Prop Walk II - May The Force Be With You
In this sequel to the first SSC Prop Walk video, we repeated the experiment, only this time we mounted a crane scale on the starboard stern line to measure the force that was produced. The stern line was positioned to be perpendicular with the boat's centerline and at the fore-and-aft position of the boat's propeller.
We went on to measure the comparative side force of the rudder at full deflection (about 30 degrees) and of the backing force when the engine was in reverse. Can you guess which of the three numbers was highest?
The boat is a 1979 Freya 39 with a Michigan Wheel 17 x 10 2-bladed propeller. The tests were conducted on June 21, 2022 (the summer solstice). The hull and propeller were cleaned by a diver the day before the tests.
An important caveat to these tests is that they were conducted at steady state and with zero speed of advance. This is not generally the case when maneuvering, and values could vary dramatically from what we measured. Nevertheless, the experiments provide great insight into the absolute and relative magnitudes of the forces involved.
We hope you get a lot out of it!
