How often to tack... Angle to destination

[Dave_S]

To follow on from the "Help me improve VMG" upwind thread... Thanks for the input, I must have read it and the links 4 or 5 times now and looking forward to next weekend to try it out.

How often should I tack assuming there are no obstacles, just working on VMG angles to destination V's tacking time losses.

I understand that this will be more an angle to destination rather than a distance. The boat tacks well, I'm still pretty crap at it but just assume we're average.

[Alan Mighty]

1. define a "tacking cone" to your destination. Cone is the wrong word (because cones are 3D objects), but the idea is to define a triangle with its apex at your destination, the triangle defined by a pair of imaginary lines that intersect at the immediate destination, used to optimise an upwind or downwind tacking course and avoid overstanding.

2. those imaginary lines are your laylines. Set the laylines at 10 degrees either side of your rhumbline to your destination in steady winds; at 20 degrees either side of your rhumbline in shifting winds; and 30 degrees either side of your rhumbline in rough conditions.

3. tack when you meet your laylines. Do not overstand. And only under-stand when you have good information about a wind shift.

For a better explanation than mine, read: https://www.skippertips.com/members/1959.cfm?sd=113

[Alan Mighty]

Download and read Ferretti & Festa, 2017, A hybrid control approach to the route planning problem for sailing boats:

https://www.researchgate.net/publica..._sailing_boats

[Cheechako]

Cruising, I tack by watching the heading vs destination, if a wind shift holds for long, go for the favorable tack. Sea state can make a difference though too. Many times as you near land or a headland the wind will shift a lot. Just keep watching for what the wind direction is doing and tack accordingly. Cruising offshore, OTOH, you may be on the same tack for a day.

[44'cruisingcat]

Theoretically, because tacking slows you down, you want to tack as few times as possible, only once if space permits.

In reality doing this would make you vulnerable to wind shifts. (I'm presuming you're racing.)

[billknny]

Originally Posted by 44'cruisingcat

Theoretically, because tacking slows you down, you want to tack as few times as possible, only once if space permits.

In reality doing this would make you vulnerable to wind shifts. (I'm presuming you're racing.)

Why not just tack once? This is why...

Imagine you are sailing to a destination due north of your starting point, with a north wind. You sail off on a port tack to the northeast. Your plan is "to tack as few times as possible" because your theory tells you that is faster. Since this hypothetical sail is happening in the open ocean, you plan is to tack once. So you sail toward your layline, close hauled as best you can.

You reach your layline, and fall over to starboard tack. your destination is now directly under your bow to the Northwest. Moments later, the wind backs 4 points to the Northwest... and you are so screwed. A boat that had tacked more often, staying closer to the original rhumbline would eat your lunch.

There is no simple magic answer to this problem. If you can accurately anticipate a windshift in time or space and tack to position yourself to take advantage of it--then great.

If you can not accurately predict the wind shifts, it is better to stay close to the rhumbline course. If you are very close to the rhumbline, a standing wind shift in ANY direction is favorable to your VMG in the long run! How "close" is close? It depends...

My typical cruising approach for a long upwind leg is to go roughly half the distance to the layline, and then tack, always starting with the favored tack--if there is one. As the destination approaches, and unpredicted wind shifts become less likely, or less annoying if I get headed, I'll of course take it further out.

In the REALLY practical world if you are sailing offshore with long distances and modern weather tools it is not common that you would be tacking upwind for days, totally blind to coming wind shifts you can take advantage of.

[james247]

Originally Posted by billknny

Why not just tack once? This is why...



Imagine you are sailing to a destination due north of your starting point, with a north wind. You sail off on a port tack to the northeast. Your plan is "to tack as few times as possible" because your theory tells you that is faster. Since this hypothetical sail is happening in the open ocean, you plan is to tack once. So you sail toward your layline, close hauled as best you can.



You reach your layline, and fall over to starboard tack. your destination is now directly under your bow to the Northwest. Moments later, the wind backs 4 points to the Northwest... and you are so screwed. A boat that had tacked more often, staying closer to the original rhumbline would eat your lunch.



There is no simple magic answer to this problem. If you can accurately anticipate a windshift in time or space and tack to position yourself to take advantage of it--then great.



If you can not accurately predict the wind shifts, it is better to stay close to the rhumbline course. If you are very close to the rhumbline, a standing wind shift in ANY direction is favorable to your VMG in the long run! How "close" is close? It depends...



My typical cruising approach for a long upwind leg is to go roughly half the distance to the layline, and then tack, always starting with the favored tack--if there is one. As the destination approaches, and unpredicted wind shifts become less likely, or less annoying if I get headed, I'll of course take it further out.



In the REALLY practical world if you are sailing offshore with long distances and modern weather tools it is not common that you would be tacking upwind for days, totally blind to coming wind shifts you can take advantage of.

The variables as to this question are great. If you were in the middle of the ocean then dependant on the distance to be traversed would affect the answer. A day on one tack is physically more than enough. As weather systems move from east to west or west to east dependant on your location. Going out in one direction may negate a benefit.
Coastal cruising has many more variables.
Tide and current - not necessarily the same thing, wind on headlands and the sea state from those headlands, nocturnal and diurnal wind conditions are also a serious consideration.
Plotting a course taking these matters into consideration deserve some planning time. The southerly set of the east coast of Australia as the Gulf Stream Of the east coast of USA make an enormous difference as to your planning.
A 10 or 20 degree lift can take you your destination upto a third quicker. Reading all of the variables is extremely important.

