Determination of the vessel speed by the propeller speed mode. Determination of speed by reference point
05/12/2016
To become navigator by a professional, you need to read a lot of navigation, which is authored by scientists. In this article, in this article, using a simple, not loaded with complex terminology language, we will try to find out - what speeds are taken into account by the navigator.
When we talk about the speed of a ship, we are considering two quantities. One of them - this is the movement of the vessel on the water... Direct connection between the propeller, the ship's hull and the aquatic environment. The second is movement of the ship in relation to peaceful space... This is the path, the segment that we have passed in a certain time. The fact is that the world Ocean and the entire water envelope of the Earth are not static. It is free in its movement, although it is subject to physical laws. The system of the world's waters, their interaction, creates the movement of water masses, and a sea vessel, along with any straw, participates in this movement of a colossal scale. Also, do not forget about wind, which also affects the speed of the vessel. More about everything.
STW - Speed \u200b\u200bThrough the Water - Vessel speed over water
SOG - Speed \u200b\u200bOver Ground - Vessel speed relative to the ground
Knot - Knot - unit of measure for ship speed. Nautical mile per hour.
So, we are on watch, we go from point A to point B. Full speed, the propeller threshes the water, our ship, swaying on the waves, cuts the water with its stem. - this is the water in which our ship is immersed, its hull and propeller. With the positive work of this system, the ship, like a physical body, moves in the aquatic environment, receiving an emphasis. Compare this with a swimmer who methodically rowing from one wall to another in a pool. His body moves through the water, which is limited by the walls of the pool, does not have a current that would affect the swimmer. Using only his physical strength, he overcomes the distance, passing the way through the water.
Let's go back to our ship. Since it is in the system of world currents, then all this water mass moves in a certain direction, taking the ship with it. If we stop our ship STW will be 0. But we will move across the globe with the water, moving from one point to another. Let's put the ship in motion again. Drawn on the navigation map location... Spotted time... New location... Measured distance traveled, divided by timethat we detected. Received the speed of the vessel relative to the ground - SOG... Consider our ship abstractly as a physical point that moves across the planet at a certain speed. 
Let's remember our swimmer. After the pool, we invited him to swim in the river. At first he tried not to row, and was carried downstream. The speed of movement relative to the coastal objects became equal to the speed of the current. He began to paddle upstream. To get back to where he started from, he had to swim faster than the current. He swam quickly relative to the water ( STW) as in a pool. But relative to coastal objects, his body did not move so quickly. The river flow "ate" him SOG... And so, if he floated downstream, it would help him navigate.
Lag - a device for measuring the speed of a vessel on water (there are different types, in more detail These are the simplest and primitive examples. For a complete understanding of the picture, the navigator should learn the basics vector geometry, namely, addition and subtraction of vectors.
In modern navigation we have at our disposal a device satellite observation — GPSwhich continuously gives location vessel, respectively, calculating SOG, which undoubtedly helps the skipper during work.
Further on SOG can be significantly affected by creating wind drift. Especially, it affects ships with great sailingyu, such as container ships, RO-RO, passenger ships, large ballast tankers and others. For example, in a strong headwind SOG will decrease, and vice versa, with a favorable direction, the wind will "help" the vessel to overcome the water resistance.
We hope this introductory article " Navigation. First steps. Ship speed. " will help you in comprehending science Navigation .
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Navigation. First steps. Ship speed. (c) NavLib
Along the lag. Orientation accuracy largely depends on reliable information about the ship's speed. When sailing on lakes and reservoirs, the average speed relative to the bottom can be determined from the lag.
Lags come in various designs. The turntable logs, operating on the principle of a hydrometric turntable, are stationary and extend as needed from the bottom of the vessel. Hydrodynamic logs are two tubes with the help of which the seawater pressure is measured during movement and parking. The higher the speed, the higher the pressure in one of the tubes. The difference in pressure can be used to judge the speed of the vessel. In general, logs are complex electromechanical devices.
The river flow, acting on the log, makes it possible to determine from it only the speed of the vessel relative to calm water, but not relative to the banks. In addition, uneven currents and vessel movement in channel bends distort the log readings.
