Sunday, 25 September 2016

Compass Installation Made Easy

Recently I came across a cruising sailboat with a beautiful new compass installation - problem was, it just didn't work. The compass had been installed in a location where the local magnetic interference was very strong, consequently the compass readings were sadly inaccurate.

A boat's compass uses the earth's magnetic flux to drive the floating card - any local magnetic forces can distort or even dominate at the compass, ruining the compass accuracy. Loudspeakers, engine blocks, electric motors, electric cables and the like can all distort the reading and in the case of steel boats the hull also has an effect.

We faced similar challenges when positioning our Raymarine EV-1 Sensor Core. This unit contains a fluxgate electronic compass, a multi axis solid state gyro and a GPS receiver.

The Sensor Core is the real intelligence that drives our autopilot system - it was important that we found a satisfactory location for the unit - the same goes for any magnetic compass. Raymarine's installation guides said it should work fine where our previous electronic compass was mounted, but we wanted to check alternate sites. In the end we measured the lowest magnetic flux field right where the old compass was mounted - out on the stainless davits mounted on the stern. Unfortunately this meant running the STng network cables another 10 meters through the boat and out onto the davits, but that's another story...

Multi Measures App

To test possible compass installation locations we used two software tools that run on the iPhone / iPad operating system. Multi Measures, by Skypaw, is an app that includes a basic Tesla meter - it graphs the field strength and gives x/y/z orientation for the magnetic flux field.

Incidentally, Tesla is the name for a measured unit of magnetic flux density, named after Nikola Tesla, a Serbian - American physicist and engineer.

What makes a good Sensor Core or electronic compass location ?  It should ideally close to the vessel center line, with access for the required network cabling and with a decent view of the sky so the internal GPS can operate. However the real driver here is lack of magnetic interference - that's the fundamental requirement.

Using the Multi Measures app we were able to wander around the boat, watching the display in real time and testing all the possible installation locations. When testing each location its a good idea to operate all the boats electrical systems, to make sure that no interference is generated when say the genset is started or when the water heater is switched on. The Multi Measures app also includes a tilt measuring function, truly useful for mounting things horizontally or vertically on boats that often have no useful reference lines.

Gemeco Marine Installers App

We also used the very capable Tesla meter included in the iNstall marine installers app by Gemeco. The Gemeco company distributes a wide range of marine electronics and NMEA network products in the USA, so this app is clearly aimed at marine electronics technicians.

iNstall includes a generous number of tools, references and calculators to make marine electronics installation a little easier - transducer details, cable sizing tools, tilt measurement and a "mix'n'match" guide for sorting out product compatibility.

The Tesla meter within the app allows you to zero the meter scale once a background level is established, then see the differences as electrical systems or machinery are activated.

Sadly for us, these handy Tesla meters proved that our inspired "alternate location" choices were not so good after all, and the Sensor Core ended up installed back out on the davits, where it works just fine.

Friday, 23 September 2016

A Record Flying Fish Haul

Carnage On Deck
Our night passage from Tobago to Grenada was memorable for setting a new record - that is, a record number of Flying Fish on deck in one evening. Ley counted 34 of the little devils initially, then we continued to find more over the next few days, secreted under lines, behind cleats and hidden by turning blocks.  What a mess they made.

To add insult to injury, one flew right into the cockpit and hit Ley on the back - lucky fish, she threw it overboard right away for another chance at life. 

As dawn broke our viewing of the beautiful Grenada coastline was interrupted by the discovery of slimy carcasses all around the boat - and in these numbers they quickly became very smelly in the sun.

Thursday, 22 September 2016

Boat Shopping In Grenada

Loading The Important Things In Grenada - Italian Wine By The Box Load
Two weeks ago we sailed overnight from Tobago to Grenada, an overnight down-wind romp for 80 nautical miles that had us approaching the south coast of Grenada just after dawn. By 07:30am we were anchored in Prickly Bay and by 10:00am we had completed the friendly Immigration and Customs formalities - which then let us get down to the nitty gritty of this voyage - the shopping ! We had pre-ordered a range of spares and equipment from Budget Marine in Grenada, as they were around 25% cheaper than here than in Trinidad.

New Walbro Fuel Pump Installation
It took some days to gather all the parts, and we were able to farewell our good friends on Ceilydh, who are heading for the Panama canal and the west coast of Mexico As our parts trickled in to the dealer we started work, installing what had been delivered.

