Seaworthiness

I agree that it needs additional stability compared to the ocean-going characteristics we are discussing in this thread but this is not quite the place for that post.

Can you move it to the power boats forum please, someone will pick it up and answer there

The Pogo 40 would have pretty good ocean going characteristics compared to that

Mikey

 

I guess seaworthiness is relative after all...

 

Maybe the pics aren't showing the true value of the boat

Pacific proa's don't look sea worthy, still they have transported people safely between islands in the pacific for a thousand years. No science there, just hands on experience

Mikey

 

Excuse me, but that's your assumption, not my words. May I remember you what is the kind of boat I would like to own, if I could? : http://www.efesyat.com.tr/project.html

I think you are very daring acusing me and Mike of ignoring evidence. I would appreciate if you could agree that we are not absolutely stupid and have some idea of what we are talking about. But (in my opinion, of course), you do not seem to me to have a lot of knowledge on these matters and because of that I think you even contradict yourself.

May I remember you the STIX number, as an example? As you know it has been based on a thoroughful research of yachts with desirable and undesirable characteristics, by a group of highly knowledgeable professionals, and it clearly penalizes excesive beam and lows AVSs for cruising boats. You were very fond of the STIX number and strongly defended its validity in these forums (and not only) not that long ago. Now, in a matter of a couple of months you seem to have radically changed your point of view. I think you contradict yourself quite easily. And I'm afraid this is only because you really do not know in deepness of what are you talking about, and post only inspired in an 'spirit of contradiction', even mistifying other people's words if necessary, with whoever doesn't agree with your too easily changing points of view.

But, of course, I may be wrong and soberb, and maybe you know much more than I do on these matters.

Cheers.

 

Randy, I've drawn a rough curve (by hand) with those data and your boat seems to have a very high initial GM (so pretty stiff) and quite a lot of inverted stability with also very high angles at the 160-180º range, this giving the boat a high tendency to remain inverted if capsized. Am I wrong?

Cheers.

 

I don't think you can argue like that.
Viking ships traveled across the atlantic etc. etc.
That doesn't mean they where very safe.
100 years ago drowning was the most common death for Norwegians, I suppose, several hundreds each year. Why? They where fishing in small open boats.

 

The myth of ancient Polynesian sailors is also worth popping.
Migration waves were a one way voyage/ritual depopulation.
Making a landfall and populating/depopulating it was a fine chance, and successive migrations carried the rulers will with them.
No one was expected to come back and give a report from 'paradise'.

Yes yes off topic, be gentle...

 

I don't know of any stories that state the boat has stayed inverted. The boat is not designed as an open water boat, yet it have numbers better than many ocean racers.

In 1997, the data for the IMS racing fleet shows that LPS of 118deg is higher than average with the majority of boats ranging from 112 to 116deg.

Almost 2/3rd's of the boats have +/- ratios of less than 3.0 (1800), 750 boats between 3-3.99, 390 boats between 4-4.99, and less than 200 with ratios over 5.0

At 118deg and 2.892 +/- ratio, my boat is better than the majority of the 1997 IMS fleet.

Some more data points:
25deg = 1.178 arm
60deg = 1.777 arm
90deg = 1.168 arm
120deg = -0.105arm
150deg = -1.104 arm
165deg = =1.043 arm

Compared to the requirements for an Open 60, the vast majority of offshore racers are prone to capsize and long inversion. (Based on the LPS and +/- ratios). Yet inverted Open60 examples are easy to find compared to inverted IMS boats.

The impression is that Open60's invert regularly, while IMS boats rarely do.

 

Yes, you are right about that. Multihulls resist better to capsize because they are really beamy boats and can laterally slide on the wave, instead of tripping on the keel. But I will prefer a mono with very good resistance to capsize but also capable to recover from a capsize in a reasonable period of time. I would say a boat with a minimum 120º AVS,.

 

Hum, can you give me a single example (with the actual safety requirements)?. I don’t think you can.

The rules (that I have posted) are recent. They have increased substantially the safety of those boats. Old Open 60's even modified with more ballast on the bulb, have a lot of trouble passing the safety tests. On the “Velux 5 Ocean race” there was at least a boat excluded because it didn't pass the stability tests (an American racer), and as you know there were very few entries on that race.

These boats are safer than IMS boats (racing). Put am IMS 60ft going at 28k with 60k of wind and they will be on trouble (you can only compare the stability of the boats at the same speed. Both boats sailed at cruising speed would be very safe boats) .

The problem with these boats, as with the Volvo70 has to do with strength and scantlings in what refers the canting keel. If they lose the keel isn’t much to be done, but that is not a problem of boat design, but of adequate scantlings and good engineering. Lots of progress there, but a lot to be learned yet.

 

Vega,
Multis trip on their beam halfway through an inversion just like a beamy mono.
Sliding sideways doesnt help a multi (or a beamy mono) on a 45 deg wave face with the force of a wave travelling horizontally.

Like you, I personally prefer a self righting mono.
From the multi perspective it may be nit picking regarding AVS, but I place importance on the negative side, inversion stability.
Very bad things happen there.
Initial stability in the positive side can create long inversion times, and negative righting moments should be minimised in the negative range.

High initial stability is great for performance, but can bite your arse if you go upside down.

 

About the Multis I disagree with you. Tank testing had shown that they are much more difficult to capsize than monos, and that is because they have a bigger positive stability and can slide sideways in a wave. The problem with the Multis is the wind, or the wind with waves. A cruising multi with its sails down is a very safe boat. Capsizes with cruising Multis can happen when they are sailing under apparent normal circumstances and are hit by some freak and huge gust of wind (and that happens very, very rarely).

About the High initial stability, it can happen as you say, but it is not a rule, there are some very fast cruiser-racers, like the Swan 45 that have a huge initial stability with a small inverted stability and a good AVS. You have to look at each case. Bulbed keels make a lot of difference in what regards fast boats with high initial stability, relatively high AVS and relatively small inverted stability. For relatively I mean that they can have a better stability curve than many good cruising boats, normally considered more seaworthy.

 

Not only.
Under combined wind and waves, a catamaran may be vulnerable, because when sailing the heaving action of the wave on the windward hull imparts rolling momentum to the boat, reducing the energy reserve left under the righting moment curve. If the boat has a low static stability for the type, and is being sailed close to the limit, with the daggerboard down, it will be possible to capsize it in waves in a wind speed that would be safe in flat waters (quoting here John Shuttleworth). Multihulls seaworthiness depends, as for any other boat, on type and design (among other considerations).

 

Vega
I pledged to leave the poor old multis alone in a previous post, so Ill bite my tongue. They have a place in the sun, just not in this thread.

Bulb keels...aaaarrrrrrrghhh....
Just as long as the damn things are stuck on properly

One of my particular pet hates is self righting monos with detachable keels.
Oxymoronic.

Apart from your casual mention of bulb keels aaaarrrrrrrghhh and poor old multihulls I agree with you.

But excessive beam is bad.

:?: By the way, what rights your inverted beamy boat Vega? Most boats seem to have inverted stability to greater and lesser extents.
Something must tip them over again.

 

Yes I agree, I have said the same thing: