Evaporation (yachting)
Due to the evaporation , docking and casting off maneuvers can be carried out in confined spaces or in unfavorable wind and current conditions. The purpose of evaporation is to be able to use thrust (force), derivative force and wheel effect to change position without driving through the water. For this reason, the boat is usually firmly attached to the pier with one or more lines.
There are hardly any limits to the variety of possible maneuvers and the planned maneuvers have to be adapted to the prevailing conditions and “classic” evaporation maneuvers adapted if necessary.
elements
In order to change the position of boats in a deliberate way, specific forces must be used. The available elements for generating power, and thus for carrying out evaporation maneuvers, can be roughly divided into the following four options:
- Thrust from the propeller : rotating propellers displace water and thereby generate thrust. If the water is displaced aft, an opposing, i.e. forward-acting thrust is created. If the propeller rotates clockwise when looking at the boat from aft, the propeller is referred to as clockwise, otherwise counterclockwise. Most yachts are equipped with change gears, i. H. when thrust backwards, the direction of rotation of the propeller is reversed.
- Derivative force through flow around the rudder blade : Since the propeller is usually in front of the rudder blade, the water displaced during forward thrust flows around the rudder blade. By adjusting the rudder blade, the flowing water is deflected and creates an opposing buoyancy force across the ship's longitudinal axis (derivation). Conversely, the propeller displaces the water forwards during backward thrust and the rudder blade is not flowed against - the derivative force can therefore only be generated during evaporation maneuvers with forward thrust, but not with backward thrust.
- Wheel effect through (lateral) flow around the boat hull : the propeller also sets the displaced water in rotation. The swirl increases the area of the rotating water jet. Depending on the direction of rotation of the propeller, water is sucked away from one side of the boat hull and pressed against the opposite side of the boat hull. Depending on the type of propeller (inclined shaft, saildrive (horizontal propeller shaft), ...), the strength of the wheel effect can differ with forward thrust and reverse thrust. As a rule, the wheel effect is stronger with backward thrust, as the water flow is stronger against the boat hull. In the case of forward thrust, the wheel effect can also be easily compensated for by the derivation, whereby it usually does not play a role.
- Line forces : The use of lines for power transmission is an essential part of technical mechanics ( rope statics ). The correct line guidance is the essential criterion for the successful execution of a evaporation maneuver, it is therefore worthwhile to deal more closely with the technical basics. At this point it should only be pointed out that lines are limp and can therefore only absorb and transmit tensile forces in their effective direction.
The elements listed are available for the majority of boats to carry out evaporation maneuvers; yachts with double rudders do not have the option of using the derivative power. Bow and stern thrusters are becoming more common, but are not yet part of the standard equipment of yachts and are not considered in the following illustrations - these can of course be used as support for evaporation maneuvers, regardless of the following explanations.
"Classic" evaporation maneuvers
Some proven evaporation maneuvers are to be described and analyzed here. These maneuvers can only be used as a guide and are primarily dealt with in order to understand the elementary processes. It is the skipper's responsibility to plan, discuss, prepare and carry out a maneuver that is adapted to the situation.
Deposit by evaporation into the fore-ring
This maneuver is recommended from a side position in onshore wind or when there is little space available in front of and behind the yacht lying alongside. The aim of the maneuver is to turn the stern away from the pier, whereby it may be necessary, especially in stronger winds, to continue the turn until the stern is (almost) directed against the wind. In the example given, the yacht is on the port side at the pier, the wind hits the land at a right angle.
preparation
Since the yacht is turned away during the maneuver at the bow of the pier, which must stem are well abgefendert. To carry out the maneuver, a long fore-jump is required, which can be put on slip if necessary . What is essential is the attachment or deflection of the protrusion at a point on the boat that is as far forward as possible - the attachment of the protrusion to the front cleat on the mole side creates a counter-torque and hinders the maneuver or makes it impossible. One variant possible on every yacht is to attach the fore-spring to the front cleat on the side facing away from the pier and to redirect it around the stem.
execution
The yacht can be stabilized in position by evaporation into the projection with a slight forward thrust. Thereafter, aft spring and pre-line be solved easily. Once the stern line is released, the rear of the yacht from the pier begins to turn away. At this point in time, the position of the baffle fenders on the stem should be checked again by a crew member and readjusted if necessary. As soon as the stem (protected by the fenders) is in contact with the pier, the rotation of the yacht comes to a standstill - the onshore wind tries to push the yacht back to the pier. In order to move the stern of the yacht further away from the pier, the derivative power can now be used by hitting the pier. The pivot point of the yacht is in the cushioned stem, the derivative force creates a moment with the lever arm (from the rudder blade to the stem), the wind creates a counter- moment with a slightly smaller lever arm . If the torque generated by the derivative force is greater than the counter-torque generated by the wind, the stern turns away from the pier, in order to increase the torque of the derivative force, the propeller speed can be increased and thus the flow around the rudder blade can be increased. If the stern has been turned far enough away from the pier (it should be in the wind), the clutch can be disengaged, the rudder set amidships and the fore-ring released. If all crew members are on board, it is possible to drive backwards away from the pier.
