Dee’s recent diaries tell of the considerable struggle and frustrations she has been having with the autopilots systems.
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.
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Enquiries:
Karen Earl Sponsorship
Georgina Spring +44 (0) 207 202 2854 or Caroline Ayling +44 (0) 207 202 2840
Aviva
Hayley Stimpson +44 (0) 207 662 7544