Improving the performance of a small vessel is a task that sooner or later confronts every owner of a boat with an outboard motor. Often the regular transom does not allow optimally to set the different, which leads to a buoyancy of the nose in the wave or, conversely, to excessive stern lifting. cross-plate become an effective solution to the problem, allowing you to adjust the angle of inclination of the body already on the move.
Making this in your own workshop not only saves you money, but you also have confidence in the quality of your work, because you control every weld and mounting point. custom-solution You can adapt to the specific geometry of the bottom of your boat, whether it is PVC materials or aluminum alloy.
In this article, we will discuss the technical details of creating hydraulic plates, the choice of materials and the secrets of installation that will help you avoid the typical mistakes of beginners.
Principle of operation and impact on driving performance
The main function of transom plates is to create an additional hydrodynamic force acting on the stern of the vessel. When moving, the water flows around the surface of the plate, creating pressure that either raises or lowers the transom depending on the angle of deviation of the plate relative to the bottom, this allows you to compensate for the shift in the center of gravity when you change the load of the boat.
Use of use hydrocompensator It allows you to control the differentiator dynamically, for example, when you get on plane, the plates are lowered, helping the boat to jump into the water faster, and at cruising speed, they rise, reducing drag. Without this mechanism, the motor often runs inefficiently, overloading or, conversely, capturing air.
⚠️ Warning: Incorrectly installed or too large in area slabs can cause yaw on the course and make the control dangerous, especially in lateral wave.
The efficiency of the system depends on the area of the working surface and flow rate. At low speeds, the impact of the plates is minimal, but as the speed gains, their role becomes critical for the stability of the course, which is why it is considered mandatory for high-speed boats and boats with powerful engines to install adjustable transom plates.
Selection of materials and preparation of tools
For self-manufacture of transmutation plates, the corrosion resistance of materials is a key factor. Sea water and river environment with various impurities aggressively affect metals, so the choice of alloy should be justified. aluminum-alloy AMG series (AMG5, AMG6), which has excellent weldability and resistance to salt corrosion.
The metal thickness for the working plate is usually from 3 to 5 mm, which provides the necessary rigidity without excessive weighting of the structure. The use of stainless steel is also possible, but requires more complex processing and increases weight, which can adversely affect the weighting of a small vessel. Plastic composites are less often used in homemade structures due to the complexity of molding at home.
In addition to the metal, you will need a high-quality hydraulicsHomemade products often use pre-fabricated hydraulic cylinders from automotive systems or specialized actuators for marine applications. It is important that the cylinder rods are made of stainless steel, and the seals correspond to hydraulic oils and operating temperature.
- 🛠️ AMG5 sheet aluminum with a thickness of 4-5 mm for the manufacture of working plates.
- ⚙️ Hydraulic cylinders with a stroke of at least 150 mm and a force of 500 kg.
- 🔩 Fixing elements of stainless steel (bolts, nuts, washers) and epoxy sealant glue.
- 🧪 Degreasing, aluminum primer and two-component paint to protect welds.
When buying aluminum, be sure to check the alloy marking, as dural sheets (D16T) in salt water are prone to intercrystalline corrosion and will quickly collapse.
Drawings and calculation of plate geometry
Before cutting metal, you need to make precise geometry calculations: the area of the transom plate is usually 2-4% of the area of the bottom projection on the horizontal plane, too small area will not work, and too large will create excessive resistance and the risk of failure of the anchorages.
The shape of the plate is most often a trapezoidal or rectangular with rounded corners. Sharp angles can create flow vortexes, reducing efficiency. It is important to provide the angle of installation in the neutral position: the plate must be parallel to the conventional extended line of the bottom, so as not to create resistance when going straight.
The lever must be taken into account to calculate the hydraulic attachment points. The further away from the transom is the cylinder mounting point on the plate, the greater the deviation angle can be obtained with the same stroke of the rod. However, excessive removal of the mounting point increases the load on the fracture of the plate itself.
| Type of boat | Plate length (mm) | Slab width (mm) | Hydrocylinder stroke (mm) |
|---|---|---|---|
| Small size (up to 4 m) | 300-400 | 150-200 | 100-150 |
| Medium (4-6 m) | 450-600 | 200-250 | 150-200 |
| Boat (6+m) | 600-800 | 250-350 | 200-250 |
| heavy cruiser | 800-1000 | 350-450 | 250-300 |
Nuances of the shape of the back edge
The back of the plate should be sharp or have minimal rounding, so that's a clean flow of water, and if you make the edge thick, you create a zone of turbulence behind the plate, which will dampen the speed and create noise.
