May, 2016 Dispatch: On Tides and Med Mooring

 

 

Tides:  What you must know and more than you want to know.

 

What you must know:

 

Recently on a combined Combo(103/104) and 106 (Offshore cruising) course we had the occasion to experience the bad and the good of tides.

 

The major novel requirement of the ASA 106 is that you must do a night-time entrance into Galveston Entrance.  This of course meant that we would have to go far enough offshore and stay out long enough to arrive at the Channel entrance after sundown.  It just so happened that this coincided with a 3 knot ebb tide!  Now, obviously, a sailboat which is capable of at most 6 kts isn’t going to make much “speed over the ground” going against a 3 kt. Ebb tide.  As expected, it took over 5 hours to cover the distance which would normally take an hour and a half.  This is when one’s patience is worn very thin, especially in the Galveston entrance because of the extreme challenge of picking out the channel markers against the constellation of background lights from the city and the ships in the anchorage.  We had plotted our course beforehand, as recommended, so that we knew what should be the course from one marker to the next, but even then it was a challenge which required the attention and participation of every crew-member.

 

Now, it should be remembered that the major causes for making a mistake while sailing are:  1. Sleep deprivation, 2. Pain and 3. Hypothermia.  We did not have the risk of the last two, but there was certainly a risk of the first, so, about 11 pm, I sent two of the crew-members down below to take a nap while the helmsman and I continued to pursue the channel markers which appeared to be receding even as we could see the water slide under our hull.  Our speed over the ground was a whopping 2 kts!  One must not lose patience and give up unless you are going backwards!

 

Finally, we got into the slip after 1 a.m.  Everyone felt that they had accomplished something.

 

What you must know about tides:

 

The depth at low tide (designated “mllw” = mean lower low water on the chart)

The draft of your vessel

Time of high tide

Time of low tide

The site where this information applies is relevant.  For example, when you listen to NOAA (or VHF 1) or look in the newspaper you will get a particular time for, say, “high tide is 8 a.m.”  That particular time applies to GALVESTON ENTRANCE.  You must extrapolate the difference in distance (26 miles up the HSC) to determine the high/low tide at Clear Lake Channel.  You can find this extrapolation in a book (Coastal Pilot) you can purchase from the Coast Guard or download it, or you can find it in the little books which can be purchased at bait shops or West Marine. 

 

For Galveston Entrance to Clear Lake Channel it is.....drum roll....6 hours!  So, if high tide is 8 a.m. at Galveston Entrance it would be 2 p.m. at Clear Lake Entrance.  This comes as a surprise to most people.  But considering this difference gives some clue to what a tide actually is.

 

 

How We Know

Isaac Newton and the mechanical world view.

 

Everyone knows the story about Isaac Newton and the apple falling off a tree.  Apparently, the story is true, and it is even more fascinating than you might imagine.  In 1665, Isaac Newton was a student at Cambridge University.  Because of the plague, the University was closed, so Newton took himself to his aunt’s farm for two years.  Since he went without his books he had a lot of time to think.  During 1665 and 1666 he discovered the law of universal gravitation, the laws of optics and invented the calculus.  But he did not publish any of it.  Twelve years later, back in London, Edmund Halley (of the comet fame) and Christopher Wren (the architect of Westminster Cathedral were in a coffee shop discussing the tides and the path of the moon around the earth.  Halley bet Wren that the brilliant mathematician out at Cambridge would know the answers to their questions,  so he went and asked Newton.  Sure enough, Newton knew the answers to Halley’s questions, but he had never published it and couldn’t find his notes.  (If Newton were alive today he would be on meds! - and I don’t necessarily mean that as a criticism of Newton)  So he had to start all over again.  This time, because of the threat of competitors (Wilhelm Leibniz, a German living in Paris, in particular) to be certain that he got the credit he thought he deserved, he created his entire mechanical world view of the attraction between two bodies (we know them as “Newton’s First Law, Newton’s Second Law, Newton’s Third Law), which he published in his Principia Mathematica...This book was the basis for all of physics until Einstein’s General Theory of Relativity in 1915.  The work is considered by most historians to be the greatest scientific treatise ever produced by man.  As Alexander Pope wrote:

 

“Nature and nature’s laws were night.  God said, ‘Let Newton be,’ and all was light.”

