On our most recent yacht charter tot he Bay of Islands New Zealand we encounted one day with reasonably high swell and only about 10 knots of wind. Being on a broad reach was not the ideal heading for this but alas this is the direction we wanted to go – from the Bay of Islands up to the Cavalli Islands.
During the sail one of our precious crew became a little seasick. The proven cure I’ve always found to work is to have that person steer the boat. It takes about 5 minutes and viola – they’ve been so hard concentrating on helming that the seasickness has gone.
Later on in the week another became sick on a long sail. This time I administered a nice hot cup of freshly made ginger tea. We ground up the fresh ginger root and poured boiling water over it then strained off the root after a minute and served the tea. Besides being quite tasty and refreshing the tea did it’s job of fixing the seasickness with in 10 minutes. Having ginger on board is is paramount to enjoying a good feed of sashimi after your catch. So ginger up when doing your provisioning.
Ginger fixes seasickness
There is another good preventative measure that one should take before pulling anchor. And that is to have a good pooh. Yup that’s right strange as it seems it helps. Of course having one underway is always proven to work as well because the moment you go below to indulge in this behavior you will instantly puke – which is actually a good way to fix seasickness anyway. I.E. don’t go below unless you instantly want to puke. Now having a good puke does work but the instant this happens you’ve got to eat more food to help settle the stomach no matter how bad you feel after a puke – eat! It works!
Other methods I’ve seen work is the electronic shocker watch. It’s a strap you wear around your wrist that administers a small electric shock on intervals.
If your a druggy there are non natural methods that can also work like patches and ingested drugs. Unfortunately our western culture tends to believe a drug method first rather than the natural ones. Me, I’d rather not put too many chemicals into my body and try the natural proven ones first.
Int eh bareboat charter course we go through just about everything you’re going to encounter on a bareboat yacht charter sailing vacation. Knowing this kind of information can make you a hero and an admired leader.
Take the Bareboat Charter course now
On the way back
Christian and Lucy at Performance Yacht Charter are a pretty impressive (and really nice) couple. They sail the world with their two charter yachts, Northern Child, a swan 51, and Smile and Wave, a Beneteau First 40, entering into world renown Yacht Regattas. They’re good friends of us at NauticEd. We first met them in St. Thomas in the USVI in 2011 at the International Rolex Regatta where they raced their sailboat, Northern Child with a combined group of NauticEd students and Safe Passage Sailing Clients.
Provided you’re got a little bit of sailing experience you can VERY affordably join Christian and Lucy on one of their Regatta Charters. And at NauticEd we TOTALLY endorse this idea. You see at some point, as much as you enjoy our sailing courses you’ve got to get off the computer and get the wind in your face. Being in a charter race regatta is going to be an such an exhilaration that you’ll never forget it plus you’ll get a huge step jump in sailing knowledge from the emersion situation. CAUTION HOOKING UP WITH THESE GUYS WILL BE A LIFE CHANGER.
Christian and Lucy’s talents are proven by the many 1st line honors they taken at various regattas, so when you join them, you’re learning from some of the best.
Go visit Performance Yacht Charter now and check out their next race series.
Being the beginning of March 2013 right now – here’s the next opportunity to join and learn from this awesome couple/team:
40th International Rolex Regatta in St. Thomas 22nd -24th March
BVI Spring Regatta in the BVI 29th – 31st March
To make a reservation now call Christian or Lucy on their UK phone number at country code 44 number 7795 955702 or send an email to email@example.com
But don’t let these dates stop you if your too busy to engage with life at this level. Visit Performance Yacht Charters website to learn more about opportunities.
COME ON – challenge yourself – send this blog to a friend or life partner right now and say – “Hey come on lets do this”.