Sources of error
A major mistake is attaching or redirecting the fore-spring behind the stem. This means that the rotation of the boat away from the pier, which always takes place around the bumper fender on the stem, is hindered by the fore-ring - the fore-ring creates a counter-torque ( ). This is illustrated in the graphic below through an obvious approach: It shows the yacht in its original position (solid lines) alongside the pier and in its final position (dashed lines) normal to the pier. The fore-spring is attached to four different points. It can be clearly seen that every deflection behind the stem requires an (unrealistic) stretching of the projection in order to get into the desired position.
Another source of error is the (premature) termination of the maneuver before the stern is against the wind. The wind pressure on the freeboard of the yacht decreases disproportionately with increasing angle between the ship's longitudinal axis and the edge of the pier, as shown in the following table:
| Angle between the edge of the pier
and longitudinal axis of the ship |
Proportion of the original
Wind pressure on the freeboard |
|---|---|
| 0 ° | 100% |
| 30 ° | 87% |
| 45 ° | 71% |
| 60 ° | 50% |
| 90 ° | 0% |
The lateral wind pressure on the freeboard is only halved at an angle of rotation of 60 °. Turning the stern into the wind is therefore necessary for the maneuver to be successful in stronger winds. How far the stern is turned away from the pier depends on the actual wind direction. If the wind falls more aft on the boat, turning the stern through the wind causes the wind pressure to support the maneuver and move the boat away from the pier - to what extent this is desirable and how this is used for the maneuver is at the discretion of the Skipper. If the wind is onshore, but with a clearly forward component, then evaporation into the aft spring can be effective.
Deposit by evaporation in the aft spring
This maneuver is recommended from a side position in onshore wind with a strong forward component. It only makes sense if the maneuver allows the bow to be turned away from the pier so that it goes through the wind. In the example given, the yacht is on the port side at the pier.
preparation
Since the yacht is turned away from the pier around the stern during the maneuver, the hull at the stern and the transom must be well cushioned. To carry out the maneuver, an eight jump is required, which can be put on slip if necessary. It is essential to attach or deflect the aft spring at a point on the boat that is as far aft as possible - in most cases this is the stern cleat or the most aft cleat.
execution
The yacht can be stabilized in its position by evaporating into the aft spring with a slight backward thrust. Then the fore-spring and stern line can be loosened without any problems. As soon as the bow line is released, the bow of the yacht begins to turn away from the pier. At this point in time, the position of the baffle fenders on the transom should be checked again by a crew member and readjusted if necessary. As soon as the stern (protected by the fenders) is in contact with the pier, the rotation of the yacht comes to a standstill - the onshore wind tries to push the yacht back to the pier. Since the rudder blade is not illuminated during backward thrust, no derivative force can be generated by the rudder position. To move the bow of the yacht further away from the pier, you can only increase the speed, the only moment that helps the maneuver is that consisting of thrust half the boat's width . The wheel effect has a greater effect when you push backwards, but it only helps if the yacht “happens” to be on the right side of the jetty, otherwise it hinders the maneuver. In most cases the rotation comes to a standstill as soon as the buffer fender is squeezed. If the wind still falls clearly sideways on the yacht in this position, then the maneuver must be interrupted and another maneuvered. In the best case scenario, the bow is in the wind or even hits the yacht on the pier side. As soon as the bow goes through the wind, the clutch can be disengaged and the aft spring released. If all crew members are on board, you can drive forward away from the pier.
Sources of error
A major mistake is trying to perform the casting-off maneuver, even if the wind still hits the yacht clearly on the sea side at the end of the turn. This maneuver is only effective if the wind has a significantly more forward than lateral component at the beginning of the maneuver.
