THE NEW KRAKEN 44 BLUEWATER CRUISER

I confess that the first idea I had about Kraken was a very negative one: the designs seemed outdated and I still think that the choice of having skeg rudders and non-bolted keels is more a publicity stunt than a real advantage, even if most conservative sailors are attracted by those features. You can read more about that here:

Above the new Kraken 44, below, the older Bluewater 44,
by the same designer, Kevin Dibley.

 https://interestingsailboats.blogspot.com/2023/03/kraken-50-versus-pegasus-50-comparison.html

But the truth is that Kraken yachts are well-built, and except for those two items, not in an outdated way. The designs, even if slightly outdated (bow, keel and rudder design), offer advantages (and disadvantages) if we compare them with modern beamy bluewater boats like Hallberg Rassy or Contest.

I was very curious about their new 44ft boat because while they claim to make boats "founded with one objective, to build the best blue water yachts ever launched...a boat crafted For Life (to) Sail across oceans safely and comfortably", the truth is that a couple does not need a 50ft yacht (or over 50ft) to circumnavigate or to do bluewater sailing, neither can they afford yachts with a starting price of 1.5 million euros (the cheaper ones). 

Above, the new Kraken 44, below, the old Bluewater 44

How can the best bluewater yacht, designed for life, be one that has a price that puts them out of reach of practically all cruising sailors, and only at the reach of very healthy people, who are not necessarily good sailors? Looking at it from this perspective, they are more like a luxury item, than a practical offer regarding bluewater sailing and cruising life.

Below, Hallberg Rassy 44

That's why I was very interested in their new 44, which was meant to be what the others were not, an affordable bluewater boat, and one that could be used by a considerable number of sailors for a cruising life, an alternative to other options on the market, even if at a moderate extra cost, justified by a superior quality.

To attain that Kraken chose to base the new boat on a pre-existing older design, made by Kevin Dibley, the designer of all Kraken. The original design has a 13.50m LOA, the Kraken 44 has 13.52m. The BW44 has a 3.78m beam for a 3.83m beam on Kraken. Both have a 2.0m draft, and the keel and rudder design are similar, even if the BW44 had a bolt-on keel, and originally a spade rudder, that became a skeg rudder by demand of the single client.

Kraken 44

Looking at both designs the differences are minimal, being the more noticeable the longer cabin and bigger height on the aft part of the boat on the Kraken, due to the option for a central cockpit, instead of an aft cockpit, as on the original design, and the higher position of the boom, certainly because of the American taste for huge dodgers and enclosures. 

The new design is a bit nicer, mainly due to the cabin design, which seems not to be as high: being longer, because of the center cockpit option, makes it look lower. The longer hull ports disguise better the high freeboard. The underbody is basically the same, with the exception of the older design having a slightly more efficient keel with a torpedo.

The higher boom is not a good thing for sailing, raising the sail center of effort, and is even worse in terms of sail accessibility and the easiness of storing the sail on a sail bag. They could use an inclined boom, lower at the head, a solution that has become increasingly popular, and that is used for instance in the Jeanneau SO 440.

Jeanneau SO 44 inclined boom.

There are some mysteries regarding the dimensions of the two boats. One of them is the LWL which on the original design has 11.2m, while for the new design, they say it has a 12.0m LWL. But looking at both designs and the scale that is on the bottom of the Kraken 44 image, I cannot understand how that is possible. The transom design looks slightly different, and that would increase LWL, but not by 0.8m, taking into account that the bow design remains essentially the same.

Hallberg Rassy 44

But what is really odd between the two boats is the displacement, which is given as 10900kg for the older design and 14597kg for the new boat, and if we consider that the displacement on the older design is a measured weight, it is difficult to understand that huge difference, even considering the extra weight the solution of an encapsulated keel implies, unless the Kraken 44 is not built the same way and using the same materials as the other Kraken.

Take for instance the difference in displacement between the Kraken 50 and the Hallberg Rassy 50, being the Kraken the lighter boat with 18250kg for 20000kg, while if we compare the Kraken 44 and the Hallberg Rassy 44, it is the opposite, with the Krakem displacing 14597kg and the HR44 displacing 13300kg and that is especially odd because the HR has 1100kg more ballast than the Kraken.

