compass fluid/oil

[centerline]

the bulkhead compass on my boat is a plastimo contest. it is an older compass but it has been covered most of its life so it is in excellent condition EXCEPT for its low on oil. I would leave it like it is except for when I trailer it and hit a bump, it sometimes gets a bubble under the card and tilts it so that it becomes unusable until the bubble works its way out..... so I have it out of the boat now and I am wanting to refill it but I dont know what to use. the fluid in it is fairly thin and more like turpentine rather than oil. I have not uncapped it so I am not sure if it has any distinguishing odor. does anyone here have experience refilling compasses that could give me some guidence? are all compass oils compatable? what is the most likely fluid that would be in this compass, given the fact that it is so thin? thanks.....

 

[Maine Sail]

Some brands used a light weight mineral oil and most others used Odorless Mineral Spirits. You don't want to used the wrong fluid as it can change the design characteristics for damping. Put some one your fingers and feel them. The put some mineral oil and mineral spirits on your fingers and do the same. Pretty easy to tell the difference between mineral oil and spirits.

With many compasses flip it over and remove the plug and re-fill with Ritchie Compass fluid. You may have a bad o-ring on the drain plug or a bad o-ring sealing the globe.

Until 2001, Ritchie compasses were filled with a high quality odorless mineral spirits. Ritchie now uses a fluid called Isopar L® that has similar properties but some added benefits over odorless mineral spirits. These two fluids can be mixed together.

Ritchie began using Isopar L as dampening fluid during 2001. This fluid is a high-purity isoparaffinic solvent very similar to Odorless Mineral spirits.

Ritchie changed to this fluid because it has a higher flash point and conforms to most of the world's shipping regulations. It is important to note that some other manufacturers use Isopar M as their dampening fluid. I know ISOPAR M should not be used in Ritchie compasses but don't know about Plastimo. Hamilton Marine sells Isopar L/ Ritchie Compass Fluid but any hardware store sells odorless mineral spirits.

Ritchie also suggests: "Dampening Fluid - Be sure to subject the fluid to a vacuum equivalent of 28 inches of mercury for a minimum of 15 minutes before sealing it in the compass. This step prevents the formation of a bubble in the fluid due to temperature changes."

An old trick to get around that, which often works very well, is to stick the Isopar L or Odorless Mineral Spirits in the freezer for a while then fill the compass with it.

 

[Alan Johnson]

Use orderless mineral oil. Available at your local big box hardware store

 

[rgranger]

An old trick to get around that, which often works very well, is to stick the Isopar L or Odorless Mineral Spirits in the freezer for a while then fill the compass with it.

Main

That is interesting. The solubility of a gas in a liquid is directly proportional to pressure and inversely proportional to temperature. However oxygen and nitrogen are not very soluble in mineral oil at all to begin with so getting the mineral oil degassed should be easy. The vacuum you mentioned would serve that purpose. I suspect your trick works by increasing the density of the liquid and then when it reaches ambient temperatures in the compass, it is actually under a slight positive pressure. That keeps any dissolved gasses in solution.

I wonder if your trick would be enhanced further if you first heated the mineral oil on the stove top to drive out some dissolved gasses, then sealed it in a bottle to keep out any air, and then chilled it in a closed bottle to increase the density before adding it to the compass?

 

[Benny17441]

The missing fluid must have leaked out somehow so just refilling may be at best a temporary solution. I have learned that compass work is not a do it yourself proposition and best left to the proffessionals if you seek a lasting repair on a quality unit. Just replacing gaskets, "O" rings and glass/plastic dome does not insure you will get a good seal, the unit must be pressure tested prior to filling.

 

[Ken Palmer]

The missing fluid must have leaked out somehow so just refilling may be at best a temporary solution. I have learned that compass work is not a do it yourself proposition and best left to the proffessionals if you seek a lasting repair on a quality unit. Just replacing gaskets, "O" rings and glass/plastic dome does not insure you will get a good seal, the unit must be pressure tested prior to filling.

Can you give us some names of companies that re-fill compasses?

 

[Benny17441]

Call the manufacturer of your compass and get a list of their authorized service dealers for your region. If there is none within a convenient distance radius You can probably arrange with them to have the work done by the factory repair shop. Once a compass looses fluid it is likely the job will entail more than a simple filling. It will probably require stripping down and at minimum replacing gaskets and seals, pressure testing and filling. If the dome is scratched or cloudy and the card is fading this would be the time to replace them. The repair on any compass that has lost a significant amount of fluid should be considered a rebuild. If there is only an air buble I would learn to live with it until the work was really needed. To uncap a compass just to add a small amount of fluid could require that work to be performed sooner than if just left alone. I'm no compass repairman and these recommendations are just based on my experience with them.