Seaworthiness

Quite right, Vega, thanks.

 

No, maybe this photo helps. It is not the cruising version, but Ibelieve the hull is the same, the keel is shorter (80cm) and the bulb heavier. the boat will weight more and it will seat a little bit more on the water.

 

There it is

 

Not all modern narrow boats have a high AVS, and that doesn’t mean that they are worse than the Nordborg.
Take a look at a favorite of mine, the Faurby 424, also a Danish boat.

It is a beautiful boat a little bit longer, but also a little bit lighter.

If we compare the GZ curves, we will see that the Faurby has a much bigger max rightening arm (0.77 to 0.55), that at 90 of heel the Faurby has 0.52 and the Nordborg 0.46 and that regarding initial stability there is a huge difference favorable to the Faurby:
At 10º of heel, 0.15 to 0.2, at 15º, 0.2 to 0.3.

In what regards AVS and negative stability, there is also a big difference, this time favorable to the Nordborg (AVS, 119 to 140).

This makes the Norborg a better or worse boat than the Faubry?

I think that depends of what you want, certainly the Faurby is a lot faster and the big question would be: Is the Faurby an oceangoing seaworthy boat?

I would say yes. The negative stability is acceptable and the AVS, if not great, is also inside the average and probably, even compensating for the difference in weight, it will be probably needed more energy to capsize the Faurby than the Nordborg and both boats will be making about the same force to re-right themselves at 90º of heel.

http://www.faurby.dk/gb/faurby424_teknik.html

 

Vega, thanks for the side view of Pogo cruising version, I have been looking for that. The bulb would influence LP slightly (bulb numbers included within brackets). I get (approx. figures);
LP/SA: 7.9% (9.4%)
KA/SA: 3.7% (5.1%)
RA/SA: 0.9%

It's a skimming dish all right, HA/LP is a low 42.7% (36.2%), RA/LP is 11.1% (9.4%)

The Faurby on the other hand shows (assuming no fractional rig and genoa 1);
LP/SA: 13.9% (14.6%)
KA/SA: 5.7% (6.3%)
RA/SA: 1.0%
HA/LP: 52.1% (49.7%)
RA/LP: 7.2% (6.9%)

Pogo has twin rudders, I have just doubled the area disregarding angle, I simply don't like the configuration and haven't bothered spending time on it.

I was looking for the LWL figure on the Pogo 40 website until I remembered that it doesn't need one, I find that funny Good to see that the bulb of the cruising version doesn't extend in front of the keel, get's a bit boring to drag the Sargasso Sea along around the world

I see a low LP/SA for Pogo, too low in my opinion and I am surprised that both boats show low RA/SA. I consider 1% not enough, but on the other hand, Faurby's LP/SA and KA/SA is rather high. May I have your thoughts on this please

Mikey

 

OK, Norborg figures (with genoa);
LP/SA: 16.4% (16.8%)
KA/SA: 6% (6.4%)
RA/SA: 1.4%
HA/LP: 54.7% (53.4%)
RA/LP: 8.4% (8.2%)

Faurby Norborg
LWL/Bmax 3.3 3.2 (don't have Bwl)
SA/Disp 20.7 20.3 (don't know how much overlap)
Disp/LWL 137 210
Ballast ratio 39.9 37
LP/SA 14 16 (bulb not included)
KA/SA 5.7 6
RA/SA 1 1.4
AVS 119 140

Faurby relies more on form stability and is stiffer, it also has higher accelerations so Norberg will have more comfortable motion, SA/WSA is much higher for Faurby, it will be much faster all around but especially in light winds. Norberg's larger rudder area (and skeg) is a plus IMO. Storage in Norberg is better.

Is the Faurby an oceangoing seaworthy boat? Well, the question - Is the Faurby a good oceangoing cruiser for your round-the-world trip is easy to answer. No, the compromise is a bit on the extreme side.

Oceangoing seaworthy boat then? Yes, but clearly at the lower end of the scale. Its relatively high LP/SA and KA/SA saved it from a No (took me an hour to decide which )

Mikey

 

"Is the Faurby a good oceangoing cruiser for your round-the-world trip" surely depends on what YOU want to make of YOUR trip.

For the people who cruise around the world (with a baby born on the way) in 25 footers, the Faurby would surely be "good". For the couple who have been cruising for about 14 years+ on an old stripped-out flush-deck IOR lightweight with runners, the Faurby would surely be "good". For the family of four who live on a fairly spartan cat, it would be "good" in some ways.

Surely in the same way that we can choose to drive a Ferrari or a 4wd or a sedan or a people mover, or the way we can choose to live on a farm or an inner-city unit, we can choose what is "best" for US, our way of sailing and our way of life.

 

Here is an interesting data point to add to the discussion ...

