She would then stretch the hull where needed, add an America’s
Cup-caliber keel or other complex configurations, make sure that there was enough volume
inside the hull for the desired number of rooms (and square footage of teak decking). Once a
first pass design was complete, she would then check the design’s seaworthiness by
running a hydrostatics analysis package. This used to be done by slicing the 3D hull at
points along its length (a process called "sectioning") and then running the hydrostatics
calculator on the resulting offsets. Obviously, by slicing at points along the hull, any
characteristic changes between those points is lost; starting with and sticking with the 3D
model for these calculations arguably gives a more accurate result.

Further, using CENIT NAVAL ARCHITECT, the designer can continuously update the
calculations, seeing in an instant the effect of any change to the hull. So say you change
the basketball court to a bowling alley, you may now have too much weight on one side of
the vessel — leading to a very unpleasant voyage that these tools can help avoid.

DS says that CENIT NAVAL ARCHITECT is already commercially available, that the 3D
solids-based calculations run on a standard laptop (a limiter used to be the compute cycles
needed for these calculations) and that pilot users report that the product is easy to learn
and easy to run. Anchors aweigh!

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