In the era of total digitalization and widespread GPS-navigators, trying to equip their boat with the latest technology, many aquatic motors make a fatal mistake, neglecting classical devices. boat's compass It is the only autonomous navigation device that does not require external power, satellite signal or connection to the onboard network. Electrical failure on the turbulence or discharge of the GPS receiver battery should not be a factor that jeopardizes the safety of the crew, because it is the magnetic needle that will indicate the right path to shore when the electronics are silent.
Choosing the right appliance is not just about buying an accessory, but an investment in safety that requires an understanding of the principles of operation and operating conditions. Sea compass It differs from a tourist or car counterpart in a number of design features designed to compensate for constant swaying, body vibration and aggressive exposure to salt water. Incorrectly selected model can give critical errors, which in poor visibility or navigation in the alignments will lead to dangerous situations.
In this article, we will discuss in detail how to choose a reliable device for your boat or boat, consider the nuances of installation, which are often ignored by amateurs, and learn how to eliminate magnetic errors. Understanding the physics of the process will help you feel confident at the helm even far from civilization, where you can not recharge your gadgets or receive a signal from satellites.
Principle of operation and boat's compass
The basis of any magnetic compass is the sensitive element. pot-pocketIt's a cartridge that rotates freely around a vertical axis and is held horizontally by a balancer, and it's got a magnet or a system of magnets that interact with the Earth's magnetic field, always pointing towards the magnetic north pole. boat-compass equipped with a complex damping system (quenching oscillations), which allows the shooter to calm down even with heavy chop.
The body of the device, called a boiler, is filled with a special liquid, usually a mixture of alcohol and distilled water, which has two important functions: it extinguishes the inertial vibrations of the potato when rolling and lubricates the supports, reducing friction. Deviation This is a deviation of the compass readings from the true magnetic meridian caused by the magnetic field of the boat itself (metal hull, engine, electronics), and it is to combat its consequences that complex boiler designs are created.
Modern models often have red lights to keep the steering wheel from disturbing night vision and to adjust the brightness. It is important to understand that any magnetic device is subject to temperature expansions, so the design includes a compensation tank (extension chamber) to prevent the boiler from rupturing or the formation of air bubbles when the temperature changes.
- 🧭 pot - a sealed case filled with liquid in which the potato is placed.
- 🧭 Potatoes. - a moving part with a degree scale and a magnetic system.
- 🧭 Pelengator - an additional device for removing azimuths to remote objects (optional).
- 🧭 Correctors Magnetic bars or balls to eliminate deviation.
⚠️ Warning: Never place a compass near powerful electromagnetic radiation sources such as radars, VHF radio antennas, or powerful audio speakers. Even brief exposure to a strong field can overmagnetize the cardboard or create a permanent error.
Why does the liquid in the compass change color?
Over time, the fluid in the boiler may become cloudy or change color due to oxidation of internal components or the penetration of moisture through microcracks in the seals. If you notice bubbles or a change in the color of the liquid, the compass requires professional maintenance or replacement, since the accuracy of the readings is already impaired.
Criteria for choosing a compass for boat and boat
When choosing a navigation device (first of all), you need to consider the type of boat and its operating conditions. calmness If you own a displacement yacht or a heavy cruise boat, the accuracy of the scale and the quality of materials that are resistant to long-term ultraviolet exposure become a priority.
The size of the pot is not the least: the larger the diameter of the card, the better the reading accuracy, but the more space is required for installation. Standard dimensions range from 80 mm to 150 mm or more. Compass for boat Small size (80-100 mm) is often chosen as an auxiliary or for installation on small craft where space is limited, but for basic navigation it is better to focus on models with a diameter of 110 mm.
Pay attention to the type of attachment: there are models for installation on the bulkhead (bulkhead mount) and on the deck/top (flush mount or binnacle mount). bulkhead compasses often have an inverted scale or (specific) design, allowing readings when the device is installed vertically on the cockpit wall.
Materials must be of exceptionally high quality: brass, bronze or high-quality composites that are resistant to corrosion. Cheap plastic models can be deformed by sunlight, which will lead to jamming of the potatoes. Waterproofness The body should be absolute, since the penetration of even a small amount of off-shore water will disrupt the balancing and lead to corrosion of the internal elements.
Installation rules and installation sites
The right installation is 90% of the success in navigation accuracy, and the basic rule is that the compass should be as far away from ferromagnetic materials and current sources as possible. Minimum distance The engine, steering gear, radio equipment and large metal objects should be at least 1 meter, and ideally 1.5-2 meters. Neglecting this rule will lead to a huge deviation, which will not be compensated by regular proofreaders.
The installation site should ensure that the helmsman's scale is visible in any position of the vessel, but the instrument should not interfere with the control. Often compasses are installed on the bulkhead in front of the helm station or on a special bracket on the roof of the wheelhouse. horizontality installation: if the compass is skewed, the potato will sway, which will increase friction and lead to sticking.
For bulkhead models, you need to strictly observe the orientation with respect to the diametric plane of the vessel. The axis of 0-180 degrees on the boiler should be parallel to the axis of the vessel. If the compass is installed with a deviation even of several degrees, this will require constant correction or mechanical adjustment, which is not always possible on the go.
- 🔨 Avoid installing directly over the engine or generator.
