The art of ship handling 

After we have the skill to access the RB change and range of the target visually, we actually get the feeling of danger. Although these techniques should not be the only mean we can use to acquire the danger target. 
Times will come that this is the only way we can rely on in the case of extreme danger. The most favorite advantage of these skills is we can keep the eye on the most dangerous target always, instead of going back and forth to check on the ARPA data or the gyro compass reading. Even the ARPA data cannot totally rely on, if we cannot handle the ship in the correct way. 

ARPA is not Mr. know all 

Why the ARPA data become unreliable in the emergency case? It is because the ship's course or speed changed in short interval from the avoidance actions. ARPA data is based on the speed/course of both ship in the past motion, the actual course and speed of both ship now is still under calculation. Before both ship are steady on the new course/speed, the machine just give the data it calculated from the maneuvering between the original and new course/speed. In emergency case, both ship’s speed and course may change continuously make the speed vector shown on the ARPA CRT incorrect. We should combine our visual ability and the calculation power of ARPA to yield the best usage in lookout skill. 

Another problem is the positive identification of the target. The target display on the CRT is a spot. What is the method to make sure the echo in the ARPA is the correct echo of the target in question. The target's true bearing should be taken from gyro repeater and check with the target's bearing in the ARPA to make sure. When the traffic density is heavy, this technique should have the ability to verify the distance by eye, especially at night time. This is the step should be taken when the target is first sighted as a dangerous target or we should say we got the feeling of danger. After we positive identify the target in question, the ARPA's target number should be memorized for late stage use. However, even this simple step may not have the chance to exercise in the first opportunity. For some special occasion, the danger target just comes out from nowhere (for example: a vessel comes out of anchorage in crossing situation) and we just didn't have the time to ascertain the correct echo in ARPA is the one we sought by eyes. In the emergency, even in the rush, the echo's data should not be assumed as we thought (unless the ARPA is correct set in auto acquisition mode which indicates the true motion of the target). Hence the ARPA's data is useless as we have no time to ascertain the correct echo. 

ARPA get other ship's course, not from the gyro repeater, but calculate from other ship's position change. As we learnt from the previous chapter, the position change when turning will only be visible after the rudder have used over two ship's length. What a precious time wasted. The position change is not readily visible from the ARPA display, but the course change (10 degree) of the target at this stage can be detected by eye. It is more vivid for the human eye's receptor in detecting other ship's course change. In the other hand, the ARPA is more accurate in speed calculation and range detection which is no way we can match with machine. 

Maintaining the heading steady in maneuvering 

The usual mistake in ship handling is too much course alternation or course change continuously. We use the bold rudder to swing the ship's heading for avoiding the imminent danger. At any event the ship's heading should be under totally control. As long as the circumstance permit, the heading of the ship should steady as soon as possible for continuing the assessment of the collision risk and can avoid the distraction thereof. This practice is benefit for both the ARPA and visual bearing taking. There are times when we avoid one danger target and come into another danger with the second target after the course/speed change. Cutting out the unnecessary swing time as much as possible to steady the vessel's heading is vital for assessing of the risk of collision. 

Altering the course to avoid the collision can be done in two ways. One is give the quarter master the course to steer, the other is give the rudder order only and check the swing by our own discretion. The first one is the lazy one. Each quarter master has different personality, so as the steering style. Sometimes their steering style may not meet our requirement, even worse they will make mistake sometimes by human natures. 
If we must give the course order to quarter master in the first method, we should give the rudder order first and check the correct rudder order been executed. Make sure the desired rudder order had reached, then give the intended course to quarter master to steady. This is a more reliable method. By doing so we can ensure that the course order is carry out correctly. 

The second method should carry out whenever possible:  
Give the rudder order and check it by rudder indicator. 
Wait for the swing begin and check vessel’s turning rate. 
Verify the bearing change of the target and apply the counter rudder to stop the swing. 
Ask the quarter master to steady on the new course. 

