IMOCA 60 2022

Charlie Dalin is about to crush the rest of the IMOCA fleet in the first race of the season. Apiva is about 12 hours ahead of Charal, and a day ahead of the rest. This is a 1000 nm race that started 4 days ago. Conditions let him stretch his lead the entire race.

Tracker - Guyader Bermudes 1000 Race https://www.imoca.org/en/guyader-bermudes-1000-race

 

The launch and the first Sailing of the new PRB / skipper Kevin Escoffier :



Runs of speed before the Guyader Bermudes, showing the various foiling attitudes :

 

Do these still have canting ballast keels? Oops. My question was just answered.

 

Vendee Arctique live start.

Tracker - Map tracker - rankings | Site officiel de la Vendée Arctique-Les Sables d'Olonne 2022 https://www.vendeearctique.org/en/map-tracker-rankings

 

The top 5 are presently at 27 to 29 Knots in a reaching sequence. To note that the current 1st "Bureau Vallée" is the ex-Occitane, a Sam Manuard design with a scow bow (within the rules) , and the current 5th "Guyot Environnement -Water family" is the previous Hugo Boss second of the Vendee Globe 2016 with Alex Thomson (also quasi winner of the Route du Rhum 2018), a still fast boat now driven by Benjamin Dutreux the revelation of the last VG 2020. Alex last Hugo Boss, unfortunately forced to abandon in the VG 2020, is now "Hublot" driven by Alain Roura.

 

For English speakers, I ran across a nice interview with Pip H. that has a nice quick review of the design differences of most front of the fleet favorites -designer, original vende round, foil config...
She also covers the difference between Vende focused, and IMOCA focused programs. IMOCA push to win, Vende push to finish for the qualifying miles.

(302) Pip Hare & the race around Iceland - YouTube

 

Quite interesting map-tracking presently, with an unexpected leader the non-Foiler "Monnoyeur-Duo for a job" / Benjamin Ferre, Apivia/Charlie Dalin second, and the followers quite far behind , most being glued in light winds , + some trying the East route still windy.
Map tracker - rankings | Site officiel de la Vendée Arctique-Les Sables d'Olonne 2022 https://www.vendeearctique.org/en/map-tracker-rankings

 

The deterioration of the weather conditions in the North Atlantic have forced the organisation on the Vendée Arctique Les Sables d’Olonne race to make a difficult decision. The race will be neutralized after passing through the virtual gate located in the southeast of Iceland.
For safety reasons the Vendée Arctique Les Sables d’Olonne race is neutralized | Site officiel de la Vendée Arctique-Les Sables d'Olonne 2022 (vendeearctique.org)
3 boats have already crossed this virtual gate, successively Apivia, Charal and Linkedout. Charal still waiting leeward the coast, Apivia and Linkedout have choose to shelter in a Fjord, waiting for the new race departure. The second half of the fleet currently in the strong winds !
Newsfeed | Site officiel de la Vendée Arctique-Les Sables d'Olonne 2022 (vendeearctique.org)

 

Decision finally taken to stop the race at this Iceland gate, so Apivia/Charlie Dalin is the winner, a great performance after his previous victory in the Guyader-Bermudes one. 13 boats already crossed the line (Medallia/Pipe Hare 13th), and 10 are still in the strong winds. 50 Knots sequences with gusts at 60 were reported.

 

Hi,

Having my ankle broken, I feel able to useless occupations only... so tried to solve the puzzle of design an IMOCA boat that satisfies the current rules with the maximum use of foils.
Please criticize the result...

For many years, the IMOCA rules seem to prevent the boats from full foiling. The experiments were made, the simple modification of rudders (i.e. adding T-foils to them) makes a hull-flying foiler of any present IMOCA boat (see https://www.boatdesign.net/threads/fully-foiling-imoca-60.66063/), but the class rules explicitly ban this. The boat has to drag her stern on the water.

This is obviously a wrong configuration. At speed, the bow is lifted up, which increases the angle of attack of the foils. As a result, the foils tend to lift out of the water, ventilate, and increase the drag, unless their lift is not very big. The 5deg rotation degree of freedom, allowed by the rules, helps a bit, but still the pitch stability limits the lift of the foils.

Maybe, instead of dragging the stern, make a deep, planing bow? - No, this would be laterally unstable. When heeled, the lee foil will decrease its angle of attack, and the boat tends to capsize. So, the "taildragger" is the better option.

So, what is the solution? My idea is a deep-V stern, that can substantially change the draught, depending on the load. Together with the 5deg rotation of the foils, this can maintain the horizontal trim, even for 90% of the boat weight carried by the foils.

