Posted by Grant Headifen on August 12, 2010 under Bareboat Charter, Crew, Maneuvering Under Power, Skipper | 
Next week we’re going to Tonga and the island of Vava’U for a week long NauticEd Flotilla sailing trip amongst the archipelago. After a rainy and relatively cool winter in New Zealand this year its going to be a welcome and fun trip. We’re bareboat chartering three catamarans from the Moorings. 21 adults and 3 three children aged 2, 3 and 6 are coming. Correction that makes 24 children I think by the excitement and way every one is acting so far. We’re looking forward to doing some excellent sailing, fishing, swimming in warm water, snorkeling under the rock wall into Mariner’s cave and maybe have a few lovely glasses of red wine under a warm evening sky. So in light of catamaran sailing then I thought this week we’d review a method of getting a catamaran off the dock when a difficult wind is blowing onto the dock. We needed to use this in the British Virgin Island last year and with some whacky wave action we also had to time it right. It’s just as well we used this method because, with the waves, some serious damage could have occurred.
Using a spring line to get off the dock with a catamaran
The concept is pretty simple and effective. First tie a dock line from the front of the boat to the dock towards the aft. Then turn the helm all the way towards the dock and engage the out side engine in forward. The thrust from the backward wash of water as depicted by the arrow onto the turned rudder plus the force moments from the outer thrust and inner dockline will act to turn the back end of the catamaran out away from the dock. You must position a crew member with a dock fender to hold it between the boat and the dock. When the boat is turned out a significant amount, you can engage reverse but make sure it is more than 45 degrees out, else you can be in trouble with the wind pushing you back onto the dock. Once in reverse, turn the helm the other direction to get the boat moving in the right direction. Wait until the boat is a significant distance away from the dock before you decide to engage forward and swing the boat around otherwise the back quarter of the boat can broadside back into the dock, especially if the wind is strong.
You can apply a little reverse thrust to the dockside engine but keep it so that the tension remains on the dock line. The method of using the dock line rather than just opposing engines turns the catamaran more effectively when operating close to the dock because the dockside front quarter is essentially trapped thus a simple rotation won’t work.
Make sure that the dock line is arranged so that it is tied to the boat then looped 1/2 turn around the dock cleat then back to the boat. In this manner the crew member managing the fender can, at the right time, release one end of the dock line and pull it back around the dock cleat to retrieve it – all the while standing on the boat as it pulls away from the dock. Make sure the end has no knots in it. Also ensure the crew member understands not to release the dock line too early because they will not be able to hold against the thrust force.
Obviously this concept works similarly for monohulls.
Full concepts of maneuvering sailboats under power and catamarans are covered in these two NauticEd sailing courses. http://www.nauticed.org/courses/view/maneuvering-under-power and http://www.nauticed.org/courses/view/catamaran-sailing-confidence
Posted by Grant Headifen on July 13, 2010 under About NauticEd, Bareboat Charter, Crew, Skipper |
Rolex Regatta St. Thomas
Join us on an 80 ft Maxi Yacht in the Rolex Regatta.
In the movie “Hunt for Red October” the XO came to Sean Connery and said: “Captain, it is time”. It was the time to make the decision to go for it – or not. And it is now one of those classic movie lines you just can’t forget.
Well everyone, that time for you is now!
Join us on Kialoa a 80 ft maxi yacht
NauticEd along with sailing adventure partner, Safe Passage Sailing, are chartering Kialoa V, an 80 ft (25m) Maxi yacht to participate in the Rolex Regatta (the “Crown Jewel of Caribbean Racing”) in St. Thomas in March next year.
On board will be world-class sailing and winning professionals Rich Stearns and Brian Thompson along with NauticEd’s Educational Director, Grant Headifen to lead us through the weeklong event and … hopefully win.
The event consists of 2 training and preparedness days followed by 3 race days out and around the various island of St. Thomas and St. Johns.
Because of the reasonably serious nature of operations on such a large yacht, we will be requiring a certain level of sailing experience to sail on this Maxi yacht so you’ll need to ensure you fill out your NauticEd Sailing logbook under your login account.
See our successful Antigua Sailing Week Video.
We have space for 10 more crewmembers only on this 80 ft yacht so in order to participate you must register your interest with us NOW. Accommodation in local rental Villas is available but these will disappear fast after that the hotels can get quite pricey so contact us now to get moving on this opportunity.
Accomodation can take place in several rental villas that we have identified – BUT … these will go fast so you really should contact us fast.
Send us an email to: info@nauticed.org / subject line: Rolex Regatta Interest
See our brochure on the Rolex Regatta which contains the itinerary, costs, professional hired crew resumes, etc.
Discounted rates for 4 or more so update your facebook page, send out a tweet and bring a few friends!
Back to NauticEd Sailing School
Posted by Grant Headifen on July 6, 2010 under Bareboat Charter, Coastal Navigation, Crew, Skipper, Storm Tactics |
As you learn to sail, you should be also learning about anchoring. There is more to tossing the hook so to speak.
After doing some research on the internet and looking at some of the tests performed on holding power, I’ve made a quick summary of what I learned.
Anchor types are selected based on the bottom conditions. These are rock, mud, clay, sand, grass, coral and shoal.
Charts will usually tell you what the bottom conditions are, as will local sailors from whom you should never be afraid to ask.
The following shows the type of anchor and the associated bottom that the anchor is best suited for.
