Compasses -- What do I do about a Bubble in my compass?

sketchrbob

The First Compass Question is what do I do if I have a bubble in my compass?

The obvious answer is to fill it. However, what should we use to fill it? and will it leak out again? The oil in compasses is a special oil of a definite viscosity and supplied by the manufacturer. Ritchie uses one grade of oil for all their compasses while Danforth uses a No.35 in their regular compasses and a No. 50 (heavier weight) in their high speed compasses.

Many of the Marine Supply stores sell small quantities of compass oil and that would be the best source to fill the compass. I used to keep my oil in the freezer so that it would condensed to its smallest volume. If you are just adding a small amount you would not need to do that. Find the fill screw on the side of the compass and remove it. Hold the compass so the fill hole is upper most. You can add the oil with a medicine dropper or a short length of plastic tubing using the syphon method. Yes, it does not taste very good if you start the syphon by mouth, but spit it out and rinse out your mouth and it won't hurt you. I started all my syphons that way for 18 years and I am still here so it can't be too poisonous!

What if you can't find any compass oil for sale? Well No.1 Kerosene is probably pretty close and should work ok. I had a customer call me from the Canary Islands once and wanted to know what to use. I told him to use Gin and I guess it worked ok. Sad way to use the gin though. Whatever works!

You may find that after filling the compass there is a small bubble that still remains. Try rocking the compass to get the air bubble to pop out of the fill hole. If it does you may have to add a small additional amount of oil. You may have to go through this procedure several times. Yes I know it can be frustrating but stick with it.

Why do compasses get bubbles in the first place? The dome sits on an "O" ring and with the passage of years the "O" ring gets tired and with cold weather the oil tries to contract and pull air in past the "O" ring causing the bubble. So if you are successful in filling the compass it is a good idea to remove the compass from the boat during the cold weather. The other solution is to send the compass back to the repair center and have a new "O" ring installed.

Most of the compasses today are Ritchie and that is a good thing as they make one of the best compasses. They have their own repair department. I know it is good because I went through their repair training course. They make all their own compasses at their modern plant in Pembroke Massachusetts. Their address is E.S. Ritchie & Sons, 243 Oak Street, Pembroke MA 02359. Phone is (781) 826-5131. Ask for the repair department. They can give an estimate of cost and tell you how to ship the compass. If it is a Danforth Compass you can call Viking Instruments. Phone is (781) 331-3795. I believe Dirigo Compasses in Washington State may repair compasses but you west coast sailors should know more about that.

What if you don't do anything about a bubble in your compass? Well actually it will not do any harm and will not affect the accuracy of the compass. If the bubble is small and does not bother you, live with it. It may grow larger over time, but you can deal with that later.

That is enough to start this subject off so we are ready for your comments, questions and sarcastic remarks!

Very Happy

Captains Cat

Sea Wolf · Posted: Thu Oct 06, 2011 3:09 pm Post subject:

I used clear mineral oil from the local pharmacy to eliminate the bubble in the compass on my Sea Ray. Seems to work fine. I read that some of he much earlier compasses used alcohol as a fluid.

I suspect that heating from the sun and the consequent fluid expansion is a major culprit in compasses leaking fluid and air coming back into the compass.

To that end, I made a cover from the one above out of a white PVC end cap for a 6 inch PVC irrigation pipe. I lined the inside near the lip with felt for a snug fit, and added small eyelets to cinch it down to the dash with a small diameter bungee cord. Hasn't leaked yet!

If you take the compass apart, be careful not to cinch the screws up too tight, as the whole compass, outside of the magnets under card itself and the corrector magnets, is plastic! ("Snap, crackle, and pop!") (Remember that?) Laughing

Joe.

mailbox101 · Posted: Thu Oct 06, 2011 4:53 pm Post subject:

A culinary tool, caller a 'flavor injector', works well for getting oil/alcohol into the small fill-hole without making a mess, or getting tiny bubbles.

sketchrbob · Posted: Thu Oct 06, 2011 5:02 pm Post subject:

Joe: You are right about using alcohol for compass fluid. In fact old sailing ship skippers sometimes had a problem with crew drinking the alcohol from the compasses in the lifeboats. The trouble using alcohol as fluid was that it had a low viscosity, and the card would spin or wander endlessly. Your idea of using the mineral oil was a better one.

The expansion of the fluid from heat from the sun may cause a little leakage but will not cause a bubble because the pressure will keep the compass full. It is when the oil contracts from the cold that the air is pulled in. The heat from the sun tends to cause crazing or tiny cracks in the dome. The newer domes are make from a better quality of plastic and the problem is not quite as prevalent. Your idea of making a compass cover is a good one. I should have mentioned it as I made them or bought them for all my boats. Thanks for bringing it up!

Bob

Captains Cat · Posted: Thu Oct 06, 2011 7:18 pm Post subject:

Bob, I hope you don't mind, I shared your name/info over on the Ranger Tug site (Tugnuts). They seem to be having some compass issues, when they're not worried about the temperature in their wine coolers Mr. Green

. Sorry TNs, not fair, just having fun! Hope we helped you!

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Us Brats have a compass expert on our C-Brats site that we'll share with you. See the thread http://www.c-brats.com/viewtopic.php?t=16774. His screen name is sketchrbob and he's been doing compass things for years. Feel free to ask him questions there or invite him to join the tugnuts. He seems to be glad to share his expertise. Enjoy!

Charlie
TC255s
CAPTAIN'S CAT
and
THATAWAY
-------------------------------------------------------------

Charlie

oldgrowth · Posted: Thu Oct 06, 2011 7:35 pm Post subject:

When I have something like a compass to fill through a small hole, I use a hypodermic needle w/syringe to fill it. If you can get the needle into the fluid, it will push the air out as you squirt the fluid in. You do need a needle that is smaller than the hole so air has room to escape.

Dave

www.marinautboats.com

sketchrbob · Posted: Sun Oct 09, 2011 11:31 am Post subject:

Just found that Hamilton Marine sells Compass Oil by the pint. Go to hamiltonmarine.com. catalog page 35. Part #RIT-SH-0091. Order #128679 Price is $7.79 for the pint.

Next topic : What is the "Best" type of compass for a C Dory? will be posted next Thursday.

Bob W.

oldgrowth · Posted: Mon Oct 24, 2011 4:07 pm Post subject:

Bob – it is not a compass but a Suunto clinometer PM-5/360. I have had it for 25 m/l years but it is starting to stick. Actually it is stiff. The scale will not move with a small change in the angle of the clinometer. It use to be accurate to within ¼ degree. Now it can be as much as 7 degrees off. Is this something you can fix? I was going to send it back to the factory for service but if you think you can fix it, I would just as soon send it to you and support a fellow C-Brat.

Dave

www.marinautboats.com