A boom brake is a device designed to control the swing of the boom on a

sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminolo ...

. The boom brake acts as a

preventer A gybe preventer, preventer, or jibe-guard, is a mechanical device on a sailing vessel which limits the boom's ability to swing unexpectedly across the boat due to an unplanned accidental jibe. During an unplanned accidental jibe (or ''gybe'' ...

when sailing downwind, and can also be used to jibe(US) or gybe(UK) the mainsail in a slow measured action. Uncontrolled jibes often damage elements of the rig, and can inflict serious and sometimes fatal injuries to crew in the path of the boom or the mainsheet and associated hardware. The brake usually rides on a line running perpendicular to the boom; when the boom brake is actuated, it grabs the line and either works as a preventer, or slows the boom's speed while jibing. The brake is actuated by either tensioning the line upon which it rides or using a second line to tension the brake relative to the main line.

References

*Mainsheet magazine, Vol. 23, No 2, May 2005 Sailing ship components {{navy-stub