Bluewater 44 layout, also a two-cabin two head layout, but with a much
smaller aft cabin and much more storage space accessed from the outside

Even more worrisome is the B/D difference between the BW44 and the Kraken 44. The older design has a 39%B/D, having 4251kg ballast while the Kraken 44, being much heavier, has 51kg less ballast making for a B/D of only 29%, that, associated with that type of keel and draft (both not very efficient), seems to me insufficient for that type of narrow hull, in what regards a very good sailing performance upwind or beam reaching, and in what regards the safety stability and AVS a bluewater boat should have.

Kraken 44 layouts, the king-size cabin restricts the possibility
of having a decent space for sailing material, from fenders to
ropes and all the stuff a long-range cruising boat has to have.

I hope they sort this out because I like the original boat, which I have no doubt has a very good sailing performance. I doubt the same can be said regarding the Kraken 44, considering the dimensions they have released regarding displacement, ballast, and sail area. I hope these dimensions are just a mistake.

In fact, there is much good to be said regarding the original model, the Bluewater 44: the big B/D on a relatively narrow modern hull (if we exclude bow design) allows for a big sail area and excellent performance, especially in lighter winds and upwind, in all winds and sea conditions. I like narrow boats and in regards to sailing in the med, I would prefer this type of hull over the beamy type that is now proposed by almost all builders, and that we can see for instance on the Hallberg-Rassy 44.

The much-beamier hull, even if not hugely beamy by
modern standards, allows for a much bigger interior 
volume and also a much bigger storage space. The 
space for equipment or interior storage is much bigger
on the HR44 allowing for an option of two extra berths.

The Hallberg Rassy beam is much bigger (4.20m to 3.78m), the HR is much heavier (13.300kg to 10 900kg), and has a slightly bigger B/D (40% to 39%). The superior hull form stability, and the superior B/D (with more draft and a more efficient keel) will give it a much bigger overall stability for at least a similar safety stability and similar AVS, but the narrow Bluewater 44 hull offers advantages in what regards drag (less displacement) and wave drag, even considering the bigger HR LWL, due to a modern bow (12.0 to 12.8m).

In what regards SA/D the HR can have 20.5 and the Bluewater 44 21.0. Apparently, this is not a big difference, but it is a difference bigger than what it seems in regards to sailing with weak winds or sailing upwind, due to the big difference in beam. Overall the Bluewater 44, even with a bigger keel and rudder drag, will be faster in most conditions.

For sailing in the trade winds and even for sailing many days in a row, I would choose the HR44. Maybe if I was younger I would have chosen the Bluewater 44, but now, being honest, if I don't mind sailing with considerable angles of heel for a day sail ( I like it), for living in a boat while sailing for several days, being it for sleeping, eating or cooking, the difference in heel between the two boats while sailing will make a huge difference in living comfort. 

Kraken 44 grey hull

And that's for me, who likes sporty boats and sailing with the boat heeled. Even in the med, if cruisers test sailed both, I am sure that most would prefer the HR 44, due to a more moderate heeling. Upwind with medium or strong winds the BW 44 will sail more heeled, but also faster, with a softer motion, pounding much less and being able to close more on the wind.

But most sailors in the med chose not to sail upwind in medium-high or strong winds. Many choose to stay sheltered waiting for better conditions, while others motor upwind. On a bluewater passage motoring is out of the question, at least for a long time, and the BW offers advantages not only in what regards sailing upwind but also in sailing faster in lighter winds. But not even in a bluewater passage the BW44 offers always advantages over the HR44, namely in regards to sailing downwind and beam reaching, with medium and strong winds, the conditions you will find in the trade winds.

Kraken 44, blue hull

So, it all depends on where or how you are going to sail oceans. If you go against the prevailing winds, certainly the Bluewater 44 is a better boat for the job but if you are going to sail on the trade winds, and in the "right" direction, which many times depends on the time of the year, then the HR 44 is from the two, the best to do that, being a more forgiving and easier boat to sail on those conditions, rolling less and being more easily driven in auto-pilot, even sailing fast with strong winds.

