Skipper’s Tips #17 – Magnetic or True

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I’m sure most boaters or walkers or anyone who navigates their way around using charts or maps will have come across the situation where their compass is pointing one way and their maps or charts are pointing in a slightly different direction.

The reason for this, in simple terms, is that the molten core of the earth, which is constantly moving, is what compasses point at.  However, when you look at the globe from a human perspective, it has been drawn with the North Pole at the top and the South Pole at the bottom, a slightly skewed axis and to add insult to injury, the beautifully drawn land masses are not quite in the position that our trusty new GPS gadgetry now correctly indicates.   Here’s an interesting observation to chew on; if you went out into space and looked at the world, how would you know which way is up? Is the North Pole actually at the top?

I digress…

Obviously, if we are to sail around without bumping into things we need to work out how to work on the same page as the compasses we are utilising.  What we do, is allow for the difference in opinion (Variation) and once applied to the (True) or unadjusted heading, we end up with a (Magnetic) heading figure.  The story doesn’t end there though.  Stick a compass on a boat and all the electronic and magnetic forces on the boat will have a further effect on the compass, confusing the ‘poor dear’ even more, this we call (Deviation).  Making an allowance for the Deviation inaccuracy of the compass gives us the most accurate heading and is called a (Compass) heading.

Do not despair. When you buy a new boat, a compass adjuster will get on board and eradicate as much of the Deviation as possible.  The bit that’s left will be listed on a compass Deviation card so you can allow for it when navigating.  Beware though.  If you change any electronic equipment, or bring items onto your boat that have any electronic or magnetic properties, they will have an effect on the compass and it will have to be ‘swung’ again!

By now you must be starting to wonder how you’ve managed to navigate safely between ports without bumping into rocks and chunks of unexpected land. The answer, of course, is that we all readily use the chart-plotter/GPS equipment that’s become almost as intrinsic as the hull!  The chance of this equipment failing is remote and I have touched on this in another tip but if it were to fail or cease to operate correctly we will have to deal with Variation and Deviation before we can start to steer a course by the boat’s compass.

So, how do we work with Variation and Deviation?  Importantly, you must remember to make these ‘allowances’ in a specific order.  Allow for Variation first and then Deviation. You will also need to decide how you apply the correction.  When dealing with Variation this correction is essentially adding or subtracting the appropriate amount of degrees difference between what the compass is indicating and what the local Variation is shown to be on your chart as either degrees (West) or degrees (East)

Doc 3 Sep 2017, 12-37This is an example of a compass rose on a chart.  The Magnetic Variation shown is 2 degrees, 45 minutes West, correct in 2006.  Each year, this ‘error’ is decreasing by 8 minutes.  There are 60 minutes in a degree, so for 2017 – 11 years on – that’s a reduction of 1 degree and 28 minutes.  Therefore the Magnetic Variation in 2017 is 1 degree and 17 minutes West. Yes, there will come a point when the error disappears completely and then starts to become an East Magnetic Variation.  When I first started teaching, the Variation in parts of the Med was just under 2 degrees West and the last I saw it was almost zero – Point & Go!

N.B. Please remember, Magnetic Variation is nothing to do with whether you are going in a Westerly or Easterly direction, it is actually about your position on the globe relative to that molten core of the Earth which we spoke about earlier.

The question now is, how do we know whether to add or subtract these degrees of Variation or Deviation?  I don’t doubt that there are many different ‘aide memoirs’ but the one I favour, naturally, is the one I made up myself.  If you are calculating from True (shown on the chart) to Compass (the heading you are going to steer to by the ship’s compass) then any Variation or Deviation you allow for that is West must be added.  In other words True To Compass Add West – TTCAW.  It therefore follows, that any Variation or Deviation that you encounter when going from True to Compass that is East must be subtracted; the opposite, see?

Furthermore, when you are calculating from Compass to True, as you might when taking a Magnetic bearing with a hand-bearing compass, you would add East and subtract West. Clear as mud isn’t it?  Have a look at the table below, which has some examples.

Just to reiterate, don’t fall into the trap of thinking the direction you are pointing your boat in determines whether the Variation or Deviation is West or East.  The Variation figure comes from the compass rose on your chart and the Deviation figure from your boat’s deviation card.

True    Variation        Magnetic       Deviation      Compass

231        6 W                  237                  2 W                  239                             add West

079        3 E                   076                    0                     076                             subtract East

147       4 W                  151                   1 E                   150

013       2 E                    011                   2 W                 013

348       2 W                   350                  1 E                   349

To remember the order try,  ‘True Virgins Make Dull Companions’.  Alternatively, if that’s too racy for you, remember the reverse order with,  ‘Cadbury’s Dairy Milk Very Tasty’.

This has been another Captain Corbett’s Adventure.  If I’m not on Jersey teaching a private tuition Day Skipper theory or Yachtmaster theory course, then I’m either spending time with someone on their boat, giving them the confidence to take their boat out with their family and friends on board or I’m off somewhere exotic delivering a boat. Either way, I’ll write it up and put it on the Blog for you all to see, so keep popping back to see my most recent adventures.

 

 

Giving you confidence

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So, my contract in Italy on the 76 footer has finally come to an end and I am now back on Jersey full time.

Operating as a true freelance captain and RYA instructor again, I am now fully available to offer a whole range of skipper services to anyone who needs help building the confidence you need to safely take your friends and family out boating with you.

