The Offshore Voyaging Reference Site

Twin Rudders Have No Place In The High Latitudes or Maybe Cruising

We just got an interesting question from Françoise and Jean-Michel who are looking at buying a new boat.


Boreal’s daggerboards can be broken as you can see on the n° 42 ep ” Bushpoint ” on You tube. It was last year on a Boreal 55 in the north of Norway. Even if it was not a great issue , it can happen. The owner fix it himself.

My wife and I are looking to build a new boat to change our Ovni 43 and we ask Patrick Lenormand, the yard manager of NYS ( Caen France) to build it .

We have chosen a Cordova 45 ( design of Jean-François André , well known french architect ) . His choice of a twin rudder system concern me .

He said that he put two strong skegs welded on the hull to prevent any damage. My worry is also about the drag of these skegs in front of the rudders.
I know that a boat is always a trade-off but I don’t want to make a mistake.


You are right to worry about the twin rudders and that’s a great question because it exposes something we are often told: that we can fix a basic design problem by just making it stronger.

I used to believe this, too, until the engineers that comment here helped me understand it better.

Sure the boards on the Boréals can break. Boréal themselves talk about this.

But that’s a a good thing, not a bad thing. It’s a feature, not a bug.

A key thing to understand about boat engineering is that saying we will just make it stronger, is actually bad engineering.

There is no way to build a skeg strong enough to withstand even a six-knot impact from ice, a rock, or a big log (big problem in many places). The key point is that something must flex and bend to absorb force.

So if we make the skeg super strong and it does not flex, then maybe it rips right out of the hull and the boat sinks. The force must go somewhere.

So based on that, here are the key points that I think about:

  • When a Boréal board gets damaged, it breaks and the hull is fine. With skeg-hung twin rudders, a bad collision with a rock or ice can hole the boat and the stronger we make the skeg the worse that problem gets.
  • A Boréal can operate fine with no boards (I have sailed one that way). You could even sail all the way home with no boards. Bend a twin rudder and skeg and the steering is jammed until we can haul the boat and then we need skilled metal workers to fix it.
  • When in tricky waters (rocks or ice) on a Boréal, we can pull up the boards and the rudder is protected by the huge keel box. We can never pull up twin rudders, they are always down there ready to get damaged.

For me, based on some 30 years of cruising, particularly in the north, I would never do so in a twin-rudder boat. Heck, I would not own a twin-rudder boat for cruising, but that’s me.

And by the way, the reason Boréals will never have twin rudders is because the chief designer, Jean-Francois Delvoye, went to Chile in a twin-rudder boat and broke a rudder on a rock.

After that he sold the twin-rudder boat, and designed and built a boat with a single rudder and keel box for himself. That was the first Boréal.

A good example that will help to explain this point about the force being absorbed by bending is the A40 keel.

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Jean-Michel Roulland

Hi John
Thanks a lot for your answer!
We will ask Jean-François André if he can change his design . I know that he as already made such a boat without twin rudders for this size . I even wonder if he was the inventor of the daggerboards : in 1979, he designed the Damien IV for Gérard Janichon with one rudder and a twin daggerboards. So, it is probably still possible.
A few years ago, we have had a bad experience In Glengariff ( South West Eire ) as we have hit a rock with the rudder (Ovni 43) and broke the hydraulic pomp( not the fuse) . I dived to put a rope between the propeller protection and the rudder to make it useable . We have crossed the Manche Chanel like that. A little nerve-wracking!
So you understand why rudder technic is so important for us!
Best regards!
Françoise et Jean-Michel.

Drew Frye

This is interesting.

I once bent and jammed a rudder in my PDQ cat. I was ripping along at 10 knots through brown post spring flood waters on the Chesapeake Bay and hit a submerged log. The keel pushed the log down, after which it popped up in front of the rudder. No hull damamge; the shaft bend just a small fraction of an inch until it hit the hull and jammed.

Two things. First, having a keel in front of the rudder is not for certain. Second, having two rudders, completely the cruise was simple, even though I was alone. I steadied the boat by reducing sail and lowering a low-drag drogue. I then cleaned out the aft locker, crawled in with two wrenches, and disconnected the dysfunctional rudder. I finished the cruise with one rudder. If the rudder had holed the hull, the shaft and aft portion of the hull is bulkheaded nearly to deck level.

But yes, in ice country I would want something in front of the rudder and bulkheads fore and aft. I’ve sailed in thin ice with spotty 10-inch flows and didn’t like it. That’s scary stuff.

Drew Frye

I agreed completely. I would think those exposed rudders would get whacked frequently. Good fun on a lake scow, not so much on a cruising boat. I was just sharing an experience.

Planing designs on a cruising boat make no sense for the same reason that cruising catamarans are not appreciably faster than monos; both only go fast if you are pushing harder than you probably safely can over long periods.

P D Squire

It’s not immediately obvious from the drawing but this alloy centreboarder has twin rudders. It also has twin motors driving props through mini keels in front of each rudder.
Enough protection do you think?×766.jpg

P D Squire

I agree about the complication. Also suspect the motor keels might add drag. You’re right, it is a dagger board and I share your concern about damage potential. Also, the board looks like a very high profile section for a cruising boat, optimised for higher than cruising speeds I’d have thought, and taking a while to start gripping after each tack perhaps.

Neil McCubbin

I agree that twiin rudders are vulnerable. Racers take the chance, in the interest of hydrodynamic performance. Cruisers are better off with a larger margin of safety,

Philippe Harle, who designed virtually the Garcia boats, and MANY others, until he died in the early 1990’s, told me that he preferred the spade rudder (no skeg) on our Passoa and the other works voyaging boats because if it is hit, the worst is a bent or broken rudder, with no leak in the hull.
The structure of our hull at the rudder supporting tube that Harle designed is massively strong, and I am pretty sure would resist the force necessary to break off our 100mm diameter rudder stock, without causing a leak..

The design of the single rudder Garcias, and Boreals, puts the rudder square behind the very solid fin, which must surely reduce chance of rudder colision.
On the Passoas and similar Garcia boats, the rudder is slightly shallower than the fin, and the fin underhangs the prop. So far, in 40,000+ miles, we have never hit the rudder or caught a line in the prop

Philip Aston

I have a Boréal 47. Here’s another bonus for the dagger boards… A while back a fellow owner suffered an Orca attack off Portugal. The boards were stoved right in, both at about 45°. But the rudder and steering was fine. He reckoned Orcas are not accurate at hitting a target and the boards acted as good sacrificial protection.

A year later, I was entering the Med as he was leaving, so I asked whether he’d leave the boards down again. “Not sure” he answered, since the boards did need replacing and the rudder is very well built. We did see a pair off Cap St Vincent, I kept the boards up (but the Watt&Sea came out of the water very quickly!). Fortunately they swam by, a couple of boat lengths off.

As John says, losing the boards does not affect a Boréal’s seaworthiness. They are most useful off the wind in a seaway, making the helm lighter for the autopilot. Similarly, the centreboard is only really important when hard on the wind, although I’m learning how to use it to tune the centre of lateral resistance, and hence the helm balance.

Philippe Dreyfuss

We are in the “decision time” between Garcia and Boreal. We visited Garcia yesterday and they explained that their twin rudder have a foam part at the top that would be sacrificial in order not to break the hull if anything big happened and then you could still sail away by disconnecting the dysfunctional rudder. What do you think of this solution?