What is the fluid in floating compasses ?

[Idle]

A large air bubble appeared in my Horizon Compass. I did not take it out yet but I presume it must have a filling hole. To avoid rusting and weed formation under the sun what kind of a fluid is added?
Idle

[accomplice]

I don't know about horizon, but usually compasses are filled with a light oil which dampens motion. Some use lamp oil which is highly purified kerosene.

[DefinitelyMe]

You can also use vodka :-)

[a64pilot]

Cmon guy's they are called a "Whiskey compass" what do you think is in there?

Seriously the correct fluid is easy and cheap, there is also a diaphragm in the compass that allows the fluid to expand and contract due to temp.

AIRPATH COMPASS FLUID ( 1/2 PINT & QUART ) from Aircraft Spruce

[Jason Flare]

Originally Posted by DefinitelyMe

You can also use vodka :-)

Yes. But after you add vodka, what do you put in the lamp?

[Cormorant]

I remember reading a book called The Tuntsa, in which the crazy alcoholic captain of a boat making a trans-Atlantic voyage smashes the compass to drink the alcohol in there. . . .

[a64pilot]

Before I removed it, I would index it, maybe something as simple as a pencil line so you could put it back exactly like it was

[dalewils]

mineral oil will do but in a pinch i had to use water and it worked fine
but yeah get the quantity right shuld be around 70ml ? check on line
alcohol will evaporate BTW

[bsurvey]

when I sailed finns I used a small compass 3 inch card compass. the fluid inside was to not very viscos and the compass card bounced around a lot so I could tell lifts from headers. I emptied it out and filled it with baby oil as it is thicker and the card was not quite so lively. I still have the compass to this day and it works fine

[Scaramanga F25]

I have used and would use proper compass fluid.
You may need a syringe or an eye dropper.
Do not over tighten filler screw nor drop O ring.

[woc]

Just stop by any West Marine store, they sell it. it is called " Ritchie SH- 0154 Compass fluid and come is one pint bottles. Get a syringe at the same time or else it will be difficult to get all the air out. I just did this on my compass and it worked fine. Haven't tasted it but at the price I can afford the real stuff.
Good luck

[Captain Bob]

The fluid in most modern compasses is Isopar, a synthetic fluid available from most compass providers It should be placed under a vacuum to remove any air bubbles. This in turn allows the fluid to absorb any minute amounts of air entrapped while refilling.

The most common problems causing air bubbles to appear in the dome are a cracked rubber diaphragm or a crack in the plastic dome. The diapphragms stiffen and crack with age. This is not a do-it-yourself job for most people and some compasses ( like most Plastimo) cannot be repaired. Some very old compasses (like C. Plath) were indeed filled with a mixture of grain alcohol and distilled water.

A good source for rebuilds is J. Gordon & Co. in Annapolis, MD. Call them at 410 263-0054.

[Scaramanga F25]

I forgot to add: I refrigerate the compass before adding fluid in order to contract fluid before adding more. This method got rid of the last tiny bubble.

[NSpence]

Originally Posted by Scaramanga F25

I forgot to add: I refrigerate the compass before adding fluid in order to contract fluid before adding more. This method got rid of the last tiny bubble.

FYI Scaramanga F25 Fluids do NOT contract or expand.

[davemachado]

My guess would be "white (clear) mineral oil" or "polyethylene glycol".