40-50 Ft Catamaran build

… And what about disinging your ship yourself? That’s something Delftship was imagined for. 😉

I remember I downloaded a Lagoon model from the Delftship website. Try to find it and scale down its size. B)

This is an ambitious project.

I believe you need to generate an indicative budget, of both your construction time and effort, plus the purchases, for the project. A building site is also important. The rule of thirds (structure, outfit, propulsion) should be reasonably applicable for such a boat.

After this you should assess your intended use of the vessel, and where it will be kept. These are both significant commitments of resources.

You may well get some frights here.

I have recently generated DELFTship models for 2 GRP Leisurecat power catamarans – see website

http://www.leisurecat.com.au

The first was for a 9 m existing boat, to support generating stability particulars for commercial operation. Shape was lifted off the existing hull.

The second vessel was a newbuild high speed 15 m commercial fishing boat. The shape was lifted off the existing 12 m mould, and extended to suit. This shape was then used to support some design investigations, and to generate arrangement and structural drawings. This boat is shown (4 outboards) on

http://www.leisurecat.com.au/product-category/some-extended-models

For this vessel I generated an IGES surface in DS, put it into Solidworks, and built the hull, etc from the surface. (It has taken me years to get to this capability.)

Neither project involved building the hull shape defined by the DS model.

I can make these hull shapes available. (File for 9 m boat attached.)

Now to consider construction methods. This comes in part from some investigations in support of a website design.

Traditional ply S&G is limited to fairly light and small boats – cartop and light trailable. A major limitation is that the ply has to be fairly thin – say 6 mm or so – to allow it to be bent up into hull shape. A second limitation is that framing up (transverse frames and/or stringers) isn’t very easy inside a S&G shell.

Another issue is that chine strakes, longitudinal steps and knuckles, spray strips etc can soak up a lot of effort.

One common solution is to build the hull in ali plate, which can be rolled or pressed close to shape.

There are a number of solutions to building a one off boat in GRP without the traditional mould (great for multi-boat programs). However, many of these bring in the labour intensive requirement to finish the “as laid” exterior surface to fair and smooth.

DS is well suited to designing hulls for cutting panels from the flat, and bending and joining to hull shape. Whilst it does analyse and display “developable” surfaces, I have yet to find an easy way of generating the hull panels as fully developable.

A suggestion here is that you consider designing and building a small trailable catamaran, using the construction technique you intend for your dream boat. Look to existing designs to give you some starting points for your designs. The sooner you start on your design spirals (function, size, layout, shape, weights, costs etc) the better. Your dreams have opened up a very interesting topic

Peter Edmonds
Naval Architect
Perth, Western Australia