For sailing in the Med and the Baltic, I would probably prefer the Bluewater 44, if I could overcome my displeasure regarding how the boat looks, and I doubt that. The cabin and freeboard are just too high for my taste, and all those glass surfaces would make the boat unbearably hot during the sailing season in the Caribbean or the Med, and would have to be closed in the hot summer months. Of course, if you live in a boat for the full year, or if you sail in cold climates those windows can be very handy to let the sunshine in, and warm the boat and your soul. 

Lyman Morse 46

Between Dibley designs, I would have, for sailing in the Med, the Lyman Morse 46 performance cruiser, not the Bluewater 44. I find it beautiful, it is certainly fast and would be a lot of fun to sail, having a good cruising interior for a couple. 

But I am only talking about my personal taste in regards to cruising in the Med and because I was talking about that regarding the HR44 and the BW44. I like speed and sailing fun, and I am way out of the mainstream in regard to cruising boat preferences. 

Above and below Dibley designed Lyman Morse 46

Cruising in a very fast boat implies always a bigger level of discomfort and a more spartan way to live, and regarding preferences, there is no right or wrong. Each one likes what he likes and there are sailing boats adapted to all cruising tastes, having the majority tastes that are reflected in main market cruising designs, the boats that sell more, some of them bluewater boats, others not really, even if they can cross oceans or even circumnavigate. 

The difference lies in being more or less adapted to do that, and in the bigger safety factor bluewater boats can provide, which has to do with being a stronger built boat, with having a big overall stability, bigger safety stability and AVS, offering a more sheltered enclosure to sail the boat with bad weather, a more adapted rigging, better tankage and with being equipped with ways of generating lots of electric energy, even if this is normally an extra, that is only required if that use is given to the boat, and unnecessary for other uses.

Lyman Morse 46, has a very nice cruising interior.

But this article is not about the Bluewater 44, but about the new version of that boat with a center cockpit, now renamed Kraken 44, and even if they look similar, due to the much superior Kraken displacement, the smaller SA/D (only more 0.4 sqm of sail for 3697kg more), the much smaller B/D (29% to 39%), they are very different sailboats, even if they share practically the same hull. They are so different that I really hope there is some mistake here in the numbers given by Kraken.

I asked them for information but they redirected me to the information on the boat site, and these dimensions are what they have there. I am afraid the information is correct because that could explain why both boats have practically the same sail area being the Kraken 44.1% heavier than the Bluewater 44.

Kraken 44

That only makes sense if Kraken 44 is a much less powerful boat than the Bluewater 44. Both boats have practically the same hull, being the Kraken 3.7T heavier. It is as if the stability BW 44 gets by having a much lower CG (much more B/D), was substituted by the stability Kraken gets for having much more displacement (weight increases overall stability). In the end, both can carry the same amount of sail, but the BW44 will be much faster and will have much better safety stability and AVS than the Kraken, due to the lower CG.

The Kraken 44 SA/D is 14.3, an unusually small value today, that compares to 21.0 for the Bluewater 44 and 20.5 for the HR44 (with an optimized sail area) or 19.3 in its standard version. As it is the Kraken 44 is a shadow of what could have been, and without being a bad boat it is not a match for the competition, in regards to sailing potential, overall stability, safety stability, and interior space. I would say also in what regards looks, even if that is debatable.

The Hallberg Rassy 44 has the keel strongly bolted to a stub and
 to the superior structure. They stopped using skeg rudders years ago
and use now, in most models, twin rudders. 

Regarding extensive cruising, the Kraken 44 has a problem: the very small outside and sailing-related storage space, due to the king-size aft cabin, and small beam. The BW 44 does not have that problem because the aft cabin is much smaller, and on the other side of the boat there is an ample storage locker for all the sailing and cruising stuff a long-range cruising boat needs to have.

On the Hallberg Rassy that space is also not big and some will find it unsuited for long-range cruising, but it is incomparably bigger than the one on the Kraken 44, mostly due to the bigger difference in beam, and the beam being carried more aft. The aft lockers are much bigger and the sail locker is also bigger. It has also a much bigger interior space to mount equipment.

In green, the Combi 15KW electric drive engine is mounted
over the Yanmar and designed to work with it.

