How to test sail an Ovni

[Polux]

Originally Posted by noelex 77

I have seen both the K&M (Bestevaer) and Allures aluminium production facilities. K&M are actually quite a bit larger, but this matters little.
... There are therefore few cost savings for the hull build that a larger yard can take advantage of.

Yes K&M shipyard is larger and it has to be because contrary to Allures they make rather larger yachts, some with 90ft (many custom yachts) and in what regards aluminium semi custom yachts besides the Bestevaer they make the Stadtship (Van de Stadt) as well as Axonite (big yachts) and the Opus 68 more big custom yachts.

I also agree with you that the size of the yard dos not matter in what regards price contention. One of the things that matter is the number of produced boats and I do not mean very different boats but identical boats from the same model. A big production can reduce costs significantly and that's what happens to Allures that is the Aluminium brand that now produces more boats of each model, specially the 45 (and the previous 44).





That contributes for the the huge difference in price between a similarly sized Allures and a Besteaever, that has very few similar unities produced.

Originally Posted by noelex 77

I will try to find some links to the Garcia ballast, but while I was unsure about the Allures ballast I am positive that Garcia do not use lead at least on the Garcia Salt and Exploration 45.

I am very curious about that. I have searched and found nothing regarding the ballast material but it is hard for me to accept that it is iron. It just does not seem to make sense.

I hope you can remember where you saw that they have an Iron/Lead ballast. I would be very interested in hearing why.

[Balance]

Originally Posted by Polux

Ballast on the Allures and Boreal is lead too and that with most of it outside on the sub keel gives them a better stability and a higher AVS than the OVNIS. On the case of the Allures, a very light infused cored GRP deck further contributes to lower the CG and increases even more stability.

Note that the GRP deck/hull connection on the Allures is not like on all GRP boats, I mean the Aluminium hull extends inside to the deck for some 30cms and the deck is put over it, bonded and aluminium riveting. They use the system from the beginning without problems.

I wonder how well the lead ballasted centre boards when raised will perform over a bar crossing?

[noelex 77]

Originally Posted by Balance

I wonder how well the lead ballasted centre boards when raised will perform over a bar crossing?

The centreboards for the Ovni, Garcia and Boreal are not ballasted. (They are just solid aluminium which does not have much weight in water). The ballast is in the hull or sub keel (although I think Ovni did have one model with some ballast in the keel).

So the stability and AVS is essentially unchanged as the centreboard is raised/lowered. In survival conditions these boats actually raise their keels so they side slip more effectively.

[noelex 77]

Originally Posted by Polux

I hope you can remember where you saw that they have an Iron/Lead ballast. I would be very interested in hearing why.

See here under construction:
http://www.garcia-italia.it/wp/wp-co...45_english.pdf

The popular Garcia Salt series had the same ballast material.

[Polux]

Originally Posted by noelex 77

See here under construction:
http://www.garcia-italia.it/wp/wp-co...45_english.pdf

The popular Garcia Salt series had the same ballast material.

Thanks. I had searched a lot and could not find any reference to the Garcia's ballast material -resin-insulated iron cast/steel ballast - (and I think it was not by accident) while I had not any difficulty in finding information regarding the lead ballast of the Allures and Boreal.

But the central point is not that, I seem to recall you said that each shipyard claimed that its ballast material was the best or more appropriated and I cannot see evidence of that.

In fact the use of iron instead of lead on the Garcia can only be due to what they will consider acceptable cost reduction with small inconvenients. They will need a bigger and fatter skeg for housing the same weight of iron that would fit on a smaller skeg with lead. That will increase drag that they probably would consider not very important on this type of boat.

Iron is also a much worse material to be in contact with aluminium (comparing with lead) so they will have it insulated with resin but any insulation can grow cracks with time and then Iron contacting with aluminium can lead to a serious galvanic problem.

So in my opinion, a better solution it isn't (and that's why it is so hard to find information about the ballast material) an acceptable solution regarding cutting costs? It is a matter of opinion. I don't like it and it seems a lot worse to me then using iron as keel material on a fiberglass boat (like most use these days).

[Polux]

Originally Posted by Balance

I wonder how well the lead ballasted centre boards when raised will perform over a bar crossing?

Noelex had already said that the boats I was talking about have not ballasted centerboard but others have like Southerly (that has ballast on the centerboard) or with a Pogo, a Wauquiez Opium, some Comet or some aluminium boats that have all the ballast on a swing keel.