Steady on the new course

When and how many counter rudder order should be used is the art of ship handling. But we dare to say that for stopping the swing efficiently: it need almost twice the original rudder order to stop the swing, i.e. Starboard ten to stop a port five order. This characteristic is even more profound when we try to swing the vessel by hard over rudder order. When a full swing developed, it is almost impossible to overcome the turning momentum immediately by the counter rudder along. We need some extra propeller expellant current to work on the rudder to stop the already developed swing. If this is happen in the open sea which we are already in full sea speed or in the confined waters which we proceed in full ahead with no extra engine power to use, we will suffer the prolonged over-swing which may lead to undesired results.  In this point, we can understand why we should proceed in safe speed all the time which, by other words, is reduced speed. 

Course altering in 4-6 N. Miles range

 
As we see in the diagram of turning circle, in the first stage of turning, the heading make no so much difference in each rudder angle been used. After the heading begin to swing, it is different story for each rudder been used. The more rudder angle been used, the fast the turning rate is. If the crossing vessel is coming from starboard side, usually we will use the starboard rudder to swing own ship to her stern. By 6 SL advance, even we only use 5 degree starboard rudder, own ship will have one SL transverse distance away from the original course which should be enough to avoid the POC. Comparing 4 SL advance, only the hard starboard rudder can achieve the one SL transverse distance.  If these two or three SL advance is essential on the avoidance action, there is nothing wrong to use the hard over rudder in the first place. In other circumstance, we should avoid to use too much rudder angle to avoid the unnecessary over-swing. 

For the normal purpose of collision avoidance, the heading change in the end-on or overtaking case is usually 10 to 20 degrees. For the crossing case, the heading change should be readily apparent to another vessel observing visually or by radar; no hard over rudder should be used. So the situation when the hard over rudder should be used is in the emergency 

For a crossing situation involving a risk of collision, the maneuvering to avoid the collision is illustrated above. The course is altering to the stern of the target vessel at the first action. After the relative bearing of target vessel increased in the port bow, the course comes back to the original course step by step. Keeping the target vessel always on the port bow to clearly indicate own ship’s intention to give-way. This maneuvering has the effect to keep the safe distance always regardless the stand-on vessel’s following actions. By the COLREG, the stand-on vessel should keep course and speed when the give-way vessel takes the avoidance action. This is true when only two vessels are involved in the risk of collision. If the stand-on vessel has the obligation to give way to third vessel, this is the safest way for the give way vessel in heavy traffic to avoid all close quarter situation at once. In the true plotting dispatched from the shore surveillance radar at Dover strait below, this shape of track appear twice. Each dotted mark on the track is 6 minutes run. The shape difference is due to the speed difference of these two vessels. Another vessel should use this practice is the green track vessel going south-westerly direction. A collision happened in later stage although other maneuvering had been taken to avoid it.       

Course altering in 1-2 N. Miles range 

The overtaken vessel take the avoidance action in this 1-2 n.m. range is allowing more time to evaluate the overtaking vessel’s movement. Small course alternation may be adopted by the overtaken vessel to compensate the leeway caused by the current or wind effect. Different vessel has different drifting rate to the same tidal current. Too early action to avoid the overtaken vessel may result in another close quarter situation make the overtaking to go around too far away from the original course. In the illustration above, the light blue track vessel going north-westerly direction is overtaking the pink track vessel. The pink track vessel gives way to the green track vessel. The overtaking light blue track vessel goes through original course without any avoidance action.       

The avoidance maneuvering is like give-way to a crossing vessel. At two n.m. range, overtaking vessel alter course sharply to starboard side, not alter course 5 or 10 degrees and wait the safe passing distance reached. This leaves no stress on both vessels to wait and see. Overtaking vessel can shorten the avoidance action time and go back to a steady course earlier to access the collision risk with other vessel ahead. From which side to overtake the target vessel, some mariner would like keep the target vessel on the port side and leave the starboard side sea room free for any avoidance actions needed for later stage. The red track vessel going south-easterly direction is overtaking purple track vessel on the portside and there is a collision risk with the green track vessel. Before the red track vessel clear of the purple track vessel, she is restrained to alter course to starboard side to take earlier action to avoid the collision. Others may decide to go through the least deviation route. For blue track going north-westerly vessel, she has two vessels ahead to overtaking and two other vessels crossing from the starboard side. The avoidance action to her is once for all. The light blue track vessel going on the same direction is overtaking the pink track vessel and has two crossing vessels from the starboard side. She has taken no action at all and has cleared all targets at the scene. The route choice of her may be correct, but she is still under the obligation to give way to these three vessels once they decide to take other action.     