 

So, turning to some oceanographic facts to explain tides:

 

The Oceanography of Tides

What we know as high and low tide is that it is actually a single wave that sweeps around the Earth as it spins.  Actually, rather than thinking of the tides as being a wave it is more accurate to think that the water on the surface of the earth is attracted to the Moon as it passes over and the Earth spins UNDERNEATH the water.  Think of spinning a bucket of water - the bucket spins under the water which builds up on the sides.  This creates the phenomenon of two daily tides:

 

Again to be even more accurate, the tides are caused by the complicated combined effects of the attractions of the Earth, the Moon and the Sun as a body.  When the Earth is closest to the Moon the water on that side of the Earth bulges towards the Moon.  There is a simultaneous bulge of water on the opposite side of the Earth.  I have read of two different theories for this phenomenon, which produces two (diurnal) tides a day.  One explanation is that the far-side bulge is caused by the centrifugal force of the spinning ocean.  Another explanation seems to me to be more plausible:  The ocean on the side of the Moon is closer to the Moon than the Earth, so it bulges towards it.  The Earth’s center of gravity is more massive and closer to the Moon than the ocean on the far side of the Earth, so it is pulled away from the water on that side, producing the bulge. 

What this variability in the explanation of the tides indicates an interesting fact:  The force of gravity is still largely a mystery to physics, and currently there are competing theories.

 

Why the tide is so much later at Clear Lake Entrance:  Add to this already complicated picture, interference of continents, inlets, bays, the spin and tilt of the Earth and you get some sense of the difficulty of predicting the tide times.  The tidal wave that comes into the Clear Lake Entrance is coming from the Atlantic, across the Gulf of Mexico, up through the Galveston Bay Entrance, then it has to slosh around the coastline of the Bay until it sweeps into Kemah. 

 

I mentioned in an earlier dispatch of the extreme tidal range at that time in Galveston Bay, making it such that I was unable to get my boat out - that was a “spring” tide, when the Earth, Moon and Sun are lined up, which together with a north wind sucked the water out of the Bay.

 

So, what is the wavelength of the ocean tide?  20,000 kilometers!

 

As I stated, Newton’s theory of the tides is based on the theory of universal gravity which was ridiculed by Einstein as (“action at a distance”).  This theory holds that two bodies are attracted to each other in a manner which is directly proportional to their mass and indirectly proportion to the square of the distance between them.  Newton never presented a hypothesis to explain gravitational attraction.  He said, “I offer no hypotheses.”  (He actually wrote it in Latin, but Ill spare you).  Even today, physics does not have an explanation for universal gravitation and the theory is not part of what is called the Standard Model of Particle Physics (which includes three forces - the Electromagnetic Force, the Weak Force (together, the “Electroweak Force), and the Strong Force).  Today physicists are attempting to subsume the Standard Model of particle physics and the theory of gravity under what is called “String Theory.”  I am told that it would take about 6 years of constant study to master the mathematics to become a String Theorist.  This is about how long it would take to make two leisurely circumnavigations of the Earth.  So, I had better get started on it.  (The circumnavigation, I mean)

 

 

Back to Houston Ship Channel

 

After, a rest of several hours we then proceeded up Houston Ship Channel towards Kemah.  As expected, we now rode a flood tide, so our speed over ground was 8 kt!  those(The Lord taketh away, and (for those who are patient) the Lord giveth.

 

So, on the entrance, we were trying to climb up a wave,

While,

On the passage from Galveston to Kemah up the HSC, we were riding down a wave.  You know, it is said, “location, location, location.”  Well, I must add: time, time time.

 

A lot more is known about gravity than in Newton’s day.  It is known, for example, that gravitation is responsible for the rings of Saturn and for the volcanic eruptions on a moon (Io) of Jupiter!

Think about it:  While we were interacting with the ocean’s wave we were interacting with the same force that affects Saturn and Jupiter!  I don’t know if I should feel humbled or defiant (like Lieutenant Dan in Forest Gump - “Is this all you got!?”)

 

 

I suppose that this is the meaning of the sentence:

 

“May the Force Be With you.”

 

 

References:

1. Cartwright, David Edgar. Tides: A Scientific History.  Cambridge: CUP, 2000.

2. Pugh, David. Changing Sea Levels:  Effects of Tides, Weather and Climate.  New York:  CUP, 2004.

3. Burton David M. History of Mathematics: An Introduction. Dubuque. IA: Wm. C. Brown.

 

 

 

Anchoring and Med Mooring

 

In our Combo course (103/104) we don’t typically teach Mediterranean Mooring.  I have discussed it previously and commented that it is used all over the Med (and elsewhere) because it allows a marina to stack in more boats.  I realize that that statement is a bit biased, so here is another explanation: It encourages you to get to know your neighbor better.

