Tacking To the Mark

[RHenegar]

I brought this up on another thread, but I thought I would start a new thread on this topic. I am looking for feedback, particularly for shoal draft E32 (my boat) and E38s. Here is the typical scenario:

On a close hauled starboard tack with the sails trim in hard and telltales flowing, COG 000[SUP]o[/SUP]T, AWA 35[SUP]o[/SUP], AWS 15k, SOG 6k; in my boat I would have to wait until the bearing to the mark was 120[SUP]o[/SUP] before I tack to make sure I could lay to the mark. A bearing of 115[SUP]o[/SUP] and I likely won't make the mark. Basically in my boat from close hauled starboard to close hauled port tack is about 120[SUP]o[/SUP] COG. This will vary a little with changes in wind speed and other factors but in general 120[SUP]o[/SUP] is the number.

I am looking for feedback from other owners to see how these numbers compare, or how you know when it is time to tack.

 

[nquigley]

data collection and analysis is the key

I brought this up on another thread, but I thought I would start a new thread on this topic. I am looking for feedback, particularly for shoal draft E32 (my boat) and E38s. Here is the typical scenario:
On a close hauled starboard tack with the sails trim in hard and telltales flowing, COG 000[SUP]o[/SUP]T, AWA 35[SUP]o[/SUP], AWS 15k, SOG 6k; in my boat I would have to wait until the bearing to the mark was 120[SUP]o[/SUP] before I tack to make sure I could lay to the mark. A bearing of 115[SUP]o[/SUP] and I likely won't make the mark. Basically in my boat from close hauled starboard to close hauled port tack is about 120[SUP]o[/SUP] COG. This will vary a little with changes in wind speed and other factors but in general 120[SUP]o[/SUP] is the number.
I am looking for feedback from other owners to see how these numbers compare, or how you know when it is time to tack.

You've made the right start - collecting the data. You might also look at using the (free) software, raceQS, to track your course so you can analyze your course later against the tacking angles you measured on board and whether you made your layline, or overlayed significantly.
But, there are far too many variables at play to rely on the angle to the mark as your main deciding input as to when to initiate the tack: e.g., current? (maybe not on a lake), anticipated wind shift if breeze is oscillating in a regular pattern or there's a persistent shift, sea conditions, and tactical considerations. Oh, and the biggie - how good is the crew and helm at getting from one tack to the other and up to speed quickly without loosing height just through the maneuver?
The cost of underlaying a weather mark is so great (two extra tacks at minimum, let alone port/starboard issues if there's traffic) that it's usually best to go a length (or two if you're some distance from the mark) past what you calculate to be your boat's layline before you tack. After all, a little of the extra time spent by 'putting the layline in the bank' is regained by increased SOG if you have to slightly spring sheets close to the mark when you're certain you've overlayed.
Good luck!

 

[Loren Beach]

When to Tack

Before the "age of data" I knew several sailors who made up a piece of cardboard or plastic and taped it down on their bridge deck with bold lines on it in flow-pen. This showed the point where they could tack and clear the mark, rival boat, obstacle, or etc.
The person adjusting the mainsheet was easily able to call the tacking point to the driver, by direct observation.

Of course this was on a river where boats and "obstacles" are very close together most of the time, and there are wind shifts due to shore configuration. Wind direction changes in puffs, as well.
Race "marks" were and are steel buoys or ATN's as they are nowadays called, so there is the added desire to not bang into one (for several reasons).

 

[Christian Williams]

I'd do what Loren says. Just mark a line on the deck where the helmsman can see it. Forget all the other numbers.

A cruising boat can tack in 90 degrees, more or less. Start with a line abeam as a base and correct that.

How close you can tack depends on the sea state, the heel, the sail set, how clean the hull...and the keel.

Old sails kill pointing.

 

[gadangit]

I brought this up on another thread, but I thought I would start a new thread on this topic. I am looking for feedback, particularly for shoal draft E32 (my boat) and E38s. Here is the typical scenario:

On a close hauled starboard tack with the sails trim in hard and telltales flowing, COG 000[SUP]o[/SUP]T, AWA 35[SUP]o[/SUP], AWS 15k, SOG 6k; in my boat I would have to wait until the bearing to the mark was 120[SUP]o[/SUP] before I tack to make sure I could lay to the mark. A bearing of 115[SUP]o[/SUP] and I likely won't make the mark. Basically in my boat from close hauled starboard to close hauled port tack is about 120[SUP]o[/SUP] COG. This will vary a little with changes in wind speed and other factors but in general 120[SUP]o[/SUP] is the number.