Apply by evaporation into the fore-ring
This maneuver is useful in offshore winds or when there is only a little more space available for berthing at the pier than the length of the yacht. The aim of the maneuver is to turn the stern towards the pier. It is a demanding maneuver that requires experience, a feeling at the helm and a capable crew. In the example given, the yacht is to be laid with its port side to the pier, the wind is blowing away from land at a right angle.
preparation
Since the yacht is turned around the bow to the pier during the maneuver, the stem must be well cushioned. To carry out the maneuver, a fore-jumping is required, as well as a crew member who disembarks with this over the bow and z. B. occupied on a bollard .
execution
In order to avoid the bow being driven away, the yacht must be steered against the wind towards the pier and at the same time take speed out of the yacht when approaching. In the best case scenario, the yacht comes to a standstill at the moment of contact between the bounce fender and the pier and the crew member with the bump can disembark. For the maneuver to be successful, the contact between the stem and the edge of the pier must be maintained; if the longitudinal axis of the ship forms an obtuse angle with the edge of the mole, forward thrust can be used to evaporate into the edge of the mole, thus preventing the offshore wind from drifting away. The projection should be occupied quickly on a bollard or something similar. It is important that the fore-spring does not sag, otherwise the yacht could start moving when the stern is turned towards the pier and the stem could be damaged. You should also avoid pulling up the fore-spring so much that the bow is shifted sideways. As long as the yacht is steaming towards the pier with forward thrust, the crew member should always make sure that the fore spring does not receive any loose parts without pulling on it. As soon as the fore-jump is occupied, the oar is moved away from the pier. Due to the flow around the rudder blade by the propeller, a derivative force acts, which turns the stern around the baffle fender to the pier. If the rotation comes to a standstill due to the increasing wind pressure, the speed can be increased successively. As a rule, the rotation finally comes to a standstill when the baffle fender is about to lose contact with the pier. Now the breast lines and the fore-ring can be deployed without reducing the speed. As soon as the lines are occupied, the speed is reduced.
Sources of error
A common mistake is trying to approach the maneuver at an angle to the wind. As soon as speed is reduced near the breakwater, the wind drives the bow and the boat moves away from the breakwater. If the wind is stronger, starting against the wind is unavoidable.
During this maneuver, the bow runs the risk of being damaged. Since it is carried out on offshore, the yacht is pushed away from the pier (i.e. the danger) in the event of a mistake, so it offers a certain level of security in the event of unsuccessful approaches. Of course, this security is no longer available if the maneuver is to be forced under unsuitable conditions.
If the wind does not hit the pier at right angles, the side for mooring should be chosen so that it always has to be turned over the smaller angle. With forward thrust the wheel effect is usually negligible and neither side offers advantages in this regard.
Cast off by evaporation into the sea-side stern line
This maneuver is suitable for casting off from the side position in light onshore winds. It can only be carried out if there is enough space aft (at least the length of a boat). At higher wind speeds it usually does not lead to the goal. One advantage over steaming into the fore-spring, however, is that the yacht does not have to be turned around the stem - which is not possible with high moles due to the pulpit.
preparation
A very long line is required or several lines must be connected. A rope is used on the lake side on the middle cleat or on the Genoa winch. It is led ashore outside the pushpit and deflected ashore as far as possible behind the stern and again on board on slip, again middle cleat or genu winch. A crew member must be ready to throw off a rope from the mooring line and bring the line on board
execution
To stabilize the yacht, the long stern line can be pushed forward to evaporate and the remaining lines can be loosened. Now the rudder is placed towards the pier, the resulting derivative force pulls the yacht away from the pier. If the movement comes to a standstill, the thrust and derivative force can be increased by increasing the speed. If the yacht is sufficiently far from the pier, the rudder is turned away from the pier and the yacht turns the bow under the stern line. The stern line is released and brought on board.
Sources of error
If the deflection of the stern line on land is too close behind the stern, the poor pulling direction of the line prevents the boat from moving away from the pier. The further the deflection point is from the stern, the lower the force component that holds the stern to the pier.
Another source of error is the occupation of the sea-side stern line behind or at the level of the rudder blade (e.g. on the stern cleat), this prevents the yacht from spinning at the end of the maneuver. The rotation should be achieved by moving the rudder away from the pier, in that the derivative force creates a moment with the lever arm between the rudder blade and the attachment point of the stern line. If the attachment point is just in front of or even behind the rudder blade, the necessary torque cannot be generated - the stern line prevents rotation.
Retracting the stern line after the maneuver, especially in cases where it is fragmented, can lead to problems if, for example, a knot gets stuck on the mole. The line routing should therefore be well thought out before the maneuver in order to prevent problems at the end of the maneuver.