Danforth: Works best in sand and mud
Danforth Anchor
Hinged Plough CQR: Works Best in sand, rock and mud.
Hinged Plough CQR Anchor
Non Hinged Plough Delta Anchor: Works best in sand rock clay and mud.
Delta plough anchor
Non Hinged Plough Roll bar anchor: Best for all types of bottoms – sand, rock, mud,clay, grass
Rollbar plough anchor
Bruce Anchor: Best for sand, rock, mud.
Bruce anchor
The Roll Bar Plough type anchor is a new type of anchor and therefore is not that common yet. However, tests show that it is certainly one of the winners when it comes to selecting an anchor.
Posted by admin on July 3, 2010 under Bareboat Charter, Coastal Navigation, Crew, Skipper, weather |
As a new sailor, just learning to sail, the thought of figuring out tides can be quite intimidating. We know that even some seasoned sailors tend to just wing it – a dangerous concern. This learn to sail series article will dispelled any concerns about understanding, reading and predicting tides.
Gravitational Pull
Tides took a lot of figuring out by some very smart people over the ages including Galileo.
But now that the principle causes of tides are understood and quite well mathematically modeled, they are pretty easy to understand by the average Joe when explained properly.
Tides exist solely because of the celestial bodies the moon and the sun. The moon is relatively close but comparatively small. The sun is far away but a giant when it comes to mass. Gravitational pull increases linearly with mass but decreases inversely with the square of the distance. So when you balance these out and do the calculations, the sun’s effect is 46% that of the moon.
So the moon has the dominant and most noticeable effect on the earth’s tides. However the Sun still has a significant effect.
There are a couple of tricks to understanding the tides that took the physicists quite a while to figure out in the old days. The moon circles the earth about every 24 hours and 50.4 minutes. But for most of us it seems that the tide takes about 6 and a bit hours to go out and 6 and a bit hours to come back in. That’s a frequency of 12 and a half hours not 24:50 hours. What’s up with that?
Tide is actually a gravitational concept rather than specifically related to the movement of our oceans. All celestial objects are susceptible to tidal effects from other “relatively close” bodies. Consequently a planet with in gravitational range of another body will experience pull leading to stresses acting to deform the shape of the planet.
That means that as the moon circles the earth, the earth is deformed by the moon. Similarly, the moon also experiences deformation by the earth and thus is suffers a tide effect. The effect is called tidal force. Fortunately for life on earth, the deformation is small but it does lead to the rising water that we experience. Therefore, with out the moon, life on earth would be vastly different.
As non celestial body and gravitational experts we’ll probably struggle to understand the resultant effect because it happens in a way that we might not initially expect.
Double Bulge Phenomenom
It is suffice for this description of tides to state that the planet doesn’t just bulge towards the distant body but actually bulges on both sides in a line between the center of the two bodies because of the volumetric stress imparted upon the planet. Various arguments still exist on why, some are flat out wrong and some are right. As sailors we really don’t care too much other than knowing the resultant.
To gain a visual appreciation for this, although not in anyway accurate in science, take a calamari ring and hold in two points opposite each other. Now hold one side still and pull the other side. You’ll see the ring bulge on both sides in a line of the direction of pull.
That is a similar resultant action to what the earth is experiencing. The bulge occurs on both sides of the planet diametrically opposite each other and in the plane of a line between the moon and the earth. So following this, we have a high tide on the same side of the planet as the moon and simultaneously on the opposite side. Thus leading to a theoretical tidal period twice for every rotation of the moon about the earth.
The double bulge concept has nothing to do with the spin and inertia of water on the earth, although you will find some arguments and textbooks reporting this as a contributing factor to the opposite bulge. Not so! In any case, again as sailors we don’t necessarily care too much. We just need to know and realize that the double bulge occurs to explain two tides in a day rather than matching the periodicity of one moon rotation per day.
The exact same concept is valid for the sun. A solar high tide exists on the same side of earth as the sun and simultaneously on the opposite side of the sun.
Theoretical Tide Heights
Now let’s look at a few theoretical mathematical numbers for comparison. If the earth’s oceans were uniform in depth and no landmasses existed and just considering the moon and if the moon was rotating around the earth every 24 hours, plus a few other ands and ifs, then the theoretical rise of the water at high tide would be 54 cm (21 inches). Now consider the suns effect in the same way. This would lead to a theoretical tide rise of 25 cm (9.8 inches). If the moon and the sun aligned or were directly opposite (from the bulge theory above) then we could add these heights together and get 79 cm (31 inches). If the moon and sun were acting against each other by being 90 degrees apart, then we would subtract the numbers and be left with a tidal height of 29 cm (11 inches).
The phenomenon then of a spring tide has thus been explained. Spring tide is when the sun and moon align or are diametrically opposite. The word spring does not come from a relationship to the season but from the concept of “force”. Meaning there is more force during this period of alignment, which occurs about every 14 days – full moon and new moon.
Consequently, a neap tide is the minimal tide effect from the action of the sun and moon opposing each other. When they are at 90 degrees from each other – not diametrically opposite each other due to the double bulge effect. Again, this occurs at a period of every 14 days.
In addition to the above, the sun and moon operate in elliptical orbits relative to the earth. You can then imagine as the sun and moon become at their closest points to the earth that a greater effect would take place. The effect is increased 18% for the moon and 5% for the sun. Since the earth rotates about the sun once per year, at a certain times of the year then you would expect all these phenomena to exist simultaneously and create a theoretical tidal height of 93 cm (37 inches).
