What Does Abaft Mean?
In nautical terms, abaft describes a position toward or near the stern (rear) of a vessel. It’s used to indicate direction or location when navigating, steering, or describing the placement of equipment onboard.
For example, if something is located “abaft the beam,” it means it’s behind the midpoint of the vessel, closer to the stern. The opposite term would be forward or ahead.
How “Abaft” Is Used in Navigation
The term is more than just sailor slang it’s used formally by the U.S. Coast Guard to define navigation rules and lighting angles.
According to Rule 13 of the International Regulations for Preventing Collisions at Sea (COLREGS),
“A vessel shall be deemed to be overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft the beam.”
In simpler terms, if one boat is approaching another from behind that angle, it’s considered an overtaking vessel and must yield.
Abaft in Navigation Lighting
Understanding “abaft” is key when positioning navigation lights on your boat. These lights use specific beam angles based on where they’re installed:
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Masthead Light: Mounted over the fore and aft centerline of the boat, it shines light from directly ahead to 22.5 degrees abaft the beam on each side.
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Sidelights (Port and Starboard Lamps): Each light covers an arc of 112.5 degrees, showing from directly ahead to 22.5 degrees abaft the beam on the respective side.
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Stern Light: Mounted at the back of the vessel, showing light 67.5 degrees from the centerline on each side, covering a total arc of 135 degrees.
Explore marine-grade options such as:
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DRSA LED Masthead Lamps for reliable 360° visibility.
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Port and Starboard Navigation Light Kits built to meet USCG requirements for recreational and commercial vessels.
Visualizing Abaft
If you were to look down on your boat from above, the bow is at the front, the beam is the widest part of the hull, and abaft indicates everything toward the stern.
Knowing these directional terms helps with communication, safety, and lighting compliance, especially when navigating at night or in crowded waterways.
Example in a Sentence
“The captain ordered the deckhands to move abaft the mainmast to even out the vessel’s balance.”
Synonyms
aft, behind, astern, back, toward the stern
Related Terms
Aft
Stern
Stern Light
Starboard
Port Lamp
Explore Marine Navigation Lighting
Shop navigation lights and stern lights at DRSA.com. Each product is engineered for precision beam control, marine-grade durability, and compliance with U.S. Coast Guard lighting standards.