Whenever we lift our OVNI out at a boatyard, she soon attracts a lot of attention. Partly that’s due to the sight of a sizeable boat (seemingly) without a keel, sitting on her bottom, but especially the rudder in its kicked up position, pointing out behind her.
But equally as there are now many different yards building these aluminium centreboarders, so there are many variations on the type of control surfaces—lifting, spade rudders, twin rudders and/or a combination with daggerboards. The challenge for the designer is to come up with a robust, practical system that enables the boat to maximise the use of its shoal draft and beachability, whilst at the same time functioning effectively and safely offshore, and being maneuverable in today’s crowded harbours.
The rudder system on our boat has a lot going for it—it is robust and uses simple hydraulics to lift the lower section when in shallow water, but when down it is well immersed and provides good control. In the event of hitting a submerged object, a small core plug in the hydraulic pump will rupture, saving the rudder from major damage, which several owners we know can confirm. The propeller is well protected either when underway or when dried out with a solid skeg all around it. But, as we have found out, it is another thing that can give trouble, and requires additional maintenance. Alubat now seem to be going over to twin rudders, as on the 445, where, unusually, the rudders are aligned vertically.
Others such as Garcia used to use a spade rudder with a liftable single trim board ahead of the rudder on their older Philippe Harlé designs (Maracuja, Nouanni, Passoa), before going over to twin angled spade rudders on their more recent models. Owners I have spoken to like these boats a lot, and claim that the trim board is highly effective, on all points of sailing.
One of the more recent designs in this field is the Allures 44, where twin angled spade rudders are used in combination with a saildrive leg, sheltered behind a partial skeg. But equally, another very recent design, the Boreal 44 has opted for a single spade rudder with liftable twin daggerboards mounted ahead and outboard of the rudder, and uses a conventional shaft drive sheltered behind the keel box and partial skeg.
Pros And Cons
These designs tend to be quite beamy, to give them additional form stability, and many of the most recent designs have the beam drawn well aft, so the designer has to do some smart thinking to keep the rudder immersed when heeled hard over. Undoubtedly, this is where angled twin rudders offer a benefit and have thus gained in popularity. But several owners have commented that they don’t like the noise associated with the exposed windward blade slapping waves, although they are impressed with overall controllability. It has also been suggested that angled twin spades off the centreline are more exposed to damage from floating debris, or in the event of a hard grounding.
Centrally mounted spade rudders on the boats from Garcia (and others) seem to have a good record of reliability as far as I can ascertain, and the combination with daggerboard(s) seems to work well. With a substantial skeg extending below the propeller, there is also some shelter for the rudder, which has been much improved on the Boreal (where the rudder is well immersed) by the mass of the keel box.
These boats tend to lack much lateral resistance with their smallish keel areas, and with their relatively high freeboard, can be a handful in cross winds under power, especially if the centreboard is raised (don’t try that is my advice…). Twin rudders that are a long way from any prop wash tend to exacerbate this, and generally speaking, if you spend a lot of time around small, tight marinas a bowthruster might be a necessity to stop your hair from going prematurely grey! Otherwise, it’s a case of keeping more way on than you might like, fitting the best stopping prop that you can afford and spending some time practicing until you’re confident in your close quarters boat handling.
There is probably no perfect solution. All of the options have their good and bad points. Nowadays, much will also depend on whether you might be looking at a new or used boat, given that the available options have been changing over recent times. Ultimately, all of these systems have been shown to work effectively offshore—look at the track records of any of these designs and you’ll find they have been taken just about everywhere. The older, simpler systems are well proven though, and it will be really interesting to find out whether the newer approaches stand the test of time just as well. It would be good to hear from anyone out there with experience of any of these boats to help build a better picture. Please leave a comment.
Colin, Thank you for this great review of various solutions to the age old issues. As you aptly put it, “we will see whether these new systems stand the test of time.”
Which brings to mind another question. Would I be crazy to purchase an older Ovni and modify it to suit my needs or have the functional designs improved that much over the last 25 years?
Thank you for your comments.
Thanks for great comments. Our Hood Pilothouse 51 “PATIENCE” has a Hood “delta form” hull design (some call it a whale bottom) where there is no skeg keel and the deep centerboard extends from the bottom of the hull. The rudder kicks up like the OVNI, but is controlled from a single line in the lazarette— since the rudder has slight negative buoyancy, when the line is released it thumps into the down position. This allows a less than 5 ‘ draft on a 52 foot 50000 pound vessel. We agree that motoring in confined spaces isn’t a good idea with the board up!
