Magnetic compass: The coefficients are the mathematical ... - Rajnav

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Coefficient E This is caused due to induced magnetism in the horizontal soft iron located symmetrically about 45 deg from the compass position. This is corrected by the slewing of Kelvin’s spheres at their athwartship position to cancel this deviation. Coefficient J (Heeling error) This is the mathematical representation of the deviation caused when the vessel is heeled to port or stbd by 1 deg. This has 4 components: 1. Deviation due to Vertical component of the ships permanent magnetic field. Maximum deviation in the north and south courses and does not change with latitude or hemisphere. (Corrected by Heeling error magnets) 2. Deviation due to Induction of vertical soft iron component below the compass. Maximum on North and South courses but changes in strength and polarity with latitude and Hemisphere (Corrected by Heeling error magnets) 3. Vertical induction of Horizontal athwartship soft iron as the vessel rolls. Changes in polarity with the hemisphere. In southern hemisphere it will be low sided deviation and in the northern hemisphere it will be high sided deviation. This is corrected by the presence of Kelvin’s spheres. Maximum deviation on North and South courses 4. Horizontal induction of Fore and Aft soft iron, terminating below the compass position. Maximum on North south courses and nil on East/West courses. Heeling error is corrected by the use of Vertical permanent magnets Heeling error magnets in a bucket placed below the compass. The bucket is attached to a chain and its position can be adjusted by adjusting the chain. The bucket has holes to vary the number of magnets. At the equator the bucket is placed at its lowest position and farthest from the compass. As the latitude increase the bucket is placed closer to the compass by adjusting the bucket.
3. Magnetic bearing of an object is found out by taking bearings of a chosen object from all cardinals adding all the values and then dividing by the number of cardinals. 4. The object chosen for swinging should be at least 15 miles (to avoid parallalax error) 5. The heeling error bucket is in the way and hence in order to maintain symmetry the F/A correctors are placed on both sides for Bp correction. 6. Two correctors at bottom are preferable to one single corrector at the top in order to avoid parallax error and also to produce uniform field. 7. This is a combination of alcohol and distilled or Bayol. The alcohol is used to prevent the water from freezing and the water is added to prevent the alcohol from evaporating. In case of Bayol it is a special liquid and has the R.D to give horizontal stability to the card movement and also the buoyancy for the card itself to reduce friction at the pivot point. 8. One magnetic compass is required and one more if there is no Gyro at the steering position 9. It should be kept safely stowed where it is away from magnetic influence and any shock. 10. The following information is available from the deviation card: Size, position and number of all correctors Deviation curve Name of the vessel Name of the adjuster Date and place of adjustment of compass 11. The efficiency of the compass can be ascertained by the following: The value of the deviation after correction should be low and symmetrical on all headings The directional force especially at higher latitudes Steady movement on all headings 12. Terminating material is those ships material that can produce magnetic poles above or below the compass in any direction 13.
Page 1 and 2: Magnetic compass: The coefficients
Page 3: Compass adjuster method: With his e
Page 7 and 8: 22. The vessel should be in sea goi
Page 9 and 10: Coefficient D - Kelvin’s spheres

Magnetic compass: The coefficients are the mathematical ... - Rajnav

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