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Old 11-11-2015, 15:05   #1
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Tacking 101

Ok, so having just clocked up our first 5000 miles I thought it was high time I learned to sail.

Tacking. When to do it? Most efficient way to get where I want to go?

For some reason I just can't seem to get my head around when I should be tacking. What is the best overall strategy(s) to use?

Basically all we are doing at the moment is trying to stay on the tack that gives us the best VMG to the next waypoint but knowing how to recognise when that changes from one tack to the other seems to elude my mind and its more like, "ok, lets try the other tack and see how that goes." Sometimes it works, other times, not so much.

I read somewhere that if working direct to windward, use a set of lines 5 degrees each side of the rhumb as your guide lines and tack between them toward the goal. Is there any sort of trigonometrical (never thought I'd use that word in a sentence) basis for this or just a rule of thumb? Are there other such rules of thumb where a set of guide lines can be applied?

Does tacking strategy change if your tacking angle changes due to current, sea state etc? We make angles of 90 deg in ideal conditions but it is probably more like 100-110 degrees on average.

Being a nerd engineer, I have been trying to write a spreadsheet to figure it all out but am getting hung up on the maths and programming. I may have to resort to pen, pencil and graph paper here people so please, before the sky falls, enlighten me with wisdom and understanding.

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Old 11-11-2015, 15:47   #2
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Re: Tacking 101

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!
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Old 11-11-2015, 15:53   #3
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Re: Tacking 101

It all depends on how far to the next waypoint, what tide/current and wind are predicted to do along that course and what obstacles there are along the way.

The fewer tacks you make, the better since you lose speed in the tack, put addition wear on everything during the tack and you need to put physical effort into it. So, the ideal would just one tack, two legs with the tack happening when the waypoint is abeam.

That almost never happens in practice.

But if you are obstruction free and current/wind shifts are expected to be negligible, it it quite appropriate to sail on one tack until you reach the "lay line" i.e. the line on which you can "lay the mark" without tacking again.

When cruising, I make as few tacks as possible and don't mind getting many miles off course. When racing I tack a lot
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Old 11-11-2015, 16:18   #4
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Re: Tacking 101

This is so situational that I don't think there can be a rule of thumb.

In a steady wind, no current situation the best approach is to stay on one tack until you can lay your mark on the other tack. That gives the fastest time to mark because the tacks are where you lose speed. You've still sailed the minimum distance, and done it with the smallest possible number of tacks, hence the best time.

Of course, if the the wind shifts while you're way off to one side you're hosed, hence the common advice to stay close to the rhumb line, but the only reason to do that is to hedge your bets on shifting winds.

But how often is wind steady, and current nil? Then you have to do things like tack on headers, take advantage of current distances, etc. All of that will depend on the individual situation, and that is what makes an experienced sailor; being able to evaluate the situation and select the optimum course.
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Old 11-11-2015, 16:27   #5
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Re: Tacking 101

As mentioned it all depends on circumstances, distance to target especially, or setting yourself up to take advantage of a shift.

All things being equal you tack on headers (which will be lifts on the opposite tack), how much of header depends on the boat, how much speed (distance) you lose on the tack, etc. If you have true wind angle indicator you can just add/subtract the number X 2 to see what your other tack will look like.


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Old 12-11-2015, 17:37   #6
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Re: Tacking 101

The best way to learn is to spend some time on a racing boat.
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Old 12-11-2015, 18:39   #7
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Re: Tacking 101

Over years of observation I believe the number one mistake made with tacking is to tack too soon. This then leads to either needing an extra tack or pinching to the next location.

Sailing with great racers and poor racers, it has been this one item of behaviour that is most apparently different between the two groups.

So as Steveinmd suggests, spend some time with racers but try to get on board with the good ones. You may be surprised at how late they tack.

As a general rule on our boat I wait till the point I want to reach is at about 115 degrees before I tack. But I am not racing and comfort is the name of the game for me.

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Old 13-11-2015, 11:16   #8
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Re: Tacking 101

Staying within 5 deg of the rhumb line seems really tight, unless your destination is on the other side of the ocean. I would normally be much wider than that. It is not just the action of tacking that slows you down. Everyone will admit that it takes time to get back up and completely comfortable at top speed in the new direction.

But you definitely do not want to go out to the layline because you give up any opportunity of taking advantage of a lift or shift in wind direction.

