Autopilot -- Linear Drive Sizing/Interface - SailNet Community

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Old 12-29-2013
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Autopilot -- Linear Drive Sizing/Interface

A technical autopilot question. I did a number of searches but cannot find anything on point.

I have a Simrad AP26 system with the AP20 Computer, RC136 rate/heading sensor, and RF 300 rudder feedback unit. The boat is an old 56 foot, 33 ton, full keel steel ketch with a 3 X 4.5 foot rudder and cable steering. The AP26 system is not yet installed.

Looking at the internet info available, it appears that I will need about 2000 pounds of max thrust from the hydraulic linear drive. The Simrad HLD2000MK2L only puts out about 1100 pounds. Most actuators have a 12 inch tiller arm and a 12 inch stroke.

About the only options I see are the Raymarine type 3 with 2700 pounds max thrust and the Garmin class B with 2380 pounds. Both companies advise that the actuators can only be used with their autopilot system but I wonder a bit about that claim.

Questions-- (1) Does my 2000 pound max thrust requirement seem valid for the size and type of boat? I have had one input that the Simrad HLD2000 was fine. Any experience from installers or users?
(2) Has anyone out there interfaced a Simrad with either of the above actuators?
(3)Any ideas on other potential solutions to my problem-- for example other suppliers or used equipment?

Last edited by kaakre; 12-29-2013 at 02:17 PM. Reason: typo
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Old 12-30-2013
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Re: Autopilot -- Linear Drive Sizing/Interface

Quote:
Originally Posted by kaakre View Post
A technical autopilot question. I did a number of searches but cannot find anything on point.

I have a Simrad AP26 system with the AP20 Computer, RC136 rate/heading sensor, and RF 300 rudder feedback unit. The boat is an old 56 foot, 33 ton, full keel steel ketch with a 3 X 4.5 foot rudder and cable steering. The AP26 system is not yet installed.

Looking at the internet info available, it appears that I will need about 2000 pounds of max thrust from the hydraulic linear drive. The Simrad HLD2000MK2L only puts out about 1100 pounds. Most actuators have a 12 inch tiller arm and a 12 inch stroke.

About the only options I see are the Raymarine type 3 with 2700 pounds max thrust and the Garmin class B with 2380 pounds. Both companies advise that the actuators can only be used with their autopilot system but I wonder a bit about that claim.

Questions-- (1) Does my 2000 pound max thrust requirement seem valid for the size and type of boat? I have had one input that the Simrad HLD2000 was fine. Any experience from installers or users?
(2) Has anyone out there interfaced a Simrad with either of the above actuators?
(3)Any ideas on other potential solutions to my problem-- for example other suppliers or used equipment?
AFAIK all autopilot units control the drive unit in the same way, by controlling current and polarity going to the drive unit. The AP unit must be able to deliver at least the current the drive unit will use at max load.
To AP "brain" also need a rudder angle sensor - some drive units (Garmin) have this built into the drive unit.

Have a look at the Autopilot drive units here Jefa Steering Systems
Direct link to the drive units here Autopilot drive units

I have got good help from Stig at Jefa when I upgraded my drive unit, his contact info is here Infopage Jefa Marine

They have a dealer in US -- PYI Inc. Max-Prop PSS Shaft Seal Seaview Radar Mounts R&D --
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