Along the length of the ship's hull. The boat speed relative to the bottom can be determined by one of the following methods. At the bow and stern, two planes of superstructures are selected, perpendicular to the centreline plane of the vessel, or two objects that create leading sighting planes. There are two observers in the fore and aft sighting planes H and K (fig. 78). Observers select a stationary object P, located on the shore or water. At the moment the object enters the nasal sighting plane, the observer H gives a signal by which the observer TO notices the time. At the moment the item arrives P in the aft sighting plane observer TO. also makes a time stamp. The speed is calculated from the distance between the sighting planes / and the time.
Time marks can be made by the third observer, who is on the bridge, according to the signs of the observers H and TO when the item arrives P in the sighting plane.
Figure: 78. To the definition of speed
movement of the vessel along the length of its hull
Less accurate speed is calculated when sighting an object P on one ship's item, when the leading sighting plane is absent or when the object of sight is on the abeam of the stem and stern of the ship.
Using the direction finding of the subject.The essence of this simple and reliable
the way is as follows. In the diametrical plane of a vessel moving in a straight line, between points a and b (Fig. 79) measure the distance lcalled the basis. Being at points a and b , observers at the same moments measure the angles a1 a2 a3 B1 B2 B3, etc. between the basis and the direction to the object P.
When processing the obtained measurements, an arbitrary line is drawn on a sheet of paper, on which a point is put down, which determines the bearing being taken. From this point at measured angles a1, b1, etc., bearing lines of arbitrary length are drawn. Noticing the baseline length on the ruler at any scale, place it between the bearing lines, parallel to the course, until it touches them with the corresponding marks. Thus, the position of the ship's hull at the moments of bearing is determined. The distance traveled by the vessel during the direction finding, taking into account the accepted scale, is taken directly from the diagram.
To construct a scheme, two direction finding is sufficient, but the result is more reliable with several direction finding.
The direction finding of an object is carried out using a compass or other goniometric instrument. In the absence of them, a tablet is used, which can be a sheet of plywood, thick cardboard, a piece of wide board or a deck table.
A tablet with a sheet of paper is placed over the site of sight. A line is drawn on the sheet that coincides with the base line. The direction finder is a wooden block with a straight edge.
The observer at the time of direction finding, directing the cut of the bar to the object, draws a pencil line and marks it with the measurement number. The corners are removed from the tablet using a protractor.
Figure: 79. To determine the speed of a vessel using direction finding from it an object
Direction finding is carried out as follows. The observers, having checked their watches, disperse to their places. At the same moments, for example, after 15 or 20 s, they are bearing the same object. Direction finding can take place according to signals from a third observer. By determining the distance and time traveled, it is easy to calculate the speed.
The proposed method is applicable to determine the maneuverability of a vessel: inertial path, circulation, etc.
By the relative speed of approach of ships. Knowing the distance between oncoming or overtaken vessels, as well as the speed of the oncoming or overtaken vessel, you can determine the speed of your vessel or, conversely, calculate the speed of the oncoming or overtaken convoy from your speed. |
Let's designate: S - distance between ships, v1 - the speed of our vessel, v2 is the speed of the oncoming or overtaken vessel, t - rendezvous time. Then
In this formula, the plus sign "+" is taken for the case of meeting ships, and the minus sign (-) is taken for overtaking.
When overtaking ships, the relative speed of approach is equal to the speed difference, and when meeting, the sum of the speeds of both ships. In other words, in the first case, the overtaken vessel seems to be standing still, and the overtaking one goes at a speed equal to the difference in their speeds. In the second, one of the ships seems to be standing, while the other moves at a speed equal to the sum of the speeds of both ships.
During swimming, the given formula has limited application and can only be used in special cases. Therefore, the determination of the speed, as well as the time and distance traveled by vessels during meetings and overtaking, can be made according to the universal nomogram of DK Zemlyanovsky (Fig. 80). It is easy to use, applicable in ship conditions and allows you to quickly solve any problem without intermediate calculations, provided that the ships are moving the same or parallel courses.
