Building a Half Hull Model

In days of old boatbuilders would carve out a half hull model and show it to the client.  Once everyone agreed on the shape, the builder would take the lines off the model, loft it (see discussion of lofting here), and build the boat.  The half hull model was the starting point.  Nowadays, we have the lines already on paper, and we can use that to build a half hull model to represent the design of the boat in 3D.  Actually, we can model it in 3D on computers now, but sometimes one wants to do things the old-fashioned way.

First, take the lines drawing and using the copier, scale it to the size you want your model to be.  Now, plane your wood stock to the exact thickness of the waterline spacings in you lines drawing.  Accuracy is important here.  The next step is to cut out each of the waterline lifts from the half-breadth view, stack them up and glue them together.  This gives you a rough idea of the shape of the hull.

Take the glued together stack to the bandsaw and, cradling it in your hands, carefully cut the outline of the profile curves of the keel and deck.  This step can be intimidating, but just proceed cautiously and it will come out fine.  Don’t cut too close to the line.  You can clean it up later with planes, chisels, sandpaper, etc.

Now it’s time to start carving.  The aim is to knock off all the sharp corners of the lifts until you’re down to the inside of each lift joint.  It’s easier than it sounds, and quite fun.  Finish off with sandpaper, working through the various grits from 80 up to about 400.  Varnish, sand between each coat of varnish, and repeat.  I needed 5 coats to get the finish I wanted.

For those who are interested in more detail, there’s an excellent article in WoodenBoat Magazine, issue 182 on the process.