What you really do is watch for varying winds across the water. Once you get used to looking, you will see them much better. "Oh look. The wind is a little stronger 1/2 mile to the port." or "Darn, I just sailed into a bit of a lull and I've dropped from 6.5 to 6.2. I saw it coming but I didn't do anything."

Wind is constantly changing, even on a large lake or an ocean. So the best thing you can do is start watching for those changes, and learn from them, and then plan your tacks accordingly. I predict that in another 5,000 miles or so you will have become reasonably proficient. I've been sailing for a long time and I still sail into lulls every time I stop paying attention.
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Old 13-11-2015, 11:40   #9
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Re: Tacking 101

As others have said, current can be a big factor. If you can stay in the strongest part of the current when it is with you and out of it when it's not, you are going to get where you are going faster.

As far as wind goes, I'm not sure if this is what the OP is after, but here's what I have seen...

The wind is usually is either 1) a constant clocking or backing wind direction or 2) oscillating direction. If you think it is #1 then don't be afraid to sail into a header for a while until the opposite tack really helps you. Draw it out on paper and you will see what I mean. If the wind is oscillating (#2) care fully trim your headsail and drive by the telltales. At the same time watch the compass. Write down your course readings, carefully watching for high readings and low readings. Racers often write in pencil directly on the deck - it washes off. Soon you will start to notice when you are in a header or lift. Do this on both tacks and tack appropriately. Sometimes it helps to have one person drive and one write down headings. If you are not carefully driving to the telltales this method will not work.
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Old 13-11-2015, 11:50   #10
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Re: Tacking 101

There are two "indicators" you should learn to use.

For a close waypoint, use the VMG feature on your GPS. You will then, of course, need to compare it to your tacking angle and the wind conditions.

For a far away waypoint, finding the 5 degree cone (I learned it to be 20 degrees from Hiscock's books), you set a waypoint 1,000 miles (yes!) dead to windward and work within that cone; when you get to the layline, you tack. Of course, the wind changes, so you have to keep your head outside the boat.
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Old 13-11-2015, 15:43   #11
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Re: Tacking 101

Good advice, all of it. I watch the buoys ahead of me on my phone. If I am going to be getting headed in the next 50 miles or so, I wait till I am loosing ground on this tack (as opposed to the opposite tack), then turn her over. The more the wind is against you, the faster you should go into a tac. Coming about in 20 plus knots of wind I need at least 3 knots of speed in my boat ( every boat is different.)
Finally, if the wind is up and its at night, or a sail change is anticipated, I get someone up to help me. Don't be a overboard hero.
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Old 13-11-2015, 19:22   #12
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Re: Tacking 101

As always, thanks for the input folks.

The 5 degree cone idea came from a book by Tom Cunliffe. It seemed a little tight to me also but to make sure there is no confusion, he is talking specifically about heading dead to windward.

Reading that section of the book again, he emphasises staying on the favoured tack as much as possible. Tack if headed and jump on to any lifts.

I also seem to recall reading/hearing that it was better to stay upwind of your rhumbline (ignoring predicted shifts, currents etc)

Quote:
Originally Posted by Stu Jackson View Post

For a far away waypoint, finding the 5 degree cone (I learned it to be 20 degrees from Hiscock's books), you set a waypoint 1,000 miles (yes!) dead to windward and work within that cone; when you get to the layline, you tack. Of course, the wind changes, so you have to keep your head outside the boat.
This is interesting. Am going to grab some graph paper and pen and draw out some scenarios to try and get the picture in my head.

Winf
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Old 19-11-2015, 14:07   #13
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Re: Tacking 101

Maybe this thread will help:

VMG - rhumb line vs. banging the corners

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Old 19-11-2015, 14:26   #14
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Re: Tacking 101

Quote:
Originally Posted by Winf View Post
Being a nerd engineer, I have been trying to write a spreadsheet to figure it all out but am getting hung up on the maths and programming. I may have to resort to pen, pencil and graph paper here people so please, before the sky falls, enlighten me with wisdom and understanding.

Winf
Being an engineer, you can use Sin and CoSin functions to compute distance to the mark for various tacking angles and degrees of wind shift.

If memory serves, Ann and Stu and I went through this exercise awhile back but I can't recall the thread.
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Old 19-11-2015, 14:34   #15
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Re: Tacking 101

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Originally Posted by OldFrog75 View Post
Being an engineer, you can use Sin and CoSin functions to compute distance to the mark for various tacking angles and degrees of wind shift.

If memory serves, Ann and Stu and I went through this exercise awhile back but I can't recall the thread.
Found it:

Trigonometry question...
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