The nomogram has three scales, each of them for convenience - double dimension. The rule for using the nomogram is clear from its key. For example, the distance between a motor ship traveling at a speed of 20 km / h and the pushed convoy at the time of signaling the divergence is 2.5 km. It is required to determine the speed of the train if the approach time is 300 s.
To determine the speed of the pusher, apply a ruler (pencil, sheet of paper, thread) on the upper scale to the 300 s mark (see Fig. 80), and on the middle scale to the 2.5 km mark. The answer is read on the lower scale - 30 km / h. This is the joint speed of approach, therefore the pusher speed is 10 km / h.
As you know, in shipboard conditions when navigating inland waterways, it is often impossible to perform even simple arithmetic races.
Figure: 80. Nomogram for determining the speed of movement of the vessel, time and distance traveled by vessels when meeting and overtaking
couple Therefore, the nomogram can be used to solve the problems of time and path when meeting and overtaking ships.
We will show the methods of calculating the nomogram using examples. Navigators should not strive to get too accurate values, such as tenths of a meter and a second. At large distances, it is quite acceptable to round the obtained values \u200b\u200bto hundreds of meters, at small ones - to ten or up to a meter.
Example l. The speed of two opposite dry cargo motor ships: going down - 23 km / h, going up - 15 km / h. The distance between ships is 1.5 km. It is necessary to determine the time and distance traveled by motor ships before the meeting.
Decision. The sum of the speeds of the motor ships will be 38 km / h. Find on the lower scale a point with a mark of 38 km and apply a ruler to it. The other end of the ruler is applied to the 1500 m mark on the distance scale, and the answer is read on the upper scale - 140 s.
The speed of the going ship from above is 23 km / h. We apply a ruler on the lower scale to the 23 km mark, and the other end of the ruler to the 140 s mark, the answer is read on the distance scale - 900 m.Then the path traversed from below by the ship going down is 600 m.
Example 2. A train 150 m long, going upward at a speed of 8 km / h, from a distance of 300 m, giving the go-ahead, begins to overtake a cargo ship 50 m long, which goes at a speed of 14 km / h. Calculate total overtaking time and distance.
Decision, The full distance, that is, taking into account the lengths of the ship and the composition, is 500 m (300 + 150 4``50 = 500 m). The difference in speed is 5 km / h.
To determine the time, one end of the ruler is applied on the left scale to the 6 km / h mark, and the middle of the ruler to the 500 m mark on the distance scale. We read the answer on the upper scale - 320 s. The total distance traveled by the overtaking motor ship from the beginning of the signal is equal to the product of its speed and the time of overtaking. This is determined by the nomogram in an already known way. The end of the ruler is applied to the 14 km / h mark, and the right end to the 320 s mark. We read the answer on an average scale - 1250 m.
As can be seen from the above examples, using the nomogram, you can easily and simply solve any problems of divergence and overtaking vessels, being directly on the vessel.
Using the radar. To determine the speed of movement, radars are most widely used among technical means. The radar screen has fixed range circles (NKD), with which you can determine the distance. Some radars have Movable Range Circles (RRTs), with which it is even more convenient to measure distances. Having measured the distance traveled on some object using the radar and noticing the time, the speed of movement is calculated.
On the navigation map or reference book. IN In this case, the distance traveled is determined by the map or reference book, and by the clock, the time. By dividing the length of the covered section by the time, the speed of movement is calculated. This method is most common when sailing on river boats.
The constant knowledge by the navigator of the reliable speed of his vessel is one of the most important conditions for trouble-free navigation.
The movement of the vessel relative to the bottom at a speed called absalty,is considered in navigation as a result of the addition of the ship's speed vector relative to the water and the current vector acting in the navigation area.
In turn, the vector of the ship's speed relative to the water (referbodilyspeed)is the result of the work of ship propellers and the effect of wind and waves on the ship.
In the absence of wind and waves, it is most easily determined by the rotational speed of the screws.
Knowing the speed makes it possible to determine the distance traveled by the vessel S about in miles:
S about = V about t, (38)
where V about - the ship's speed, determined by the rotational speed of the screws, knots; t - sailing time of the vessel, h.
