How difficult was to escape from a naval battle after engaging into one during the Age of Sail?

Answer:

Very easy, providing the enemy was playing a classic game. If the enemy was "charging" like Nelson at Trafalgar, there would be a lot of losses for the loser. If the wind was changing fast, this could possibly trigger a charge from the enemy or prevent the ships to go out fast, and thus heavy losses could happen.

Explication:

The main tactic at the age of sail, is two lines of ships going alongside each other and firing at each other. If you lose, you just have to move your line and you escape. But for that, there are some conditions:

• Ships must be down the wind to sail fast
• Ships must have the order in time (not easy at the Age of Sail)

There are plenty of examples of ships withdrawing out of range during a ship vs. ship battle. HMS Java vs USS Constitution is one. Constitution withdrew to make repairs before returning to the battle. It could have easily sailed away, but that would have been silly, as it was winning the battle at the time.

The subject of disengagement and, possibly, the subsequent chase is one that fills chapters and even whole books on Age-of-Sail tactics. Determining the possibility of escape involves a large number of variables. This includes, the number of vessels involved on each side, the state of those vessels (age, loading, trim, damage, how clean the hull is, etc), the comparative skill and morale levels of the crews, the nationality of the vessels involved (which determined standing orders, training, etc.), the proximity of allied forces (e.g. other ships, harbours and shore defences) and, especially, the weather.

A book you should read is by Sam Willis - Fighting at Sea in the Eighteenth Century, The Art of Sailing Warfare (Boydell, 2008) which has two chapters on "Chase and Escape". (While the title refers to the 18th Century, much of what is covered will apply to tactics through the whole Age-of-Sail). As he notes -

Once two ships or fleets had made initial contact, one of two things would then happen: they would prepare to engage, or one would flee and the other would chase. It was rare indeed for two ships or fleets to meet and both be intent on action, and usually the aggressive party in some way had to force action on his enemy. The captains of both ships, therefore, now turned their minds to the question of speed.

^{Fighting at Sea in the Eighteenth Century, The Art of Sailing Warfare, S.Willis (Boydell, 2008) pg. 27}

In a engagement between single ships, it's the individual captains who are responsible for the choice of tactics. They decide if and when to break off and attempt an escape from an action, or if they were the aggressor, how and if they make the attempt to chase. Again, there are many factors involved in making those decisions. For example, a British Royal Navy captain always had the Articles of War in mind which required him (on pain of death) to do his utmost in the face of the enemy. Other navies were less focused on the destruction of the enemy, especially if that conflicted with the mission that they were on, which gave their captains other priorities.

In fleet engagements, the captains had less scope for individual action. They had a responsibility to the fleet as a whole and were directly answerable to the admiral in command. Conducting an escape or a chase as part of a fleet was a very different proposition.

The whole purpose of a fleet was to achieve strength in numbers, and that required a certain degree of cohesion. A fleet strung our over miles of ocean posed relatively little collective threat offensively, and could offer little collective resistance defensively; a fleet in close formation, on the other hand, was a fearsome opponent. The basic problem for a fleet in chase, therefore, was that the basic building blocks of fleet performance, the performance of the individual ships themselves, was neither uniform nor reliable.

^{Fighting at Sea in the Eighteenth Century, The Art of Sailing Warfare, S.Willis (Boydell, 2008) pg. 31}

Any captain of a vessel that broke away from an engagement, to escape, without permission or extremely good reason, would find himself in a very awkward position. In theory, the escaping fleet has the option of scattering, which makes it more likely for the faster vessels to escape, but that would doom the slower ones to capture or destruction. There were also other risks -

The dilemma facing the fleet commander in chase, therefore, was to go at the speed of the slowest performer or to sacrifice any hope of cohesion. Sacrificing cohesion was risky; it opened the fleet up to attack and brought with it a heightened risk of collision. If a fleet was committed to a general chase through individual action, with each captain free to do exactly as he saw fit to bring his ship up with the enemy as quickly as possible, the behaviour of each ship immediately became unpredictable. In fair weather this could be problematic, but if the weather turned foul, chaos was inevitable.

^{Fighting at Sea in the Eighteenth Century, The Art of Sailing Warfare, S.Willis (Boydell, 2008) pg. 32}

In a general chase there was also the risk that the fastest vessels of the chasing fleet would get too far ahead of their own companions and risk being defeated by coming up on larger numbers of the escaping fleet. First contact would be the 'hottest' combat, with fresh gun crews and a full complement of guns on each side. So there was the potential for the fastest chasers and/or slowest of the escapers to be significantly damaged (which would reduce their performance) in such a situation.

Ultimately, the ability to escape or not wasn't simply the relative performances of the vessels -

It has been argued that once a chase had been established, with both ships sailing as fast as they could, the only chance of escape for a slower craft rested on 'shifts of wind, squally weather, or the blunders of the chaser'. It is a statement that implies both a passive role for the captain of the escaping ship and a sense of inevitability in the outcome of the chase, both of which are unjust. The outcome of any chase, however ill matched the ships or fleets, was characterised by a marked unpredictability; it was an activity in which everything remained uncertain.
[my emphasis]

^{Fighting at Sea in the Eighteenth Century, The Art of Sailing Warfare, S.Willis (Boydell, 2008) pg. 36}

To answer the final part of the question — was escaping easier than boarding? — you might want to have a look at an earlier question on this site: Was there a way for ships to disengage from boarding actions?. In short, there were significant risks to boarding actions, so, for a ship that is potentially losing a battle, it's essentially a last throw of the dice. If your ship was still manoeuvrable, it was far more sensible to attempt to escape first (and boarding remained an option if that escape attempt failed).