Tides and tidal currents came to mind today as I strolled along the harbor’s edge watching the behaviour of some sailboats racing. Remembering a recent race regatta series I participated in in the Auckland New Zealand harbor last winter also brought up this topic of tides and tidal current. In one race in the series, we were racing back up the harbor while the tide was ebbing (going out). Consequently, the current was racing in the other direction. Our tactic was to stick to the sides of the harbor as close as possible where the current is the least. Unfortunately all the other boats knew to do this as well and this created a pretty big mess of all the fleet tacking on top of each other. “Starboard” was the call of the day as each boat established their stand-on position over the other. Every now and then one boat would break out and try to brave the current instead of the tacking mess only then to rejoin the fleet as they were dragged backwards. It was pretty exciting actually, although our skipper was stressing a little.
There was pretty much nothing we could do except tack tack tack and keep a very diligent watch for traffic ducking and tacking to give way when required. The skippers were trading expletives with each other across the water more in this race than I’d seen in any other. LOL
How Tidal Flow Works in a Harbor
In a channel, current will run strongest in the deepest parts typically towards the center, unless there is a bend in the channel then the current will run strongest on the outsides. Just think about the last time you watch water flowing in a river to visualize. So your best bet when trying the go against the tidal current is to hug close to the sides and on the inside turn if possible. At an extreme case I had a friend in Sydney harbor who won a race by waiting out the worst part of the tidal current by throwing down the anchor. Not sure if that’s against any official race rules but it’s pretty funny.
Also take note that current flows “relative” to the tide period but slack water does not necessarily match high and low tide times especially in harbors. Tidal current is determined by the local effects of the upstream harbour shape and weather, not just the sinusoidal tidal period. That comes as a big revelation to some. In fact, I physically had to show my skipper prior to the start of a race one day last winter.
Real Example of Tides in a Harbor
Observe the following which is Auckland New Zealand harbour, one of the more heavily raced harbors in the world.
Chart of in Auckland Harbour
Now look at today’s tidal period;
Sinusoidal Tide in Auckland Harbour
- High tide: 3:52 am
- ½ tide at 6:55 am ebbing (going out)
- Low tide: 9:57 am
- ½ tide 1:07pm flooding (coming in)
- High tide: 4:16 pm
- ½ tide: 7:22 pm ebbing (going out)
You might assume that minimum current occurs at high and low tides ie 3:52 am and 9:57 am and 4:16 pm while the max current occurs at ½ tides at 6:55 am and 1.07 pm
But now look at today’s current predictions:
Tidal Current in Auckland Harbour
- Min current flow was at 3:15am (45 minutes before high tide)
- Max current flow ebbing was at 5:16 am (1 hour 39 minutes before ½ tide ebbing)
- Min current flow was at 8:15 am (1 hour 45 minutes before low tide)
- Max current flow flooding at 10:54 am (2 hours 13 minutes before 1/2 tide flooding)
- Min Current flow at 3:51 pm (25 minutes before high tide)
- Max current flow ebbing at 5:57 pm (1 hour 25 minutes before ½ tide ebbing)
A quick analysis of this shows that the current matches in time the flooding tide more than the ebbing tide. This empirically supportis the statement above about how the upstream shape determines the current flow out.
As a specific example, lets say it is 8:30am on the day shown. From a tidal analysis you would think that the tide is ebbing and so an early morning race out of the harbour you’d probably stick to the centre of the channel. However the prudent sailor doing a current flow analysis would see that the current has already turned to flood and would stick to the sides of the channel. All things else being equal, prudence would win.
- Don’t assume that the current is slack at high and low tides
- Stick to the edges of the harbor when going against the flow
Navionics Electronic Chart
In this article I used the Navionics iPhone app. I pressed and held my finger over the diamond shaped T to get the tidal info and the diamond shaped C to get the current info. When you have such an electronic chart, look for these diamond T’s and C’s scattered through out. On iPhone and iPad simultaneously push the home button and the power button to get a screen shot.
Tide and Current icons on an electronic navigation chart
Rule of Twelve
While we’re on the tidal topic I might as well discuss the rule of twelve regarding a sinusoid. It’s a good general piece of knowledge to know since tidal heights generally follow a sinusoid shape (except in weird tidal places in the world like the Solent in England where two high tides occur about 1 hour apart).