You can also imagine a common high high tide condition existing when the moon is closest to the earth with the moon and sun aligned (or diametrically opposite). This is called a perigee spring tide and occurs every 7.5 moon cycles.
This can be further expanded to include the sun being at its closest point along with the moon and in a spring tide situation. This occurs every 18.6 years. For this reason tidal high high and low low measurements are recorded and reported over periods of 19 years by statistical governmental recording agencies.
There is one last effect to discuss and that is that the sun and moons orbits are not directly aligned with the pole of the earth. Both the sun and moon’s orbits are not in unison and change day by day. For this reason the height of each high tide will vary day by day.
And just in case you’re wondering, Venus provides the next greatest tidal effect on the earth. But it is less than 0.001% of the magnitude of the Sun’s effect.
We’ve added a rudimentary animation of the Moon’s and the Sun’s tidal forces on the Earth at http://www.youtube.com/watch?v=XZNnb9YP1xg. The animation shows the Moon’s larger tidal force in blue and the Sun’s smaller tidal force in yellow turning relative to the Earth with different frequencies. You’ll need to view it several times through to see that when the bodies are aligned either on the same side or diametrically opposite, that the tidal forces align creating a spring tide. You’ll see Neap tide occur when they are 90 degrees apart. Of course in reality, the earth rotates about the sun but for relativistic purposes of an observer standing on the Earth, this demonstrates the effect. Additionally we did not simulate the 7.5 lunar periods before the cycle repeats nor did we show differing declination of the orbits or the elliptical shape of the orbits … and a few other things.
How the Tides Work
In Reality
So now let’s take out some of the theoretical arguments and start adding back in landmasses and differing ocean depths. The effect is called Bathymetry. These affects greatly affect the timing, tidal heights and periodic frequency of the tides at different places on the earth. Regardless of this, the tides still occur with periodic consistency in each location according to the above discussion of the moon and sun movements. This last sentence, matched with empirical data over time, means that tidal predictions are very accurate, both height wise and time wise.
Lets say that again; Tides heights and times are highly predictable!
Most places on the planet experience two high tides every 24 hours and 50 minutes as discussed above. This is called a semidiurnal tide. However due to bathymetry, some places experience one high tide every 24 hours and 50 minutes. This is called a diurnal tide and is experienced in the South China Sea, the Gulf of Mexico along with a few other places. Another significant departure from the theory is the experiencing of two differing height of tides. This is called a mixed tide and is experienced in quite a few places including the west coast of the United States.
Keep in mind that 100% of the reason for departure from a semidiurnal tide in these locations is solely due to Bathymetry. Bathymetry is also the reason for departure from the high tide being at exactly the same time as the moon at its highest apex in the sky overhead (or diametrically opposite the planet). As an example, in Norfolk Virginia USA, high tide is approximately 2 ½ hours before the moon passes overhead. Typically on the planet, a spring tide occurs 2 days after a full or new moon.
Bathymetry also explains why tidal height in some places is far greater than the theoretical predictions above. As water moves and slushes around the planet it does so with lunar (and semi lunar) frequency setting up a crowding effect of the water in certain places.
Regarding all the above discussion about high tides, for every high tide there is a corresponding low tide. As sailors, we’re pretty concerned about low tides and low low tides due to grounding issues. For mixed semidiurnal and semidiurnal tides, low tides occur every 12 hours and 25.2 minutes. Low low tides occur at spring tide every 14 days about 2 days after a full moon or new moon. And lowest low tides occur every 7.5 lunar cycles when there is a perigee spring tide situation.
The Tidal Map
Putting it all together, and considering the periodic consistency, bathymetry and real empirical data, NASA has developed a tidal map of the planet. The map is quite revelational and will help you understand tides even further.
Tidal Map of the Earth
Grey parts are landmasses. The colors on the map represent the amplitude (height) of the tide. Note the locations marked in red. These are well known really-really high tide areas. Some in excess of 40 feet (11m). Also if you’ve ever sailed in the Caribbean or Mediterranean, you’ll have noticed a distinct lack of any tide. These are marked in Blue.
Of particular interest for me is the west coast of my home country, New Zealand. Near Auckland, two estuaries, one from the west coast and one from the east coast are separated by about 500 meters of land only. Yet the tidal difference is hours apart and the two tide heights are vastly different. Similarly take a look at the area around Panama. Extreme high tides exist on the west coast and almost none on the east coast. The UK also has some very interesting tidal results particularly in the Solent area.
The highest tides in the world can be found in Canada at the Bay of Fundy, which separates New Brunswick from Nova Scotia. At some times of the year the difference between high and low tide in this Bay is 16.3 meters (53.5 feet), taller than a three-story building. Anchorage, Alaska, comes in at a close second with tidal ranges up to 12.2 meters (40 feet).
The white lines on the NASA map above represent one hour difference in time for a high (or low) tide. Note how the lines appear to be randomly placed around the planet with out any particular reason for their placement. Again this is due to bathymetry. Of note however is that over time, the lines are don’t move. For example the blue region in the middle of the south pacific where the white lines converge always experiences little to no tide. The high tide travels around this point in a clockwise direction. The amphidromic point where the lines meet defines the meeting point of high and low tide giving rise to a consistent zero tide effect. In fact, at most amphidromic points as such in the southern hemisphere, the tide turns clockwise due to the coriolis effect of the earth spinning. In the northern hemisphere at most amphidromic points the tide turns anticlockwise (counterclockwise).
