Owners of PVC boats, especially low-pressure inflatable floor (LDP) models or budget options with plywood inserts, often notice that the standard board begins to “walk” under the weight of a heavy motor, not only reducing the efficiency of the control, but also creating a real safety threat, since excessive vibration can lead to damage to cylinders or even loss of the engine in the water.
The solution to this engineering problem becomes grazing-treeThis is an additional rigid structure attached to the sides or bow of the vessel, which allows you to spread the load, while maintaining the tightness of the main cylinders and providing an ideal vertical for the lower unit engine. Unlike the standard board, the remote design takes over the entire weight of the power unit, allowing you to use more powerful engines without the risk of deformation of the aft part.
In this article, we will discuss in detail why there is a need for modernization, what materials are best suited to create a reliable support and how to properly conduct installation work yourself. You will learn about the nuances of calculating the height of the suspension and how to strengthen the structure so that your boat served for many years without complaints.
Why do you need an extra transom and in what cases it is needed
The main reason for installing the extra transom is because of the physical properties of the inflatable elements of the boat. Even the highest quality PVC reinforced cylinders have a certain degree of elasticity, which, when loaded, turns into unwanted mobility. outboard Weighing more than 30-40 kilograms per board, it begins to bend, and with it the back of the cylinders also flexes, which causes the engine's lower unit to lean into the cockpit, changing the angle of attack of the propeller.
The consequences of this tilt can be critical. hydrodynamic efficiency: the boat gets worse at planing, increases fuel consumption and drops top speed. Second, there is a risk of flooding the transom compartment with water through splashers or simply through the upper edge of the board during the wave. Third, constant vibration and friction of the engine against the soft side can lead to rapid wear of the material and the appearance of microcracks.
⚠️ Warning: Operating a boat with a skewed engine is prohibited by safety regulations. A lower unit tilt of more than 5-10 degrees from the vertical can cause the cooling system to overheat and cavitate the propeller.
The remote transom solves these problems by moving the force point, the design relies directly on the rigid elements of the boat frame (stringers, cans), or has its own attachment system to the sides above the waterline, without affecting the soft part of the transom. NDMAThe stern liner is often missing or thin, and the remote element is also necessary if you plan to use high-power motors, which the boat manufacturer formally allows, but the standard transom for them is weak.
Design features and types of remote transverses
The engineering of the water-engines has given rise to many design options for the remote transoms, but they are all divided into several basic types of attachment and geometry. Understanding these differences will help you choose the optimal solution for your model of the boat. The key parameter here is how to transfer the load from the motor to the boat hull.
Type one: frame-frameThey're an U-shaped or rectangular frame that covers the stern of the boat outside, and they're mounted through special eyelets or straps to the sides, and they have the advantage of being versatile, adaptable to different boats, but they require very careful tuning of tension so that the frame doesn't slide down under the weight of the motor when it's moving.
Type two: internal reinforcement panelsThese are rigid sheets (usually made of plywood or composite) that are mounted inside the cockpit parallel to the normal transom, but with the removal overboard through special slots or mounts. They rely on the bottom or special supports, this option provides maximum rigidity, since the motor hangs on a rigid ligament, but requires more complex installation and can take up useful space in the cockpit.
- 🛶 Frame transists: easy to remove, versatile, but require control of tension of fasteners.
- 🔩 Interior panels: provide monolithic rigidity, ideal for speedboats, but more difficult to install.
- ⚓ Combined systems: use elements of both types to distribute the load over the maximum area.
The important aspect is the fabrication material. The most common solution is the fabrication material. plywoodIt's a classic that's been tested for decades, but modern technology offers alternatives: carbon fiber composites or durable engineered plastics, lighter plywood and not afraid of water at all, but they cost a lot more, depending on the budget and weight requirements of the entire structure.
Selection of materials and tools for manufacturing
If you've made the decision to make a remote transom, you need to be very responsible about the materials you choose. The aqueous environment is aggressive, and the loads on the structure are dynamic, with vibrations and wave shocks. Errors in choosing raw materials can lead to rapid destruction of the product directly on the water.
The basis of the design is most often the plywood brand. FC or FSFThe PFS brand (with phenolformaldehyde glue) is considered more moisture resistant, but the adhesive is toxic, so it is not always recommended for interior work in closed cockpits without careful insulation. FC (on urea glue) is safer, but requires better waterproofing, plywood should be at least 12-15 mm thick, and for powerful motors - up to 18-21 mm.
Secrets of plywood processing
For maximum protection of the ends of the plywood, you need to impregnate epoxy resin in several layers to the main coating, since it is through the sections of the fibers that water penetrates the fastest.
The protective coating uses fiberglass-reinforced epoxy resin, which creates a strong shell that keeps water out and protects the tree from mechanical damage. Alternatively, you can use special yacht varnishes and paints, but epoxy + fiberglass gives the best result in the ratio of price / quality / durability.
The fasteners must be made of stainless steel (AISI 304 or 316), ordinary galvanized fasteners in salt water or even fresh water, with constant contact with moisture, will rust in one season, bolts, nuts and washers should be of high strength.
- 🔨 Drill and drill on wood and metal.
- 🪚 An electro-cloak or circular saw for cutting.
- 🖌️ Hands and rollers for applying resin and varnish.
- 📏 Roulette, coal and level for marking.