In the first 1/6th of the time between high and low tides, the height changes by only 1/12th of the full amount
In the next 1/6th the height changes by an additional 2/12 (=1/6)
In the 3rd 1/6th ie half tide the height changes by an additional 3/12 (1/4)
Adding 1/12 + 2/12 +3/12 = 1/2. So at half tide, the height has changed to ½. That makes sense but looking back and assuming a diurnal tide (6 hours between high and low), in the first hour the height has only changed by 1/12th. That’s insignificant. At the end of the 2nd hour the height has changed by a total of 3/12ths = ¼. That’s still pretty insignificant.
What this means is that if you’re relying upon the tide to increase the depth in a shallow area, then even with a 10 ft (3m) tide, 2 hours after low tide, it has only come up 2.5 ft (0.75m). Best you wait until half tide at least when the ½ of the height change has occurred (5 ft (1.5m) in this example).
NauticEd Coastal Navigation Sailing Course
For a full discussion on tides, tide table, how tides work and why there are two tides in one day when the earth and moon only rotate relatively about each other once per day, take the NauticEd coastal navigation sailing course. You’ll also be able to brush up on your navigational skills which isn’t at all a bad thing.
Coastal Navigation Sailing Course
This article was written by Grant Headifen, Educational Director for NauticEd Online Sailing School
NauticEd’s sailing courses cover a wide range of sailing education. They cover from beginner information designed to help a new sailor become familiar with the goings on on a sailboat all the way to extremely advanced information like what to do if your mast breaks 1000 nautical miles off shore.
Saling courses availability
All the courses are online and available worldwide. The information has been internationalized meaning that as you travel around the world you’ll be able to adhere to the various standards. For example, the lighting and buoyage system covers both IALA-A and IALA-B information. In addition to that NauticEd is engaged in a project to make all the sailing courses available in multiple languages.
At first thoughts, some sailing instructors have been against the idea of using the Internet, citing such comments as “you can’t learn to sail online”. However once they start to interact with students who have done their theory work using NauticEd’s multimedia approach to learning, they have started to turn around.
Virtual sailing instructor
As a practical sailing instructor for many years, in many instances I would battle with trying to have students really understand and “get” how the sails should be set for each wind direction. For that reason we invented NED. NED is a virtual sailing instructor that students can interact with to learn the set of the sail. They can see the boat speed up and slow down depending on the set of the sails and the different wind angles.
In other circumstances, we have created interactive educational animations that show how wind creates lift and how turbulence is created. When showing a student on an actual boat in real practice, the student can’t actually see the turbulence if the sail is over trimmed. These kind of things are best left to diagrams and even better than a diagram is an actual interactive animation where by the student can move the sails themselves and see wind spawning off into eddies.
In addition to the sailing courses that NauticEd offers, we also worked with the world’s yacht charter companies to create a sailing certification that would be acceptable and desirable by them. What we overwhelmingly found during our interviews is that the bareboat yacht charter companies wanted to see lots of practical sailing experience in addition to theory knowledge. For this reason we created a free online sailors logbook allowing students to enter their past experience in a manner with which the charter companies were familiar and in a similar manner that the United States Coast Guard require when applying for a captain’s license. Then combining the theory courses that were completed with the practical experience we were able to electronically create and display a very useful sailing resume and thus sailing certification.
Thus the NauticEd sailing certification inherently contains more information about the student’s real knowledge than any other sailing certification because in order to get the certification, a student must fill out their practical experience logbook. With other certifications, if you do a weekend class you can get a certificate and the charter companies said to us that that was not enough to allow a client to take out a boat. The NauticEd certification covers everything a yacht charter company needs to know.
So in summary, and perhaps tooting our own horn a little, NauticEd has the best sailing courses available and the most useful sailing certification when it comes to chartering a bareboat yacht.
Learn more about NauticEd’s sailing courses.
This is the 2012 New Years Resolution Sailing Tip
This issue’s sailing tip is a pretty simple one. It will lead to you having more valuable practical sailing experience than you’d ever imagine. And it fits nicely in with any new years resolutions you might be considering.
