Raymarine forum

Hi there!
I have a sail catamaran with a hydraulic steearing system that includes two seastar cylinders (BA150-7TM / HC5318), a liquid tie bar, a Seastar pump (HH5272-3) and a Raymarine wheel autopilot (Raymarine Evolution EV-100 T70152 Wheel Autopilot Pack). I want to install a new E12139 eletric autopilot pump in this system (my controller is ACU-100) but I don´t know if the ram capacity is enough to my system. The cc volume of each cylinder is 167.3. Can you help me?

regards,

Jefferson
Adhara - Brazil

Dear Adhara

Thank you for your enquiry.

Based on your information, the fact you mention there is a liquid tie bar and the displacement of the hydraulic cylinders there are a number of issues here to resolve.

The cylinder displacement of one of the cylinders at 167.3 indicates the displacement is too big for a T0.5 pump and so a T1 pump is needed. This is too large for an ACU100 and so an ACU200 will be needed.

The Hydraulic tie bar indicates that although you have two steering cylinders, they will be connected in series and so the oil discharged from one, will move the other cylinder, in theory keeping them aligned, however, in practice, this does not work so well, over a period of time, oil will seep past the seals of one or other of the rams and this will lead to them gradually slipping into different positions and the rudders will become misaligned. Systems using a hydraulic Tie bar tend to have a balancing valve that enables the boat owner to resynchronise the rudders periodically. This will need to be monitored closely, because it will have a bad effect on the performance of the autopilot and lead to poor course holding.

Normally catamarans use a solid bar between the rudders or two cables to keep the rudders synchronised.

regards

Derek