What does this really mean? It means that if you consider the amphidromic point near Hawaii and the radical lines from it incident on the west coast of the USA, then the high tide must move north along the coast over time. IE the high tide in Los Angeles will be after the high tide in San Diego (San Diego being south of Los Angeles). Of significant value when understanding this is that if you can read a table showing the high tide in one place you can predict the time of the high tide in another location. Look at the southern part of the south east coast of South America. The high tide occurs all along that region at almost the same time but over approximately the same distance along the east coast of New Zealand, that experiences 5 hours of high tide time difference. Interesting!
It is doubtful that even the most complex mathematical models could predict all this. However combining the empirical data with the periodic frequency of the two celestial bodies gives us every thing we need.
Practical Application of Reading And Understanding Tides
Whether we’re experienced sailors or just starting out in our learn to sail quest, chances are you’ll be sailing in an area where tides are happening.
One of the greatest reasons you need to understand and deal with tide heights is when you are anchoring. Anchor at high tide and you might find your self stuck tipped sideways on the ocean floor a few hours later. Anchor at low tide and with a lee shore and you might be blown onto the rocks when your anchor scope becomes less than sufficient to allow the anchor to hold.
Tides are also significant when dealing with bridges. Cleverly, charts list bridge heights as height above high tide not low tide.
There is some language around the practical application of tides that we now need to learn.
- Ebb tide: Water going down towards low tide
- Flood Tide: Water coming up towards high tide
- Slack Water: Times when the water movement due to tidal effects are minimal. Note that because of the time it takes for bays and estuaries to drain out, slack water is not necessarily at high tide and low tide. Consult current tables to learn slack water times.
- MHHW: Mean higher high water level. Average height of high tides at spring high tide
- MLLW: Mean Lower low water level. Average height of low tides at spring low tide
- Chart Datum: Reports of water depth on charts are taken at MLLW
- Bridge Heights: Reported on charts as the height above MHHW
- Tide Current: Flow of water due to tides
Below is a tidal prediction chart for a buoy position in La Jolla, San Diego, California. Note a few things: (1) The prediction is extremely close to the observed. (2) That it occurs twice per day – Semi diurnal (3) The heights are different with in the same day – Mixed Semidiurnal. (4) The low tide drops below the MLLW.
Tide Data in San Diego
Rather than carry around masses of graphs as above, convenient tide tables have been produced by the maritime agency in almost every country that borders an ocean. Visit you local chandlery and they’re bound to have a copy of the local tide table. Or search on the Internet. In the USA go to http://tidesandcurrents.noaa.gov/tidesXX – where XX represents the last two digits of the year you want to explore. Tide table are abundantly available to us.
So whenever we want to know the time and height of the tide we can just consult the tide tables. And from the above, we now know and are very confident that, they will give us a very accurate prediction. Tables are arranged to give us tidal heights and times at most well known ports called Reference Stations. Time and height adjustments are then provided to get predictions for lesser known ports that are called Subordinate Stations.
To predict your tidal information from written tables find the closest Reference Station, then make the time and height adjustment from that Reference Station to your closest Subordinate Station. Because of the power of computing, on the Internet, many Subordinate Station calculations are already done for you. In this case you can just look up the tide heights and times directly at your location. Most of us don’t carry Internet connected laptops on our boats so the ability to read and understand the table is paramount.
For example, from a table you might read the time and height of the low tide on the afternoon of January 15th 2010 in Los Angeles. But if you are further north in El Segundo in Santa Monica Bay, the tide will be slightly different. From the NASA developed tide map above you at least know that high tide will occur later because of the anticlockwise turn of the amphridomic point near Hawaii, but by how much time and by how much amplitude? Thus we consult an adjustment table.
Below is a typical tide table for Los Angeles. Click the image to go to this page on the tidesandcurrnet.nooa.gov website.
Tide in Los Angeles
You can read (probably with glasses) that the afternoon low tide occurs in Los Angeles port at 3:46pm and is 0.7 feet below the MLLW chart datum.
Correction tables will show that for the Subordinate Station of El Segundo, the correction from the Reference Station of Los Angeles will be to add 13 minutes for low tides and to add 13 minutes for high tides. And to multiply the low tide reported in Los Angels by 0.96 and the high tide by 0.96.
Correction of Tide for El Segundo
Thus the afternoon low tide in El Segundo will be at 3:59pm and will be 0.67 feet below MLLW.
The below table confirms that result. Click the image to go to this page on the tidesandcurrnet.nooa.gov website.
So there you have it. You completely understand tides and can now use the table to predict tide times and heights.
Of considerable further interest is the currents produced from tides. These must also be understood, especially as sailors, because in many cases your sailboat can not sail as fast as the tidal current. San Francisco Bay is a good example of this. Module 1 of the NauticEd Skipper Course (http://www.nauticed.org/courses/view/skipper) discusses Tidal Currents and their prediction.
This article was written by Grant Headifen, Educational Director of NauticEd. NauticEd is an online sailing school providing sailing courses and sailing certifications for beginner to advanced sailors.
For more info see http://www.nauticed.org
Posted by Grant Headifen on June 29, 2010 under Bareboat Charter, Crew, Sail Trim, Skipper |
I once sailed with an ex-submarine captain who would turn the boat through a tack extremely slowly. When asked why, he had several good reasons.
