Experiences with Compasses in the Mid-20^th Century

Abstract

This paper presents the thoughts and experiences of marine navigators of the mid-20 th century in their use of compasses during the transition from magnetic to gyro compasses.2. Magnetic compass. I N T R O D U C T I O N.In the mid-20 th Century, ships' magnetic compasses had hardly changed in design or construction since Victorian times. Gyro compasses, on the other hand, were comparatively new devices and were by no means installed in all ships, even relatively large ships. This paper is a collection of firsthand experiences in the practical use of compasses during the period in question.Old sailors' tales, if you like. M A G N E T I C C O M P A S S E S.Magnetic compasses of the time were often mounted in shrines of teak and polished brass. The purpose of these binnacles was to support the gimbal system in which the compass bowl was slung, to provide lighting for night-time viewing of the compass card and to house the system of correctors. These included horizontal and vertical permanent magnets, a pair of soft iron spheres and a vertical, soft iron Flinders' bar. Every few years, a compass adjuster would swing the ship to adjust the correctors and compensate for the deviating effect of the ship's steel structure on the compass. On leaving the ship, he would hand a deviation card to the captain, setting out the residual deviation on all headings of the ship. This would normally show that the residual deviation was zero on all headings except, perhaps, half a degree on southwest, to show that the compass adjuster was a mortal being despite the apparent magic he had performed. Mortal, he might or might not have been, but his deviation card would have no relationship with the real world whatsoever. However, it was routine for us to check the compass error by Sun or star bearings at least once on each watch, and more often if the ship made a significant change of heading, so we soon discovered what real deviations the adjuster had left us with.

Latitude Error in Compass Deviation: Mathematical Method to Determine the Latitude Error in Magnetic Compass Deviation

“…Both coefficients may be considered constant for a long time. However this may not always be the case, since a bolt of lightning or a shipment of steel cargo may affect the ship magnetism [8].…”

Towards an Improvement of Magnetic Compass Accuracy and Adjustment

“…Moreover, the deviation differs over time and compass compensation must be performed at least every two years (one year according to some regulations) and every time that the ship magnetism changes suddenly (ISO, 2009). Some thoughts and experiences concerning violent changes in ship magnetism, such as lightning striking metallic installations of the ship, are related by Kemp (2010).…”

Coastal Navigation in the Mid-20th Century

“…This is the third in a series of papers about various aspects of merchant ship navigation in the mid-20 th Century. Previous papers concerned Soundings (Kemp et al 2008) and Compasses (Kemp et al 2010). As with those papers, this compilation is intended to encourage our fellow ancient mariners to record their experiences of navigating ships in the middle years of the 20 th century.…”