Back in the early fifties, many yachtsmen were prejudiced against installing a gasoline or diesel engine on a sailing yacht. The engine on the yacht was considered a completely useless and even dangerous (from a fire point of view) cargo; argued that the motor tends to fail at the most critical moments. Most yacht captains called the union of a motor and a sail unnatural.
Now the situation has changed. It is difficult to find a cruising yachtsman who would deny the need to install an auxiliary engine. The vast majority of cruising yachts are equipped with motors, if not during construction, then during subsequent conversion.
A motor is, of course, necessary when the yacht has to enter the harbor along a narrow, winding channel, tacking against a headwind. People involuntarily remember him even when the sails hang helplessly, and you urgently need to return to the yacht club, going against a strong current. What about anchoring and unanchoring in narrow places, crossing canals and under bridges, sailing in calm weather? In all these cases, the motor not only makes maneuvering easier, but also saves time, which can then be used to go a hundred miles further or to explore the sights on the shore.
Tourists sailing on boats, on the contrary, often have a desire to set sails in order to use the fresh tailwind, save fuel, and simply take a break from the constant noise of the engine and vibration.
Below we discuss the features of combined motor-sailing vessels, combining the qualities of a sailing yacht and a boat. The two extreme poles of such combined vessels are a yacht with a low-power auxiliary engine and full sail rig, and a boat with a powerful engine and auxiliary sail (mainly to give the vessel stability on rough seas). The intermediate type vessels discussed in this article will be further referred to as motor sailboats.
Boat and yacht. It is easy to compare the main operational qualities of a motor boat and a sailing yacht in the form of a table. 1.
Table 1. Comparison of the main qualities of a sailing yacht and a boat
| Indicator | Sailing yacht | Boat |
|---|---|---|
| Characteristic | ||
| Travel speed | Unstable, depends on wind strength and yacht heading | Almost constant |
| Cruising range | Limited only by supplies of water and provisions | Limited by fuel reserves |
| Seaworthiness | High (unlimited for ocean-going yachts) | Limited (for most coastal boats - waves 3-5) |
| Draft | Large (2.1 m for a yacht with a vertical line length of 10 m) | Small (0.9 m for a boat with a vertical line length of 10 m) |
| Habitat conditions | Silence; move with roll | Increased noise and vibration of the housing |
| Minimum crew | 2-3 people on watch, 4-6 for emergency | 1-2 people on watch, 2 people. for emergency situations |
| Costs of organizing a trip | Food | Food - fuel |
When designing a motor sailboat, the goal is to achieve high speed, both under the engine and under sail, and maintain a shallow draft of the boat, which makes many shallow harbors and bays accessible. A sailing yacht must maintain high seaworthiness, efficiency and a long cruising range, as well as good conditions habitability.
In coastal cruising, a keel yacht (7-10 m long) without a motor shows an average speed during the transition from 3 to 5 knots. On a motor sailboat, you can get a stable average speed of 3-4 knots more, which allows you to travel an extra 50-80 miles per day; there is no need to tack in a weak headwind or wait out calm hours at sea. On the other hand, if the boat crew is often forced to refuse to go out to sea, especially in strong headwinds and large waves, a motor sailboat can safely go into a steep close-hauled sail under reefed sails.
How to best combine in one vessel positive qualities? Would it be right to install a powerful engine on a sailing yacht or a developed sailing rig on a boat?
It is known that a sailing ship can develop an acceptable speed if its sail area S (m²) is in a certain ratio with the displacement D (m³) and the wetted surface Ω (m²). These ratios should not be less than:
S 1/2 /D 1/3 = 3.8÷4.2; S/Ω = 2÷2.5,
Moreover, the first of them characterizes the performance of the yacht in strong winds, and the second - in weak winds.
The yacht will be able to carry such an optimal windage if it has good stability, which is ensured by a deeply submerged heavy false keel (its weight is 35-50% of the total displacement). Naturally, when sailing under a motor, such stability is not needed, and “transporting” a false keel will require an unproductive expenditure of engine power; In this case, the spar, sails and equipment become the same useless cargo.
To create sufficient resistance to drift, the yacht's hull must have a large area of lateral resistance (14-18% of the sail area). Therefore, the wetted surface of the yacht’s hull is larger than that of a boat of the same dimensions, and to achieve the same speed as the boat, more motor power will be required. The developed equipment and spars of the yacht increase air resistance, which also requires the expenditure of additional power to overcome. The contours of the yacht, designed for sailing at a relatively low speed and with a list, do not allow the motor to develop a higher speed, no matter how much its power is increased.
On the other hand, if you put the sailing rig of a yacht of the same size on the boat, the result is unlikely to be satisfactory. Due to the absence of a false keel and the high location of heavy loads (engine, fuel reserves, developed superstructures), the stability of the boat will be clearly insufficient for sailing and a reduction in the sail area will be required. It will not be possible to sail steeply into the wind, since the lateral resistance of its body is small. The contours of its underwater part are not designed for swimming with a roll and drift. A propeller with a large diameter and wide blades will greatly slow down sailing. And the hull of the boat itself, designed to move at a single and fairly high speed, will have more resistance than the hull of the yacht.