When I lived in Austin Texas, I raced a lot with the local sailing club there on Lake Travis, an inland small lake. And I have to admit that much of my finer technical sailing knowledge came from those many regatta races.
When a sailboat racing next to you is inching ahead moment by moment you learn quickly the importance of accurate sail trim. And talk about drilling the rules of the nautical road – wow when you’re on collision course with dozens of yachts you’ve got to know the rules.
Here’s the tip: Join a local yacht club this year.
At NauticEd we REALLY believe that practical sailing experience is one of the keys to becoming an excellent sailor (of course we’re making a big assumption that you don’t have a goal to be a crappy sailor).
A bit of History: When we designed the NauticEd sailing certifications, we consulted with dozens of sailing instructors and many of the world’s largest charter companies. With out any hesitation, they all rated practical sailing experience as a must have to becoming a competent sailor (durh). When we looked at every other global sailing certification, none required practical sailing experience as a prerequisite to gaining the certification. That’s a bit strange we thought because in this digital age, it’s easy to write an algorithm that can combine theory knowledge and practical experience (well not that easy but you get the point).
Then we looked at the scuba diving industry and the scuba certifications. We found that the theory education was excellent but practically – if you can barely swim, you’ll still end up with a certification. Still strange! The scuba magazine editorials are full of complaints about new divers banging into the protected reefs because they can’t do the most basic buoyancy control.
When it comes down to it I guess, most certifying companies are more interested in the $ than the true competency of the student. Thus we decided to set the competency bar high so that the charter companies could truly trust a experience and theory based certification.
So here’s the big “but” that people ask us all the time then.
“But … how do I get sailing experience when I don’t own a boat”.
Well… in virtually every city with a sailing waterway there is a yacht club.
- Joining a yacht club is pretty simple and relatively inexpensive for the return you’ll get. Costs range from $40 to $80 per month. And if you own a boat, many times the marina fees are less expensive than a regular marina.
- Some clubs are very racing focused some are not. I’ll maintain however that even if you’re not a racing type person, racing experience will improve your cruising sailing skills vastly. Racing is like learning a language by immersion.
- Yacht clubs are highly social and so you’re going to meet a lot of very cool and interesting people who will become your friends. Throw away the preconceived notions of the stereotype snooty stuffy yacht club and just join one and find out for yourself.
- Yacht clubs many times have a nice pool for the kids to hang out in and they will get to hang out with other yachting type kids. A vast improvement from learning life skills at the mall.
- Yacht clubs organize weekend sailing trips away. These are usually very fun flotilla events. Here you can learn a lot of overnighting and anchoring skills.
- Occasionally yacht clubs will also organize a bareboat charter sailing holiday to places like the Caribbean, Mediterranean or the pacific islands. This is a great opportunity to join in on the safety of a flotilla.
Some people think that if you don’t own a boat, then what’s the point of joining a yacht club. However, if you don’t own a boat, then you should definitely join a yacht club. Here’s a big fact. Virtually all boat owners are desperate for crew for either racing or cruising events. This is proven by the dozens of post-its on the yacht club notice board from skippers looking for crew.
Typical Yacht Club Notice Board
So – this year, join your local yacht club. Put your name up on the notice board that you’re willing to crew. Commit to some regatta race series. Do some boat jumping to find the boat/crew/skipper that you like. Make some friends. Get lots of sailing experience and most importantly, fill out your free NauticEd electronic sailing logbook. As with above, your logbook is the single most important thing that the charter companies look at when you are trying to charter a boat.
And one more comment – years ago when I ran a large yachting membership program, the biggest reason that people dropped out was that they did not have friends to go sailing with them. A mistake that I made was that we should have promoted our boat owning members to also join a yacht club. There, they would have found plenty of new friends to go sailing with, from the exact same notice board mentioned above. If you own a boat – join your local yacht club this year.
Happy Sailing Experience!
While all sailboat designs are different and will sail optimally at different heel angles and reef points, there are a few generalities that we’ll cover in this sailing blog.
