As a rule, people who decide to bind the raceactivities (be it a hobby or a profession) with reservoirs such as rivers or lakes, sooner or later face the problem of choosing a boat and the type of propulsion for it. Motor water cannon or still screw? Each has its pros and cons. How to choose the right thing to pay attention to? And is it worth making a choice between a water jet and a classic open screw motor?
Water jet propulsion
The water jet is the engine that provides the movement of the vessel with the help of the force created by the release of a water jet.
The propeller consists of a propeller with a shaft (impeller), a water jet tube, a rectifier and a steering gear.
Принцип работы заключается в поступлении воды through the impeller into the water intake compartment, and then the liquid is ejected through a cone-shaped tube, the outlet of which is smaller in diameter than the inlet. This creates a jet that provides movement of the motor boat. With the help of the steering device, the direction of movement of the jet is changed by turning the propeller in the horizontal plane, which ensures the vessel turns, and the overlap of the outlet orifice creates a reverse flow, providing the boat with reverse gear.
К выбору водомётов обычно склоняются люди, which often have to overcome littered or porphyry reservoirs. Under normal conditions, a conventional screw motor runs the risk of becoming unusable due to the high risk of winding mud on the screw in shallow water or the usual ingress of large debris. In such situations, it is precisely water jets that provide high speed, maneuverability and safety.
Не стоит ограничиваться мнениями участников various forums. After all, to make a complete picture allows not every review. The water cannon is not only a rather complicated structure, it can not be suitable for any model of the vessel. If the beginner is satisfied with the very idea of using a vessel with a water-jet propulsion unit, it is necessary to dwell on the finished version of a vessel with a water-jet in the original configuration. Moreover, it is desirable to choose a manufacturer engaged in the production of these propulsion for a long time.
Advantages and disadvantages
Water jet device especially that allthe most important moving parts are “hidden” inside the case. If the boat is stranded, the bottom of the boat is touched by the hull of the vessel. This design feature allows you to protect parts from damage, which is not the case with outboard motors with a “bare” screw. Water jet propulsion are not afraid of meeting with underwater debris.
When a motorboat moves through shallow watera depth approximately equal to the landing of the hull (about 20 centimeters), the water cannon makes it possible to overcome littered areas, as well as places with obstacles protruding from the water, thanks to its maneuverability.
If you hit a barrier at a depth of about 30centimeters, the blow will take over the bottom of the boat, and not the water jet, since the propulsion unit has no protruding parts, which is not to say about the outboard engine, where the blades of the propeller take the blow.
Sometimes water-jet propulsion devices are also used on pleasure craft due to the soft work of powertrain (transmission) and the absence of vibration.
The advantages also include the lack ofadditional resistance to water, characteristic of engines with an open propeller (propeller blades and create additional resistance). In addition, high rates of inertia, more convenient handling at high speed (both in the forward course and in the rear) are distinguished. The low noise range is also of considerable importance: a suspended water jet works noticeably quieter than a motor with a propeller.
Nevertheless, it should be noted negativeside: when moving through shallow water there is a big risk that stones, sand and debris will be pulled into the engine from the bottom, because the water cannon works on the principle of a pump pump. This can lead to damage to the impeller, failure of the cooling system and incorrect operation of the drainage nozzle.
Another negative side is friction.It is due to the high velocity of the water inside the pipe. Do not forget about the cost of installation. Water-jet boat engines are about twice as expensive as conventional open-head outboard motors. Because of this, boats with a water jet in the kit significantly add to their value and are perceived by customers as a whim or an unaffordable luxury.
Непривычным для поклонников классических винтовых motors is also a water management system. The problem is due to the fact that the classic propulsion unit with an open propeller has a single-lever control system. Water jet propulsion also have a multi-lever reversing-steering device. Some manufacturers manage to produce boats with built-in water cannons with single-lever control system. On the one hand, it helps to master the water-jet; on the other hand, it entails troubles rather than benefits:
- First, the newbie has the wrongrepresentation of the work of water jet propulsion. This is due to the lack of such a gearbox, which allows to translate the gearshift lever to the neutral position. The gearbox can either turn on the clutch or turn it off. The water jet propulsion is gaining speed smoothly when turned on, an instantaneous response in the form of a jerk from the spot should not be expected.
- Secondly, for a better understanding of the principles of workwater jet, it is recommended to take the appropriate course. The whole trick of managing a water jet propulsion is the need to use the gas lever (to increase the speed of movement) only in an open reservoir. When moving along the rivulet river, it is better not to do so.
- The third important minus, peculiar to anytype of water transport - overgrowing. This problem is especially acute with a water jet, since all moving parts are inside. With constant use of the propeller problems arise. However, if the boat is not used for a long time, the insides overgrow. In particular, fouling of the viscera of the drainage system leads to a decrease in the speed of movement up to 10%. The problem is solved by disassembling the water cannon and cleaning manually, but if the motorboat has been inactive for a very long time, you will have to contact the workshop and look for suitable spare parts for boat engines. The use of special coloring composition will allow to solve this problem, but not for long: the constant movement of water will quickly wash away this paint.