From what has been said, it is clear that a boat under sail will not be able to achieve the same tacking and sailing qualities as a yacht, just as a yacht with a powerful engine will not be able to achieve the speed of a boat of the same size and with an engine of the same power. When designing a motor sailboat, you need to find a compromise between these types of vessels and give preference to one or another individual qualities.
Features of the movement of displacement vessels at high speed. Every yachtsman certainly knows that when a yacht moves, waves form around its hull. The height and length of these waves increase as the speed of the yacht increases (Fig. 1), and their number, which fits the length of the vessel, decreases. Sometimes you can see how racing yachts, for example, class "P-5.5", sail on only one wave (the adjacent crests are located in the bow and stern, and the sole is near the midsection). This position means that the yacht has reached its maximum speed if its weight, contours and sail area do not allow it to go into planing mode. It seems that the ship is unable to climb the crest of the wave that it itself created. Nevertheless, light yachts - “Flying Dutchmen” and “stars” - in a fresh wind can overcome this barrier and plan, being only on one ridge, which is now located near the midsection. Similar phenomena are observed on boats with a gradual increase in their speed.
It is easy to see that the pattern of wave formation depends not only on the speed of travel, but also on the length of the vessel: the shorter the vessel, the lower the speed the wave barrier phenomenon is observed. Therefore, in shipbuilding, the speed of ships is usually characterized by relative speed, or Froude number,
where v is the speed of the vessel, m/sec; L - length along the waterline, m; g is the acceleration due to gravity, equal to 9.81 m/sec², √ is the square root.
This value characterizes, first of all, the intensity of wave formation near the hull at a given speed and the proportion of motor or sail power required to create these waves. For example, if a yacht is said to be sailing at a speed of Fr = 0.29, the boatbuilder knows that regardless of its length:
There are approximately two transverse bow waves along the length of the yacht;
The power required to create waves is about 50-60% of the total required engine power (the rest is spent on overcoming the friction of the hull skin on the water and the vortex resistance of the hull).
In the same way, when the Froude number Fr = 0.4÷0.5, the moment comes when the ship rides on two adjacent crests of the same wave, and the resistance to movement from wave formation reaches 90% of the total resistance of the hull. This speed represents the very barrier that can only be overcome by light planing yachts or boats with appropriate contours and engine power. In Fig. Figure 2 shows a graph of the dependence of the yacht's resistance (in the form of the towing power required to overcome it) on the relative speed. It can be seen that in the range Fr = 0.3÷0.5 the resistance increases sharply with the slightest increase in speed. That is why the power developed by the sails is usually only sufficient to achieve a certain speed v = 2.2÷2.4√L knots. (which corresponds to the relative speed Fr = 0.38÷0.39). It is obvious that increasing the speed of a yacht under motor beyond this limit without any change in contours and reduction in displacement will require an exorbitant increase in engine power, and consequently, an increase in its dimensions and weight, fuel reserves and displacement of the vessel as a whole.
Therefore, the speed of motor sailboats under power usually does not exceed the value v = 2.7√L. At this speed, you can get a satisfactory compromise between sailing performance and performance under the motor.
In table Table 2 shows the maximum and economic speed values for motor-sailing yachts of various lengths according to the waterline.
Table 2. Economic and maximum speeds of motor sailers
When a vessel moves at a speed above v = 2.7√L (Fr = 0.45), it forms, as already noted, a wave whose length exceeds the length of the vessel, and the apex is located near the amidships of the vessel. Such a wave causes the vessel to trim aft, which in turn leads to an increase in the stern wave and, ultimately, to sharp growth resistance of water to the movement of the vessel. In order to counteract trim, the stern of the vessel must have a wide transom and a flat bottom with gently sloping, almost horizontal buttocks. Thanks to this shape of the hull, a lifting force is created on the bottom, which levels the vessel, and with a further increase in power, squeezes it out of the water, putting it in planing mode.
However, such stern contours are unacceptable for a motor sailboat, since when sailing with a list (under sails), the large volume of the stern causes a trim to the bow; As a result, the hull and keel of the yacht occupy the wrong position (angle of attack) when tacking and do not allow sailing steeply to the wind, and the flow formed behind the stern slows down the movement of the yacht.
Thus, having considered the peculiarities of the movement of heavy displacement vessels, which are usually tourist boats and yachts, we can draw the following conclusions:
The maximum achievable speed under sail for yachts is v = 2.2÷2.4 √L knots;
The engine power for a motor-sailing yacht with good tacking qualities should not exceed the value necessary to develop a speed v = 2.7 √L knots;
If a boat is designed for high speed under power, it cannot be expected to have satisfactory tacking ability.
Types of motor sailboats. Depending on the speed developed under the motor and the role assigned to the sail or motor on a given vessel, all motor-sailing yachts can be divided into four main types.
I. Yachts with auxiliary engine. These are essentially ordinary cruising yachts on which the engine plays minor role and is installed solely to facilitate entry and exit from the harbor, passage along the fairway, mooring, etc. The motor is selected with minimal power, weight and dimensions. The speed under the motor in these cases does not exceed the value v = 1.8÷2.0 √L knot. (5-6 knots for most cruising yachts). The fuel reserve is also small, usually 20-30 hours. continuous engine operation, i.e. 100-200 miles.
