Tacking 101

[jrbogie]

hmmmmm. perhaps i'm misreading but I question many of the replies here. no need for trig, spreadsheets or computers. when to tack is quite simple. current notwithstanding, always tack on the headers to get onto the lifted tack. how do you know which is the lifted tack to begin with? turn head to wind. if your bow points to the right of your destination mark, starboard tack is the lifted tack. if it points left, port tack. pointed directly at the mark? take your pick but on starboard you'll have rights when encountering other boats.

while on starboard tack and the wind goes left? you just got headed. tack onto port to get back on the new lifted tack. if the wind goes right? smile, you just got lifted closer to your mark. think opposite when on port tack.

[jrbogie]

Originally Posted by mike d.

I would think it depends on how far off the rum line you want to go. If you sail more on a broad reach(not saying full broad) but an angle that gives you grater hull speed, you can actually gain more ground, than short tacks, because of the speed increase. When I tack it is to set up a better angle of approach to the desired destination. I don't tack because it's written some where that I should. I pretty much let the boat stay in the groove, even falling off to keep up the speed, before tacking!

may I ask what broad reaching has to do with tacking to make the best vmg to windward?

[OldFrog75]

Originally Posted by jrbogie

hmmmmm. perhaps i'm misreading but I question many of the replies here. no need for trig, spreadsheets or computers. when to tack is quite simple. current notwithstanding, always tack on the headers to get onto the lifted tack. how do you know which is the lifted tack to begin with? turn head to wind. if your bow points to the right of your destination mark, starboard tack is the lifted tack. if it points left, port tack. pointed directly at the mark? take your pick but on starboard you'll have rights when encountering other boats.

while on starboard tack and the wind goes left? you just got headed. tack onto port to get back on the new lifted tack. if the wind goes right? smile, you just got lifted closer to your mark. think opposite when on port tack.

But what if the wind direction is more or less constant? In that case there is an optimum tacking point and trig (or a handheld GPS) can help determine what that is. Even if it's shifting, sooner or later you get to the layline and want to avoid overstanding or tacking too soon.

[jrbogie]

Originally Posted by OldFrog75

But what if the wind direction is more or less constant? In that case there is an optimum tacking point and trig (or a handheld GPS) can help determine what that is. Even if it's shifting, sooner or later you get to the layline and want to avoid overstanding or tacking too soon.

sure, but think about what you just said. when you get to the layline it BECOMES the favored tack so tack and you're pointing directly at the mark. in fleet racing a good tactic is often to remain in the center of the course so as to not get caught on the wrong side of a shift. but we're talking cruising here and the op asked how to make the best vmg beating to weather. unless the wind puts you directly downwind of your destination one tack will be favored over the other. his question seems to ask, 'what tack is best,' and when is it time to tack onto the other tack?' if the wind is constant the favored tack won't change until you've sailed to the layline. you're right, you don't want to overstand and sail extra distance so by all means, tack to lay the destination/mark. but sure, if you want to stay near your rumbline then tack early but know that as long as you stay on that tack your vmg will suffer.

[jrbogie]

perhaps this will clarify. the first thing we do when we get to the start area is turn the boat head to wind right in the middle of the start line. if the boat is now perpendicular to the line and pointing directly at the weather mark then the race committee did a good job of setting the course. neither tack is favored, neither end of the line in favored. we can start on either tack knowing that either will give us best vmg. of course starboard will give us rights around the many other boats looking for a good start too.

but if when head to wind the boat points to the right of perpendicular, then starboard tack is preferred as close to the committee boat, right side of the line, as possible. if she's left of perpendicular, a port tack start is favored at the left side pin end of the line. after the start as we sail to weather, it's all about compass heading. if we're on starboard and the compass veers right or remains constant, we stay on starboard. if it veers left, we just got headed so we tack onto port. if there's one rule in racing it's ALWAYS TACK ON HEADERS.

if we put ourselves in a much bigger picture such as cruising to an islan d in the carribean, the rule doesn't change nor does how to determine the favored tack change. if we begin our voyage by putting the boat head to wind and then determine, with gps or whatever, where are island is in relation to our bow we can determine which tack is best to begin to get best vmg toward our island. we'll know if this changes simply by watching the compass while sailing for boat speed.

all of this assumes no current, no possible weather problems or interference with shipping lanes etc., but the original question is all about knowing when to tack which itself is all about where the wind is coming from.

[Jim Cate]

As I read it, the OP was interested in a cruising situation, not a short race with an established course and starting line. Cruising often involves fairly distant destinations or in his parlance, waypoints. When a destination is many hours or days away, lots of the rules of thumb used in racing are inapplicable, for the winds and currents to be encountered are unknown or at best only approximations. So, our practice is to stay somewhere fairly near the rhumb line and to respond to local variations fairly slowly. Tacking on every header gets pretty old in a cruising environment!

Also, in the open ocean, wave patterns from distant origins may be quite different from the local wind waves. This can make big differences in comfort and speed on the different tacks, and can lead us to sail on what appears geometrically to be the "wrong" tack for long periods. The progress may or may not be worse, but the comfort factor is important for short handed crews (who are not in that much of a hurry anyhow!).

All quite different than racing!

Jim

[monte]

When you can beat the other boat
http://www.sailracer.net/windgame/

[jrbogie]

Originally Posted by Jim Cate

As I read it, the OP was interested in a cruising situation, not a short race with an established course and starting line. Cruising often involves fairly distant destinations or in his parlance, waypoints. When a destination is many hours or days away, lots of the rules of thumb used in racing are inapplicable, for the winds and currents to be encountered are unknown or at best only approximations. So, our practice is to stay somewhere fairly near the rhumb line and to respond to local variations fairly slowly. Tacking on every header gets pretty old in a cruising environment!