So, a new Walbro FRB-13 electric diesel fuel lift pump was fitted, the old unit had done 3500 hours and was starting to fail. With associated plumbing changes, this took a couple of days to complete. The pump is used for priming the fuel system on the Cummins main engine, and for transferring fuel to an aft tank that serves  the Northern Lights AC generator.

Another two days disappeared installing a new Raymarine digital radar cable in the mast, not an easy job, but essential since the old cable had become intermittent. Note to Raymarine - your original analog cable lasted over 13 years, the new digital cable served for only 20 months. Not good enough !

We also continued another project that had started back in Tobago, which was refinishing and painting the front of the mast where the spinnaker pole track is fastened. Corrosion had set in around the pop-rivet fastenings, so we had removed the track and sanded back where necessary to bright metal, then epoxy primed the surfaces.

In Grenada I started on the high build and finishing priming, a tricky task as most of it had to be done sitting in a bosuns chair, hanging on a halyard from the top of the mast. Of course the anchorage was quite rolly, so bruises and strained muscles were the order of the day, every day.

Ley is getting plenty of shoulder exercise winching me up and down the mast.

We found Grenada to be quite sophisticated, certainly compared to Tobago, yet it remains friendly and quite laid back. There are literally hundreds and hundreds of cruising boats anchored around the island, and probably several thousand more stored for the season in the many boat yards around the coast, packed in like sardines with only inches between them. I honestly have never seen so many boats in one place in all my life.

Remora Attack - More Information ...

My experience being hassled by 12 desperate Remora fish in the ocean off the coast of Suriname is apparently not so rare . Our friends on the catamaran Ceilydh came up with some research that shows it is common when a large shark kill has happened in the area - basically the lack of shark hosts means the Remora fish outnumber the hosts, and the results are not pretty.

The BIG One- Fast & Hungry
We commented on the problem after I was hassled between Suriname and Tobago - then our friends on Ceilydh were prevented from swimming off their boat in Tobago - one even bit Evan on the toe.  By this stage we were both still "hosting" just a few Remora. Just google "remora attack" to learn more about this.

Unfortunately for us we still had with us the BIG One, lurking under the boat and definitely not afraid of us. I did think about starving the critters out (surely they'd leave?) but the thought of not pumping the heads for a few days was not a good one (yes, they eat everything that comes out of the host).

Fortunately, by the time we had sailed from Tobago to Grenada we had lost the aggressive creatures and were left with just one smaller, shy creature that disappeared whenever we swam off the boat.  About time - at last we could swim and enjoy the water.

Wednesday, 7 September 2016

Diverging Wakes

Ceilydh anchored in Prickly Bay, Grenada
Crystal Blues and Ceilydh sailed away from Malaysia bound for Sri Lanka within a few days of each other, back in February 2015. Since then our wakes have crossed many times, across both the Indian and Atlantic Oceans. Onward we sailed, sometimes diverging, other times sharing anchorages, marinas, cultures and each others lives. Last week we sailed overnight from Charlotteville in Tobago to Prickly Bay in Grenada - our last passage together. What great friends and companions the crew of Ceilydh have been.

Crystal Blues anchored out the back in Prickly Bay, Grenada
Diane's work as a writer opened up many interesting opportunities in the countries we visited together. Evan is a naval architect, so there was always a lot of boat talk. Maia blossomed in the time we knew her - changing irreversibly into the beautiful and confident young woman she is today.

It did help that we are all passionate about live music, fine wine and good food. We shared the same simple pleasures when discovering a market where there were more than a few choices for foods we craved. Here in Grenada the five of us roamed around the two world class chandleries, like children in a toy shop, ogling over boat stuff that we had been looking for several countries back. We also shared the same culture shock when anchoring in Prickly Bay, Grenada - looking at the forest of masts in the bay, with even more spilling onto the crowded hardstand.

Most of all we just spent time together. Laughing, cooking, exploring, shopping, swimming, celebrating birthdays, helping each other out along the way. A fine and lasting friendship blossomed across two oceans.

Ceilydh sailed away yesterday to Curacao. Diane, Evan, Maia and the feline bosun Charlie are excited to be slowly heading home to Canada. Crystal Blues remains anchored in Prickly Bay, Grenada, waiting for a few boat parts, before we sail on to Trinidad and haul out. Next year we plan to explore the USA via the inland lakes and waterways.

We remind ourselves how lucky we are to have shared this special time together, for it was a bitter sweet parting. Our wakes may have diverged, but not our hearts - we'll meet these special people again.

Diane, Evan, Maia and Charlie preparing to depart Prickly Bay, Grenada. Maia, we are going to miss your Key Lime Pies!