For the crossing vessel in this range, the maneuvering is relatively compact leaves no room for any mistake of human factor or mechanical malfunction on both vessels. The vessel comes from starboard side is under the obligation to stand on the course and speed. One study based on an assumption that the stand-on vessel may has the steering gears malfunctioned when under way at any moment. The possible turning diameters of each degrees the rudder angle been stuck are the areas a give-way vessel should be avoid. The more rudder angle been stuck, the narrower diameters will be. The possible area covered by the rudder stuck is smaller when the rudder angle is bigger. This smaller area seems pose lesser threaten to the give-way vessel when she take the avoidance action. But the heading change and the transverse distance gained are more quickly, in another word, are in shorter time notice. When the give-way vessel had detected the sudden course change of the stand-on vessel, the reaction time will be less. Another malfunction from the mechanic is lost main engine propulsion due to various causes. The obligation of the give-way vessel is any vessel approaching from starboard side up to 111.25 degree relative bearing by the COLREG. When the give-way vessel maneuvers to alter heading to the stern of the stand-on vessel, both vessels has the possibility of malfunction of the machinery. The give-way vessel will be the one to be damned once any collision happened for not taking earlier action.                    

Course altering in less than 1 N. Miles range 

In this range, the avoidance action is not as simple as the course alternation. When the collision seems inevitable, the OOW will have the first instinct to stop the engine. This instinct may comes from the court verdict in the collision case. Reducing speed by the engine is one of the options to avoid the collision as we can see it form part of action in COLREG Rule 8 Action to avoid collision: (e) If necessary to avoid collision or allow more time to assess the situation, a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion. The rudder effect (Re) is consisted of rudder area, the speed of water passing through rudder plate and the rudder angle been used. 

l   Re is proportional to the rudder area.

l   Re is proportional to the square of water speed.

l   Re is proportional to the sine of rudder angle

l    is referred as effective rudder area

The speed of water passing through rudder plate is consisting of two parts. One is the ship’s speed and the other is the water expelled from the propeller. V=Vs+Vp. Vs is the speed of the vessel. Vp is the propeller expelled current speed which we refer as engine speed.

Turning without the propeller expellant current is called coasting, also known as Titanic Effect due to the OOW of “Titanic” stopped the engine first when he saw the iceberg ahead. When the collision risk is imminent it is hard to tell “Does the rudder effect is enough to avoid the collision?” For the turning maneuvering need at least 4.5 ship’s length to accomplish and the distance judgment is hard under the extreme mental stress. If one dedicated OOW is assigned in radar observation and report the range when master needed to decide what action to take to avoid the collision will be a great help to ensure the success of avoidance action. The choice is how much rudder angle should be used to effective the turning. Stop the engine in the first instant may not be the correct choice if there still have ample distance. The ample distance is more than 4.5 ship’s length. 

One collision case has shown that overtaking vessel's stern hit the overtaken vessel in the Japanese waters by third mate. The reason is third mate mistook the stern light of overtaken vessel as one fishing boat and take the drastic rudder order to avoid the collision when he realized the truth. OOW cannot steady the ship heading under the full rudder turning. The correct timing to midship the rudder and to apply the counter rudder to stop the swing is a common problem to junior OOW.

Each time we use the hard over rudder to avoid the danger. As the ship’s bow begins to swing, the necessary heading change should be estimated. Bear in mind that there is always some extent of over-swing when the hard over rudder been used. Apply the counter rudder in time to stop the swing just in the same/reciprocal course. 

