Autopilot Installation (December 2003) Updates to this page are at the bottom Back to Projects
Though the integrated Aires windvane and Tillerpilot (see article) has served well under most conditions, I wanted something a bit more robust and easier to operate and adjust.
My choice was for the Raymarine suite of ST6001+ Control Unit, Rotary Drive and Type 150 Computer system.
The ST6001+ installation was straightforward with bulkhead mounting where it can be read from the helm. That's it below the wind speed instrument ... and yes it was blowing 23 knots when I snapped the photo.
The course computer was mounted in a locker below the navigation station in the recommended position of athwartship for a sailboat.
Not shown is the flux gate compass which was mounted beneath a starboard locker near the center of the boat's pitch, roll and yaw.
The significant challenge was to install the rotary drive and rudder position sensor.
Shown here is the rudder position sensor on a bracket angled 105 degrees to match the plane of a sensor arm clamped to the rudder post. The bracket and sensor arm were locally fabricated from 1/4" stainless steel. Probably a bit overkill in thickness but I believe that more is better! They are positioned below the floorboards of the lazarette locker.
The main challenge was integrating the rotary drive unit with the Edson worm-screw steering system. Only after receiving the installation manual is it possible to determine the sprocket sizes required, which are based on the number of turns lock-to-lock for the vessel. In my case it is 3 1/2 turns. This results in a 15 tooth drive motor sprocket and a 25 tooth steering sprocket. Though the specification was for 3/8" pitch standard chain, which was not available locally, I chose to use motorcycle chain with 1/2" pitch. Again, stronger seemed better.
Edson has had the foresight to mill a keyway on the aft end of the worm screw shaft so removal of the worm screw shaft was not necessary, as I first imagined. I had the sprockets and key fabricated at a local machine shop, again from stainless steel.
To insure alignment of the sprockets I designed and had fabricated a mounting bracket for the drive motor as shown. A reinforced "L" shape, again of 1/4" stainless steel, the bracket is secured directly above the steering shaft pillow block. It was only necessary to shave 1/4" from a teak spacer between the pillow block and the mounting glassed into the underside of the lazarette. Elongated holes in the drive motor base permit precise tensioning of the chain.
The bad news is that the Raymarine autopilot is expensive (you can look it up in your favorite catalog)! Further bad news is that the NMEA interface claimed for the unit does not work with my "vintage 5 year old" GPS (Garmin) or wind/speed/depth instruments (Standard Horizon). At the Raymarine Technical Staff suggestion I contacted NoLand Engineering and obtained a NMEA multiplexer (NM42U $240) that solved the problem for all the instruments except the depth sounder (but that's a fault of the Raymarine unit not accepting the depth data).
The good news is that all machine work, materials and fasteners cost less than US$100. Further good news is that the remote control from my integrated windvane/tillerpilot (Raytheon ST600R) DOES interface with the system since it utilizes the Raymarine SeaTalk standard. The integrated windvane/tillerpilot remain as a backup system.
UPDATE 22 Jan 04: The rotary drive unit failed after 36 hours into our passage from Port Bonbonon to Kota Kinabulu. Email exchanges with Raymarine are underway.
UPDATE 22 Mar 04: An email from Raymarine Technical Support in the USA said:
"Try tapping the rotary drive with a rubber mallet. If this helps then we know that the rotary drive is the culprit. "
I did that and guess what? It worked! I then enquired about the need to return the unit for inspection. After numerous exchanges I finally was advised by Stuart Graham, of Oceantalk Sales, the Raymarine dealer in Australia:
"It is not that unusual for brushes to be sticky when new. Our experience has
shown that as the brushes wear in, the surface area of contact expands and
the units operate without any further problems.
I do understand your concern, however I would strongly suggest you monitored
the units performance for a while before returning it, as chances are you
wont have any more problems!!"
So, keeping a rubber mallet handy I have now sailed several hundred miles in the local area and the unit has performed flawlessly! So much for my paranoia!
UPDATE 26 December 04: During our return
trip from Busuanga in November the ST6001+ Control Unit malfunctioned. I
notified the Raymarine dealer (OCEANTALK) in Singapore of the problem, shipped
the unit to them (DHL screwed up the paperwork with Customs causing a week's
delay), and was delighted to learn that they would send me a new unit.
With our departure just a few day's away, I deferred having it sent to the
Philippines (I really don't trust DHL or FedEx there) but had it sent to Kota
Kinabalu. It arrived at Sutera Harbour marina the same day we did ..
Christmas Eve. I used my backup control unit (handheld) for the passage
without incident. Kudos to Thomas Beck and Mr Lee of Oceantalk Asia,