Seaworthiness

That's true. But it does allow for 'reasonable intervention' by the crew to assist this which includes the shifting of ballast in boats that have this capability. This allows Class 40s to meet this requirement.

Well not that funny - it's listed along with all the other races in the race calendar. The NOR and entry requirements are also given with modification by the race rules to OSR-O, including a design review required for keel structures.

 

You are right.
I just saw nothing in the ranking and gallery for the 2008-2009 edition, but the calendar and requirements for 2011 are here.

 

could someone give a link to these rules please...
i was just wondering how one would achive 180° positive stability on a monohull even without rig...
probably its my ignorant stupidity but that seems to be an impossible task if we talk physic laws here and a draft and ballast within acceptable range...

 

The details are on the ISAF website: http://www.sailing.org/sailors/32171.php

There's also the amendments for 2010 listed separately.

The classical interpretation of '180° of positive stability', or a vessel having an AVS of 180, isn't quite what is being demanded. The simple screening via STIX and AVS has been dropped for OSR-0 and instead boats entering these extended races have to prove that they can recover from a complete inversion without outside assistance.

The caveats are that this can involve reasonable intervention from the crew and must be with, or without the rig (to prevent the reliance of buoyancy in the mast). This is really a development of the situation that has existed in the VOR and IMOCA for years and has seen the acceptance of the importance of deck camber and cabin house volume.

 

See http://www.finot.com/nouvelles/actucourse/0300wavre.htm

draft and ballast within acceptable racing range

Open 60 have 4.5m (14.5 ft) draft.

Class 40 only have 3m (10ft) draft.

 

Lots of deck camber, shallow cockpit, and bouyant coachroof. A naval architect can manipulate the bouyancy of the vessel when inverted to achieve positive righting arm at 179+ degrees (a symmetrical boat with CG on the centerline will always have zero righting arm at 0 degrees and 180 degrees heel).

That's how lifeboats, coast guard rescue boats, and some pilot boats have positive stability even when inverted.

 

Older designs often had positive stability to almost 180 degrees, before excessive beam became the norm. Ballast ratio is only one factor, and not a particular big one, in ultimate stability. Beam and deck shape are major factors. The buoyancy in my wheelhouse has the equivalent effect on ultimate stability of adding 3,000 lbs to the keels.
Ballast one side of a beach ball with a 2% ballast ratio and you make it 100% self righting, whereas a raft is not very good in ultimate stability with a 75% ballast ratio. Thus midships shapes closer to a beachball ( trunk cabin with high camber, etc) Need a far lower ballast ratio to have good ultimate stability that a beamy flush decker.

 

The new Pogo40S² N1 has just completed the 180° test for OSR-0. She was held inverted 20 minutes to test for water ingress, then she rolled over with two co-skippers inside.

The designers had given a step by step procedure to fill the lateral water ballast and possibly the front water ballast to disturb the boat from any 'stability' it might have at 180°, but this was not necessary. The Class 40 immediately began to rotate gently at first, then increasingly fast.

Five other pogo40S² are currently in build and five will race the Route du Rhum in November. Three of them will race around the world for the GOR 2011.

 

We have two main type of capsizing, the burst which flat the boat at 90 degree sails in the water, and the waves which can roll over the hull upside down.
The inertia of the wave which roll you over also do the contrary, and put you rightside up. Providing the vanishing stability is at least at 120 degree. But in some case the inertia was enough to right side up low freeboard, flat deck high bulwark inside ballasting type of boat. (Typhoon)
In some case a burst can flat out a 80' coastal schooner, and she is incapable to right side up.
We have a lot of variation. I find ludicrous for a designer to tell the crew how to play with liquid ballast to right side up.
When you are an inverted boat, you are in chock, sometime injured, your internal compass is screw up, and the things are flying, you are going up and down at a speed of 20' a second, the noise is like Woodstock if all the performers and the crowd was singing on the same time, and the banging of the water against the hull is horrific. Let me tell you, you don't start listening the designer to play with valves. You want to kill him.
I prefer high freeboard than the camber deck and large trunk cabin, for reason of comfort to mane the sail and walk the deck at night by bad weather, I like bulwark, with good evacuation they are not dangerous, and good seamanship will do the rest. **** happens, and the maximum time a boat as to be inverted should be less than 2 minutes. Which feel like a day by the way. Twenty minutes inverted I a harbor under supervision is a cup of tea.
I think it is important to design the best boat possible for any kind of situation, to be prepare and ready, inside out. Mostly the crew is the weak link on the chain of event.
Daniel

