Reply To: Rudder Hum
There have been lots of throries about humming foils as you can expect!
One is that it is often caused by turbulence at the trailing edge of the foils caused by water from one side meeting the water from the other side at a different speed and thereby causing a turbulence. This often seems to be worse on foils with parallel sides where when it kicks off it happens on the whole foil so you really notice it.
I did some tests on a Lark foil I made. What we did was put some sticky tape on the trailing edge each side to make a temporary flexible edge- a bit like a trim tab on an aeroplane elevator.
This stopped the hum so we decided that it was the trailing edge we were looking at. In that instance I did some work to the trailing edge and that stopped the hum.
You couild try just sanding the back edge to make it square and sharp and about 2mm across – that can work. It is often better than trying to get a sharp edge anyway.