Tracking ability - what is it, how to measure?

[zachduckworth]

Hi,

I’ve heard the term “tracking” used, often in conversations about long distance cruising with autopilots and wind vanes, and often in the context of a full keel being better at it than a fin keel. I was hoping for some clarity on precisely what is being described on this term. My understanding now it that it refers to the way the hull shape allows to boat more easily stay moving in a straight line despite wave and swell action, especially when moving downwind. But I don’t know snd wanted to see if there is more to it. Thanks!

[Searles]

Most long keel yachts with a balanced sail plan will hold a course with minimum helm corrections ,this is called tracking,it maybe hard to windward on a reach or run,generally the magic sort for a good cruising yacht .

[GordMay]

Yacht design is all about juggling important aero/hydro dynamic variables, and”tracking” ability [resistance to Yaw ]is only one of several key attributes [* see 6 degrees of freedom of motion].

Tracking ability, or directional stability, is the tendency of a hull to maintain a course, and not yaw [vertical rotation on Z-axis] excessively, or when deflected from its straight-line path [by say wind or waves], it returns to a new straight-line path, although this will not necessarily be in the same direction, as the original path.

As a vessels speed and seaway motion increase, sailboats with less directional stability [upright & upwind, or heeled & downwind] require excessive rudder response, to stay on course.

In the past, better directional stability has been linked to a longer run of keel, and split rigs, that allow sail area to be parceled out, and balanced [Centre of Lateral Resistance, & Centre of Effort] more efficiently.


Today, larger, high-aspect ratio, semi-balanced rudders, with stocks rotating on roller bearings, require less autopilot [or steering vane] torque, and therefore, deliver more course correcting force, more quickly.
However, these contraptions are a non-seeing, non-sail trimming, alternative to a helmsperson, and directional stability still remains a limiting variable, when it comes to cruising-boat performance.

[GordMay]

Since hull/keel, and rig design, are fixed [except mast rake], by the NA/builder, the variables that are easily controlled, by the cruiser, underway, are the sail trim, and movable weight distribution.

[Tupaia]

Tracking is really the result of balance between CE (centre of effort) and CR (centre of resistance).

Assuming the sails are set correctly. On a fin keel vessel the CE/CR could be regarded as "twitchy" the position fore and aft will vary quite a lot and quickly as the boat heals either by wind gusts or wave action. The movement will be much less pronounced on a heavy long keel vessel and because of the slower healing motion can be self correcting.

The same can be said for catamarans. A catamaran will "track" because in order to turn one hull must travel faster than the other. To demonstrate a cat with boards (up) sailing downwind will maintain its course as the CE will always be in front of the CR that will be right astern at the rudders.

[SailingHarmonie]

I don't know of any way to "measure" tracking, but you know a boat has it when you sail it. A cruising boat without good tracking is a pain in the butt for long passages.

Any decent design should balance and sail hands-off without an autopilot when close hauled. Not every boat does, because not every boat is a good boat. Boats that have any lee helm because of poor design or sailtrim are basically impossible to balance.

The real test in tracking is when the wind is from further aft. Not many boats can hold a course themselves on a beam reach, and very few when sailing downwind.

You do not need a full keel to track well. Many modified fin keels and with skeg rudders will do fine. One of the best tracking monohulls I ever sailed was a Hans Christian Christina, not a full keel design. I have sailed a Hughes 40 on a 600 miles passage with no autopilot, just trimming sails--almost all of it hands off the wheel.

Boats with very high aspect keels, spade rudders, and very shallow flat hulls are designed to be highly maneuverable, and this is the opposite of tracking. A good thing on a buoy racer. Not so much on a ocean crossing cruising boat.

[Orion Jim]

On 7/1/15 I was caught in a force 9/10 gale 200nm southeast of Montauk. It blew from the southwest and I was in the Gulf Stream. I just kept reducing sail until my main was dropped completely, my staysail was stowed, and I had just a scrap of my yankee (maybe 30 square feet) sheeted tight and I was able to fore-reach comfortably over seas I estimated at 20 feet.
My Monitor windvane was at the helm the entire time. At some point my airvane came adrift while I was below. To my great relief my boat continued to maintain herself on course despite this complication. I replaced the airvane once the gale moderated since I had plenty of sea room and my current point of sail was the most comfortable under the current conditions.
With a full keel cutter it’s relatively easy to adjust the sails and maintain course on a close reach. Other points of sail take a little work but are manageable.

[Tupaia]

One of the worlds most famous yachts was also one of the worst and was slated by it's famous skipper as being unable to hold a course. Gipsy Moth IV and Sir Francis Chichester.