 

This was done in flat water . A rough sea would have righted her far more quickly.It clearly shows how grossly inacurate our ultimate stability calculations can be.
Flush decks make it far easier to fall, with nothing to get your feet against and nothing between to you and the ocean, but lifelines, with a lot of momentum buildup before you get there.
I prefer two foot wide side decks. Many have never experienced side decks wide enough , which is why flush decks are so popular. If they had they would have less enthusiasm for flush decks.
A well know local designer, named Stan Huntingford, once tried to disuade me from going for 4 inch bulwarks , because, as he said "It would hold a four inch layer of water over my entire deck, and that is a lot of weight."
I said "When ? When I am going to windward?" He said "Yes." I said "When I am heeled 25 degrees, there will be a four inch layer of water over my decks?" He said "Yes ,and that is a lot of weight." I gave up on this world reknown designer ,who actually believed a deck at 25 degrees of heel will hold a 4 inch layer of water over the entire deck ,even, uphill.
I'll bet he knew his mathematical calculations well , tho! Among some , common sense can be the least common of all the senses.
Actually, even with the scuppers closed, it will hold about two or three liters in a rough sea , max.
I have seen a lot of hairbrained theories about what one should do in extremely rough weather, by landlubbers, especially multihullers, things that would be almost impossible in conditions too rough to stand up in.
Good call ,Daniel.
I see people going to extreme lengths to keep a boat safe, with little consideration for the crew. I have a reinforced safety blanket over my setee bunks at sea, attached at three corners, with a snap shackle on the fourth. It is loose athwartships , but tight along the longitudinal sides. It is no restriction in movement and unoticeable when sleeping in the bunk , but in the event of a knockdown, It will keep me in my bunk and not allow me to be throw accoss the cabin.

 

The calculations may be accurate, but not realistic. A good engineer needs to know not only how to do the math, but what it means and what it doesn't mean.

 

Which is to say "Common sense is the least common of all the senses.'
So much for the infallibility of calculations. Nothing like reality to set the record straight.
It appears that it is time to compare the calculated ultimate stability to the real ultimate stability, them work backwards to make the calculations more prone match the reality, over a variety of boats.

 

A valid point, Brent; I think it's one that most designers are already familiar with. We have realistic equations and models for stability, and they produce realistic results if fed with realistic inputs and assumptions.
The trouble is that very few equations or computer models have the ability to put up a red flag and say "Hey designer, this data you're feeding me doesn't look like it matches the real boat or the real conditions that you'd get in this scenario". The designer has to know what he's putting into his calculations and how to make sense of what comes out.
If it were possible to just draw the model, run the numbers and see unambiguously exactly how it would behave, there wouldn't be much use for engineers and designers. Thankfully for those who make a living in this work, it's never so simple!

 

We should not forget that when talking stability we are usually talking "static" stability (infinitely slow movement), which is not intended at all to model the real thing, which is a dynamic and extremely complex problem.

Stability criteria based on static stability and its derivative "dynamic" stability (this last in fact just an "static" work) is nothing else than an statistical approach to non-capsizing scenarios.

Cheers.

 

Class 40 and capsizing.


First, the class 40 whith the 16 year old girl that presumably capsized in the indian ocean.

Then this one, more documented :

http://www.facebook.com/topic.php?uid=247766872007&topic=11581

or

http://forums.sailinganarchy.com/index.php?showtopic=101905



In the french version, the owner clearly states :

"Un Class40 n’est pas assez rapide pour échapper rapidement aux conditions plus difficiles que prévues "

A class 40 is not fast enougth to fastly escape from harder conditions than forecast. (soory, my own translation.)

And it was a racing boat with a racing crew.