Dixon Kemp style curves

Fri, Sep 1, 2023

Although most boat designers these days work in CAD software, some still work with pencil on paper and need to draw those sweet curves that make a set of boat plans worth dreaming over. You’ll start out sketching freehand, but when it comes time to firm up and commit to a line, it’s useful to have something rigid to run your pencil against. This might be a spline, a flexible batten of wood or acrylic, held in place by cast lead drafting ducks. Or it might be a curve template that you use to build up your line by tracing and connecting sections of the template.

The most ubiquitous curve template these days is the French curve, but for boat design many French curves are often poor fits for the swooping lines we’re trying to draw. The Copenhagen ship curves were once common and full sets can occasionally be seen for sale for hundreds of dollars. These were sets of 50-ish curves, some long sweeps that serve a similar purpose to a batten and some smaller curves that work for curves tighter than the flexibility of a good batten.

In 1881 the naval architect Dixon Kemp published his “Practical Boat Building for Amateurs”, where he described a set of “pear-shaped curves” that have come to be known as the Dixon Kemp curves, although his writing seems to indicate that these curves were widely used around him an not an invention of his own (Google Books). These curves work like the smaller radius Copenhagen curves to draw stems, rudders, and other tighter curves, in combination with a batten and a set of drafting ducks for the longer sweeps.

The Dixon Kemp curves have been occasionally manufactured, but like many tools for pencil and paper boat design, have not been available for many years. Recently I traced a set of them owned and used daily by yacht designer Paul Gartside and laser cut a set for my own use.

Since they haven’t been available for years, I might as well do a small batch production run for those few hardy souls who are still drawing boats by hand. If you’d like me to send you out a set, you can order them here: https://nixiemarine.square.site/product/dixon-kemp-style-curves/3