[DG] [DG11] CR hydraulic drive versus Type 3 linear hydraulic

[Derek - Raymarine - Moderator]

Hi shparrot,

Thankyou for your enquiry.

The first point to make is that the two ACUs should not be connected to the same rudder reference unit, they should only be connected to their own transducer, OR use a relay operated by a change over switch to isolate one ACU from the transducer when not being used.

The rudder oscillation you describe is generally caused by the natural flexibility within the steering system and will always be worse when the boat is alongside - usually the water pressure on the rudder when the boat is underway will damp out this flexibility. Further background to thiscan be found here.

The modifications that you have made are all the correct course of action to take, you have not mentioned checking the operation of the rudder reference unit to make sure it is smooth and mounted such that is accurately reflects the movement of the quadrant - any amplification of the movement, flexibility in the mounting of the transducer will also trigger this instability too.

You mention a T3 system, is this the T3 hydraulic linear drive? if yes, then check the drive type selected, sometimes the drive type needs to be set to Mechanical linear not hydraulic depending on how sensitive the steering is.

I would also add that we are introducing new software in the next 1-2 months with some improved performance characteristics for larger vessels - primarily power vessels, but one of the changes we have introduced is a modified rudder damping protocol and this will help you out too, you will find that a damping level of about 7 will be better for your application than the current version at 9. Please keep an eye on our website as the software will be launched there as a free download.

I hope the above helps?
Regards
Derek