#1 2011-02-24 20:43:04

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F26 - Fitting an Autohelm to a Frances 26

[Moved from 'Technical Advice' pages, dated 28/08/09]

Fitting an Autohelm to a Double-Ender like the Frances 26 or Victoria 26

Aim of this web page

There are some real difficulties and compromises involved in fitting an inexpensive and easily available autohelm to our kind of boat. After many mistakes, I have come up with various solutions that suit me and may assist others or may at least make them aware of the problems. Others will have tackled the problems in different ways and I hope that this web page will lead to discussion, possibly argument, and to further web pages describing other installations. I have included a good number of photographs that illustrate the problems and possible solutions but each can have several references in the text and it has been difficult to put them in a sensible sequence.

Our story

Jenny and I owned a lightweight yacht equipped with an Autohelm ST1000 autohelm before placing an order for a new Frances 26 back in 1993. This is mentioned only because the Autohelm unit always worked perfectly, never gave any trouble and was the greatest help to us on our various voyages. Knowing how much better things would be once we owned a moderate displacement, long keel yacht, we requested Victoria Yachts Ltd to fit an Autohelm, as an optional extra. We couldn't really be in better hands since Victoria Yachts Ltd were Autohelm agents and had already talked us into ST50 instruments with a chart table repeater. Their salesman, I won't mention his name, said an Autohelm 800 would be fine since the yacht was so well balance! I begged to differ, since I wanted the ability to use 'wind vane mode', 'track to a waypoint' and generally make use of the Sea Talk bus. I told him to fit the Autohelm ST1000 instead.

After taking delivery of 'Jenter', it was only weeks before the autohelm failed; the push rod became disconnected from the drive. As we were about to depart on an extended cruise, I purchase an Autohelm ST2000 and sent the ST1000 away for repair under warranty. The ST2000 survived our holiday before failing as well, so I refitted the ST1000, now repaired. In all, the ST1000 was repaired three times and the ST2000 just once! All the failures were due to mechanical problems with the drive and the push rod; never electrical.

At some stage I started a correspondence with Autohelm and accused them of not making their autohelms properly; the way they used to. They responded by asking what type of boat I was sailing. When they discovered it was a Frances 26, they wrote that I should have bought their ST4000 model and that the ST1000 was unsuitable because of the long keel, the displacement and the unbalanced rudder. Clearly the fault was mine, or was it? I wrote again and told them that their own authorised dealer had recommended it, sold it and fitted it. All went quiet for a while and then I received a letter asking if I would swap the old ST1000 for a new ST4000, provided I agreed not to hold them liable in any way. It was to be a goodwill gesture!

Time, I think for a photograph.


Autohelm_4000_hard_to_port.jpg
Autohelm 4000 hard to port

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#2 2011-02-24 20:45:20

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Re: F26 - Fitting an Autohelm to a Frances 26

What do you want your autohelm to do?

My first problem was probably a misunderstanding due to lack of communication. I expect my autohelm to safely steer my boat for 90% of the time in all weather conditions and sea states. I don't think this is what the salesman had in mind. I should, perhaps, have made my intentions clearer or perhaps he should have asked!

Autohelm have now become Raymarine but their products have changed very little. If you want what I originally wanted then I have to tell you that even their ST4000+ cannot oblige all of the time and you will have to be a little less ambitious.



What was going wrong?

The reasons for the total of four failures was that the autohelms were repeatedly running up against their own internal stops. The autohelms are really very strong and can take huge loads but this is definitely not good for them. This, in turn, was caused by the autohelm's socket being put in the wrong place; too far forward. Victoria Yachts had provided a small stainless steel platform that took the socket just outside the capping rail. It was neither sturdy enough, nor in the right place. As a consequence, the tiller could only move a small distance from its central position and even that was not the same when turning to port and to starboard. In other words, the installation was a bodged affair. It is easy to see why it was done. The further aft you put your autohelm socket, the further out, over the water, it has to go!

Positioning my new ST4000

All the Autohelm and Raymarine autohelms have the same 'B' distance, i.e., 460mm (18"). 'B' is the perpendicular distance from the tiller pin to the rudder pivot line, which is not easily measured because it passes through the stern of the boat. When you do determine the correct position you also discover another problem. The aft upstand of the pushpit is exactly in the wrong position and the autohelm cannot be positioned correctly.

My solution was to fit the socket on a substantial outboard platform just aft of the upstand. My 'B' distance is about 16" instead of 18". This decision was based on my experience of previous failures and to give the autohelm a chance to move the tiller and successfully steer the boat. No push rod / drive failures have occurred since; a period of 15 years.