Mooring by evaporation into the landside stern line
This maneuver is suitable for being able to moor alongside in offshore wind - it is also very good as a one-handed maneuver. The implementation is simpler and less critical than when berthing by evaporation into the fore-spring, but it requires more space at the pier and the chances of success are lower in stronger winds.
preparation
Initially, only one stern line is required for the mooring maneuver. However, this must not be occupied on the stern cleat, but must be attached further to the front of the boat (e.g. genoa winch or middle cleat) in order to be able to guarantee the rotation of the boat by the derivative force even against possible wind pressure. The stern line is either brought ashore and occupied by a crew member, but can also be carried out from on board e.g. B. be thrown over a bollard - each variant requires appropriate preparation.
execution
The yacht is steered, stern first, towards the point where the stern should be roughly at the end of the maneuver. If the boat is close enough to the pier, a crew member gets ashore and occupies the mooring line or throws it over the bollard and brings it on board - since this maneuver is carried out in offshore wind, there is a risk of damage if the boat is aborted low as the yacht is being driven offshore by the wind. As soon as the stern line is occupied and tight, forward thrust is given and the oar is placed towards the pier. The derivative force generated by the flow around the rudder blade creates a moment around the point at which the stern line is attached to the board and turns the bow against the direction of pull of the line. As the angle between the line direction and the ship's longitudinal axis increases, the yacht moves on an approximately circular trajectory with a radius corresponding to the line length towards the mole. If the wind pressure on the freeboard due to the increase in the projected area is so great that the movement of the boat comes to a standstill, then the speed can be increased. If the yacht is alongside the pier at the end of the maneuver, the rest of the mooring lines are deployed and the engine speed is only then reduced.
Sources of error
The main source of error is the attachment of the stern line behind or at the level of the rudder blade (e.g. on the stern cleat); this hinders the turning of the bow against the wind and thus the movement of the yacht towards the pier. The rotation should be achieved by laying the rudder towards the pier, in that the derivative force creates a moment with the lever arm between the rudder blade and the attachment point of the stern line. If the attachment point is just in front of or even behind the rudder blade, the necessary torque cannot be generated - the stern line prevents rotation. Stronger winds require a larger lever arm, i.e. the stern line must be occupied on board at a point further forward.
If the pivot point on board is too far forward, the yacht reacts very sensitively to changing rudder angles and varying speeds (thrust) due to the long lever arm. As a rule, mooring the stern line on board is more forward than the middle cleat, but makes the maneuver more difficult without bringing any advantages - in extreme cases, the "stern line" on the front cleat is occupied and the maneuver mutates into mooring by evaporation into the fore-spring.
Evaporation "in the box" with side winds
Especially when casting "out of the box" with a mooring , it is necessary to keep the yacht in position by evaporation, as long as the mooring line has not sunk after loosening - the same applies, but to a less critical extent, when mooring until the mooring is occupied . In order to increase the range of possibilities to evaporate, the stern should be applied to the pier.
preparation
In the case of side winds, only the windward stern line is required; the leeward line should be loosened before the casting-off maneuver in order to reduce the number of sources of error during the maneuver. The windward stern line - usually occupied by the stern cleat when lying down - should be put on slip and attached further forward in order to move the pivot point of the boat clearly in front of the rudder blade (e.g. genoa winch). When redirecting the mooring line ashore, it must be taken into account that it should not be too far, but still be windward of the boat.
execution
Before loosening the mooring, the boat must be stabilized against the lateral wind pressure. By absorbing the thrust, the mooring line pulls the yacht to windward and the angle between the mooring line and the edge of the pier increases until the force component of the line force across the ship's longitudinal axis corresponds to the wind force. In light winds, an equilibrium of forces can be set simply by thrust and line direction. After loosening the mooring, the boat can be held in position until the mooring line has sunk.
In stronger winds, the reaction force generated by the thrust in the line is usually not sufficient to counteract the wind force acting from the side. In these cases a derivative force can be generated by turning the rudder in order to turn the bow of the yacht against windward. By placing the stern line well in front of the rudder blade, the derivative force can be used to generate a moment around the point of attachment of the stern line on board and twist the boat. By turning the bow towards windward, the angle enclosed by the thrust force and stern line increases , the force component of the line force transverse to the ship's longitudinal axis is increased and thus the wind force is counteracted. If the boat is only stabilized in the box by evaporation, the mooring line can be released and put down as soon as the mooring line has sunk.
Sources of error
The main source of error is the attachment of the stern line behind or at the level of the rudder blade (e.g. on the stern lamp); this hinders the rotation of the bow against the wind and thus the reinforcement of the line force components transversely to the ship's longitudinal axis (to windward). The rotation should be achieved by laying the rudder towards the pier, in that the derivative force creates a moment with the lever arm between the rudder blade and the attachment point of the stern line. If the attachment point is just in front of or even behind the rudder blade, the necessary torque cannot be generated - the stern line prevents rotation.
Compared to most other evaporation maneuvers, in which the rudder is fully turned at the beginning and only thrust (i.e. the engine speed) is used in the further course of the maneuver, the maneuver described here is performed from the beginning by changing the speed and rudder angle. Especially in gusty conditions and the typical changes in wind direction between other boats, the correct interaction between speed and rudder position is important and requires practice.