bad advice, again
boats tend to wallow DDW in wind over 10 knots apparent when running under a spinnaker without a main or when running wing on wing with the main sailing by the lee. once you're wallowing, you're one gust away from what we call a death roll, and if you are using a preventer (or worse yet, a vang on the rail)to keep the main by the lee you stand a very good chance of losing the rig during a death roll. inexperienced sailors should understand two things: these are small-boat tactics for use only in light air; expert sailors don't need to resort to preventors to sail wing on wing. learn to do it right and you won't have to endanger your rig. otherwise, if you death roll with the preventor on, either the boom explodes or the mast will snap at the gooseneck when the boom submerges. the advice to use the vang as a preventor is just plain bad: you won't be able to depower the main by blowing the vang should you get hit by a gust. not smart. remember, once your rudder comes out of the water during a roundup the only way to regain control is by blowing the vang. similarly, running a chute without a main means that you won't have the main's wind shadow to tuck the chute behind should you suddenly need to control it. on a big boat you can't control a chute by rudder alone unless the wind is very light. using small boat downwind tactics in any sort of wind is going to result in gear failure sooner or later. if you're determined to sail DDW, especially offshore, a far better solution is to go with double headsails. the only time when a preventer is called for is when you're in light air and the swells are big enough to cause unwanted gybes; at that point it's almost always preferable, both in terms of crew comfort and VMG, to reach rather han run.