Due to the much bigger beam, the living space is uncomparably bigger in the HR, which offers more interior storage and also, if there are kids, two additional berths, without compromising the galley or the saloon living space. More about the HR 44 here:

https://interestingsailboats.blogspot.com/2016/03/halberg-rassy-44.html

https://interestingsailboats.blogspot.com/2017/05/halberg-rassy-44-boat-test.html

The sole Kraken 44 argument seems to be its encapsulated keel (and eventually price) and skeg rudder, a weak argument since Hallberg Rassy has thousands of boats on the water, for several decades, and none of them has ever lost a keel or had any problem related to the keel and it offers the superior reliability of a twin rudder system. 

The Kraken 44 estimate price is between 779 000USD and 850 000USD (no taxes at the factory) and includes as standard a hybrid engine constituted by a main Yanmar 4JH57, combined with the Combi 15kW electric drive motor.

For  a good efficiency the system should include a
generator, but I don't know if it will be standard or not.

I would not trust that solution for a bluewater boat. If the system were reliable enough Yanmar would have it as an option in their engines or would have developed its own version. It is theoretically a good idea, but like in cars, these new systems have more maintenance and more malfunctions than traditional systems, including the ones having a separate hydro generator, solar panels and wind generators. 

The option to mount it as standard, on a type of boat that by definition will be many times away from a repair facility (and knowing that around the world the ones that can repair this system are very few), seems to me a bad idea, increasing boat cost.

https://electricboat.co.nz/index.php/product/combi-hybrid-parallel-electric-hybrid-system-for-diesel-engines/

BEST TYPE OF RUDDER: SKEG RUDDER? SPADE RUDDER? TWIN RUDDER?

                                                                                                                        Hallberg Rassy 49

Almost 10 years ago I posted about this subject when two rudder setups started to be applied to almost all cruising boats, a time when many still doubted the efficiency of the system. Today the situation is different, most boats have a twin rudder, but curiously we see now an increase of cruising boats with a  single rudder set up.

Swan 115

On the main market mass-production cruisers many use now a single rudder, and in the last article about 40ft main market mass-production cruisers, there were more using a single rudder than a twin rudder. I believe that in this case this has mostly to do with cost-saving, and not with rudder efficiency. A twin rudder setup is more expensive than a single rudder and on these boats, they cut in anything they can. This does not mean that a twin rudder is always more efficient. There are many top racing boats and top cruiser racers with a single rudder.

https://interestingsailboats.blogspot.com/2023/10/brand-new-hanse-410-compared-with-all.html

X4.9

Rob Humphreys describes here the benefits observed through tank testing that was performed on an Oyster 885 model, and that convinced Oyster management regarding the benefits of using twin rudders on their line of yachts:

"David’s naval architecture background (David Tydeman is the CEO of Oyster Group) quickly helped me persuade him that twin rudders were the way to go! It was clear that this was going to be a bit of a sea-change for Oyster and I was pleased that David was keen to push this onwards and also to support this breakthrough with a decent budget for tank testing.

Oyster 495

We both felt it would be helpful to have fairly tangible reference information for those owners trying to understand the shift from a skeg-rudder to the twin rudder form for this exciting new model.

In fact our testing session set out to do more than just this because we also used the opportunity to let the spade rudder have its say, just for some form of completeness. 

Tank testing twin rudders

We have often been asked why Oyster has tended to steer clear of spade rudders and the answer has more to do with potential vulnerability than any disrespect for its potential qualities. 

As any Oyster owner knows a blue-water cruising yacht has to be accomplished in a number of different ways, and one of the lower profile requirements has to be an ability to slide backwards against a Mediterranean harbour wall without necessarily endangering the steering gear.

Oyster 825

In our tank testing we were focusing our attention on a fully-pressed up set of sailing conditions, with the boat heeled over to twenty degrees and sailing at nine knots, with a variety of leeway angles and load conditions. .. 

We tested a lot of other things as well but the rudder testing part was most interesting and was totally supportive of all that we had learnt to be true in the field. ...

Oyster 825

For example, with the twin rudders set to just two degrees to the flow the spade rudder needed to be at over six for an equivalent moment, and the skeg-hung rudder at eight – all for the same yaw moment. Put another way, the leeward twin rudder provided 4 times as much force than a skeg rudder!..

From our perspective twin rudders represent a huge benefit and an Oyster owner will really appreciate it too as soon as he has the wheel at his finger-tips. But what’s also interesting is that the system fares a lot better in terms of potential reliability, especially against the spade rudder. 

