The Secret Revealed: The Fundamental Logic Behind Motorboat Navigation - Part One

Core power: Achieving forward thrust through "water jetting"

Whether it's the outboard motor hanging at the stern of the boat or the inboard motor hidden inside the hull, the core task is to drive a component called "the impeller" to rotate at high speed. This impeller just like an "underwater blower". When the engine starts, the rotational speed of the impeller can reach several thousand or even tens of thousands of revolutions per minute, voraciously "devouring" the surrounding water and then forcefully spraying it out from the tail of the flow channel.

Perhaps someone might ask: Why not use propellers to directly push through the water instead of having to suck in water and then spray it out? This brings us to the advantages of water jet propulsion. Firstly, it is safer. If the propellers are exposed, when rotating at high speed, they can easily injure the creatures in the water and are also prone to getting tangled up with water weeds or fishing nets. However, the impellers are hidden inside the flow guide tubes, effectively avoiding these problems. Secondly, it is more efficient. The flow guide tubes can gather the water flow, making the thrust more concentrated. Especially when navigating in shallow waters, water jet propulsion will not scrape against the sand and rocks at the bottom like propellers do, and it has better adaptability. Moreover, the acceleration feeling of water jet propulsion is more linear, without the "jerkiness" felt when propellers are pushing through the water. The driving experience is smoother.

Navigation status: From "floating on the water surface" to "gliding along the water surface"

When the motorboat is just started, its speed is relatively slow. At this time, most of the boat is floating on the water surface, just like an ordinary small boat, supported by the buoyancy of the water. But as the speed increases, the design of the boat begins to take effect, which is also the key to its ability to "fly along the water surface".

The hull of the motorboat is not flat. The bottom has a special streamlined design, and there are protrusions on both sides resembling "small wings", professionally known as "anti-tilt wings". The bow of the boat is a pointed curved shape. When the speed reaches a certain level, the fast-moving boat will press against the water surface, and at the same time, air flows between the bottom of the boat and the water surface, forming a thin "air cushion". This air cushion is like an invisible pillow, lifting the hull upwards, and reducing the contact area between the hull and the water surface.

When the contact area becomes smaller, the resistance of the water naturally decreases significantly, and the speed increases rapidly. When the speed is high enough, only the tail guide tube and a small part of the bottom of the entire hull come into contact with the water surface, just like "gliding" on the water. This is what we commonly refer to as the "water-contact flight" state. At this time, the driver can clearly feel the hull being lifted upwards, and the jolting sensation is greatly reduced. Only the resistance of the wind and the roar of the water jet remain, and the stimulation is at its peak.

The gliding states of different types of motorboats are also different. Leisure motorboats are relatively wide and thick, with a lower center of gravity. Even if the speed is not fast, they can still maintain a stable floating state. However, the hulls of competitive motorboats are narrower and lighter, made of carbon fiber materials. Only when reaching a certain speed can they enter the gliding state. Once the speed drops, they will "sink" back to the water surface again, with increased resistance and a rapid decrease in speed. This is why in competitive motorboat races, the competitors rarely slow down. Once they do, it is very difficult to catch up with the opponents in front.

Control technique: No rudder is used, the direction is controlled solely by the "flow direction" of the water.

Many people think that motorboats turn like ordinary small boats by using the rudder. But that's not the case - motorboats don't have the traditional rudder at all. Their turning and reversing are all achieved by controlling the direction of the water jet. In essence, it's "guiding the hull with water flow". The operation logic is actually much more ingenious than imagined.

Let's talk about the turn. Between the impeller and the water outlet, there is a "directional guide plate" that can rotate left and right. This guide plate is like an adjustable "water faucet nozzle" and can change the direction of the water flow. When you turn the handle (or steering wheel) of the motorboat, it will be driven to rotate by a thin cable: if you want to turn right, the guide plate will direct the water flow to the left, and the powerful water impact force will push the boat tail to the left, causing the bow to naturally turn to the right; if you want to turn left, the guide plate will direct the water flow to the right, the boat tail will deviate to the right, and the bow will turn left.

Here is an important driving tip that new drivers must remember: A motorboat can only turn when water is sprayed out. If you suddenly release the throttle, the engine speed drops, the force of the water jet from the propeller is insufficient, or even stops spraying water, the guide plates lose their function. The motorboat will lose all steering ability and can only drift straight forward, which is very prone to losing control. In the past, many beginners lost their boats or collided with other vessels because they suddenly turned while releasing the throttle. Now, the new models of motorboats have added an intelligent assistance system. Even if you release the throttle, as long as you turn the handle, the computer will automatically control the engine to restart the spraying device, maintaining sufficient water flow to assist in steering, which has greatly improved safety.