[JPA Cate]

Go out on a blowy day, get at least 5 mi offshore, set the 'chute, and hand steer. If you are very busy and have to anticipate in ways the autopilot doesn't do as well as you, she's not "tracking" well. If, on the other hand, you have only small and occasional course corrections to make, she is tracking well. (NB, when you surf, the apparent wind will come forward, and you always will need to correct for that.)

Now, this measure is subjective, but it IS repeatable, and your body learns it, so you will have an internal standard, just not objectively quantifiable.

Ann

I don't think I'd try this with a catamaran.

[thomm225]

A few of the boats that competed in the 1968 Golden Globe Solo Non-Stop Round the World Race had their autopilots fail.

They repaired them repeatedly until finally running out of parts.

At this point, they worked with the sails etc. so their boats would sail themselves. They would sleep through the night as their boats continued to track on course much like Joshua Slocum's Boat spray did.

Knox-Johnson's 32' Boat Suhaili was one and I believe Victress a 40' Trimaran sailed by Nigel Tetley was another.

Tetley's Catamaran came apart and sank 1100 miles from the finish. The Southern Ocean having damaged it repeatedly beyond repair.

[El Pinguino]

The secret is in the sail trim. My (moderate) fin keeled boat tracks well in all sea conditions under wind vane - if the sails are sorted. OK all the sea states I have ever been out in .
Downhill simply make sure you minimise and or depower the main and have the headsail doing the work. If she is light on the helm and well mannered when hand steering she will or at least should be equally well mannered on wind vane.

Big difference is that if sails aren't set right and she takes a big sheer when hand steering you can put on as much helm as you desire to bring her back, on windvane ( at least on my boat ) the vane is 'damped' so she will not apply more than about 5º max. So you need to make sure the sails are well and truly balanced.

[El Pinguino]

Originally Posted by thomm225

A few of the boats that competed in the 1968 Golden Globe Solo Non-Stop Round the World Race had their autopilots fail.

They repaired them repeatedly until finally running out of parts.

snip

I think they had wind vanes rather than autopilots.

Speaking from my experience with both my present boat and my first boat that was 'full keel' I think it would be far easier to get a full keeled boat to maintain a good course than a modern boat with a deep fin.

Vito Dumas took LEGH II around the world - first single hander to do it south of the important capes - without the luxury of a windvane.

[skipperpete]

Haha, I had a Spray derivative, it felt like it had reasonable tracking ability but a casual glance over the shoulder at the wake revealed the uncomfortable truth. After I sold that boat and bought a fin keeler that sailed really well I realized how badly that Spray sailed to windward. I did enjoy everything else about that Spray though and ventured into places along the length of the Australian east coast that I would never enter with the fin keeler ( or any other deep draft sailboat)

[Bowdrie]

Originally Posted by thomm225

Knox-Johnson's 32' Boat Suhaili

Originally Posted by El Pinguino

Vito Dumas took LEGH II around the world

Their ability to be "self steered", is not surprising.
Being double enders, the center of floatation doesn't change its fore-and-aft location all that much at different angles of heel.
This makes it easier to get the sail trim in the "groove" on various points and the groove is wider.
Having the CE down low also helps, lower down and spread out is easier to work with.
Tall high aspect rigs are not as forgiving, i.e., they have a narrower operating range, they're fussier.
Mentions have been made about CE/CR-CLR, the horizontal distance between them is called "lead" and is expressed as a percentage of the WL length.
We might say a certain boat has a "9% lead", meaning the CE was ahead of the CLR by 9% of the WL.
Interestingly, many of the old Schooners had negative lead, the CE being aft of the CLR, and many of them had good self-steering qualities, non-cutaway forefoots helped in this regard.
The caveat being the wind, when the wind picks-up you either reef or drop the mainsail, this moves the CE forward.

[thomm225]

Originally Posted by El Pinguino

I think they had wind vanes rather than autopilots.

Speaking from my experience with both my present boat and my first boat that was 'full keel' I think it would be far easier to get a full keeled boat to maintain a good course than a modern boat with a deep fin.

Vito Dumas took LEGH II around the world - first single hander to do it south of the important capes - without the luxury of a windvane.

Wind vane / autopilot samie same.

Jun 8, 2021 — A mechanical autopilot is called a windvane pilot. In English they are called windvanes or windpilots. Their story is very fascinating, ...

After they failed, they set their boats up so they would track on their own.

Knox-Johnson's boat had two autopilot/ wind vanes and both failed.