To reduce resistance when moving under the motor, the propeller must have a minimum permissible diameter and narrow blades; Usually the propeller is placed in the window of the sternpost and rudder.
The power of the auxiliary engine to achieve the specified speed is usually 1.2÷2.0 liters. With. per 1 ton of yacht displacement. The weight of the motor does not exceed 3% of the displacement D, and the weight of the fuel reserves is 2% D. Therefore, installing the engine does not affect either the stability of the yacht or its tacking qualities. The weight of the false keel is maintained within 35-45% D.
II. with preference to sailing qualities. When designing ships of this type, the designer usually strives to combine good tacking qualities and sailing performance with a relatively high speed under the engine. One of these sailboats is shown in Fig. 3.
 |
Motor sailboats of this type differ from yachts with an auxiliary motor by a more powerful motor (4÷5.5 hp/t) and, therefore, higher speed stroke under the motor (2.2÷2.4√L knots), as well as an increased cruising range under the motor (up to 800-1000 miles for a yacht about 15 m long). Here the engine plays the same basic role as the sails, so greater attention is paid to performance under the engine. This type of yacht is often called “50/50” (i.e. 50% each of a yacht and a boat).
In Fig. Figure 4 shows a theoretical drawing of a motor sailboat, the main elements of which are indicated in table. 3 (for comparison, data on a type I yacht and a seaworthy boat with the same length according to the waterline are shown next to it).
Table 3. Comparison of vessels of the considered types
| Characteristic | Motor sailboat (type II) |
Yacht (type I) |
Boat |
|---|---|---|---|
| Maximum length, m | 14,35 | 16,0 | 11,0 |
| Waterline length, m | 10,97 | 10,97 | 10,25 |
| Maximum width, m | 4,10 | 3,70 | 3,2 |
| Draft, m | 1,52 | 2,26 | 0,85 |
| Displacement, t | 16,5 | 17,7 | 5,8 |
| False keel weight, t | 5,0 | 7,8 | - |
| Sail area, m² | 96,4 | 123 | - |
| Engine power, l. With. | 94 | 41 | 140 |
| 9,0 | 6,5 | 16,2 | |
| Cruising range, miles | 700 | 150 | 500 |
| 5,7 | 2,3 | 24,1 |
The contours of this motor sailboat are characterized by a shallow draft, short overhangs, a straight keel line, and a wider transom stern than usual on yachts. The camber of the frames in the bow and the outline of the deck line are typical for motor yachts. The waterlines at the bow have a sharper entry angle (point), and the buttocks at the stern rise at a smaller angle to the waterline than on a sailing yacht.
Due to the installation of a powerful diesel engine, the weight of the false keel was reduced to 30%D. The propeller is located in a large sternpost window, behind the vertical star post and has a significant diameter. This placement of the propeller helps to increase its efficiency and more fully utilize the power. Naturally, the reduced stability, as well as the trimmed underwater part of the DP, does not allow for full sail. On larger yachts of this type, a centerboard is often installed to improve tacking qualities. The option with a centerboard is a good compromise between the sail and the motor: when sailing under the motor, the centerboard can be removed and thereby reduce the wetted surface of the hull.
To reduce air resistance when sailing, the volume of superstructures is sought to be reduced to a minimum.
Among the relationships characteristic of this type of vessel, another parameter can be noted:
S 1/2 /D 1/3 = 3.5÷3.9,
while for type I yachts this value is larger (3.8÷4.4).
III. Motor-sailing yachts with preference to boat qualities. In this case, the speed under the motor plays a primary role and reaches v = 2.7÷2.9 √L knot. As already noted, at this speed the vessel gets a strong trim aft, so a wide transom stern with flat buttock lines is preferable. The required engine power increases to 6.5÷9 hp/t, which forces the weight of the false keel to be reduced to 15-25% D.
The draft is taken such as to accommodate a propeller of the required diameter (usually T=11÷13% L).
Since the shape of the hull still turns out to be unsuitable for steep tacking, they abandon the installation of a centerboard and increase the volume of superstructures. The sail area is relatively small:
S 1/2 /D 1/3 = 2.8÷3.4.
Sails are intended mainly for sailing full courses in fresh winds and stabilizing the movement of the yacht on rough seas.
An example of a vessel of the type under consideration is the Serch (Fig. 5 and 6), a seaworthy yacht designed for long voyages. It has good performance both under motor and under sail. The main elements of the yacht are given in table. 4 (next for comparison are the data of the yacht with the Khortytsya auxiliary motor).
The yacht's hull, in terms of its contours, approaches the shape of a seaworthy boat (straight keel line, short overhangs, high freeboard, stern with a wide transom partially submerged in the water). The propeller with a diameter of 850 mm is located behind the sternpost in a large window.
“Serch” carries half the sail capacity of a yacht with an auxiliary motor. The sails are relatively wide, with a low center of sail, designed for full course sailing.
