HOW TO ADJUST THE COMPASS

It is advisable to do many of the following Compass adjustments prior to making the first "Swing"

Removing a bubble

Compass fluid may be added by means of the filling plug on the side of the compass bowl.Check the Compass maufacturers manual for what fluid is advised to be used for filling

The 'A' Error

All 'A' found may be removed by rotating the compass binnacle (or stand) in the proper direction as best possible

Order of Adjustments(1) Flinder's Bar(2) Quadrantal correctors(3) Heeling error magnets(4) Fore & Aft magnets(5) Athwartships magnets

1 - FLINDERS BARThe main use of this corrector is to overcome induced B error caused by funnels & cranes

Residual Magnetization check of the Flinders barThe Flinders bar magnetization check is preferably made with the ship on steady east or west compass headingTo make this check: (a) Note the compass reading with the Flinders bar in the holder (b) invert the Flinders bar in the holder and again note the compass reading.

Quadrantal error from Finders bar.

2 - QUADRANTAL SPHERESPlace the spheres at the best position as indicated by the previous deviation table.If the compass has never been adjusted, place the spheres at midposition on the bracket arms.

Residual Magnetization check of the Quadrantal SpheresThis test may be made with the ship on any steady heading. Move the spheres as close to the compass as possible and slowly rotate each sphere separately.

3 - HEELING MAGNETSHeeling error is the difference between a vessel's deviation when upright & when heeled on the same headingAdjust the positioning of the heeling magnet by means of a properly balaned dip needle, if available, OR

Quite large bubbles sometimes appear beneath the cover glass. They may shrink or enlarge as the temperature changes and, other than looking unsightly, may be no trouble at all. If they cause difficulties then the fluid will need topping up.

Correct alignment of the lubber's line of the compass, gyro repeater, and pelorus with the fore-and-aft line of the ship is of major importance. Such a misalignment will produce a constant A error in the curve of deviations.

The order in which you carry out adjustments is important as they are not totally independent, and the correctors themselves may interact (eg permanent magnetism in the quadrantal correctors may cause B and C deviation)

The iron sections of Flinders bar should be continuous and at the top of the tube with the longest section at the top.Wooden spacers are used at the bottom of the tube to achieve such spacing.

Any appreciable difference (2° or more) between these observed readings indicates residual magnetism in the Flinders bar. Such Flinders bars that show signs residual magnetism should be annealed (i.e. heated to a dull red and allowed to cool slowly)

Since the Flinders bar is generally placed in the forward or aft position, it acts as a small minus D corrector, as well as a corrector for vertical induced effects.

This means that upon inserting the Flinders bar in such a position, the regular spheres should be moved closer to correct for the increased plus 'D' error, or vice versa, if the Flinders bar is removed

Shift the spheres as described in the "What to Adjust" section of this program

Any appreciable deflection (2° or more) of the compass needles resulting from this rotation indicates residual magnetism in the spheres. Such spheres that show signs residual magnetism should be annealed (i.e. heated to a dull red and allowed to cool slowly)

Adjust the heeling magnet while the ship is rolling on north and south headings until the oscillations of the compass card have been reduced to an average minimum as described in the "What to Adjust" section

4 & 5 - FORE & AFT MAGNETS / ATHWARTSHIP MAGNETSAdd/Remove or shift these magnets as described in the "What to Adjust" section after making the compass swing

WHAT TO ADJUST IN THE COMPASS

Following the "How to Adjust", see what observed errors need correction on the Flinder Bar & Heeling Magnets

THE FLINDERS BAR - Select the type of error you observed in the scroll box below

1If no bar in holder then place required amount of bar forward

Increase amount of bar forward if bar forward of binnacleDecrease amount of bar forward if bar aft of binnacle

THE HEELING MAGNETS - Select the type of error you observed in the scroll box below

1Raise the heeling magnet if red end is up or Lower the heeling magnet if blue end is up.

SWING THE SHIP

Swing the ship to get the True headings for the required eight( 8) Compass points

Fill out the 'Swing' data (in blue) below & proceed to see the personalised solutions for reducing the Deviation below

Cardinal Compassº Trueº Dev A B C D E

N 000º 343.0º -1.5 W -1.5 -1.5 -1.5NE 045º 029.0º -0.5 W -0.5 -0.5E 090º 073.0º -1.5 W -1.5 -1.5 1.5

SE 135º 119.0º -0.5 W -0.5 0.5S 180º 166.0º 1.5 E 1.5 -1.5 1.5

SW 225º 212.0º 2.5 E 2.5 2.5W 270º 257.0º 2.5 E 2.5 -2.5 -2.5

NW 315º 298.0º -1.5 W -1.5 1.5

Variation Sign Convention 0.1 -1.4 -1.5 1.0 -0.315.5º E is +, W is - A B C D E

THE 'A' ERROR A is + (Deviation shown more than actual)This Error is less than 0.5 degrees and so will be impractical to correct

THE 'B' ERROR B is - (Westerly on East & Easterly on West)Place required magnets red aft if no magnets or magnets are less

Raise magnets if fore & aft magnets are red aftLower magnets if fore & aft magnets are red forwardTHE 'C' ERROR C is - (Westerly on North & Easterly on South.)

