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W54 Mile Stone

Over the years we have experimented with various ship design CAD programs – at enormous cost. Some have been very good. Autoship™ is an industry standard. There are also now numerous lower cost programs available.

It became apparent over time that while some packages provided efficiency, productivity wise design work was no faster by computer than the drawing board.     

Many might find this difficult to believe. In reality 90 percent of design is thinking and research……. and arithmetic. The actual time to draft a drawing is little different by either means.

For the approx. 300 sheets of drawings required to build a vessel such as the W54 each takes on average three days to complete.

Drawing Board

Drafting on a drawing board has distinct advantages. The paper size, at A1, is larger than most computer screens. Also, it is possible to run a scale rule anywhere over the drawing and it can be “penciled” on. More important however is that a discussion group can form around a drawing board. This is typical when a client visits – in fact it is one of the satisfying experiences for a customer as it allows a casual involvement from the design stage.

A hand drawn plan by an experienced draftsman, often falls into that area considered art, something to be appreciated for more than just the information it contains.

While detailing the construction we are also planning how the vessel will be put together. The largest cost in boatbuilding is labour at around 50%. There are two options for containing man hours; a simple design or a well thought out procedure. The simple hull form such as a single chine with fine ends does not correlate with ocean going capability. Ours are well formed hull shapes to maximize seaworthiness and economy of travel. Our planning inevitably draws from modern ship building practices with sectional or modular construction. 

Drawing Board

The photos above show my brothers drawing board. It is quite old and worn. At a guess some 100 odd vessels have been drawn on it, from the smallest at 23ft to the largest vessel ever launched in New Zealand, all detailed in every respect.

We are not totally anachronistic and do rely on computers for a lot of our work. While the lines and construction are detailed by hand, these are handed on to one of two computer draftsmen we work with. One completes the lines fairing and 3D hull model and takes off the CNC structural cut files for parts and completes vessel hydrostatics.

3d cad

3D model fairing saves many weeks of lofting work where once we would lay down the lines of the vessel full size on a loft floor and from there take off a scrieve board from which to cut, manually, all the steel bulkheads frames and longitudinal pieces.

3d Hull

In this work the computer has saved many hours of effort and combined with the latest in CNC profile cutting provides accuracy in cut materials to .5mm. A consequence of this accuracy; which is pursued right through construction, is that productivity is higher.

The second draftsman uses the 3D model to complete the interior fit out detailing for shop drawings.

The drawing seen on the board above marks a milestone in the design of the W54; it is the last structural detail drawing. The completion of the hull and superstructure detailing confirms the General Arrangement drawing. As structural detailing has progressed this has required minor tweaking.

General Arrangement

General Arrangement

As can be seen there are two General Arrangements; one with a fly-bridge the other without.

The next update I will begin to explain the arrangement beginning with the wheelhouse and fly-bridge.

© T.C. Watson & Sons Ltd 2013

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