However, this method is inaccurate, since it does not take into account the change in the state of the vessel (fouling of the hull, change in draft), the effect of wind and waves. The following factors affect the speed of a boat relative to the water.
1. Degree of loading, list and trim of the vessel. The speed of the vessel changes with the change in draft. Usually, in good weather conditions, a vessel in ballast has a slightly higher speed than when fully loaded. However, as wind and waves intensify, the speed loss of a ship in ballast becomes much greater than that of a fully loaded ship.
Trim has a significant effect on speed change. Generally, nose trim will reduce speed. A significant stern trim leads to the same results. The optimal trim option is selected based on experience.
The presence of the ship's roll causes its systematic departure from the given course towards the raised side, which is a consequence of the violation of the symmetry of the contours of the submerged part of the hull. For this reason, it is necessary to resort to shifting the rudder more often to keep the boat on course, and this in turn leads to a decrease in the speed of the boat.
2. Wind and waves usually affect the vessel at the same time and usually cause a loss in speed. Headwinds and waves create significant resistance to the movement of the vessel and worsen its controllability. The speed loss in this case can be significant.
Winds and excitement of a passing direction reduce the speed of the vessel mainly due to a sharp deterioration in its controllability. Only with a weak tailwind and insignificant waves in some types of ships a slight increase in speed is observed.
3. Hull fouling is observed when vessels navigate in any conditions, both in fresh and salt water. Fouling occurs most intensively in warm seas. The consequence of fouling is an increase in the resistance of the water to the movement of the vessel, i.e. decrease in speed. In middle latitudes, after six months, the decrease in speed can reach 5-10%. The fight against fouling is carried out by systematic cleaning of the ship's hull and painting it with special non-
overgrown paints.
4. Shallow water. The effect of shallow water on a decrease in vessel speed
begins to affect at depths in the navigation area
H≤4T cp + 3V 2 / g,
where H - depth, m.
T cp, - average draft of the vessel, m;
V - vessel speed, m / s;
g - acceleration of gravity, m / s 2.
Thus, the dependence of the ship's speed on the rotational speed of the propellers determined for specific sailing conditions will be violated under the influence of the listed factors. In this case, the calculations of the distance traveled by the vessel, made according to formula (38), will contain significant errors.
In the practice of navigation, the speed of the vessel is sometimes calculated using the known dependence
V \u003d S/ t,
where V - vessel speed relative to the ground, knots;
S - distance traveled at constant speed, miles; t - time, h.
Accounting for the speed and distance traveled by the vessel is carried out most accurately using a special device - a log.
To determine the speed of the vessel, measuring lines are equipped, for the areas of location of which the following requirements are imposed:
lack of influence of shallow water, which is ensured at a minimum depth determined from the ratio
N / T≥ 6,
where H - the depth of the area of \u200b\u200bthe measuring line, m; T - draft of the vessel, m;
protection from the prevailing winds and waves;
the absence of currents or the presence of weak constant currents coinciding with the directions of the runs;
the ability to freely maneuver ships.
Figure: 23. Measuring line
The equipment of the measuring line (Fig. 23), as a rule, consists of several parallel cross-sections and one leading, perpendicular to them. The distances between the cross sections are calculated with high precision. In most cases, the line of movement of vessels is indicated not by the leading line, but by buoys or landmarks placed along it.
Typically, measurements are taken at full load and in ballast for the main operating modes of the engines. During the measurement period, the wind should not exceed 3 points, and the excitement - 2 points. The vessel should not be heel and the trim should be within optimal limits.
To determine the speed, the ship must lie on the compass on a course perpendicular to the lines of the cross-sections, and develop a given speed of rotation of the propellers. The duration of the run is usually measured using the readings of three stopwatches. At the moment of crossing the first secant alignment, stopwatches are started and every minute the tachometer readings are noticed. The stopwatches stop when the second crossing line is crossed.
Having calculated the average time of the duration of the run according to the readings of the stopwatches, the speed is determined by the formula
V \u003d 3600S / t, (39)
where S is the length of the run between the cross sections, miles;
t - the average duration of the run between the cross sections, s; V - vessel speed relative to the ground, knots
The rotational speed of the propellers is determined as the arithmetic mean of the tachometer readings during the run.