In any case these boats will remain with plenty stability with the swing keel up (remember that up is not inside the hull but a bit like on a skeg on the mentioned aluminium boats) and it will only not advisable to sail the boat on those conditions with medium or strong winds. Not a problem while motoring, probably an advantage.

To put it more clearly I would say that the AVS point (the angle where the boat will turn turtle) on a Pogo with a swing keel up is about the same on most OVNIs, both over 100º.

[robert sailor]

I'm told that boats like the Ovni with less righting moment than most people would like to see on an offshore boat make up for it by raising their boards in **** weather and allowing the boat to slide down waves rather than tripping over the keel and possibly rolling. Is the Pogo in the same boat??

[Polux]

Originally Posted by robert sailor

I'm told that boats like the Ovni with less righting moment than most people would like to see on an offshore boat make up for it by raising their boards in **** weather and allowing the boat to slide down waves rather than tripping over the keel and possibly rolling. Is the Pogo in the same boat??

You mean If a Pogo can do that? Well it could since the reserve stability is not that much different with the keel up but I doubt that any Pogo sailor would do that because the stability with the keel down in simply huge and will be more than enough to get the boat out of trouble sailing the storm with reduced sail.

Besides the Pogo keel is a very narrow one and it would have not a significant tripping effect. That effect would be several times more substantial on a medium profile fin keel, much more on modified fin keel and even more on a full keel boat. Have a look at the 30ft Pogo keel:

[noelex 77]

Uu

Originally Posted by Polux

You mean If a Pogo can do that? Well it could since the reserve stability is not that much different with the keel up but I doubt that any Pogo sailor would do that because the stability with the keel down in simply huge

Ballasted swing/lifting keel yachts tend to have a much better stability curve than non ballasted centreboard boats, but it is important to lock the keel down with a very strong mechanism. The ballasted keel retracting as the boat goes inverted is not a nice thought.

Small yachts need a better stability curve than their larger brethren. I don't like just quoting the AVS, it is better to look at the whole stability curve. However, it is a convenient single number, but have a look at the whole stability curve in the link.

The Pogo 12.50 has an AVS with the keel down of 124°. This is an good number, but with the keel up it reduces to only 100°. This is a very low number, especially for a yacht of this size. So it is vital the keel is locked down. If inverted with the keel up my guess is that it would spend a very long (ie too long) time inverted. Looking at the stability curve it needs almost the same force to trip it back to the right way up.

fastsailing.gr - Stability Curve - The yachts , Absolutely Safe

For comparison the unballasted swing keel Garcia Exploration (a very different yacht) has an AVS of 118° and would be almost identical keel up, or down.

The Pogo 10.50 has just slightly better numbers with the keel up (124° and 105°) but given the smaller size the risk of capsize is greater.

[Polux]

Originally Posted by noelex 77

Uu

Ballasted swing/lifting keel yachts tend to have a much better stability curve than non ballasted centreboard boats, but it is important to lock the keel down with a very strong mechanism. The ballasted keel retracting as the boat goes inverted is not a nice thought.

Small yachts need a better stability curve than their larger brethren. I don't like just quoting the AVS, it is better to look at the whole stability curve. However, it is a convenient single number, but have a look at the whole stability curve in the link.

The Pogo 12.50 has an AVS with the keel down of 124°. This is an good number, but with the keel up it reduces to only 100°. This is a very low number, especially for a yacht of this size. So it is vital the keel is locked down. If inverted with the keel up my guess is that it would spend a very long (ie too long) time inverted. Looking at the stability curve it needs almost the same force to trip it back to the right way up.

fastsailing.gr - Stability Curve - The yachts , Absolutely Safe

For comparison the unballasted swing keel Garcia Exploration (a very different yacht) has an AVS of 118° and would be almost identical keel up, or down.

The Pogo 10.50 has just slightly better numbers with the keel up (124° and 105°) but given the smaller size the risk of capsize is greater.

I have some difficulty in understanding your point in what regards the answer I had given to Robert. Robert was talking about OVNIs compared with Pogos, not about any other boat.

Many OVNIs have a AVS around 105º. New models are a bit better (due to increasing stability demands of the RCD) but most OVNIs around have a low AVS.

