Gary,

PARKING:
My definition of "parked" is what Bill Vining has just described. The idea is to keep your boat stationary. With a catamaran you normally accomplish this by letting the main way out, having the jib in enough so it does not flog (softset), and having the tiller hard over. If there is no tide or current involved, the boat will just kind of sit in place, oscillating back and forth through about 45 degrees toward the wind and away from the wind. It kind of backs around away from the wind and then moves forward again toward the wind and then backs around away again, etc.

Meanwhile, it is also drifting in a direction that is sort of a combination of downwind and sideways. You can easily see this if you do a drill where you try to park your boat beside a mark. It is very difficult to maintain your position beside the mark even though you are "parked," because the drift will keep taking you away from it. However, when you are "parked," you are not making progress upwind, and you are the mercy of the "drift."

That is why, if you are parked and if your leeward drift is toard a hazard, like rocks, you can do the "dime tack," as described earlier in this thread, to get the boat onto the other tack so it will drift a different direction.

HEAVE TO:
The definition of "heaving to," according to all my research, is that you are NOT trying to park in one place --you are trying to set the sails and the rudder so the boat continues to sail forward, but at a very slow pace, on a close-reach angle into the wind and waves.

That is accomplished by balancing the sails and helm so the boat will continue to slog slowly forward. Normally this is done by having the jib backed and sheeted on the windward side, basically centering the helm, and then setting the main so it properly counteracts the jib and keeps the boat on a close or close-reach course into the weather. Sort of natural autopilot.

Now, having said all that, I think "parking" is something that most sloop-rigged monohulls cannot do. At least they do not seem to do it. If you are at a regatta with monohull sloops (Flying Scots, for instance), you do not see them parking. They just keep sailing back and forth all the time between races.

Maybe the reason they "heave to" in heavy wind conditions is because they are not able to park.

So the question remains for multihulls: If you are caught out in a big storm and big waves, whether a small multihull or a large one, is it preferable to park and drift or to heave to and maintain some forward progress?

Or I may be all wet about all of this. But I'm glad Gary started this particular discussion, because nobody really seems to know the answer as far as the best option for a multihull in severe conditions.