The last 24 hours have seen Dee Caffari working hard to solve the autopilot problems that continue to threaten the Aviva Challenge, her single-handed attempt to sail non-stop round the world against the prevailing winds.

Caffari has slowed Aviva’s progress as she makes her way towards the Falklands and Cape Horn to allow more time to isolate the autopilot system faults. This testing is likely to continue for a further two or more days. However, as weather conditions look set to worsen, the pressure is now on to solve the faults as soon as possible.

Caffari has to contend with problems on both her main autopilot, which began losing hydraulic fluid on Christmas Day and her back-up system, which has experienced glitches for several weeks now. She and her shore team agree that the voyage cannot safely continue around Cape Horn unless the causes can be traced and fixed.

Taking on this task in good conditions would be a challenge, but Caffari also has to contend with the prevailing weather. Aviva Challenge Weather Router, Mike Broughton comments: “Normally when yacht racing across the ocean, the plan is to avoid the centres of high-pressure. With the light winds, boats can get becalmed for long periods. Troubled by the autopilot problems, she is sailing slowly on purpose, keeping closer to the ‘high’. This means she keeps the boat on a ‘level keel’ for longer, making the work on the autopilot boxes at the stern of Aviva much easier.

“A low pressure is now moving east towards Dee’s position from the Argentinean coast. This will bring stronger winds, but they will be from a favourable direction and continue to allow the boat to be sailed upright relatively speaking. On the down side there is a lot of rain associated with this ‘low’ and we must hope that Dee can make progress before the worst of the rains arrive. Working on hydraulic pipes and electrical switching circuits in the middle of a full frontal downpour, is far from ideal.”

Aviva Challenge Project Director Andrew Roberts said “Yesterday, we believed that we had a 50/50 chance of finding a solution, we are feeling more confident today as Dee starts to make her way through the various tests. However, we will know more tomorrow when we have completed more of the tests.”

Autopilot technical information

Dee’s recent diaries tell of the considerable struggle and frustrations she has been having with the autopilots systems. Before Christmas we were all confident that Dee had successfully solved the problems but only a few days later a bitter blow was dealt to Dee when, in difficult conditions, serious problems came to light with the fully functioning pilot.

None of the key components of each independent system are faulty, but it is the secondary components where the problems originate. The intermittent nature of the electrical faults make them very difficult to find and because of the complicated switch over system, there are many computations to test.

The latest problem to beset Dee requires her to bleed the air out of one autopilot’s hydraulic system which is both difficult, time consuming and messy.

Because of Aviva’s size, much of the equipment has to be in proportion to cope with the high loads found on a yacht specifically designed for the Southern Ocean. The autopilots and their hydraulics systems are a good example in that the rudder they control projects 2.5 metres (8 feet) below the hull and is over 1 metre wide (3 feet 3inches) at its widest point. The rudder’s area is greater than a large desk so has to be enormously strong because of the massive shock loads that can occur when a wave hits it, or the yacht plunges off a huge wave. In fact the lower bearing, which is 1 metre below the hull, is structured to accept a sideways load of 19 tonnes.

Consequently the autopilot hydraulic rams that push and pull a tiller (steering arm) connected to the rudder are in proportion size wise. Each of the rams is approximately 600 mm (2 feet) long and 75mm (3 inches) diameter and is driven by an electrically powered pump mounted at the aft end of the aft cockpit. Each hydraulic system holds over 2.5 litres (.5 gals) of oil but 4.5 litres would be used to purge the system of a relatively small amount of air.

Hydraulic oil is nasty stuff at the best of times but filling a header tank, switching on the pump and opening a bleed nipple to allow oil and air to be forced out under pressure is both messy and difficult. Throw in the motion of the yacht, a fresh breeze and salt spray whilst crouching in the bottom of the cockpit for an hour, and the difficulties become more apparent. Then there’s the question of cleaning up the hydraulic fluid that has escaped onto the teak gratings and paintwork as well arms and clothing.

Once this is completed the time consuming testing of electrical connections and components can continue but there are also concerns over the quantity of spare hydraulic fluid that Dee has left.