Alubat , Ovni

[lazeyjack]

Deerefot, that boat was built by two chaps that used to work for me, in NZ Bos and Carr
if you ever do find the lotto, give em a call I believe they are amongst the worlds best
Stu

Vega,

Initial stability is mainly form stability. At least for the first 15 - 20 degrees of heel. The weight of the keel begins really to work after that, with higher heel angles. As the beam is major form stability factor and "deriveurs" have a lot of it. they shouldn't have trouble caring sail in moderate conditions. In the stronger winds they have to reef earlier then deep keeled boats but there is a room for improvement of their performances for more ambitious. Water ballast tanks in their sides would improve sail caring a lot. They would also benefit a lot from the modern sail plan with a fully battened, highly roached main sail, which would provide a lot of sail area with a relatively low center of effort.

As for chances to turn upright after capsize, negative stability depends a lot from the shape of the deck and everything above. Strongly built but light, (aluminum), watertight deckhouse could considerably improve righting chances, but main thing for these boats is that because of described skid factor and breach - proefness they don't capsize.

Being as they are, they seem to have proven their practicality and safety for long distance voyaging with reasonable performances. Meffre's voyages with photos among the ice blocks seems pretty convincing to me.

Lifting ballasted keels seems to offer a lot, but I'm worried about price, complexities and long term potential maintenance headaches which huge lamps of lead attached to a thin, movable plates, could provide. I'm curios what happen when such keel hits a rock at speed. In contrast with that, all ballast inside and daggerboard looks so simple and cheap, practically foolproof. Combined with a thick hull shell as in Metapassion they give a peace of mind and confidence to visit some rough places.

In the end, I must say I'm not some kind of deriveurs - crusader who fanatically propagate his favorite boat. I like many different kinds of boats, trying to keep an open mind. But in general, I do like to sail fast, I prefer simplicity and have special soft spot for lean, narrow boats.

If I ever win a lottery, I would go for something like attached photos. Lottery wining chances being what they are, I'll continue, (slow), designing work on my fast, simple, leen, cheap, steel gaff schooner which I mentioned before.

Milan[/quote]

[lazeyjack]

and I may point out that , the owners have given away sail and just had a lean mean power yacht, built

[Packeteer]

Milan, the Dashews sure have made some nice boats

I could happily sail off in a Sundeer 65, pity i don't have the 3/4 million (US$)

[Packeteer]

Originally Posted by lazeyjack

and I may point out that , the owners have given away sail and just had a lean mean power yacht, built

well, they're over 60 now afaik.

and yeah the FPB is an awesome peice of work

[Vega]

Originally Posted by Vega

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Even if I demand specifically to be informed with stability data, only the more expensive boat builder have sent what I have asked. From Allures I have received a lot of information, but nothing about stability.

These boats have all the Ballast inside the boat.
The Allures 40 has a displacement of 8.8T with 3.8T of ballast.
The Alliage 41 has a displacement of 9.9 and 3.6T of Ballast.
The Ovni 385 has a displacement of 8.5T and 2.9T of Ballast.

Those boats have a similar hull shape, and form stability should not be very different among them.

The Alliage 41 has an AVS of 114.6º and a Stix number of only 32,41. From those three, this is the one that has , with all probability, the best numbers regarding stability. These are very poor numbers for an oceangoing boat.

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Originally Posted by Vega

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They have also a strong negative stability ( A41': more than 0.3 GZ(m)) and when capsized they will stay capsized for a long time (beamy boat with a high center of gravity) . As any small boat can be capsized easily, giving the right conditions, this type of boat (Swing unballasted keel) will not fulfill my criteria for a passage maker.

I have received some new information that as, somehow, changed my opinion regarding at least one of these boats.

I have assumed that these boats, with similar characteristics would have similar stability curves, and if that is true regarding initial stability (against the wind, none of these boats is a match for a similar size and weight fixed keel), that is not true regarding final stability.

Allures have sent me the stability curve of his 44ft…and I was surprised with an exceptional curve for this kind of boat. There are some differences in the design approach that explains that and are related with the weight distribution (only the hull is aluminium) and also with the % of D/B, that are responsible for those good results.

The boat has an AVS of 125 and almost half of the inverted stability of the OVNI 435, that has an AVS of less than 115. That’s a big difference in the final stability and in the capacity of recovering from a knock down or a capsizing.

These numbers, with the particular seaworthiness characteristics, typical of these kind of boats (explained by Milan in a previous post), makes this a very interesting boat, sold also at an attractive price (246.500 euros).

I wish everybody a Merry Christmas and a Happy New Year.