Rudder force

[va3mrj]

I have a 34 ft CHB trawler single rudder. Playing with some idea to cobble together an autopilot using a mix of parts from marine autopilots.

Does anyone know the force acting on a rudder when in a heavy sea (4-6 feet)
in worse case. I have not decided on electric actuator or hydraulic yet. Steering is currently chain and cable.

Thanks for any help

 

[GoneFarrell]

Back-engineer the breaking load of what you have now for the cable fasteners & the chain. Start with that, since it seems to work.

Maybe size the auto pilot actuator force at something less than the above, but with comparable ultimate strength.

With hydraulic you can have a relief valve. With electric you trip breakers.

 

[Arc]

My advice would be to change over to a hydraulic helm, Seastar etc. then install the AP with a hydraulic pump . I think everything will be easier to maintain going forward

 

[Martin J]

Go to the autopilot websites , most of them have sizing program's that work out what is required force wise.