Tried to attach a small picture but wasn’t able to navigate the technology to do so!
Pete & Kareen Worrell
Hi Pete and Kareen,
Sorry you were not able to add a photo. Not your failure, that capability is specifically blocked, otherwise the spammers would be posting pictures that would make us all blush!
We do have a plan to add a Flicka group to this site so we can all share photos. Will deal with that as soon as I recover from the effort of getting this new site up and running.
As far as I can see, you have a 3 blade fixed propeller. Is there any special reason why you don’t use a feathering propeller like for example the MaxProp?
Colin, one option you seem to have overlooked is the cassette rudder…why is that so? Regards DV
Victor, there’s no doubt that a well cared for and well sorted out older boat has many advantages, especially as there is no guarantee with a new boat that all will be easy. You often get all the extra gear you’d be buying anyway, and someone else has funded (and endured) the ‘finishing’. And many of these boats are still largely evolution, not revolution, so a good old one may well be a good option. The only drawback is that if you have your heart set on a particular interior (for example) you may struggle if it is not the standard option.
Pete, it would be great to hear more about your boat – my current neighbour here in Portugal has a Wauquiez Hood 38 and was eulogising about her last night – a really strong, powerful seaboat.
Henrik, there was indeed a reason for the fixed prop, and we now have a new feathering prop, as of two days ago. Until we’ve got some experience with it I don’t want to say too much, but will be posting about it just as soon as we do. Suffice to say that this is prop No. 3!
And David, I’m not entirely sure what you mean by a cassette rudder – perhaps a board that slides up and down in an outer casing? That was a system much in use on smaller boats over here, and was simple and effective, as far as I could see. If there is a particular design or an experience of such a system you have in mind it would be good to hear your thoughts. Basically what I set out to do was to show what the options have been on the French alloy centreboarders in recent years, and if I’ve missed something then it would be good to put that right.
I enjoy reading through these extensive discussions. Even if they are several years old, they maintain their relevance.
I believe the “cassette” rudder that David Venning is referring to is found on only a very few vessels. “Glory of the Sea” is perhaps one which has twin rudders in rotating cassettes, connected by a rod to the steering quadrant. You can see how it works – more or less – at http://www.dailymotion.com/video/x9nhky_glory-of-the-sea-le-voilier-des-gla_sport . It has the advantage of keeping the sensitive mechanisms encased in the cassettes which are buried in slots in the hullform, thereby reducing exposure to air/salt.
As usual your original post is well reasoned and thorough. I own a 10 year old Garcia 46 with twin rudders and you summed up the pros and cons of this design well. Your points about close quarters maneuvering can not be over stated. The relatively flat forefoot on our boat precludes a fixed tube for a bow thruster so we have a retractable one. I was looking at your hydraulic rudder photo and feeling well satisfied with my fixed twin rudders. I hate too many moving parts. Then I considered the complexity of my bow thruster set up… Oh well trade offs with most everything.
As always your analysis is well thought and balanced, evaluating all (or almost all) aspects of the subject. Except for all the aspects you have treated, one additional aspect is important to us: the shape you can gave to your rudder and your appendages… And I’m afraid that for a long long time quite a lot of boatbuilders have only used flat plates as rudders…
We like the idea of daggerboards in front of the rudder and have tested them. According to us, it is (was the beginning of) a good solution but because of the distances between daggerboard and rudder, your rudder gets a lot of turbulence. When you want to enhance stability it is ok, but having sensations when you steer or reducing the consumption it is another problem.
Everything is trading off & compromising and I think we already discussed why we are in favour of single rudder systems.
Very best regards,
Chris, thanks for your comments, which bear out my own impression with twin rudders, and largely mirror our own single rudder experience. It sounds like the same point regarding retractable bow thrusters applies across the range of these boats – OVNI fit them, and I saw one being installed in a Boreal in build. Obviously they offer less drag than a tunnel thruster, which would be a major plus for me, but like you I tend to avoid complexity (where possible!) and would hope that they are reliable, especially in terms of raising and lowering. And as we’ve just had the whole rudder apart due to an internal fault, yes, there’s a lot to be said for simplicity!
Jean- Francois, I fully agree that there are still benefits to be gained from the point of view of using modern shapes for all appendages and foils. I know that you at Boreal have put much thought into this, and judging by the sailing performance as I experienced it they seem to work. Interesting point about turbulence with daggerboards ahead of the rudder, which I hadn’t considered. Obviously an area where twin rudders or your own twin boards and single rudder would be better.