Oyster 825

The blades are significantly smaller and more lightly loaded, and the span is considerably shorter, making it almost impossible to damage the steering gear when reversing into a quay. 

And of course, with two rudders rather than one there is an obvious increase in the level of redundancy. Unlike some twin-rudder installations, the arrangement we have for Oyster means that even assuming the worst-case loss of one rudder it would be possible to still sail the boat on the compromised tack, albeit with reduced canvas."

http://www.humphreysdesign.com/63/twin-rudders-for-blue-water-cruising

Beneteau Oceanis 51.1 twin rudder

This pretty much resumes the advantages of twin-rudders, but that quicker response is translated also in a smaller sensitivity. They have more inertia due to more moving parts.

Besides Humphreys was making the comparison between twin rudder and a typical spade rudder used in main market cruising boats, not a comparison with a very deep high-performance spade rudder, typically used in more sportive boats.

J45 single deep rudder, as in all J/boats

Regarding more advantages of a spade rudder over a twin setup, if you want to make a sharp turn or turn around, the single rudder can do it much faster, and in a much tighter circle, and that is important in regards to manoeuvering at the marina or port, especially if you don't have a bow thruster, and also very useful while racing around marks.

A single rudder is especially adequate for a not very beamy boat.

Dehler 46 single rudder, as in all the Dehlers (except the 30)

On modern ultra-beamy sailboats having a solo rudder implies a deep rudder and that increases the problems regarding med mooring and also the needed boat draft.

Also, unless the rudder is extremely deep (and for that it needs a deep draft) at high angles of heel, when the boat is heeled by a gust or is over-canvassed, the twin rudder allows the boat to be kept under control. All the rudder is in the water and the water flow is centered with the rudder, while on a single rudder, it will be partially out of the water, and the water flow will be passing sideways to the single rudder. In these circumstances, this gives a higher efficiency to a twin rudder setup.

Wally 93

Only sportive cruiser racers or race boats have really deep spade single rudders. Very beamy main market cruisers have relatively deep single rudders but much less deep than on sportive boats, which normally are not so beamy. And when they are very beamy, like Pogo, they use twin rudders.

Main market beamy cruisers are designed to sail with relatively small angles of heel, and in those situations, their single rudders work perfectly well, and can even be more agreeable to steer than twin rudders, but in extreme situations, they will not offer the same boat control as a twin rudder.

Arcona 465

If the boat has a single rudder and is to be sailed in the Med I advise against buying the shallow draft option because the keel can be shorter (with more ballast), but not the rudder, and you will end up with both keel and rudder with almost the same draft.

As the depth near the quay is always less than some meters away you will end up risking hitting the bottom with the rudder while backing instead of hitting it with the keel. The keel is resistant to small impacts while the rudder has a much smaller resistance. If you need a boat with a small draft buy one with a twin rudder.

Rudder in a full keel boat

Looking back at the rudder design, the first sailboats had a full keel and the rudders were on the continuation of the keel, offering the best rudder protection. But besides the full keel being responsible for a lot of drag, they had an efficiency problem and had to be big: the rudder to work well has to be in the way of the water flow, and the further away from the keel the better they work. The rudder on a full keel is just immediately after the keel, and that does not allow them to be very efficient.

A Moody with a skeg rudder

The next step in the evolution of yacht design towards a more efficient and better sailboat was to separate the rudder from the keel, using a modified fin and bringing the rudder aft. Almost all the rudders of that era used a skeg, most of the time an integral one that protected all the length of the rudder. That improved the rudder efficiency over the previous solution but also revealed some problems regarding using skegs. 

But they found out the skeg could not be very strong. If it is very strong the skeg would not break with a very strong impact or grounding, but the force transmitted to the hull, multiplied by the long arm due to the depth of the rudder, would risk breaking the hull at the insertion point, what is far worse than a broken rudder.

Skeg rudder was destroyed by an Orca attack

Skegs become weaker, and, like the rudders, sacrificial, to preserve hull integrity in the event of a truly violent shock. The sad situation with Orca attacks on sailboats, mainly in Portuguese, Spanish, and Moroccan waters, showed that all types of rudders could be damaged and that the 4 sunk sailboats went down because the rudder breakage led to a loss of hull integrity, and that, to water ingress.