Table 4. Comparison of two representative vessels
| Characteristic | "Serch" | "Khortitsa" |
|---|---|---|
| Maximum length, m | 14,9 | 18 |
| Waterline length, m | 13,0 | 13,3 |
| Maximum width, m | 4,27 | 4,0 |
| Draft, m | 1,53 | 2,2 |
| Displacement, t | 21,5 | 24,5 |
| False keel weight, t | 1,5 | 7,8 |
| Sail area, m² | 69 | 150 |
| Engine power, l. With. | 140 | 62 |
| Travel speed under engine, knots. | 10 | 7 |
| Cruising range, miles | about 900 | 100 |
| Specific engine power, l. s./t | 6,5 | 2,5 |
| S 1/2 /D 1/3 | 3,18 | 4,22 |
IV. Boats with auxiliary sails. If the boat is intended for sailing in the sea or on a large lake, it makes sense to install small-area sails on it, first of all, to improve seaworthiness on a wave (primarily to increase stability on course, soften pitching and give the ability to drift). In a fresh wind, the boat can sail (without a motor) at low speed into the backstay or even tack, powered by the engine. The sail area is assumed to be about 5 m²/t for boats with a displacement of up to 5 tons; 4÷3 m²/t for boats with a displacement of 5-10 tons and 2.5÷3 m²/t for large vessels.
As an example, let’s take the seaworthy boat “Passagemaker” (Fig. 7 and 8), designed for long-distance sea and ocean voyages. The engine power is small - only 40 hp. With. (1.6 hp/t); the speed is correspondingly low - 7.5 knots (2√L), but the fuel reserve is 5.5 tons (22% D), which provides a huge cruising range - 2400 miles. Only 2.3 kg of fuel is consumed per mile traveled.
The greatest length is 15.3, and along the vertical line - 14.0 m; beam 4.9 m, draft 1.53 m, displacement of the Passagemaker 25 tons, and the weight of the false keel is only 3.3 tons (13% D). The sail area is about 50 m².
The contours of its hull are typical for motor seaworthy yachts with low speed (sharp waterlines in the bow, a bottom with a large deadrise at the transom, a straight keel line). High freeboard and extensive superstructures are also typical. This theoretical drawing can be taken as a basis for designing a motor sailboat of shorter length (9-10 m).
It should be noted that yachts of this type are often equipped with low bilge keels, which significantly reduce drift under sail and, in addition, serve as effective roll dampers.
D. A. Kurbatov, 1966
Water speed record
For true connoisseurs of their time, the choice of yacht will focus exclusively on the highest quality, best and fastest option. Therefore, we can assume that there will someday be buyers for the fast yacht put up for sale, despite its cost of $25 million. After all, this particular yacht is the fastest yacht in the world! Today there is a very wide variety of beautiful and super-fast ships, but this model, built by WALLY, was able to prove its fame by setting a world speed record.
Yacht equipment
The ultra-modern vessel captivates with its minimalist design and sweeping appearance. Built in 2003, the Wally Power 118 reaches speeds of up to 60 maritime knots(111 km/h), which are inaccessible to most existing yachts. The yacht is equipped with three helicopter (gas) turbines, where their total power reaches 16,800 hp. The yacht's pointed stern cuts through waves at speeds of over 40 knots, even when sailing in the roughest waters.
Complete sound insulation
The hull of this vessel is designed so that even when moving at the highest speeds, vibrations and sounds cannot penetrate inside, and this allows vacationers to feel comfortable. The interior design of the vessel was designed by Carl Pickering, a famous designer from Lazzarini & Pickering. Karl focused on functionality and modernity, so the design turned out to be a bit of a mixed style: hi-tech, minimalism and loft. Sharp corners, metal, wood, rectangular windows and light shades of upholstery material - all this significantly helped to complement the technological and comfortable look of the yacht.
Amenities of the “yacht of the future”
The yacht is able to take on board from 6 to 12 passengers and 6 crew members, with a yacht length of 36 meters and a width of 9 meters at the base.
Wally Power 118 has already received the nickname “yacht of the future” and also won the top prize at the MYDA (Millennium Yacht Design Award). The star ship managed to appear in one of the most popular films of recent years.
The season of vacations, travel and adventure is just around the corner. Lovers of water recreation will find the sea or ocean, resorts and beaches, large marinas and small marinas. Some will prefer the Croisette and spend time with a light beach cocktail, others will choose scuba diving and the endlessly amazing underwater world, and someone will give free rein to their inner to the sea wolf(or she-wolf) and go on a free, personal, independent journey on a charter yacht under the hot Adriatic sun.
But how to decide on the choice of yacht? Do we want to sail towards the horizon, catching the tailwind with our sails raised, or will we rush through the waves on a boat with a powerful diesel engine? The choice of yacht for charter depends entirely on our preferences and wishes. However, there are only three options: sailing yachts, which are perfect for family and active recreation, catamarans - double-hulled, relatively fast, comfortable and safe vessels, and motor yachts - for lovers of speed on the water and luxury. So which yacht should you choose?
Sailing or motor?
The main difference between sailing and motor yachts is speed. Modern motor yachts with powerful diesel engines can reach speeds from 10 to 60 knots, i.e. from 18.5 to 111 km/h. In the open sea on a large wave, especially if the wave is from the side or from the stern, the motor yacht does not hold its course well, swaying and causing roll. In this case, powerful engines come to the rescue, helping to cope with the force of the waves. The more powerful the engines, the greater the stability of the vessel, and the faster you can avoid possible bad weather.