Water cannon is safe!
Of course, the safety of the jet engine -main positive trait. Since the impeller is inside, the water cannon does not pose a danger to a person in the water. Such devices are used on jet skis and boats when towing water skiers and surfers.
Features of the water jet propulsionallow the motorboat to carry out turns practically on the place thanks to the reversive-steering device (RRU), providing the change of direction (reverse) of the output stream.
Water jet parts are readily available, and repairs are notcauses particular difficulties. If the engine of the water-maker fails, you should use the services of any auto repair shop, where it will be easily repaired or replaced with a new one. Everything will depend on the degree of damage. It may be necessary to refine the mounting, cooling and exhaust system in the case of replacement.
Water-jet propulsion has a number of nuances, owhich should not be forgotten. One of those: should be maneuvered at high speeds, you should not dump those before the end of the maneuver, be it turning, turning or reverse.
Like outboard, water jetis at risk of winding algae on the impeller, which, in turn, can jam. To prevent damage to the engine in case of winding algae on the shaft, a special key is provided that can be cut. It is also easy to get rid of algae just by opening the flap. Provides protection from hitting stones - grate.
How to choose a water cannon
Conventional outboard motors with open rowingpropellers have a coefficient of efficiency (Efficiency) of 0.65–0.75 when driving at moderate speeds. For a water-jet, the efficiency is approximately 0.55 at a speed of 40–55 km / h. With an increase in speed to 100 km / h, it is already 0.60–0.65. Competent design of all elements of water jet propulsion gives an efficiency of about 0.70. In this case, it is necessary to consider not only the water jet, but also the acceleration of the boat with the installed water jet structure.
It is recommended to examine a number of rules that allowWisely choose a water cannon, the main focus of which concerns the design and manufacturing technology. It should be noted that it is necessary to pay attention to the shape of the nozzle. Drainage should have a round or ellipsoidal cross-section. Less desirable options are square drain pipes and rectangular shapes with rounded corners.
An important aspect is the angle of inclination of the axiswater intake. It is necessary to choose according to the principle “the speed is higher - the slope is less”. Water-jet boats develop a speed of 55–65 km / h, which is achieved with an angle of 35–39 degrees. To achieve higher speeds, the angle should be reduced to 25 degrees. The angle of inclination of the axis of the propeller shaft is selected in the range from zero to five degrees.
Installation
Install the water jet engine onlight high-speed vessels, called “gliding”. Such boats are designed for speeds above 60 km / h. However, sometimes the water cannon is installed on medium motor boats with a bottom tilt angle (deadrise) from 10 to 30 degrees.
При установке следует учитывать и массу propulsion, because the water is constantly inside adds a significant share of the weight of the vessel. Therefore, doing the calculations of "shipiness" of the vessel, you should take into account this important nuance. But if you look at the whole picture, the mounted water jet on the boat is a more compact option than a motor with an angled column. The added weight is easily compensated by the absence of a gearbox, which is replaced by a reversing-steering mechanism. It is worth noting that experts recommend installing a special coupler between the engine and the water cannon. This ensures the isolated functioning of the motor, regardless of the mode of operation of the water jet propulsion unit.
Relevance
Неподдельный интерес к водомётным движителям со parties to commercial organizations emerged relatively recently. Thanks to the experiments of shipbuilding companies in the form of installing water cannons on high-speed sea ferries, military and commercial ships, this type of ship propulsion has gained popularity.
Successful operating experience showed a lot of hidden merits, in addition to the obvious superiority, which won the jetboats in shallow water.
So, one of the Italian shipbuildingcompanies, advertising a boat with a water jet, indicates such features as a high degree of adaptability to changes in the load on the vessel (which may change very often), as well as a more substantial efficiency at speeds from 60 to 95 km / h.
Water cannons outside the shoal
These characteristics play far from the lasta role for a high-speed yacht, since on a classic propeller with an open propeller the speed of a vessel directly depends on the speed of rotation of the propellers. Changes in weather conditions, contributing to the slowdown of the ship, makes it difficult to maintain a constant speed. This adversely affects the performance of the engine due to the inability to develop a greater number of revolutions. Because of the peculiarities of the water cannon, which consists in the impossibility of overloading the engine, it became possible to develop a large number of revolutions, regardless of the speed of the vessel. That is, the number of revolutions will not fall, the engine load will remain the same, fuel consumption per unit of time will remain unchanged, but fuel consumption will increase per unit path.
In addition, the maneuverability of water jet propulsionallows yachts to moor in the conditions of close river moorings, but not specialized ports. In addition, an important aspect, thanks to which water canals won recognition in the field of application on cruise yachts, is their noiselessness.
Motor yachts begin to experience difficultiesmovement over 50 km / h in the open sea. This is due to the increasing resistance of water to the blades (even if rotating) of the propeller. When using a water cannon, the resistance is almost zero thanks to the propulsion design, which ensures a constant flow around the hull.
