Seaworthiness

Cool. As I mentioned several times, I wish my mathemetics was good enough to have let me do NA. I was not trying to say that I was better qualified/educated etc - all I was trying to say that I know, as a member of a profession often criticised and very much deserving of criticism, that professions can get it wrong or be open to other viewpoints.

I shall move out of the thread with a couple of final comments.

1- You said that you would like to talk numbers - but isn't the discussion of numbers based on an enormous number of considerations? How do you specify the number of the "correct" LPS without considering what effect that may have on cost, performance, or other factors?

2- One number that says a lot to me is that the number of deaths caused by inversion of light boats is small, compared to other causes of death.

3- Dollars or Euros are also expressed in numbers. As Mike said, light boats can be cheaper. People normally have limited funds. If they have to buy a more expensive boat, they have to get the cash from somewhere. They may have to work harder and therefore get less exercise, creating health risks. They may have to work for longer before they can go cruising, creating health risks and handling difficulties. They may have to drive a cheaper, older car with inferior crash protection. Given the risk of road accidents and the low risk of inversion injuries prevented by heavier displacement, it is probably statistically bad for your health to spend $20,000 of your available funds on a boat with a heavier displacement - that $20,000 would probably be much better spent on a safer car or other health-improving areas.

This factor is very real in my experience, but it seems to be always ignored by the "heavy is good" brigade. If we don't allow for factors such as costs we may as well legislate for every boat to have a 10,000 ton rescue tug following it across oceans in case something goes wrong.

4- There are some very interesting studies on "revenge effects" of legislating to improve safety, including areas such as bike helmets. The numbers in these indicate that you have to take lots of factors into account when trying to legislate, or you can create as many problems as you solve. If we legislate for expensive boats, we will probably end up with a cruising population largely consisting of older people who have spent their lives making money, not sailing. Whether we are better off with the oceans full of 70 year old tyros on "safe" expensive boats, or 45 year old "old salts" on cheaper boats, is hard to solve with numbers but surely such matters must be considered in a thread considering safety.


To me, looking at mere numbers of DLR or LPS without considering these other numbers does not tell the whole story. But it's your thread so I shall move on.

Happy sailing.

 

Paulo
I am very glad and I am sorry I misunderstood you.

Please don’t take offence , the following is necessarily personal in replying to this.

I can quote to you the names of many prominent Naval Architects/Engineers, Yacht designers, Riggers, Magazine editors, scientists and sailors who do agree with the view I espouse but disagree with some of the views that you have posted. Does this amount to conclusive argument ? I think a researched scientific view should prevail over the view of popular culture.

You have not availed yourself of the possibility of detailed discussion but have skipped to conclusions based on your beliefs rather than that which you can argue from a factual basis. Your attempt to alienate the established science of boat behavior with your beliefs is an example. When science disagrees with what you think is it to be discarded?

Your appeals are often indirect appeals to a 3rd party such as “Far would not be designing unseaworthy boats since he is a Naval Architect”. But you don’t quote Far himself saying his boats are seaworthy, do you understand what I am saying?

Perhaps we could re-visit some of the issues, if you could agree that you may have been wrong in some of your comments, it will change much of the argument you have used in the past.

There has been too much effort already to try and convince you that popular culture cannot replace the science of Marine Engineering no matter how vociferously or prolifically you appeal to those arguments they remain contrary to established and accepted material.

As an Engineer of course I argue from the principles that I have learnt and apply, principles that are accepted as definitive and are not open to dismissal by popular opinion.

Hopefully your views may have changed a bit over the course of this thread?

I thought the point was made well enough that reports are not collated worldwide by any agency sufficient for these sorts of claim. I doubt any researcher would consider this proof by any means. We would need someone to collate all accidents and analyse them accordingly it is called research.

But beam is a detrimental factor so we can say that beam compromises seaworthiness.

As for the open 60; Seaworthy for what? As a cruising design it has many problems as you say yourself:

Do not presume that the same hullform will be as “seaworthy” when scaled down, this is a trap when designers use their open 60 success to promote smaller look- alikes. Each vessel needs assessing on its own merits and the advantages of a 60 footer are not necessarily applicable to a 40 footer, but marketers would like you to think so.

As an example of your logic for supporting the Pogo40 types we could use one of your arguments: and I’ll repeat myself again.

