The Plotting Sheet

I’d read about Plotting Sheets briefly on the online course and while the three instruction books I had on board each touched on the plotting sheet, there seemed to be some assumed knowledge here that I didn’t have.  The idiot me could not find a basic step by step instruction guide.  The sheets themselves did come with some basic instruction, but it didn’t quite fit with what I was trying to achieve.


It turned out that the huge gaping hole in my knowledge was transferred position lines, yes I must confess I thus far in my maritime career and never used or even thought about transferred position lines.  


I hear the navigators among you despairing, and trust me I was despairing for days, how could something that I felt sure was so simple elude me for so long.  At this point we have been at sea for eight days and I had done nothing but study and keep my watches of course, but even my night watches I spent more time staring at Sky TV than the empty horizon, I was possibly going slightly mad at this point.


Back to that infernal question “where on that line are we?” Finally the answer comes to me in the only really valuable bit of online course printing I’d done.  And there it is in black and white staring at me on the page “We move our estimated position to the closest point of the position line”.  Of course, of course, of course we do, of course it was so simple too.


Now I see, move the morning EP to the morning position line, draw our noon latitude on the plotting sheet, draw our track from the morning EP, move our position line down our track taking distance run from the log…. And there is it… the position line meets the noon latitude line and bingo, we have an actual fix which compares closely to where we are!!


To give real confirmation of this fix I can take an afternoon sun sight, again more maths, graphs, tables and calculations and I get another sensible position line on the plotting sheet.  I then move this back up the course line by the estimated 20 miles travelled and hey presto I now have a cocked hat triangle which puts us within 5 miles of GPS in latitude and longitude at noon.  Admittedly it is now around 1700, but it seems my days of despair and torment are over I finally have cracked this – YES!!!! I have been eight days at sea now, thinking of little else.   And there is it, a curtain has lifted and I see how simple the concept actually is, once you cut through all the jargon and endless books of numbers the process is pretty straightforward and with practice can only get easier.

Sun Run Sun

This was the chapter I didn’t quite get to on the online course, so now I’m counting on having brought the right books, Google or Youtube tutorials are not available out here.  I found it a little frustrating that I’d paid for an online theory course, but hadn’t considered that there was no option to download the course, so, with the exception of a few pages I’d printed, I had no access to any of it whilst at sea, but I guess most people do the theory course first.


And now I’m about to get fully acquainted with new favourite book number two, this book only contains numbers, lots and lots of them.  I like this book, I can see when I have the answer right or wrong even though I can’t always see why at this point, but I can see that the numbers either “fit” or they don’t.  


This book enables us to refine our estimated position using the Sun, Moon and planets at any time of day or night.  Part of my morning routine, as per the instruction books, has been to take a morning sight on the Sun.  I’m at roughly 20 degrees north, it is November and I quickly observe how fast we are spinning as the Sun rises above the horizon at a fair old rate and every observation requires some twiddling of knobs on the sextant to keep the sun on the horizon.  At this time of day we take a series of five sights, record each one to the second and then head for shade.  


I’m also going through the same process with the afternoon to try and use sight reduction to ascertain a position line.  I seem to be able to collect the information I need from the sextant and use the sight reduction tables, but the logic of how the plotting sheets work is elluding me, the more I look, the more lines I draw and rub out and draw again the less it makes sense.  But I’ll keep trying, it will click eventually.  Until that happens the whole thing is driving me a little mad and without Google, Youtube or another human being to explain it to me it could be a very long learning process.


The next step is quite lengthy when you’re as mathematically inept as I am.  We need to work out the average of the five sights, “add them all together and divide by five” I hear you say, neither my brain or my calculator can cope with adding up three columns of degrees, minutes and seconds, all of which are 60s.  I am a metric girl, I was brought up with tens in columns, not sixties.  