I spent some time talking to a gentleman that circumnavigated in a 34 foot boat. I asked about how the boat was rigged and found that it is a sloop with an inner forestay added to make a cutter rig. They have a roller furling Genoa on the headstay, the heavy air and storm jibs hank on to the inner stay.

I asked him how often they had to roll the Genoa up and use the storm sails ... his reply was "Never".

He did admit that they got caught in one squall and saw 55 knot winds for about 2 hours. During the squall, they just dropped the sails and waited it out.

13 years sailing, including a circumnavigation (they spent 6 years in the Med), and they NEVER had to use the storm sails. Kind of makes me question how much weight to place on ultimate stability and storm survival when choosing a boat. The way some people talk it sounds like having to deal with storm conditions is likely and unavoidable, yet the people that I talk to that have actually sailed oceans and circumnavigated tell a different tale.

 

That depends on where and when you sail. If you are in the north Atlantic in the winter you will probably meet a storm

 

Thanks, Paulo.
Working on that image to estimate measurements, I get an STIX of 38,475 for Pogo 40 Cruiser in MOC condition. You posted before her real STIX is around 41 for this condition. May I see the complete calculation sheet you have (Even if it is the one for the loaded condition) to check out my estimated numbers and find out where is the difference, please?
Thanks in advance.
Cheers.

 

Paulo,
On top of what Mikey has posted:
As per a quick estimative RMs at 90º are 3600 kgm for the Nordborg (better figure than the 4000kgm posted before) and 3500 kgm for the Faurby. Faurby's negative/positive GZ curve's areas ratio is around 0,19 and Nordborg's around 0,10. Also, max GZ happens at around 55º for the Faurby and descends from that on, but although happening at 50º for the Nordborg, it remains in high values for a bigger range of heel angles, due to the flatter upper end of the curve.
I find more seaworthy the Nordborg than the Faurby (from the point of view of stability).

 

If you really want to cross oceans, what European big production builders propose to you is a removable inner forestay. You don't say if it is the case (removable), but if it is not, that would make a genoa a very difficult sail to tack.

There is also another option and that is a special storm sail that you rig over the furled genoa, utilizing the spinnaker halyard.

 

Hey Mikey, about boats and seaworthiness, let me tell you the story of Diogo Botelho Pereira. He was a Portuguese, born in India around 1507, probably a product of miscegenation of Portuguese with beautiful native ladies. This guy was smart and brave; he learned maths, was a good sailor, a good pilot and a cartographer.

In 1533 he sailed to Portugal, to offer the king a world map made by him and asked him to be a captain of the Kingdom and to be Governor of a small Indian fortress (Chaul). The king said NO and later he found out that Diogo had said that, no matter the king decision’s, he would manage to be a Captain by his own means.

The King did not allow that kind of disrespect and arrester and deported poor Diogo back to India (Diu).

Well, Diogo was stubborn, and after having built by himself a small Fusta (a sailing boat) with 5.5m length and 2.4m beam, secretly set sail for Portugal in 1535. The Fortress of Diu was finished and he wanted to be the first one to tell the king the good news.

After making a scale in Azores, for water and fresh food, Diogo made it to Lisbon.

This time the King was impressed and after having ordered the small boat to be burned (he did not want to be known that it was possible to travel to India in such a small boat) he made Diogo a captain, making him first the Governor of S Tomé, a small Island on the equator and later the governor of Cananor, an Indian Fortress town, much bigger than Chaul. He stayed as Cananor Governor till his death..

So, an 18ft home made wooden sailboat, 500 years ago, was seaworthy enough to make it from India to Portugal, with a small detour to Azores and you think the Faurby 424 is barely fit for oceangoing travel ?

I know, Diogo has taken some chances, but remember he was not crazy, he was an expert, a excellent sailor and a prime navigator, and I am sure he knew a lot about boats and seaworthiness. If he had thought that he had not a decent chance to succeed he would not have tried.

As CT has pointed out, seaworthiness is a relative concept. Some will not put their feet on any boat smaller than a Cruising Ship, others have circumnavigated in 25ft light displacement boats with the family, including a small child.

For me, all the boats we are talking about are seaworthy enough to circumnavigate with an adequate safety margin, but I have nothing against other people’s criteria unless someone tries to impose their standards on me or tries to prove, against all evidence, that only certain types of boats are seaworthy, I mean heavy displacement, slow and narrow boats .

 

Try to change the downflooding angle that you have estimated. The downflooding agle on the Pogo is bigger than the AVS, so I believe you have to enter the AVS angle (127º).

 

Done, but it only reaches 38,910. In fact STIX does not grow over this figure for downflooding angles over 113º, due to FDF reaching its maximum value of 1,25 at that angle.
I'm really curious to analize the document you have....
Cheers.