Although the red internal
lighting had been working when I left the UK, it had become intermittent
before finally giving up the ghost altogether. Checks of the
switch and fuse revealed no problems. It was impossible to trace the wiring from the switch
panel, so the compass needed to be removed from the steering pedestal in
order to work 'backwards'.
Removed 4 nuts from around the base of the compass binnacle and lifted
the complete assembly and wooden base from the pedestal top plate. This revealed a
broken live wire caused by corrosion, at the point of entry into the
steering bevel gear housing. The remaining blue neutral wire can
be seen in the photo. There was insufficient cable to make a new
connection, so the top plate would have to be removed also. After
scraping out the old sealing compound, two bolts were removed from the
engine morse control (bottom left of picture) and the four bolts securing the
plate to the pedestal were removed. Then the two bolts securing
the plate to the 'grab bar' were withdrawn, allowing the plate to slide
upwards along the bar.
With the pedestal top
plate out of the way and the upper bevel gears of the steering exposed, an unbreakable
thin mouse cord was tied to the cable and the cable pulled down into the
engine compartment immediately below the pedestal.
Unfortunately........the cable and the mouse parted
company when doing this, leaving the problem of how to get a new
mouse or cable through the pedestal. The top hole is only about
4mm diameter (under the grease) and the lower hole is hidden somewhere
at the base of the pedestal, in a somewhat inaccessible part of
the engine compartment. Despite many hours of using mirrors,
reaching in and taking photographs and generally feeling around with my
fingers, I was unsuccessful in locating the lower cable entry/exit
The only other option is to remove the
pedestal from the cockpit deck - a complicated job which entails wheel
removal, disconnection and removal of the autohelm, unbolting the
lower steering universal joint and gearbox and finally unbolting the
pedestal from it's mount. Even then....it seems unlikely that a
new cable could be run through without further dismantling of the upper
bevel gears and vertical torsion bar. Because of the
impracticalities and difficulties of actually doing that, I decided on
the less aesthetically pleasing option of running the cable up the
outside of the pedestal until such time as it becomes essential to
remove the pedestal for major repair or maintenance of the steering
The upper steering bevel gear
housing - mouse and cable connected
Lower end of
steering pedestal - looking forward
With the compass and
binnacle already removed from the pedestal, I now turned my attention to
the problem of the wildly fluctuating compass card. Firstly, the
compass needed to be separated from it's binnacle. This was
achieved by the removal of the light hood and four securing screws.
The lower mounting ring and gasket were removed and, on inspection of the diaphragm,
a small split on the rounded bottom edge was
revealed - the cause of oil
loss and subsequent un-damped card. A new diaphragm would be
needed from the manufacturers in the UK.
Sestrel Major Mk I
The location of
the diaphragm and gasket can be seen in the lower part of the diagram on
Below - diaphragm ready for removal
The old diaphragm,
(left) is basically nothing more than a small, flimsy plastic
dish. I've placed an AA battery inside to give an idea of size and
the small split can be seen at the 1 o'clock position.
This inferior quality 'tupperware type' bowl costs an amazing £28.50 from the
manufacturer! Basically, the diaphragm forms the bottom of the
compass and, because of it's flexibility, allows for expansion and
contraction of the contained fluid as climates change. The fluid
used depends on the compass manufacturer (you could use distilled water
if you avoided low temperatures!). There are stories of gin being
used in some compasses, or paraffin in others. The manufacturer's
recommended fluid for my particular compass is 2 litres of Bayol-35 at
£13.90 per litre.
With the compass
inverted , it is a simple matter of replacing the 'O' seal (£14) in it's
groove, fitting a new diaphragm and replacing the mounting ring before
filling the compass with fluid.
I chose not to use
Bayol-35 as the damping agent, but the cheaper option of Johnson's Baby
Oil instead - ensuring that the compass contained no residue of Bayol,
(although it's probably the same anyway) and I used a large syringe for
this purpose, as the feed hole is quite small.
Compass and binnacle removed.
The old 'split' diaphragm
Filling with baby oil, and the level after
"After filling, rotate the
compass gently until all the bubbles are removed". This is easier
said than done and no matter what I did, I was left with a small bubble
in the dome. Without the benefit of vacuum gas removal equipment,
I resorted to the 'fix it in the field' method and placed the compass in
the fridge for two hours, along with a syringe full of baby oil.
On removal, the bubble was
much bigger, which allowed me to put in more oil until it disappeared
and I then allowed the compass to stand overnight. The difference
between full and empty was now very evident, the numerals appeared much
larger and of course the unit was much heavier! But, next
morning.......on shaking the compass to check the damping of the
card.......a small bubble about 5mm diameter, which had obviously been
trapped somewhere beneath the card, appeared in the dome - and this
time, after hours of trying, I was unable to get rid of it.
However, a week or so later, the bubble disappeared of it's own accord
and has not returned after two years.
Now I turned back to the
lighting part of the compass. A
previous fault, by whoever installed the lighting and which I
hadn't fully realised was that when the compass light was switched
on......the engine instrument lights also came on! Instead of just
two red diode type bulbs illuminated when under sail at night, an
additional five normal bulbs were lit. Clearly, that is
unacceptable. I removed the instrument panel (not in itself an
easy job because it is bolted rather than screwed and involved crawling
around behind the panel) then fitted a waterproof switch, taking the
compass light cable direct to the compass and the new switch spurred to
the instrument panel, allowing the panel lights to be turned off except
when under engine power. Now I have a satisfying red glow from the
compass at night, which is nowhere near as bright as it previously was
(when it worked!) and which I can only attribute to the fact there
wasn't any fluid to diffuse the lighting.
My thanks to Annette at
SIRS Navigation Ltd, who was extremely helpful and friendly when
ordering spares (it's not her fault they cost so much!)
Full - but small bubble between SW and W.
A satisfying night-time glow!
MANUFACTURER and SPARES:
SIRS NAVIGATION LTD Compass House, Bowes Estate, Wrotham Road,
Meopham, Kent, DA13 0QB, England.