As The Propeller Turns
One of the more interesting builds that went in to this steam launch is the propeller that moves the launch through the water.
Initially, I did not really put much thought into the propeller, and going through a selection of propellers I had lying around from the radio controlled model gas powered boats that I built at one time or another, I choose a propeller that looked about the right size. Well, wouldn't you know it, when I steamed the launch for the first time, I could not keep a head of steam up. I quickly realized that the pitch of the propeller which was meant for a fast turning gasoline engine was to fine a pitch for a steam engine..
Back in my shop, I did the work-up that should have been done initially, as I realized that I needed a propeller with a pitch meant for a slow turning high-torque steam engine, I rolled up my sleeves and went to work constructing a steam boat propeller. This 4 bladed propeller is 2.5" in diameter, and with a very coarse pitch that is suited to a slow turning steam engine. With the propeller completed and the launch back in the water, it was a whole new ballgame.
With 30 psi showing on the pressure gauge and the throttle wide open, you need to not quite break in to a run to keep up to the launch as it moves along at top speed, and the good thing is that the boiler can maintain a head of steam while doing this.