However, speed is paid for by increased fuel consumption. For example, two 650 hp diesel engines, depending on the operating mode, can consume more than 100 liters of fuel per hour. Real example: motor yacht Princess 52, equipped with two 710 hp engines, sailing from Split to Dubrovnik (seaside towns in Croatia) with average speed 20 knots (37 km/h), will consume approximately €1,500 worth of fuel. In practice, this means that such a yacht will have to refuel at a gas station more often, which is usually extremely difficult at the height of the season due to queues. You will often have to wait in line for more than an hour. Therefore, if you rent a motor yacht or a large boat, you should definitely pay attention to the average fuel consumption, since the cost of fuel can get dangerously close to the cost of renting a boat.
Sailing yachts
The speeds that sailing yachts are capable of developing are determined by the conditions of their purpose. Cruising sailing yachts are designed primarily to provide maximum comfort for the crew. Due to the relatively small surface area of the sails, a classic cruising yacht sails at speeds of 5 to 10 knots (9.3 to 18.5 km/h). This means that in six hours of active sailing, the yacht can cover approximately 50 nautical miles, which should always be taken into account when planning a route.
This category of vessels is designated special philosophy life at sea: speed is not important, but contact with the sea, wind and nature is important. Yachtsmen love the Adriatic not only because of the clean sea. The Croatian part of the Adriatic coast has many islands and highly indented coastline with a large number of sheltered bays and harbors with comfortable marinas for safe anchorage of yachts.
Short distances between anchorages allow you to have enough time in one day to enjoy sailing, swim in some picturesque bay and have the opportunity to stop overnight in a place you like. And this is undoubtedly important. Sailing in a light wind at a speed of 2-3 knots, without engine noise and exhaust smells, enjoying the sun and sea - what could be better! The engines that power sailing yachts and catamarans with a power from 30 to 100 kilowatts are designed for maneuvers during moorings, sailing during complete calm or for avoiding stormy weather.
When sailing on a cruising sailing yacht, fuel consumption and consumption are usually quite insignificant. On average it is about 100-120 euros per week. Fuel consumption, of course, may fluctuate slightly depending on sailing conditions and your preferences, the main thing is that the more often the boat is sailed, the lower the fuel consumption. With a full fill of about 100-200 liters (depending on the model of the vessel), you can travel for a whole week.
In practice, this means that you rent a sailing yacht, leave with a fully filled fuel tank, and only pay for the fuel consumed at the end of the seven-day voyage. If the wind blows favorably during the voyage, and you sail all week, then the engine will only be needed for maneuvers in ports and for recharging batteries. As you know, many yachtsmen have traveled long distances, traveling around the world even on relatively small sailing yachts, which is impossible to do on a large motor yacht without constant refueling.
Continuation - in the publication from
Sunseeker yacht
When a motor yacht glides across the sea, the impression can be conveyed in one word - breathtaking. And the first thing that catches your eye is the beauty and grace of a woman.
IN lately in many countries, motor and sailing yachts have become more accessible not only to a group of fairly wealthy people, but also relatively to a wide circle representatives of the so-called “middle class”. Mass creation of relatively inexpensive plastic hulls and other equipment for small yachts 8-12 m long, as well as the ability to take yachts for rent () allowed millions of people to join amateur water sports and sea travel.
But we will limit ourselves to studying the development of the fleet of motor yachts. Steadily growing demand in recent decades has generated increased production small vessels both in states where the creation of pleasure yachts has long been traditional, and in countries that are new to this area.
So, in Italy alone, more than 60 companies are engaged in the construction of motor yachts. Today, the shipyards' portfolios contain about 500 projects of yachts up to 32 m in length, and 41 of them are more than 25 m. The lion's share of these products is exported. A considerable number of medium-tonnage motor yachts are created in shipyards in the USA, the Netherlands, France, Sweden, Finland, Norway and Australia. The development of yacht building in Japan, Spain, Turkey, Egypt and the UAE is also gaining momentum. Along with this, there has been a steady increase in the creation of larger and more expensive motor yachts, the cost of which ranges from 7 to 100 million dollars. Naturally, the purchase of such toys is affordable only for rich people, for whom, as a rule, a yacht becomes a symbol of prestige, a place for business meetings, and a way of profitable investment. material resources- after all, with proper care, and with growing demand, a comfortable yacht can be sold profitably even after 5-8 years of use. In addition, the yacht can be rented through brokerage organizations to partially cover ongoing operating costs.
IN recent years There is a real boom in the choice to create ever larger motor yachts. Of the $6 billion valued today's global powerboat market, the majority comes from yachts more than 45 m long.
Among those under construction, there are about a dozen yachts ranging from 70 to 138 m in length. Such superyachts are designed for 14-28 guests in luxury conditions. There is also a growing fashion for the construction of ocean-going motor yachts 70-80 m long in the Explorer class. These research yachts have a decent cruising range of up to 5 thousand miles and can carry crew boats and even a helicopter on board. As a rule, they are useful not only for long-distance cruising, but also for research work in various areas of the World Ocean.
motor yacht "Lurssen "Queen"
In the production of large motor yachts, the palm is occupied by shipyards such as Luerssen and Abeking&Rasmussen (Germany), the Feadship group (Netherlands), Benetti, Codecasa and Rodriques (Italy), Oceanco ( South Africa), Oceanfast (Australia) and Palmer Johnson (USA). However, modern ones are not characterized only by size. The persistent modernization of their technical characteristics continues. Lightweight and durable composite materials are being increasingly used for the production of hulls, the power and efficiency of installed power plants is growing, modern propulsors such as partially submerged propellers and are being actively introduced, air conditioning and domestic water supply systems are being improved, consumer qualities and aesthetic properties of room decoration are growing.
speed or comfort of motor yachts?
