Many inflatable boat owners are faced with a situation where the normal power of the engine becomes insufficient for the desired speed or operating conditions. Often the solution lies in replacing the engine with a more powerful one, but here there is a technical problem: cross-board It may not be able to withstand the increased loads or it may not fit the geometry of the mounting, and in such cases the only sure way out is to upgrade the stern of the vessel.
The process of increasing the transom requires careful preparation, understanding the physics of loads on the body and quality selection of materials. Errors in calculations or savings on components can lead to the fact that at the most inopportune time. motor This article details the technology of strengthening and lengthening the transom board, allowing the boat with a more powerful engine to be safely operated.
Before cutting materials, you need to make a thorough diagnosis of the current condition of your boat. slingcondition glued If the boat has a solid mileage, it might make sense to combine the upgrade with preventive repairs to avoid double disassembly of the mounting units.
Necessity analysis and load calculation
The first step is always to understand why you need to build up the transom, most often it is associated with installing a motor that has a longer lower unit than the standard one, or you need to compensate for the change in the differential as you increase the power, and improper calculation of the angle of inclination or height of the suspension of the engine will lead to cavitation, overheating and lowering the efficiency of the screw.
When calculating loads, not only the weight of the engine should be taken into account, but also the dynamic forces that arise when planing and shocks against the wave. transom plate It's under tremendous pressure to pull and compress, and if you plan to put 20 to 30 percent more powerful than your regular engine, standard plywood may not be able to handle vibration and torque.
⚠️ Warning: Exceeding the engine power recommended by the manufacturer by more than 30% without strengthening the entire design of the cylinders and bottom can lead to rupture of the seams and loss of buoyancy.
To accurately determine the necessary parameters of the build-up, you can use a simple formula or empirical method of fitting.
Selection of materials for modernization
The quality of the result depends on the materials chosen, and the basis for the build-up is marine plywood, which should be highly dense and moisture-resistant, and the use of conventional construction plywood is unacceptable, as it will quickly dissipate under the influence of water and vibration.
For gluing and protection, special epoxy compounds and fiberglass are used, and it is important to choose components that, after polymerization, form a rigid, but not fragile structure. Epoxy resin It must be compatible with the cylinder material so as not to damage the PVC upon contact.
Below is a table of recommended materials for the various stages of work:
| Component | Recommended material | Appointment |
|---|---|---|
| Basis | Plywood FSF or Bakelitov | transom-bearing structure |
| Protection | T-11 glass, T-13 | Waterproofing and reinforcement |
| binder | Epoxy resin ED-20 + hardener | Impregnation and gluing of layers |
| Fastening | Stainless steel A2, A4 | Bolts, washers, bushings |
Additional requirements corrosion-free For metal elements and possibly PVC paint, if the decorative layer is to be re-established, all wooden elements must be thoroughly dried before assembly.
When buying plywood, be sure to check each sheet for no internal voids and layers, tapping it, even a small defect inside the sheet under load will become a source of destruction.
Tools and workplace preparation
To do this, you need a set of carpentry and metalworking tools, and the workplace needs to be well lit and ventilated, because the epoxy vapors are toxic, and you need to prepare everything in advance to keep the glue polymerization process in check.
You'll need a wood-fisher jigsaw, a grinder, or a set of sandpaper of different grains, strubs to fix the parts, and personal protective equipment like a respirator, gloves and glasses. Security When working with chemicals and power tools should be in the first place.
The list of necessary tools includes:
- 🛠️ An electric drill or screwdriver with a set was drilled on wood and metal.
- 🪚 A knife or jigsaw for precise plywood cutting.
- 📏 Roulette, coal mine and a marking pencil.
- 🖌️ Hands and rollers for applying epoxy composition.
Before starting work, it is recommended to spread all the parts on a flat surface and conduct a "dry assembly" without glue, which will help to identify possible inconsistencies and adjust the dimensions before the materials are spoiled.
☑️ Readiness for work
Technology of manufacturing and amplification of transom
The build-up process begins with the removal of the standard transom board, carefully disconnect it from the cylinders, trying not to damage the slings and mounting elements, and if you plan to completely replace the old board, you can use the old one as a template to cut a new blank from thicker plywood.
The parts should be sawed out with a tolerance of 2-3 mm for subsequent grinding. Once the desired shape is obtained, the edges are carefully treated with sandpaper. epoxyIt is a soil that fills the pores of wood.
⚠️ Warning: Never use polyurethane adhesives or mounting foam for transom gluing – they do not provide the necessary rigidity and water resistance for an outboard motor load.
To reinforce the structure, a layer of glass-fiber-soaked resin is applied to the inside of the transom, which is repeated 2-3 times, creating a durable composite material. Between the layers, you need to withstand the time specified in the resin instructions, but not allow the previous layer to be completely polymerized for better adhesion.
The secret to perfect impregnation
To soak the fiberglass evenly and without bubbles, use a hard brush with a short pile and trampling movements. The air bubbles are pierced with a needle or driven out with a roller.
Protection from moisture and finishing
Wood, even the best quality, is a hygroscopic material. Without reliable protection, water will eventually get in, causing swelling and rotting. So the waterproofing step is critical to the durability of your boat.
After the reinforcement layers dry completely, the surface of the transom is grinded to smoothness, then the finish layer is applied to epoxy resin or specialized paint for boats, special attention is paid to the entry points of the fasteners and joints.
The main stages of protection include:
- 🎨 Apply 2-3 layers of varnish or paint to protect against UV radiation.
- 🔩 Installation of brass or stainless bushings in fastening holes.
- 🧪 Treatment of the ends of the transom with an additional layer of sealant.
You can use additional protection for transpool It's made of dense PVC fabric that is put on a board before being placed in the boat, and it creates a double barrier to water, and it protects the sides from friction against the hard surface.
High-quality sealing of the ends and holes under the fastener is more important than the thickness of the layers on the plane, since water penetrates through unprotected edges.
Installation and testing of the design
Installation of reinforced transom in cylinders requires care. Make sure that all slings are stretched evenly, and the board itself is perpendicular to the diametrical plane of the boat, skewed will lead to uneven load and can cause the boat to roll.
Once the engine is installed, make a visual inspection of the gaps between the transom and the cylinders. If necessary, put rubber gaskets. Before the first step into the water, it is recommended to conduct a static test: secure the boat on the shore, hang the engine and try to loosen the transom, simulating the load.
When you're in the water, you should be moving at low speed, listening to outside sounds and watching the behavior of the stern. The absence of creaks, backlashes and deformations indicates that you've done the right job. Regularly check the condition of the fasteners after each fishing.
Can you build up a transom without taking it off the boat?
Theoretically, this is possible, but it's not recommended that the gluing and sealing quality in tight conditions will be low, which will cause the unit to fail quickly, and it's better to dismantle the transom for full processing on all sides.
What is the maximum weight of the motor will withstand the reinforced transom?
When using plywood thickness of 25-30 mm and high-quality reinforcement fiberglass, the design is able to withstand motors weighing up to 60-70 kg. However, it is important to take into account not only the weight, but also the propeller thrust, which creates the main effort to tear off.
Do I need to remove the old paint before building?
Yes, if you build up an existing board, the old coating must be completely removed to a clean tree, and the adhesion of new layers of epoxy to the old paint will be weak, which will lead to the layering of the pie under load.