One of the types of problems you may have on a Coast Guard exam for deck licenses is the estimated time of arrival (ETA) problem. These problems can be solved with a knowledge of the basic time, speed, and distance formula from piloting. The following information is given in these types of problems:
1. The name and or latitude and longitude of the place departing from. (When coordinates are not given the zone description is provided.)
2. The name and or latitude and longitude of the place the ship is going to. (When coordinates are not given the zone description is provided.)
3. The distance between the two points.
4. The ships speed of advance.
5. The length of any delays enroute such as bunkering.
With this information, the estimated time of arrival at the second port can be calculated by local zone time and date. The example problem will give you a idea on how to solve these problems.
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Thursday, March 12, 2009
Chronometer Error (Time Ticks)
Chronometers are set to Greenwich mean time when they are installed and again after each cleaning. They are not reset by the navigator between these times, but as time passes chronometers will acquire error. Determination of the amount of error and the trend of the error is an important duty of a navigator. Knowledge of the error is important so that exact Greenwich mean time is available for use in solving navigational sights.
Chronometer error is determined by comparing the chronometer to a radio time signal broadcast. In most cases this procedure involves tuning in the time signal, listening for the exact GMT, and then using a stop watch or comparing watch to measure the interval between hearing the time signal and the reading of the chronometer. This procedure is termed obtaining a time tick. There maybe some confusion because time signals are in a 24 hour clock format while the chronometer is normally a twelve hour clock, but chronometer error will be relatively small even years after the chronometer is set.
Example: When the chronometer face reads 07h-58m-02s at the 2000 GMT time signal, you should understand that this means the chronometer time is actua!ly 19h-58m-02s. Chronometer error can be either fast or slow. It is also important for the navigator to have a good estimate of the average amount the chronometer error changes each day. This is called the chronometer rate. The rate is determined by obtaining the difference between the error on the first day and last day of a given period, and then dividing by the number of days in the period. The result will be the chronometer rate. The rate is termed "losing" if a slow chronometer error is increasing or a fast error is decreasing. It is "gaining" if a fast error is increasing or a slow error is decreasing. With knowledge of the rate, the navigator can determine the estimated chronometer error on a day when he cannot get a radio time tick.
The following Coast Guard exam problems demonstrate solution of typical "time tick" problems.
"CLICK HERE TO VIEW"
Chronometer error is determined by comparing the chronometer to a radio time signal broadcast. In most cases this procedure involves tuning in the time signal, listening for the exact GMT, and then using a stop watch or comparing watch to measure the interval between hearing the time signal and the reading of the chronometer. This procedure is termed obtaining a time tick. There maybe some confusion because time signals are in a 24 hour clock format while the chronometer is normally a twelve hour clock, but chronometer error will be relatively small even years after the chronometer is set.
Example: When the chronometer face reads 07h-58m-02s at the 2000 GMT time signal, you should understand that this means the chronometer time is actua!ly 19h-58m-02s. Chronometer error can be either fast or slow. It is also important for the navigator to have a good estimate of the average amount the chronometer error changes each day. This is called the chronometer rate. The rate is determined by obtaining the difference between the error on the first day and last day of a given period, and then dividing by the number of days in the period. The result will be the chronometer rate. The rate is termed "losing" if a slow chronometer error is increasing or a fast error is decreasing. It is "gaining" if a fast error is increasing or a slow error is decreasing. With knowledge of the rate, the navigator can determine the estimated chronometer error on a day when he cannot get a radio time tick.
The following Coast Guard exam problems demonstrate solution of typical "time tick" problems.
"CLICK HERE TO VIEW"
Wednesday, March 11, 2009
A Sailors Knife or a Pointless Story
Thought I'd give you a break from Celestial Navigation and Terrestrial Navigation and pass this interesting bit of information on the "Sailors Knife".
The lore involves the points on sailor's knives, or rather the lack there of. Sailor's rope knives traditionally have no points. As far as I can discover, there is no functional reason for this. After all, a knife with a point will cut line just as well as a knife without a point. The story I have seen and heard holds that, on most ships, sailor's were not allowed to carry pointed knives, to discourage them from stabbing each other when the strains of a long voyage under sail got to be too much for some of them to bear.