What about the speed of yachts? This value can vary within very wide limits - from 10 to 80 knots - depending on the purpose, method of operation and size of the yachts, and, of course, on the preferences of the owners. Among small sports class yachts with a length of 10-15 m, especially popular in the USA and Italy, there are many vessels capable of reaching speeds of up to 40 knots, and sometimes much higher. Modern advances in the field of hydraulic engineering are capable of providing such speeds on yachts mass-produced for private use. As a rule, motor yachts of this type are single-hull boats with planing contours and a system of longitudinal and transverse steps, with an open cockpit and power plants that include either two or three powerful outboard motors or Z-shaped rudder propellers.
On such a high-speed yacht it’s nice to rush along the resort coast, delighting spectators, but you can also compete in speed by participating in informal competitions. These ships are usually popular among the wealthiest young people.
However, it is difficult to travel along a long route on high-speed yachts - their seaworthiness and cruising range are limited. IN best case scenario, they are equipped with a small cabin, a bathroom and a mini-galley in the bow area below deck. In the USA alone there are more than 20 companies producing yachts this type. Among them we can mention “ Fountain», « Baja Marine», « Hustler», « NorTech», « Donzi Marine" And " Hallet Boats».
motor yacht "Baja Marine"
Among large yachts with a length of 18-25 m and much more comfortable ones with two or three double cabins with individual bathrooms, a cozy common salon and a galley, there is also a subclass of ships capable of reaching speeds of up to 50 knots. Their bodies, as a rule, are made of composite materials, have a lightweight design, and their power plants are twin-shaft with high-speed diesel engines. The owners of such motor yachts are dynamic people who value time. They are impressed by the opportunity with a group of friends to quickly get to a secluded bay or deserted island, located several hundred miles from the quay wall, have a barbecue and swim there, and return home in the evening. Companies such as Sunseeker and Princess (Great Britain), as well as Riva, FIPA Group, Pershing, Alfamarine (Italy) have made particular progress in the construction of yachts of this class.
And yet, the vast majority of modern motor yachts up to 25 m in length have a speed that rarely exceeds 20-25 knots. They are naturally cheaper and more economical to operate. They are used for short-term, fishing or one-day ones. Shipyards in the Netherlands, Germany, Taiwan, Italy and the USA are engaged in mass production of such yachts.
motor yacht “Riva 92”
motor yacht “Pershing 72”
As for “mega-class” motor yachts, a fairly predictable situation has developed here, in which the most numerous fleet of the lowest size subgroup, and these are yachts with a length of 28 to 36 m, has dozens of units developing maximum speeds of 40-48 knots. Most of all, high-speed vessels of this type include yachts with a dynamic silhouette of the “semi-open” type, fashionable for the southern seas, with an opening salon roof. Among the modern models of such yachts, we can mention the 46-knot yacht “ Predator 95» companies « Sunseeker" or a 40-knot yacht " Mangusta 108» Overmarine company.
motor yacht "Mangusta 108"
motor yacht “Sunseeker Predator 95”
The clients of expensive motor yachts over 40 m in length have a very atypical approach to high speed. The clients of these vessels are, naturally, very respectable people who want to relax in the most comfortable conditions. However, the rich also have their own whims, which can only be satisfied thanks to the latest achievements of technological progress and, naturally, generous financing of projects.
Technical innovations developed at, naturally, interested fans of high speeds, who were able to buy themselves as expensive yachts.
Here are some of the most striking examples. Once, in 1992, the restless billionaire John Staluppi ordered the yacht Moonraker from the Norwegian shipyard Ulstein Eikefjord, which reached a speed of 66.7 knots during sea trials. This record lasted for about 8 years. A significant reduction in the weight of the hull was achieved through the use of composite materials, and the power plant included a gas turbine powered by a medium water jet, while the onboard controlled water jet propulsors were driven by diesel engines.
motor yacht “Fortuna”
In 2000, by order of the King of Spain Juan Carlos, the English designer Donald Blount designed a 41-meter yacht with a combined yacht, designed to achieve a speed of at least 65 knots. The design of the vessel was finalized by the designers of the Spanish shipyard “Izar” in San Fernando, which carried out production yachts, called "Fortuna".
The contoured planing hull has a double chine and is equipped with transom plates to adjust trim when overcoming resistance. In order to minimize weight, the hull is made of aluminum alloy, and the superstructure is made of ultra-light composite materials. The interior of the motor yacht looks very modest - all for the sake of lightening the weight.