  • If you want to brush up on some rusty skills or you simply want a skipper to handle the boat while you enjoy the ride, then I’m your man
  • If you are studying the theory and it’s not making sense, then I’m your man
  • If you need an ICC (International Certificate of Competence) assessment, then I’m your man
  • If you need your boat delivering somewhere, then I’m your man
  • If you want to take clients out to give them a good time, then I’m your man

I’ve recently taught two separate Yachtmaster Theory candidates who were taking distance learning courses and they both tell me that they truly benefited from spending a few days on a one to one basis with me prior to taking their exams.  So whether that’s you or you’d just prefer to learn about the theory behind navigation, safety and etiquette on the water, give me a call and we can discuss times to suit you.

With summer truly on the way, it’s time to get the boat washed off and start planning those trips.  However, if it’s been a while since you were last out on the water, you might be feeling a little low in the confidence stakes.  Spend a few days buzzing around the marina with me and your confidence will come racing back and you’ll be good to go.  If you are intending to visit France this summer and you don’t have an ICC, then I can take you through the requirements and assess you as we go – much easier than taking a test I’m sure!

Perhaps you just want to sit back and let someone else take the strain.  Leave the driving to me and you can enjoy the time relaxing with your family and friends instead of worrying about tide times, mooring on an unfamiliar berth or going to that marina you’ve never been to before.  Impress your clients with a trip out on your boat and let a professional captain and crew make it work seamlessly for you.

I have many, many years of world wide cruising experience and teaching under my belt – let me share this with you and give you the confidence to properly enjoy your boating.

Skipper’s Tips #12 – Fog

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The first time I encountered fog on a boat was in the early days of my teaching career.  We were on the school boat Alpha, just having passed Calshot Spit in the Solent.  I could see the fog ahead of us and determined that we should continue towards our destination; fully expecting it to be a narrow bank of mist which we would soon pop out of as we approached Cowes.  Behind us was brilliant sunshine and in my naivety I wasn’t prepared for just how dense and disorientating it was going to be.  We all had life-jackets on, the radar was working and as we entered the fog bank we slowed down to tick-over.   Despite following the correct procedures I have to hold my hands up and admit that I found myself in a very uncomfortable position.  Everyone on board was relying on my experience and skill to navigate us safely through the fog to Cowes and yet my stomaching was churning – I couldn’t see a blinking thing and all I could hear was the engines of the Red Funnel fast-cat, seemingly headed directly towards us.

My training kicked in and after a sustained squint at the chart plotter it soon became apparent that the fast-cat was actually a mile to the south of us and not on a collision course after all.  With no particular reason to go to Cowes that day and glorious sunshine behind us I made the decision to retreat and we were soon out of the fog and heading for Southampton Water to do some Man Over Board practice instead.

 

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No matter where you do your boating, fog or reduced visibility situations will arise at some time or another.  Don’t forget, that a heavy rain shower or even snow can make it exceedingly difficult to see and truly disorientating, so it is supremely important that as you approach an area of reduced visibility, you make an accurate note of your position and indicate this on your chart: all your subsequent navigation will be based upon this position fix so get it right.

Big shipping, the kind you really don’t want appearing out of the gloom directly in front of you, will be staying to the main shipping channels, it therefore makes sense for you to run outside these channels but only if it is safe to do so, obviously you must check your position on the chart before moving to the shallows.

A really handy tip is to follow a suitable contour line around the coast until you come to a safe harbour. Once you are within 100 yards of the entrance you can normally make out the entry channel markers; get yourselves safely tied up and wait for the visibility to improve.

For those of you with radar on board, the processes of navigating in reduced visibility and avoiding other vessels are that much easier.  However, you are obliged to know how to correctly decipher the information presented to you by your radar screen; if you were to have an accident based on this information and you had misinterpreted what you had seen on the radar screen, you could be found liable for the accident.

 

Here are some of the procedures you might employ when heading into an area of reduced visibility:

  • As soon as you see the weather deteriorating, take a fix
  • Make a note in the ‘Deck Log’ and on your chart of your position
  • Slow down and move outside the main channel if you can
  • Turn on your navigation lights and navigation equipment
  • Make sure everyone is wearing a life-jacket and the life-raft is ready to deploy
  • Sound the appropriate signal for your vessel every two minutes
  • Keep alert for the sound of approaching vessels

Over the years I’ve found myself enveloped in varying degrees of fog, walls of rain and snow storms.  I have to tell you it’s not much fun.  You have to put a lot of reliance on your equipment and if you’re not that confident with using radar this can leave you very dry mouthed.  If you keep your head and follow the procedures listed above you will, most likely, be fine.  I would encourage you to attend a radar course when you get a chance as there have been many instances of people misinterpreting their radar and ending up colliding with other vessels.  Remember that some of what you learn in the COLREGS is based around vessels being in sight of each other – when you are in reduced visibility you are no longer in sight of other vessels.  In situations like this your immediate reaction to avoiding a collision might not be to turn to starboard but to turn to port instead! 

This has been another Captain Corbett’s Adventure.  If I’m not on Jersey teaching a private tuition Day Skipper theory or Yachtmaster theory course, then I’m either spending time with someone on their boat, giving them the confidence to take their boat out with their family and friends on board or I’m off somewhere exotic delivering a boat. Either way, I’ll write it up and put it on the Blog for you all to see, so keep popping back to see my most recent adventures.