(1) Look behind you as you come about. If you are leaving swirling water eddies behind the rudder, these are a sum of kinetic energy that was previously in your sailboat but has now been released to the water. What does that mean? If you jam the tiller over during a tack you will loose momentum – slowing down your sailboat more than you need to. If you execute an easy steady turn leaving the kinetic energy in the boat, you’ll maintain kinetic energy in the boat.. Thus when you come out on the other side your boat still has speed. Still not convinced? You’ll remember from docking that the boat carries a lot of momentum. Put the throttle in neutral and the speed bleeds off very slowly. Ever been skiing? Execute a few cutting turns and you’ll see how fast your speed drops. Same concepts when tacking.
(2) A slower turn also allows your crew a few extra seconds to get the jib sheet in tight before the real heel and tension comes on. This is really important because once you’re heeling over on the new tack it is more difficult and slower for the crew to tension up the jib sheet to it’s appropriate trim. It’s pretty frustrating as helms person when you’re perfectly on the new tack and you’re watching the crew floundering around cranking slowly on the winch and the jib is still only half in. You’re probably yelling “get it in get it in” and watching others pull past. What I’m doing here is putting a little responsibility back on you. With a slower turn, the crew can get the jib sheet almost all the way in by hand before the tension comes on.
(3) The swirling water eddies left a signature in the water that could be picked up by submarine hunting satellites. Not that this is relevant to sailing really but it was just his well formed habit.
The point is – when you’re the helms person, maintaining speed through the tacking maneuver is a balance between your boat’s momentum profile and your crew’s efficiency in getting that sheet in. It’s not about jamming the wheel over to the other side as fast as possible.
Just goes to show you that slow is faster. Ask the tortoise!
Posted by admin on June 22, 2010 under Bareboat Charter, Coastal Navigation, Crew, Sail Trim, Skipper |
Leeway is just one of those things that is a law of the universe that we have to put up with. It’s just like gravity. Still with gravity – the advantage is that it’s highly predictable. And so then is leeway.
Leeway is the sideways slip motion of our sailboat down wind from the pressure of wind against our boat and sails. It results in a course that is less than desirable.
Leeway Slips Your Boat Side Ways Down Wind
Airplanes suffer from the same issue. When flying in a cross wind, the plane crabs (slide slips) downwind. The course becomes different from the heading.
Not accounting for leeway will have you sailing (or flying) in a fairly unnoticeable arc to get to the mark. To represent an example with a mark to the north and a westerly crosswind, here’s what happens; you aim for the mark at 000, your boat slips sideways to the west. Now your mark is at 359 but you don’t really notice it. After a few minutes your mark is at 358 still in noticed. Minutes later your heading is 355 then 350 etc. All because you keep aiming at the mark but you’re being pushed to the east by the wind. Your course over ground becomes an arc and is the long way around.
The prudent sailor will account for the leeway and sail a constant heading depending on their known leeway of say 350 for the example above. The sideways slip motion will deliver them to the mark in a straight and shortest line.
Now that we’re in the electronic age, navigators will plug in the destination to the gps. The autopilot which is cross talking to the gps takes care of the rest. The gps analyses the cross track (the boat’s distance away from a straight line to the mark) and feeds back to the autopilot the proper heading to minimize this in real time. Thus resulting in a straight course to the mark.
I’m doubt that during the Wednesday/Friday night beer can race such electronic methods are utilized. So I’m suggesting that to take line honors and win the bottle of rum at your club race by taking account of leeway.
Leeway is particularly more prevalent when you are sailing on a close haul or close reach and can be as much as 20 degrees depending on the wind conditions, water conditions, your sailboat design, your apparent angle with the wind and how your sails are set.
However, other than buying a new boat, the only thing that you have control over is the trim of your boat and sails.
Here’s a couple of general rules to follow:
- Over sheeted sails cause more sideways force and thus sideways slip (leeway). Fly the telltales diligently.
- Aim for a position to windward of the mark you’re trying to go around. The more you are sailing on an upwind course, the more the degrees upwind you should aim.
- The higher the wind speed, the higher above the mark you should aim.
- In general, on a close haul, allow 10-15 degrees. Adjust this less if the wind is light, more if the wind is strong. Reduce this amount linearly as you bare away from the wind.
When doing serious navigation we absolutely must account for leeway and an excellent understanding of how your boat performs leeway wise is essential and how to solve for it once you know it. NauticEd developed an educational navigation video solving a leeway and current exercise at http://www.youtube.com/watch?v=1LQcFOGSJQs
Using a gps and a nice steady windy day, you can do a simple determination of your sailboat’s typical leeway.
(1) Begin sailing on an angle slightly off a close haul direction and with a recognizable land marker dead ahead.
(2) Measure your speed
(3) Douse the sails and begin motoring at the same speed in exactly the same direction.
(4) Take note of your gps course.
(5) Deploy the sails and turn off the engine.
(6) Continue to aim for the same point on land.
(7) Now read out your gps course.
(8) The difference in course angles will be your leeway
(9) Repeat for different points of sail
(10) Repeat for the opposite tack.
(11) Repeat on different days with different wind strengths
Note that:
(a) this method is relatively immune from current because you have normalized it out by performing the motoring task.
(b) this method will not account for the leeway due to the hull of your boat presented to the wind.
We hope you enjoy your bottle of Rum!
Posted by admin on June 16, 2010 under Crew, Sail Trim, Skipper, weather |
During the Americas’ Cup campaign in New Zealand in 2003, I saw one of the best explanations of this on a TV interview with the Greg Butterworth, the Tactician for the Alingi Team.