Step-by-step instructions for installing a remote transom
The installation process requires precision and precision. Before work begins, the boat must be fully pumped to operating pressure to simulate real-world operating conditions. Any measurements made on the boat lying on the ground will be incorrect due to the change in the geometry of the cylinders.
The first step is to fit and mark. Apply the transom to the stern of the boat. Make sure the top plane of the transmolant is at the correct level relative to the bottom of the boat (usually 0-25 mm above the conventional bottom line extended to the transmolator). If the transmolator is too high, the boat's nose will linger, if low, the boat will dig water with its nose.
☑️ Plan for the installation of the remote transom
Then there's the drilling and installation of the fixture, and if the design involves a through-mounting through the sides, the bolts' passageways are necessarily reinforced. loovers Or special linings made of a durable material (Teflon, thick leather, rubber) that prevent PVC tissue from rupturing around the hole under load, the bolts are tightened through wide washers to distribute pressure over a large area.
Once the main body of the transan has been installed, you need to check its rigidity. Try leaning on it with all your weight, swinging from side to side. The structure should not have backlashes. If you use additional supports to the bottom (for boats with a hard floorboard bottom), make sure that they fit tightly and are fixed so that they do not scratch the floorboard when vibrating.
⚠️ Note: When drilling holes in the sides of the boat, use only special PVC drills so as not to damage the reinforcing cord. Overheating of the fabric during drilling is unacceptable.
Adjustment of engine height and tilt angle
Installing a remote transom is only half the battle; it's critical to adjust the engine position correctly; the height of the engine suspension determines how deep the anti-cavitation plate is; for most planing boats, the optimal position is when the plate is 0-25 mm below the bottom line.
If the motor is set too high, the propeller will capture air (cavitation), especially when cornering or starting abruptly, resulting in loss of traction and overheating of the engine. If it is too low, water resistance will increase, the boat will lose speed, and the engine will operate inefficiently. Adjustment is done by selecting the thickness of the gaskets between the transom and the motor or changing the attachment point of the transom itself.
Use a transporter or digital angler to check the inclination angle of the lower unit. The optimal angle for most PVC boats is 2-4 degrees from the vertical (nose up).
And you also have to consider this phenomenon called rolling on board. Under the weight of a heavy motor, the boat can sway. A pull-out transom, if it's made symmetrically and rigidly, helps to align the stern, but sometimes you need to balance the load in the bow or on the opposite side. The tilt angle is checked on the water: when you get on plane, the boat must go smoothly, without yawing and excessive splashing.
To fine tune it, you often have to do a series of test swims. Write down the changes: add 5 mm gasket — the speed dropped, remove — cavitation began. By eliminating it, you will find the middle ground for your boat-motor-propeller bundle.
Comparison of specifications of different enhancement options
To make a final decision on the design, it is worth comparing the main parameters of different approaches to strengthening the transom. The table below provides comparative data for the three most popular types of solutions.
| Parameter | The regular transnet | Frame-sized | Inside panel |
|---|---|---|---|
| Max, engine power. | 15 hp. | up to 30-40 l.4. | up to 50+ hp. |
| Structure weight | Minimum | Medium (5-8 kg) | Tall (10-15 kg) |
| Difficulty of installation | Missing. | Low. | High. |
| Impact on the cockpit | It doesn't. | Minimum | Takes up space. |
As you can see from the table, panel It's the most powerful solution that can withstand the weight of large four-stroke engines, but it weighs the boat down significantly and reduces the usable volume. Frame designs are a middle ground, suitable for most hobbyists using motors in the 15-25 hp range.
Do not forget about the cost. Manufacture of a remote transom yourself will cost 3-5 thousand rubles (materials), while factory analogues from well-known brands can cost from 10 to 25 thousand rubles. At the same time, a homemade version made with the observance of technology often exceeds factory aluminum frames in rigidity and reliability of fastening.
The choice of the type of transom should be based on the power of your motor: up to 15 hp is enough regular, 15-30 hp - you need a frame, over 30 hp - only a rigid internal panel or factory gain.
Frequently Asked Questions (FAQ)
Can a takeaway transom on inflatable floor boats (BBD) be used?
Yes, but with limitations. On NDND boats, the regular transom is often just a soft fabric with a pocket for the board. The installation of a remote transmutant is even more necessary here than on paiola boats. However, the attachment should be very carefully so as not to damage the valves and seams of the inflatable floor. It is better to use structures that rely on the sides, not on the bottom.
How much will the weight of the boat increase after the reinforcement is installed?
Weight depends on the materials. A lightweight frame structure made of aluminum or thin plywood will add 4-6 kg. A massive plywood panel with epoxy can weigh 10-12 kg. This is something to consider if you plan to often carry a boat alone. However, this weight is offset by the possibility of using a more powerful and heavier motor that would still have to be carried.
Do I need to remove the remote transom while transporting a boat?
Most of the time, yes. A folded transom takes up extra space and can damage the fabric when it's put in a bag. Frame structures are usually easily dismantled in 5-10 minutes. Internal panels are also better removed so they don't rub against cylinders when deflated. Except for boats that are kept inflated in a garage.
Will the remote transom withstand a four-stroke motor?
Yes, if the design is correct. Four-stroke engines are heavier than two-stroke engines of similar power, so the safety margin of the transom should be increased. It is recommended to use plywood at least 18 mm thick and increase the support area on the sides of the boat. For motors over 20 hp, the use of a remote transom is a prerequisite for safety.