This is from cruiserforum.com and applies to a dinghy but I think the principle is applicable to larger boats. I feel that some of the circumstances described in this thread justifies having a hand on the mainsheet when running dw. As I am in a learning phase, the following helped clarify and reminded me that practice on this technique of sailing is as important as MOB drills. Being good at the former may prevent the latter in this case.
Originally Posted by CaptainJeff
rtbates gives good advice, but is a bit off regarding the terms.
When sailing DDW (dead downwind) one cannot fall off the wind any farther, because there is no deeper point of sail to "fall off" to.
What rtbates is actually proposing is to avoid a DDW point of sail by steering the boat higher into the wind, so as to have both sails drawing on the same side. This maneuver would be to Bear Up, Come up, Go Up, Harden up, or Head Up. The result of hardening (the sheets) up would be to put the dingy on a deep run so as to adopt a strategy of so-called downwind tacking (an imprecise term, but it describes the zig-zag downwind course that results).
Practicing downwind tacking (gybing from a starboard deep run to a port deep run, and vice-versa) is a worthwhile use of your time, but should be practiced, like most maneuvers, in lighter conditions until skills and timing are perfected. When gybing:
harden up the mainsheet to center the boom, while maintaining a deep run
pull the tiller to weather until the mainsail fills from the opposite side (shift your bodyweight at this moment to the new windward side to retain balance)
ease the mainsheet to let the boom out quickly so as to avoid a broach, then
trim the new working jibsheet and adjust your course.
This prevents the uncontrolled swinging of the boom from one side to the other in a fresh breeze, i.e., a crash gybe, and the sudden shift in balance that is hard to keep up with, and which undoubtedly caused your dunking .
Until those skills are perfected, when caught in strong winds, performing the so-called chicken gybe will leave the boat in your control and prevent damage to the boat. The chicken gybe is performed by:
quickly heading up from a starboard run through a close reach, hardening the mainsheet energetically to keep the boat driven
continuing the turn by steering the bow across the wind (tacking), and
easing off on the mainsheet/trimming the new working jibsheet to adopt the new point of sail, a port run, or vice-versa
There is nothing "chicken" about staying in control of your boat; rather, it is the sign of a prudent skipper.
Your anecdote brings back my salad days on the bay teaching myself in my own 14' dinghy. You're going about it the right way, from all I can tell.
SkiprJohn is right: the farther off the wind your point of sail is, the less centerboard you need in the water. Just don't forget to lower it again when coming up, or you'll be side-sliding across the bay with no board to prevent leeway (been there, done that).
Note: when the breeze freshens, there is a real danger of a broach, an uncontrolled acceleration/pointing up due to over-pressure on the mainsail. In extreme cases, it can spin the boat around like a top before dumping you over. On broad reach and deeper courses in any kind of breeze, always have the mainsheet in hand and ready to release in a blink, or you could find yourself capsized and/or inadvertendly hitting someone/something.