Say you're on a beat from point A to point B. B could be a mark, the line to fetch a channel, etc. Do you take a few large tacks? Lots of small ones?
Are there any rules of thumb for picking the optimum number of tacks? I realize this will vary with the boat's pointing ability, maneuverability, acceleration, etc., but are there any "in general" ways to decide this?
It's a big question. First, if the wind isn't uniform in strength, tack over to the good wind.
Assuming uniform wind strength, when to tack depends largely on shifts in wind direction. Generally, if it's shifting, stay on the tack that is being Lifted, and tack off a tack that's being Headed, since it's a lift on the other tack. In general, stay on the tack that takes you closer to your destination, and once that destination is more than 50-60 degrees off your windward bow, think about tacking, as the other tack will now be the "major" tack.
Don't "shoot the corner" (meaning don't go all the way out to the layline) from way, way out--if you get lifted, you'll overstand and will have wasted distance; if you get headed, then you'll have wasted distance in a different way.
Picture a windward course to a mark as a christmas tree shape. You start at the bottom with lots of width, then it narrows as you get closer. Try to stay in or near the middle of the "tree", that way you will have room to tack when you get headed, without overstanding.
You can reduce the number of tacks by not tacking til you get, say, a 10-degree header. Crew size, sail size, and fatigue will also govern how many times you want to tack.. In general, watch your compass, it's your friend, and will tell you if you're getting lifted, or headed, or neither.
Hope this of some help. But there's no "correct" number of tacks, it just all depends...
nolatom's comments sound like good advice for racing. If you're not racing, I would say that unless there is a major wind shift, staying on on tack is probably better since each tack will slow you down. Geometrically speaking, the total distance traveled by a boat doing that does one 90-degree tack is the same as one that does many 90-degree tacks.
There will of course be many other considerations. Sailing in narrow channels or channels with hazards will require more tacks, for one thing.
Current is the other big factor that plays a role as well. Sailing across the southern Strait of Georgia I'm often going nearly dead upstream against a current that might be 1 to 2 knots in parts. On one tack, I'll be going upstream and making a measly 1-3 knots speed over ground depending on conditions, while on the other tack I may be making 5-6 knots over ground but have negative VMG :P So I have no choice but to stay on the "slow" tack for most of the trip.
My first rule of thumb for tacking to windward is to tack as infrequently as possible (within the general guidelines that nolatom suggests). Each time you tack, you lose boatspeed, and consequently pointing ability, and consequently you lose ground to windward. If you can fetch the mark in fewer tacks than another boat of the same design, the likelihood is that you'll round it ahead of him, unless he can make up his lost time by playing a wind shift or a current better than you.
Generally, unless you're just putzing around for pure pleasure, each time you tack, it should either be because you are "forced" to do so by considerations of geography or seamanship, or because you stand to gain something from it, by reason of wind speed or direction. If you aren't "forced" to tack, and you won't gain something from tacking, then you should hold your course.
I would agree with Nolatom. Stay on the preferred tack as long as possible, and if there's current (or a tidal stream) keep it in the lee, as that will give you a lift to windward.
Tacking effectively will not loose too much speed, but don't do it too often..
If you can anticipate a windshift, plan accordingly, as that may shorten the actual distance - sometimes you will get it wrong, though :)
A cruiser's perspective:
Stay on the windward (tack) side of the mark for as long as you can hold it and go for speed, if you have the water.
Then you can reach to the final mark.
I go for as few tacks as possible for; the boat speed; physical energy etc etc. A few months ago, I sailed a few hundred miles on the same tack down the Queensland coast. I used this philosophy to stay close to the reef side of the course, giving myself searoom if needed. At one point it was needed and I was happy I had a few miles to play with.
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