Most of us sort of understand the concept and we’ve been left with the answer of “Well – weather helm is better because it’s safer.” But few explanations go into how it gives your boat a sailing advantage.
The definition of weather helm and lee helm is simple and it is easy to remember which is which. If you have a tiller, weather helm is when you have to pull the tiller to weather (toward the wind) in order to keep the boat going in a straight line. Lee helm is when you push the tiller to lee (downwind) in order to keep the boat going in a straight line. We’ve probably all felt this slight pressure required on the tiller when underway.
Your boat can be tuned to give weather helm or lee helm. Rake the mast forward and you move the center of effort of the wind forward which causes your boat to want to turn downwind. Rake the mast back and you move the center of effort of the wind back causing your boat to want to go upwind to weather.
When your boat gets rounded up – you just experienced massive weather helm. No matter how much you pull the tiller to weather, you can’t stop the boat going to weather. Dumping the main sail moves the center of effort forward thus reducing the weather helm.
The basic perception of weather helm being safer comes from this effect: if you let go of the tiller, it will automatically go to center because of the water flowing over the rudder and because the rudder is pivoted at its leading edge. Now there is no rudder force to counter the desire of the boat to turn up wind to weather so the boat does exactly that. It turns to weather and rounds up slowing the boat down and reducing forces on the rig. Conversely, lee helm means that if you let the tiller go the boat will turn away from the wind, heel over more increase forces on the rig.
So from a safety point, weather helm is good. BUT there is another advantage that we’re not generally taught. Holding the tiller to weather means that there is a slight pressure on the rudder to windward. This actually MOVES THE BOAT TO WINDWARD as it slices through the water. And we all know what that means, race advantage!
The Weather Helm Advantage
The illustration shows how the water pressure from weather helm creates a sideways force on the rudder tending to push the boat to weather.
Now Greg Butterworth went on to explain that there are other cool things you can do. One is to put a little trailing edge swinging control surface on the keel.
The illustration below shows this effect too. For us pilots, this is much like a trim tab on a wing of a small airplane. The trim tab creates the ability to adjust the lift at that point on the aircraft and thus create a balance of forces. The issue to remember here is that you’d need to trim the tab the other way when you tack over.
A control surface on the keel
So there you have it. While we’ve all been understanding the lifting effects of the wind over the sail, the other fluid that we’ve ignored is the water under the boat and how we can gain lift from it too.
Next time you’re out sailing on a nice steady 10 knot breeze, come up on a close haul, trim the sails perfectly so that all your tell tails are flying smoothly. Then notice what pressure you’ve got on the helm. Note that if you’ve got a wheel, weather helm will be a tendency to apply downwind turning pressure on the wheel (which is the same as pulling a tiller upwind right?). Ideally you should have slight weather helm. If not, you should probably not jump right in and start raking your mast back. Talk to a mast tuning specialist in your area first.
Posted by Grant Headifen on June 8, 2010 under Crew, Sail Trim, Skipper |
Rounding up is caused by many factors. One is too much wind and force aloft which tends to heel the boat over. This reduces the amount of rudder in the water and thus the rudder’s effectiveness. Another factor in rounding up is the center of pressure of wind on the sails is too far aft which then pushes the aft of the boat downwind and thus the front of the boat up wind.
The NauticEd SailTrim clinic discusses this topic and so what we wanted to do was test it out for sure. So last weekend we took out a friend’s Beneteau 373 to test out an anti-round up theory. Read on to find out the results of our experiment.
First though, we must first understand wind shear. The phenomenon of wind shear is pretty easy. Wind moves faster at the top of the mast than is does at the water level because the stationary water slows the down the wind in close proximity.
Secondly, consider the concept of true wind vs apparent wind. Which is best understood by imagining driving your car in a cross wind with your hand out the window of the car. At stand still you would feel the wind coming from the side of the car. The faster you go, the more you feel the wind coming from the front of the car. But when a gust of wind comes (which is just an increase in true wind speed) then you would feel the wind shift back more to the side. When relating this to a sailboat, if your boat was standing still, the wind at the top of the mast would be the same apparent direction as at the cockpit level albeit, faster (from the wind shear phenomenon). However as your boat picks up in speed the apparent wind moves forward BUT because of wind shear it shifts forward less at the top of the mast. IE at the top of the mast the wind tends more to the direction of true wind direction because the true wind speed is higher. Thus at the top of the mast the true wind is more aft than apparent wind. Aft means it is coming from a direction further towards the back of the boat. Get it?
So – whether you get it or not. The fact is: at the top of the mast the wind is higher in speed and more aft than at the cockpit level.
Figure A and B show the boat speed, true wind and apparent wind vectors for cockpit level and top of the mast. Obviously in both cases, the boat speed vector must be the same. The true wind vector is obviously the same direction but due to wind shear it is longer (faster) at the top of the mast. This results then in the apparent wind direction being more aft. IE in this case from 135 deg to 125 deg.
Wind shear and apparent wind phenomenom
Thirdly, you should understand that if a sail is sheeted in to tight it creates more heel. This then is exactly what is happening at the top of the mast. Even though at the bottom of the sail you may have perfectly trimmed the sail, the top of the sail is sheeted in too tight against higher wind speed. No wonder you’re getting excessive heeling. And excessive heeling creates round ups.