A friend of mine found this book "The Making of a Sailor", or Sea Life Aboard a Yankee Square-Rigger, by one Frederick Pease Harlow. The book was published in 1928, but recounts the author's experiences at sea as a boy about six decades earlier. On pages 90-93 Harlow describes the outset of a voyage to Melbourne, Australia. The first and second mates are choosing up the port and starboard watches for the voyage from the newly hired crew. The first mate, naturally, chooses first. I choose you, What's your name? Hans, sir, he replied. Let me have your knife, requested the mate, who stood on top of the main hatch, with a hammer in his hand, which he was all the while turning and twisting. Upon receiving the sheath-knife, which is as much a part of sailor's uniform as his overalls and is always carried in a sheath or scabbard, hanging from a strap about the waist and back of the hips, where it is handy for cutting line, for a sailor is not dressed without his knife, the mate put the point of the knife across the iron band on top of the combings of the hatch and struck a sharp blow with the hammer, breaking off the point.
You probably didn't have the mate, in your last ship, break the point off your knife. said Mr. Burris. But I always keep a ship sweet and clean by seeing that every knife aboard the ship has no point. This is for your own protection. If you get into a fight with a shipmate you know you can't stick him with your knife or he, you. Knowing this you both will fight like men and use your fists, the weapons God has given you to fight with. Returning the knife to Hans, he was told to stand over to the port rail. The second mate then chose Jim Dunn. His knife was broken in the same manner and he was told to stand over to the starboard rail. The selection and knife breaking continued until the 14 men and two boys were all divided into two watches.
Going forward, I followed the men into the forecastle. A big Irishman by the name of O'Rourke, was much put out by having his knife point broken and was saying as I entered, I don't know phat ye's fellers tink about it, an I haven't been to sea for ten years, but fifteen years ago I sailed in the (Clipper) ships Live Yankee (built 1853, wrecked 1861) and the Phantom and if ships of that caliber can make a vi age widout breakin our knives, why in the --- does an old tub like this wan want to do it?
The answer to seaman O'Rourke's question very likely lay in a Federal maritime law enacted in 1866, during the ten year interval when he had been ashore. First Mate Burris had in fact not gone nearly as far as the new law required. The Act of Congress of July 27, 1866, which is still the law (Title 46 u.s. Code, Section 710) reads:
Carrying sheath knives. No seaman in the merchant service shall wear any sheath knife on shipboard. It shall be the duty of the master of any vessel registered, enrolled, or licensed under the laws of the United States, and of the person entering into contract for the employment of a seaman upon any such vessel, to inform every person offering to ship himself of the provisions of this section, and to require his compliance there with, under a penalty of $50 for each omission.
Note that the penalty for a violation falls not on the sailor, but on the captain or the owner's agent. As far as I know, U.S. Navy sailors at this time, and up until World War II, were only allowed to carry folding knives, and those had to have square tipped blades.
The lore involves the points on sailor's knives, or rather the lack there of. Sailor's rope knives traditionally have no points. As far as I can discover, there is no functional reason for this. After all, a knife with a point will cut line just as well as a knife without a point. The story I have seen and heard holds that, on most ships, sailor's were not allowed to carry pointed knives, to discourage them from stabbing each other when the strains of a long voyage under sail got to be too much for some of them to bear.
A friend of mine found this book "The Making of a Sailor", or Sea Life Aboard a Yankee Square-Rigger, by one Frederick Pease Harlow. The book was published in 1928, but recounts the author's experiences at sea as a boy about six decades earlier. On pages 90-93 Harlow describes the outset of a voyage to Melbourne, Australia. The first and second mates are choosing up the port and starboard watches for the voyage from the newly hired crew. The first mate, naturally, chooses first. I choose you, What's your name? Hans, sir, he replied. Let me have your knife, requested the mate, who stood on top of the main hatch, with a hammer in his hand, which he was all the while turning and twisting. Upon receiving the sheath-knife, which is as much a part of sailor's uniform as his overalls and is always carried in a sheath or scabbard, hanging from a strap about the waist and back of the hips, where it is handy for cutting line, for a sailor is not dressed without his knife, the mate put the point of the knife across the iron band on top of the combings of the hatch and struck a sharp blow with the hammer, breaking off the point.
You probably didn't have the mate, in your last ship, break the point off your knife. said Mr. Burris. But I always keep a ship sweet and clean by seeing that every knife aboard the ship has no point. This is for your own protection. If you get into a fight with a shipmate you know you can't stick him with your knife or he, you. Knowing this you both will fight like men and use your fists, the weapons God has given you to fight with. Returning the knife to Hans, he was told to stand over to the port rail. The second mate then chose Jim Dunn. His knife was broken in the same manner and he was told to stand over to the starboard rail. The selection and knife breaking continued until the 14 men and two boys were all divided into two watches.
