I have a hand bearing compass in a wooden box. The compass itself has a black flashlight handle and when held upright and the switch pushed, the flashlight bulb illuminates a compass card which has a 45 degree prism lens attached to it's edge so that bearings may be taken while holding the unit in front of your eye. The compass is oil dampened and has served me on and off for twenty years. I now have better units, electronics, global positioning and rdf devices...but I still like the simple hand bearing compass. It has a small access hole to add fluid if a bubble forms...which it has. I don't want to make a big production out of this by taking it to a compass repair facility...all I want to do is drain the fluid, pop open the top, clean the compass card, reseal the top and put a clear oil of some type in the unit. I am sure I can do it myself, it is dirt simple. What i need to know is what fluid do I use. Should I splurge and buy "real copass oil" or is there a homebrew that will adequately solve my very small problem? Thank you, Cap't Bob Schulte M/V Lucinda Smart Mainship 34 III

At 12:27 PM 2/20/99 EST, you wrote: >I have a hand bearing compass in a wooden box. >It has a small access hole to add fluid if a bubble forms...which it has. I >don't want to make a big production out of this by taking it to a compass >repair facility...all I want to do is drain the fluid, pop open the top, clean >the compass card, reseal the top and put a clear oil of some type in the >unit. I am sure I can do it myself, it is dirt simple. > >What i need to know is what fluid do I use. Should I splurge and buy "real >copass oil" or is there a homebrew that will adequately solve my very small >problem? > > >Thank you, > >Cap't Bob Schulte Arild writes: Sounds like the same compass I have. fortunately mine has not leaked any fluid. However I do repair compasses well as swinging them. I have found three differnt types of fluid in use. Alcohol in very old models, varsol or mineral oil, and some of the newer units have a special silicone oil. Apparently the latter has very little expansion factor with increasing temperature; thus reducing the need for an expansion chamber to compensate. When you open the fill plug you can smell what sort of fluid is used. Mineral spirits or varsol has a definite chemical smell. Unless your fliud has discoloured greatly I would be inclined to keep it and simply ad a bit to top it off with a littel more mineral spirits. If you change the fluid completely and it is not compatible with the paint used inside the compass bowl you could do more damage than good. I have seen compasses totally ruined when the owner put the wrong fluid in and it dissolved the paint. Depending on the material of the card and the ink used that too could be damaged. What prompt you to consider"popping the top" and cleaning the card. Is the card itself damaged, paint peeling or is it just the fluid which has discoloured? Cheers Arild