The Offshore Voyaging Reference Site

The "S" Word—Stability

From the first time I saw one, I thought that one day I’d like to own an OVNI for long distance cruising. Living and working for part of each year in France meant that I encountered OVNIs and their sisters from Garcia and other builders regularly, and saw them return battered but proud from distant shores again and again. Listening to their skippers only made me more envious—all of them had nothing but the highest regard for the seakeeping abilities of these quirky craft. One day, I thought, one day…

So when the time came to put our money where our mouth is, there was no hesitation. And I can honestly say that the vexed question of the supposedly limited stability of the OVNI was never an issue for us. I simply thought of Jimmy Cornell taking his OVNI 43 Aventura III to the Antarctic and Alaska, and then crewing aboard Igloo, an OVNI 39, to Spitsbergen. I also thought of many other well known high latitude boats, Pelagic, Seal, Parati (to name a few), all lifting keelers that have made equally illustrious voyages. Now, we’ve a long way to go before we dare to include ourselves in the company of these immensely capable boats and their crews, but you have to aspire to something. Nonetheless, I thought it would be interesting to check the numbers.

The OVNI 435 has an EU category A (Ocean) rating, and that’s good enough for most people over here. Being no naval architect, the complexity of the formulae needed to come up with comprehensible figures made my head spin, so when I heard about the excellent Sailing USA web pages, for example, where simple data entry can be calculated to give a wide variety of figures that might be pertinent to ocean cruisers, it seemed a good place to start. So using the manufacturer’s data from our owner’s handbook, the website allowed some basic calculations to be effected.

The OVNI 435 has a ballast ratio of 135%—about average for today’s cruising yachts, and has high form stability, as we found when we sailed her home recently. The stability value is 34.15, and the Angle of Vanishing Stability (AVS) is 126.57, within the boundaries deemed acceptable for ocean crossing. The capsize screening value is 1.84, anything less than 2 being considered good. So looking solely at the stability numbers there is little to be overly critical about.

In terms of performance and comfort, the OVNI shows up well. The displacement to length ratio is 258, firmly in the moderate category, whilst the sail area to displacement ratio (with the standard genoa) should provide more than enough power for fast passage making at 22.42—ours will be lower, though, as we are having a yankee rather than a genoa as our working headsail, giving us a rating of somewhere just under 20—more cruiser territory. And finally, she has a motion to comfort ratio of 31.17, which when combined with the soft ride associated with internal ballast should make her a comfortable boat to make long passages aboard. All in all, a steady, middle of the road design built for long distance cruising.

Of course, these are “dry” figures, so we’ll be making sure that we don’t overload our boat. She has been kept deliberately simple, and even with only two of us aboard for most of the time, we’ll still be watching the weight. We’ve also kept weight down aloft—radar on the stern arch, hanked on staysail and so forth to keep the stability levels up, and in keeping with all our previous boats, we’ll be stowing everything possible below decks on passage. Keep it low, keep it light and keep the decks clear is a good way to go, we believe.

Another factor we’ll be looking to exploit is the ability to lift the centreboard when going downwind, not just to gain extra speed (although that’s good, too) but to avoid “tripping” on the keel and broaching. Many experienced OVNI sailors report lifting the keel in bad weather, allowing the boat to slide when hit by bigger waves, rather like a multihull. Well, if and when we have to face that, we’ll find out how well it works!

But at the end of the day, these are all just figures, and as it’s not unknown for well respected ocean cruisers to get into serious trouble if caught in the wrong place at the wrong time, we’re not kidding ourselves that we’ll be any less likely to suffer if it’s our turn one day. And so we’ll be out as soon as possible learning how our new boat likes to heave-to, run or work her way upwind in strong winds, and what survival tactics or equipment will be most suitable for our boat, so that we’ve at least a good working idea of where to start when the going gets really tough. There’s nothing like empirical experience, as the sea soon deals with the complacent, and at the end of the day it’s down to the way the crew handle the boat in so many cases, and staying away from the most dangerous places and conditions if at all possible.

