Reporting in with more nformation:��
(1) I talked to a marine engineer
he had some VERY interesting bits of information about rudders.
He told me there should be NO play in the bearings any AT ALL, any is out of spec.
He fixed a loose bearing on one boat, underway, by inserting a plastic Coke bottle, it has lasted several thousand miles and is still OK!
He suggested the [lower] autohelm
arm's through shaft bolt is critical and should be replaced or a clamp added, a fail is catastrophic from the leverage if the rudder drops onto the top quadrant.
A very recent beneteau rudder failure was caused by resonance from the propeller
amplified buy loose steering cables
that destroyed the bottom bearing housing causing a slowish leak.
In a thousand miles the shaft might go through 80,000 cycles, but bearing failure isn't normally unpredictable, so the play will slowly increase to the point there is a mechanical failure - replace early or check regularly.
(2) I talked to Beneteau tech support:
12mm is the maximum play allowable on a NEW beneteau at the bottom rudder tip. Old boats: "If you can feel any movement of the rudder shaft IN the shaft log then it's time to sort out the problem"
Perhaps it's the bearings, could also be the shaft is warn thinner, the shaft log itself has been ovaled or one of many other factors.
"The quadrant and autohelm
arms don't have published torque settings for the through and clamping bolts". I forgot to ask about cable tension.
Scary! It is obvious that the torque is critical as both arms clamp the rudder shaft, to much torque crushes or weakenes the (hollow) rudder tube to little and the rudder is only held by the through bolts.
(3) Measurements I made when the boat was 5 years old are very! surprising - in light of the spec beneteau provided of 12mm! Perhaps my figures were contaminated by the force I used (blade flex?)or the way I did the measurements?! Hmm not sure..
shaft = 500mm (between top and bottom bearings)
blade = 1600mm (below bottom bearing to tip)
Total length = 2100mm
Fore-aft play: = 51.15mm(bottom tip)
When pulled really hard and held under tension. calipers used.
Side-to-side play: = 42.21mm
Pulled as hard as possible, loverly assistant using calipers.