A three-shaft gas turbine unit with water-jet propulsion from the KaMeWa company provides the yacht with a speed of about 68 knots. Now Fortuna is the private yacht of the King of Spain, he can personally manage it at sea. For the safety of the monarch and his guests, the walls of the superstructures and all glazing are made of bulletproof materials.
motor yacht Wally 118
Another yacht for the title " the fastest yacht in the world"was built in Italy in 2009 at the Intermarine shipyard according to the design of the Wally company. The 36 m long motor yacht Wally 118 can reach speeds of over 70 knots with a total power plant of 17,000 hp. Designed under the leadership of Luca Bassani, the yacht has a completely atypical “militarized” silhouette. The avant-garde interiors are also original. Tinted glass and sliding ceiling structures are widely used. The cost of this yacht is estimated at 17.3 million dollars.
Designer Frank Mulder once said: “ People have always loved speed. All that is needed to create high-speed yachts is technological capabilities and money..." Note that they are very large. Indeed, to increase the speed of, for example, a 40-meter yacht from 20 to 40 knots, the cost of the propulsion system increases approximately four times, and the total cost of the yacht - by more than a third.
KEEL
It has long been observed that yachts with high side drag sail better than those with equal frontal and side drag. The designers were given the task of increasing the lateral resistance without changing the frontal resistance. Kiel turned out to be a very successful decision.
Over the years, shipbuilders have experimented with its shape and size in an effort to achieve maximum efficiency. It turned out that a long and narrow keel works best, and this is due to the fact that its main function is to create lift when moving in a stream of water. The keel is symmetrical, so it is capable of creating lift only if the direction of movement does not exactly coincide with the longitudinal axis of the yacht, i.e. the ship is moving with some lateral drift. It is thanks to lateral drift that the keel crosses the flow at an angle called the angle of attack. The consequence of this is an increase in the flow path on the “upper”, windward side. Due to this, in accordance with the wing theory, on the windward side there is an increase in flow speed and a decrease in pressure. On the leeward side of the keel there is a decrease in flow velocity and, accordingly, an increase in pressure.
A long and narrow wing works much more efficiently than a wide and short one. This statement is true for both the sail and the keel, which, in fact, are wings, only located vertically. The explanation for this phenomenon is the vortices that form at the end of the wing and create additional resistance to movement. With the same area, a longer and narrower wing has more lift, and the cost of vortex formations is less.
Due to the higher density of water compared to air, the role of the keel shape is especially important. With the same hydrodynamic properties, a narrow and long keel can have a much smaller wetted surface area, and therefore less resistance. The most striking example of the application of this principle is the America's Cup contender yachts, but for an ordinary pleasure or cruise yacht, such a keel can become a serious problem due to the depth limit in their sailing areas (Fig. 3).
FORCES OF RESISTANCE
There is a rather complex set of forces that impede the movement of the yacht. Water resistance to body movement. Since water molecules are attracted to each other and to the surface of the body (van der Waals forces), any movement is accompanied by the expenditure of energy to overcome these forces. The layer of water at the very surface of the hull is called the boundary layer; its displacement speed is maximum. As you move away from the surface of the body, the speed of displacement of the water layers decreases, i.e. there is a speed gradient. The energy consumption to overcome water resistance is proportional to the area of the wetted surface and the speed of movement.
The frictional forces of a liquid are fundamentally different from the frictional forces between solid bodies. To reduce friction between the surfaces of solids, they can be polished and lubricated. This will reduce the protrusions on the surface and replace contact between solid parts with contact with lubricant molecules. In principle, lubrication of the housing does not make sense, since it moves in a liquid medium. Polishing the body also does not eliminate the need to separate water molecules. Conclusion: the most effective way to reduce friction is to reduce the wetted surface area.
Formation of turbulence is a well-known flow phenomenon. When moving at low speed, there are no disturbances or turbulence in the flow, it is smooth, i.e. laminar. As the flow speed increases, displacements of molecules relative to each other appear in it, uniformity disappears, and turbulence appears. When a critical level is reached, the number of vortices increases sharply, and the flow stalls. As a result, the pressure difference on different sides of the wing decreases, which leads to the disappearance of lift. At the end of the 19th century, the English engineer Osborne Reynolds proposed a formula, the result of which is a dimensionless quantity characterizing the moment of transition of a laminar flow to a turbulent one. It turned out that at a typical speed for yachts of about 5 knots (2.4 m/s), turbulence begins for any yacht longer than half a meter.
Typically, turbulence increases the overall drag by four to five times! An uneven, rough surface leads to the fact that turbulence occurs earlier and is more pronounced. Therefore, for high-speed yachts it is very important that the hull surface is smooth. It is considered sufficient that the roughness of the body does not exceed 0.05 mm. Usually such a surface can be achieved if the sanded surface is covered with two layers of good paint.
For a wind speed of 5 m/s, which can be called typical, turbulence occurs when the sail width is more than 3 meters. A sail stall is also very dangerous. If turbulence is formed when the air flow moves along the surface of the sail, the pressure difference on different sides of the sail disappears, and along with it the lifting force (thrust) of the sail disappears.
End vortices, are another factor that increases resistance. They arise at the end of the wing, and on a yacht at the top of the sail or the bottom of the keel. Both air and water, moving along the sail or keel, will tend to equalize the pressure on opposite sides of the sail or keel, moving from an area of high pressure to an area of low pressure. Figure 4 shows a diagram of such movement for the keel. On the one hand, the flow angle goes slightly up, on the other, slightly down. As a result of the fact that at the trailing edge of the keel or sail, the flows from both sides meet at a certain angle, vortices are formed, which intensify as they approach the top, and here a tip vortex is formed. The tip vortex leads to a redistribution of lift along the wing span, reduces its effective area and aspect ratio, and reduces its dynamic quality.