[SSgtPitt]

Was looking forward to reading the Skippertips article, but the $70 fee was a little stiff.

[hamburking]

You always want to be getting closer to your destination. If you hold a tack too long, at some point you will actually be getting farther away from your destination. And there are so many other factors. Current and tide. Shore effects. Anticipating wind shifts. Other boats. Obstacles.

Here are some things to think about when you are out there:

"Wind shift, you shift"

"If in doubt, come about"

[ffelker]

Since this is the "Cruiser's Forum" and not the "Racer's Forum", the question has a simple answer.

Cruisers tack no more than once per day, and then only after careful planning.

[cyan]

We occasionally "attack for the halibut".

If I'm leaning on a "favorable" tack all day in steady conditions, happy with my fancy math and my VMG, I'll throw in a couple tacks every once in a while just for a sanity-check. My guess is that ocean currents are the source of my superstition, but occasionally I get a little surprise when my math fails to accurately predict the VMG on the other tack. This new information helps to adjust the lay lines.

We call it "attack for the halibut". (though my son likes to remind us that you cannot attack a bottom feeder by simply turning a boat)

[catsketcher]

Gday Dave

The question you ask is the racers dilemma - there are many books written on strategy and tactics - Stuart Walkers Racing Tactics is thick with advice. As an ex racer there are many times I use my racing knowledge when cruising.

Staying away from laylines is a great first step. Your boat should be nice to tack. If it isn't make sure you ease the main slightly before you put the helm down. But strategy is not always easy. If you watch the tracker for any race to windward, or even downwind (Volvo or the Melbourne Osaka) you will see the boats often taking different courses - often the experts disagree.

It helps to know the forecast - When I sail up and down the coast, knowing what the wind is forecast to do will help my planning. One really nice dictum is "Sail towards the new wind - but not too far" (Laylines again).

If I am sailing from Brisbane to Mooloolaba in a building summer sea breeze, the breeze will start off (probably) south east or east. Then as it builds it usually turns nor east (going left). The new wind is going to be coming from the left so you head left. Stay near the shore (or at least left of the rhumb line) and do shorter tacks. When the wind heads left you tack on the knock and have a lift on port.

When we sailed day sailed hard on the wind for days to get south from Lizard, we would head out to the reef and do short tacks under the reef in flatter water. Some soueasters never shift so you play the water rather than the direction. Other times I would be hard on the wind heading south (on port) and aiming far below my rhumb line. Usually (but not always) the sea breeze would add a component of east or even noreast to the breeze later in the day and we would lift up to our destination leaving those who tacked behind.

In fast multis it often pays not to sail the rhumb early line if the breeze is going to clock around. I often sail high or low for a few hours at a time, especially in a seabeeze situation, to stay in the groove and come back up (or down) when the new breeze arrives.

Get out on a race boat. Even some beer can races will help you understand what is happening better.

cheers

Phil

[44'cruisingcat]

Originally Posted by billknny

Why not just tack once? This is why...

Imagine you are sailing to a destination due north of your starting point, with a north wind. You sail off on a port tack to the northeast. Your plan is "to tack as few times as possible" because your theory tells you that is faster. Since this hypothetical sail is happening in the open ocean, you plan is to tack once. So you sail toward your layline, close hauled as best you can.

You reach your layline, and fall over to starboard tack. your destination is now directly under your bow to the Northwest. Moments later, the wind backs 4 points to the Northwest... and you are so screwed. A boat that had tacked more often, staying closer to the original rhumbline would eat your lunch.

There is no simple magic answer to this problem. If you can accurately anticipate a windshift in time or space and tack to position yourself to take advantage of it--then great.

If you can not accurately predict the wind shifts, it is better to stay close to the rhumbline course. If you are very close to the rhumbline, a standing wind shift in ANY direction is favorable to your VMG in the long run! How "close" is close? It depends...

My typical cruising approach for a long upwind leg is to go roughly half the distance to the layline, and then tack, always starting with the favored tack--if there is one. As the destination approaches, and unpredicted wind shifts become less likely, or less annoying if I get headed, I'll of course take it further out.

In the REALLY practical world if you are sailing offshore with long distances and modern weather tools it is not common that you would be tacking upwind for days, totally blind to coming wind shifts you can take advantage of.

Apparently you didn't notice that there were TWO paragraphs to my post.

[SaltyMetals]

I usually use XTE for a while until i get closer to my destination, then the laylines are important. Do not over-stand. Having said that, if you are approaching a strong cross current you can throw most of my above and much the other replies overboard. Back to basic, classical navigation, plan your passage bearing in mind what currents you will find at each hour., alternatively try one of the weather-routing Apps like Sailgrib WR. Absolute magic. These Apps Include all the wind changes and current changes. I used Sailgrib WR across Biscay 2 yrs ago and then to Gib. Current factors on that route only significant in English Channel around French N & NW coast. After that our App helped 7lots bec we had W F5-6-7 across Biscay and then NW 5-7 down Portugal. The weather routing programs are worth investigation IMHO.
Andrew

[charliehows]

my two options; 1; set sails, engage engine to improve angle towards destination, tack as few times as possible... or ... 2; sit in bar, order whatever keeps you amused until the wind changes to a more favourable heading.