FLINDER BAR EXPLANATION AND SOLUTION FOR ALL LATITUDES
In some vessels, sometimes It happened to me, that the captains ask me why when the vessel changes a lot of in latitude ,some deviations appear , overall in E-W magnetic headings and the explanation and the procedure to solve the problem is as follows:
Coefficient B & Induced Magnetism
The coefficient B ,has two components, one is due to the permanent magnetism which is corrected with the fore&aft magnets, the other is due to the vertical induced magnetism , which is corrected with the FLINDERS BAR.
Normally the coefficient B(both parts) is corrected when the vessel left the shipyard and if the FLINDERS BAR does not have the proper length, some E-W deviations will appear when the vessel changes a lot of in latitude due to that the induced magnetism changes with it.
Adjustment in Mediterranean & Latitudinal Shift
Taking into account we are going to adjust the coefficient B in latitudes close to Valencia or other Mediterranean ports ,with only the fore&aft magnets (I will not change the length of the FLINDERS BAR), maybe, when the vessel changes a lot of in latitude some deviations will appear due the induced magnetism will change.
The procedure is as follows:
In position of magnetic equator or close when Z=0º and then there is not vertical induced magnetism.
Step-by-Step Procedure for All Latitudes
1.Take out all pieces of FLINDERS BAR.
2.When the ship crosses the magnetic equator or close, head to Em or Wm and in the position of magnetic equator or close , correct all the deviations which appear with FORE&AFT magnets.
3.When the vessel is in other part of the ocean ,around 25º or 30º in latitude( N or S) , head to Em or Wm.
4.Correct all the deviations which will appear with the pieces of Flinders Bar.This will serve for all latitudes. To insert the pieces of bar, start with the smaller and continue with the bigger till in a way that the superior should be at the same level of the compass rose.
Do not forget to supplement with wooden blocks in a way to the last piece will be at the same level of the compass.
REMARKS: The use of the FLINDERS BAR is not necessary if the vessels sail in the same latitude or do not change a lot , like tug-boats, coastal vessel,etc…
CAPT. A.ROS COMPASS ADJUSTER Nº 86 BY DGMM (SPANISH ADMINISTRATION)