Beneteau oceanis 55

[Polux]

Originally Posted by robert sailor

THe Contessa 32 is simply a British cruising boat that was popular enough that it had is own one design class. It wasnt designed specifically for offshore sailing, it was simply a British design. ....

These days yes the EU does but you can't compare a high production older cruising design to a current racing design, you compare it to a current cruising design. No one on this forum cares about a boat they will never own but I'm sure some here might be interested in how a current cruising boat stacks up with an old one. You featured a Dufour 31 a day or two ago why not compare the AVS on that boat to the Contessa??

"Since first launching from the Rogers yard in 1971 she has become widely recognised as the most popular racer cruiser ever "

About the ever I don't know, lot's of popular cruiser racers, but regarding to be a cruiser racer and a popular one there is no doubt. As you said it has even his racing class as a one designed boat.

The Contessa 32 was not a main market boat like the Dufour 310 but an old small offsore cruiser racer and if you want to compare it it is not with small main market modern cruisers but with modern small offshore cruiser racers (or performance cruisers).

Performance cruisers or cruiser racers, because they need to be more powerful have a superior overall stability when compared to main market designs of the same size and that's because it is a cruiser racer that the Contessa 32 has such a good stability: It needed the power for racing, the extra seaworthiness comes as a bonus as in all performance cruisers.

The boats I was talking about that you, probably without intention but just by ignorance, are calling a "current racing design" is not such thing, not even a cruiser racer but a performance cruiser.

Yes, it is influenced on his hull design by the current trend in what regards solo racers design, the same way the design of the Contessa 32 was influenced by the design of the racing boats of his time.

This boat that I gave for example is far to be alone in what regards cruising market offer having several brands similar boats on the market, being the most known the Pogo with the Pogo 30.

Regarding nobody buying boats like that it is quite obvious that they are selling today in hugely bigger numbers than the Contessa 32, that is still on offer on the market:
Contessa 32 New Build | Jeremy Rogers Limited
but selling nothing for the simple reason that these new boats, offering a similar seaworthiness (in different ways) offer also a hugely bigger interior a much bigger speed at almost half the price.

Regarding not anybody buying these modern performance cruisers I guess that as usual you are mixing what you would buy with what the ones that are on the market for a sailboat would buy and the reason why are several builders doing them is because there is a market for them and they are selling boats.

I was talking about these type of performance cruisers as the ones that today offer more seaworthiness and speed, like it was with the Contessa 32 in its time but there are other boats, small mass production performance cruisers, that are probably as seaworthy as the Contessa 32, among them for instance the Azuree 33, the Arcona 34 or the Dehler 34 and those are even less expensive than the Django or the Pogoand cost less than half the price of the Contessa 32.


Here you have the Azuree 33 on a very tough Middle of the Sea race that saw 60k winds, were many boats retired, among them a Oyster (with a broken rudder) and that the Azuree 33 finished sailing fast with only a crew of two, being one of them the boat designer:

https://www.youtube.com/watch?v=NCAHUe8UglA

https://www.youtube.com/watch?v=a7XsyAkTmZ0

[robert sailor]

I'm waiting for your reply on how your new racer could deal with breaking seas 3 to 4 times higher than what a Contessa 32 could and NOT be rolled.

[neilpride]

You cant compare a contessa 32 with a Dufour for god shake!!!
The Contessa 32 is a rare piece of art in hull design , well proven in heavy weather...
I want to see one of those Dufours or Arconas in a really bad Fasnet....

[Polux]

Originally Posted by robert sailor

I'm waiting for your reply on how your new racer could deal with breaking seas 3 to 4 times higher than what a Contessa 32 could and NOT be rolled.

I did not saw a your question but it is pretty simple: The energy needed to be rolled by a wave is proportional to the energy the boat can oppose it and that energy is measured by the positive area under the RM curve.

when I said that, I was talking about the Django 12.70, having as reference the stability curve from the Pogo 12.50 (that is a very similar boat) and the stability curve of the Contessa 32.

You can see that the Stability curve from the Pogo 12,50 and the Contessa 32, regarding shape have about the same are under, being the one from the Pogo more rounded and compensating the one from the Contessa with the extra area due to the bigger AVS.