The important physical difference is that there is no walkway or dock between the boats.  So, many many fenders are required. 

The other features of Med mooring which are different is that you lay an anchor out in the water, or pick up a line (“lazy line”) and attach it to your bow, then back onto the dock. 

 

So, learning how your boat backs is critical.

 

I recently came up with a method of teaching Med mooring by incorporating it with teaching standard anchoring:

 

Consider the procedures consist of three stages:

 

1. Prepare the anchor and lines.

2. Drop the anchor.

3. Secure the anchor.

 

 

Stage 1:  So, with regular anchoring:  The lookout and anchor -crew stands up on the bow and directs the helmsman to a good anchoring site, based on the look of the water (in the Bahamas, for example, through the coral). 

The boat is motoring INTO the wind. 

This is Stage 1.  The anchor and rode are prepared so that they can be dropped when required.  This stage should be practiced even before the procedure is begun, and can even be practiced while in the slip.

The anchor rode is taken from the anchor locker and “faked” so that it will play out smoothly when the anchor is deployed.  The anchor may be hung over the bow and held firmly in place.

 

Stage 2: The bow-crew directs the helmsman with appropriate pre-agreed hand signals to stop (usually a closed fist).  The boat is allowed to stop and begin to drift backwards with the wind.  Then the anchor is dropped.

The boats is allowed to drift backwards until about 1/2 of the previously calculated amount of rode plays out, then:

 

Stage 3:  The anchor is secured.  Then the helmsman is directed by appropriate hand gestures to motor back at about 1500 rpm to set the anchor.  If the anchor is set then the remainder of the rode is played out.  It not, then there should be consideration of another site with perhaps better holding ground.

 

Now, of course, you set an anchor watch.

 

 

Med Mooring

 

 

Now, if you have learned this procedure with standard anchoring off the bow, then Med mooring is straight-forward:

 

Stage 1:  Before entering the slip one should approach the slot in forward and look for a “lazy line,”  a line which is attached to a cleat on the dock.  If one is spied, you will not need to drop a bow anchor but will pick it up instead.

 

Prepare the anchor and the lines.  The anchor is prepared as in standard anchoring.  Additionally, the lines which will be thrown onto the dock are prepared and attached to the stern cleats.

If there is a lazy line, the anchor does not have to be prepared.

 

Multiple fenders are hung from the sides.

 

Then the helmsman proceeds to slowly back towards the selected spot between two boats. 

 

Stage 2:  This is the same as in standard anchoring, except that the helmsman indicates when to drop the anchor (usually when the boat is about 3 boat-lengths from the dock). 

 

He indicates this by merely holding up two fingers.

 

The bow-crew drops the anchor and the helmsman continues backing toward the dock.

 

Again:  if there is a lazy line, the anchor is not dropped.

 

Stage 3:  Then, when the boat just begins to enter the space between the two boats the helmsman holds up three fingers, indicating that the bow-crew should secure the anchor.  The helmsman continues backing into the space.  (The anchor should now be secure and becoming taut). 

 

When the boat approaches the dock, the helmsman (or a crewman) throws the lines which have been secured to the stern cleats to someone on the dock where they are secured, or, if there is no one on the dock, the helmsman approaches the dock close enough for a crewmember to jump in the dock (using the usual precautions to not jump until the boat is virtually touching the dock

 

If there is a lazy line, it is now picked up and walked to the bow, fed through a bow pad eye then secured to a cleat.

 

  The boat should now be anchored at the bow or secured by a lazy line and secured to the dock at the stern.

 

There are several good Youtube videos of Med mooring.  The one I like the best is titled:  Stern-to mooring techniques Greece

 

 

 

If your boat does not back down with a degree of control, or if there is a really strong cross wind, a different approach can be tried.  Head the boat into the wind and at the proper drop point let go the anchor and allow the boat to settle back, gently snubbing the rode to set the anchor.  Let out slightly less rode than the distance from the anchor to the bows of the other boats.  Take a line ashore in the dinghy and manually sweat the the stern into position at the entrance to the slot, from where it can be further worked into the slot.

 

Some precautions:  Position your boat fore and aft so that your spreaders do not tangle with those of your neighbors.

 

I haven’t mentioned why it is better to back in rather than motor in forward -- it is easier to get off the boat at the transom than clamber the bow.  Duh!

