On Feb 18, 2:53*pm, "Randy Haupton" wrote:
I get a vibration in the steering system of my old Owens 27. I've checked
and had checked all the steering linkages and the gearbox and there is no
play. Also I checked the boat (it is old) for hogging underway and none what
so ever. I've got the problem down to being that the rudder is not balanced.
I have called dozens of prop shops up and down the coast to see if they do
rudder balancing, none of them do. I can't even get them to point to someone
who does. Does anyone know of any shops that balance rudders? Otherwise, it
looks like I'm going to have to braze material on to the leading edge of the
rudder and grind it off in a trial and error fashion until the rudder
balance. One old guy said to try bending the rudder relative to the shaft so
the center of effort is moved forward but I don't think this is good advice.
It would give the rudder a forward canted leading edge which I don't think
is good. Thanks.

Randy

In all probability, your vibrations are due to the shape of the
leading edge of the rudder. A knife edge shape to a leading edge will
often promote extreme vibrations in very thin sectioned and high
aspect ratio (depth to length) rudders, especially at high speeds
where they develop 'harmonic' (natural frequency) induced
vibrations.
The most often used keel/rudder shape on sailboats is the airfoil
"NACA 010" shape to promote 'stable' flow across the rudder at most
common speeds, there are other NACA shapes but the "010" will result
in the least hydrodynamic 'stability problems'. Overly thin rudder
sections are very difficult to change to a NACA010 shape profile.
Such NACA010 shapes were primarily developed for air foils but are
used equally as well for 'boat's' keels and rudders.

Do websearch for "NACA 010" and simply 'scale' those parabolic shapes
to your rudder if you want to 'experiment'.

'Buzzing' rudders can be remedied ... just takes time to change the
shapes, etc. by continued experiment to arrive at one that is
'stable'.