Cruise yachts rarely go at high speed,the need to use water cannons is most likely caused by the desire for a rational and safe engine operation. But there are also instances that provide for an increase in the speed of movement in the open sea due to power - that is, the installation of several engines.
Market share
The reliability of water cannons in littered ponds does not cause any complaints. It is known that ships overcome such polluted places as the English Channel, without a single failure.
Despite its usefulness, water jetsthey are used in the diametrically opposite spheres of shipbuilding: either on multi-motor cruise yachts, or on small speed boats or jet skis. And for the last water cannon is the only possible option. The lion’s share of the market is made up of boats of various sizes with classic propellers. About an extremely small number of boats that go off the conveyor, having already built water cannon, it is not necessary to mention.
Итого около 11% (по мнению экспертов) рынка belongs to water jet propulsion. But this figure can also be significantly reduced if we do not fully consider the market of propulsion devices, excluding jet skis, where the water cannon is an integral part of the design.
According to the forecasts of companies producing engines, there is a probability of an increase of this figure to 45% due to the disclosure of the potential of the market of jet propellers.
Reviews of engines and manufacturers
Many fishing enthusiasts prefer to use boats "Rotan 240M" in conjunction with a water cannon Yamaha 40.
According to their opinions, to the manufacturer Yamahaclaims are very minor. Basically, they are connected with mistakes “out of habit”, because the reviews were compiled for the most part by those who recently changed the water cannon from one to another. It does not immediately jerk from a place after a smooth feed of the lever, then deeply fails the back of the boat.
Negative reviews are seen in the address of the companyTohatsu. First, fishermen complain about the frequent purchase of defective products. Secondly, the model Tohatsu 40 got the nickname “dishonest forties”, since the engine does not produce 40 horsepower. Often replaced by Tohatsu 50, but this model quickly overheats.
Expediency of using a propeller
Installing a classic outboard moverit is advisable if it is necessary to use the most simplified design and move around water areas with a depth greater than average at low speeds (up to 50 km / h).
Well proven Yamaha engines. There are three main types:
- Median exhaust blade.The peculiarity of the structure is that the outlet through which the fuel is released, as well as the release of combustion energy, is located in the middle - in the center of the axis on which the blades are mounted.
- Screw constructions with an exhaust hole over the axis.
- Systems with two exhaust openings located above and below the axle.
Conclusion
In general, water-jet outboard motors bring many advantages to the design of the boat, but the disadvantages described above should not be discounted. Otherwise, an expensive mover can become a burden.
Foreign manufacturers produce boatwater cannons with very high efficiency and relatively small sizes. For example, a Yamaha water cannon measuring 350x560x300 mm and weighing 19 kg has a cost of about 75,000 rubles in the domestic market.
The Mercury ME JET 25 ml water jet (made in the USA) is more bulky: it has a length of 508 mm along the upper part of the body (horizontal), weight is about 60 kg, engine displacement is 420 cm3, the number of revolutions of the impeller per minute reaches 5000, fully manual control. The cost in the domestic market is already 263,500 rubles.
The Japanese Tohatsu M25JET water jet with similar characteristics (it differs only in the number of revolutions: 5200–5600 per minute) costs 287,500 rubles.
For comparison, a classic screw motor can be found at a price of 30,000 rubles or more.
No wonder because of this difference incost few decide to buy a water cannon. The price is considerable, and not everyone can afford such chic. It is hoped that over time, pricing will stabilize, as foreign manufacturers predict. Then jet propellers will win a significant market share.
It should also be noted that the growing popularity of the use of water jets is provided by the popularity of manufacturers. The most famous companies:
- Yamaha (Japan);
- Suzuki (Japan);
- Tohatsu (Japan);
- Honda (Japan);
- Mercury (USA);
The products of each company are characterized by their high quality, equipment and productivity ratio.
Question about the need to get spare parts foroutboard motors does not rise sharply. It's all about the fame of these brands. Details are available both for purchase on order and for sale in specialized stores or auto repair shops. Repair of water cannons is not a big problem.
Manufacturers pay a huge amounttime to check each drawing, part and each numerical indicator before putting the model on stream. Samples are being improved: water cannons are produced with a large number of cylinders, with a large number of screws, with shafts of left and right rotation. Particular attention is also paid to noise-insulating materials in the manufacture of appropriate gaskets in order not only to muffle the sound of a running engine, but also to reduce vibration. Exclusive steering systems are available for installation complete with a water jet. Devices to reduce the so-called torque in order to make the control of the ship the most comfortable.
There are fully lever designscontrol that does not involve the use of a cable system, which significantly reduces the likelihood of unpleasant situations that can suddenly bring an exploding cable.
Учитывая всё вышесказанное, к выбору водомёта It should be treated very carefully. Considerable funds invested in the acquisition should pay off in the future, and the difference between the use of screw and jet engines should be noticeable.