Taking two boats with not very different sizes, a OVNI 345 and a Pogo 10.50, we will see that the Pogo has about the same AVS with the keel up as the OVNI on sailing condition (106º and 107º).

If I remember correctly there are OVNIs with a smaller AVS. They had a politic of not made available AVS and is dificult to have them but I have somewhere the stability curve of the famous OVNI 43/430 (the one with whom Cornell circumnavigated) and if I believe its AVS was slightly less than the one of the OVNI 345 and older ones can even have less.

So regarding what Robert asked (OVNIs and Pogos) I think my answer was correct.

I said also that no Pogo sailor would consider to have the keel up in bad weather conditions even if on boats with a similar AVS (the reserve stability is not very different), it would not make much difference (Pogo with a keel up versus OVNI), except that the Pogo would have a much superior stability with a keel down and that and the small surface of the keel in what regards a tripping effect would make that a far better solution.

Regarding locking the keel all the boats that I know off that have a full ballasted keel have a system to block the keel down.

[noelex 77]

Originally Posted by Polux

I have some difficulty in understanding your point in what regards the answer I had given to Robert.

My point was that the stability of the Pogo with the keel retracted is in my view not adequate for offshore sailing. (Keel down is fine)

The peak righting movement at a very low angle of heel (not much more than 30° from the graph) This means from a normal sailing angle you are not very far from loosing control. This together with the low AVS and high inverted stability means I would not be comfortable sailing this boat with the keel retracted offshore.

The stability curve with the keel retracted is shown in purple on this graph:

[Jim Cate]

Originally Posted by noelex 77

My point was that the stability of the Pogo with the keel retracted is in my view not adequate for offshore sailing. (Keel down is fine)

The peak righting movement at a very low angle of heel (not much more than 30° from the graph) This means from a normal sailing angle you are not very far from loosing control. This together with the low AVS and high inverted stability means I would not be comfortable sailing this boat with the keel retracted offshore.

The stability curve with the keel retracted is shown in purple on this graph:

The curve with retracted keel is SCARY!! I surely agree with you re sailing with it up. If one became inverted with sails up, it might well stay that way forever... or until the mast failed.

But I agree with Pollux that no Pogo sailor is likely to sail with it up...

Jim

[roverhi]

Lead and Iron are right next to each other and to various aluminum alloys. From that, lead is very little better as far as galvanic corrosion than steel/iron. Steel/iron is cheaper than lead so may be the reason that they chose it but it is not structurally worse than lead. Iron/steel is a pretty common ballast for sailboats especially fin keel boats and probably gaining in use because of the ultra short keels with bulbs currently in fashion.

Originally Posted by Polux

Thanks.

In fact the use of iron instead of lead on the Garcia can only be due to what they will consider acceptable cost reduction with small inconvenients. They will need a bigger and fatter skeg for housing the same weight of iron that would fit on a smaller skeg with lead. That will increase drag that they probably would consider not very important on this type of boat.

Iron is also a much worse material to be in contact with aluminium (comparing with lead) so they will have it insulated with resin but any insulation can grow cracks with time and then Iron contacting with aluminium can lead to a serious galvanic problem.

So in my opinion, a better solution it isn't (and that's why it is so hard to find information about the ballast material) an acceptable solution regarding cutting costs? It is a matter of opinion. I don't like it and it seems a lot worse to me then using iron as keel material on a fiberglass boat (like most use these days).

[robert sailor]

Polux I do have to say that I have been bitten by that Pogo 12.5. That is a damn cool boat and it sails like a witch. I wish I was 20 years younger and not needing a so called cruising interior because I would buy that boat for sure!!

[K_V_B]

Originally Posted by Jim Cate

The curve with retracted keel is SCARY!! I surely agree with you re sailing with it up. If one became inverted with sails up, it might well stay that way forever... or until the mast failed.

But I agree with Pollux that no Pogo sailor is likely to sail with it up...

With boats like the Pogo you're only supposed to raise the keel when you're entering shoal draft areas, and this probably only under engine. It's not like with centerboarders where down wind you will raise the keel to improve your trim.
With a Pogo it's going to be "keel down, then sails up".

Anyway, the Pogo is inspired by the Class 40, and those boats actualy have to demonstrate that they will not remain upside down. Here is an example of a test. with people on board!

https://youtu.be/4gC1lPI_lJk