Goolwa Radio Yachting Group

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Goolwa RC Yachting

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Modifications to Rudders on the Phantom Yacht

Rudders Chain Plates Mast fitting for shrouds forestay Mainsheet fairlead Water proofing the hatch Improving Ballast Replacing Shrouds 'B' rig sails Radio Setup Clew/Tack Adjustment Improved sheeting system Gooseneck repair


Rudder modifications

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.





page last edited on 27/10/2011