Owners of inflatable boats often face a situation where the standard specifications of the coatboard It is not enough to install a more powerful engine or specific equipment, and standard models, especially budget segments, are often limited in height or width, which does not allow you to comfortably operate the boat in certain conditions. The optimum transom height for most outboard motors is 381 mm (15 inches) or 508 mm (20 inches) from the keel to the anti-cavitation plate. If your engine “snarls”, but the boat does not accelerate, or if the nose is constantly uphill, the problem may lie in the geometry of the stern.
The rear end upgrade is not just about nailing an extra board, it's an engineering challenge that requires understanding the distribution of loads. sternIn this article, we will discuss proven methods of changing the geometry of the transom, the choice of materials and the nuances of installation that will ensure the safety and durability of your design.
Diagnostics and calculation of necessary changes
Before you start to take up the tools, you need to determine exactly what you are not satisfied with in the current configuration, most often you need to either raise the mounting point of the engine higher (increase the height) or expand the seat to install a second engine or gas cylinder. transom plate It's under tremendous stress, so any changes should be mathematically based, and measure the current distance from the bottom of the balloon (keel) to the top of the transom and compare it to the recommended values for your motor.
If you are planning to install a heavier motor, it is important to consider the displacement. centreIncreased transom height will raise the motor higher, which may require shifting seating position of the crew or redistribution of the cargo to the bow, and also assess the condition of the cylinder at the adjacent transmuner: if PVC has worn out or has microcracks, modernization can not begin.
⚠️ Warning: Never exceed the maximum allowable power of the motor specified by the boat manufacturer, even if you have strengthened the transom. Increasing the height of the motor mount changes the thrust vector and can lead to the boat tipping over under sharp gas.
To calculate the new height accurately, use a simple formula: the desired height of the anti-cavitation plate above the keel plus the thickness of the engine's lower unit. Write down all the measurements so you don't get the materials cut wrong. A mistake of a couple of centimeters can cause the engine to run inefficiently, consuming more fuel.
Selection of materials for translance build-up
The key to success is the right (material choice) and the transboard must be rigid but light enough not to overload the cylinders. Traditionally plywood is used, but modern composites or special woods are better suited for building.
Let’s consider the main options of materials:
- 🌲 Marine plywood (Bakelized): Classic choice: It's very strong and resistant to moisture, but it's very heavy, it needs quality impregnation and coloration.
- 🧱 Composite panels (ACP): Aluminum with a plastic core. Lighter plywood, not rotting, but more difficult to process and requires special fasteners.
- 🪵 Leaflet: Dense wood that doesn't rot in water, heavier than pine, but more durable, great for overlays.
- 🛡️ Glass plastic: It allows you to create any shape, but requires skills of lamination and creating a matrix.
When choosing plywood And you should pay attention to the labeling. Only the stamp is suitable for the aquatic environment. FSF (phenol formaldehyde glue) or ideally bakelized plywood FB- Regular building plywood FC It will dissipate quickly even with good painting, and the thickness of the build-up part should be at least 12-18 mm to ensure the necessary rigidity when attaching the engine rods.
You'll also need epoxy soaking resin, edge-plating glass and a quality marine sealant. Don't skimp on fasteners: bolts must be made of stainless steel. A4 (316) It's not allowed to use aluminum fasteners because of electrochemical corrosion when paired with other metals.
Technology of increasing the height of the transanth
The process of increasing the height of the transom requires precision and consistency of actions. The main task is to create a rigid structure that will not "play" under the vibration of the engine. First, you need to dismantle the regular transmuter board, if the design of the boat allows it, or work directly on the reinforced stern.
Step-by-step algorithm of actions:
- Remove the dimensions from the standard transom and prepare a template from cardboard.
- Cut the main part from the selected material (plywood or composite) with a margin of 1-2 cm in height.
- Treat the edges of the part, rounding them with a radius of 3-5 mm to prevent damage to the cylinder.
- Glue the ends with fiberglass on an epoxy resin in 2-3 layers.
☑️ Checklist for preparation of materials
A system is used to attach a new, higher board to the cylinder. sling or metal-cornerIf you're putting a plate on top of a regular transom, the surface should be perfectly cleaned and defatted, and the sealant layer between the old and the new board is mandatory, so it will prevent water from getting in and rotting.
⚠️ Attention: As the transom height increases, the stern sail area increases. In windy weather, the boat can turn more sideways to the wave, be prepared to adjust its course more actively than usual.
An important step is the installation anticavitational After you install the new board, put the engine on and check the position of the screw relative to the bottom. If the screw is too high, cavitation and loss of traction will occur; if it is too low, water resistance will increase. The ideal position is when the anti-cavitation plate is in the same plane as the bottom of the boat or 10-20 mm lower when entering the plane.
Strengthen design and protect against moisture
Any wooden part in contact with water is subject to destruction, so high-quality waterproofing Even the most expensive plywood will eventually feed moisture through the microcracks in the paint layer, and the best solution is to paste the entire surface, including the ends, with fiberglass on epoxy.
