Binnacle
noun
Definition
A binnacle is a non-magnetic, cylindrical housing that holds and protects a ship’s magnetic steering compass. The term originates from the Latin word habitaculum, meaning “little house,” which perfectly describes its function a safe enclosure for the compass used in marine navigation.
Traditionally built from brass or other non-ferrous materials, the binnacle is mounted near the helm or on the monkey island (the uppermost deck of large vessels) and often covered with a tarpaulin when not in use.
The binnacle’s primary purpose is to isolate the compass from magnetic interference caused by the ship’s metal structure while keeping it steady and readable under rough sea conditions.
Purpose and Function
A magnetic compass responds to both the Earth’s magnetic field and the magnetic fields generated by a ship’s iron parts. The binnacle minimizes these effects and includes corrective mechanisms that compensate for magnetic deviation, ensuring accurate bearings for safe navigation.
Key Components of a Binnacle
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Flinders Bar: A vertical tube containing iron bars that counteract the vertical magnetism naturally present in the ship.
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Quadrantal Spheres: Two adjustable metal spheres mounted on either side of the binnacle to correct deviation caused by ferrous materials on board.
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Heeling Magnet: A bucket-and-chain setup that corrects compass deviation when the vessel heels or lists.
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Longitudinal and Athwartship Correctors: Magnets positioned fore and aft and at right angles to the ship’s centerline to correct the permanent magnetic field.
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Binnacle Light: Illuminates the compass for nighttime navigation and typically includes a dimmer function, similar to the Vimar 120V Rotary Dimmer
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Gimbal Arrangement: Allows the compass to remain level despite the ship’s motion, ensuring steady and accurate readings.
Fun Fact
The word binnacle has also found its way into automotive design. It refers to the part of a car’s dashboard that houses instruments like the speedometer and tachometer a nod to its maritime origins.
Example in a Sentence
“As the research of magnetism progressed, binnacles were constructed with greater precision to prevent compass disturbances caused by iron.”
Related Terms
FAQs
What is the main purpose of a binnacle on a ship?
A binnacle houses and stabilizes the ship’s compass, shielding it from magnetic interference caused by the ship’s structure and helping maintain accurate bearings during navigation.
Why are binnacles made of brass or non-magnetic materials?
Brass and other non-ferrous metals don’t affect magnetic fields, ensuring the compass remains unaffected by surrounding materials and delivers accurate readings.
What are quadrantal spheres on a binnacle?
Quadrantal spheres are two adjustable iron balls attached to the sides of a binnacle that correct compass errors caused by the ship’s magnetic field.
Where is the binnacle located on a vessel?
It’s typically positioned near the helm on smaller boats or on the monkey island (the upper bridge deck) on larger ships for optimal visibility and alignment with the vessel’s heading.
Do modern ships still use binnacles?
Yes. Even with digital navigation systems, magnetic compasses in binnacles serve as essential backup instruments required by maritime safety regulations.