If there is no current in the area of \u200b\u200bthe measuring line, then the velocities relative to the ground and water are equal. In this case, just one run is enough. If there is a current constant in direction and speed in the area of \u200b\u200bmaneuvering, it is necessary to make two runs in opposite directions. The relative speed of the vessel V 0 and the frequency of rotation of the propellers pin this case will be determined by the formulas:
Vo \u003d (V 1 + V 2) / 2, (40)
n \u003d (n 1 + n 2) / 2, (41)
Figure: 24. The graph of the dependence of the speed on the speed of rotation
where V 1, V 2 - the speed of the vessel relative to the bottom on the first and second runs; n 1 and n 2
- the frequency of rotation of the propellers on the first and second runs.
When acting in the area of \u200b\u200bthe measuring line of a uniformly varying current, it is recommended to make a third run in the same direction as the first, and the speed, free from the influence of the current, is calculated naboutapproximate formula
V 0 \u003d (V 1 + 2V 2 + V 3) / 4. (42)
If the nature of the change in the flow is unknown or if they want to get a more accurate result, then four runs are made and the speed is calculated by the formula
V 0 \u003d (V 1 + 3V 2 + 3V 3 + V 4) / 8. (43)
The average rotational speed of the propellers in these cases is calculated for three and four runs, respectively:
n \u003d (n 1 + 2n 2 + n 3) / 4; (44)
n \u003d (n 1 + 3n 2 + 3n 3 + n 4) / 8. (45)
Thus, the speed and rotation frequency of the propellers are determined for several modes of operation of the main engines in cargo and in ballast. Based on the data obtained, graphs of the dependence of the speed on the rotational speed of the propellers are plotted for various loading of the vessel (Fig. 24).
Based on these graphs, a table is drawn up to match the speed of the propeller speed or the table to match the speed of the ship's propellers.
If, according to the results of passing the measuring line, any speed and the corresponding rotational speed of the screws are known, then you can calculate the value of the speed for any intermediate value of the rotational speed of the screws using the Afanasyev formula
V И \u003d V 0 (n 1 / n 0) 0, 9, (46)
where V 0 - known speed at the speed of rotation of the propeller n 0 ; V И, - the required speed for the speed of rotation of the propeller n 1 .
Thus, having determined the speed of your vessel according to the graph of its dependence on the rotational speed of the propellers, you can calculate the distance traveled in nautical miles using the formula
where V 0 - vessel speed, knots; t - swimming time, min.
If the distance traveled is known, then the swimming time is calculated: v
These formulas are used to compile the tables "Distance by time and speed" and "Time by distance and speed" in MT - 75 Appendices 2 and 3, respectively.
Calculations of the distance traveled using the speed determined from the rotational speed of the screws V o6 are performed only in the absence of a lag or to control its operation.
5.2. Principles of Measuring Ship Speed
The speed of the vessel is measured with special instruments ® lags ... Currently, the following systems (types) of lags are used on ships:
Pinwheel lags (produced on laglin and bottom).
The speed of the spinner is proportional to the speed of the boat. The proportionality coefficient is determined by testing. The number of turns of the spinner is recorded on a counter indicating the distance traveled by the vessel.
Hydrodynamic logs (GDL).
Receiving devices of these lags measure the pressure of the high-speed water pressure that occurs when the vessel is moving. Based on the measured pressure value (the difference between dynamic and static pressures), the speed of the vessel and the distance traveled by it are generated in the log calculating circuit. To measure the pressure difference in these lags, spring (bellows) and liquid (mercury) differential pressure gauges are used. (LG-25, LG-50, LG-4, LG-6, MLG-25, MLG-50, etc.).
Induction lags (IEL).
The principle of operation of these lags is based on the phenomenon of electromagnetic induction, which occurs when seawater moves between two electrodes in an alternating magnetic field. The source of the magnetic field in the lag is an electromagnet supplied with alternating current. It is enclosed in a fairing, on the surface of which there are two measuring electrodes in contact with sea water. Under the influence of an alternating magnetic field of a magnet, a variable emf. The amplitude of this emf turns out to be proportional to the speed of the electromagnet, and hence the ship. The measurement of the signal taken from the electrodes is carried out using the compensation method. If the hydrodynamic logs give stable readings at V>3 knots., then induction® is practically with 0 knots
Hydroacoustic logs (GAL).
