Bubble Trubble

From memory,  it was La Paz Mexico that the boats Plastimo Olympic 135 compass developed a small bubble.  But it was during the heavy rolling below 50 S in my approach to the Horn that the bubble got bigger and bigger.  Fortunately the size of the bubble did not increase after my arrival in Fremantle,  but the matter had to be dealt with because the card was now very difficult to read.  Also, neither compass light was working.

One thing about boating is that it forces you to learn new things.

I removed the compass knowing nothing about it beyond how to change its lights.  I didn't know what fluid would be required, or how/where to inject it.

I got various suggestions about the fluid: glycol, baby oil, kerosene, and "compass oil", whatever that is.

At Yacht Grot Roger produced some clear fluid in a clean jar that he said was highly refined kerosene, with the assurance that it would mix well with the existing fluid in the compass, sparing me the trouble and expense of fully draining it.

Big Bubble in Compass

Rubber Membrane

Stephen arrived for an overnight visit on Sunday morning and soon we began our work.  I had dismantled the compass enough to identify the filling screw, which I exposed after cracking the epoxy seal on it.  On his advice I had also purchased plastic syringes at the chemist.

We worked for hours but try as we may we couldn't shrink the bubble beyond a certain point.  We stopped our effort with the thought of perhaps immersing  the entire compass in fluid to ensure that we could evacuate all of the air.

I was a bit despondent because even if we could shrink the bubble there was no guarantee that it would not return due to some leak somewhere.

In the afternoon Stephen helped me to join Ebay and link it to my Paypal account then we did a search for another compass.  Soon we identified a pitfall: There are at least 3 versions of Plastimo 135 compasses,  the "Offshore", "Horizon", and "Olympic",  different from each other and at different price points.  It took a while to confirm that I wanted the "Olympic", which was priced on Ebay at just over $620, a bit rich for my blood.  Later that night I found one Queensland priced at just under $400.

On Tuesday morning I  got back onto the web to find the Queensland company's contact information and stumbled on a compass at Whitfords Marine near Fremantle for $349.  I  phone up, they had one in stock, and they agreed to hold it for me.  Two hours later Stephen and I arrived, put the new compass and my old one side by side, and confirmed that they had identical specifications.  I purchased the compass and two spare globes.

Old and New Compasses

From our web searches we had concluded that "mineral oil" was the most likely compass fluid.  I needed more fluid because I had used all of the fluid that Roger had given me.  We stopped at Bunnings on the way home and found a liter of "paraffin oil" that seemed suitable.  It was clear, of light viscosity, and had  a neutral smell - certainly not of kerosene.

Yesterday morning I resumed work  on the old compass because I didn't want to simply throw it away.  I started off  by putting the compass in the freezer for 2.5 hours on the theory that the fluid would shrink, making the bubble bigger, allowing me to expel more air, then the remaining bubble shrinking as the fluid got warmer.  The flaw in this theory is that we discovered a rubber fluid-filled membrane at the base of the compass whose purpose was to allow for expansion and contraction as the temperature varied.  So how could the bubble size vary with fluid temperature given that the rubber membrane would do the compensating?

What finally did the trick, in my opinion, was that I discovered that the end of the syringe could seal the filling hole quite effectively with only a little pressure.  This enabled me to overfill the compass while I watched the rubber bladder expand, then allow the fluid to spit out when I released the syringe, bringing out bubbles of air with it.  After doing this a few times I reduced the bubble to the size of a match head, but try as I may I could not completely eradicate it.

Nevertheless the compass is now quite acceptable for use and had I not been able to source a new  replacement I would have reinstalled the old one, hoping that the bubble would not increase in size over time.

Spot the Bubble

My plan is to set up the old compass as an adornment in  my house which is already laced with nautical decorations.

I cannot complain about the compass problem.  It is with little doubt part of the Pachuca's inventory when she was launched in 1983.  The new compass has a 5 year warranty and will probably see me out, unless I live beyond 106.

Regarding the failed lights, I discovered that the wiring to the compass was delivering less than 3V.  I tracked the  problem back to the grounding in the electrical  panel.  The grounding had been set up before my time, to a white wire that was part of a bundle of white wires that would have been difficult to track.  I elected to earth the wire directly to the ground side of the switch panel and began to get over 13.5V at the binnacle.