Also the part of a crew on a yacht typically responsible for tactics
and rules interpretations
during races. They usually maintain navigation
of the boat, and forecast the weather to assist the skipper
in choosing the fastest track during the race. They are responsible for MOBOARDs
to determine the best angles of attack, and also perform MOBOARDs to determine which angle to the wind produces what boat speed and speed over ground
combination. Finally, their most important responsibility is to maintain the crew's safety by serving as a safety observer, attempting to preclude dangerous situations on the boat.
Usually the afterguard is the lightest member of the boat so that they affect the balance of the boat the least as they move around the cockpit rather than riding the rails for ballast. Typically the afterguard will have racing experience in one of the other crew positions, and thus tends to be one of the senior members of the crew (many times senior to the skipper).