Autohelm_2000_hard_to_starboard.jpg
Autohelm 2000 hard to starboard

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#3 2011-02-24 20:48:56

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Re: F26 - Fitting an Autohelm to a Frances 26

An outboard bracket

My present bracket, in use for over six years since the previous one was destroyed in a collision, is made from solid teak 27mm thick and screwed to the capping rail by four large screws covered by pellets. The support bracket is scribed both horizontally and vertically to fit the shape of the hull and screwed through the hull in two places by bolt-headed screws, accessed from the gas cylinder locker. It can easily take my weight with no obvious sign of movement.

There were three previous brackets and each was made stronger and more substantial than the one before. The forces involved can be very high and you really do need to make this as strong as possible.

The socket for the autohelm is well outboard as the 12" ruler shows. The triangular shape of the platform is designed to keep the socket as far forward as possible without any chance of the autohelm touching the pushpit upstand.

On 'Jenter' the fairlead had to be moved aft to make way for the platform. This can cause problems when 'starboard side to' on short marina fingers when it is often better to lead the mooring warp round the upstand rather than through the fairlead.

Below the pillar socket is an ordinary brass socket, which was used successfully for some years. If you set a socket into wood, ensure it is epoxied in position and screwed through its base. It will probably still come loose, as the reaction forces on the socket are high and teak is simply not strong enough.

The tiller supplied by Victoria Yachts soon started delaminating and I made my own rather stronger version with a flat bottom where the autohelm bracket needed to go. I also discarded the alloy bracket supplied by Raymarine, as it flexed and twisted too much. In addition, I wanted to mount two pins instead of one.

My stainless steel bracket is made from 5mm steel and through bolted, not screwed, to the tiller, although this plays havoc with the varnish.

The 'A' distance (socket to tiller pin) for the ST4000 is 620mm but 610mm for the ST2000. The lower and nearer pin is for the ST2000. The high and more distant pin, by 10mm, is for the ST4000. This enables me to use the ST4000 normally but to give the ST2000 an outing when the sea is particularly calm.



Platform_from_astern.jpg
Platform from astern

Platform_from_above.jpg
Platform from above

Tiller_bracket_and_pins.jpg
Tiller bracket and pins

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#4 2011-02-24 20:51:32

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Re: F26 - Fitting an Autohelm to a Frances 26

Autohelm limitations

Autohelms cope well when going to windward, especially if the boat is reefed early. Problems begin when large seas are on the quarter. This can be made worse in relatively shallow steep seas. The forces on the rudder are huge and sailing by hand, one would allow the boat to deviate from course before returning to the course when the wave had passed.

Autohelms don't work that way and I have seen the push rod bend into an arc before the end cap on the rod shattered. This has now happened twice aboard 'Jenter'. This composite cap is clearly visible in the photograph.



Another surprise

After ten years use, the ST4000 did fail when the electronic controlling box started doing strange things. I decided to buy a Raymarine ST4000+. When it moved the tiller fully to port it lifted itself out of the socket. It was also impossible to lift the push rod off the tiller pin except at certain positions.

The problem was that the autohelm wasn't level. I had to purchase the maximum height pillar socket (3" high) to correct the situation. My outboard bracket does slope downwards from the capping rail, as can be seen in Photograph 3. The old Autohelm ST4000 was not nearly so fussy and is still sometimes used, as it works perfectly well with the new controlling box.



Sea Talk bus and NMEA interface

Having both an ST4000+ and an ST2000 and wanting to use both on different occasions has led me to fit two independent power supplies (see Photograph 1). The aft electrical socket is always used with the ST4000+ or the old ST4000 drive unit. The forward electrical socket is used with the ST2000.

Since both autohelms are connected to the Sea Talk bus, I never power the ST4000 with the ST2000 connected as any tiny disagreement between the two fluxgate compasses results in strange behaviour.

Since both the ST4000 and the ST2000 are individually connected to the Sea Talk bus either can be used in 'wind vane mode', which I use quite a lot and find very useful.

The ST4000 electronic controller contains an NMEA input which enables GPS waypoints with associated 'cross track error', 'bearing to waypoint' and 'distance to go' to be put onto the Sea Talk bus. The ST2000 does not have this facility but can share it, provided the two fluxgate compasses are in complete agreement. I frequently use the ST4000 for tracking to a waypoint that is stored on the GPS. If you only have a ST2000 then you would need to buy a special interface to make use of the NMEA interface from a GPS.

To complete the Sea Talk bus and to make the ST4000+ work at all you must have your Sea Talk Instruments switched on and working. The ST2000 does not suffer from this requirement.

Recommendations

If you don't have an electronic autopilot at all and want to buy one then the obvious choice is the Raymarine ST4000+, which you will be able to use in most conditions, most of the time. It is considerably more capable than the ST2000. You will need to make some difficult decisions when it comes to fit it though.



ST4000_push_rod_on_pin.jpg
ST4000 push rod on pin

Pillar_mounted_socket.jpg
Pillar mounted socket

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