Sometimes in life, simple is, well, complicated. Comparable to a fractal image, the deeper you go, the more you find. Such a situation occurred with our steering gear.
This Blog is for readers building their own projects. Not as a tale of woe, more woe betide anyone who does not expect this to happen.
It's not a disaster, but it does take a few cool heads to work through.
So here we go; firstly, it was a multi-part problem with each player seeing the issues through their own eyes.
Will Ridley - supplier of our steering system.
Praxis Automation - steering controls and Dynamic Positioning (DP0).
Furuno - Autopilot (supplied and integrated by Praxis)
Naval Yachts - boat builder.
In spring 2023, Praxis substituted a component for a Furuno 711c Autopilot system as it is easier to support in the field, and their own Heading Control System is proving problematic. The Furuno 711c is a clever piece of kit with self-learning functions.
This action resulted in an Autopilot system independent of the Praxis system; we lost the handoff and other coordinated functionality.
Additionally, the loss of functionality with the installation of the Furuno 711c Autopilot dictated additional components at the helm stations, notably an NFU jog lever and FFU wheel. (None Follow-Up, Full Follow-Up)
Wills Ridley had provided an initial design that placed all steering command selections at the main helm. A hand-off between the main helm and flybridge was missing from the picture. We did not look forward to a future of running between helms, so we needed a more integrated design.
The system was no longer "Praxis Centric" and now potentially had four modes of operation instead of just 2. And so the debate began on how to simplify this mess. It began with a considerable amount of circling, partly through a lack of understanding of systems by the players in the mix, including yours truly.
The Good Points:
All players kept civil and cool heads; no blame attached; it happens.
Wills Ridley took time to educate everyone, filling the apparent knowledge gaps and helping to narrow the proposed solutions.
All players provided feedback in real-time, limiting frustration and delays.
The owner (us) was prepared to take different roles in the debate and help reconfigure a now suboptimal system design.
Require steering control from both helm stations. This included NFU Jog Lever, Autopilot linked to the TimeZero nav system, and FFU wheel.
Helm control hand-off will be by a single crew member from one helm station to another (short-handed operation).
Dynamic Positioning and emergency hydraulic steering are restricted to the main helm.
Minimize the occurrence of systems daisy-chaining commands as this is a point of failure we don't need.
Limit the thought processes needed when switching between various steering modes - look for instances of "no further thought is needed!". "Stupid, tired, cold, hungry" derived accidents are best avoided.
The Solution and thought process
Praxis/Wills Ridley/Furuno autopilot is selectable using a 3-function switch (plus dimmer) on each helm with an automatic handoff of each between the flybridge and main helm.
Autopilot is configured as a stand-alone system and linked with the TimeZero navigation system for course tracking, waypoints, perimeter alarms, etc.
Independent Furuno rudder feedback linked to Port (lead) Wills Ridley steering controller. Furuno 711c has a limited jog function built in (think COLREGS maneuvers in open waters), so we do not need an additional Jog lever.
Autopilot 711c Units will automatically hand off within the system between the main and flybridge helms; no further thought is needed.
Praxis: Praxis Steering controllers receive rudder position from Wills Ridley CAN bus communications ports fixed to both Wills Ridley Rudder Angle Indicators (RAI); this removed the need for additional RAI units linking both rudders. We removed two additional dedicated Rudder angle Indicators, and wiring became simpler. FFU wheel function fed directly to Praxis Steering Controllers.
When Praxis Steering is selected, hand-off between helm stations is pre-configured as the Praxis engine controls are switched from the main to the flybridge. No further thought is needed.
Praxis Dynamic Positioning System is set as stand-alone and works at the main helm station only. Controls drive line, independent rudders, and bow thruster. No further thought is needed.
Wills Ridley: Steering units have two output rheostats linked one to each rudder. Rudder Angle Demand and Rudder Angle Indicator (Feedback) are displayed on the Praxis system, thus limiting duplication.
Wills Ridley NFU jog lever is linked directly to Wills Ridley steering controller. Once WR steering is selected, then this will work on both helms no further thought is needed.
We can now sail along happily on Praxis steering and switch to Praxis DP0 at will for any close-quarters stuff. Note Praxis have supplied a portable controller for their DP system, so we can work this from anywhere on deck or the nearby dock. Sort of like a video game, only with a 62 ton puck!
When we want Autopilot at sea, we simply switch to that function and carry on. We have an integrated jog function within this for course corrections and COLREGS maneuvers.
If all fails, we can switch to Wills Ridley manual steering.
If even that fails (a bad day), we have a manual override for everything using a hand-steered hydraulic pump.
Loose one rudder; we can lock it and sail with just the other with any system.
All but the hand hydraulic function will automatically switch between the main helm and flybridge with a well-designed handoff.
To facilitate all this, we have to upgrade the Wills Ridley steering controller; they have graciously offered a rebate on the original unit.
What could we have done differently?
Bought a simple sailboat that was Plan A and now faded into the distance.
We needed a better brief at an earlier stage and to look more closely at the steering philosophy beyond a conceptual overview.
The Autopilot change came from left field, to quote US jargon. That was unavoidable and forced a rethink of how it all interacted.
No one panicked on this issue, and we did find a good solution given the very late stage of our build.
FFU - Full Follow-Up - rudder reacts to achieve position set by lever
NFU - None Follow Up - rudder reacts when lever moved off center.
Useful Contacts : I thank the Wills Ridley staff for working with us on this issue and changing plans in mid-supply. Wills Ridley - Mike Kitchener, Director, firstname.lastname@example.org