 

 

mWC

 

 

April, 2016 Dispatch:  On the BVI, the Caribbean Sea, water pump belts and fuel filters

 

On the BVI

            I recently spent some time cruising in the BVI.  It has been over 10 years since I was last there and there were some changes.  The BVI is still the most popular spot to charter a boat and the number of vessels in the water has grown considerably, but it is still a great place to cruise – particularly for a first-time charterer.  The Moorings and Sunsail bases are on the south side of Tortola, in Roadtown, which is sheltered.  One does not have to worry about leaving and returning to the marina because a pilot will take you out and, on return, will come out and board you and take you in to base.   The majority of vessels in the waters now are catamarans.  One doesn’t have to worry about not having catamaran certification because the managers will check you out and instruct you on the boat before you leave.

             Most of the good anchorages where the snorkeling is the best  now have mooring balls which can be picked up for the duration of the dive.  Most do not allow overnight mooring or anchoring, so you will need to leave your anchorage early in the morning to get a good mooring for the duration of your snorkeling.

 

In the Caribbean Sea

        On this same trip we sailed south of the BVI out into the Caribbean Sea to the east of the Leeward Islands.  This is a good area to get some ocean sailing experience with the swells one would expect to encounter in deeper waters.

            We sailed east of Saba island.  One must be careful to keep considerable sea room from Saba island because the “Saba Bank” extends out several miles and has depths as shallow as 6 ft. in spots.

            Keeping a careful DR is important because there is also a small island (Aves) right out in the middle of nowhere.

 

Of water pump belts

            Recently while sailing my boat in Galveston Bay I had an experience which teaches some principles to be known regarding the (over) heating of the engine.  When I first started my engine there was a screaming sound coming from my water-pump belt.  I had heard this before and had checked and found that the belt was tight enough, so I just dripped on some lubricating oil or WD 40 on the belt and the squealing stopped.  This time, however, when the sound started, I could not go down and drip on oil.  Soon the squealing stopped.  Then my overheating alarm came on.  When this occurs, the first thing to do is check to see if water is coming out of the exhaust which would indicate that the sea-water cooling system is working.  I checked and it was coming out.

I stopped my engine – this is obviously important, because if you don’t you will permanently damage the engine.

Now, remember that a marine diesel engine has two cooling systems – the sea-water system: consisting of an inlet hose (with stopcock), a water filter, and a pump (with impeller).  Malfunction of any one of these would result in water not coming out of the exhaust.

As I said, this was not the problem in my case.

So, now, I turned to consider the fresh water system:

            This system is internally circulated (and cooled by the sea-water through a heat exchanger)

            It does not start circulating until the water temperature rises to 42 degrees (in the case of my 30 hp Yanmar).

            For it to begin circulating a thermostat must open.

So, I assumed that the problem was that the thermostat was malfunctioning.  Now, one can remove the thermostat (after the engine has cooled – be careful!) and the water will circulate.  This could be a temporary fix.

The fact that this overheating alarm occurred about 15 minutes after starting the engine made me suspicious that the problem was the thermostat.

Of course, the problem could have been caused by there being too little water (or antifreeze) in the internal system, so, after letting the engine cool, I checked the water level and it was okay.

So, I set about to remove the thermostat – then I noticed – the water pump belt was missing!  It had broken and fallen down in the pan under the engine.  So this was the obvious problem.  Luckily I had a spare on board and, after installing the new one, the engine ran coolly into the marina.

Now, the question should arise:  How come there was sea-water coming from the sea-water system if the water pump belt was broken?

            There are two possible answers:

                                    1. The two systems run on separate belts.  This is true for some engines.

                                    2. The sea-water system runs without requiring a belt drive.  And this, surprisingly, turned out to be the answer in the case of my Yanmar 30.  I had to go to the engine booklet to see how it works.  The explanation is vague – but it clearly is separate from the fresh water system.

            The moral of this tale:

1. If your engine is heating but your sea-water is circulating, look at your fresh water system.

                        2. Do the diagnostics before you set about doing the treatment.

 

On fuel filters

            On a recent course we had an experience which taught a lot of lessons.  When we left Kemah, the wind and waves were very heavy and tossed us around dramatically as we motored across the Bay towards the Boater’s Cut at HSC marker.  After turning into the HSC the wind and waves tossed us around even more and the engine throttled down significantly.  After passing through the narrow part of the channe at Red Fish Island, l we deployed  the jib, to be ready should the engine fail completely.  Sure enough, this is what happened at about marker ‘45’.  One should be able to speculate what was the problem with the engine.