In Fig. 5 you can clearly see how vortices are formed at the tops of the masts during the race, which took place in thick fog, and in Figure 6 the same vortices are visible on the wings of the aircraft.
The wider the keel, the more energy is spent on vortex resistance. By making the keel narrow and long, designers increase the lift-vortex drag ratio. The same thing happens with narrow and high sails, especially when moving on sharp courses. Long and narrow wings for gliders are made for the same reason. In order to reduce the braking associated with the formation of end vortices on the keel, additional horizontal wings are made. In aviation, such a device is called a winglet (Figure 7); it helps to achieve optimal distribution of lift over the wing area. Wing theory, to minimize induced drag, recommends the use of an elliptical or tapered trailing tip, such as a bulb at the end of the fin.
The keel of modern, non-racing yachts is a compromise between a comfortable short and wide keel and a very efficient, with high hydrodynamic qualities narrow and long, but difficult to use outside the racing distance. Another type of resistance arises as a result water flow deviations while the ship is moving. First of all, it depends on the geometry of the body. It is clear that a narrow body has less resistance than a wide one. Any boat is a compromise between minimum drag and providing the necessary space for passengers and cargo. For centuries, shipbuilders have searched for the ideal shape for a given volume, seeking to ensure minimal hull resistance. Even Isaac Newton dealt with this issue. The conclusion he came to is best form for the body, an ellipsoid of revolution with a truncated cone attached to the front part.
Spatial computer modeling and hydrodynamic tests have shown that the optimal hull is one that smoothly widens from the bow and remains quite wide at the stern. To ensure a smooth flow at the stern, many designers narrow and raise the rear part of the hull. If the flow at the stern is not smooth, laminar, the eddies will create significant resistance to movement.
BODY SPEED.
When moving, the hull creates a wave, the length and speed of which depends on the speed of the yacht. As soon as movement begins, several short waves are formed on the water, which move along the hull. As the speed increases, the length of these waves increases, and the number along the length of the body becomes smaller (Fig. 8a). At some stage the yacht reaches a speed at which the wavelength becomes equal to length yacht hull, i.e. a ridge at the bow, a depression in the middle of the hull and a second ridge at the stern level (Fig. 8b).
With a further increase in the speed of the yacht, the wavelength also increases, therefore, the second crest will move further and further back, behind the stern. As the second ridge moves back, the stern drops into the depression between the ridges. If you look at the hull from the side, it turns out that the bow is raised up, the stern is down, and the yacht must constantly climb the wave, while the resistance to movement increases dramatically (Fig. 8c).
This type of resistance is called wave resistance. Of course, for a motorboat with a powerful engine and a flat bottom, the speed at which the stern reaches the middle (trough) of the wave is not the limit. By adding speed to the engine of a motor yacht, you can increase the speed and switch from displacement mode to planing mode. However, most sailing yachts do not have this capability, and in most cases the hull geometry does not provide for planing mode. Therefore, for most yachts of a traditional shape, wave resistance turns out to be an insurmountable obstacle. This applies not only to sailing yachts, but to barges, tankers, large passenger ships, in short, everyone who is not able to plan.
The speed at which the wavelength becomes equal to the length of the hull at the waterline is called the speed of that hull. A further increase in speed is possible in principle, but without switching to planing mode, this is associated with very high energy costs. In practice, it is very rarely possible to accelerate a yacht to a speed one and a half times higher than the hull speed.
The hull speed is determined by the formula - v=1.34√L,
where v is the speed in knots, L is the length in feet. So for a yacht with a waterline length of 20 feet (6 m), the maximum speed will be 6 knots. For a large cruising yacht with a 40 ft (12 m) waterline, the speed will be about 8.5 knots. For a 300 foot warship, the hull speed is 23 knots.
Comparing all the factors that impede the movement of the yacht, we will find that friction accounts for more than a third of the total resistance, another third is due to the formation of waves, about 20 percent is due to the formation of vortices at the surface of the hull, 10 percent is the resistance associated with the formation of vortices at the trailing and lower edges keel. The rest is accounted for by the resistance of the surface part (resistance of the spar, air turbulence formed by the sail, etc.). Of course, the ratio of the listed components can vary significantly depending on the shape of the hull, the conditions in which the yacht is moving, its course relative to the wind, etc.
To summarize, we can formulate the following rules: the yacht that moves faster is the one that has a longer and narrower hull, a larger sail area and a smaller wetted surface area. Of course, such simple rules can lead to designers making long boats with cabins that do not provide even minimal comfort. But any design decision is a compromise between mutually exclusive wishes. For jibe movement, it is desirable to have wide square sails that will easily capture the wind and a keel of minimal size. In contrast, tall, narrow sails work better for upwind sailing because they provide the best balance between lift and vortex losses. The keel on sharp courses should be long and narrow to create maximum lateral resistance with a minimum wetted surface. But such a keel is very inconvenient outside the race track or simply in shallow water. A short keel with a bulb or horizontal wings is an excellent compromise satisfying most yachtsmen.
The Physics of Sailing Explained: An Introduction