So for each morning (and afternoon) Sun sight I draw a graph. As a result I think I am the inventor of “Navigators Graph Paper” where the squares are divided into sixes instead of tens.  We do this to come up with a number and average of our five sights, this is the angle we have measured between our horizon and the Sun, applied some corrections and written down as “Ho”.  This is where the real excitement begins, this is where I find out if I have correctly estimated our longitude, latitude and local hour angle and correctly observed the Sun.  If all of these things are correct the number I have (Ho) should be very close to the number I will obtain from Favourite Book number 2.  “Ho Mo To” has been the mantra my shipmate has been whispering for the last few days.  It turns out that once upon a time he had taken celestial navigation classes and this phrase was drilled into them.  “Ho Mo To” will mean nothing to you, but it meant the world to me once the penny dropped.  Seeing the numbers align themselves on the page is an immensely satisfying process, especially for the mathematically challenged, and a welcome confirmation that all of the above are good.


Rather disappointingly after all this the best we get is a line on a chart, all we know is that at the time the sight was taken we are somewhere on this line.  “But where?” That infernal question again… “somewhere on that line” is very vague, especially when the line is very very long.  I still feel rather lost in all of this!


I know the next thing I must do is work out what time I think noon will be, take our noon sight and with any luck, finally get my head round the mystery of the Plotting Sheet…

Day 7. “The Bomb Squad”

Another blue sunny day in the tropics.  The waves are bigger now, but this cruise ship is hardly feeling the roll of the ocean.  Had we been in a monohull this crossing would have been an altogether different and more difficult state of affairs.  Our progress has slowed considerably, the wind has dropped and our wind angle is way aft, we are now averaging a very painful 4 to 5 knots over the ground.

On the astro nav front I am starting to despair over Sun-Run-Sun and how to use the plotting sheet, I am now beyond the point I got to in the Yachtmaster Ocean online theory course.  I could be lost at sea for a long time yet!


Our Iridium Go system of wonder, is providing little wonder and much frustration.  We can text out, but for some unknown reason we are not receiving messages back, which is rather disappointing and the Iridium Go Help page is not helpful.  It does give us access to weather files each day, so I shouldn’t grumble.


It turns out that it is our skipper’s birthday today and at dinner time our American crewman sings us a Sea Shanty that he has written about the trip so far, it is very entertaining.   Since are now having a party by providing our own entertainment it seemed like a good day to get the whistle out and play a few tunes.  To celebrate the birthday and because we are “yachting” and there is fruit to use up, it seemed rude not to mark the day with a glass on Pimms.


It is Monday, so the watch system rotates, which means tonight I am on 2200 – 0200, man that watch seems to go on forever.  It was a pretty grim watch, with shifty light flukey frustrating winds, loads of ominous clouds and heavy rainfall, all the signs of potential squalls, but the breeze doesn’t seem to materialise.  For a very brief spell of maybe 20 minutes under one cloud we caught a bit of a draught, only about 16 knots true, but it felt like a gale compared to what wind we’ve had so far.  It was colder air tumbling down from aloft and for a fleeting moment I had 9.3 knots out of her, I averaged closer to 8 knots for the 20 minutes then we were back down to 3 knots and flog, flog, flog.


Once again I have to wake “sleeping beauty”, to encourage him to arrive on deck on time.  My patience is wearing thin after a week of this and the wake up “calls” contain a lot of shouting and swearing in proper Manx fisherman style.  At 0150 my shipmate looks at the clock and says “Time to send the bomb squad in”.  

Day 6. The Ocean springs to life

I’d not long been in bed after coming off watch at 0600 when I heard a shout of “Whale!!” By the time I’d dashed up on deck I had of course missed it, but I was treated to my first flying fish of the trip, so I wasn’t disappointed.


Back to my “bunk” and I’ve adopted the starfish sleeping position (it would be rude to waste all that space!) so the first indication I had of us gybing was a bit of kerfuffle on the deck followed by the Atlantic coming in my window as my cabin become the windward side – splosh!  


So here we are at 20 degrees 50’N sailing west with beautiful rolling waves, a fair wind and a following sea making on average 7 knots over the ground.  It is Sunday, so I cook bacon and eggs for lunch.  Today I get my noon latitude to within one mile of our actual position today – yippee!!!  


