Like the motor boat http://www.thingiverse.com/thing:272132 I wanted to make another bigger boat. So I just scaled up my boat http://www.thingiverse.com/thing:204303 to about 200%. Only the transom is half as thick. It can be printed in two parts: 162,5 mm (aft) and 163,5 mm (bow) height. Additional it has now a impeller drive and rudder control. The complete rudder control unit can be taken from http://www.thingiverse.com/thing:272132 I tried to use my Roxxy BL-Outrunner which I already used for my plane http://www.thingiverse.com/thing:86982 But as you can see on the video, the boat is pretty overloaded with it. Only a little mistake is enough to turn it upside. So I had to go back to the little dc motor which makes it much more relaxing ;-) http://youtu.be/UBQ-xlQTCDg I used only a 2 cell battery because the impeller with only 2 mm hole was not printet exactly concentric. With higher speed it touches the housing. However, the impeller M5 runs perfectly even with the Roxxy BL-Outrunner. For testing it I just bonded the two parts with tape ;-) Attention: You will use it at your own risk! Be aware that there will accrue unexpected high centifugal force if you run the impeller with high speed!! If the blades have not a strong connection to the hub, the blades can pull out and become dangerous. So be careful if you use a strong and high speed running motor like the Roxxy Outrunner that I used! Here you can calculate the centrifugal force: http://www.kfz-tech.de/Formelsammlung/Fliehkraft.htm And better choose flat water without waves and where you can go in - in worst case... ;-) Update MHarvey82 asked me to split the hull in three pieces. So I made an alternate design and uploaded the files: impeller boat bow 119 mm.stl impeller boat middle 103 mm.stl impeller boat aft 103 mm.stl impeller boat interface front.stl impeller boat interface back.stl The bow is now 119 mm and the other two pieces are each 103 mm high to print. And of course there are two new interfaces. Printing The best is, if you print it with spiral vase methode. Then you will get a neat surface without any noses from layer change. Hull The hull is 3.0 mm thick. I printed with layer hight: 0.3 mm and width: 0.6 mm. Anyway, you have to print it hollow with one perimeter otherwise it will not fit inside the interface part to connect the bow to the aft. I added a small base on aft to get more brim. I printed without heatbed and used 6 mm brim. And yes, be very careful, if you reach the nose. Reduce the temperature and speed by and by in small steps. Printing the Aft The stern is 1.2 mm thick. That means you must take four 0.3 mm solid layers on bottom to get a complete solid stern. The top (the connection to the bow) shall not have solid layers to stay hollow. Slice3r don't add solid layers on top, how many ever you enter. But I don't know how other slicers work. Printing the bow Here you shall not have solid layers, just a little brim. Interfaces The interfaces are supposed to put them fifty-fifty in the gap of each hull part. In this way the the hull parts are aligned and easy to glue. Before gluing you should mask the edges of the hulls with tape to keep them clean from glue. Impeller Layer height: 0.3 mm, width: 0.5 mm, infill: 0.2, 2 perimeter, 3 solid layer on bottom and top Impeller housing Layer height: 0.3 mm, width: 0.5 mm, infill: 0.2, 2 perimeter, 2 solid layer on bottom and top Drive The small drive I used is a dc motor that tolerates even a 4 cells battery. It has a diameter of 24 mm and a shaft of 2 mm.