But, as you say, all boats are a compromise, and all of the solutions employed so far have their good and bad sides. Robustness and reliability are my watchwords, and as long as improved performance comes with those two fundamentals, then I’m all for that.
What about a transom-hung kick up or daggerboard rudder? Sure, they may be a bit less efficient than one under the hull, but I think that can be more than compensated for with good design, possibly including running it through the stern scoop. I’ve had both types of transom hung rudders on a 32-foot cruising cat and they worked well. Having everything out in the open on the transom makes it much easier to repair when it is needed, and you can have it right in the prop blast..
Regarding the Ovni 435 rudder “rupture disk” safety mechanism. I admit to smacking into coral heads in tropical waters, a rock or two in New Zealand (and most recently in Labrador-well within a marked channel incidentally), sand bars off the east coast of Australia, and even a submerged pile in the ICW. Thanks to the Ovni’s retractable centerboard and rudder, the worst thing that happened was the need to replace one of the brass wafer “rupture disks” in the hydraulic pump/valve assembly.
Given the frequency of my poor navigation (or our tendancy to take chances because we know we can), I now never lock the centerboard down since its weight is sufficient to hold it down while underway. This means that if the centerboard collides with an immovable object, it simply rides up and I do not sacrifice a rupture disk. On the other hand, the rudder must be pumped down and locked into place. Since the centerboard is the first thing to hit, I usually have had just enough time to release the rudder and as it pivots up, save the sacrifice of the rupture disk in its valve.
However, in May of this year, coming up the ICW south of Wrightsville Beach, NC, we once again ran aground in shallow water. I had felt the centerboard hit and released the rudder. As we moved back into deeper water, I tried to pump the rudder back down and it would not move more than a few inches. Inspection showed that the hydraulic ram had been bent. There could only be one cause of this and I checked the rupture disk (brass wafer) in its valve assembly. It had obviously not ruptured. Closer inspection showed that two rupture disks had corroded together while in the plastic zip lock bag provided by Alubat when the boat was launched and had appeared to be a single disk when last replaced. Two of these rupture disks could not be ruptured and the ram bent. And this was at a speed of no more than two or three knots.
I had been corresponding with Jimmy Cornell and told him about this event. He indicated that Alubat now supplies the rupture disks in individual zip lock bags, perhaps for this reason. A replacement ram from the factory would have taken about a month to obtain so I was very fortunate to find a farm equipment hydraulics repair facility a mere hundred miles drive away that was capable of replacing the ram and three days (and an unscheduled haulout) later, we were underway. Bottom line. Check to make sure you never put two rupture disks in or carry a back up ram.
All the best,
Fripp Island, SC
Kettlewell, the transom hung rudder idea has its merits, not least (as you point out) that everything is easily serviced. However, I’d want to know that the reinforcement of the transom, and the strength of the rudder and its fitments was up to the job, as the loadings on a boat of this size are massive. The only experience I have of such a system was on the very first Southerly 135 (many, many years ago), and it suffered from stress very badly and was extensively crazed.
Jim, that’s really timely. We have never ruptured a disk yet, but that’s more by luck than judgement, I can assure you. It’s an ingenious system, that offers a real fail safe in the event of a collision with a floating or shallow object, and friends of our who took their 395 into the Amazon got through quite a few. Our disks are in a single ziplock bag like yours, and it has never occurred to me to check that they haven’t stuck together – but I will now! And aren’t farm and fishing boat mechanics great people when the going gets tough? Nothing fazes them, and hydraulics are their daily bread.
Great comments from you all, so many thanks, and do keep them coming.
I think transom reinforcement/strength is the least of your problems. Much easier to make that area strong than it is to put a tube through the hull, add bearings, hydraulic rams, etc. keep it all watertight, functioning, etc. I’ve got an Autohelm self-steering gear that functions as an auxiliary rudder and it doesn’t require any particular transom reinforcement, and is showing absolutely no signs of strain after about four years of use. It’s a lot lighter than an underwater rudder, shaft, tube, etc. too.
I note that several Open 60’s have retractable/kick up transom hung rudders. The loads on these rudders is many times higher than the loads encountered by 40-50′ cruising boats because of the speed and power of these machines. And the design and structural issues of this type of rudder are easier to solve than any other system. The Open 60’s choose them for ease of repair and for the ability to retract the windward rudder rather than letting it drag along the surface. The rudder ventilation problem on the active rudder seems acceptable, especially if the rudder has a ventilation fence.
My only personal experience with twin rudder designs was on a 44′ Tom Wilie ULDB in the Bahamas. Worst helm feel I’ve ever encountered, but I assume this is not characteristic. Still I suspect that most twin rudder designs on cruising boats are there for the same reason women wear spike heel shoes.
