Planning tacks over a longer trip.

[Tmacmi]

I will be crossing Lake Michigan this weekend and I have not done much long distance sailing. (yes I know that 70 miles is not that long).

I've done this trip before, but the wind heading was cooperative.

During part of the trip (30 miles of it) it appears I may be facing winds well within 40 degrees of my desired heading. How do you create a plan to tack to the destination?

[Wolfe10]

First, a question: Is the wind direction/speed predicted to change during your transit.


If so, use that to your advantage.

[fxykty]

Longer tack first towards your destination. This means that if the wind is coming from 20* to starboard of your destination (eg destination at 000*, wind at 020*), sail on starboard tack first. If the wind changes in the meantime you may not have to tack at all. If the wind stays steady then at some point you will end up dead downwind of the destination and will need to tack.

If you do have to tack, do it on wind shifts - as your heading gets pushed further away from your desired course, tack. For a while your heading will be closer to your desired course. If over time the wind shifts back and you are again pushed further away from your desired course, tack again.

When you’re far away from your destination your tacks can be long (several hours each). As you get closer to your destination your tacks will be shorter.

There’s lots more information to make this even more complicated, but the bottom line is always sail the longer tack by selecting the tack where your heading is closer to the destination than the other tack.

[Dave_S]

It depends on the characteristics of your boat. Some boats sail well at 40° true. My boat would be happiest around 50-54° true so I would sail at 10-14° COG (a bit worse for windage) off target. If the conditions were stable I would tack once if they were not stable I would tack more often. If I knew which way the breeze would turn I would try to position myself to make the best advantage of that change (and then the change wouldn't come until you are anchored of course).

[s/v Jedi]

I recommend a course for coastal navigation, which includes passage planning like this and also with tidal currents. Not sure where you are based, but for me passing the exams for this also gave me a certificate of competence which is required to enter some countries.

[DEAN2140]

fxytky has the right idea. Figure the rhumb line to your destination and sail which ever tack is the closest to it. When that changes, tack.

[JPA Cate]

A lot of the answer depends on whether there is a wind shift predicted for later on that you can take advantage of.

Here's an example: there's part of the Ozzie coast that in summer receives a mid day shift from roughly SE to NE winds. If you're wanting to go south, then, you head out on an easterly to northeasterly tack, and let the wind head you, eventually heading towards your selected anchorage for the night. You might get to use the chute on the shift.

Your trip sounded as if you anticipate it being more or less on the nose for 70 miles. It's a 28 ft. boat, so 14 hrs. if you could sail the rhumb line. I guess you'll be leaving early in the morning to assure a daytime arrival. Let's assume an average speed of 4 kn. , and because you'll be tacking, add the additional distance you shall have had to travel because of the tacks which is about 2/3 more than the rhumb line distance. If you encounter any favorable or unfavorable currents, you should factor them in as you go, also. The minimum distance without current assisting, would be 106 n. mi., which will be an overnight sail for you, at ~27 hrs.. Winds and currents will possibly change during that period. Yes, start out on the favored tack, and plan to tack least when someone is off watch and more when both are up and won't be disturbed, and to arrive while the sun is still high (setting in the west means it will be really glarey in your eyes). If it were me, I'd like about a 2 PM arrival, or even earlier if there is much work to be done at the end.

Preserving rest is VERY important for shorthanded crews.

Enjoy the trip.

Ann

[Sparx]

In addition to lots of good info above...

I find it useful to know if a low pressure or high pressure system will cross the boat's path. In the northern hemisphere high pressure system winds rotate in a clockwise direction, while low pressure winds rotate in a counterclockwise direction. We use this to inform our planned course.

70 miles may be not long enough to fully ride a front, but understanding what's going on up there will be helpful.

[Dave_S]

Originally Posted by Tmacmi

I will be crossing Lake Michigan this weekend and I have not done much long distance sailing. (yes I know that 70 miles is not that long).

I've done this trip before, but the wind heading was cooperative.

During part of the trip (30 miles of it) it appears I may be facing winds well within 40 degrees of my desired heading. How do you create a plan to tack to the destination?

The way I understand it, there is only 30miles upwind?

[Donnybrook]

Where are you sailing from/to? I sailed from Chicago to South Haven a couple of weeks ago and had a glorious sail!

I use qtVlm (https://www.meltemus.com/index.php/en/) for route planning. It predicts tack/gybe points and even where I might motor if I can't maintain a defined speed. It's free software and makes it easy to download weather gribs from Saildocs.

Here's a screenshot of the route I'd expect to take from South Haven to Chicago leaving at 8 am Saturday. It's based on the GFS weather model.


This is a summary of the trip.


I agree with fxykty's advice to pay attention to progress and wind shifts. Actual conditions often very from the prediction. The route for my South Haven trip, for example, predicted light winds and a lot of motoring, however we had better than expected winds and we were able to sail the entire trip.

[Tmacmi]

Thank you all. Your tips clicked it all in my head. After a while I could get a good understand of when to tack based off my current attack angle to the wind and then using that to estimate how far or under the rhumb line to make the tack. I also was able to see a wind knock to the south that indicated we should make the tack north. There was also a predicted wind shift from NE to N that never materialize, so we had to work with that.

It took us 11 hours to go west and 18 to go back.

Still a lot to learn, but a good start.

Originally Posted by Donnybrook

Where are you sailing from/to? I sailed from Chicago to South Haven a couple of weeks ago and had a glorious sail!

We sailed from South Haven to Racine. I highly, highly recommend Reefpoint in Racine. Its the best marina I have been to. I also recommend Salute for Italian food in town.