Inflatable swimming equipment often requires upgrading, especially when standard factory equipment no longer meets the growing demands of the owner. transmessorThe 5 centimeter increase in the height of the transom board is not just a cosmetic change, but a serious engineering task requiring an understanding of the hydrodynamics and properties of materials.
The main reason boat owners take this step is because they change the angle of the trim when they're moving, because if the engine is too sunken, the stern sags, the boat draws water and loses speed, and the fuel consumption rises rapidly. graffiti Or build-up of the main shield allows you to put the engine's lower unit in the optimal position, providing a way to planing at lower speeds, and in this material we will analyze all the nuances of the process so that you can get the job done efficiently and safely.
Design analysis and selection of materials for modernization
Before you start to take up tools, you need to study the design of your boat in detail. PVC boats from different manufacturers use different types of mounting of transomach boards, from simple pockets to complex systems with metal profiles. transom board In your boat, it can be removable or pasted, and the way you lift it depends on it, so if it's removable, it's easier to make a new part or a stretcher, and if it's glued into cylinders, you'll need to work with adhesive seams.
The key element here is the material of the insert itself. Standard plywood used in the factory is usually 9 or 12 mm thick and covered with special enamel. To build height, you will need a material similar in density and moisture resistance. plywood The FFS brand, which has a high moisture resistance and the strength of gluing veneer, is unacceptable to use conventional construction plywood, as it will quickly dissipate under the influence of water.
The most important factor in choosing wood is its weight, the extra weight on the stern can negate all efforts to improve performance, so when choosing a material for insertion that is 5 cm high, prefer lightweight but durable wood varieties or composite materials. Wood density It must be balanced with the requirements for strength to withstand vibrations and loads from the operation of the motor.
Geometry calculation and drawings
The accuracy of the calculations at this point determines the success of the entire operation. The 5 centimeter lift of the transom is the change in the center of gravity and the geometry of the aft. You have to consider not only the vertical size, but also the angle of inclination. transom-angle For most boats, PVC is 10-15 degrees, and when building up the board, it is important to keep this parameter or adjust it for a specific engine.
To do this, you'll need to take precise measurements from your existing trans board. Measure width, height and, most importantly, thickness. If you're planning on making a wedge insert, you'll need to do the calculations to within millimeters. A few millimeter errors can cause the engine to skew and unevenly distribute the load on the engine. stringer and mounts.
It is recommended to create a preliminary drawing or a template from cardboard, which will allow you to "try on" the future design and assess its impact on the balancing of the boat. When designing, note that the upper edge of the new transom must be flat to ensure that the lower unit engine fits tightly throughout the area.
Before starting work, take a picture of the current position of the motor and transom from different angles, which will help you visually assess the changes after the upgrade and, if necessary, return to the original parameters.
Tools and consumables
The quality of the work depends on the toolkit you use, and you'll need a set of specialized equipment to work with plywood and glue, and the main tool will be an electric jigsaw with saws for clean cutting, which will avoid chipping on the edges. plywoodAlso, a grinding tool is needed to treat the edges and create a smooth surface.
Special attention should be paid to adhesives. To connect the wooden elements and glue them to PVC fabrics or an existing board, special two-component polyurethane adhesives are used. The usual "moment" or silicone sealants will not work here, because they will not provide the necessary strength and elasticity of the seam. You will need to activator And a degreaser for surface preparation.
Below is a table with a recommended list of materials and tools needed to complete the work:
| Name | Appointment | Features of choice |
|---|---|---|
| Plywood FSF 12-18 mm | Main material of the insert | Choosing without knots and voids |
| Polyurethane glue | Sticking and sealing | Two-component, for PVC |
| Sandpaper | Grinding edges | Grain 80, 120, 240 |
| Degreaser | Surface preparation | Acetone or special solvent |
| synthetic brush | Applying glue | Hard bristles |
Don't forget personal protective equipment. Chemicals require gloves and a respirator. Solvents and activators can be toxic, so all work should be done in a well-ventilated room or outdoors.
☑️ Checking readiness for work
Technology of manufacturing and installation of insertion
The fabrication process begins with marking and cutting the material. Using a previously prepared template, transfer the outlines to a sheet of plywood. Cut with a small margin, which will then be removed during grinding. It is important that the ends are flat and perpendicular to the plane of the board, unless otherwise provided by the design of your boat. Geometry of detail It has to be perfect.
The next step is to prepare the surface, and all the glued areas must be thoroughly cleaned with sandpaper to remove the gloss and create roughness, which will improve adhesion, after machining, the surfaces are degreased, and the adhesive is applied according to the manufacturer's instructions, usually by applying a layer on both surfaces, drying to a stick, and applying a second layer with a hardener.
⚠️ Attention: When gluing large areas of plywood and PVC, it is important to avoid the formation of air bubbles. Smooth each layer of glue with a roller as you move from center to edge. Disrupting the drying technology between layers will lead to loss of strength of the connection.
