SHIP'S MAGNETISM, PART- 06, NAV AIDS, PHASE -II, Coefficient C — Athwartship Magnetic Error 🧲🧭

Coefficient C — Athwartship Magnetic Error Explained 🧲🧭 | Ship’s Magnetism | Chief Mate / OOW This lesson explains Coefficient C, a key component of magnetic compass deviation and an important topic for Chief Mate, OOW, and Deck Cadet examinations. Coefficient C represents the maximum value of semi-circular deviation that varies with the cosine of the compass course. It is caused by the athwartship magnetic field of the ship and consists of both permanent and induced components. 🧲 What Creates Coefficient C? Coefficient C is produced by: 1️⃣ Permanent C (PC) — due to permanent magnetism built into the ship during construction 2️⃣ Induced C (IC) — due to induced magnetism in vertical soft iron located off the ship’s centerline Together, these components influence deviation differently on various headings. 🛠 Permanent C (PC) Permanent C develops when a ship is built on an easterly or westerly heading, creating magnetic poles across port and starboard. Deviation pattern: • Maximum easterly deviation on northerly headings • Maximum westerly deviation on southerly headings • Zero deviation on easterly and westerly headings Effect on directive force: • No change on North / South • Reduced on East / West Correction: Permanent C is corrected using athwartship permanent magnets fitted horizontally in the binnacle. 🧲 Induced C (IC) Induced C arises from vertical soft iron structures located off the centerline, such as side bulkheads near the compass. Key points: • Often small or negligible on most merchant ships • More common on aircraft carriers, ships with off-center compasses, or strong side bulkheads • Varies with cosine of the heading • Strongest on North / South • Zero on East / West Correction: Induced C is corrected using Flinders bar pieces fitted on the port or starboard side. 🔁 Combined Correction — Induced B + Induced C This video also explains how Induced B and Induced C are corrected together using a single Flinders bar. Method: • Calculate slooh angle: tan(slooh angle) = IC / IB • Swing ship to heading: (90° − slooh angle) to port • Adjust Flinders bar for maximum correction A worked numerical example explains how a Flinders bar fitted at a slooh direction confirms the presence of both IB and IC. 🎯 Who This Video Is For ✔ Chief Mate Phase-II candidates ✔ OOW & Deck Cadets ✔ Navigation Aids students ✔ Anyone preparing compass deviation numericals Understanding Coefficient C is essential for deviation cards, compass adjustment, and safe navigation. CONNECT WITH SAILOR RIDER YouTube:    / @sailor_rider   Instagram:   / sailor_rider   Facebook:   / 19imzynlrp   Threads: https://www.threads.com/@sailor_rider TAGS coefficient c ship magnetism athwartship magnetic error semi circular deviation cosine permanent c magnetic compass induced c deviation explained slooh angle compass flinders bar correction explained athwartship magnetism ship magnetic compass deviation coefficient c chief mate magnetism lesson oow navigation aids compass merchant navy magnetic compass tutorial induced b and induced c correction binnacle compass magnets marine navigation magnetism #MagneticCompass #Navigation #ChiefMateExam #MerchantNavy #NauticalScience