This is now quite a revelation! It means that the top of the main needs to be “out” further than the bottom of the sail for it to operate efficiently. This is usually indicated by the top telltale. Often the leeward telltale will be stalling at the top of the sail. Especially in high wind because of the phenomena above.
The top of the mainsail needs to go further out so that the starboard telltale can fly smoothly
Thus the top of the mainsail needs to be let out further so that the leeward telltale can fly smoothly. This is commonly referred to as twisting the sail out at the top. Except people believe you are just spilling out (wasting) the wind at the top. Not quite so now, as you’ve just learned. Twisting out the top of the sail is letting the top of the sail fly according to the direction of wind it is feeling.
In the illustration, you can see the top telltale on the downwind side is fluttering. If you let out the main at the top, the wind can reattach to the sail on the leeward side and the telltale will fly smoothly reducing the force aloft.
Understanding all the above. How do we stop rounding up?
Option one: Obviously the first and safe option in higher winds is to reef the sail.
Option two: Let out the traveler which is what most people do when hit by a gust. Just so long as you realize what you’ve done is not twisted the top of the sail out – all you’ve done is let out the mainsail from top to bottom and thus depower the mainsail. This reduces the force aloft and thus the heel. It also moves the center of effort of wind on the sails forward which reduces tendency to round up. The trouble is that you spend all day fighting gusts with still quite a few involuntary round-ups.
Option three: Let out on the mainsheet. Here again you’ve depowered the entire mainsail to handle the gust. Still, it works.
Option four: Permanently reduce the force aloft by letting out further on the mainsail and tightening up on the traveler. The trick here is to bring the mainsail bottom back in again using the traveler. Yes, bring the traveler to windward up past the center point. Most sailors are reluctant to do this because they’ve been taught that it detaches the wind on the leeward side. But not when you’ve let out the mainsheet. In effect, by letting out on the mainsheet, you’ve allowed the boom to rise up and the leech of the sail to slacken. This creates the desired twist at the top and allows the top of the sail to fly according to its apparent direction. At the same time, the bottom of the sail can fly according to its apparent direction.
By trimming the traveler and mainsheet together you can manage the twist at the top of the sail as desired yet still keep power on the bottom of the mainsail. Keeping power on the bottom of the mainsail keeps your speed up which also increases the effectiveness of the rudder. Increasing the effectiveness of the rudder means it can hold more against any turning effect created by the shifting of center of pressure backwards. Wow – see how it is all connected.
What happened on our 15 knot gusty sailing day? Well, not one round up.
So to summarize, the sailing lesson here is when in higher winds bring the traveler up and sheet out the main. You’ll also need to release the boom vang a little. Letting the boom vang out allows the boom to rise which loosens the leech (trailing edge) of the sail and allows the top part to “twist out”.
This and many other finer sail trim concepts are discussed in NauticEd’s Sail Trim Clinic at http://www.nauticed.org/courses/view/sail-trim.
Posted by Grant Headifen on May 15, 2010 under About NauticEd, Bareboat Charter, Celestial Navigation, Coastal Navigation, Crew, Maneuvering Under Power, Rules of Right of Way, Sail Trim, Skipper, Storm Tactics, weather |
This is day 4 of 6 in your introduction to NauticEd
Today we’re discussing the list of courses and clinics that NauticEd offers for your education.
One of the first course we believe that all sailors should complete no mater what their experience level is the FREE NauticEd Rules of Right of Way Clinic.
If you’re an experienced sailor you’ll see the value in a quick refresher course.
If you’re new to sailing then you’ll learn some vital nautical rules.
In either case – this course is free and thus you’ll be able to see how taking a NauticEd clinic and the associated test will work. This is a graphical and fun 20 minute course.
Take the Rules of Right of Way Clinic now!
For your convenience, we’ve created a chart of recommended courses depending on your skill level.
Go to http://www.nauticed.org/recommended_sailing_lessons
Ranks and courses
In email #2 we discussed the ranks Skipper, Bareboat Charter Master and Captain
Gaining the Skipper Rank
The first lessons to begin your sailing certification is the Skipper course and the Maneuvering Under Power clinic.;
The SKIPPER SAILING COURSE is a beginner to intermediate sailing course. It is a prerequisite to any certification and covers the fundamentals that every one must know. The total time needed to complete this course will be about 20 hours. Cost $67.00
The MANEUVERING UNDER POWER CLINIC: This is our most popular course. An absolutely essential maneuvering and docking course that will save you thousands in dents, bumps and scratches at the marina. Want to dock your boat like a pro every time? Want to impress? Take the most popular NauticEd Sailing School Course now. Estimated time: 3 hours total. Cost: $39.
Gaining the Bareboat Charter Master Rank
BAREBOAT CHARTER CLINIC: Taking a sailing vacation? All hands on deck – this is the yacht charter sailing course for you and ALL of your crew. Make your charter sailing trip more enjoyable by getting ALL the bareboat charter tips you’ll need. Estimated time: 5 hours total. Cost: $39.
COASTAL NAVIGATION CLINIC: Learn to navigate your sailboat. If you plan on sailing away from your home base or are taking a sailing vacation, you need this course. NauticEd Sailing School makes navigating a sailboat – a breeze. Estimated time: 10 hours total. Cost: $39.
Gaining the Captain’s Rank
WEATHER CLINIC: If you’re a real sailor then you need to understand and read the weather. It’s as simple as that! Written by the professionals at Clear Point Weather, this is the best weather sailing course available. Estimated time: 7 hours total. Cost: $39.