The Sailing USA website makes this abundantly clear, quoting the 1998 Sydney/Hobart race review report that gave the following as one of the significant findings:

There is no evidence that any particular style or design of boat fared better or worse in the conditions. The age of yacht, age of design, construction method, construction material, high or low stability, heavy or light displacement, or rig type were not determining factors. Whether or not a yacht was hit by an extreme wave was a matter of chance.

The numbers for the OVNI are reassuring, and may be one of the reasons why so many experienced sailors over here choose them for ocean crossings, which is good, but it is surely only a small part of the picture. We always felt we had chosen wisely long before we looked at the numbers though, and felt that as others had gone before us and come back to tell the tale, then with time, experience and humility in the face of the sea, maybe we shall make it too. So now it’s down to us, a good strong boat and yes, that indefinable entity—luck.

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Hi Colin,
Now that you have crossed an ocean in your Ovni what did you find as far as stability goes and handling in a seaway?

On a broad reach and maybe a little too much sail up in a gust how did the Ovni behave with the centerboard up? Was there any tendency to round up or just drive forward while surfing down a wave?
Steve and Tracy

Colin Speedie

Hi Steve & Tracy

Sorry to have missed this before – better late than never!

Pelerin handled everything the sea threw her way very well indeed.

We were never even near the limit of control, and in the only prolonged spell of strong winds we had (off Cap Blanc for 48 hours) we hand steered for two hours in squalls, otherwise it was business as usual, downwind with the board up and the Windpilot steering – easy going, indeed.

The question with the board seldom arises – we only start to raise the board when the wind is behind the beam, and when going downwind or broad reaching the plate is either almost up or fully up. With so little lateral resistance, boat just tends to slide back on course rather than trip over the board in a big gust.

It’s worth remembering that the mast is well forward on these boats, which helps downwind, too. They’re really easy to handle downwind. Wait until you try this with RC Louise, as I think that the Boreal 44 with the daggerboards will be even better!

Best wishes


Victor Raymond

Hello Colin
John created a link to this previous post which I am sorry not to have read until now. It certainly is comforting to read your analysis. I suppose flat bottom boats have a certain amount of initial instability but higher secondary stability once the chine is in the water.
In my year and a half on Rajah Laut I can not say that I have experienced enough to know how the boat will handle all sea states however the non stop run from Aruba to Panama taught me that the boat can handle much more than my stomach can. We covered the roughly 600 miles in 3.5 days with only the genoa partially furled. In hindsight I should used either the Yankee or staysail but my Yankee furler was inop at the time although the stay was in place. This particular section of the Caribbean is known to be rough with nothing to stop the wave train and reflection coming as faraway as west Africa. In addition we had winds and gusts upwards of 30 kts. To say the boat handled it well was an understatement. I am sure your Ovni would have done the same but it certainly was a pleasant surprise to find out that the boat felt more comfortable in those conditions than we did.
Thank you again for this great post and thanks to John for pointing it out today.

Colin Speedie

Hi Victor

These boats do have a lot of form stability, and there’s very little point in overpowering them to over 20 degrees of heel – far better to let the boat settle on to the chine and power along.

On our recent transatlantic we close reached for nearly all of the last section from 3 degrees North to 9 degrees south in around 15-20 knots true wind. We simply reefed the yankee a little, carried the staysail and one reef in the main, and she rattled along very well indeed, in great comfort, too – cooking was easy.

With all internal ballast she (like all of these boats) has a very soft motion, which is exactly what you want on a cruising boat.

I wouldn’t want to spend days on end beating in one of these boats (well, any boat, in fact!) but on all other points of sail they really do well.

This despite the fact that Pelerin is a loaded up cruising home, so the numbers will look different these days. I’m sure that Rajah Laut will continue to impress, and look after you well.

Best wishes


Gaute Resheim

Hi Colin
just bought a 435 that i use as a liveaboard in north off Norway Bodø
i am planing a long trip and want more diesel i have standar tank 300 liter
but thinking about building a spare tank in the stern rom where i now have liferaft. 150 liter ekstra and that wil give me more weight in the stern. any idea about this ?