General reefing point number 1 through infinity: Don’t scare the beegeebees out of those on board by heeling the boat over too much. While you may be singing and enjoying yourself, others may be frozen solid.
One time sailing off Corsica (lovely sailing destination btw) we encountered a 40 knot Mistral breeze. We were sailing a Beneteau 50 and what a delight it was. The waves were about 8 feet and consistently washing over the deck. It was a beautiful day and we all had a blast – EXCEPT one person on board who had not been sailing much before. When we reached the marina in Bonifacio he jumped off the sailboat and lay flat on the dock kissing the dock boards. I learned that he had been so terrified that he could not speak and was looking between each wave where to jump clear of the boat it in case we went over. Lesson learned for me! That’s not a good thing to do to your guests and not a good way to keep the sport of sailing growing.
Funny as it is (sort of), now I make sure that everyone new on the boat knows to look first into my face when they start to get scared. I tell them that if I’m smiling then it’s all ok and that they are only allowed to get scarred if they see worry and fear on my face. Now the thing to do is to not show fear through facial expressions or through my voice. This keeps the crew thinking straight and following instructions instead of worrying about jumping clear of the boat.
Ok back on topic to heel angle and reefing. We’ll cover non-spinnaker/genaker operations here because broaching (getting knocked down) with those sails is a different topic.
Certainly in light winds, some heel angle will ensure your sails have some airfoil shape to them so position your crew to leeward to create at least about 5 degrees of heel angle. As the winds pick up you can begin to move your self moving ballast (crew) to the windward side to balance the wind force aloft in the sails.
In general, for most cruising sailboats, once you reach about 25 degrees or so the sailboat hull design and sail rig design will begin to reduce the ability of the boat to increase in speed in an efficient manner. OK wow that’s a very general statement but it’s a statement that will allow you to watch, learn and experiment with your own particular boat.
A weighed keelboat typically is not in danger of capsizing for three main reasons:
- As the boat heels over the distance aloft to the center of pressure of the wind is lowered and thus the heeling moment is reduced. As an example, lets say the boat leaned all the way over. This heeling moment then is reduced to zero. So theoretically the wind can’t heel you all the way over anyway.
- As the boat heels over the vertical area of the sails presented to the wind is reduced which reduces the actual heeling force.
- As the boat heels over the weighted keel is lifted to windward thus creating a righting moment. The more the keel is lifted to windward the more the righting moment.
Heeling Moment vs Righting Moment
From above then, the more the boat heels over, the less the “heeling” moment from the sails and the more the “righting” moment from the keel. Or again in very not tech speak: in a full laydown situation there is no more tipping over force left and only straightening up force remaining. It might not feel like that when your hanging onto the rails for dear life but it’s pretty much the reality of the nature of forces and moments.
What is “moment”? Moment is the ability to use a screw driver to open a paint can. Imagine a very stubborn paint can and a very short screw driver. Now use a longer screw driver you can imagine the force needed becomes much less. That’s moment. It’s not the force that opens the can but the moment. Moment is mathematically force x distance. In the same manner it’s not the force that heels the sailboat over it’s the height of the wind times the force of the wind.
Wind force on sails
Mathematically, when you apply wind pressure to a triangle (sail) the center of force can be equated to be at the position of 1/3rd of the way up the triangle/sail.
Here’s a few more equations. Lets assume a right angle triangle.
- Force = pressure x sail area presented vertically to the wind = pressure x foot length x sail height x (cosine (heel angle))/2
- Pressure = ½ (density of air) x (wind velocity)Squared
- Height of force above the sail foot = 1/3 rig height * cosine (heel angle)
- Moment = force x height
Or to wrap it up into easy terms:
Moment is proportional to the following:
- wind velocity squared
- the cosine of the heel angle squared
- the rig height
- the foot length.
In practical terms if the heel angle is 30 degrees the heeling moment is reduced to 75% or if the heel angle is 90 degrees (laying down flat) the heeling moment is zero zip nada.