For shorten the time to steady on the same/reciprocal course, the hard over rudder should be used to minimize the time needed to the desired course. In the hard rudder turning curve, the tactical center is located in about one and half SL advance position. Once ship advanced 1.5 SL, the turning will begin accelerate to a steady rate and will advance about another 1.5 to 2 SL to complete the turn. It is in this stage or second stage (ship turning in a steady rate in second stage) the rudder should reduce to midship to check the turning rate of the vessel. The counter rudder should apply 10 or 20 degrees before the intended heading is reached. 

COLREG Rule 17 Action by Stand-on Vessel (a) (i) Where one of two vessels is to keep out of the way the other shall keep her course and speed. (ii) The latter vessel may however take action to avoid collision by her manoeuvre alone, as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these Rules. (b) When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision. (c) A power-driven vessel which takes action in a crossing situation in accordance with subparagraph (a) (ii) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side. (d) This Rule does not relieve the give-way vessel of her obligation to keep out of the way. 

In the 8-4 n.m. range, stand-on vessel shall keep her course and speed when give-way vessel is to keep out of the way. In the 4-2 n.m. range, stand-on vessel may however take action to avoid collision by her manoeuvre alone, as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these Rules. In the 2-1 n.m. range, When, from any cause, the stand-on vessel finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision. A stand-on vessel takes action in a crossing situation to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her port side. In theory, there are two exception stand-on vessel may alter course to port to avoid the collision. One is stand-on vessel about to hit the give-way vessel’s stern when give-way vessel has passed its bow. If the stand-on vessel alter course to starboard side will increase the collision risk and hit the venerable part of give-way vessel’s engine room. The other is give-way vessel has not taken avoidance action to keep clear of stand-on vessel’s track and has the tendency to hit stand-on vessel’s midship section. The port rudder will have the side kick effect to lift up the stern to reduce the impact strength as shown on the drawing below.

For the former case, the RB of the give-way vessel is reduced to zero from the port side. The stand-on vessel’s obligation shall keep her course and speed by the COLREG Rule 17(a) (i). Stand-on vessel had the chance to take early action by the COLREG Rule 17(a) (ii) to avoid collision by her manoeuvre alone, as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with COLREG Rules. However, the avoidance action took according to Rule 17 (a) (ii) is not compulsory as the Rule use the word “may however take action to avoid collision”. The obligation of stand-on vessel comes back when, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision. The hard port rudder is compulsory for the former case when the RB of the give-way vessel is reduced to zero from the port side. Take the avoidance action when the RB reduced to zero is theoretically correct as we look at the too late case. The heading change will be apparent only after the rudder been applied after 2 SL advance. Waiting the RB of give-way reduced to zero may end up with the collision. This 2 SL immobilized period of give-way vessel should also take into account. Two SL before the collision spot is the last chance to avoid the collision. If we try to find some visual clue from the RB of give-way vessel, it will be clearly show that at the last stage the RB of the stand-on vessel will be appreciably decreased. The stand-on vessel’s action to avoid the collision is better be early than late in this case.  

For the later case, the RB of the stand-on vessel is increased slightly or almost unchanged. For the collision consequence, the later case (hit by give-way vessel) is more dangerous than the former one and if stand-on vessel tries to take early action to alter course to port side may end up with collision to be blamed by the court for violation of COLREG Rule 17(c). Adding the possible action of the give-way vessel alter course to starboard side at the last moment, the hard port rudder better be late than early for the RB of the give-way vessel is increasing slightly. If the hard port rudder is applied at the last moment, the vessel’s heading will not alter accordingly in the first two SL advance. The effect of hard port rudder will mainly use to reduce the collision impact strength. Theoretically, the give-way vessel has take action to avoid the collision or not, the RB of give-way vessel should increase to 180 degree to clear of stand-on vessel’s track. The RB of give-way vessel is increasing slightly in this case. For the stand-on vessel to take the action to avoid the collision safely, the first choice is always to increase the RB of give-way vessel. At the same distance away, the track of port side turning compare with the starboard side turning is illustrated below. The early action of altering course to port side may cause the end to end collision. Even the stand-on vessel can clear the track of give-way vessel; the collision risk is still present for the stand-on vessel is under the possible track of the give-way vessel. The safety margin between too early and too late is very narrow in the later case (RB of the give-way vessel is increasing). The decisive master will detect the slightest tendency of the give-way vessel’s RB increasing and take the bold action to alter course to starboard side. The art of ship handling to pick up the correct timing and action to avoid the collision is beyond these discussions here. These materials presented here is to simulate the most dangerous situation and provide the proper mind setting to handle the situation correctly.      