- 🔨 Do not place the device near the stereo speakers or subwoofer.
- 🔨 Make sure there are no hidden metal bulkheads or tanks under the installation site.
- 🔨 Provide access to proofreaders for possible deviation adjustment.
☑️ Verification of installation site
⚠️ Warning: When installed on a (plastic glass) bulkhead, make sure that there are no laid power cables or steel reinforcement elements inside it in the assembly area that can shield the magnetic field.
Magnetic deviation and its elimination
Deviation is the most insidious phenomenon in navigation, which is the deviation of the compass from the magnetic meridian under the influence of the magnetic field of the boat itself. The metal hull, engine, anchor chain and even tools lying nearby create their own magnetic fields that distort the readings. Deviation rate may vary depending on the course of the vessel, reaching maximum values on (some) rhumbs.
The process of eliminating deviation is called compensation, and it's done with built-in correction magnets. By rotating the proofors screws (usually two to eliminate the semicircular deviation in the N-S and E-W courses), you can minimize the error. However, you rarely completely remove the deviation, so after compensation, you compile the error. deviation (a plate of residual deviation), which should always be at the hand of the navigator.
To decouple a compass yourself, you need to go out into calm water and choose two tailored signs with a known true bearing or use a 360-degree turn, comparing the readings to GPS (taking into account magnetic declination), the process requires patience and accuracy: turns are performed slowly so that the potato has time to calm down.
| boat's course (Compass) | Magnetic Course (Magnetic) | Deviation (Deviation) | Amendment |
|---|---|---|---|
| 0° (N) | 358° | +2° (E) | Add in |
| 90° (E) | 93° | -3° (W) | Subtract. |
| 180° (S) | 181° | -1° (W) | Subtract. |
| 270° (W) | 268° | +2° (E) | Add in |
It can change after a long stay on the same course, after transportation on the trailer (especially if there was a bridge fitting or power line nearby), or after installing new equipment on board. The deviation test shall be carried out at the beginning of each navigation season. and after any major changes in the equipment of the boat.
The deviation depends on the course of the vessel and changes when the direction of movement changes, so the table of amendments is mandatory for accurate navigation.
Maintenance and care of navigation devices
The boat's compass is reliable, but it requires regular attention and care. The main enemy is the formation of air bubbles in the boiler liquid. If you notice bubbles, they must be removed, because they interfere with reading and can disrupt balancing. Some models provide a special plug hole through which you can add a special liquid (a mixture of alcohol and distilled water) or ether to displace air.
External cleaning should be done only with fresh water and soft fabric. The use of aggressive chemical solvents, gasoline or acetone is strictly prohibited, as they can damage seals, cloud the glass or destroy plastic elements of the boiler. Lubricant Friction parts are usually not required, since the device works in a liquid medium, but external hinges and fasteners should be checked periodically for corrosion.
In winter, if the boat is kept in an unheated room, the compass is better removed and stored at room temperature. Although the liquid inside does not freeze at normal winter temperatures (alcohol prevents water from freezing), sudden temperature changes can lead to condensation inside the boiler or leakage.
- 💧 Regularly wipe the glass of the boiler with a soft wet cloth from salt deposits.
- 💧 Check the tightness of the body and the condition of the sealing rings.
- 💧 Watch for the absence of bubbles in the liquid.
- 💧 Do not expose the device to shocks and strong vibration during transportation.
⚠️ Attention: If flakes, mud or it becomes opaque in the compass liquid, the device loses its leakage. The operation of such a compass is unacceptable, since the viscosity of the liquid has changed, and the potato will be delayed or sticky.
To prevent the formation of bubbles in the off-season, store the removed compass in an upright position in a cool place, avoiding direct sunlight, which heats the liquid and causes its expansion.
Frequently Asked Questions (FAQ)
Why does the compass show up wrong after installing a new speaker?
The speakers contain powerful permanent magnets that create a strong local magnetic field, and this field interacts with the compass map, causing significant deviation or even magnetization, you need to remove the speaker at least 1-1.5 meters from the compass or use shielded models of speakers, although this does not give a 100% guarantee.
Can I use a car compass on a boat?
It is strongly discouraged: Car compasses are not properly damped (liquid or pendulum) and are not protected from moisture and salt spray. On water where constant pitching, the needle of the car device will rush randomly, making navigation impossible, and the body will quickly fail due to corrosion.
How often should I check for deviation?
At least once in the navigation season, and after a long stay in one place (more than a month), after a lightning strike, after transporting a boat for long distances in a trailer or after installing any new electrical or metal equipment on board.
What to do if the liquid in the compass is completely leaked?
You can try to refill it yourself if the model allows access using a mixture of ethyl alcohol and distilled water (a ratio of about 45:55 or 50:50 for freezing and the desired viscosity), but it is better to contact a specialized workshop or replace the device, as the imbalance of the liquid is critical.
Does the color of the boat hull affect the compass readings?
The color of the paint (gelcoat) does not affect the magnetic field. However, if the paint or gelcoat (especially in inexpensive or specific coatings) uses ferromagnetic pigments or fillers, this can create a slight deviation. This effect is usually negligible compared to the engine or body structures, but when installing a compass on a top light (mast) of fiberglass, this should be considered.