So we can say then the MAX RM on both curves will be a good indicator between the proportionality of the total are under the RM curve on both stability curves. The value for the Pogo 12.50 is 6.3T/m and the one of the Contessa 32 is 3T/m (after the needed calculations).

Regarding only static stability, to capsize the Pogo 12.50 it will be needed a bit more than two times the energy needed to invert the 32ft Contessa.

But talking about only a bit more than two times diference it would be to forgot the importance of the dynamic stability and regarding that, while only a part of a breaking wave energy will be turned on a Pogo 12.50 (or similar boat) into a rotating moment, a hugely bigger part of a wave energy would be directed in a rotating moment on the case of the Contessa 32 and that due to the hugely bigger trip effect of the big area of the Contessa keel. Look at the difference in keel area surface:



That triping effect (that prevents the wave energy to be dissipated in a sliding movement) is proportional to the immersed area of the keel and the almost absence of it is what makes aluminium French centerboarders, that normally have a worse static stability than keel ballasted monohulls, so seaworthy.

The effect is described here on drawings on an old book by Eric Tabarly that had a big knowledge regarding both types of boats and keels. Note that what was then a small keel surface is a big surface now, having modern keels less surface area. [/IMG]



You are right regarding the size of the waves, I should have said breaking wave's energy and regarding that for capsizing the Django 12.70, taking into account only static stability, it would be needed a bit over two times the energy.

Regarding dynamic stability and the big difference regarding the proportion of the wave energy that would be transformed in a rotating moment (face to the one that would be dissipated by a sliding movement), the diference would be huge and that's why I talk about 3 or 4 times a bigger wave, or more correctly, a breaking wave with 3 or 4 times the energy of the one needed to roll the Contessa 32.

Originally Posted by robert sailor

..Guys like Polux are masters at the internet and have a huge library of information (which is why his stuff can be quite interesting) I use a little 7 inch tablet and a weak WiFi signal to try to dig up info but most of it comes from memory which can be scarey as it doesn't work anywhere near as good as it used to, lol. That aside I dug up a recent article by a respected sailor that actually had the information I was looking for so if you want a good short read about choosing a sailboat and stability ranges, take a moment and read it as its an excellent article and speaks to both my opinions as well as Polux's opinions.
Understand your boat and her statistics

You confound knowledge with internet speed access.

Regarding this article that you quote:
Understand your boat and her statistics

There is nothing there regarding calculating the boat overall stability or regarding dynamic stability. For that you have to look at papers from the Naval architecture schools or universities specifically about the subject.

The article, on a very conservative magazine (believe me I know, I signed that magazine for 10 years before it become stuck in the past) by two conservative sailors is about how to chose a conservative boat.

Nothing wrong with that, except if one think that conservative cruising boats are the ones all sailors should have as bluewater boats and that unfortunately is not the case with that magazine and particularly with Chris Benson with whom I exchanged in the past some emails about the subject.

That bias regarding a given type of boat, namely a heavier boat, being better for passage making, regardless of the sailor's preferences is evident on the way they analyse the different boat ratios and information, with some misinformation by the middle.

From their 6 decision tools and the way they are interpreted, 4 are full of bull and bad information regarding what they mean with factual errors by the middle.
Displacement/length (D/L) ratio
Ballast ratio
Sail area/displacement (SA/D) ratio
Angle of vanishing stability (AVS, also known as LPS, the limit of positive stability)
The stability index (STIX) number
Polar charts

Not the place to make that extensive analyse here.

[AJPT]

Originally Posted by Bubu delaMancha

Intresting to learn that, about the Beneteau dealers asking about Hanse Surely there must be a reason they are asking about that particular manufacturer.

Have not been on the O-55 yet. Went to Southampton show in 2016 and if I remember rightly the largest oceanis there was O-48. They only had Sense there from the larger boats. Seems like they want to get their money back for designing the Sense, promoting it like this. Personally I really like the look of the O-55, the luxurious cockpit with navigation screens in front of every helm station...also the dining area is massive. I think the under waterline hull is solid laminate,above is sandwich. Are you a sailing couple? Would Oceanis 50 be too small for your purposes? Must say though that the 55 is a grand boat

Yes it is interesting that they always mention hanse. I guess beneteau main rival is Hanse now. Hanse are the second largest boat builders in the world, they recently won boat builder of the year award too. They must be doing something right.