If you make a single squirrel board of new height, the process is similar, but requires more precision when you dock the layers. Plywood layers are adhesive and compressed until they are fully polymerized. Drying time can vary from 24 to 48 hours depending on the ambient temperature. polymerization It's got to go through a full cycle.
Nuances of work with two-component adhesives
The lifespan of the mixture after adding a hardener is only 15-20 minutes at +20 ° C. Mix the glue in small portions immediately before applying. If the glue begins to thicken in the jar, you can no longer use it - it has lost adhesive properties and will become brittle.
Finishing and waterproofing
Once the adhesive seam is completely dried, you have to finish the finishing, plywood cuts are the most vulnerable place to get moisture in. Even the FF plywood requires additional protection for the ends, using a special wood putty for outdoor work or an epoxy resin that thoroughly smears all the sections.
The painting phase follows. To protect against UV and mechanical damage, the transom is coated with several layers of yacht lacquer or special boat enamel. The coating color is usually matched to the color of the cylinders or left in black/gray. It is important to apply a minimum of 2-3 layers with intermediate grinding to create a strong solid surface. shield-film.
Pay special attention to the places where the transom is attached to the boat. If you have built up an existing board, check the reliability of the mounts. Bolts or screws should be made of stainless steel brand AISI 316 to avoid corrosion in salt water. It is recommended to treat the thread joints with a fixing composition so that the vibration of the motor does not weaken them during operation.
The waterproofing must be absolute. Any microcrack in the paint layer can be the beginning of the destruction of wood. Therefore, after drying the paint, it is recommended to conduct a visual inspection in bright light.
High-quality waterproofing of ends and anchorages is more important than the thickness of the plywood itself, and it is through the unprotected edges that water penetrates inwards, causing stratification and decay.
Testing and adjusting the angle of the differentiator
Installing a modernized transom is only half the battle, and after installation, you need to run a test run on the water, go out in calm weather and at a safe distance from the shore, the primary task is to check the tightness of the seams and the reliability of the attachments under load, visually assess the position of the boat on the water: how the stern has changed, whether the nose is too upward.
Now we need to set up angle. When you lift the transom, you change the application point of the engine's thrust. Try changing the position of the lower unit using the available holes on the motor bracket. Your goal is to find a position where the boat goes smoothly without burrowing or lifting it too high. The optimal position is when the sole of the lower unit is parallel to the bottom of the boat or slightly raised (by 1-2 degrees).
During the tests, pay attention to the behavior of the boat in bends and in choppy conditions. A raised transom can change the sensitivity of the steering wheel. If the boat has become too prowling or, conversely, has become sluggish to the steering wheel, you may need to adjust the height or install water fittings on the lower unit.
⚠️ Warning: For the first exits after the upgrade, avoid sharp accelerations and sharp turns at high speed. New specifications of the vessel require addiction and possibly additional adjustment of the position of the engine.
Possible problems and ways to solve them
Unforeseen difficulties can arise in the process of modernization. One of the common problems is the lack of rigidity of the structure. If after installing the boat at 5 cm, the transom begins to walk under the weight of the engine, this indicates that the insert thickness is not calculated correctly or the use of poor-quality plywood. reinforcement Or a scarf on the sides.
Another problem is imbalance: a raised center of gravity at the stern can make the boat less stable in the parking lot or when moving against the wave, in which case it may be necessary to redistribute the load in the bow or install additional inflatable sections to compensate for buoyancy.
If you notice adhesive dissection or cracking, stop using immediately, which means that the adhesive you choose has not been able to withstand the dynamic load, you have to dismantle the insert, clean the surface thoroughly and glue it again using a better quality. adhesive Or by increasing the bonding area.
What to do if the plywood has started to collect water?
If you find that moisture has appeared inside the plywood (dark spots appeared, weight increased), you must immediately remove the transom, dry it in a warm dry room and re-soak the ends with epoxy. You can not operate the "sick" plywood - it will lose strength.
Frequently Asked Questions (FAQ)
Can I raise the transom by 10 cm or more?
Theoretically, it can, but it requires a serious engineering calculation: a rise of more than 5-7 cm significantly shifts the center of gravity and may require a change in the design of the cylinders themselves or the installation of more powerful stringers. For a conventional tuning 5 cm is a reasonable maximum.
Does the rise of the transom affect the manufacturer's warranty?
Yes, any interference with the design of the boat, including the replacement or modification of the slingboard, automatically voids the factory warranty.
Which glue is better to use for plywood and PVC?
The best results are shown by two-component polyurethane adhesives (for example, Kleyberg, Texakol or specialized boat adhesives). They provide high strength and elasticity of the seam, which is critical for inflatable structures.
Do I need to change the mounts (bolts) when replacing the transom?
Replace all the fasteners with new ones made of stainless steel, and old bolts may have been corroded or fatigued by metal, and reusing them with a new, heavier design is risky.
How much does the glue dry at a temperature below +15 ° C?
At temperatures below +15 ° C, the polymerization process of polyurethane adhesives slows down significantly or may stop altogether. Drying time can increase by 2-3 times. It is recommended to work at a temperature not lower than +18-20 ° C.