We’ve only just entered the land of the flying fish and already the “bad boy” lures are proving perhaps a little too successful.  A big fish has taken my lure and all my line while no-one was watching damn it, I was asleep!  There is more line on board so I’ll rig another one tomorrow.   Although, I think I might be only person on board with an idea about fishing (and my knowledge is pretty limited, unless there are some dredges).   Over dinner the landlubbers were exposed as they started asking about how to gut a fish.  I gave them my finest Manx description “take  sharp knife, stick it in its asshole, slice its belly open… stick yer hand in…”.  Judging by their reaction this will be my job when we do catch a fish.

There were a pair of what looked like Manx Shearwaters flying around at sunset, they look so familiar, but I’m not sure if we find them at this latitude.  I must remember to check when google is back on.



Day 5. Into the Tropics

We entered the tropics today pretty much at dead on noon and here are the trade winds, we are now shifting at 7 knots in nice rolling waves, but still no flying fish.  It looks like we’ll be making the big turn right tomorrow, in about 100 miles.  


Today I have a huge revelation in sextant operation… index error (actually operator error), but with this eureka moment and a few minutes of maths I have our latitude at 23°01’.5N, I am 1.5 miles out!!! Allelujah!  Another small step in the right direction.  Next up Sun-Run-Sun and the quest for longitude is occupying my mind.  I wish I had learned about running fixes and transferred position lines before now.  There is no human or Google available out here to ask.


Our American crewman has decided that this catamaran sailing is not really sailing “more like yaaughting” attempting his best at a posh English accent.  I am inclined to agree, this is certainly not sailing, we are far too comfortable, so “yachting” is a fitting description.


It is another beautiful night on the ocean under the brightest and lightest full moon I have ever seen.  I realise trying to explain VMG to my shipmate is nigh on impossible, so I give up and enjoy the peace on deck “moonbathing”. Plotting star sights is also proving nigh on impossible at the moment.

“The full moon shines upon the sea like spilled milk”

With the quest for noon latitude only allowing for one attempt per day I had been filling the hours taking morning and afternoon sun sights and observations on other celestial bodies, the Moon, Venus, Polaris and a whole host of stars, but I had very little idea what I was to do with all this data.  


It is our third night at sea and I have the 0000 to 0400 watch.  I go out on deck to a brilliant 99% full Moon.  It is so light out here it could be noon on a mid winter day at home, you could almost read a book out here.  The moonlight makes the horizon is clearly visible, so, (unusually I will soon learn)  in the middle of the night I have a go at trying to get some star sights with the sextant.  


I’m using a plastic cheapy sextant which is ok, but the telescope is not good enough to pick out the stars.  However, since I can see them with the naked eye I try taking the telescope off the sextant and just looking through the space left by the telescope.  To make this work I have to set the sextant to 0 and point the whole thing at the star until I have the star in the mirror, then I slowly work everything down to the horizon keeping the star in the mirror all the time.  It is tricky and my approach is the reverse of the recommended method described in the books, but it is the best I can do and it is working.  I have also been fortunate to grow up on an Island with “Dark Skies” status so I have already spent years learning my way round the constellations and stars, this is also helpful now I have resorted to this backwards approach.


“Star men do it with their eyes open” the book says and sure enough, no telescope, plenty of moonlight, a clear horizon and I am bring stars down to the horizon and getting readings!  Now I have so much information I’m struggling to sit down and face making sense of it all.  In the end I call this a sextant learning exercise and leave the maths for later.  The Sun is occupying all of my mental processing ability, there isn’t room for any more numbers right now.


The sextant and the celestial bodies are fast becoming an obsession and for days I took sights on everything and anything that I recognised.   Writing down endless numbers I pondered in awe about it all, a slow moving pattern is emerging.  

Day 4 “Can this day get any better”

It started with a massive sleep, almost a whole five hours, which was much needed after yesterday’s adventures.  I got up shortly before noon, armed with sextant, watch notebook and pencil and I’m off out on the deck on my quest to establish our noon latitude.  I’m getting closer, within 18 miles of GPS today, but still not good enough, we’ll try again tomorrow. 

The ocean is big and blue and beautiful, the sun is shining and we are headed toward the tropics.

