How it all began
Since I was a youngster, I built model ships. Functions were always more important than a perfect look. Life steam ships were built later and became the main hobby for many years.
Then the focus shifted to garden railways and still is there now. But some time ago I had the idea of building again a live steam ship, using the recently purchased 3D-printer.
Knowing thrust reversers from my work in the aircraft industry I thought that such a device could ease the design of the steam engine by eliminating the reversing mechanics.
In reverse the thrust would be limited to less than half the forward thrust, but I valued that as acceptable.
Additionally the ship should be equipped with a bow thruster since it would have to operate in small ponds.
Of course it should look historic. A modern Bow thruster would not fit and would be also difficult to build.
So I drew a kind of paddle wheel that would fit nearly invisible under the hull and hoped that it would produce some sideways thrust when operated.
With the 3D-printer the realisation of both devices was not very difficult.
Both the thrust reverser and the bow thruster later exceeded my expectations by far and led to further investigations.
The simple bow thruster
It is a paddle wheel with the axle along the length of the ship, tilted 11 degrees upward at the aft end to ease the connection to the motor.
casting off with the bow thruster
As one can see, it works very well, better than expected. But why?
The theory behind these paddle wheels
The thrust reverser rudder
It consists of two halves that move in parallel when acting as a rudder.
For reversing the two halves close:
On modern aircraft, reversers have an efficiency of 40 to 45 percent. Not bad.
Here is an investigation of the reverser on the experimental- Ship 'ERIKA':
That means an efficiency of approx. 53% !