Colin Speedie

Hi Gaute

Before you do away with the liferaft locker I’d consider the following ideas:
1. If you do convert it to a tank it will need to be very well sealed
2. You should add no more weight in that locker than you would the weight of a 6 man liferaft and ancillaries, especially if you have a wind vane steering gear on the transom (as we do).
3. We carry around 11ol of extra fuel for long passage (oceans really) and have never arrived with less than at least half full tanks. Most of the time we carry only 10l spare fuel in 1 jerrycan.
4. We decant the fuel from the cans as we use the fuel from the tanks – that way the extra fuel is lower and closer to the centre of gravity, that keeps the tanks almost full.
5. For my money I’d keep the liferaft locker, and use strong jerry cans of no more than 20l capacity each with good strong screw caps. Ours live in the cockpit lockers and we can strap them down.
6. I like that locker for emergency equipment.
And good luck with the 435 – they are terrific boats, and great for long distances.

Kind regards


Chuck B

Hi Colin, do you have a link for that calculator you used? I found this one ( but it does not have ballast ratio or angle of vanishing stability.


Hi Colin,

I am a member since a couple of days and I have already read a lot of your articles.
I have sold my 9,30 m steel yacht and I am currently looking for another boat which suits my plans of long-distance cruising together with my wife in a couple of years, when I am retired. So I will be 60+ then.

The boat I am interested in is an Ovni 35. Before I had looked for a Hallberg Rassy 35 Rasmus, but I couldn’t find one in good quality.

I like the Ovni but I am a bit concerned about the stability and about the swinging-up rudder which is operated by hydraulic. I am also not sure which is the best heavy weather tactic on the Ovni (I have read John’s articles about this subject).
It would be kind if you could tell me your points of view in these cases.

1st Stability
I saw the stability figures you wrote for your Ovni 435 and tried to compare them to the Ovni 35, but I didn’t find a calculator that showed exactly the same results that you have written. Which calculator did you use? Is it for free use in the internet?

There is only one thing I could compare for myself. It’s the percentage ballast to displacement which is 35% (10.300 displacement/ 3.600 ballast) on the Ovni 435 and 40% (5.400 displacement/ 2.200 ballast) on the Ovni 35. But the 435 is much beamier 4,22 compared to 3,60 on the Ovni 35 and has a minimum draft which is deeper (0,74 compared to 0,55m).

Would you also say that the Ovni 35 is stable enough for ocean-sailing even in heavy weather?
And if the Ovni capsizes will she stand up again in a reasonalble time? (having read the article about the loss of TAO – I think she remained too long upside down).

2nd swinging-up rudder
As far as I know, the Ovni 35 has the same system as on the 435. The upper part is protected behind the skeg. The lower part has no skeg to protect but when you strike an obstacle it swings up by breaking a small thin plate in the hydraulic-system to protect the hydraulic-hoses from bursting.
To me in that system there is more protection than on a half-skeg-fixed rudder modern grp yachts have if they have any skeg at all.

But… and these are my concerns about that:
The time, the rudder is in the upper position it is very hard to steer. As I was told it takes a couple of minutes to replace the plate. And in a storm a couple of minutes can be long.
And if there is a failure in the hydraulic-system which might happen because of chafe of the hoses or because the seal in the hydraulic-cylinder is damaged you don’t have the chance to put the rudder down again.

I was told that some Ovni sailors fix the rudder (by a bolt f.ex.) when ocean-sailing. But I think than you get the risk of a real damage if the rudder strikes something during the voyage.

What do you think about these concerns, Colin? Are they theoretical?

How often do you maintain the hydraulic rudder-system and what do you do to maintain?
Do you also clean the hydraulic-rod from time to time?