Also note that in the above, if you go from 5 knots to 20 knots the heeling moment goes up 16 times. In most sailboats you should be looking at reefing anywhere from 12-15 knots. The other thought process to use is when you are starting to think about reefing, you probably should have reefed ½ an hour ago.
What effectively is reefing the sails doing? Well, it’s just reducing the sail area and the height of the position that the wind force acts upon the sails. As an example if the sail was reefed down 15% of its height the area is reduced by 0.85 squared = to 72% of it’s original but the heeling moment is reduced even further because the center of pressure on the sail is lowered . IE reefing has a cubic effect on reducing the heeling moment. Wow that’s pretty enlightening.
Another consideration regarding reefing and heeling is that the more you heel over the less effective is the rudder because you’ve reduced the vertical presentation of the rudder to the horizontally flowing water. IE at a 45 degree heel, you’ve lost 30% of your rudder area which gives you less ability to handle the weather helm from a gust. This can put you into a dangerous rounding up position. And believe me rounding up can be VERY dangerous. One time when sailing along I saw two things about to happen – a gust was on its way across the water towards us and a boat was heading towards us to pass to windward. A rounding up in this gust would drive us right into the oncoming boat. I reached over and let out the mainsheet. This twisted out the top of the sail and effectively lowered the heeling moment but keeping the bottom of the sail powered. The gust passed with out a round up. Just think what if I’d been below and a rookie was helming the boat? No, don’t think!
A sailboat Captain friend of mine who would sail regularly from the Mediterranean to the Caribbean on a 150 fter would always say, if you’re thinking about reefing, you should have yesterday. If you’re thinking about shaking out the reef, wait until tomorrow.
So when should you reef?
- So as you’re not scaring the crew
- At about 25 degrees of heel angle
- At about 12-15 knots of breeze
If you enjoyed this sailing article blog, consider taking the NauticEd Skipper and Sail Trim sailing courses. NauticEd also provides a free sailing course describing the basics of sail trim.
This article was written by Grant Headifen, Director of Education for NauticEd Online Sailing School. NauticEd provides basic to advanced multimedia online sailing courses and a globally accepted sailing certification by most all yacht charter companies.
Docking a boat on to an end-tie or tee head with a strong wind blowing you off requires some knowledge on how to do it and it’s one of those things that you SHOULD practice for WHEN the time comes.
Trying to just sidle up along side like you might do in a no wind condition or where wind is blowing you on to the dock is just not going to work.
Fortunately, there are some simple ways of doing it.
(1) Motoring forward up to the tee head directly into the wind.
Have dock lines prepared and cleated to the forward and aft dock side of the boat.
NOTE: Make sure that the dock lines are run outwards underneath the life lines first then back onboard over the top of the line lines. This ensures that when the line is deployed, it will be clear of the life lines. Since this is usually a crew member doing this, it pays to physically show the crew member when you are out away from the marina if you’re not sure they will do it correctly. Running them inboard and over the lifelines can create a huge havoc at the wrong and crucial time.
Approach the tee head near perpendicular but at an angle so that it makes it as simple as possible for the crew member to step off the boat as far forward as possible. As you reach the tee head the crew member will have to step off the boat and onto the dock. This requires a little dexterity on the crew member’s behalf and good throttle work on your behalf to not hit the dock yet get the crew member close enough with out jumping. Since you’re headed directly almost into wind, you’ll have afforded some time with the bow at the dock so that the crew member can take their time carefully stepping off the boat and onto the dock.
The crew member now cleats the dock line to the dock cleat in the direction of where the aft of the boat will sit using about ¼ of the boat length of line between the two cleats.
Now comes your part. Turn the wheel all the way to the stops to the non-dockside side of the boat (tiller to dockside side) and engage forward gear. This creates a sideways force on the rudder and will push the stern of the boat to the dock. Adjust the throttle to over come the windage force on the boat.
DOCKING A SAILBOAT INTO THE WIND
(2) Motoring in reverse up to the tee head directly into the wind.