A number of years ago I had Bernard and Monique Souchard over to my boat for dinner. They had been to the high Arctic, around Cape Horn, and wintered in Alaska aboard their Garcia Passoa 45. As I recall their downwind technique involved raising the keel (which was a large elliptical shape with as much area as a conventional ballasted keel) and lowering the daggerboard ahead of the rudder. They had only a small tiller pilot, and claimed the boat would steer itself because of the resistance moved aft and react to a rogue wave by sliding down the face rather than broaching. When beating the daggerboard was raised to avoid stalling the rudder.
Looks like there are starting to be enough different design ideas in use to let the ocean teach us what works best.
Kettlewell, thanks for making such a fair case – and Jim for backing it up. My point wasn’t that such a system was inherently less suitable than the others I originally outlined, simply that in the one case I saw it employed the required strength had not been achieved. I’ve no doubt that in the case of a good naval architect and a dependable builder it can be easily achieved, and indeed has its own merits, not least its simplicity.
Jim, I’ve only very basic experience of twin rudders and that was on a small boat, so I’m not the best person to comment on their abilities. However, I know that the builders who are going down that route believe that there is merit in having the leeward rudder well immersed when heeled, rather like the Open 60’s. And as the trend towards new designs with more beam aft continues to gather pace, you can see why. Not that it is obligatory – Boreal have managed to do a good job without them.
Good to hear about another positive first hand experience – the Passoas are great boats and have an enviable track record in all latitudes. And the downwind ability with the board raised is remarkable, as it is with our OVNI – the pilot is hardly working at all. And I totally agree with your final comment – my view entirely.
You speak about Open 60’s and their capacity to raise their windward rudder. The main reason for that is to reduce the probability of hitting unidentified floating objects… In the past some participants to the Vendée Globe had to abandon the race because their windward rudder hit something… And as you point out without being liftable it was impossible to service them… (nowadays the problem remains with swinging keels)
I have an Ovni 36 and sail her in the Chesapeake. I have a problem with the hydraulic pump for the rudder. Basically there is no more pressure when I action the pump. I have dismantled the whole thing, services the main rod, confirmed that there is no leak and pretty much isolated the problem to the hand pump itself. If I can have the pump repaired locally, would you recommend getting a new one from Hydroem in France, or going for a US made hydraulic pump, like Harkem , for example.
A few thoughts –
Did the pump fail slowly or just fail? If the former it may just need new seals.
In my (limited) dealings with Hydroem, I found them to be very efficient and helpful, so they should be able to help you with either replacement seals or a pump.
I’d be a little cautious about changing to a US made pump, as (a) the Hydroem pump works with glycol mix (so any replacement would also need to) and although I don’t think it would be a major issue, the pump you have is all metric fittings.
Myself, I’d go for a replacement pump from Hydroem, simply as it should be a straight swop.
Thanks for the advice, I just sent an enquiry to Hydroem. I will investigate the seal issue, before ordering any replacement pump. when I got my ovni (1 season ago) the fluid inside the hydroem pump was navtec. Unless you advise against navtec fluid, I will stick to it in order not to mix different fluids in the lines.
Obviously as yours is an older boat, things may be different, but on all the more recent Ovni’s the Hydroem pump uses an ethylene glycol/water fluid.
It may be that the Navtec fluid is appropriate for your boat – Hydroem will tell you. Michel Farre is their technical Director and is very helpful.
But until you hear, I wouldn’t mix the fluids!
Good luck with it and do tell us how you get on.
Hi Colin and all,
Additional thoughts re. rudder options for center boarders or lifting keel boats : http://en.ovniclub.com/sailboats.php
Interesting article about modern rudder option. It might be useful to know that the “inventor” or more simply said “the first real use of a 2 rudders boat” was Gilbert Caroff with Spanielek in 1977 (a boat designed for the 6.50m transat) and since then all racing boat have twin rudders. But Gilbert Caroff who is also credited for having the number of sailboats having spent the most time in remote exploration and icy waters advocate AGAINST angled rudder for pleasure craft. The reasons:
-Can’t use in ice
-Impossible to control at low speed (no water push on rudder)
-Very little performance advantage (non perceptible) for a pleasure (not racing) boat
-They can and they will hit many things in the water
He recommend instead that the 2 rudders be placed vertically at about 1 meter behind the propeller and maximum 1 meter between the two. This is what i’ve done while building my Chatam 43. (i don’t know how to insert pictures in this post though…)