how to describe ship course speed

What does the length of a ship's course line represent?

Calculating a ship’s course, speed, and position using data from the hydrophone Tutorial by jerm138 www.subsim.com. 00:00 00:10 00:20 00:30 00:40 00:50 Assuming a constant speed and course, a ship will travel an equal distance during two …

How do you find the course of a passing ship?

Each time a fix or running fix is plotted, a vector representing the ordered course and speed originate from it. The direction of this course line represents the ship's course, and the length represents the distance one would expect the ship to travel in a given time. This extrapolation is used as a safety precaution: so, a predicted DR position that will place the ship in water 1 …

Why is a ship’s speed measured in knots?

COURSE OBJECTIVES . CHAPTER 9 . 9. SHIP MANEUVERABILITY . 1. Be qualitatively familiar with the 3 broad requirements for ship maneuverability: a. Controls fixed straightline stability . b. Response . c. Slow speed maneuverability . 2. Qualitatively describe what each requirement is dependant upon. 3. Briefly describe the various common types of rudder. 4.

What are the degrees of a ship called?

ship is in “open water” conditions i.e. without breadth restrictions, this decrease may be up to 15% of the service rpm in deep water. If the ship is in confined channel, this decrease in rpm can be up to 20% of the service rpm. 5. There will be a drop in ship’s speed. If the ship is in open water conditions this decrease may be up to 35%.

How is the speed of a ship measured?

One knot equals one nautical mile per hour, or roughly 1.15 statute mph. The term knot dates from the 17th century, when sailors measured the speed of their ship using a device called a “common log.” The common log was a rope with knots at regular intervals, attached to a piece of wood shaped like a slice of pie.Oct 8, 2021

What is ship's speed?

knot, in navigation, measure of speed at sea, equal to one nautical mile per hour (approximately 1.15 statute miles per hour). Thus, a ship moving at 20 knots is traveling as fast as a land vehicle at about 23 mph (37 km/hr).

What term is used to refer to the speed made by the vessel along its track?

Drift is referred to as the current's speed, which is usually measured in knots. “Leeway” refers to the amount of sidewards translation of a vessel drifting off of or away from the intended course of travel (with no correction or compensation by altering the heading of the vessel such as pointing her into the wind.)

How do you determine the course of a ship?

A ship's true course is determined by the direction from the ship to the geographic north pole (also called true north). Navigation charts andthe compass are labeled with true north, but setting a ship's course is not merely a matter of steering in relation to the north pole.

What is effective speed?

Effective Speed can be defined by total distance travelled divided by the total time devoted to the mode of transport.Nov 25, 2015

What is a good cruising speed for a boat?

Most mechanics and engineers suggest the best cruising speeds are achieved at 3400 and 3800 rpm respectively.Jun 18, 2014

How do you write ship logs?

They are;Date.Names of vessel, MMSI Number & Call Sign.Number of persons on board.Time of each log entry (this may be local time, ship's time or UT - and should be specific clearly)Departure Port / Destination Port & associated HW & LW times and heights.Water Log (the 'milometer')Water Speed (log speed)More items...

Which instrument is used to measure the speed of ship?

loglog, also called maritime log, instrument for measuring the speed of a ship through water.

What is course made good and course over ground?

Course Made Good (CMG) - Is the course actually steered which includes the effect of current set (direction) & drift (speed), wind and leeway and helmsman errrors. Note we distinguish COG (course over ground) from cmg (course made good), as one being present dynamic value, and the other being past.Aug 27, 2021

How do you calculate good speed?

Speed over ground is speed made good, or the vessel's actual speed found by dividing the distance between two fixes by the elapsed time interval between the taking of the two fixes.Aug 31, 2010

What is ship course?

Most sought courses in maritime and shipping are as follows: Diploma Courses: Diploma in Marine Engineering – 3 years. Diploma in Logistics and Shipping – 1 year. Diploma in Naval Architecture And Offshore Engineering – 3 years.

What is a nautical course?

Nautical Science is a three years course that results in an undergraduate degree or diploma after which the student joins a ship as a trainee cadet officer (commonly referred to as a deck cadet).Nov 29, 2021

Why is it important for ships to be maneuverable when traveling at slow speeds?

This is because evolutions such as canal transits and port entrances are performed at slow speeds for safety reasons. Unfortunately, this is when the ship’s rudder is least effective.

What is ship maneuverability?

Ship maneuverability is a very complex and involved subject involving the study of equations of motion involving all six degrees of freedom. Analysis of these motion equations allows for predictions of ship maneuverability to be made. However, many assumptions are made, so model testing is required to verify analytical results. Once built, a ship’s maneuvering characteristics are quantified during its Sea Trials.

How does a rudder work at slow speeds?

To improve the low flow rate experienced by the rudder at slow speeds, the rudder is often positioned directly behind the propeller. In this position, the thrust from the propeller acts directly upon the control surface . A skilled helmsman can then combine the throttle control and rudder angle to vector thrust laterally and create a larger turning moment with minimal advance and transfer.

Why is the rudder limited at slow speeds?

Unfortunately, at slow speeds the rudder is limited in its effectiveness due to the lack of flow across its surfaces. However, there are several modifications that have been developed to improve the situation.

What are the requirements for a naval architect?

These include the obvious dimensions such as LPP, Beam and Draft, but also other requirements such as top speed, endurance, operational mission, etc. Some of the more complicated requirements involve maneuverability. These can be split into three broad categories.

Is it hard to steer a 30ft pleasure boat?