Our battery situation is still troubling me, perhaps we’re not charging often enough, perhaps there is something running and draining the power that we’ve overlooked.  I go through a charter company boat brief almost verbatim,  how often to charge batteries, what volts we should be seeing etc etc.    I learn that the boat had motor sailed from La Rochelle to Fuertaventura, so now we are sailing the power is dropping more quickly.   At this point I suspect the inverter has been on all the time, which is likely to be the cause of the drain.  We’ll keep monitoring it.

Meanwhile in the ship stores, the bananas are ripening up nicely and need using.  I have brought all we need to make banana bread, so this afternoon I do a spot of baking and the crew all wake to the lovely smell of cakey goodness.  Hey presto, I’m the most popular person on the boat.  Keeping the vultures off the stuff while it was cooling proved tricky!  

I’m also now taking sun sights in the afternoon to try and use sight reduction to ascertain a position line.  I seem to be able to collect the information I need from the sextant and use the sight reduction tables, but the logic of how the plotting sheets work is illuding me, the more I look, the more lines I draw and rub out and draw again the less it makes sense.  But I’ll keep trying, it will click eventually.  Until that happens the whole thing is driving me a little mad and without Google, Youtube or another human being to explain it to me it could be a very long learning process.

The day ends with dolphins at sunset and shepherds pie for tea! Things don’t get much better than this and there is still the midnight watch to look forward to.





Day 3, Batteries, spreaders, dolphins

It is 0000 on 2 November, I have the 0000 to 0400 watch.  It was quite a chilly night, at least chilly enough for a jumper and a duvet while I lay in the comfort of the cushions on the top deck, staring at the moon and the stars, I’m in heaven.

 And to top things off I treat my fellow crewman to jam on toast, Juan’s home made Manx blackberry jam.  My American crewman was delighted (apparently blackberries were expensive in the US when he was a boy), “but the grow everywhere for free” I exclaimed, explaining that these weren’t shop bought, but hand picked.  Apparently the jam is so good that I’m worth throwing overboard for, I’d best watch out!


It was shortly after the jam treat that the autopilot started complaining about low ship battery, to be honest i was surprised it had taken this long to register.  Sure enough we’re down to 11.4V on main battery bank, we fire the generator up, the alarms stop.  Our skipper wakes up after a while of the genny running, wondering why we have it on and how could it be we are using so much power?


I’m off watch at 0400, but I’m still awake and alert and thinking about our power situation.  We are running a lot of domestic systems, plus autopilot, radar, chartplotter, but we have a huge battery bank, so something seems amiss.  The worry is that everything on this boat needs power, you can’t even pump the heads out manually, the worst case scenario is not a pleasant one, but I guess it is more like the kind of sailing I am used to!  It is a worry for the daylight tomorrow.


The next thing on my utterly sleepless mind, is the noon sight I took today.  I was 2 degrees out (doesn’t sound like a lot but it equates to 120 miles in real terms).  I rework the sums again, then I rework it with different numbers to see if I can get us closer to our actual position.  In the end I do the whole thing backwards from my known lat off the GPS to work out what I should have had as the sextant reading.  The problem all along had been the accuracy of my sight in the first place, but this is a big learning curve and we can only aim to improve.

I doze restlessly until I’m back on watch at 0900 for three pleasant uneventful hours, we’re plodding along averaging 5 knots, it isn’t very windy and is dropping, the sea is calm in relative terms.  

This morning watch also saw the start of the fishing competition.  Who is going to catch that illusive tuna?  Our skipper has got an actual rod mounted on the starboard side down aft and is using some kind of squid lure, I’m on a hand line which is lashed on to the port side, I’m using the bad boy big silver lures that Juan sent me off with, I reckon my chances are better, but it is going to be a long game this one 🙂


The next part of my daily ritual is to work out the time of the sun’s meridian passage for our longitude. I estimate today it will be around 1158 (ship time).  So, I finish my watch poised on the foredeck, sextant in hand to try again for a noon sight.  I think this time my sextant altitude is closer than yesterday’s efforts, but we’ll have to wait until later to do the sums, something more pressing has come up.


One of our crew points to a very definite hole in the mainsail where it has been sitting on the lower spreaders.  This boat is advertised as being an ocean cruiser, surely on an ocean cruiser you would at least reinforce the sail with spreader patches? Apparently not.  So, I am not getting off watch to catch up on sleep.

