Installation of navigation electronics on a light alloy floater always involves a number of specific difficulties that are not present when working with plastic or fiberglass. Aluminum transom has high thermal conductivity and rigidity, which requires a special approach to the choice of adhesives and fixation methods. Incorrect installation can lead not only to the loss of expensive equipment. transducer during movement, but also to violation of the tightness of the body, if the method with drilling is chosen.
Metal boat owners often face a dilemma: drill hard metal or trust a chemical compound. Statistics show that more than 80% of installers prefer contactless methods because they maintain the integrity of the structure and allow easy dismantling of equipment when selling a boat. In this article, we will examine all the nuances of surface preparation, bracket selection and adjusting the radiation angle to get the perfect picture on the screen.
Selection of installation site and surface preparation
The first priority is to determine the optimal zone on the transom where the flow of water will be most laminar. Air bubbles formed at the cheekbones or in the area of operation of the engine can interfere with the ultrasonic signal, making readings. sonar You need to visually inspect the transom for rivets, seams or irregularities that can create turbulence.
Preparing the aluminum surface requires careful degreasing, because even a microscopic layer of oil or oxide drastically reduces the adhesion of the sealant. Use acetone or specialized solvents to remove factory lubrication and dirt.
To maximize the strength of the joint, it is recommended to do a light abrasive machining of the mounting area. Use P80-P120 grain sandpaper to create micro scratches that will anchor the adhesive compound. Don't overdo it by removing too much metal, your goal is to increase the contact area at the micro level.
⚠️ Attention: Never use gasoline or kerosene for degreasing, as they leave a greasy film that is invisible to the eye, but critical for glue.
Fixing methods: drilling against glue
The debate about how to securely fix the sensor, mechanically or chemically, has been going on for decades, and mechanically fastening through the transomic through holes is considered classic, providing physical protection against failure even when the glue is completely cured. stainless bolts and mandatory sealing of holes to prevent electrochemical corrosion.
The adhesive method, often called “through-hull” or simply a sealant landing, is gaining popularity because of its simplicity. Modern polyurethane and silicone compounds are able to withstand vibration loads and impacts on water at speeds up to 100 km / h. The main advantage here is the lack of holes in the hull, which is especially true for thin-walled aluminum boats.
Why is aluminum difficult to glue?
Aluminum is highly thermally conductive, so the adhesive seam experiences constant thermal expansions and compressions, and the oxide film on the metal surface is chemically inert, requiring special primers or aggressive adhesives that can penetrate metal micropores.
When choosing a method, consider the frequency of removal of the boat from the water. If you often pull the boat ashore for inspection or storage, a mechanical bracket may be more convenient, since it allows you to quickly unfasten the sensor. For boats standing on the water all season, the adhesive method is preferable because of its reliability and aesthetics.
Instructions for installation on adhesive sealant
The process of installing the sensor without drilling requires strict adherence to the technology, otherwise the risk of equipment loss increases many times. The first step is to fit the sensor site into the selected place without glue, to make sure that there is a tight fit and no gaps. The surface must be dry, warm and clean.
Put a thick layer of sealant on the sensor mounting pad, avoiding air bubbles, press the sensor against the transom and hold it with paint tape or load until the initial grasp, and it is important to squeeze out the excess glue so that there are no voids under the sole that can distort the signal.
☑️ Checklist for installation
The time of full polymerization of most marine sealants is from 24 to 48 hours at a temperature of +20 ° C. Do not rush to launch the boat before the time, as water can wash the undried composition from under the sole.
| Type of sealant | Seizure time | Max, speed. | Resistance to UV |
|---|---|---|---|
| Polyurethane | 2-4 hours | up to 120 km/h | High. |
| Silicone (acid) | 30-60 minutes. | up to 60 km/h | Medium |
| MS polymer | 1-2 hours | up to 100 km/h | High. |
| Epoxy glue | 5-8 hours | up to 80 km/h | Low (yellowish) |
Use of clamping brackets and rods
For those who don't trust chemistry or who own a boat temporarily, removable brackets are a great solution, and they attach to the top of the transom using screw clips and don't require drilling or waiting for the glue to dry, and they often have a quick-removal mechanism that allows you to remove the sensor when you approach shallow water.