The principle of their work is based on the use of the Doppler effect... A pulse of ultrasonic vibrations sent from the ship is reflected off the ground and returned back to the ship's log receiver. When the vessel is moving the frequency of the received signal will differ from the transmitted one depending on the speed of the drive.
Galasmeasure the speed of the vessel not relative to the water, like all of the above, but relative to the ground and therefore are considered absolutelags ( not relative). However, the stable operation of these logs is possible at relatively shallow sea depths, but the accuracy of their operation is very high.
Lags of all systems, like any other devices, cannot give absolutely accurate readings, they require periodic verification and adjustment. That part of the error in the lag readings that cannot be compensated for is determined on the "measuring line" and then taken into account by the lag correction.
Lag correction - a value equal to the relative error, expressed as a percentage and taken with the opposite sign, i.e.
where S L - the actual distance traveled by the vessel;
ROL- the distance traveled by the vessel according to the log counter ( ROL \u003d OL 2 -OL 1 )
(5.7)
where V 0 - ship's true speed;
V L - vessel speed according to log readings.
5.3. Determination of the ship's speed. Correction and lag coefficient
Ship or ship speed ( V) and corrections to their lags (D L%) are defined in different ways:
on a visual measuring line;
using the ship's radar;
using high-precision RNS;
on a cable measuring line, etc.
All ways to determine Vand D L% differ from each other only in the method of obtaining the true distance ( S) required to calculate the true speed of the vessel ( V 0) ® see. fig. 5.4, \u200b\u200b5.5, 5.6.
Consider one of the methods ®determining the speed of the ship ( V) and its lag correction (D L%) on the visual measure line.
Visual measuring line ®Special equipped testing ground for high-speed testing of ships.
Such a polygon must meet the following requirements:
- be located away from the paths of movement of ships and vessels;
- be free from navigational hazards (\u003e 2 miles) and sheltered from wind and waves;
- must provide freedom of maneuver ( V£ 36 knots.® L= 3miles;V£ 24 knots.® L= 2milesand V£ 12 knots.® L= 1mile);
- be able to ensure the required accuracy of positioning and navigation safety;
- have depths that exclude the effect of shallow water on the speed of the vessel (with a draft of 5 mand V£ 30 knots H³ 95 m).
Figure: 5.1. Visual measuring line
The visual measuring line is equipped with secants ( B, C, D) sections (not<2-х), направление которых перпендикулярно линии пробега судна (рис. 5.1), а расстояние между створами измерено с высокой точностью.
Some measuring lines are equipped with a leading alignment, along which the ship's run line is directed ( AND).
The method for determining the travel speed ( V) and lag correction (D L%) boils down to the following:
® a ship, in a steady-state mode of propulsion operation, i.e. at a constant number of turns of the propellers (screws), makes a run along the leading alignment AND... (In the absence of a leading alignment, the course on the run is held perpendicular to the direction of the cross sections B, C, D).
When crossing the line Isection ( B) at the command "Zero!" the observers' stopwatches turn on and the lag count is removed ( OL 1 ) and counting from the total propeller revolutions counter ( n 1 ).
When crossing line II of the section ( Dor IN) at the command "Zero!" stopwatches stop and are removed: - lag countdown ( OL 2 ) and counting from the total propeller revolutions counter ( n 2 ).
®the true speed of the vessel on the run is calculated by the formula:
(5.8)
where S- distance (from the form or the description of the measuring line) between the cross sections Band D(or Band INor INand D) (i.e. the length of the run, which is set depending on the speed of the vessel on the run: if V<12knots. – 1mile;if a V\u003d 12¸24 knots. – 2miles;if a V>24knots. – 3miles);
t i - average running time in seconds (average time of all stopwatches).
