Tom (a friend of my son) asked me for a boat hull to be equiped with radio command hardware. I started buiding this first trial, to be tested... and continued. It has a helm and a propeller shaft and is waiting to be filled with stuff to be controlled (battery, servos...). It's a relatively large one (more than 27 cm long) and I printed it in diagonal on the bed (I think it's the largest thing I printed on my RepRap Prism. It is a bit bulky (but it floats) and can certainly be improved (you can derive it). You can add a propeller (at the end of the shaft) like the one I found here : http://www.thingiverse.com/thing:15354 (double sized to fit the scale). 1) Print the hull.