Beneteau Oceanis 393 STIX

aquaholic

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Not too up on all of these figures but have just seen a list where it quotes this boat's stix figure as 43.
Thought it was high for this type of boat, not a bad thing obviously, just wondered why, seeing as though the bigger boats have a lower number, any ideas why? does the 393 have a secret weapon of some kind ??????

OCEANIS 343 STIX 34 AVS 134

OCEANIS 351 STIX 35 AVS 125

OCEANIS 361 STIX 32 AVS 120

OCEANIS 36CC STIX 35 AVS 126

OCEANIS 373 STIX 36 AVS 132

OCEANIS 381 STIX 38 AVS 130

OCEANIS 393 STIX 43

OCEANIS 411 STIX 37 AVS 114

OCEANIS 423 STIX 38 AVS 119

OCEANIS 44CC STIX 34 AVS 110

OCEANIS 461 STIX 37 AVS 115
 

dk

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All the others are incorrect - in fact so is the 393 figure, but it's a lot closer!
Class A (Ocean) yachts have a STIX of >32. For most AWB production yachts the STIX is very close to this figure - usually in the 32.1-34.0 bracket. i have the figures on the 393 somewhere - i'll check them out and get back.

BTW - I think you'll find the other numbers are the AVS - that's the Angle of Vanishing Stability - the point at which the yacht loses its positive buoyancy and turns over.

Just found the info - the 393 STIX was 35.8. This figure doesn't actually mean a lot though, as it is rather contrived!
 
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jwilson

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Not too up on all of these figures but have just seen a list where it quotes this boat's stix figure as 43.
Thought it was high for this type of boat, not a bad thing obviously, just wondered why, seeing as though the bigger boats have a lower number, any ideas why? does the 393 have a secret weapon of some kind ??????

The 393 was the updated replacement for the 390, not long after the capsize and inversion in the Bay of Biscay and resulting loss of life from "Ocean Madam", a Beneteau 390. After having had one of their supposedly ocean-capable yachts in a highly publicised tragedy, they increased the ballast ratio on the next new model, the 393, hence the better than typical STIX figure. Beneteau explained the extra ballast as being there to improve sailing performance.

There is nothing much wrong with any of the Beneteau range, then or now, as long as you realise that heavy weather ocean sailing is simply not what they are built for....
 

aquaholic

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Thanks for the link, the RYA figure also show it as 43. I also noticed the displacement as 8500 seems a bit on the heavy side, would this account for the high figure?
 

doug748

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Thanks for the link, the RYA figure also show it as 43. I also noticed the displacement as 8500 seems a bit on the heavy side, would this account for the high figure?

God knows, it is a pretty fuzzy concept, the cynic would say it is as much a political construct as a mathematical one.

The calculations are based on LSW (Light Ship Weight) the weight of the boat without the tons of stuff that people tend to put on board. The figures are supplied by the manufacturers and might well be open to "negotiation", so the different figures may have been derived by taking different basic assumptions about the dimensions of the boat.
 
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God knows, it is a pretty fuzzy concept, the cynic would say it is as much a political construct as a mathematical one.

The calculations are based on LSW (Light Ship Weight) the weight of the boat without the tons of stuff that people tend to put on board. The figures are supplied by the manufacturers and might well be open to "negotiation", so the different figures may have been derived by taking different basic assumptions about the dimensions of the boat.

The cynics would be wrong about the calx being political though I've no doubt that the threshold of 32 was chosen on that basis. Thats the way that international standards work.

To give you an idea of what goes into it, below is the calx for my Starlight 35


Base length 28.24
Righting energy factor 1.193
invesrion recovery factor 1.146
knockdown recovery factor 1.444
displacement/ length factor 1.045
beam displacement factor 1.016
wind moment factor 1.000
downflooding factor 1.250

total stix 45.7

I havent yet been able to find out how each factor is calculated but it is perfectly clear that shear size is an important factor.

By comparison the Contessa 32 has a stix of 33.
 

gregcope

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The cynics would be wrong about the calx being political though I've no doubt that the threshold of 32 was chosen on that basis. Thats the way that international standards work.

To give you an idea of what goes into it, below is the calx for my Starlight 35


Base length 28.24
Righting energy factor 1.193
invesrion recovery factor 1.146
knockdown recovery factor 1.444
displacement/ length factor 1.045
beam displacement factor 1.016
wind moment factor 1.000
downflooding factor 1.250

total stix 45.7

I havent yet been able to find out how each factor is calculated but it is perfectly clear that shear size is an important factor.

By comparison the Contessa 32 has a stix of 33.

Forgive the digging out of an old posts.

How accurate are these figures?
Anyone know of any others published?
Is this for a wing keel?

Ta.
 

sailorman

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Not too up on all of these figures but have just seen a list where it quotes this boat's stix figure as 43.
Thought it was high for this type of boat, not a bad thing obviously, just wondered why, seeing as though the bigger boats have a lower number, any ideas why? does the 393 have a secret weapon of some kind ??????

