Operating an inflatable vessel in shallow waters, mud-covered waters or winter ice often puts the owner in a difficult position to choose the engine. The traditional outboard propeller is powerless here: the screw is instantly wrapped in algae, and a blow to the bottom or ice crumb can lead to fatal damage to the gearbox. It is in such extreme conditions that the focus comes to the fore. jet-engine A power plant that pushes a vessel with air rather than water.
This kind of propulsion, often called an air propeller or an air submarine motor, is a game-changer in how we navigate, allowing us to walk where other technology simply stands: on swampy slurry, among water lilies, on snowy virgin land, and even on broken ice. But switching to air propulsion requires an understanding of specific aerodynamics and safety rules that can be costly to ignore.
In this article we will discuss in detail the design features of such engines, methods of their adaptation for boats from the PVC and HypalonAnd we'll also make an honest comparison of efficiency with classic jet drives, and you'll find out why. efficiency of the air propeller on planing can reach 85%What tradeoffs will have to be made for this performance.
Principle of work and design features
The basis of any aeroplant is a power unit that rotates a large diameter propeller. Unlike marine engines, there is no lower unit foot immersed in water, which eliminates the risk of getting caught by underwater objects. The engine is usually installed on the stern of the boat on a special frame, and the air flow is directed back, creating a jet propulsion.
The key element of the system is the propeller itself, which is made of wood, composite materials or aviation aluminum and has a specific geometry of blades. Screw pitch It's a very high-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed inflatable tubes that are easily blown away by the wind.
The safety device is another important node without which operation is impossible. The screw is necessarily fenced with a ring protection (net or ring) to prevent the blades from contacting people or foreign objects. The speed of the ends of the blades can exceed 200 km / h, and getting there a finger or fishing line will lead to instant and severe injury.
⚠️ Attention: It is strictly forbidden to start the aero engine if there are people or animals in the immediate vicinity (less than 5 meters), the flow of air from the screw raises dust, sand and small stones that can cause serious damage to the eyes and skin.
The belt is often used to transfer rotation from the engine to the screw, which serves as an additional torsion damper. The belt also serves as a safety lock: when the screw is jammed sharply (for example, when hitting a branch), it can slip or break, saving the crankshaft of the engine from destruction.
Advantages and Disadvantages of Air Traction
The switch to an aero engine is always about balancing patency and comfort, and the ultimate trump card is absolute ubiquity, and the propeller boat is not afraid of shallow water 5 to 10 centimeters deep, making it ideal for duck hunting in wetland deltas, and the lack of submerged parts eliminates shell and algae fouling, which saves the owner from frequent cleanings.
But there's a downside to the coin: Aeromotors tend to be much noisier than their water counterparts; the rotating screw and engine exhaust (if it's gasoline) create a constant background hum that can scare off careful fish and annoy others; and it's difficult to operate such a boat at low speeds because of the inertia of the airflow and the lack of a clear traction vector at low revs.
The economic aspect also requires attention. Air engines often have higher fuel consumption, as they have to overcome the greater aerodynamic drag of the hull of the boat, which, unlike plane boats, is not always streamlined. Wind and lateral turbulence have a much greater impact on a flat-bottomed inflatable boat with aeromotor sailing than on a classic PVC suspension boat.
Among the advantages is simplicity of design: there is virtually nothing to break in the context of interaction with water in an aero engine. There is no glands that flow, there is no lower unit that bends, there is no water pump that clogs with sand. Maintenance is reduced to lubricating bearings, checking the tension of the belts and monitoring the condition of the screw.
Adaptation of PVC boat under the aero engine
Standard inflatable boats are not designed to fit bulky frames with engines. transom board conventional "Velcro" will not withstand the vibration and weight of the power unit. So the first step is to strengthen the aft. Often owners weld to the factory transom additional profile of duraluminium or use special transition plates that distribute the load on the cylinders.
Vibration is the main enemy of inflatable material. Constant shaking from the running engine can lead to the wiping of the fabric in the places where the frame is attached. To minimize this effect, vibration insulation materials such as rubber or special damping pads should be laid between the frame of the motor and the trunk of the boat.
☑️ The boat is ready to install an aeromotor
The important thing is that the propeller and the safety net engine weigh a lot, and if you put it on the edge of the transom, it can cause differentiation at the stern, the boat will snarl, and the plane will be unstable, and in some cases, you need to move the battery and passengers closer to the nose to balance the vessel.
⚠️ Attention: Never attach the frame of the aero engine directly to the inflated cylinder without a rigid transom. The propeller blade can touch the cylinder, and the consequences of such contact will be fatal to the integrity of the boat.
The installation often requires dismantling of regular elements, such as rod holders or awning arcs, which can get into the air sucking zone. The area of rarefiedness in front of the screw is large enough that any light object that gets there will be dragged into the screw with the force of a bullet.
Comparison: Aeromotor vs. Screw motor
To make a good decision, you need to be clear about the difference in performance: a screw motor is effective in deep water and in going against the current, where it "clings" to dense water mass, and an aero engine wins where water is mixed with silt, grass or ice. Below is a comparative table of key parameters.
| Parameter | Aeromotor (Air propeller) | Classic screw engine |
|---|---|---|
| Permeability | The highest (grass, silt, ice, stones) | Low (risk of damage to the screw) |
| Noise level | Very high (screw hum + motor) | Medium/Low (depending on model) |
| Management of small | Difficult (flow inertia) | Excellent (clear traction vector) |
| Service | Minimum (no water pump) | Regular (pomp, galls, lower unit) |
| Security | High (screw closed), but noise is dangerous | Medium (open screw under water) |
It's worth noting that in deep, clean water, the propeller will always be more economical and quieter. The aerodynamic drag of water is hundreds of times higher than the air resistance, so it takes more power and therefore more fuel to create the same propeller traction. However, if your route passes through the "impassable" thickets, the savings in time and nerves will overshadow the cost of gasoline.