3rd heavy-weather tactics
Which tactic would you recommend for the Ovni?
Heaving-to – will she do that?
Using JSD?
Or just running off, downwind?
I have heard that an Ovni won’t capsize / or is less vulnerable to capsize than a keel-boat while the centerboard is retracted, as an Ovni will slide down the waves and not struggle over her keel as there is none with the centerboard up. – Does that really work? Won’t she capsize while sliding down the waves?

And what about steering in these conditions? Will a windvane work?

Will the Ovni be as save as a HR 35 Rasmus for example?

Well, Colin, a lot of questions. I would be glad to hear from you.

Thank you very much and best regards

John Harries

Hi Rolf,

Although I’m here in the comments pretty much 365 days a year, our writers only monitor comments for a week or so after article publication. A fair compromise since they have other jobs and obligations outside of AAC and they are paid on a per/article bases. So you are stuck with me.

There are rather more questions in your comment than I can answer here, but what I can say is that the Ovni 35 is a well proven ocean sailing boat so I think that as long as the one you buy is well maintained you should be fine in her. In fact I have a friend who has sailed a 365 all over the world, including some serious high latitude sailing. (We met them in Greenland.

As to storm tactics, yes the skidding ability really does work to keep these boats safe. (Our friends at Boreal did a big study on this, including Ovnis, before finalizing their design.)

All that said, a key thing to remember is that no boat will be totally safe from capsize and that it’s much more important to concentrate on tactics to stay upright than worry too much about stability numbers. To this end my recommendation is always: when in doubt, use a series drogue.

If you want to really delve into your boat buying options and tradeoffs, Colin does provide a consulting service:


Hi John,

thank you very much for your reply.

Yes, I have/had a lot of questions. Your reply gives me confidance in buing an Ovni 35. If I need more specific information to the Ovni, I will contact Colin.

Thank you and best regards

Ian Feathers

Hi Ian,

sorry for my late reply. No, I didnt get any further answer. But as I am now owner of a Hallberg Rassy 35 Rasmus it doesn’t do any matter to me. But when I decided to buy the Hallberg Rassy instead of the Ovni 35 it was not because of the stability. The final reason was that I think the Rasmus is a more comfortable boat, not because of space, but because of the deep sheltered cockpit and the S-shape hull. As we are no youngsters anymore that was importent for us. And, also importent to us – she’s a very proven bluewater cruiser for her size.

Best regards

Blair White

Hi Colin,
You’ve really peaked my interest in the Ovni 435 however I’m not able to located the Sailing USA site where you’ve come up with the various calculated ratios. In looking at the sailboatdata site I’m coming up with the following, calculated from sailboat data; your reported numbers.
Capsize Ratio: 1.96; 1.84
SA: 732;
SA/D: 14.6; somewhere under 20 with working headsail
Motion Comfort: 28.43; 31.17
Since I’m planning for the Southern Ocean, Motion Comfort and Capsize ratios seem to be numbers I should not take lightly. In one article I read they said to use caution when getting capsize ratios over 1.83 and motion comforts less than 30.6. The Alubat site no longer lists stats on the 435, so any guidance you can provide as to actual ratios for the 435 would be greatly appreciated

John Harries

Hi Blair,

It’s unlikely that Colin will reply, see (#3)

I don’t have any personal experience with the Ovni 435 but I would not worry too much about motion comfort or stability. In fact the Ovnis are known for being very comfortable offshore due to not having a large lump of ballast hanging off a deep keel.

Also the standard capsize ratio calculations don’t really work well with these centreboard boats since they tend to slide sideways when hit by a wave, rather than trip over the keel (as long as the board is up).

All that aside, I guess the biggest point is that the Ovnis have built up a great offshore record over the years.

Don’t get me wrong, I’m not trying to sell you an Ovni, but if that’s the boat you want, I would not let those two numbers put you off.

Arne Mogstad

Hi. This is an old thread, and maybe the questions in the comment are a bit dated, but I have an OVNI 385, which is a little smaller than the 435. After using it a lot for a year, including living aboard and sailing last winter in Northern Norway in some serious weather, I thought I could maybe answer some of it in case it would be of anyones interest, so here goes.