When the collision is imminent, the best heading we choose to steer should be the reciprocal course or the same course as other ship. The best aid to avoid the collision is altering course to the same/reciprocal course of other ship and steady on the course to minimize the collision area. This is when two ship's distance is very close and the collision is almost inevitable. 

Avoid the drastic rudder order

If it is believed that some maneuvering space still left for our discretion. We don't need the drastic change to the same/reciprocal course as other ship. Unlike the situation above, steering to the same/reciprocal course and steady on it, the best decision should be stay in the safest position to avoid the possible area of collision. 

The safest position is no collision area or no collision risk area. Own ship follows general direction of the traffic flow in the Singapore Strait. One overtaken vessel is at her starboard side and one crossing is coming from starboard side also. Own ship’s heading is chosen by the master and the position fixing is carried out by the OOW. The risk of collision present with the crossing vessel. For three set courses, the maneuverings to avoid the collision with the black vessel are totally different. The green vessel maneuvers to reach the stern area of the crossing vessel. Without appreciable course alternation been conducted, green vessel can maneuver to avoid the overtaken vessel ahead after clear of the crossing vessel. The grey vessel keeps the original course and has collision risk with black crossing vessel. The master has to avoid the crossing vessel as usual. The transverse distance needs to be covered is half ship’s length. For the red vessel reached the bow area of the crossing vessel, the avoidance actions will be drastic. In the red vessel’s situation, no matter how good of the master’s maneuvering, the situation is not necessary to be so.            

If we look at the fig c-5, the possible area of collision is two SL diameter circle. In theory, any course change that can make one SL transverse from original course line will be enough. In the illustration above, we can see that three ship departure at same position in about the same course. When reach the possible area of collision, the vessel's position more close to the center of the possible area of collision will take the more drastic action for creating this one SL clearing space. 

The collision course is not only one heading line we steered. It's a heading sector from the OP line to OS line cutting the possible area of collision. 

For the give-way vessel keep original course and speed, 
If the heading we steered is in the sector of, the target's RB will decrease slightly which imply that target may have the chance to pass our bow. The likely collision situation in the last stage is OS hitting the give-way vessel’s starboard side. In this meeting situation, OS has the freedom to maneuver at the last stage unless the RB change is discontinued by the give-way vessel’s action to avoid the collision. The best aid to avoid collision in this situation is reducing speed of stand-on vessel at the last stage. In the COLREG Rule 6 Safe Speed : Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions.
If the heading we steered is in the sector of, the target's RB will increase slightly which imply that target may have the chance to pass our stern. The likely collision situation in the last stage is give-way vessel hitting the OS port side. The tendency of the RB increasing of the give-way vessel will not cease unless the stand-on vessel alter course to port side or reducing speed. The best aid to avoid the collision in this situation is altering course to starboard side. In the COLREG Rule 7 (c) A power-driven vessel which takes action in a crossing situation in accordance with subparagraph (a) (ii) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.

The dangerous situation is the relative bearing never change when ship in a steady course. This is a rare case. Usually, the RB change is only visible at the last stage in a collision case. In which sector own ship are in will depend on the visual clue we got from the RB. This little RB change implies the best aid to avoid the collision in the last stage. In the COLREG Rule 17(a) (ii) to avoid collision by her manoeuvre alone, as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with COLREG Rules. As soon as it becomes apparent to her that the give-way vessel’s RB is not changing apparently. If master think it is necessary this is the time stand-on vessel to take action to avoid the collision. 

In the heavy traffic area like Singapore Strait, the idea position to steer is like the green vessel. For a prudent navigator, this waterway is always armed the steering with an experienced quarter master. The ship’s course is under constant modifications to compensate for the tidal current and frequent altering to adjust for the fishing vessel around. From these three vessels meeting situation, it is the master’s experience to lead the vessel to the safe position. One SL transverse space can make a great difference.

