[RichH]

Kindly explain exactly what you mean by 'rudder vibration'.

The reason I ask is that Pearson used the quite common "NACA 63A010" type of foil shape profile for their keel and rudder shape. Such shapes if not perfectly 'faired' and kept 'smooth' at the leading edges, can easily develop hydrodynamic 'anomalies' that can be felt in the rudder. If all your work doesnt lessen your 'vibration', perhaps we can discuss in more detail later on how to lessen this - slight changes to the leading edge shape, minor fairing of the leading/trailing edges and the need for SMOOTH bottom paint, etc.

NACA 63A010 AIRFOIL (n63010a-il)

 

[RichH]

The wheel wants to turn one way, then the other, repeatedly, back and forth, with a small motion. This was not the normal keel/rudder hum that is enjoyable at top speeds in certain conditions.

Aha! the keel is probably shedding vortexes and the formerly loose rudder allowed the amplification, probably the rudder also is/was shedding the same type of vortexes.
Such foil shapes will do this if the surface is not 'smooth', especially from the leading edges (bow, keel and rudder assy) back to about 30% of the total cord length of each 'foil' segment.
If you have 'rough' bottom paint (typically applied with a roller which leaves 'stipple' bumps) this effect can be quite pronounced. Especially if youre applying an ablative paint ... sand the old 'paint pimples' so that the tops of the pimples are flat, apply the new paint with a roller then immediately follow up with a 'wipe' of plastic trowel (The yellow WEST system trowels are best) and allow to fully dry/cure .... then repeat until you get a mostly smooth surface. The wiping with a poly trowel will fill-in the craters between the 'stipples' and paint bumps.

You can also 'sharpen up' the trailing edges but this isnt as important as to work on the leading edges to about 30% back from the leading edges which will lessen those 'vibrations' (parasitic vortexes).
What will happen is the flow water along the entire length will become less 'turbulent', will create less 'vortices' ... and you should then notice that keel will better 'lift to weather' and the boat will have significantly better 'light wind' performance - a plus on the Chesapeake in mid Summer.

Great job on the 'rebuild'.

regards
RichH