It turned out that it don't runs straight ahead if driving this boat with an impeller. It runs more like a drunken sailor ;-)
Therefore I designed a kataraman that has much more directional stability.
This time I got something bigger for testing - a bath tub ;-)
I used the same drive again that Oliver designed for his impeller-truck :-) http://www.youtube.com/watch?v=h_ZOYQsWkps
The best is, if you print it with spiral vase methode. Then you will get a neat surface without any noses from layer change.
The hull is 1.5 mm thick.
I printed with layer hight: 0.3 mm and width: 0.6 mm.
If you need to scale down you maybe need to reduce the width also because there must be a gap between the two perimeters. Otherwise it may not print continuous without stopping - even in spira vase methode.
And yes, be very careful, if you reach the nose.
Reduce the temperature and speed by and by in small steps.