I don't have any vang. In the picture below you can see diagonal 2-part lines running from the aft crossbeam ends to the end of the boom... keeping the boom centered at anchor. Those are detachable with snap shackles -- so under sail only the leeward one is attached to the boom. They act as preventers and are also used in conjunction with the main sheet to limit upward boom movement when deep reaching. Don't need no stinking vang.