Also, in the open ocean, wave patterns from distant origins may be quite different from the local wind waves. This can make big differences in comfort and speed on the different tacks, and can lead us to sail on what appears geometrically to be the "wrong" tack for long periods. The progress may or may not be worse, but the comfort factor is important for short handed crews (who are not in that much of a hurry anyhow!).

All quite different than racing!

Jim

simply put, jim, you read it differently than I read it. i'll paraphrase how I see his question. "when cruising how can I make the BEST VMG TO WEATHER?" nothing, absolutely nothing is more important in racing, whether around cans in the bay or the transpac to Hawaii, yep, done that too, than VMG and how one obtains the best VMG does not change simply because the voyage doesn't start with a horn blast and end with the boom of a cannon.

sure, when i'm cruising long or short distances I enjoy my comfort. I don't even think about tacking on every header and i'll often bear off for the comfort and safety of my companions but I do so knowing that it has a negative effect on VMG. hell, I'll even gybe and run if conditions demand so long as I have sea room to leeward but such a tactic simply won't work in answering the question. and of course he is free to correct me if I've taken his question in a manner different than he intended but his reference to computers and math problems leads me to think that he's well aware of comforts at see and now is interested in getting to where he's getting to and getting there PDQ with best VMG.

[Jim Cate]

jr, I guess that we've answered different questions, and only the OP can decide what he was interested in.

But I have never set out on a cruising voyage by running the start line to determine the favored tack as you seemed to be advocating. As I said, actual sea conditions can over ride geometry at times in determining how to get to windward on long legs.

Jim

[Sandero]

Of course there are a bunch of factors to weigh. tacking slows forward progress and so constant tacking to stay on the rhumb line seems kinda dumb.

If you have sea room and conditions are pretty constant.... then longer legs/tacks makes the most sense. If the wind is moving back and forth you simply trim. If it trends on way maybe that's the time to tack.

Of course on very long tacks you can sail into new conditions, weather and currents... so it can be "iffy" and probably why staying relatively close to the rhumb line makes sense.

When I was beating on long runs (YUCK) I would usually take once every hr or so.

Obviously there are conditions where you can head off and sail around unfavorable conditions. Problem is knowing this for certain and having reliable information in advance. If you know you are going to see a change which is a lifter... in several hrs, you can take advantage of that by heading off and then tacking to take advantage of the lifter.

Most of the coastal sailing we are doing these days... has the fairly strong ebb and flow as a driving factor... and it get's weird closer to shore and so on. It's like sailing across a huge drain with various obstructions... and variable wind speed and direction throughout the day. All in all current is what drives our sailing plans.

[Sandero]

Of course there are a bunch of factors to weigh. tacking slows forward progress and so constant tacking to stay on the rhumb line seems kinda dumb.

If you have sea room and conditions are pretty constant.... then longer legs/tacks makes the most sense. If the wind is moving back and forth you simply trim. If it trends on way maybe that's the time to tack.

Of course on very long tacks you can sail into new conditions, weather and currents... so it can be "iffy" and probably why staying relatively close to the rhumb line makes sense.

When I was beating on long runs (YUCK) I would usually take once every hr or so.

Obviously there are conditions where you can head off and sail around unfavorable conditions. Problem is knowing this for certain and having reliable information in advance. If you know you are going to see a change which is a lifter... in several hrs, you can take advantage of that by heading off and then tacking to take advantage of the lifter.

Most of the coastal sailing we are doing these days... has the fairly strong ebb and flow as a driving factor... and it get's weird closer to shore and so on. It's like sailing across a huge drain with various obstructions... and variable wind speed and direction throughout the day. All in all current is what drives our sailing plans.

[thinwater]

If the OP is an engineer, this is something that would have made an easy test question in high school. By now, he should be able to estimate VMG in his head with no more difficulty than you estimate a 15% tip. This is simple arithmetic.

Is he funning us?

[jrbogie]

Originally Posted by Jim Cate

jr, I guess that we've answered different questions, and only the OP can decide what he was interested in.

But I have never set out on a cruising voyage by running the start line to determine the favored tack as you seemed to be advocating. As I said, actual sea conditions can over ride geometry at times in determining how to get to windward on long legs.

Jim

you miss the point entirely, jim. the op didn't ask how to set out on a cruising voyage. he asked when to tack to make best vmg to weather. I gave him the benefit of my experience. specific things he can look for and steps he can take to accomplish that. and because I've and I needn't pull head to wind before a cruising voyage to determine which take make sense to begin on because I've done it so many times I can figure it out before I leave the slip. the last think i'm doing here is telling you how to sail your boat but the op with more miles under his hull than i'll ever see asked a question that I think many cruisers I know might also want to ask because frankly many haven't a clue how to get the most out of their boats.

[jrbogie]

Originally Posted by Sandero

If the wind is moving back and forth you simply trim. .

huh? if you weren't trimmed before the wind shifted you weren't making best vmg to weather in the fist place. why would trim settings change when the wind shifts direction?

[jrbogie]

Originally Posted by thinwater

If the OP is an engineer, this is something that would have made an easy test question in high school. By now, he should be able to estimate VMG in his head with no more difficulty than you estimate a 15% tip. This is simple arithmetic.

Is he funning us?

it is simple arithmetic but he's not concerned with figuring vmg. he wants to know when to tack to make the best vmg.