Vang...
Steve,The function of the boom vang is to keep tension on the boom (and thus the main sail) when the mainsheet is eased when running or on a broad reach. This keeps the boom from rising in wind gusts and bouncing around in sea swells and keeps the mainsail from twisting and loosing the desired shape for the current sailing conditions.Also, some people use the boom vang as a accidental jibe preventer by rigging the deck end to a different place on the boat. Most boats nowadays have a vang and it is considered pretty much standard sailing equipment. But some years ago it was found primarily on racing yachts. Having had boats with and without, I definitely prefer having one. A rigid vang is best since it allows for easier main reefing by holding up the boom when shortening sail and allowing you to do away with the dreaded topping lift.Get one and learn to use it. You will truly enjoy all the beneifits!Chris