Hard inflatable boats, known worldwide as RIB (Rigid Inflatable Boat) or simply RIB. ribIt is one of the most popular types of boats for fishing, diving and family walks, and the combination of hard fiberglass or aluminum bottom with inflatable tubes provides perfect stability and unsinkability.
The key element in this relationship becomes boat-engineIt is the right power selection plant depends on whether your swimming will be a pleasure or turn into an endless struggle with the wave and fuel consumption. Competent assembly of the kit "body plus engine" allows you to develop high speeds and feel comfortable even in severe excitement.
In this article, we will discuss in detail all the nuances of the selection, installation and operation of ribs. cross-board should be strengthened, how to calculate the necessary traction and what to pay attention to when buying a used kit.
Structural features of ribs and influence on the choice of motor
The main difference between a rib and a conventional inflatable boat or a classic boat is the V-shaped hull, which cuts through the wave to provide a soft ride, which is critical for the safety of the crew at high speeds, but this geometry requires a more powerful engine to get on plane, especially if the boat is fully loaded.
The inflatable tubes that make up the sideboards work as additional shock absorbers, but they also create sailing. motor-power Not only does the weight of the hull have to be taken into account, but the wind load as well, and a motor that is too weak will not be able to effectively withstand the side wind, making the control of the boat dangerous.
The most important element of the design is the transom. In quality ribs, it is made of multi-layered plywood coated with fiberglass or entirely of composite, and it is on the transom that the main vibration and traction force are transmitted. Aluminum trans They are less common and require special attention to corrosion when using salt water.
⚠️ Warning: Never install a motor more powerful than the boat's passport (maximum power on the transom) and exceeding the limit can lead to transom tearing, flooding and loss of the boat.
The material of the cylinders also plays a role. PVC (PVC) is more resistant to abrasion and fuel than HypalonThe weight of the boat in the running order directly affects the choice between two-stroke and four-stroke engines.
Two-stroke or four-stroke: the eternal dilemma of a water motor
The choice of engine type for the rib is often the subject of fierce debate. Two-stroke (2T) motors are traditionally lighter than their four-stroke counterparts (4T) of the same power. For ribs, which often have to be pulled ashore or lowered from the runners, each kilogram per kilogram per mile. lower unit It matters.
Four-stroke engines are more economical, quieter and more environmentally friendly, and they don't require a mixture of oil and gasoline, which makes it easier to operate, but their weight can shift the center of gravity of a rib boat, making it more roller-like on corners. hanging passengers and cargo.
In terms of dynamics, 2T engines provide a sharper acceleration, which is important for reaching the plane with full load. 4T engines win in cruising speed and range on a single tank. For fishing, where you often need to go to the point, a four-stroke will be more profitable.
- 🚀 Speed: 2T engines are usually faster at the start, 4T more stable hold the cruiser.
- ⚖️ Weight: Two-strokes are 15-25% lighter, which is critical for small ribs.
- 🔇 Noise: Four-strokes work much quieter, without scaring the fish.
- 💰 Price: The initial cost of 2T motors is usually lower.
If you are planning to use the boat for long-distance crossings and tourism, four-stroke For short trips, or where every kilogram of weight is important, the two-stroke remains king.
When buying a used four-stroke engine, be sure to check the level and color of the oil. Milky shade indicates that water enters the crankcase, which means serious breakage of the seals.
Power calculation and engine selection criteria
Rib motor selection is the math of safety. There's a formula that can approximate the power required to get on plane: 1 hp per 25-30 kg of total weight (boat + motor + crew + equipment). However, for ribs with a deep V-bottomed bottom, the coefficient may be higher.
It is important to consider gear ratio of the gearbox. For heavy ribs and large screws, gearboxes with a large gear ratio (for example, 2.33:1) are preferred, which provide better thrust at low revs. This allows you to quickly bring the heavy boat to the top of the gearbox. plane-mode.
The length of the diewood (legs) of the motor should correspond to the height of the transom. The standard for most ribs is a long leg (L, 508 mm). Installing a short leg (S, 381 mm) on a high transom will lead to cavitation of the screw and loss of speed, as well as to overheating of the engine due to insufficient water intake.
| Parameter | Influence on choice | Recommendation for RBI |
|---|---|---|
| Boat weight | Determines mine power. | Minimum 1 hp per 25 kg weight |
| Type of use | Speed vs Savings | Fishing - 4T, cruising - 2T |
| Transcent height | Choosing the length of the leg | Standard 508 mm (Long) |
| Downloading | Power reserve | Take the engine with a margin of 20-30% |
Don't forget the control system. For motors over 30-40 hp, ribs are already desirable. remote-gas and steering (hydraulic or cable), as the physical force on the tiller becomes too large for comfortable control.
What is cavitation and how is it dangerous?