Additional Recommended reading:
Naval Warfare in the Age of Sail, Tunstall/Tracy (Conway, 1990) - Concentrates mainly on fleet tactics.
Seamanship in the Age of Sail, J.Harland (Conway, 2009) - While not about warfare, this gives invaluable information about handling the sailing ships of the period.

This is where the wind gauge becomes critical. Having the wind gauge, contrary to popular perception, was of little tactical benefit; but rather enabled one to prevent the enemy from escaping. This is because being upwind of the enemy allows one to cover him, disturbing the wind and reducing their speed by (I would estimate) 3% or so. Not enough to matter when one vessel type is inherently faster, but more than enough for comparable vessels.

For some superb examples of this, look up the online videos of the 1983 and 1987 America's Cup races off Newport and Freemantle respectively. These are the last two times that 12m yachts competed for the Cup, and as I recall one wag remarking at the time: "no sailor has ever been able to sail a slow boat faster than Dennis Connor can." The way in which Connor maneuvred his slower boat, particularly in 1983, to repeated wins by covering on both the upwind and downwind legs was a beauty to watch.

The above is why sailboat races (except for catamarans) are over triangular courses with upwind, downwind, and reaching legs. Upwind the yacht in front can cover, and downwind the yacht behind can cover, providing opportunities on both for a more skilfully crewed yacht to catch and pass in both cases. The reaching legs then become pure speed tests.

However in a full fleet battle it is impossible for both sides to engage (in line of battle, that is) except on parallel downwind paths. As downwind is considerably slower than a broad or close reach, either side can disengage from such by simply reaching away - at which point they also cover the pursuing fleet; and escape.

Nelson at Trafalgar, in particular though the tactic wasn't new, could create a decisive battle *by sailing on a broad reach into the enemy line, with the weather gauge (see diagram) and, completely disdaining line of battle, engaging just 2/3 of the Franco-Spanish fleet in vessel-to-vessel combat. Notice how the entire trailing 2/3 of Villeneuve's fleet is covered by the British fleet, while Nelson has skilfully avoided having his own vessels cover each other. The light wind that day assisted - as while it slowed the British advance into battle their lead vessels were quite capable of taking the punishment, the light air was even more disturbed by the cover than a slightly heavier breeze would have been.

Note also that the van of Villenueve's fleet, in order to enter the battle, must either turn to port and tack into the line of the approaching British fleet, or gybe away and then tack or close-reach back. Neither will be either pleasant or efficient, and as it happened the battle was all but over before they were able to do so. Nelson truly contrived a masterful plan that gave Villeneuve no good choices as the two fleets started to engage.

From my now deleted comment to another answer:

The slowest point of sail is straight downwind. In ascending speed after a straight run are broad reach, close-hauled, close reach, and finally beam reach as the fastest point of sail.

• straight run

• broad reach

• close-hauled

• close reach

• beam reach

The reasons for this are that on a run there is zero aerodynamic lift, and the boat is simply being dragged by the wind at some speed less than the wind itself. A tiny amount of aerodynamic lift is available on a broad reach, with some of the sails. Close hauled lots of aerodynamic list is available, but one must counter considerable leeway in addition to the hydraulic drag. As the vessel bears off the wind from close-hauled the lee-way lessens and the aerodynamic lift increases, and the vessel reaches full speed.

Now clearly there musty be some intermediate reaches between a (slow) broad-broad reach and a (fast) beamy-broad reach. The point above stands as I know of no precise nautical terminology for describing these, and part of a Master's or Captain's skill is setting a course that best leverages these choices.

To conclude, some may recall the phrase: "running before the wind". I have seen this interpreted as justification for the claim that a downwind run is a fast point of sail. Rather, it refers to a downwind run being the most comfortable point of sail. The boat sails flat with no heel; the crew can gambol freely aboard the vessel; sail changes are infrequent and minor (unlike a square-rigged tack or gybe); the seas are often following and if not calm then at least less disturbing to the vessel's trim; and even the passengers are comfortable and not retching over the sides. All very pleasant, and very unlike the faster points of sail.

Clarifications (mostly from my comments below):

• Re close-hauled please clarify if you are referring to velocity-made-good, which of course is terrible on a square-rig due to the inability to get much closer than 60 degrees to the wind, or actual measured speed relative to the water which I maintain is still fairly fast as, if it isn't, one is not making progress at all due to lee-way and that is demonstrably not the case. My reference is specifically to measured speed over water, the knots measured over the gunwale, which I believe should be clear from context.
  Terminology: Velocity-made-good (VMG) is net speed as plotted on a chart, as distinct from vessel speed (over the water) as measured over the gunwale. Upwind VMG for square-riggers is terrible even at appreciable vessel speed because of their very poor pointing characteristics, often in excess of 55-60 degrees off the wind. The speed references above are to vessel speed because that is independent of the reason why one is on a particular heading relative to the wind. Think of it as the difference between speed towards where you're pointed (what's dead ahead of the bow) and where you're headed (a location on a map or chart).

• Cover has a small tactical effect at Trafalgar by slowing the trailing Franco-Spanish vessels compared to the van. Note all the battle commentaries which speak of how slow those vessels were in forming line of battle, and how this hindered Villeneuve's plan. That's the cover having effect. It's right there in the battle summaries. However it's main effect is in the chase, where the pursuer has both the wind gauge and a long enough chase for the effect to manifest. For a 200 foot mast the effect in even short match races would extend out to perhaps 2000 feet, for a single vessel. The effect for a large fleet is both greater in effect, and much easier to aim at opposing vessels.