 Nope, I’m climbing into bosun’s chair on, armed with knife, gaffer tape, rope and a couple of towels to put some chafe preventers on the shrouds.  Luckily it is about as calm as the Atlantic gets, but unlike a monohull there is no constant heel angle.  I climb up the shroud (easier to grip and climb that than the big fat mast), the spreaders are too long for me to be able to wedge myself in between the mast and the shroud, so I’m trying to stop myself swinging in circles around the rigging which is tricky.  

The main halyard has a double purchase system, so there is a turning block shackled to the harness which is a massive pain in ass (or arms) as it kept pinching my skin between the block and spreader or rigging as I’m trying to hang on and keep steady with my feet and legs on the shroud and an arm over the spreader so I can work.  After an hour both spreader ends are well and truly padded out with towels and a shit load of gaffer tape.  All of this is the heat of the midday sun, at least it was calm.  Mainsail is back up and we are away again.


I’d worked up an appetite after all that hanging around so I served up lunch, the usual cheese, cold meats, tuna mayo, tomatoes and bread etc.  Man I was hungry, two sandwiches, left-over pasta salad, cheese and apple!  


After all that exercise and food I am too alert to sleep for the afternoon, so I set about looking at today’s noon sight.  This time I am within 20 miles of our GPS position, which on the large scale charts looks like almost no difference.  YES! I am happier with this one, although I am still a long way off, but hopefully, with more practice my accuracy should improve.

Then I hear shouting from on deck, I thought someone had caught a fish, but no, we have dolphins!!!! Loads of them all stopping to play in our bow waves for a good five minutes.  It was incredible, lying on the bow of the catamaran watching the dolphins around the bow and under the trampoline, the water is so blue and so clear, just beautiful.  I am so lucky to see this, I am watching Blue Planet for real 🙂


Yet more novelty for the afternoon as we put the washing machine into use at sea for the first time, by sunset I have clean and dry laundry!!


So the day was just too busy to catch up on any sleep.  As I write this I’m on the 2000 – 0000 watch, I’m sat on deck under a nearly full really bright moon, you could almost read a book out here it is so light, too light for the stars to be out and there is a full moon bow glowing around the moon above the masthead.  I’ve just finished watching the final episode of Game of Thrones whilst sat on deck under the moonlight (yet more novelty).  

It is 2340, I’d best go a wake our German crewman up now if I want to get off watch on time, he doesn’t seem to have grasped the concept of setting an alarm and being on deck early, I won’t be putting the kettle on for him.  Then I’m off to bed until 0400, so I will see the sunrise in the morning, and maybe have another go at getting some star sights with the sextant (really really really tricky with the plastic sextant I have, but I’ll persevere) provided the clouds allow me to opportunity to do so.


As I write up the 0000 log entry I realised we are yet another whole degree further south… getting warmer!  24N now, another 4 degrees before the final turn to the west, maybe another gybe south tomorrow could be in order?  At the moment we are cutting the Cape Verde corner, not much wind about anywhere it would seem, we’ll decide based on tomorrow’s weather download.

Noon is not at noon

It turns out that during the day a sailor has only one real chance at confirming the ship’s latitude, this happens at noon each day.  When the Sun is at her highest point in the sky we can take our sextant, measure the angle between the Sun and the horizon and after applying some maths we can calculate our latitude.  


It also turns out that noon is not at noon, so already the whole affair becomes a little more complicated. This is where my new favourite book to be, The Admiralty Almanac, shows me exactly why it carries the hefty price tag, all the answers are in this book, I’ve just got to decode it.  Mr Rodgers and Mr Cunliffe provide sufficient guidance and I’m away.  Even standing still the time of noon varies by up to 16 minutes away from clock noon over the course of a year, because of something called the Equation of Time.  


The beauty of the navigation side to this is that you don’t need to know why this is, one simply needs to know where to look in the new Favourite Book.  Today noon is actually at 1144 if you’re standing on the Greenwich Meridian, which of course we are not. .  So… I know the Sun will pass over Greenwich in London at 1144, from my dead reckoning position I have an idea of how far west we are, so the Sun will pass over my head some time after 1144.  I can now refer to the favourite book and estimate what time the Sun should reach her highest as she passes over my head (or my meridian on the globe if you prefer).  


