The coming days will be exciting for the latest generation of the Imoc60. It will be the first time that these flying machines have to prove themselves in the extremes of the South Sea. Each of the new boats was designed, tested and built for the Vendée Globe, which will be sailed down here for about 30 days and possibly decided.
But why is the "Grand Sud", as the French call this most open piece of ocean, so extreme? It is due to the lack of land mass in the southern hemisphere. South of the three capes to Antarctica, there is next to nothing that slows the wind and waves. As a result, when low pressure systems are circling, they are barely stopped, allowing a huge lake to form over thousands of miles. Due to the cold south polar air and the resulting higher air density, gusts also have a stronger effect than in more moderate areas.
Yesterday and during the night the head of the fleet was overtaken by the front of the first cold front. Charlie Dalin on "Apivia" is still far ahead and will possibly be able to extend his lead a bit, who can sail with and in the cold front longer than his pursuers.
Figure 1: The wave height at 00:00 UTC for Monday, November 30th. A swell of four to five meters is approaching the leading group - bad for the boats with foils, which can then no longer exploit their advantages
In the passage through the front, the wind has turned from northwest over west to southwest, so that after a jibe yesterday the front runners are now sailing east-south-east on the port bow. However, this is associated with a large swell of four to six meters in height, which has developed with the low pressure. Cross lakes are formed by the change of wind direction, closer to the Cape of Good Hope also due to the Agulhas Current. When choosing the tactic, this will have to be taken into account in the coming days, as the boats with foils in particular are heavily influenced by the sea.
You have to think of it as if an airplane were getting into turbulence: it trembles, jerks, falls and rises with the unsteady air currents. It is the same with a wave with an imoc with hydrofoils. With increasing altitude, the boat crashes more strongly into the lakes, the foils cannot maintain a constant flight altitude - this would require adjustable horizontal flaps on the oars, which are prohibited according to the Imoca class rule.
Life on board becomes really difficult, and even the simplest tasks take a lot of strength because the skippers always have to hold on to avoid being thrown through the boat. But it's not just about protecting yourself: the boat and its structure also suffer considerably. The forces on the rig and hull increase massively in the waves, which has already led to the first failures and damage. In order to maintain the boat, the sailors have to slow down - not easy when you have competitors nearby and aim for a good placement or even victory.
The shape of the hull and wings also affects how much the swell affects the boat. In the coming days we should be able to get an idea of which boats are best designed for the conditions in the Southern Ocean. Although months and years have passed to test the Imoc60, the new designs have never been in the conditions of the Southern Ocean.
The weather outlook for the front runners looks pretty promising and fast, which has been lacking in this race so far. Four years ago, Alex Thomson set a new record for the route from Les Sables-d'Olonne to the Cape of Good Hope: 17 days and 22 hours. For comparison: Charlie Dalin will need more than three weeks for this.
The leadership group will be able to hold onto the low pressure system they are currently in until about Friday and to sail with a wind of 20 to 30 knots from the southwest. It will be a wet and wild ride with little chance of a break.
What makes these boats and this race so extreme is the intransigence. The skippers have to deal with the unpleasant conditions 24 hours, 7 days a week. If you see a weather forecast that is current, you will on the one hand be grateful for the quick conditions, but also restrained in your enthusiasm because you know or at least can guess how much will be demanded of you.
It is the time when they pray that nothing will break. In contrast to the first three weeks of the race, during which there were repeated periods of rest for necessary repairs, these opportunities will be rarer in the Southern Ocean. There are only a few islands where the sailors could anchor their boats and each stop would certainly be costly in the ranking because the rest of the field is so fast.
Boris Herrmann on his "Seaexplorer - Yacht Club de Monaco" was a good example of this. Before the weekend, one of his latch locks jammed, preventing him from recovering the coiled gennaker. He knew that the next morning there would be stronger winds. So he used his only opportunity to climb into the mast and repair the lock shortly after sunset, when it was already getting dark.
The latch lock, sometimes referred to as a "hook", is used to fix the sail head to the mast. In contrast to cruising yachts, the sails on an Imoc60 do not hang on the halyard; because of the high load there would otherwise be the risk that the cordage could become shame over time and eventually break. There would also be more compression pressure on the mast. That is why all sails are attached to latch locks, including the large one.
Figure 2: Upper part of a latch lock with which the headsails are fixed to the mast. The halyard runs through here and onto a precisely fitting profile that is connected to the headsail head. If this engages in the lock, the case remains load-free. When locking and unlocking, however, there can be problems, as was the case on several boats last time
The principle of how such a latch lock works is as follows: A profile piece is attached to the head of the sail which fits into the latch lock like a key and is automatically locked with it after the sail has been pulled up on the halyard. To release, you put slack on the luff, pull the halyard, unlock the latch lock and then you can recover the sail. Here is a video from Karver on how it works.
However, the mechanism can sometimes block - this is exactly what happened to Boris Herrmann. Then all that remains is to climb into the mast and manually loosen the hook - a difficult maneuver, unthinkable in the conditions that now prevail in the Southern Ocean.
After Boris fixed the problem, which cost him a few nautical miles, he is now fighting again to catch up with the top boats. In the end he couldn't quite keep up with their pace - which is probably due to his choice of sails for the South Seas. In contrast to many other skippers, he opted for a J1.5 or Jib-Top (136 sqm area) instead of an FR0 (Fractional CodeZero with 170 sqm sail area).
Figure 3: Ensemble routing based on the data of the GFS model. The routes are pretty close together, so there is a lot of certainty about the weather in the following days. The orange marks the Antarctic exclusion zone (AEZ), in which the fleet is not allowed to sail due to the danger of ice drift. The red bulge shows the most recent extension to the north
At the weekend he was probably a little slower in the wind range between 22 and 27 knots because he set less sail area than Sébastien Simon on "Arkéa-Paprec" and Yannick Bestaven on "Maître Coq". With more wind, however, he should have much more control over the boat. Boris's experience shows in such moments. Having sailed the world three times already, he knows his own limits well and sticks to them to ensure a consistent race.
The week promises continued "lively" conditions. In about five days, another low will be approaching the first. It's pretty weak right now, but it looks like it's just intensifying as it approaches the lead group. It could bring a storm.
Figure 4: Although the Vendée Globe has been slower than expected so far, the routings promise better etmales for this week. The head of the fleet will sail at the current low until about Friday. After that, a second depression pulls in very quickly. The leading skippers will jibe along the exclusion zone
At this point the front runners will be close to the Antarctic Exclusion Zone (AEZ), which was moved further north by the race committee last week after some icebergs were sighted. This has lengthened the course. It is therefore to be expected that the fleet will remain close to the AEZ - but at the same time keep an eye on the trajectory of the subsequent low in order to limit the risks that this entails.