Robert I think your compass may be equipped with an expansion chamber (bellows). I was planning to fix the small bubble in mine and my plan was to put some mineral spirits in the deep freeze at -20C overnight and put the compass in the normal refrigerator freezer at -4C to "shrink" the fluid and then to fill to the top with cold (-20C) mineral spirits. Then as the compass body and the filler fluid warmed to outside summer temps the filler fluid should expand into the bellows and bingo the compass bubble should be gone...So it developes its own pressure when warmed because the fluid volume increases as temperature increases while the volume of the globe stays close to constant. The pressure produced on expansion serves to force excess fluid into the expansion chamber. I was planning to use ordinary hardware store Varsol which is not much different chemically from the Isopar that Rich mentioned. Besides I don't need to add that much and at least it would mix well with Isopar.
Dwight Veinot Alianna C&C 35 MKII Head of St. Margaret's Bay, NS On Wed, Nov 20, 2013 at 11:23 PM, Robert Abbott <robertabb...@eastlink.ca>wrote: > My +30 year old Danforth is filled with mineral oil, at least that's > what the gentleman said he filled it with when I had it repaired a few > years back. He said it is filled under pressure and he actually kept it > for 24 hours to monitor for any leakage. > > Maybe the reason he advised to take it off the boat in the winter is that > mineral oil freezing temp is -30C....I can't remember when we had it that > cold here in Halifax. > > Nevertheless, my old Danforth will probably spend another cold winter on > the boat. > > Bob Abbott > AZURA > C&C 32 - 84 > Halifax, N.S. > > > On 2013/11/20 10:36 PM, Rich Knowles wrote: > > Don got me thinking and is absolutely correct. I misread the Ritchie > information and said the compasses contained alcohol. Wrong. Apparently > Ritchie compasses are now filled with Isopar L, a "synthetic > isoparaffinic hydrocarbon solvent" made by Exxon Mobil. According to > Ritchie's website, they switched to this in 2001. A bit of research > revealed that the Isopar family has a wide variety of uses as solvents for > paints etc. > > The freezing point of this Isopar Lis stated to be -60C, still well > below any temperatures that most of us will encounter. > > Man, that crow has a taste.... > > Rich Knowles > INDIGO LF38 > Halifax, NS. > > On Nov 20, 2013, at 5:03 PM, Don Newman <donrnew...@gmail.com> wrote: > > More expensive compasses tend to use a mineral oil for greater dampening. > > > > _______________________________________________ > This List is provided by the C&C Photo > Albumhttp://www.cncphotoalbum.comcnc-l...@cnc-list.com > > > > _______________________________________________ > This List is provided by the C&C Photo Album > http://www.cncphotoalbum.com > CnC-List@cnc-list.com > >
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