Radio controlled motor launch, based on plans of a 1926 motor launch by John Hacker. A 25 feet motor boat originally with a 150 HP engine, scaled to 723 mm long for printing in six sections. Requires 140W motor (2830 750Kv brushless), 1.8Ah 3S battery and low profile servo for the rudder. With this power it manages to plane at what looks like scale speed. On the water: https://vimeo.com/251072600
It would be possible but tricky to re-scale, many Openscad scripts ended up being hard-coded to the scaled size. Important variables are at the top of scripts but precedence isn't necessarily sensible.
Thingiverse doesn't allow upload of all the file types. The ribs/stations and keel line were traced using minimal free plans available. X-splines (taken from a mathematical manuscript) were then used to make them continuous. They were then converted into a solid 3D object using a custom written gawk script. The continuous rib+keel points were used to make more continuous curves from bow to stern. These were then stitched together to make an initial solid hull shape that had many more polygons than necessary but faithfully reproduced the hull shape. The full build description and all the original scripts and sources are at http://abatis.org.uk/boatpage/ (my project page).
So far it has been out on the water on four days, various rudder sizes and propeller sizes have been tested. With this power combiniation it is about as fast as it can be. I can also conclude it contains no major design flaws, the only recommendation is to print it lighter than 3 perimeters.
This is a complex build, many parts, each with different printing requirements. It was all printed within a 20cm x 20cm x 18cm build space with a 0.4mm nozzle. 3 perimeters for the hull makes it a little heavy, I recommend trying a test print of 1 perimeter just to see how light you can make it on your printer without producing holes. It is easier to add ballast than to take it away. I'd like to find a technique that allows 2 perimeters on the outside of the hull and 1 perimeter on the inside. You need to start by considering the size of the parts you can't change - the motor and prop shaft.