Manufacturing technology and welding work
The manufacturing process begins with cutting the metal according to the developed drawings. Aluminum cutting is better done mechanically (metal scissors, circular saw with a hard alloy disc) or plasma, avoiding gas cutters that heat the edges strongly and change the structure of the alloy.
Welding is the most important step. Arc welding is used for aluminum (arc welding).TIGIt is important to carefully clean the edges and adjacent surfaces to a metallic shine, removing the oxide film. Welding must be carried out with a filler material of the same brand as the base metal to avoid galvanic pairing.
The fasteners (cylinders and trench brackets) must be reinforced with headscarves. The tear load when hitting a wave can reach several hundred kilograms, so you can not save on metal at the attachment points. After welding, all the seams must be cleaned and treated with etching pastes to remove oxides.
☑️ Weld control
Pay special attention to the passage of hydraulic cylinder rods through the plate body, if you use an internal installation, and carefully sealed to prevent water from entering the structure or into the hydraulic system.
Installation of hydraulic system and electrical equipment
Mounting the finished plates on a transom requires precise positioning, the rotation axis of the plate should be about 1/3 of the length from the rear edge (or according to the calculations for your model), fastening to the transom is carried out through powerful brackets that distribute the load over a large area, preventing the transom from pressing.
The hydraulic system, in homemade versions, is often implemented through an electro-hydraulic pump (hydraulic station), consisting of an electric motor, a pump, an oil tank, distribution valves and the cylinders themselves, controlled from the remote control in the cockpit.
To connect electrical equipment, use only copper wires with a cross section corresponding to the pump consumption current, with mandatory insulation and protection from moisture. All connections must be soldered or squeezed into tin tips and filled with thermal shrinkage with adhesive layer.
⚠️ Attention: Hydraulic oil thickens at low temperatures, which can cause system failure. Use all-season hydraulic fluids (e.g. Dexron) and provide a bypass valve.
Electrohydraulic system is preferable to mechanical, as it allows you to control the plates with one hand, without breaking away from the control of the boat, and ensures smooth running of the rods.
Adjustment, adjustment and testing
The first descent should be in a calm environment, and the initial setup is to set the zero position, where the plates are parallel to the bottom, by adjusting the length of the rods or the position of the position sensors on the control panel.
In the test run, pay attention to the boat's reaction, and if the boat's nose doesn't rise when the plates are lowered and the speed drops, maybe the angle of attack is too high or the plates are set too high. If the boat starts to prowl, check the synchrony of the left and right cylinders.
Regular maintenance includes checking the oil level in the tank, inspecting the cylinder coils for leaks and checking the tightening of the fasteners, which tend to weaken from vibration. A properly functioning system should respond to remote commands without delay and jerks.
- 🌊 Check the plates at different speeds: from the exit to planing to the maximum stroke.
- 🔧 Examine the lower surface of the plates after the first 5-10 hours of operation for cavitation damage.
- 🔋 Control the battery charge as the hydraulic pump consumes significant current when operating.
Frequently Asked Questions (FAQ)
Can I use car hydraulic cylinders for transom plates?
Theoretically, it can be done if they fit in size and force. However, car cylinders (for example, from shock absorbers or GUR) often do not have sufficient protection against corrosion and may not withstand constant contact with water.
What angle of deviation of plates is considered optimal?
The optimal downward angle is usually 15 to 25 degrees from the bottom plane. Larger angles create excess resistance and can cause a flow disruption. The upward angle is usually smaller and is limited to the transom design so as not to damage the engine's lower unit.
Do I need a plate position sensor on the remote?
Without visual control (a hand indicator or a digital scale), you won't be able to know exactly where the plates are, making it difficult to fine-tune the trim on the go, which is critical for safety and efficiency.
How to protect aluminum from electrochemical corrosion?
You need to use zinc anodes mounted on the transom or the diewood of the motor, and it's also important to keep the aluminum parts from contacting copper wires or steel fasteners without insulating pads, and a high-quality paint coating is the first barrier to protection.