I am looking for feedback from other owners to see how these numbers compare, or how you know when it is time to tack.

Hi Rick-
For the purposes of this discussion, I'm assuming boat speed and SOG are the same. If true, 6kts is too fast for close hauled for your boat's waterline length. You need to trade speed for point. We have 30' of waterline and our target speed close hauled is 5.69kts @10kts TWS, 30 degrees AWA which only an Olympian or a robot could do consistently.

A few things to check:
1. Is your forestay too loose? Too much sag will provide power and reduce your ability to point.
2. What condition are your sails in? This may be all you can get.
3. How clean is your bottom? The only foil on your boat pulling you to weather is under the water.

Are you sailing in the icicles right now? I've got sailmaker and racer friends, we could probably sort this out pretty quick in one sail.

Chris

 

[bgary]

AWA 35[SUP]o[/SUP], AWS 15k, SOG 6k

From some very old and tired brain-cells:

TWS = sqrt ( AWS^2 + BS^2 - (2 x AWS x BS x cos(AWA)))

TWA = arcsin (sin(AWA) x AWS / TWS)

...yeah, I know, math-geek warning, but you can do this in a spreadsheet if you want to play with the numbers.

Given the numbers you provided, you're sailing in 10.6 of TWS (true windspeed), at a TWA (true wind angle) of about 54 degrees. The "vectors" shown below (approximately to scale)

In theory, that means you should be tacking through about 108 degrees.

And... in theory, the boat should be able to do better. As Christian says, tacking through 90 degrees (TWA) should be pretty achievable, especially in 10+ knots of (true) wind.

 

[bgary]

Afterthought

Beyond the things already mentioned (sail trim, mast tune, clean bottom, no current, etc, etc...) if you're going to play with the numbers, spend some time making sure your instruments are calibrated.

You can run a measured-mile to check/calibrate knotmeter (if it is a paddle-wheel)
You can then use the speedo (preferably in dead-calm conditions) to check/calibrate windspeed.

very small calibration errors in either of the "speed" elements can drastically affect the way the instruments calculate the angles.

And, note that if you're using GPS for speed, you're not going to have any way to know what your speed through the water actually is, which can also have a significant effect on the math.

None of that will help you sail better angles... but at least it will ensure you're getting good-quality data for your investigations.

$.02
Bruce

 

[Christian Williams]

A tip of the hat to Bruce's computations. I have notebooks full of data, conclusions and recommendations to myself. Racing seems to require that, and it drives everybody bonkers and broke. But with all the data, you still never know why somebody sailed right over you one day and you sailed over them the next.

So I now consider speed an emotion. "It feels like with the new main we're faster." "I'm elated that we tacked when we did to get this shift". "It's not my fault you made me overshoot the layline."

We can tell when we're going fast and when we're going slow. The feeling is the data.

So keep changing the settings until it feels like going faster.

Sure I'm exaggerating, but with all the variables involved pointing or tacking or reaching fast remains a skill. It's like dancing, it changes with the music. We have to listen and move our feet. Now for a rhinocerous analogy, sailing is like a rhinocerous because, well, ok, never mind.

Look, you can make the mark if you pinch. But if you pinch, leeway will make you miss the mark. You sail faster free and by, but faster free and by may get you to the mark last.

How can numbers compute that?

Determine to feel it. I remember being wrong better than any number.

Sounds like voodoo, but we are the best instrument on board.

 

[RHenegar]

From some very old and tired brain-cells:

TWS = sqrt ( AWS^2 + BS^2 - (2 x AWS x BS x cos(AWA)))

TWA = arcsin (sin(AWA) x AWS / TWS)

...yeah, I know, math-geek warning, but you can do this in a spreadsheet if you want to play with the numbers.

Given the numbers you provided, you're sailing in 10.6 of TWS (true windspeed), at a TWA (true wind angle) of about 54 degrees. The "vectors" shown below (approximately to scale)

In theory, that means you should be tacking through about 108 degrees.

And... in theory, the boat should be able to do better. As Christian says, tacking through 90 degrees (TWA) should be pretty achievable, especially in 10+ knots of (true) wind.