It is relevant the case of a Moody 66, one of the last Moody to be built, a strong boat with a skeg rudder that was attacked by orcas and that did not sink almost by miracle, due to the help of a powerful water pump delivered by helicopter. The skeg did not break and as a consequence, the hull broke. The damage was quite impressive, making for a costly repair.

Moody 66 skeg rudder and the breached hull

One more step brought boat design to modern spade rudders, designed for maximum efficiency, far away from the keel, designed with a sacrificial function: they should be strong enough to sustain all the abuse strong sea conditions could have on them, resist small shocks but towards big shocks, they should break or bend before the hull breaks, to protect hull integrity. Not an easy compromise designing a rudder that responds to these two opposed constraints.

More efficient keels, with a smaller foil (increasing the distance to the rudder) better-designed hulls, and lighter sailboats, gave cruising boats a better sailing performance while the development of solo racing boats, to be sailed mostly on the trade winds, showed that very light beamy boats, with the beam brought aft, had a performance advantage in regards to easiness, being more stable, and sailing with less heel, making them easier to plane downwind, even under autopilot, without losing too much performance upwind. Overall that easiness makes them, out of very weak winds, or upwind sailing, the faster boats.

Moddy 66

But they had a problem with rudders: being extremely beamy they would need a hugely deep rudder that would not be very efficient upwind with the boat heeled due to an extremely asymmetric water flow, meaning that, while heeled the wet surface would be a diagonal, the center of it passing far away from the single rudder.

This led to the use of twin rudders located aft, at the center of one of each asymmetrical narrow water plans (wet surface) that were formed when the boat sailed upwind heeled, to port or starboard. These rudders have the additional advantage of being much smaller, less deep, and therefore generating less effort than a single rudder, making them more resistant.

IMOCA racer. The only thing in common with contemporary very
 beamy main market boats, is being both extremely beamy, but
 these boats are very light and can compensate for a less good
performance upwind with an easier beam reaching and
downwind planning speed.

It took some decades for the big brands to opt for extremely beamy hulls, with beams brought aft, as the typical hull design to be used in main market cruising boats, mainly because they had to wait for the unusual shape to be accepted by the typical conservative cruiser, as a nice one. 

The first production cruiser to be designed this way, decades ahead, was the Levrier des Mers/Cigale by Finot/Conq. They had designed previously several of those solo racers (IMOCA) and were actively involved in their development and security. 

The Cigale/Levrier des Mers, in their first versions, appeared almost 30 years ago. The difference between the two denominations had only to do with the interior layout.

Cigale 15 with a two-rudder set-up, below,
Hanse 460 with a single rudder.

The 2004 Cigale, a 46ft boat with a 4.20m beam looks today moderately beamy, if compared with today's main market cruisers of about the same size, for instance, the new Hanse 460 (45.5ft), has a beam of 4.79m or the Dufour 470 (45.9ft) with 4.74m beam, and they are not the only ones, being that the contemporary design tendency for this type.

Below the Solaris 50. The new Solaris 50 is beamier than the previous 50
 and while the first one had a single rudder, the new model has a twin rudder.
The Solaris is a lot less beamy than the Hanse 460. The Solaris is much
 bigger (48.5ft to 45.5ft) and even so it has less beam (4.78 to 4.79m)

It should be said that the reasons for designing the Cigale this way had to do with providing an excellent sailing performance in the trade winds, maintaining good upwind performance, and allowing for a boat easy to sail at speed.

The Hanse design has to do with sailing with little heel, not needing much ballast (relying mostly on hull form stability) and most of all offering a huge interior volume. 

Both the sail performance and safety stability have nothing to do with the Cigale's and they are incomparably worse.

The 2003 Cigale displaced 10000 kg, the slightly smaller Hanse 12600Kg. Both have about the same draft (2.20/2,25m) but the Cigale has a 33%B/D and the Hanse only 26.7% and I am not sure if this is not only true for the version with a 1.75m keel (being the B/D smaller on the version with 2.10 keel).  The Cigale had also water ballast. 

Note that on the shallow draft version Hanse 460 (dashed) the
single rudder is less deep, offering less control with the boat
 heeled. Below, XP50, with a deeper rudder, offers more control.