Another nuance is the possibility of reverse. On screw engines, the reverse is structural and works instantly. In aeromotors, the reverse is often absent or implemented through the rotation of the steering nozzle, which is less efficient and takes time. It is more difficult to stop an accelerated air-drawn boat because of the lack of water braking against the body of the lower unit.
Installation and engine setting
The installation process begins with a rigid fixation of the frame on the transom. Use bolt connections with the growers, as vibration can unwind any nuts in a matter of minutes. After installing the engine, you need to check the alignment of the shafts (if a gearbox is used) and the tension of the drive belts. The belt should not be pulled, but you can not sag more than 1-2 cm when you press your finger.
Secrets of setting up the screw step
To fine-tune your pitch, use a tachometer. Start the engine at full gas. If the speed is below the passport maximum, the pitch is too high, you need to reduce it. If the engine overtwistles the norm, the pitch is small, the screw is not loaded, and you lose traction. Perfectly set up allows the engine to go 90 to 95 percent of the maximum speed under load.
The carburetor is only set up after heating up, the mixture should be slightly enriched at idle and stable at high revs. Since the aero engine operates in constant blowing conditions, the cooling system (if it is airy) usually does well, but in hot weather it is worth controlling the temperature of the cylinder head.
It is important to correctly set the angle of attack of the screw relative to the surface of the water. Too low landing will lead to the capture of the spray and loss of traction, too high - to the roll of the stern and the boat goes into a tailspin. The optimal position is considered where the plane of rotation of the screw parallel to the bottom of the boat at the time of planing.
Safety rules for operation
Operating an aero engine requires discipline. As mentioned, the propeller must be free. But there are other risks. When driving through rocky shallow water, the propeller can pick up sharp stones that ricochet to the sides when hitting the safety net, so the use of safety goggles for the driver and passengers is a must.
Windy weather is another risk factor: a boat with an aero engine installed has a high sailing speed; a gust of side wind can easily turn a light vessel over or turn it across the wave; in such conditions, you need to drop gas and lie on the bottom of the boat, reducing the center of gravity; maneuvering in narrowness is also difficult due to the large radius of reversal and inertia.
Keep tight: When installing the engine on a transom, use additional neoprene gaskets. Vibration can disrupt the tightness of the adhesive seams of the transom board, and water will begin to flow inside the cylinder or between the PVC layers.
Fire safety is also the first priority, especially when using gasoline engines. The fuel tank must be securely secured and protected from direct exposure to exhaust gases and sparks.
Maintenance and care
Regular maintenance prolongs the life of the unit. After each trip, you need to clean the screw and the protective net from sticky dirt, insects and grass. Rotor balancing is a procedure that should be done once a season. Imbalance leads to shafts beating and accelerated wear of bearings.
The belt transmission needs to be inspected for cracks and scuffs, rubber will dry up over time, especially under the influence of ultraviolet light and temperature changes, and belt replacement is an inexpensive procedure, but it must be done preventively, before it breaks away from shore.
For the two-stroke engines most commonly used in these installations, the quality of the fuel mixture is critical. Use only fresh gasoline and quality oil for two-stroke engines in the right proportion. Poor-quality oil will lead to a load on the candle and in the exhaust channel, which will reduce power and increase smoke.
Regular lubrication of the frame bearings and checking the tightening of bolt joints is the key to safe operation of the aeromotor for a long time.
Keeping the boat with the engine installed in the assembled form is not recommended. It is better to dismantle the engine and store it in a dry room, and keep the boat in a slightly deflated state or on special stands to avoid deformation of the transom under the weight of the unit.
Frequently Asked Questions (FAQ)
Can I install an aero engine on any PVC boat?
Theoretically, it can, but it requires a lot of work, and it has to have a rigid transom that can withstand a weight of 30-50 kg, and a sufficient load capacity. On lightweight rowing boats of the seagull type, it is impossible to install a powerful aero engine because of the risk of loss of stability.
What is the maximum speed of a boat with an aero engine?
The speed depends on the power of the engine and the shape of the hull. On a standard flat-bottomed PVC boat with a length of 3.6-4 meters with an engine of 15-20 hp, you can reach a speed of 25-35 km / h. Record samples with streamlined hulls reach 60-70 km / h, but this is already a specialized technique.
Do I need to register a boat with an aero engine in GIMS?
Yes, if the engine power exceeds 5 hp (or 8 hp depending on current legislation and fuel type), the boat is subject to mandatory registration.
How to lubricate the bearings of the propeller?
Use high-speed bearing lubricants that are resistant to leaching and high temperatures (such as lithium lubricants with molybdenum disulfide). Conventional solidol may not withstand speed modes and leak out.
Is it true that the engine stalls on the water?
The engine itself does not die from the water, because the air intake is usually located high, but with heavy chop or careless maneuvering, splashes can fall into the carburetor or candle, causing interruptions in operation, the correct installation and the presence of spray agents solve this problem.