The feed is one of the most critical areas of any swimming aid, whether it is lightweight. PVC boat This is where the main loads of power that arise when you're driving, especially if you're using an outboard motor, are concentrated, and misunderstood the design of the stern or the use of poor materials in assembling it can lead to fatal consequences on the water.
Many small boat owners underestimate the importance of tightness and rigidity of this structure, and water trapped inside a transom box can destroy a tree for years, even if it is treated with protective compounds. Rust on the fastener And plywood is just the visible part of the iceberg, which is often discovered too late when the boat begins to lose its driving qualities or gets a hole.
In this article, we will discuss in detail how modern feed is designed, what materials are best for making a transom board and how to properly perform repairs. You will learn about the intricacies of installing a motor, how to strengthen the structure and methods to prevent water leakage. The most common reason for failure of the stern is not the weight of the engine, but resonant vibrations and hydraulic shocks during the course on the wave.
Design features of the transom part
A trans, or squirrel board, is a vertical or slightly inclined plane at the back of the boat designed to hold the outboard motor. In inflatable boats, this structure is usually glued between two layers of PVC fabric, forming a rigid package. In metal and fiberglass models, the trans is an extension of the hull or welded/pasted part.
The transom angle is not a random parameter, but a carefully calculated value that affects the differentiation of the vessel. The standard angle is 0 to 15 degrees from the vertical, which allows the engine's lower unit to occupy an optimal position relative to the bottom. If the angle is too large, the boat will peck nose, and if too small, the stern will burrow into the water, creating excessive resistance.
⚠️ Warning: Never ignore factory settings of the transom angle. Unauthorized change of slope during repair can lead to cavitation of the screw and overheating of the engine at high revs.
The most important element is chunk-box This space is often used for storing equipment, but its main function is to ensure rigidity, the walls of the box must be made of moisture-resistant plywood of the FC or PSF brand, or of composite materials that can withstand constant contact with moisture without loss of strength.
Selection of material for the transaxboard
When it comes to replacing or making a new stern bulkhead, material selection becomes a safety issue. Marine plywood is traditionally used, but modern composites offer better-performing alternatives. Wood requires careful impregnation, as even moisture-resistant varieties gain moisture through cuts and fasteners over time.
Aluminum alloys, such as AMG5 or AMG6Ideal for metal boats, but their use in PVC structures is limited due to the complexity of the adhesive compound and the risk of electrochemical corrosion when in contact with water and other metals. Fiberglass-reinforced plastic composites are becoming increasingly popular due to their absolute water resistance, although they are inferior to wood in their ability to extinguish vibrations.
Consider the main advantages and disadvantages of popular materials:
- 🌲 Sea plywood: classic choice, perfectly holds the fastener, extinguishes vibrations, but requires regular check for stratification and impregnation of the ends.
- 🛡️ Glass plastic: complete immunity to water and rotting, high strength, but complex installation and high price of the material.
- ⚙️ Aluminum alloy: maximum stiffness and durability, however heavier than wood and requires insulation from PVC fabric to avoid damage.
- 🧱 Foamed PVC (composite): light and does not absorb water, but has less strength on the cut when fastening heavy motors.
When choosing a material, be sure to consider the power of the engine planned for installation. For engines up to 5 hp, high-quality plywood with a thickness of 18-20 mm will suit. For more powerful units, especially with a long leg, the thickness of the transom should be increased to 25-30 mm, or a sandwich design is used.
Technology of strengthening the feed under a powerful motor
Installing a motor with more power than the manufacturer's recommendation, or simply wanting to improve reliability, often leads to the need to strengthen the transom. Simply increasing the thickness of the board is not always effective, as the weight of the entire structure increases. cross-plate or additional power overlays that distribute the load over a larger area.
The reinforcement process begins with the dismantling of the old transom (if possible) or careful surface preparation. You need to clean the attachment sites to a clean material, degrease them and apply adhesive soil. If you are working with a PVC boat, new layers of fabric or linings should overlap the junction between the board and the balloon by at least 50 mm on all sides.
To distribute the point loads from the motor fasteners, wide washers or special metal plates are used that cover the entire mounting area, this prevents the transom material from pressing through sharp jerks or shocks to the wave, and it is also recommended to install additional stiffness ribs inside the transmolor box, if its design allows.
☑️ Tranx reinforcement
Sealing and moisture protection
Water is the main enemy of any boat stern, and by penetrating microcracks in paint or through poorly sealed fastener holes, it triggers the process of destruction, in wooden structures, it leads to swelling and rotting, in metal structures to corrosion, and in composites to stratification when frozen.
