Magnatic Compass Coefficients
The compass plays a really vital role in maritime navigation. As per SOLAS Chapter 5, Regulation 19 “all ships regardless of size shall have a properly adjusted standard compass or other means, independent of any power supply to determine the ship’s heading and display the reading at the most steering position”. Owing to the exposure of the compass to the weather and harsh conditions, it becomes necessary to safeguard the compass. The navigation instrument that helps serve this purpose is that the binnacle. Alongside this aid, binnacles also safeguard the compasses from toppling over thanks to the constant rolling and pitching of the vessel.
Read: Swinging compass
What is the binnacle
The binnacle may be a cylindrical container made from non-ferrous material that houses the various components of the compass which as an entire . Earlier, wood was used for the development of the binnacle. The compass bowl is housed within the top a part of the binnacle whereas the center part is accessible through a door housing the corrector magnets extending to the projector towards the forward.
Magnetic compass correctors in a binnacle
- Flinders Bar
- Quadrantal Spheres
- Heeling Magnet
- Athwartship Magnets
- Fore and Aft Magnets
In the centre a part of the lower half the binnacle are contained many holes which contain inside them corrector magnets to negate disturbing effects of magnetism caused by the hull of the ship. The specifications of the corrector magnets are decided by an authorised ‘compass adjuster’ whose services are usually called upon in port. The entrance to those corrector magnets must be kept locked in the least times unless when needed to be opened for adjustment.
The Flinders Bar
The Flinders Bar may be a soft iron corrector vertically placed within the for’d or aft a part of the binnacle counting on the extension of the superstructure area abaft of or forward of the binnacle. The length of the bar could also be changed during adjustment of the compass.
The Quadrantal Correctors
The Quadrantal Correctors are two soft iron spheres fitted in brackets on either side of the binnacle. Again, the space between the quadrantal correctors are often altered during adjustent of the compass.
The helmet is fitted on top of the binnacle and is non-ferrous. This is in situ to guard the compass bowl from the weather and harsh conditions.
Care and maintenance
- Access doors to be kept locked in the least times
- If made from wood, the binnacle should be varnished and not painted
- The quadrantal corrector must be painted from time to time to stop rust from settling
- The brass parts are to be polished regularly
- All materials with magnetic properties must be kept faraway from the compass
- Helmet to be kept in position in the least times
- All adjustment to be administered by an authorised compass adjuster
- Remove any bubbles which will be present within the compass bowl within the binnacle
Removal of bubbles
- Following steps should be taken to remove bubbles:
- Tilt the bowl till the filler hole comes up and may be seen
- Unscrew the screw
- Top up with ethyl alcohol. If ethyl alcohol is not available, use distilled water
- Screw the screw back
- Return the bowl to position
The compass is housed on the monkey island and therefore the compass course must be viewed from the bridge. The compass projector is in situ to enable an equivalent via subsequent reflections. It is in situ to enable the helmsman to within the wheelhouse to look at the coincident mariner's compass reading and lubber's line to steer the ship correctly .