We are a cruising couple yes, we don't have our heart set on the 55, it's a option. Been on the 48 a few times, can't seem to get excited about that. Would rather have a hanse 505 or go for something a bit more up market like wauquiez pilot 48 or grand soleil 46.

Everything is a trade off, I'm sure we will find the right Boat in the end.

What are you leaning towards at the moment?

Forgot to say, there is a new hanse 535 coming out soon, I've heard it will have a lot of styling cues from the 588 and 575.

[Polux]

Originally Posted by neilpride

You cant compare a contessa 32 with a Dufour for god shake!!!
The Contessa 32 is a rare piece of art in hull design , well proven in heavy weather...
I want to see one of those Dufours or Arconas in a really bad Fasnet....

yes, we agree there. The Contessa 32 cannot be compared with a Dufour 310 since they are different types of boats. Regarding the Arcona I disagree. Regarding the Fastnet I don'r remember on the last 15 years any edition worse than some editions on the "Middle the sea race", maybe you can point me one and many small modern fast boats do the Fastnet and and one of them have even won one of the last editions.

Regarding the Middle the sea race and editions with bad weather, besides the videos that I posted before with a Azuree 33, you have here one with a 34ft Dehler that is a boat similar in type with the Arcona, on a 55ft squall:

https://www.youtube.com/watch?v=NPm-J6Djs9E

[neilpride]

This vid show a mild squall , nothing compared with a sustained F10 in the 79 fastnet.
again hard to see a Dufour or a Arcona on those conditions leaving .unscratched..

[robert sailor]

Huge number of words Polux but the long and short of it is that a large breaking wave really doesn't care how much stability your boat has as a rough rule of thumb is that a breaking wave 1/2 your length on the beam is enough to roll a boat. What happens after your boat is rolled is different in each boat, as the example given, the Contessa 32 would self right immediately while a Bavaria 32 would remain inverted for 2 minutes and would likely need help from another wave to get back on its feet. That's the reason that overall length is a very large safety factor in offshore sailing. I will say that having no keel will sometimes help the boat absorb some of the energy by sliding down a wave as it doesn't have a keel to trip over but in the real world of sailing you must do your best to avoid getting caught beam on to breaking seas as every now and then a wave much larger could catch you. Using beam as the key part of stability and reducing the ballast is shown quite well in the article I pasted where it compared the Contessa 32 to a modern beamy Bavaria 32. Anyways its been a fun discussion and I think we have worn this one out. Cheers, R

[Polux]

Originally Posted by neilpride

This vid show a mild squall , nothing compared with a sustained F10 in the 79 fastnet.
again hard to see a Dufour or a Arcona on those conditions leaving .unscratched..

The boats that had problems on the 1979 were IOR racing boats, most of them half tonners that had a lousy AVS and not much stability. Quite stupidly the IOR rating formula give advantage to boats with a low stiffness so for being competitive they tended to have little ballast (and a bad AVS), using meat on the rail for stability.

After that race the changed the rule (IMS than IRC) and since them the handicap does not favor a low CG anymore. The Fastnet 1970 was also at the origin of the studies that lead to the creation of the RCD.

Saying all this, with the advances in meteorology they would never allow a sail race on those very exceptional conditions. It is impossible to know if any small sailing boat would not be rolled on those conditions and if rolled would not lose the mast(on those conditions it was a matter of luck or lack of it) but certainly with today's boats you would not had the carnage and all the causalities that happened on that race.

Sail boat design evolved a lot regarding safety since that time, namely regarding the minimum AVS required and the ability to keep on sailing (superior stiffness) that was one of the conditions that was found as the most important in what regards survival. The boats that had the ability to keep on sailing on the storm were nor rolled and made it safely home, or retired to safe havens.

[neilpride]

Yeah yeah, but but,when you leave harbour you are in your own, saying that any offshore race is a matter of luck, oh boy with a strong front coming to you 400 miles from any safe bar i doubt any sat phone telling you you are in big **** is going to save the day... Sydney Hobart come to my mind to....IOR ? yes thats what they have those days ,,,, even today can happen again... when ? who know... big boys take advantage of bad conditions and small boats take a beat...


If you ask me i prefer to be in a f10 in a Contessa against a Dufour....