The resultant hull is as narrow as 2.7m. The righting moment is provided entirely by the foils. Among various shapes of the foils, I chose the simplest one: the Hugo Boss-like circular arch foils with tapered tips. You can lift the windward foil, leaving the tip in the water, which produces a strong righting moment with some lateral stability, without any heel. The canting keel (not necessary here, but mandatory) helps as well.



However, the standard 27m high mast with full sails is much too high for this layout. As it is impossible to cut the mast, I decided to use triangular mainsail with moderate area and low center of effort. Not optimal with respect to the use of the mast height, it is close to optimum with respect to the heeling moment.



The performance was estimated using Michlet to compute the hull drag, XFLR5 for hydrodynamics of the foils, and educated guess for aerodynamics. It's obviously a very crude approximation, but looks not bad...



Of course, this weird concept makes a sense under the present class rules. If the new edition allows the T-foiled rudders, it would be probably worse than the modified present boats.

regards

krzys

 

Thanks for presenting something to ponder.I can understand where the steady state performance may be achieved but suspect that there may be occasions when disadvantages appear.I have concerns about what would happen in sub foiling conditions if the boat is struck by a gust;the form stability of the narrow hull isn't that great and the lack of speed would prevent the foils generating much righting moment.The other area of concern is the bow as it cannot have huge reserves of buoyancy and this is very much against the trend of fuller scow type bows that limit the tendency to nose dive.I wonder if a 505 type flare would be helpful.It can be a good thing to have a topic to exercise one's mind and I will certainly be giving this concept some consideration in the coming days.

 

Thank you for your remarks.
The bow volume is actually not as small as it may seem. The width at 1000mm from bow is above 800mm, which is less than the maximum allowed 1200, but still not a stiletto. With the relatively small displacement of the stern and the center of mass as far aft as 6.5m from the transom, I would not bother about the bow diving.
Stability in the non-foiling mode may be an issue; however, with a two-ton bulb on the swinging keel, and low heeling arm, the chance of knockdown should be low.

All that is nothing but an intellectual play. However, one can imagine a 40% scaled "model" i.e. 24' daysailer for one crew. The sailing conditions on, say, Baltic sea are similar to the scaled South Ocean. So, theoretically it could be possible to test the concept without paying millions of $.

regards

krzys

 

I would not be surprised if this was something we would have seen, had the class not gone with canting ballast keels. Basically, the foils provide almost all of the initial stability, while the deep, bulb keel provides the ultimate stability.

This would save a lot of wetted area and give a huge advantage in light winds and sailing against a head sea.

The foil has to be strong enough to take the loads. But even if it broke off, the boat would not be helpless. The sails would have to be deeply reefed.

I think a huge oportunity was missed when the class mandated canting ballast keels. Far better would have been to not only to make them optional, but to allow them only if a DSS foil is not used.

Then, we would soon find out which is the superior technology.

 

The class seems to give up the possibility to find out, what the best ocean racing monohull foiler should look like. In my opinion, the canting keel is an unnecessary complication for the foiling boat, the standard mast is way too high and hence too heavy, the mustache-shaped foils without control surfaces may not be optimal, and, obviously, at least three immersed foils are needed. The wide hull is also redundant. Interestingly, such a boat could be even cheaper than the present ones.

Under the current rules, the taildragger is, however, the only allowed layout. I suspect the present boats are designed to heel so much not only to increase the righting moment, but mostly to decrease the angle of attack of their foils. I hope that my idea of deep-V stern would be better for that purpose. But of course, the change of the rules would be much more interesting.

regards

krzys

 

MYSZEK. Following your crazy idea. It is tempting to go narrower on an IMOCA, if simply to take advantage of the increased length/ aspect ratio of the current foils configuration. The trend in the Class seems to indicate this tendency, with boats flirting a maximum beam closer to 5m, rather than the 5.85M. allowed. Without going further for all the reasons, the logic indicates that it would be surprising to go much narrower. The lack of initial stability can be a serious problem when the foil is caught by surprise, having no time to react in certain situations. The lack of being able to use the whole sail area is another issue, as you mentioned. Personally, for IMOCA, I am looking at 3 figures. The Displacement, in my view the weight has been increased over the past. Probably due to the introduction of foils . The Wetted surface at different angles of heel, based on the hull shape proper. The Righting Moment, based on the point of "decollage" of the foils over the hull. The above balance is complicate and in my opinion not quite achieved as of it yet, especially when you consider the various conditions of the different races under the IMOCA Class.