For high-quality sealing of transoms, you need to use specialized compounds. Conventional silicone is not suitable here, since it does not have sufficient adhesion to PVC and polyurethane adhesives, and can also be destroyed by the influence of gasoline and oils. The optimal choice is polyurethane sealants or special two-component mastics for boats.
Special attention should be paid to the entry points of the fasteners. Each hole should be sealed before the bolt is installed, and the bolt cap and nut should also be protected. rubber-washer or gaskets under the washers of the motor mounting, which compensate for microvibrations and prevent the formation of gaps.
⚠️ Warning: Before applying any sealant, the surface must be completely dry, and trying to seal the wet plywood will end up with water remaining inside and continuing to destroy the material from the inside.
Use a medical syringe to inject a sealant into hard-to-reach places around fasteners – this will provide deep penetration of the composition and reliable protection from moisture.
Comparative table of transom materials
To make it easier to choose the material to repair or build a new boat, we will give a comparative analysis of the main options, these parameters will help you weigh the pros and cons depending on your operating conditions and budget.
| Parameter | Sea plywood | Fiberglass | Aluminum (AMG) | PVC composite |
|---|---|---|---|---|
| Weight (kg/m2) | Medium. | Highly | Low. | Very low. |
| Moisture resistance | Requires protection. | Absolute. | High. | Absolute. |
| Strength to bend | High. | Very high. | Medium | Low. |
| Difficulty of installation | Low. | High. | Medium | Medium |
| Term of service | 5-10 years | 20+ years | 20+ years | 15+ years |
As you can see from the table, plywood It remains a compromise solution on price and ease of processing, but loses in durability. Fiberglass and aluminum are the choice for those who build a boat "for centuries" and are ready for a more complex fabrication process.
Repair and replacement of the transom board
Sooner or later, even the best food will require attention, and if you find that the trench is cruising under the load of the engine, or you hear a characteristic crunch when pressed, then the process of destruction has begun, and in the case of wood, this is often accompanied by the appearance of dark spots around the fastener or the bloating of the lacquer coating.
Replacing the transom in a PVC boat is a complex process that requires industrial hair dryer, special glue and PVC fabric skills. First, you need to carefully separate the shingle and peel the cylinders off the transom. The old board is removed, cleaned of the glue residue, and the new one is cut from the pattern. It is important to preserve the original angle of inclination and thickness of the package.
When assembling a new design, you must observe the temperature regime of gluing. PVC glue polymerizes at certain temperatures, and a violation of the technology will cause the seam to "float" in the sun or burst in the cold. After assembly, you need to conduct a test for leakage and strength before the boat is launched.
Can I increase the transom without disassembling the boat?
It is impossible to replace the board completely without disassembling, but you can install an external transom plate (hinged transom), which will take the main load from the engine, unloading the standard transom, this is a temporary or compromise solution.
Frequent errors in installation and operation
One of the most common mistakes is the pulling of the motor fasteners, which leads to crushing of the wood or deformation of the composite around the hole, which then forms a gap for water to penetrate, and the puff should be uniform and consistent with the recommendations of the manufacturer of the motor.
Another mistake is ignoring the state of the engine's lower unit, and if the screw is damaged or balanced, there are strong vibrations that are transmitted to the stern, and the constant shaking works like a jackhammer, quickly shaking even the strongest transom, and regular checks of the screw and anti-cavitation plate are mandatory.
Owners also often forget to transport. When the boat is moving in a trailer with the engine installed, the load on the transom increases many times due to road vibrations. Always use transom wheels or remove the engine for long-distance transport, if the design of the boat does not provide for reinforced mounting for transportation.
The durability of the stern of the boat depends on 80% on the quality of sealing of the fastening holes and regular monitoring of the condition of the seams, not only on the strength of the transom material itself.
How often should I check the condition of the transom?
A visual inspection is recommended before each outing, and a full probing and stiffness check should be performed at least once a season, and after each case of hard slapping on the stern of a wave or hitting an obstacle.
What is the best way to handle the ends of the plywood transom?
The best results are shown by epoxy resin with the addition of coloring paste (to control application) or specialized polyurethane impregnations for wood. Conventional olifa or paint does not provide sufficient waterproofing for conditions of constant contact with water.
Can I use conventional steel bolts?
In an aggressive aquatic environment, regular steel rusts in one season, and the rust will destroy the surrounding material. Use only stainless steel (A2, A4) or titanium fasteners.
What to do if the transom has already taken water?
You need to dry the boat immediately in a warm room, and if it's plywood, you might need to remove the lacquer, dry the board with a hair dryer, and re-soak and varnish it, and in the case of neglect, when you start rotting, you'll only need to completely replace the tanning board.