The protection process is as follows:
- 🖌️ Grounds: Applying diluted epoxy resin to fill the pores of wood.
- 🧵 Reinforcement: Sticker layer of fiberglass density of 200-300 g / m2.
- 🎨 Finishing: Applying 2-3 layers of epoxy varnish or specialized yacht paint.
Pay special attention to the mounting places of the engine rods, which is where chips and cracks most often appear. metal-plate They'll take the main pressure of the screws and protect the tree from being pushed.
The secret to the longevity of the transan
Experienced craftsmen advise putting the transom in a vacuum chamber after assembly (or using a vacuum infusion method at home using a vacuum cleaner) to remove air from the layers of fiberglass as much as possible, making the coating monolithic and water-resistant.
If you use a bolt connection of a new board with the elements of the boat, all the holes must be drilled with a margin of 1-2 mm and filled with a sealant before installing the bolt. This will prevent the capillary effect when water flows into the tree along the thread of the fastener. Once the sealant is dry, a watertight plug forms.
Comparison of methods of transom modernization
There are several approaches to changing the geometry of feed, and the choice depends on your skills and budget. Below is a comparative table of basic methods so you can choose the best one.
| Method | Complexity | Cost | Reliability |
|---|---|---|---|
| Plywood plate | Low. | Low. | Medium |
| Replacement of the transom board | Medium | Medium | High. |
| Plastic-glass elevator | High. | High. | Very high. |
| Aluminum profile | Medium | High. | High. |
Method liner Suitable for temporary solutions or small height adjustments (up to 3-5 cm). transom Plastic fiberglass solutions require skill but produce the perfect result in weight and durability. Aluminum profiles are lightweight but require careful PVC insulation to avoid a chemical reaction.
When choosing a method, consider the weight of the structure. Increasing the weight of the stern will require more careful balancing of the boat. If the stern becomes too heavy, the boat will be worse on the plane and may become a roller on turns. balloon or aerators in the nose for compensation.
Engine adjustment after modernization
After installing the enlarged transom, you must re-tuning the outboard motor, changing the height of the mount, and therefore the angle of attack of the screw. First check the engine at idle speed, making sure that the water from the control hole ("urinal") is a good stream.
Basic parameters for verification:
- Other angle (Trim): Adjust the tilt of the motor relative to the transom. With the right trime, the boat should go to the plane quickly, and the nose should not be bullied too high.
- Rotor position: Make sure the propeller is fully submerged in water even when the boat is rolling.
- Thermostat operation: Watch the temperature, as changing flow hydrodynamics can affect water intake.
Use test runs with a GPS tracker or speedometer. Record the top speed at different positions of the angle of the trim to find the middle ground for your new transom configuration.
Notice the vibration, if you've got a strong high-speed vibration after the upgrade, maybe you've got a bad alignment, or you've got a turbulence zone, and you might need to install it. hydrofoil It will also help to stabilize the boat and improve the plane.
⚠️ Warning: After the first 30-50 minutes of working on the new transom, be sure to pull all the bolt joints. Vibation of the new motor can weaken the fastener if it was not fixed by the growers or the thread fixer.
Remember, increasing the transom is a change in the data-sheet specifications of the boat. Be careful on the water, especially when you're excited. The new configuration may behave differently in calm water and on the wave. Do the tests in a safe place, away from the main fairway and bathers.
Properly increased and reinforced transom allows you to unlock the potential of a more powerful engine, but requires mandatory balancing of the boat and careful waterproofing of new elements.
Frequently Asked Questions (FAQ)
Can I increase the transom on the boat without removing from the cylinders?
Yes, it's possible by a patching method, you make an extra board of the right height and attach it to the standard transom with through bolts and a sealant, but this method adds extra weight and can make it harder to access the interior of the transmachine compartment for maintenance.
What thickness should be plywood for reinforced transom?
For most PVC boats up to 4 meters long, the optimal thickness is 18-25 mm. If you plan to install an engine with a capacity of more than 15 hp, it is recommended to use plywood 25 mm thick or make a sandwich design with stiffness ribs.
Do I need to register changes in the GIMS after the transparticle increases?
Under current Russian law, changing the design of a small vessel to affect its safety (and changing the power of the motor and the geometry of the transom includes this) formally requires changes in documents or re-registration. However, in practice, unless you change the class of the vessel radically, this is often neglected, but the legal risk remains.
How to paint a new transom for maximum protection?
Two-component epoxy soils and enamels are the best, and UV filtered yacht lacquers are the best, and it's important to cover not only the visible part, but all the ends and the places under the fasteners.
Will the high transom affect the boat's handling?
Yes, a high transom raises the center of gravity of the motor, which can make the boat more sensitive to roll, and it can also sail more strongly, and you can compensate by properly loading the bow and mounting the hydrofoil on the motor.