Answer:  The engine was acting as if it was “fuel starved,” meaning that the jostling waves had kicked up the grundge which grows in the bottom of diesel.  I am told that there is actually a bacteria which will grow in diesel!.  It was obvious at this time that we should have tended to the engine before turning into the HSC, but now we were committed.  The wind direction would not allow us to turn back.  I elected to not deploy the main sail because of the  risk of considerable leeway movement towards the spoil banks.  So the students had to quickly learn how to handle a sail boat with extreme lee helm (just the jib was out) while another crewman and I went below to attend to the engine.  Luckily, the student who went down with me was a mechanic by trade, so he was able to quickly identify and change the fuel filter.  Equally luckily, the other students, despite having virtually no experience sailing a large vessel, quickly picked up the skill and cooperatively taught each other how to handle the bucking vessel.   Leadership and teamwork solved the day.

Just as expected, the fuel filter was completely blocked with green slimy grundge.  We had an extra filter and once it was installed and the fuel line bled of air (by opening a bleed hole and touching the starter a few times) the engine kicked right in and we were able to motor on to Galveston.  If the engine had not participated in the adventure we would have had to hoist the main and tack across the HSC (at an appropriate open spot) and anchor in East Bay, south of Bolivar peninsula,  to ultimately be towed home.

I learned from the mechanic that some modern engines have an electric fuel pump so you don’t have to hit the starter to get the fuel to start through the system.  You can tell this if you hear a “clicking” when you turn on the ignition.  For us, the wind was so loud we could not hear anything, so we hit the starter.

The major lesson repeated:  attend to a malfunctioning system before you have to have it.  Hoping that it will work when you need it is a natural human trait, but one not designed to achieve success unless you want to use up all your luck for a long time.  And you may need that luck for some time when mother nature is not so kind and forgiving.

 

mWC

January, 2016 Dispatch

Emergency Calls

                There is some confusion on which emergency calls should be used in certain situations.  The three calls are:

                ‘Mayday Mayday Mayday

                ‘Pan Pan Pan’

                ‘Securite Securite Securite  (pronounced “See-cur-a-tay”)

 

                Mayday

                                There is not much confusion about this call.  It is to be used if there is imminent loss of life or the vessel- man overboard, sinking vessel, in danger of going on the rocks, etc.

                But, with the other two there is some confusion.  Some books write that they have different priorities, but this is not entirely correct.  They actually mean different things to the ones receiving the call.

                ‘Securite – means ‘I am a hazard to navigation,’ so the receiver should be aware of the situation because the one sending the call may be a hazard to him.

                ‘Pan…’ means ‘I need attention, or help…” It does not mean that the receiver has to necessarily look out to be certain that he doesn’t run into the sender.

                Consider these three scenarios and decide what  is the appropriate call:

                A. You lose power while motoring past Kemah Boardwalk, so you drop anchor.

B. You lose power and start taking on water while motoring out Bolivar Roads, and are not able to get out of the channel.

C. You lose power while motoring out Bolivar Roads, but manage to drop an anchor out of the channel.

___________________________________________________

Scenario A:  The appropriate call would be ‘Securite…’ – you are a hazard to navigation.

Scenario B: The appropriate call here would be ‘Mayday…’ You are in danger of sinking the boat (lets suppose that it is a sailboat with a 50’ mast) in one of the busiest channels in the world.  You are more than just a hazard to navigation.

Scenario C: The appropriate call would be ‘Pan….’ You are not a hazard to navigation. 

But if for example, the wind picks up and you drift into the channel, then it would become a ‘Securite…’  Or if the winds appeared to be driving you into the rocks, then it would become a ‘Mayday…’

This last example shows that these calls should be considered to be dynamic – subject to change if the circumstances change.

 

Taking a Different Tack

One student (whose first language was not English) once asked me, in reference to some nautical term, “What is the logic?”  The answer is: There is no “logic.”  Nautical terms come from multiple languages – Dutch, French,  German – much like English itself.  They were picked up and became common merely by usage.  After the Battle of Trafalgar (when the little island off the coast of Europe became an “empire,” then the term used by the British became the language of sailing.

One term which often leads some confusion is the term ‘tack.’   It is used in three different senses:

To be on a “starboard tack”

To “carry out a tack” (from, say, starboard to port)

The front lower corner of the mainsail.

 

However, is you look at the evolution of rigging you will realize that they come from the same sailing maneuver.  Before the development of an fore-and-aft sail (Gaff, Marconi), the ‘tack’ of the main sail was rigged forward of the mast.  If you were on a starboard tack, then it was on the starboard side of the mast.  If you decided to tack the boat you had to physically move the tack to the port side of the boat.  So, to go from one tack to another you move the tack of the sail from one side of the mast to the other.

 

Hope all are having a good New Year.

mWC