I wanted to use the full thrust of my impeller. As seen in the video of the impeller boat: http://www.thingiverse.com/thing:274054 the high positioned and heavy motor capsized it already with little throttle. So I took two long boats and put them together to get something like a two hulled boat. The one is allready puplished: http://www.thingiverse.com/thing:284692 The second one is the enlarged impeller boat. Both needs a bridge to mount the impeller housing which connects the boats. Actually it needs only one rudder. This should be on the motor boat with the keel. Of course two bords also need more power. So you can only make speed if you use a pretty strong motor. Sometimes you hear a sibilant noise. Then splash water comes into the turbine. And at the end there was also some water in the boat :-) The big advantage: it will hardly capsize ;-) http://youtu.be/VkcLYyyEtxc And don't miss to close the stern tube. I used M2 srews covered with heat shrink tube. Otherwise you will not only get splash water into the boat...Printing The best is, if you print the hull with spiral vase methode. Then you will get a neat surface without any noses from layer change. 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. 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. Bridges Layer hight: 0.3 mm Width: 0.5 mm Infill: 0.5 Solid layer: 2 on bottom and top The hull of the impeller boat became wider after printing it. This is due to the flat floor in the boat that generates tension. Therefore I designed one bridge plus 3 mm. There are M3 holes to fasten the impeller housing with screws M3x10 mm. And M2 holes to fasten the bridge to the hull with screws M2x5 mm. I recommend to put metal strips between the screws and the hull to protect the hull from penetration. For this I used brass strips 6 x 80 x 0.2 mm. All remaing parts you can take from: http://www.thingiverse.com/thing:284692 (motor boat enlarged) http://www.thingiverse.com/thing:272132 (motor boat) http://www.thingiverse.com/thing:274054 (impeller boat)