®the speed of the vessel on the run according to the log is calculated by the formula:
(5.9)
where ROL \u003d OL 2 - OL 1 - difference in lag counts (lag counter readings).
®the number of revolutions of the propellers per minute on the run is calculated using the formula:
(5.10)
where 
.
® the lag correction is calculated as a percentage (D L%) on the run according to the formula:
(5.11)
® the lag coefficient is calculated ( TO L) on the run according to the formula:
(5.12)
To exclude the influence of the flow on the results, at each mode of operation of the propellers, the following is performed:
and)®by 2 runs ®if the current velocity in the area of \u200b\u200bthe measuring line is constant;
b)® by 3 runs ® if the flow is not constant and its elements ( TO T , u T) are unreliable.
There should be at least 3 modes of operation of the propulsion devices (as a rule: I- "ПХ" - designated move; II- "SH" - 75% of "PH"; III- "MX" - 50% of "PH"). In each mode, 3 runs are performed (usually) and after calculations we have:
1st run:V О1 , V C1 , N 1 , D L 1 %;
2nd run:V О2 , V L2 , N 2 , D L 2 %;
3rd run:V O3 , V P3 , N 3 , D L 3 %.
® the average values \u200b\u200bof the required quantities are calculated for a specific, assigned, mode of operation of the propellers:
and)® true (relative) speed of the vessel ( V ABOUT) in the mode according to the formula:
;
(5.13)
b)®the speed of the vessel along the log ( V L) in the mode according to the formula:
;
(5.14)
in)®number of turns of propellers (screws) in the mode according to the formula:
;
(5.15)
d)® lag correction in percentage (D L%) in the mode according to the formula:
;
(5.16)
e)® lag coefficient ( TO L) in the mode according to the formula:
. (5.17)
Note:
If not 3 but 2 runs are performed in the mode, then formulas (5.13¸5.17) will take the form:
(5.13and)
(5.14and)
(5.15and)
(5.16and)
(5.17and)
II mode–V O II, V L II, N O II, D L II%, TO L II;
III mode–V O III, V L III, N O III, D L III%, TO L III.
® according to the results of measurements on the measuring line, the following are compiled:
|
and) the graph of the correspondence of the speed of the vessel to the frequency of rotation of the propellers (Fig.5.2) |
b) lag correction correspondence graph (D L%) speed of the vessel (Fig.5.3) |
|
Figure: five. 2 ... Speed \u200b\u200bMatching Graph course the ship's speed of rotation of its propellers |
Rice . 5. 3 . Compliance graph speed lag corrections |
From these graphs, data is taken to fill in the navigator's worksheets (RTS).
Compliance with the speed of rotation of the propellers
and the correction (coefficient) lag
vessel speed detector
Alternative descriptions... (English "lag") time gap between two phenomena
Indicator reflecting the lag or lead in time of one phenomenon in comparison with others
Navigation device
Device for determining the speed of the vessel and the distance traveled
Union of Arab States (abbreviation)
Ship speedometer
Marine ship speedometer, which has nothing to do with AIDS
Ship's device for determining the distance traveled by a ship
Beam under the floor
Ship speedometer
Vessel speed meter
Yacht speedometer
Ship board
... "Speedometer" on the schooner
... "Speedometer" on the ship
Temporary "gap"
Ship instrument
... "Speedometer" on the ship
Lag
Ship "knot meter"
Marine analogue of speedometer
Ship instrument
Marine knot gauge
Speedometer
The speedometer in the car, what about the ship?
Measures the speed of the vessel
Ship "speedometer"
Ship speedometer
Vessel speed meter
Vessel speed measuring device
Time gap between phenomena
... "Speedometer" on the ship
... "Speedometer" on the ship
... "Speedometer" on the schooner
... "Speedometer" on the yacht
In the car, the speedometer, and what on the ship
Temporary "gap"
Ship "speedometer"
M. Morsk. one side, the side of the ship, relative to the guns; fire with a lag, from all the guns of one side. For water barrels: layer, row. A projectile for measuring the speed of a ship: a wooden triangle is thrown in a stand into the water, on a string, measured in knots
Ship "knot meter"
... (English "lag") time gap between two phenomena