The main disadvantage of the rod mounts is their vulnerability to impacts on obstacles and the possibility of displacement when vibrating strongly. To minimize the risks, use models with rubber clamps that protect the side of the boat from scratch and provide better friction. Regularly check the tightening of the screws before each outing.
There are also hybrid options where the bracket is glued to the transom, but the sensor itself has the ability to quickly unfasten, a compromise solution that combines the reliability of the adhesive connection with ease of maintenance. When choosing this option, make sure that the bracket lock is made of corrosion-resistant alloys.
When using a removable bracket, always extend the safety rope from the sensor to the boat hull. If the clamp screw weakens on the move, the cable will not let the expensive equipment sink.
Cable laying and connection protection
The quality of the image on the screen depends not only on the sensor, but also on the integrity of the cable track. On aluminum boats, the cable is often laid inside the board or under the banks to eliminate the risk of damage. If the wiring goes on the outside of the transom, use a corrugated tube or cable channel to protect against ultraviolet light and mechanical influences.
Pay special attention to the location of the cable entering the sensor and the head unit, which are the areas most susceptible to moisture and contact oxidation. Use shrink tubes with adhesive layers to isolate the connections. Avoid tensioning the cable, leave a small loop at the sensor itself.
To connect to the onboard network 12B or 24V, be sure to use a fuse installed in the break of the plus wire as close as possible to the battery. sonar In the case of short circuit, the wiring should be fixed with plastic clamps in 30-40 cm increments to avoid blabbering on the wave.
⚠️ Attention: Do not run the sonar cable parallel to the power wires from the battery to the motor at a distance of less than 15 cm, this will create severe interference on the screen.
Setting up the angle and testing the work
Once the sealant is installed and dry, you need to test the system on the water. The ideal angle of installation of the sensor is when its radiating surface is parallel to the bottom when the boat moves. If the boat's nose is upside down in the plane, the sensor can lose contact with water, so sometimes a small forward different is required.
From the head unit menu, select the type of sensor you have installed and the frequency of the radiation. Test at different speeds, starting at idle and gradually increasing engine speeds. Watch when there is noise or a bottom on the screen, which is the speed limit for your current installation.
A properly installed sensor should show a clear bottom and fish at maximum boat speeds without white noise stripes appearing on the screen.
If you notice a signal deterioration at high speeds, try lowering the sensor down the transom or changing its angle of inclination. Sometimes it helps to install a small deflector in front of the sensor that breaks the water flow. Experiment with the position until you get a stable picture.
Frequently Asked Questions (FAQ)
Can I glue the sensor to cold aluminum in winter?
Most sealants require temperatures above +10°C for normal polymerization, and cold metal can condense moisture, which will reduce adhesion to zero, and it is better to wait for the warm season or work in a heated room.
Which sealant is better: black or white?
The color of the sealant does not affect its adhesive properties, but it affects aesthetics. Black polyurethane is less noticeable against the background of the engine and transom, but heats up more in the sun. White or transparent silicone can turn yellow over time from ultraviolet light. The choice depends on the color of your boat.
Do I need to remove the paint at the place of gluing?
Yes, if the paint is thick or poorly maintained, the sealant must come into contact with metal or with a very strong coating, if the paint is factory-grade and quality (for example, powder), you can glue over it, slightly skinned. If the paint is old and cracking, be sure to clean it to metal.
Why does the sounder “glue” when the engine is running?
The problem is probably a poor grounding or a tip from the engine ignition system, check if the minus sonar is directly connected to the battery, not to the on-board outlet, and also make sure that the sensor cable is not located next to the motor wires.