Then it is off out on deck in the heat of the midday sun, armed with sextant, watch, notebook and pencil.  First thing, check and write down that sextant error bit, once that is done it is time to start watching the world spin round using a small telescope and a couple of mirrors.  I am on deck 20 minutes before I expect my local noon to happen (since mine is only approximate based on my estimated position), and so I measure and watch as the sun stops rising in the sky, now she seems to steady on the horizon for a few minutes before she begins her slow descent toward the western horizon.  And that is it, it is all over, we have our time and measurement taken with the sextant written down and it is time to get back into the shade.


Now I am getting more acquainted with my new Favourite Book, it will help me do a handful of calculations to (hopefully) ascertain our latitude at noon.  Two important things happen here.  First off the world tilts on its north south axis, hence we get longer days and the sun higher in the sky during the summer and now, in the winter our days are short and the sun is low in the sky.  In the celestial navigation world this is called declination. And that, is more than we need to know about it, we’ve just got to ask the Favourite Book for the answer.  We do however have to ask it the right questions, mostly “what time is it at Greenwich” and “what time is it with me here and now”, the book reveals differences between the two that we must take into account to find our precise declination.  Then a very quick sum and we have our latitude.


At this point I don’t think it is cheating to now check our noon position according to the GPS to see if I am close or not.   In a beginners kind of way I probably am close, on the scale of the ocean chart it looks close, but for the first three days my noon sights were not accurate enough.  


I continued this process like a devoted student, on day three I realise the error I have is a consistent one, so this time I take the noon latitude from the GPS and do the maths backwards to work out my errors.  Operator error and operator understanding are definitely the cause, looking at the sextant instructions on or before day one would have been an idea too.  So with errors found and corrected and corrections applied to the previous sights too, my latitudes are now acceptably close to our GPS track and I am starting feel that the task I have set myself might still be achievable..  

Day 2. Wind, waves, spin, sway

It is midday on 1st Nov, our second day on the ocean and I have just had another attempt at a noon sight.  We have been averaging 6 – 8 knots so far, although our heading is closer to south than south west, since with our swept back rig and total absence of any kind of useful downwind sail, sailing any lower is painfully slow.

However, in many respects, catamaran sailing really is living! We have more luxuries than I have at home including hot running water on demand, shower, gas oven, hob, freezer, big fridge and another drinks fridge on the aft deck, (well, I call it “deck” but conservatory might be more a fitting description) and of course we have the washing machine.

The motion on the cat is considerably more comfortable than a monohull. Where, by now a monohull would be rolling side to side, the catamaran seems to work across the diagonal axis of the two hulls, when one bow is down the other is up and vice versa at the stern. The marvellous outcomes being that I can stand up in the shower without bracing myself against anything, I can use the heads without fear of incident, I can lie in bed without rolling out – no lee-cloths required and best of all, I can put my mug down on the table without any concern for it falling off or even spilling much of a drop. Oh yes, this is living it up on the ocean for me.

The highlight of our second day on the ocean came shortly after midday, when, having had enough of seeing Africa getting closer to us, we elected to gybe and take a stab west. The result was a more acceptable heading for the Caribbean, but the loss of a knot of boat speed which was the difference between sailing west and northwest! There is valid concern at a distinct lack of wind forecast for the next few days too, it looks like 5 knots might become the norm.  Living maybe, but sailing, I’m not so sure.


We are all quietly settling into our new ship life as the daily routine starts to rotate around the ship’s watch pattern.  At the same time I am finding a second pattern which is dictated by the Sun, Moon,twilight, dawn and dusk as the Earth carries on spinning her way through time and space.  I sit here watching her constant rotation, watching her slow wobble through the seasons. 

Once again my mind explodes at the vastness of it all…. And who figured all this out…. and how did they do it…How?  The enormity and complexity of it all brings as many questions as it does answers.  I find a certain peace and sense of purpose in my routine and studies, it fascinates me on so many levels and to think that this view is just the same view as all the great navigators gone before, it hasn’t changed.  I think an old sailor spirit lives in me somewhere.