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.

 

 

Here we go again…

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Just before Christmas 2013, Lynn, my chief number one crew and I headed off to a small island off the Brittany coast. We were going to tackle the obviously impossible task of moving a boat up the Bay of Biscay in a tiny gap in the disastrous weather we’d been suffering for weeks. When I wrote about the trip I entitled it, ‘What price a life?’ as it made me think very seriously about the merits of going out to sea when it is rough.  Well, would you believe it, here I am again to tell you about the same route, the same model of boat but much, much better weather?

One of the things I learned about this trip the last time I made it, was that accessibility to this section of the French coast line is not easy using public transport. I don’t think I’ve ever used so many coaches and trains getting back and forth from a boat.  Fortunately, this time it was quite straight forward but still, more involved than just getting into a car and driving to the marina. I set off on Friday evening, on the ferry to St Malo.  Staying overnight in a hotel opposite the station made it easy to stroll across the road the next morning and virtually walk straight onto the waiting train without so much as adjusting the speed of my step. Less than an hour later and I was in Rennes. The next train got me to Nantes and then a coach took me the rest of the way to Noirmoutier.  Not bad really but when you consider I started travelling on Friday evening at 18:30 and it was now 16:30 the following day, it does seem like a long journey for such a short distance across the globe, especially when we keep getting told how small the world is these days.

So, Bill, the owner of the new Swift Trawler 50, was waiting to greet me when I arrived. As we walked to the boat, we discussed the plan and the weather and came to an amicable agreement that we would go ‘balls out’, given the favourable weather conditions, to get to Guernsey on the second day to collect Bill’s wife.  Jane was planning to come across on the ferry from Poole and complete the last leg with us.  Personally, given the distances involved, I would have preferred to have split the trip into three legs, allowing a day for each but Bill was on a mission and as long as it’s not dangerous, I’m happy to help.

The following morning, at 06:20 sharp, we left the marina on the first leg of our trip.  It was supposed to be 06:00 sharp but neither of us had had much sleep – new boats don’t come with bedding and pillows and rolling clothes up to make a pillow is only slightly successful. It started off fairly flat but as we got a couple of miles off we encountered the standard swell from the SW that plagues Atlantic facing shores and what was left of the previous few days wind blowing at a slight angle across the top of the swell.  This made it slightly lumpy but the semi-displacement keel on the Swift Trawler kept it comfortable.  Our target was Roscoff and if we could keep up a steady 12-15 knots this was going to take us about 12 hours – long day, especially after a night of very little sleep.  As it happened, we had patches of extremely smooth water and made the Raz de Sein just after 13:30.

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Lighthouse & West Cardinal marker at the Raz de Sein

Skimming across the water at 18 knots and over the ground at 15 knots was a little disappointing but we’d had a good run so far and it was inevitable we’d hit some foul tide at some stage. Nevertheless, it wasn’t long before we’d passed in front of Brest and made our way around the westerly tip of Finistère. We were now on the home run into Roscoff.  By the time we got in, the sea was like a mill pond and what wind there had been, had subsided. At this time of year, this really should have been a clue…

A tip for any motor yachts thinking of staying over in Roscoff – the diesel pump will only dispense €300 worth of diesel in one go.  We had to go through the process for refuelling eight times before we had filled the boat up!

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Sat on the fuel berth after our lengthy filling up session

Roscoff seemed to be a sleepy little marina – quite clean and contemporary looking but nobody about.  The restaurant stopped serving early so we had no choice but to stroll into town.  In fairness, it was only the 20 minutes the restaurant owner said it was.

Over the hill and down towards the town centre is a lovely and clearly affluent street of houses, punctuated by something I’ve not seen growing in such neatly aligned rows and in such quantities before – a field of Artichokes!

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Past the artichokes and a little further towards the ‘centre ville’ and the vista opens up to reveal the old port (drying) and the town tucked behind it. Here’s a couple of shots of the entrance to the old port.

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The next day we woke up to pea-soup fog! Advection Fog is common at this time of year. The warm, moist winds coming across the Atlantic are chilled as they encounter the waters around northern France and the UK which are still cold from the winter.  (Water takes a long time to change temperature and is at it’s coldest in the early months of the year, not warming up properly until September, October).

In busy commercial waters I would be very hesitant about setting sail in thick fog but this was a week day now and the only craft we were likely to meet were the local fishermen.  We had radar, AIS and two huge plotters to view it all on – off we jolly well went.  I reckon we were the only boat blowing it’s horn out there but it made us feel righteous. After an hour, we drove out of the fog and left it hanging in the air behind us. We had popped out into a sunny day of cloudless blue skies and flat calm waters; how lovely, Guernsey here we come.

Sadly, Jane couldn’t make it in the end, which was probably just as well as it got really lumpy going around the Les Casquets . The tide would have been against us going through the Alderney Race and with a slight wind over tide effect it would have been pretty rough there too, so we chose the Casquets route but honestly, it was rough enough to slow us down to 7 knots at one point and I seriously wonder if the Race might have been a better option.

Once we’d crossed the shipping lanes and made it to half way across the Channel it smoothed off enough for us to get back up to 18 knots.  From there on in it was pretty uneventful and so, just after 16:30 we arrived in Poole. A successful , speedy, slightly foggy crossing and one very happy owner!

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.

 

Alexio Buchanino’s crazy adventures in Italy!

This is a special post in my Blog to demonstrate how, in the course of my every day job, I am forced to rub shoulders with those elusive people not normally in the public eye.

Here is but one example: the infamous and as yet, still not quite a Double ‘O’ operative but nearly there, secretive agent, looking suave and sophisticated as usual…

In the picture below, in order to maintain his anonymity, he has been cunningly disguised to look like an angelic young lad, who couldn’t melt butter in his mouth, even if he tried…

aka Buchanino, Alexio Buchanino (MI5)
aka Buchanino, Alexio Buchanino (MI5)

Perhaps we should have a look at some his exploits now, starting with, ‘How to drive a RIB in circles’

Then, when you’ve finished going around in circles, you need to learn how to go in a straight line and maybe get some ‘air’ too.

…and now a little practice before the wake-boarding competition, the one that actually never happened as it was top secret and nobody knew about it and those that did had to be shot!

Then some practice eluding the ‘bad guys’; all secret agents need to know how to do this!

and finally, learning how to avoid capture using any available means of transport!

A word to the wise, if you are an aspiring secret agent, you must be able, like Alexio can, to do all of the above, otherwise HM Government is never going to accept you.

Live long and prosper, as someone from Star Trek once said.

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.