This method works especially well when the boat has a swim platform and walk through transom.
As above, have dock lines prepared. Then back up to the tee head.
NOTE: You’ll learn in the NauticEd Maneuvering a Sailboat Under Power online sailing course that a boat’s stern facing the wind is an extremely stable position and you will not get bullied around by the wind. You’ll also learn that backing into the wind is extremely easy. If you haven’t already, take the NauticEd Maneuvering a Sailboat Under Power online sailing course.
The crew member steps off the boat holding the aft dock line when the stern is close enough and cleats the dock line to a dock cleat that lies in a direction more aft of the boat in its final resting position. Again about ¼ of the boat length of dock line should be allowed between the aft cleat and dock cleat.
Turn the wheel all the way to the stops towards the dock (tiller pointing away) and engage forward. This will swing the bow of the boat in towards the dock against the wind. Another crew member can toss the forward dock line to the crew member on the dock to aid. Or if the 1st crew member is able they should take a long forward dock line with them when they stepped off the boat originally.
DOCKING A SAILBOAT INTO THE WIND
Either of these methods can get you docked safely. And, practiced, a day skipper could do all the above solo.
Practice both of these a few times and when the real moment comes, you’ll be looking like a pro. Rather than a…
This docking a sailing boat tip was written by Grant Headifen , Director of NauticEd. NauticEd offers an excellent Maneuvering a Sailboat Under Power online sailing course as well as many courses on how to sail a boat.
The posting here is not a course in celestial navigation by any means. However it’s meant to simplify a few principles for you so that you’ll at least have some sort of celestial orientation. And… perhaps it’ll inspire you to learn the aging art.
This was written by Grant Headifen, Educational Director of NauticEd. NauticEd provides online sailing courses and Sailing Certifications accepted by charter companies worldwide.
Latitude: In the northern hemisphere, finding latitude is simple using one of the greatest gifts to human kind – The North Star. What ever angle the northern star is at from the horizon, that’s your latitude.
Imagine you’re an ant sitting on the top of an apple looking at a spot directly above you on the ceiling then the spot is 90 degrees from the surface you’re standing on. If you’re standing half way around the apple then you’d barely see the spot but it would be horizontal to the surface you’re standing on and so the spot would be at zero degrees. And if you were ¼ of the way down the apple then the spot would be at 45 degrees etc. ie the northern star is the spot on the ceiling to us.
You can also find latitude using other celestial sightings but they involve table lookups and are slightly more complicated. Not meant for this post and also note that there are a few more complicated variables not taken into account during this simplistic explanation like the height of your eyeballs above the earths surface etc etc. But at least you’ve now got the principle.
Longitude: Now this is a fun one and in an incredibly easy principle. But years ago (early 1700′s) while the principle was easy then the execution was difficult. Read on to see why.
The earth rotates through 360 degrees in 24 hours. That’s 15 degrees per hour. By convention, when the sun is at it’s highest point in Greenwich, it is noon in Greenwich. That means that at a place that is 15 degrees to the West of Greenwich the sun will be at it’s highest point one hour later. Six hours after Greenwich the sun will be at it’s highest point somewhere in over the USA and 12 hours later the sun will be at it’s highest point in New Zealand.
Animation of time zones
So if we know the time in Greenwich and sun just reached its highest point where we are then we can calculate our longitude.
Lets do a few examples. If it is 6 pm in Greenwich and the sun just peaked overhead here, then I am 6 x15 degrees to the west of Greenwich which is 90 degrees West which is right near St Louis Mo.
If the sun peaked overhead in Los Angeles what time would it be in London.?Well LA is 118.15 degrees West (from Google earth). Divide that by 15 degrees per hour and we get 7 hrs 53 minutes. Now since the times zones are created in bands this would round up to 8 hours. Thus it would be 8pm in London.
You’re sailing in the Greek islands in the Mediterranean and a little bird just told you your latitude is 34 deg 54 minutes north but failed to tell you the longitude. Fortunately you have your handy sextant and just as you take a shot, the sun just reached its apex overhead. You look at your watch and the local time is 12:10:48 pm. Where are you?