SAIL TRIM CLINIC: Learn the true art and finesse of trimming the sails. When to adjust the fairleads, the traveler, the downhaul, the outhaul, the Cunningham, the boom vang. When leaning to sail properly, you should know what all these fine adjustments do. Estimated time: 4 hours total. Cost: $39.
STORM TACTICS CLINIC: Even when day sailing, a storm can be upon us in minutes. Are you prepared with the knowledge now? This storm tactics sailing course will teach the essentials to keep you and your crew alive. Estimated time: 4 hours total. Cost: $39.
SAFETY AT SEA CLINIC: This course is still under construction by Captain Ed Mapes. Captain Mapes has logged tens of thousands of miles on the sailboats around the world. He knows how to be safe and is passing on his hard learned information to you. Coming soon.
In addition to the above courses and clinics, we offer the following:
CATAMARAN SAILING CONFIDENCE CLINIC: Converting over to a catamaran or chartering a catamaran for the first/second time? Learn the essential differences between sailing a monohull and a catamaran. This clinic will give you the confidence. It includes an interactive experiential online game to practice maneuvering in a marina. Estimated time: 3 hours total. Cost: $39.
INTRODUCTORY CELESTIAL NAVIGATION CLINIC: If you’re in any way intrigued with Celestial Navigation, this is the best and simplest celestial sailing course available. You’ll be able to do an actual noon shot and determine your position. Estimated time: 5 hours total. Cost: $39.
QUALIFIED CREW MEMBER COURSE: Learn to sail and contribute as a crew member on a modern cruising sailboat. Learn the lines, sailing terminology, sail trim and rules of the road. Estimated time: 7 hours total. Cost: $37.50.
Tomorrow we’ll discuss practical sailing schools and how you can get a verified proficiency stamp added to your sailing certificate.
Until then – fair winds,
Grant Headifen
Educational Director
NauticEd
Posted by Grant Headifen on May 14, 2010 under About NauticEd, Bareboat Charter, Crew, Skipper |
We received a lot of interest in the Bareboat Charter Clinic Crew Briefing Check list that we sent out via our mailer earlier in the week. Some additional and excellent tips were sent in by some of you and so we have updated the list. See it now at the bottom of this page:
http://www.nauticed.org/courses/view/bareboat-charter
Yum yum while sailing
Bareboat chartering is one of the most fun things you can do on this planet. This August we’re leading a fully booked flotilla in Tonga to sail the islands around Vava’u. But next week we thought we’d pop over there to do a reconnaissance trip. So watch out for our video blog report in a few weeks on that.
Each year we invite our Bareboat Charter Master Graduates to join us on a flotilla. While this year is Tonga, next year we’re thinking of some where in the Med. Come join us on that – watch out for the announcement.
One of the things that we find particularly great about our trips is a fully engaged and working crew. With this comes knowledge about leadership and team work, boat systems, dinghy operations, provisioning requirements and just basic bareboating skills by everyone on board. It’s not that everyone should know how to sail but some good knowledge of what to expect before hand makes the trip go smooth with out drama, confusion, injury, or arguments. Everyone invests A LOT of money in a trip like this.
What we’re suggesting is why not make it as fun as possible. So if you haven’t taken the NauticEd Bareboat Charter clinic yet and haven’t sent it onto your crew, go ahead and do so because the small comparative investment in the clinic by everyone will make the trip seem ten times more fun (and safe). The one tip like walking under the boom side of the boat when going down wind is tooooooo invaluable for your crew.
Bareboat Yacht Charter Clinic
In addition to this, if you’re traveling to Greece, Spain or Croatia, you’ll be required to show harbor authorities a VHF endorsement on your Sailing Certificate. When you take and pass the NauticEd Bareboat Charter Clinic, you’ll get that endorsement stamped on your Sailing Certificate.
So go ahead, get started now with the Bareboat Charter Clinic and let NauticEd teach your crew prior to the trip. Register now at
http://www.nauticed.org/courses/view/bareboat-charter
And while you’re at it, please hit the Like Button on that page to tell your facebook friends that you like this clinic.
Here again is the Bareboat Charter Curriculum
Module 1: Planning and Arriving
1.1 The Types of Charters
1.2 Good Captainship
1.3 Arrival at the Base
1.4 Provisioning
1.5 Freezer and Fridge Management
1.6 Generators
1.7 Fishing
1.8 Kids
1.9 Local Area Familiarization
1.10 VHF Operations
Module 2: Checking out the Boat
2.1 Getting Familiar with the Boat
2.2 The Deck
2.3 Breakdowns
2.4 The Engine
2.5 The Fuel System
2.6 Starting the Engine
2.7 Operating the Engine
2.8 Stopping the Engine
2.9 Plumbing and Tankage
2.10 Seacocks
2.11 Showers
2.12 Heads
2.13 Bilge Pumps
2.14 Galley Stove
2.15 DC Electrical System
2.16 AC Electrical System
2.17 Sails
Module 3: Underway
3.1 Knot Tying School
3.2 Communications
3.3 The Nautical Chart
3.4 GPS
3.5 The Autopilot
3.6 Mooring
3.7 Anchoring
3.8 The Windlass
3.9 Docking
3.10 Seasickness
3.11 The Dinghy
3.12 Briefing the Crew
3.13 Conclusion
Register now at
http://www.nauticed.org/courses/view/bareboat-charter
