Maybe
not all rudders are as bad as mine was so it is worth checking
particularly if your steering is not precise, Apply these
tests to the rudder to see what needs fixing.
| Test on Rudder |
Effects and Explanation |
Modification required |
| Gently hold the rudder and
move it from side to side to see how much slop in the
rudder drive system. |
makes precise steering difficult as
there is a 'dead' zone where moving the transmitter
stick has no effect on the rudder caused by slop in the
rudder drive systems. |
Ensure the rudder steering
arm is firmly attached to the rudder shaft. |
| View from the stern while
yacht on the stand. Check how much movement of the
transmitter stick is required before the rudder moves. |
this test the 'dead' zone more
precisely. Any 'dead' zone makes precise steering
difficult |
Make sure the rudder is not
binding on the hull. Trim away some of the plastic
on the rudder with a sharp snap blade cutter. |
| View from stern, move
transmitter stick to the right then let it re-centre.
Notice where the rudder stops. Now move stick to
left and re-centre. Where does rudder stop now? |
This tests the dead zone including that
in the actual servo. If the rudder does not
re-centre there must be some 'dead' zone' in the servo
itself making steering imprecise. |
May need to replace the
rudder servo with a better quality one! Almost any
you get from an RC model shop is going to be better! |
| View the rudder steering
arm and the servo arm with the rudder centred. Are
the two arms parallel or nearly so? They should
also be nearly at right angles to the yacht fore aft
line see later test. |
If not parallel then steering will be
different when moving rudder to the left or right. |
Undo small screw on top of
servo arm (don't lose it!) and lift arm off servo shaft.
Replace arm on servo with the arm most nearly parallel
with the rudder arm. Replace the screw.
Adjust the connector on the end of the servo arm by
removing the screw and rotating the clevis on the
threaded rod until rudder is centred again.
Replace the screw. |
| Remove the rudder from the
yacht and vie from the side. Is the rudder shaft
about 20-25% back from the leading edge or is it further
back? |
If more than 30% back from the leading
edge, the rudder will be unstable flipping from the end
of the slop on one side to the end of the slop on the
other side as the rudder shaft pivot is behind the
centre of lift of the airfoil. The centre of lift
of the symmetrical airfoil is about 33% back from
leading edge Steering will be like that of a drunken
sailor wobbling from side to side. |
Rudder post must be shifted
forward. Its easier to replace the shaft than fix
the one there. It will
also mean probably replacing the steering arm |
| View the rudder shaft from
the top. Is the flat at right angles to the rudder
or set off at an angle? |
This will mean the rudder steering arm
is not at right angles to the rudder. It is
difficult to get symmetrical movement of the rudder with
this set up. For optimum steering the rudder
steering arm and the servo steering arm should both be
at right angles to the fore aft line of the yacht.
See the article on the Stirling web site on 'sailing
hints' and 'Rudder
and Rudder Servo set up' by clicking the link. |
While it seems a little
agricultural, this can be fixed fairly readily.
Support the rudder shaft in a vice near the end away
from the rudder so the flat is facing directly up.
Use a gentle heat from a gas blowlamp to heat the shaft
1-2cm from the rudder. Support the rudder with
your hand. When the plastic of the rudder becomes
a little soft twist the rudder on the shaft to make the
rudder vertical. Let cool while ensuring shaft is
in line with rudder. Top of rudder may need slight
re-trimming. |
