A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: antique compass revival - questions.
From: George Huxtable
Date: 1999 Oct 05, 5:12 PM
From: George Huxtable
Date: 1999 Oct 05, 5:12 PM
Russel Sher asked- >Hi - I recently unearthed an old Sestel gimbaled compass. It requires >filling with fluid and needs a new card - the existing card seems to be >moth-eaten. >A friend of mine used baby oil to fill a compass - any suggestions/better >ideas on this? >Does anyone have a contact for Sestrel (UK?) - there is a type number on the >pivoting section inside the bowl. >I will probably just use it for display, but would like to restore it. > >Regards >Russell First, here is my short reply. Sestrel was a UK maker who produced some fine compasses, but alas no longer exists. I do not know if replacement parts are available from anyone else. I refilled a Sestrel Minor compass with Johnsons baby oil three years ago, and since then have used it with complete success. There has been no discolouration of the fluid, which is still sparkling clear, and no bubble formation. The viscosity of this fluid may be very slightly greater than that of the "official" filling, as the compass is just marginally overdamped, but not such that you would ever notice the difference in use at sea. You say the card seems to be moth-eaten. If it's simply discoloured, you may find that dismantling the compass and carefully wiping the card clean is enough to restore it. The Sestrel Minor is a dome-top compass with full internal gimballing and a three-inch card. It is nicely illuminated from below. Many of these compasses became available as war surplus after 1945. I have one in use, and one as a spare. Sestrel also made larger compasses, some very big indeed, and you may have one of these. I would guess that the principles will be the same. --------------- Now, for a longer reply, I will tell a story about my problems in trying to fix a Sestrel Minor after its dome was cracked in an accident many years ago. That was in the days when one could obtain a spare dome. The compass was a spirit filled version, and when replacing the dome I emptied the old filling, dismantled and cleaned the innards, and refilled with the recommended strength of isopropyl alcohol, before we set off on our Summer cruise. All seemed well until a cleft started to appear in the underside surface of the dome. Clearly, the alcohol fluid was somehow attacking the plastic dome and eating it away. The new dome and the alcohol fill were completely incompatible. Urgent action was called for before the dome became eaten through, when it would become quite useless. So I emptied out the alcohol fill and replaced it (as a stopgap) with plain water, which had first been boiled up to remove bugs and some dissolved air. Water is a reasonably satisfactory fluid for filling a compass, as long as you can avoid freezing temperatures. That was good enough to see us through the remainder of the cruise, but on return to the UK I decided some expert advice was called for, so visited a certificated compass adjuster and agent in the South of England. He provided a new dome, emptied the water, cleaned and dried the inner components, and refilled with oil. The oil, he told me, was a special oil that was used in food processing, and which he had found eminently satisfactory for compass use. It came from a large drum which was marked as some form of colza oil. The compass was then beautifully clear to read. Off on our next cruise, we were heading down-Channel out of Poole, on a clear (and cool) night, when my wife, on watch, woke me to say she could no longer read the compass. I presumed, at first, that she had been overdosing from the Port bottle but then found that I couldn't read it either. The oil fill had gone completely cloudy. She looked rather like a gypsy fortune-teller peering into her crystal ball, waiting for the mists to clear. We deduced that this was the effect of the cool (but by no means freezing) night temperature on the oil. It was, obviously quite unsuitable stuff to put in a compass that has to live out-of-doors, in a cockpit. The rest of the passage involved attempts to keep the compass warm enough to be readable. We found that if we clasped it in our hands for most of the spell at the helm, that would suffice. Otherwise, we planned to dunk it in a bucket of warm water from time to time. When we arrived at the end of that passage, the oil was poured away, the compass dismantled and cleaned and dried, and once again it was filled with water for the remainder of the cruise. By this time, we had acquired another old Sestrel Minor, so after we got back home, the compass that had given us all the trouble was retired, and languished on a shelf, still filled with water, for some years. When I read, in a sailing mag, a recommendation for filling with baby oil, I decided to give it a try. I had presumed that a compass, being constructed from non-ferrous materials, would be rather immune from rust even when filled with water, so it was a surprise to find rust stains around the bowl. Where had they come from? I had, of course, quite forgotten that a compass contains some highly ferrous elements, namely the magnets. Some corrosion had started there, but it wasn't too serious, and cleaned off easily as a brown powder. The staining on the bowl and the card wiped off well. The compass took about 750 mL of oil, which was dirt cheap at our village shop. Before filling, I tested a bottle of oil in our refrigerator at home. If it could withstand refrigerator temperatures, that was certainly more than the crew could do. No cloudiness at all! Filling a compass through the small hole provided is much easier if a syringe is used. I found that a syringe, supplied for refilling an ink-jet printer with ink, did the job nicely. There's some wobbling about required, to get the last little bubbles of air out, but this isn't hard to do. No bubbles have appeared since, no cloudiness, no rust, just a clear sharp view of the card. Now we have a compass that is as good as new, and with luck this long and sorry saga has come to an end. George Huxtable. ------------------------------ george---.u-net.com George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. Tel, or fax, to 01865 820222 or (int.) +44 1865 820222. ------------------------------