First off, the stability thing:
I am nowhere near competent to comment on any numbers, but the boat sure feels stable and safe in heavy seas and winds. I’ve had her offshore in full storm conditions with waves to match multiple times, and I have never felt that the boat was unsafe. Actually she is quite forgiving even if you are caught with too much canvas up, as I have done that repeatedly (I am new to sailing and have had my fair share of “learning-experiences”….).

Regarding the rudder:
It has a lower part that is swung rearward via a manual hydraulic pump and a cylinder. With the rudder up, I think you could quickly get in trouble if you are sailing in heavier weather. It is very hard to steer (VERY!), and I only do that with the sails down and motoring. Personally I would not worry too much about it, as it is fairly robust, and the hoses can be inspected somewhat easily (with the boat out of the water). On mine they are not exposed or prone to chafe at all, so just replacing them from time to time, and maybe servicing the manual pump should provide you with a very reliable system.

I think you will be fine if it swings up while offshore (compared to a broken spade rudder). Partly because the rudder actually fall down just by it’s own weight when you lower it. And partly because you should ideally have a fairly balanced sailplan anyway, and maybe even a wind vane steering the boat. If it happens in a storm though, maybe treat it as a broken rudder? I hope I never find out, but I would not put a bolt in a healthy rudder to prevent the “fuse” from letting it swing up in case of an impact. Because even when swung up, it does provide some steering, but broken off, it would be very bad. Regarding cleaning of the cylinder rod, that happens “automatically” as you retract it. I store it retracted in harbor and on anchor to protect the piston. If the weather is a bit rough while on anchor, I leave it down, since the forces from the wave action working on the rudder is bigger than I like.

After I bought her, I have dropped the rudder and did a complete service and inspection of everything relating to the rudder and helm, and I was very impressed by the robustness of it all. And even though no system is totally failsafe, I have very high confidence in the rudder and the lifting mechanism.

Regarding the storm conditions:
I have been in some heavy conditions, but not close to what I would describe as survival conditions at all, so this is just my thinking and how I feel the boat behaves.

My survival plan is a drogue! Plenty of strong places to attach it, and I feel that it is the right strategy (as per Johns chapters on the matter). She does heave-to fairly okay, but personally I never do it. Only done it to test it out and practice in a variety of conditions. I don’t like it as the sheets pushed onto the shrouds gives me “the ick” with mental images of all bad things happening from a chafed sheet, a blown sail, a shroud with load it’s not designed for and hence taking down my mast… I get a vivid imagination while being scared in heavy weather for hours…

For a “normal” storm, I would say she handles really well! She is nice on the helm, and both the Hydrovane and the hydraulic autopilot can steer her effortlessly. As John says, the centerboard up thing actually does work. The boat slides sideways quite noticeably, and going downwind it feels incredibly stable. Even while she is up on plane surfing down a wave she feels very manageable. With a correct sailplan, she will steer effortlessly with autopilot or Hydrovane (and I would presume any other would work equally well).

I am unable to sail her any appreciable amount upwind with winds over about 40 knots, but I get to about 85 degrees to true wind, so clawing off a lee shore without engine might be hard? Note that I am a new sailor, so a better sailor will probably do better. For reference, I manage about 100 degrees of true tacking angles (track on the GPS) in ideal conditions. I don’t know how well she does compared to other cruising boats in this regard.

To sum it all up, I can only second everything that Colin and John has written. She is my first ever sailboat that I stepped foot on. I have had her for about 15 months now, and sailed her a few thousand miles in what could be argued is fairly rough conditions. I have intentionally pushed her fairly hard to test my own and the boats limits. Never have I felt that the boat was unsafe, unstable, or close to it’s limit. She feels safe, stable, and is very forgiving (she must be, she have taken care of me during my steep learning process).

Other boats might be equally good or better for what I know, she’s the only yacht I have ever sailed.


John Harries

Hi Arne,

Good analysis and particularly interesting since, because you are new to sailboats, you don’t have a bunch of preconceived notions.