Boom Preventer

A line or tackle rigged to restrain a boom from crossing the vessel unintentionally.

A properly arranged preventer leads from a suitable point on the boom to a strong point or controlled line system forward and aft. It is used when sailing with the wind abaft the beam to reduce the likelihood and violence of an accidental gybe.

A preventer can carry severe shock load and does not make an uncontrolled gybe harmless. Boom attachment, deck fittings, line strength, chafe, controlled release and the ability to change sides must form a planned system; tying a short line from the boom to a weak rail can increase damage or trap the vessel in an unsafe position.