How to create the necessary one SL transverse space? In the advance of one nautical mile, ten degrees course change will do (1852 meter x sin10 = 322 meter). In the 4-2 n.m. range, stand-on vessel may adjust her course to create this one ship's length sea room to avoid the risk of collision. By the recommendation of MCA, the stand-on vessel shall take the best aid action to avoid the collision is at 2 n. Miles range. However, in COLREG the specific range is not stipulated.

In case of OS heading is in the  sector, the stand-on vessel is recommend to adjust her course 10 degree to starboard side in 2 N. Miles range as the give-way vessel's true bearing is decreased, or the true bearing have no change. The stand-on vessel’s best aid to avoid the collision does not necessary means the boldest action in 2 N. Miles range. By altering course 10 degree to starboard side can gain some safer position from the possible area of collision to avoid any drastic maneuvering in the last minute. Unless the give-way vessel increase speed or alter course to port side, stand-on vessel will clear the area of collision. When give-way vessel comes closer, the RB change shall access once more to decide the best aid to avoid the collision.  

By this assumption, In case of OS heading is in the  sector, the stand-on vessel is recommend to adjust her course 10 degree to port side in 2 N. Miles range. By the COLREG, alter course to the give-way vessel's direction should be avoid. So, alter course to port side seems conflict with the COLREG.  The question is " does this is the best aid to avoid the collision?" As my opinion, the course change to port side should judge from the tendency of give-way vessel's bearing change. If the give-way vessel's bearing change in 2-4 n.m. range is fast which may have the possibility that give-way vessel already take some action to pass our bow, stand-on vessel alter course to port side 10 degree is acceptable. If the give-way vessel's bearing change is slowly all the way but the RB is decreasing, the better choice is still alter course to starboard side with 20 degree course change at 2 N. Miles range.  

Beside all these factors using rudder effect to reach the safe position, the proper control of the ship’s speed to get the same result is also very important. In the COLREG Rule 6 Safe Speed: Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision.

By reducing speed along, no avoidance action is needed to avoid the collision. This can be called safe timing for transit. 

Summary 

In the extremity of the collision avoidance, knowing the further limitations of ARPA's usage

1. 1.     The ARPA's data is useless unless we have time to ascertain the correct echo.
2. 2.     ARPA get other ship's course by calculate from other ship's position change.
3. 3.     The ARPA is more accurate in speed calculation and range detection.

is breaking the myth of the junior officer depend on the ARPA assessment, even in the extremity. Cutting out the unnecessary swing as much as possible to steady the vessel's heading 

1. 1.     The heading of the ship should steady as soon as possible for continuing the assessment of the collision risk. 
2. 2.     We need almost twice the original rudder order to stop the swing efficiently.
3. 3.     The prolonged over-swing may lead to undesired results.

is breaking the bad habit of senior officer in controlling the wheel to wait and see the effectiveness of its collision avoidance actions. Handling a full rudder turning

1. 1. When ship turning in a steady rate in 2 to 3 SL advance, the rudder should reduce to midship to check the turning rate.
   1. 2. The counter rudder should apply 10 or 20 degrees before the intended heading is reached.

is preparing the ship handler in the mind set at this unusual maneuvering. The technique to avoid the collision by rudder along is illustrated in this chapter. The concept is steering own ship to the safe position as soon as possible in multi ships situation. Taking the angle of blow into consideration in avoidance actions to minimize the collision area is justifying the usage of port rudder in the extremity. Create one ship's length sea room by adjusting the course or reducing speed to avoid the last minute drastic maneuvering is introducing the concept of safe position in the most effortless maneuvering.  

Our discussion begins from the theory of collision which is the bull’s eye of the collision spot. The possible area of collision is involving the risk of collision. The art of ship handling is in extremity of the collision avoidance. From next chapter, the avoidance actions of stand-on and give-way vessel are the daily practice of OOW in the navigation watch.