OCEANIS 343 STIX 34 AVS 134

OCEANIS 351 STIX 35 AVS 125

OCEANIS 361 STIX 32 AVS 120

OCEANIS 36CC STIX 35 AVS 126

OCEANIS 373 STIX 36 AVS 132

OCEANIS 381 STIX 38 AVS 130

OCEANIS 393 STIX 43

OCEANIS 411 STIX 37 AVS 114

OCEANIS 423 STIX 38 AVS 119

OCEANIS 44CC STIX 34 AVS 110

OCEANIS 461 STIX 37 AVS 115

How does it compare with a Co32 :ambivalence:
 

doug748

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Forgive the digging out of an old posts.

How accurate are these figures?
Anyone know of any others published?
Is this for a wing keel?

Ta.



You may well have seen it, the RYA stuff is now here:

http://www.rya.org.uk/newsevents/news/Pages/stabilitylist.aspx


It has been said that the large gaps in the Stability List are due to manufacturers being unwilling to release data.

There have been (on the face of it creditable) comments along the lines that the international agreement on Stix methodology is favourable to mainstream continental manufacturers. Furthermore that this was pushed through only after the UK had folded it's tents as a mass boat builder, and largely absolved itself of interest.

There has been a lot of ideas put forward on how base figures for calculation might be mishandled, for nefarious purposes. Mainly to make big boats appear more stable than they really are.

It requires a lot of reading. Getting to the nub of the matter can also involve subscribing to academic papers to try and find first person evidence. I am not keen enough to spend money, bloody hell.

I think it would make a really good series of articles in YM - to put up some smart bloke, who we could believe in, to tease out the history the politics and the sums. Explaining how builders can keep stability information secret (if this is the case) would be something we would all like to know.
 
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James_Calvert

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I think it would make a really good series of articles in YM - to put up some smart bloke, who we could believe in, to tease out the history the politics and the sums. Explaining how builders can keep stability information secret (if this is the case) would be something we would all like to know.

That's a great idea. Douglas Phillips-Birt ran a series of YM articles in the late '60s/early '70s about yacht design- one of the things that got me hooked on YM (along with JDS of course). I can't remember how recently anyone has done an update, but it's probably well overdue again.
 

gregcope

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You may well have seen it, the RYA stuff is now here:

http://www.rya.org.uk/newsevents/news/Pages/stabilitylist.aspx


It has been said that the large gaps in the Stability List are due to manufacturers being unwilling to release data.

There have been (on the face of it creditable) comments along the lines that the international agreement on Stix methodology is favourable to mainstream continental manufacturers. Furthermore that this was pushed through only after the UK had folded it's tents as a mass boat builder, and largely absolved itself of interest.

There has been a lot of ideas put forward on how base figures for calculation might be mishandled, for nefarious purposes. Mainly to make big boats appear more stable than they really are.

It requires a lot of reading. Getting to the nub of the matter can also involve subscribing to academic papers to try and find first person evidence. I am not keen enough to spend money, bloody hell.

I think it would make a really good series of articles in YM - to put up some smart bloke, who we could believe in, to tease out the history the politics and the sums. Explaining how builders can keep stability information secret (if this is the case) would be something we would all like to know.

Yes, seen this.

No Starlights :-(
 

Tranona

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I think it would make a really good series of articles in YM - to put up some smart bloke, who we could believe in, to tease out the history the politics and the sums. Explaining how builders can keep stability information secret (if this is the case) would be something we would all like to know.
Has been done already at great length by one of the members of the working party (Andrew ? -name will probably come to me later). Probably around the turn of the century when it was a hot topic.

Arguably no longer high on most peoples' agenda, perhaps because on its own it has little bearing on their choice of boat.
 

TimBennet

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I had some involvement with and keenly followed the formulation of the stability requirements in the RCD. I certainly don't recognise the idea that it favoured the large European boatbuilders or that the British lacked involvement. Sounds like a load of UKIP propaganda.

The principal drivers in the formation of STIX were academics from the Wolfson Unit who used the RYA SSS numbers and methodology as the starting point. Certainly the base size value was heavily debated, but there is no denying that big boats are more seaworthy than small. For the cut off at the lower end of 'Ocean Going' (Cat A), a value slightly lower than a Contessa 32 was thought to be appropriate. The actual STIX figure agreed can hardly be construed as favouring say Beneteau for example, as it eliminated the Figaro 1 from ocean races and required them to completely redesign and retool for the larger Figaro 2.

Everyone quotes the classification of boats like the Contessa 26 in CAT B as why the system is flawed but the production of ocean going boats of that size is not commercially viable. Why would people who worked unpaid on the committees drafting the rules work to accommodate boats that are no longer in production when the rules only apply to new boats at the 'point they first enter the market' ?

Reducing all the components of 'seaworthiness' into a formula is not going to be easy. STIX is not a bad stab at doing this, but there is no impetus in the offing to expend the vast amount of energy and work necessary to garner international agreement on any major revision. For those who worry that the size of the boat is unduly influential should try using the oft floated idea that the STIX of Cat A boats should be equal or greater than the LOA in feet. It's also quite interesting to extend this idea downwards to boats below 32 feet. I think the idea has merit but until research funding is forthcoming, it remains a hunch.
 

doug748

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Sounds like you are just the man to take the project on, TimBennet. What is your view of the gaps in the data? Should we ignore the lot because nobody is interested, as Tranona suggests?

10 years seems a long turnover time for any topic.

Trouble with single numbers is that they tend to take on a life of their own. Some big production boats have very poor Stix figures which look very nice when you are told by the nice salesman that they are well above the minimum for going round the globe.
 
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