Developing hull plates

A few years ago I found myself in a new job, in the drawing office of a boatyard (again) but for the first time in an aluminium boatyard. I had just spent a couple of years in the drawing office of a composite boatyard, and had to improve my modelling skills to work with the geometry. Solid modelling programs work easiest with primitives, and to be able to work properly around the freeform nature of the hull and coachroof was a learning curve.

I was feeling pretty confident in my modelling skills when I arrived at the aluminium yard, but quickly found out that modelling up hull plates that would unfold successfully required a whole new workflow and skill-set. I was working in Inventor, which proved to be the right software for the job, but it is extremely strict, even the smallest error would mean that the plate would not unfold.

The next two years were something of a trial by fire, as I needed to produce flat pattern cut files for a variety of sheet metal hulls. These ranged from 4.3m ‘tinnys’ to 7.5m cathedral hulls, to a 14m catamaran. And of course in order to model up any frames or longitudinals I would have to get the hull plates spot on, in order to reference an accurate inside surface.

I came up with a workflow that I was confident from the outset Inventor would accept. and when it worked on the cathedral hull, I knew I was on the right track. And there is nothing better than having the confidence that my flat patterns are going to form correctly by the boilermakers on the floor. And that all the corner-to-corner or other plate intersections will be spot on, with no overlaps or interference.

And of course thanks to Inventors associative drawing environment, all flat pattern drawings are automatically updated to any changes to the 3d model, ensuring that all cut files are the latest revision. As long as there are no scaling issues a simple DXF export is all that is needed. I have used external nesting and toolpath software in the past, but have yet to try the associative nesting plug-in that is now available from Autodesk. Needless to say I am looking forward to my next hull modelling job, as these are some of my favourite jobs to do.

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