A small 30 ft pleasure craft you own is very difficult to steer. In particular the smallest amount of wind or sea makes it almost impossible to keep on course. While the boat is out of the water for the winter, what modification could you make to the hull to improve its maneuvering characteristics?

What is the most important control surface on a hull?

Clearly, the rudder is the most important control surface on the hull. There are a multiplicity of different types. Figure 9.2 reproduced from the SNAME publication “Principles of Naval Architecture” shows some of them.

What happens when a ship goes through water?

When a ship proceeds through water, it pushes the water ahead. This volume of water returns down the sides and under the bottom of the ship. The streamlines of return flow are speeded up under the ship, causing a drop in the pressure and resulting in the ship dropping vertically in the water.

Why does a ship drift sideways?

However, depending on the strength of the wind, the ship drifts sideways due to leeway and this has to be accounted for while handling the ship.

What happens when the wind blows from the right astern?

When the wind is blowing from the right astern, steering the ship becomes easy; however, in case of head wind, the stern part of the ship has the tendency to pay off on either sides. This is a difficult situation to tackle and getting the ship back on course is no piece of cake.

When the wind is pushing the ship’s stern away to leeward, the stern tends to swing

When the wind is pushing the ship’s stern away to leeward, the stern tends to swing towards the leeward. The ship is therefore steered towards the wind and the ship is required to be given a lee helm.

Why are tugs important?

Tugs are extremely helpful for manoeuvring, but are monetary burden on ship owners as each tug taken for assistance is charged a handsome amount. However, they ensure the most important factor - safety of the ship and the port, which compensates the monetary part.

Can a ship hit the berth?

Ship can hit the berth with her bow before stopping, or the large astern movement used to stop the ship and the resulting transverse thrust can cause the stern to hit the berth.

Why is it important to balance the forward speed of a ship against the astern power needed to stop the same?

This result into greater effect of the transverse thrust, which brings the ship’s bow close to the berth and throw the stern off.

When was the nautical mile established?

In 1929, the international nautical mile was standardized at 6,076 feet; it was adopted by the United States in 1954. A nautical mile is different from a mile on land, which is based on walking distance. The Romans first defined a land mile as 1,000 paces or pairs of steps; it was set at its current measurement of 5,280 feet by Queen Elizabeth I in ...

What is the Dutchman's log?

In this method, knots were tied at uniform intervals in a length of rope and then one end of the rope, with a pie-slice-shape piece of wood (or “chip”) attached to it, was tossed behind the ship.

How does wave energy affect ship speed?

Thus, if wave height doubles, a four-fold increase in energy required to create the wave occurs. Therefore, as ship speed increases and wave height increases, wave making resistance becomes dominant.

How to determine resistance curve of a ship?

This method of determining a ship’s resistance curve involves modeling the ship’s hull in a computer and then solving three-dimensional fluid flow equations for the flow of water around the ship’s hull. These equations are solved through a method called “computational fluid dynamics” using the finite element method of analysis. This method requires a large amount of computer memory and the ability to solve thousands of simultaneous equations. Computer modeling of the hull and the flow of water around the hull produces fairly accurate results (if you have a large enough computer) and can be used to compare many different hull designs.

What is added resistance?

Added resistance due to waves refers to ocean waves caused by wind and storms, and is not to be confused with wave making resistance. Ocean waves cause the ship to expend energy by increasing the wetted surface area of the hull (added viscous resistance), and to expend additional energy by rolling, pitching, and heaving. This component of resistance can be very significant in high sea states.

How does a propeller blade work?

propeller blade works in the same manner as an aircraft wing. Water flow over the propeller blade creates a pressure differential across the blade which creates a lifting or thrust force that propels the ship through the water. If we were to make a cut through a propeller blade, we would see that the blade has a shape similar to an aircraft wing. Figure 7.20 illustrates this concept. Water velocity over the suction back of the blade is greater than the velocity across the high-pressure face of the blade. Using Bernoulli’s equation (from Chapter 1), this velocity differential across the blade results in a pressure differential across the blade. The resultant lifting force can be resolved into thrust and resistance vectors. It is the thrust vector that pushes the ship through the water.

What is the purpose of propulsion?

The purpose of the propulsion system on a ship is to convert fuel energy into useful thrust to propel the ship. Figure 7.1 shows a simplified picture of a ship’s drive train.

How fast is a model 5 feet in length?

model 5 feet in length is being towed at a speed of 5 ft/sec in fresh water at 59°F (ν = 1.092 x 10-5 ft2/s). Calculate the model’s Reynolds number.

What is the dimensionless form of viscous resistance?

The dimensionless form of viscous resistance is the coefficient of viscous resistance (CV). This coefficient is a function of the same properties that influence viscous resistance itself: hull form, speed, and water properties. The equations for the coefficient of viscous resistance that follow are empirical products of many years of towing tank testing, and are internationally recognized by the International Towing Tank Conference (ITTC). The coefficient of viscous resistance takes into account the friction of the water on the ship as well as the influence of hull form on viscous pressure drag.

Basic Directions

The diameter around which the earth rotates is “The Axis of Rotation”. Where it meets the earth form the Geographic North and South Poles

Chartwork and miscellaneous terms

A COMPASS ROSE (see pic) is a easy means- for a navigator- of finding direction on the chart and also plotting a ship’s course, besides taking bearings (angles) of objects with a compass. Called because it looks like a rose petal opened up, it is graded from 0 degrees to 360 degrees, with 0 being North, 90 being E, 180 being S and 270 being W.

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