View attachment 23640

Your 54[SUP]o[/SUP] and 108[SUP]o[/SUP] number are exactly what I came up with, so I concluded that I am making about 6[SUP]o[/SUP] of leeway on a close reach to get me to 120[SUP]o[/SUP]. That seems like alot. To get to a tack angle of 90[SUP]o[/SUP], AWA would have to be around 28[SUP]o[/SUP] with all other factors excluding leeway being the same. My boat would be pinching at that angle.

 

[RHenegar]

Hi Rick-
For the purposes of this discussion, I'm assuming boat speed and SOG are the same. If true, 6kts is too fast for close hauled for your boat's waterline length. You need to trade speed for point. We have 30' of waterline and our target speed close hauled is 5.69kts @10kts TWS, 30 degrees AWA which only an Olympian or a robot could do consistently.

A few things to check:
1. Is your forestay too loose? Too much sag will provide power and reduce your ability to point.
2. What condition are your sails in? This may be all you can get.
3. How clean is your bottom? The only foil on your boat pulling you to weather is under the water.

Are you sailing in the icicles right now? I've got sailmaker and racer friends, we could probably sort this out pretty quick in one sail.

Chris

So if you are hitting your target, what would be the angle for your bearing to the mark?

 

[RHenegar]

Hi Rick-
For the purposes of this discussion, I'm assuming boat speed and SOG are the same. If true, 6kts is too fast for close hauled for your boat's waterline length. You need to trade speed for point. We have 30' of waterline and our target speed close hauled is 5.69kts @10kts TWS, 30 degrees AWA which only an Olympian or a robot could do consistently.

A few things to check:
1. Is your forestay too loose? Too much sag will provide power and reduce your ability to point.
2. What condition are your sails in? This may be all you can get.
3. How clean is your bottom? The only foil on your boat pulling you to weather is under the water.

Are you sailing in the icicles right now? I've got sailmaker and racer friends, we could probably sort this out pretty quick in one sail.

Chris

I did last weeks on my friends E38. We were last to the first mark. Passed about 8 boats downwind and beam reach legs before we hit the finish. But I have similar experiences on my E32. I'd be interested in talking to your friend. Maybe I have a loose connection between the helmsman seat and the steering wheel.

 

[gadangit]

So if you are hitting your target, what would be the angle for your bearing to the mark?

In the PHRF racing we do in the bay we always overstand. Or rather, attempt to overstand. We don't have a line on the boat, but usually someone eyeballs by looking directly off the beam approximately 90-95 degrees +/- 10. I try real hard to not be the person making the decision as just that amount of distraction when driving screws me up. Tacking our big heavy boat always feels like we are losing time, so I'll take a bit extra sailing distance over two short tacks at a busy mark. All day long. When they start offering cash prizes I'll change my tactics.

The bay definitely has current and sometimes in reviewing the tracks our tacking angles look horrid. And since it can't be my fault, it must be current.

If you are doing the icicles or rum races you should definitely use RaceQs. I re-watched a race last year after what I thought was a bad race for us, it seemed like our last couple tacks were just terrible. I watched the J109 that was on our same line and his looked terrible too and I know he is a better sailor with, ahem, better crew. The current was definitely a factor. So it made me feel a bit better. The lesson being to watch how you are performing compared to other boats as well before you decide it is you.

The low range marker, "E" locally, always has swirling current which can make your tack decision seem wrong. The leg home from E to the start/finish always starts as a close reach and ends as a pinching close haul. And on it goes.

Chris

 

[gadangit]

I did last weeks on my friends E38.

What boat?

 

[gadangit]

What boat?

Sometime around 4 years ago our friends on an E38 (Good Leif) won the GBCA Non-Spin Boat of the Year or something like that award. It is a great boat and very competitive.

Chris

 

[RHenegar]

What boat?

My friend Mike Clark. E-38 Seahorse We did HMR last year on his boat. The 2nd leg 26NM dead up win, had me swearing I would never do another HMR. But bad memories fade in 12 months.

 

[RHenegar]

Sometime around 4 years ago our friends on an E38 (Good Leif) won the GBCA Non-Spin Boat of the Year or something like that award. It is a great boat and very competitive.

Chris

I know that boat. I did HMR for about 15 years in a row on E34 ProReNata, but the owner sold that boat.