Cavitation is the formation of vapor bubbles in the flow of fluid, which on the propeller looks like boiling water, and is dangerous because the bubbles collapse, destroying the metal of the screw (erosion) and dramatically reduce the efficiency of the engine, causing it to overheat.
Rules of installation and centering of the motor on the transom
The right engine installation is not only about speed, but also about safety, and it has to be fixed in the center of the transom, and moving to the side will cause the boat to roll permanently, which will have to be compensated by the movement of passengers or trim, which is uncomfortable and dangerous.
The height of the diewood installation is adjusted by means of holes in the bracket. The optimal position is when the anti-cavitation plate is on the same line with the bottom of the boat or 1-2 cm lower. If you lift the engine too high, the screw will capture air on the wave; too low, water resistance will increase.
When installing, you must use it. slip-pad between the motor and the transom, unless it's designed to hold it, and this will prevent damage to the paint coating of the transom and reduce the vibration transmission to the body.
⚠️ Warning: Always use a safety cable for the motor, pass it through the standard hole in the lower unit and securely attach it to the rim bolt on the transom, which will save the motor when it falls into the water.
The tightening of the mounting bolts must be done with a dynamometer key according to the manufacturer's specification. Insufficient tightening will lead to backlash and vibration, and the pulling can split. transmutant Or deform the rods.
☑️ Checking the engine installation
Rotary pair: how to choose the perfect screw
The propeller is the propeller that turns the power of the motor into motion. For ribs, which often operate in cargo or towing mode, the right pitch of the propeller is important. Too much stride will keep the motor from spinning to working turns, causing detonation and overheating.
The material of the screw also matters. Aluminum screws are cheap and bend when hit by a rock, keeping the engine shaft intact. Stainless steel is stronger and more efficient, but when hit hard, it can transfer loads to the engine. gearboxFor rocky terrain (rocky bottom), aluminum is preferred.
The rotor is checked using a tachometer. At full gas (WOT), the engine must produce speeds in the range specified in the instructions (usually 4500-5500 rpm). If the revolutions are lower, the step is too large, if higher, small.
- 🔩 Aluminum: Cheaper, safer for the shaft when hit, but less effective.
- ✨ Stainless steel: It gives an increase in speed of 5-10%, longer, but more expensive.
- 📐 Step: The smaller step is better than the thrust, the larger is higher than the max. speed.
Ideally, you'd have two sets of screws on the rib: a lower-pitched cargo screw for full loading and a faster screw for cruising, and it takes two minutes to replace the screw in the field, and it changes the behavior of the boat.
A properly selected screw allows the engine to operate in the optimal range of revolutions, prolonging its life and reducing fuel consumption by up to 15%.
Operation, maintenance and safety on water
Rib with motor requires regular maintenance, after each foray into salt water, you must thoroughly wash the cooling system with fresh water. aluminum-alloy And magnesium anodes, which need to be changed as they break down.
inflatable tubes also need protection. Although modern fabrics are resistant to UV radiation, prolonged parking under the scorching sun with pumped cylinders reduces their resource, use protective covers or awnings when the boat is standing on the water or on the trailer.
Always carry a minimum set of tools on board: candle key, spare candles, a set of screwdrivers, passages and a remake for the boat. Anything happens on the water, and the ability to replace a candle yourself or paste a puncture can save the day.
Crew safety is priority #1. Rib is resilient, but sudden movements at high speed can cause people to be thrown overboard. safety-jacket The presence of a safety check (kill switch), tied to the helmsman's wrist, will prevent the boat from moving in a circle in the event of a person falling overboard.
⚠️ Warning: Always check before starting the engine to see if the algae or fishing gear is screwed, which can cause instant overheating and destruction of the osteoils.
These simple rules will allow your rib to serve for years, giving only positive emotions from communication with the water element. Remember that water does not forgive carelessness, but generously rewards the prepared.
Keep the boat with the cylinders at half-flat or at least with the valves weakened if it is in a warm room. A change in temperature can cause balloons to inflate and damage to the seams.
Can I use an electric motor on a rib?
Yes, but there are nuances: electric motors are only suitable for small ribas (up to 3.5-4 meters) and calm water. Electric thrust is usually not enough to enter the plane, so the boat will go in displacement mode, which is slow and creates a large wave. This is an option for quiet fishing in the no-go zones for ICE.
How often should you change the oil in the gearbox?
It is recommended to change the oil in the gearbox (transmission) once a season or every 100 motor hours. Before winter storage, it is mandatory to replace the oil in the gearbox so that water accidentally enters the gearbox does not freeze and break the gearbox body.
What if the ribbe started to prowl at speed?
Whispering is often caused by improperly placing the trim tab on the anti-cavitation stove, which must be shifted in the opposite direction of yaw, and may also be caused by improper loading of the boat or a damaged propeller.