[Polux]

Originally Posted by robert sailor

Huge number of words Polux but the long and short of it is that a large breaking wave really doesn't care how much stability your boat has as a rough rule of thumb is that a breaking wave 1/2 your length on the beam is enough to roll a boat. ...

I had given you the hard data regarding those two boats and the energy needed to invert them, being one several times easier to invert than the other and you come with some empiric rule as if all boats were equal in what regards overall stability (if they have the same length on the beam)? As is if the CG or the tripping effect of the keel surface or lack of it mean nothing?

What do you mean by length on the beam? It is maximum beam? Are you saying that independent of CG and underwater surface, beamy boats are more difficult to capsize?

Are you saying that a boat with a 4m beam would be capsized by a breaking wave with 2m? If you are saying that is nonsense and if you are not saying that I don't understand what you mean.

[CbroTheDude]

Originally Posted by Polux

I had given you the hard data regarding those two boats and the energy needed to invert them, being one several times easier to invert than the other and you come with some empiric rule as if all boats were equal in what regards overall stability (if they have the same length on the beam)? As is if the CG or the tripping effect of the keel surface or lack of it mean nothing?

What do you mean by length on the beam? It is maximum beam? Are you saying that independent of CG and underwater surface, beamy boats are more difficult to capsize?

Are you saying that a boat with a 4m beam would be capsized by a breaking wave with 2m? If you are saying that is nonsense and if you are not saying that I don't understand what you mean.

Not commenting on where the rule might have been invented, but I guess he meant "a breaking wave hitting a boat on it's flat side, the wave measuring (from bottom to top? From middle to top?) half the LOA of the boat "

[robert sailor]

Originally Posted by CbroTheDude

Not commenting on where the rule might have been invented, but I guess he meant "a breaking wave hitting a boat on it's flat side, the wave measuring (from bottom to top? From middle to top?) half the LOA of the boat "

Thank you my friend, that's exactly what I said and it's a very good rule of thumb. A 32 foot boat if hit on the beam with a 16 foot breaking wave can be rolled. One of the reasons the STIX formula won't meet the CE ratings for smaller boats. You could have a longer boat built to the same specs as the smaller boat and it would meet the rating because length is way more important in CE rating stability that draft or beam. Basically as Calder said in his article you want a STIX number at least equal to the length of the boat but as a remark he felt that number was actually too low and it should preferably be higher.

[robert sailor]

I meant to say the CE Class A rating as the smaller boats all meet a CE rating but the A certification is supposed to be required for offshore.

[Polux]

Originally Posted by robert sailor

Thank you my friend, that's exactly what I said and it's a very good rule of thumb. A 32 foot boat if hit on the beam with a 16 foot breaking wave can be rolled. One of the reasons the STIX formula won't meet the CE ratings for smaller boats. You could have a longer boat built to the same specs as the smaller boat and it would meet the rating because length is way more important in CE rating stability that draft or beam. Basically as Calder said in his article you want a STIX number at least equal to the length of the boat but as a remark he felt that number was actually too low and it should preferably be higher.

????? Great confusion there. I don't know about what you are talking about but I think you should read the RCD requirements regarding boat stability instead of looking to a magazine article that is not even about that.

Of what size of boats are you talking about? RCD has a minimum mandatory AVS that depend on boat mass not length of the boat. Lighter boats have to have bigger AVS and there are many other factors has a minimum downflooding angle.

They have also a minimum STIX and for the STIX number, that is the more controversial factor on the RCD (as it is said rightly on the article), length is important but it is only one of the factors and if the other factors are very good it is possible to certificate as RCD class A monohulls as small as 25ft. The Smaller I know certificated as Class A is the Django 7.70.

Saying that there is a direct proportion between the length of a boat and the size of the wave that will be needed to capsize it equals to say that all boats with the same length have the same overall static and dynamic stability and that obviously does not make any sense for many reasons.

The length of a boat has no direct relation with stability unless the beam is proportional as well as other factors like the CG and mass. Normally bigger boats have bigger stability because in a general way and regarding similar typed boats all those factors tend to be roughly proportional, but that is only true for similar boats and there are many different types of sailing boats.

The Contessa 32 and Pogo 30 are good examples of a small boat that, for different reasons, have an overall stability superior to the generality of boats of that size and equal to the overall stability of bigger boats.