Place required athwartship magnets red to starboard no magnets or magnets are lessRaise magnets if athwartship magnets are red to port

Lower magnets if athwartship magnets are red to starboardTHE 'D' ERROR D is + (E on NE'ly, W on SE'ly, E on SW'ly, & W on NW'ly)

If first time or if no spheres then place spheres athwartshipMove spheres toward compass or use larger spheres (if sphere's are athwartship)

Move spheres outward or remove (if spheres are fore & aft)THE 'E' ERROR E is - (W on N'ly, E on E'ly, W on S'ly, & E on W'ly)

The existence of a sizeable E error is rare, but if you really do need to correct this you have to slew the spheresIf first time or no spheres then place spheres at starboard forward & port aft intercardinal positions

Slew spheres counter-clockwise through required angle (if spheres are athwartship)

To avoid Gaussin error when adjusting and swinging ship for residuals, the ship should be steady on the desired heading for at least 2 minutes prior to observing the deviation

Slew spheres clockwise through required angle (if spheres are fore & aft)

PRACTICAL STEPS FOR ADJUSTING THE COMPASS

(This step is not required if prior adjustment has been made)

-1.51.5

(The cardinal heading adjustments should now be complete.)

6. Come to any intercardinal magnetic heading, e.g. North-East (045°).

8. Secure all correctors before swinging for residual deviations.9. Swing for residual undegaussed deviations on as many headings as desired, although the eight cardinal andintercardinal headings should be sufficient.

Once completed,swing the vessel to get the new values of True Heading for the 8 Compass points.

Congratulations ! You've just completed adjusting your compass.

Once your satisfied with the new deviation proceed to '4- Final Deviation Card'

Don't forget to colour the magnets diagram (red & blue) for easy identification and sign it before posting it up.

Once you've completed the "What to Adjust" sheet, take a printout of the solutions and proceed to make the second swing to correct the compass following the steps below.

1. Adjust the heeling magnet, while the ship is rolling, on north and south magnetic heading until the oscillations of the compass card have been reduced to an average minimum.

2. Come to an East (090°) cardinal magnetic heading to remove all deviation. (See B Error)3. Come to a South (180°) magnetic heading. to remove all deviation. (See C Error)4. Come to a West (270°) magnetic heading. Correct half of any observed deviation by moving the B magnets.5. Come to a North (000°) magnetic heading. Correct half of any observed deviation by moving the C magnets.

Correct any observed deviation by the spheres (See D Error)

7. Come to the next intercardinal magnetic heading, e.g. South-East (135°). Correct half of any observed deviation by moving the spheres

(The intercardinal heading adjustments should now be complete. More accurate results might be obtained by correcting the D error determined from the deviations on all four intercardinal heading)

10. Should there still be any large deviations, analyze the deviation's again using the "What to Adjust" to determine the necessary corrections and repeat as necessary steps 1 through 9 above

Input the new values of the TRUE HEADING into the calculation table (2-What to Adjust) for the eight (8) compass points

Fill in the details where appropriate in the "Final Deviation Card" & take a print out

DEVIATION TABLE DEVIATION TABLECompassº Deviationº Devº

000º -1.5 W 000º -1.5 W

045º -0.5 W045º -0.5 W090º -1.5 W

090º -1.5 W135º -0.5 W180º 1.5 E

135º -0.5 W225º 2.5 E270º 2.5 E

180º 1.5 E315º -1.5 W360º -1.5 W

225º 2.5 E

270º 2.5 E

315º -1.5 W

360º -1.5 W

Co-Efficients REMARKS : Vessel NameA 0.1 NO MAGNETS SHIFTED AS DEVIATION WITHIN

ACCEPTABLE LIMITS. MAERSK KALEAB -1.4

Position 17 25.2 SC -1.5 061 42.7 E

Variation 15.5 WD 1.0 Date & Time 13/10/2010 10:30 to 11:30 LT

E -0.3 2/OFF RANJITH.A 3/OFF ABHISHEK MASTER CAPT.S.ROYAN

000º 045º 090º 135º 180º 225º 270º 315º 360º

-2.0º

-1.5º

-1.0º

-0.5º

0.0º

0.5º

1.0º

1.5º

2.0º

2.5º

3.0º

-1.5

-0.5

-1.5

-0.5

1.5

2.5 2.5

-1.5 -1.5

DEVIATION CURVE

COMPASS HEADING

W D

EV

IAT

ION

E

Sharan Desai®™

DEVIATION TABLE DEVIATION TABLECompassº Deviationº Devº

000º -1.5 W 000º -1.5 W

045º -0.5 W045º -0.5 W090º -1.5 W

090º -1.5 W135º -0.5 W180º 1.5 E

135º -0.5 W225º 2.5 E270º 2.5 E

180º 1.5 E315º -1.5 W360º -1.5 W

225º 2.5 E

270º 2.5 E

315º -1.5 W

360º -1.5 W

Co-Efficients Position of Corrector MagnetsA 0.1

Fore & AftPort 1 pce (4)Stbd

B -1.4Athwartship

Fore 2 pce (1,3)Aft

C -1.5Heeling Magnets C. Mark No 3

D 1.0 Quadrantal Correctors Port Centre(Spheres) Stbd Centre

E -0.3 Flinders Bar Length 2/3rd

Compass Adjustor©

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3

0.0º

45.0º

90.0º

135.0º

180.0º

225.0º

270.0º

315.0º

360.0º

DEVIATION CURVECOMPASS HEADING

W

D

EV

IAT

ION

E

Sharan Desai®™

Vessel Name

Position

Date

Compass Adjustor

Compass Adjustor©