The Coefficients Flashcards
Coefficient A
Unsymmetrical Horizontal Soft Iron (Caused by H the earth Horizontal Magnetic Field).
Apparent A - Mechanical Caused by the Lubber line not in the Fore&Aft line of the ship. (Slacken Bolts & adjust) Compass card not accurately centered. N/S Needle not parallel. Damaged azimuth Mirror
What cuases Coefficient B
It is the Fore and Aft component passing through the compass.
Caused by:
Permanent B - Caused by the Fore+Aft Component of the ships magnetic field (“P” Force of ship)
&
Induced B - Caused by the induction of Vertical Soft Iron in the Fore+Aft Line. (“Z” Force of Earth)
How is Perm B corrected for?
Place ship on E/W Heading.
Correct with Permanent Magnets in Fore+Aft slots of the Binnacle
(Deviation strongest on an E/W heading. Direction of Blu/ Red ends depends on where the ship was built.)
How is Induced B corrected for?
Place ship E/W heading.
Correct with Flinders bars fwd or aft of the compass.
Normally fwd as funnel is induced.
Amount of induced varies with Latitude. Max @ Poles and Min @ Equator.
How to split B?
Carried out within 50nm of equator
E/W heading.
Eliminate any Deviation present using Permanent Magnets only when back in Fore and Aft Perm Magnets.
When back in Higher Latitudes correct any Deviation present using Flinders bar.
Done when near the equator / when changing operating regions.
What can be done is home trade only?
Coeff B can be corrected for entirely with Permanent Magnets.
What happens with B when near eqautor?
No Z force. Place on East West. Correct with Permanent.
When back in High Latitudes. Place E/W look for Deviation if present correct with Flinders.
Coefficient C
It is the Athwartship’s Component passing through the compass.
Caused by:
Perm C- The Athwartship’s component of the Ships Magnetic Field (“Q” Force)
Induced C- Caused by induction of Vertical Soft Iron in the Athwartship’s. (Not normally present on well sighted Compass)
How to correct Coeff C?
Place ship on N/S heading. Correct with Permanent Magnets in Athwartship slots of Binnacle.
Coefficient D
Caused by the Induction of Horizontal Soft Iron either Fore+Aft and/or Athwartships.
(Caused by the H component of the Earth Magnetic Field)
How to correct for Coef D?
Place ship on each of Inter-cardinals. If….
+D is found –> Move Spheres Together
-D is found –> Move Apart
What is the goal of a Compass Adjuster?
To identify and evaluate the coefficients, and reduce their effects to a respectable value or ideally eliminate them by placing soft and hard iron correctors about the binnacle.
What is DIP? How is it measured?
Dip is the Angle between the earths total force and the horizontal. Measured using a VFI.