Since you’re in time zone B you are 2 hours ahead of Greenwich. Thus the time in Greenwich is 10:10:48 am. And since the sun peaked just now (=noon) then you are 12:00:00 minus 10:10:48 = 1 hour 49 minutes and 12 seconds from Greenwich. Putting this into decimal time this is 1.82 hours. Multiply this by 15 degrees per hour and we have 27.3 degrees East or 27 degrees, 18 minutes East.
You’re in the harbor north of the town of Kos on the Island of Kos.
That was incredibly easy, so why all the hoopla back in the 1700′s? The King of England even offered up a ₤10,000 reward to anyone who could solve the issue of Longitude. The above math was well known but the issue was telling the time. No one could accurately keep time at sea. After 27 years of work on the project, John Harrison, finally invented the Chronometer more commonly known as the watch. The watch was not susceptible to the sudden crashes of waves at sea and thus kept proper time.
James Cook on his second trip around the world in 1772 sailing on Rendezvous, took Harrison’s watch with initially much skepticism. Stating that he’d give it a try. After six months at sea, Cook stated that the Chronometer would almost certainly become the way of the future for Navigators. Cook then went on to reposition many of the Islands in the Pacific including Tahiti, his favorite island. His map of New Zealand astounds people even today with its accuracy.
Again there were a few simplistic assumptions taken in that explanation. But now, at least you understand the principle of longitude determination from a noon shot of the sun. You can also determine your latitude from a noon shot of the sun as well using tables and a bit of math. Again beyond this posting.
If you’d like to delve deeper into these topics, NauticEd provides online sailing lessons and an Introductory Celestial Navigation Sailing Course, or maybe you’re just happy with your handy boring ol GPS.
Here is a question from a student regarding letting out the main traveller in a gust.
I referred them to this post
which talks about moving the traveller upwind and letting out onthe mainsheet to increase twist at the top of the sail and thus reducing the forces aloft.
Greetings from Northern Michigan and the Great Lakes-
I have enrolled in your Catamaran Sailing Confidence Course in preparation for my first bareboat charter in the BVI’s on a 47ft Cat. In the section on sailing you state:
When sailing closed hauled on a catamaran in heavier air, move the traveler up wind (on the opposite side of the sail) and let off on the main sheet. This will allow the boom to rise a little and “twist out” the top of the sail. Twisting the sail allows you to let some of the top part of the sail “deflate” in case of slightly stronger winds. In light air, make sure that the top of the mainsail is not “loosing air” meaning, keep the traveler close to the center and tighten the mainsheet pretty good to make sure the main cannot open up at the top.
I am a crew on a 26ft monohull that races and when trying to go upwind we move the traveler to a windward position and try to keep the boom centered with the mainsheet (we also tension the outhaul and backstay). During heavy or gusty winds when weather helm and heel require us to depower the sails we will move the traveler down to center or leeward (rather than simply letting out the mainsheet and having the main luff) and this serves to “spill some air” and depower the mainsail. It certainly has worked to decrease the heel of the boat. This would be followed by reefing as winds increase.
So I have learned that in a close haul to move the traveler down to depower, but your statement is to move it upwind and I am therefore confused. What am I missing?
Thanks for your wisdom-
Here’s a question from a student regarding docking a sailboat after they took the Maneuvering Under Power Sailing Course
I have a question in reference to the maneuvering under power:
Under the excersice end ties #3, wind from behind, once you have backed the boat to the dock and secured the stern spring line, should the wheel be turned toward the dock and throttle into forward to bring the bow to the dock?
You’re absolutely correct.
Here is a vector force diagram to match. Actually, as you can see, you could do it with out turning the wheel to the dock but the resultant torque (turning moment) would be reduced. Turning the rudder creates extra turning moment. It doesn’t really matter which direction the wind is coming from with this method. Altho if the wind was high and blowing you off the dock. I would do the front spring first, then drive forward with the wheel turned away from the dock.
Docking a Sailboat