Going forward, I followed the men into the forecastle. A big Irishman by the name of O'Rourke, was much put out by having his knife point broken and was saying as I entered, I don't know phat ye's fellers tink about it, an I haven't been to sea for ten years, but fifteen years ago I sailed in the (Clipper) ships Live Yankee (built 1853, wrecked 1861) and the Phantom and if ships of that caliber can make a vi age widout breakin our knives, why in the --- does an old tub like this wan want to do it?
The answer to seaman O'Rourke's question very likely lay in a Federal maritime law enacted in 1866, during the ten year interval when he had been ashore. First Mate Burris had in fact not gone nearly as far as the new law required. The Act of Congress of July 27, 1866, which is still the law (Title 46 u.s. Code, Section 710) reads:
Carrying sheath knives. No seaman in the merchant service shall wear any sheath knife on shipboard. It shall be the duty of the master of any vessel registered, enrolled, or licensed under the laws of the United States, and of the person entering into contract for the employment of a seaman upon any such vessel, to inform every person offering to ship himself of the provisions of this section, and to require his compliance there with, under a penalty of $50 for each omission.
Note that the penalty for a violation falls not on the sailor, but on the captain or the owner's agent. As far as I know, U.S. Navy sailors at this time, and up until World War II, were only allowed to carry folding knives, and those had to have square tipped blades.
How to Determine your Speed by Wheel
1. Calculate the revolutions per minute (RPM's) with an estimated slip and known pitch.
2. Calculate the "slip".
3. Calculate the speed of advance with estimated slip.
4. Calculate the distance run with an estimated slip and known revolutions per day.
To view the formulas and solutions to these Coast Guard exam questions
"CLICK HERE TO VIEW"
2. Calculate the "slip".
3. Calculate the speed of advance with estimated slip.
4. Calculate the distance run with an estimated slip and known revolutions per day.
To view the formulas and solutions to these Coast Guard exam questions
"CLICK HERE TO VIEW"
Tuesday, March 10, 2009
Reduced Fuel Consumption at Maximum Speed Problems
1. While steaming at 15.0 knots, your vessel consumes 326 barrels of fuel oil per day. In order to reduce consumption to 178 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 8. 1 knots
B. 8.5 knots
C. 11.1 knots
D. 12.2 knots
2. While steaming at 14.5 knots, your vessel consumes 319 barrels of fuel oil per day. In order to reduce consumption to 217 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 9.8 knots
B. 11.9 knots
C. 12.8 knots
D. 13.5 knots
3. While steaming at 16.3 knots, your vessel consumes 363 barrels of fuel oil per day. In order to reduce consumption to 298 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 12.6 knots
B. 13.1 knots
C. 14.7 knots
D. 15.3 knots
4. While steaming at 17.5 knots, your vessel consumes 378 barrels of fuel oil per day. In order to reduce consumption to 194 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 12.5 knots
B. 14.0 knots
C. 15.5 knots
D. 16.8 knots
5. While steaming at 15.7 knots, your vessel consumes 329 barrels of fuel oil per day. In order to reduce consumption to 267 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 12.7 knots
B. 13.5 knots
C. 14.6 knots
D. 15.5 knots
A. 8. 1 knots
B. 8.5 knots
C. 11.1 knots
D. 12.2 knots
2. While steaming at 14.5 knots, your vessel consumes 319 barrels of fuel oil per day. In order to reduce consumption to 217 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 9.8 knots
B. 11.9 knots
C. 12.8 knots
D. 13.5 knots
3. While steaming at 16.3 knots, your vessel consumes 363 barrels of fuel oil per day. In order to reduce consumption to 298 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 12.6 knots
B. 13.1 knots
C. 14.7 knots
D. 15.3 knots
4. While steaming at 17.5 knots, your vessel consumes 378 barrels of fuel oil per day. In order to reduce consumption to 194 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 12.5 knots
B. 14.0 knots
C. 15.5 knots
D. 16.8 knots
5. While steaming at 15.7 knots, your vessel consumes 329 barrels of fuel oil per day. In order to reduce consumption to 267 barrels of fuel oil per day, what is the maximum speed the vessel can turn for?
A. 12.7 knots
B. 13.5 knots
C. 14.6 knots
D. 15.5 knots
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