They have in common a single rudder and the beam pulled aft. Only on the more recent versions of Cigale, the 16, by Marc Lombard (2017), and the 15, again by Finot/Conq (2024), that are beamier, do they have twin rudders.

The new version comes with a swing keel, with all ballast on the keel, and has a considerably bigger length than the Hanse 460 (45.5ft to 47.6), however, it has a less beamy hull (4.70 to 4.79m).

Deep rudders, some almost the depth of the keel, are more vulnerable, not only due to the bigger efforts that a deeper rudder generates, but are also more exposed to breakage due to groundings or eventual shocks with submerged objects. 

The better protection that the keel offers to a single rudder while sailing is no match for the greater reliability of having two rudders, instead of one. When a rudder breaks due to a shock with debris, if you have two, you still have steerage on the boat, and only upwind with some heel will you lose all steerage. 

Above, Bavaria C45, below, Oceanis 46.1.  The Oceanis twin rudders
 are much less deep than the Bavaria C45 single rudder.

We can also talk about the superior directional stability a twin rudder provides, making the work of an autopilot easier and that's one of the reasons why almost all offshore long-distance racers have twin rudders.

So, the single spade rudder is as dead as the skeg rudder? No, both types, the spade rudder and the twin-rudder have advantages and disadvantages, depending on the design criteria and type of hull, one can be a better solution than the other.

I continue to see designs of racing boats and of top performance cruiser racers, designed with CFD and VPP extensive use, that continue to use a deep very narrow spade rudder. Rating formulas can have to do with that. Still, I am more inclined to think that for absolute maximum performance, less drag, and maximum rudder sensibility, those rudders can offer advantages, especially if the racer is not very beamy.

But we are talking about boats designed to offer maximum performance, with somebody full-time at the steering wheel, and sailing on the limit, with a busy crew controlling the sails.

Solo racers: above, Imoca, below, class 40. All the boats on
 these classes have two rudders

Solo racers have for many years adopted twin rudders as the better solution for sailing with a short crew on very beamy boats, and that has probably not to do with absolute performance, but with the advantages in speed that a more easily controllable boat can offer, and at the superior speed an autopilot can be used while racing.

Regarding cruising, if the boat is not used also for racing (cruiser-racer), and if it does not have a moderate or small beam, the advantages of a single rudder over a twin rudder are less than the disadvantages, especially if the beam is huge, like in many contemporary main market cruisers.

The main advantage and the main reason why it is used in less expensive and very beamy cruising boats is to be cheaper to build, allowing to cut costs.  Also, it can offer a slightly better sensibility and mainly, it gives better maneuverability in the marina, but most of the owners that buy these boats have them with bow thrusters, and that makes this last advantage negligible. 

However, if you want a sportive boat and don't want a bow thruster, it can make a huge difference and a single rudder can make sense.

72ft class Cannonbal. Almost all Maxi 72 racers have a single rudder,
like almost all TP 52 racers.

Today marina "corridors" are narrow and the easiest, and sometimes the only way to put a 40ft boat (or bigger) on a berth without a bow thruster, or help from a marina dinghy, is to sail backward and turn sharply over the berth. 

A boat with a very deep spade rudder will be able to turn almost over its keel and with practice you can do this without trouble. With a twin setup, the turning angle is much bigger and it will be much more difficult or even impossible to do that. 

Grand Soleil 44, which won the ORC world championship on
the last 3 years, has, like all cruiser racers and racers built
by Grand Soleil, a single rudder, as well as all x-yachts and
all Arcona Yachts.

On a not hugely beamy cruiser-racer with a very deep rudder, you will not have less control at big angles of heel, you will enjoy the extra sensibility a single rudder can offer, will be able to put the boat where you want, and choose your way in between the waves, with a precision a  twin rudder set-up will not be able to offer. 

You will have more precise and nervous steering and you will have more fun at the wheel. But on autopilot you will miss the superior directional stability of a twin rudder, which will be able to steer the boat in conditions where, with a spade rudder, you will need to hand steer, needing to reef the boat sooner and go slower to use the autopilot.

Of course, these are generic considerations that are valid but do not take into consideration the way each boat is balanced and designed. The rudder does not work alone but in conjunction with a hull, and hull design has an influence on the rudder's effectiveness and feeling.