Can you agree that the argument that racing boats in an open class will converge on the most seaworthy hullform is not correct?
They converge on a compromise between seaworthiness and speed. With a strong bias towards a faster boat than is competititive. Past experience suggests that in order to be competitive you accept a high level of risk. The Southern ocean has pointed this out often enough. The Mini’s also show the trend of speed vs seaworthiness tradeoff.

 

You are wrong on this.

There is a whole branch of methematics, called statistics and probability that will mathematically PROOVE you that for analysing trends in a set, you do not have to analyse the WHOLE set to have accurate results.

 

You still have incomplete data If you do not have mandatory reporting of all accidents not just fatalities but all potential fatalities that would have perished had they not been picked up.

Secondly your ocean cruisers are going away, who then relays back this data to your central body so the stats are significant enough ? By the very nature of your territorial waters all the reporting is going to be coastal. Who reports on the French boat in Vanuatu ?

Without a central research body collating data you are going to draw your data from various incomplete scources which makes it valueless. For exampe our own rescue statistics here in Australia are state by state unless the central body is involved. Police records are not very complete and seldom identify anything other than the vessel general type and the owner.

We did talk about this earlier.

 

Data presented in a conference (15/4/2005) by P. Miller (D.Eng. P.E., Professor of Naval Architrture at the United States Naval Academy):

“Question :

What percentage of recreational marine accidents are related to Design, construction or equipment?

Answer: 11% of the accidents,
89% of the marine accidents are related with owner and operator mistakes.

Statistical source :1998 USCG boating statistics."

Mike, it looks that only you don’t rely on statistical marine data, in what regards boat accidents evaluation.

 

Paulo.

The first thing to consider would be whether there has been time to see the effect of extreme hull-forms in the cruising market, but I think the statistics are meaningless in this case I presume this data includes every floating object under command that required assistance from the USCG and is not useful unless properly presented.

If there is no collated data for cruising boats as a separate entity, a illuminating example might be offshore racing boats. In this class I would suggest that those figures would be at the minimum reversed.

This is why I keep saying that conclusions cannot be drawn from incomplete data. Yet people continue to dish up statistical arguments that are superficial.

Once again the data is dominated by coastal events. Consider that the coastal cruiser in developed countries is very well supported, can get help from a variety of sources and is well supplied with shelter and detailed weather forecasting. This is not the same for the mid ocean yacht, or a yacht cruising in remote areas.

We may not be seeing many extreme Pogo40 type boats cruising anyway, I suspect for reasons outlined before that they are just too unsuitable for long distance cruising without becoming dangerously loaded or miserably spartan. They possess very few suitable characteristics for long term cruising. Given this fact they are going to be very unlikely to appear in cruising boat statistics anyway (were we able to actually collate some).

 

Guillermo
I think sometimes people are content to let a representitive of a view debate the point.

I am guilty of chasing the off topic posts, sometimes it is the only way to proceed without acquiescing.

I think other Engineers/NA's are content to remain aloof rather than suffer the rudeness of some posters venting their anger when and if we defend views contrary to a lot of modern popular culture.

It would have been far better were we able to have a more professional discussion rather than running a general education campaign.

I have do some work, it is too easy to spend an hour here

 

Did you mean to say,"The other posters are not professional and I think they are not educated enough to understand the subject"?

If that is not what you meant, you might want to rephrase.

If that is what you meant you have insulted members of the forum.

Randy

 

Randy

Perhaps a poor choice of adjective.

Generally there is a professional approach to mans endeavors and there is an unprofessional approach. Nothing to do with the level of education of the participants. For example we say bussiness is conducted in a professional manner.

On this forum some discussions are conducted in a very professional manner others are emotive and passionate. Unfortuantely when they become emotive no concensus can be reached if parties will concede no error and refuse to be drawn on past statements or admit to past errors . This approach is unprofessional and prevents a logical progression.

I was commiserating with Guillermo with the thread not going as he had planned. Perhaps Mea Culpa.

IMHO
cheers

 

Thanks for that Mike.

I was scanning through this thread the other day and I think I remember that you said something to the effect that seaworthiness could be measurably improved by small changes to a design. That is a very interesting comment, I'm surprised that no one has asked what changes they might be.

How about you and Guillermo choosing a few examples and pointing out what changes you would make?

Are these things of the sort that would allow a layman could to make a valid comparison of seaworthiness between two or more boats?

The requirements that Open 60's must meet that Paulo has posted seem to be reasonable to me. I know the GZ curve of my boat has a ratio of positive area to negative area of only 2.892. Based only on this, can we conclude that my boat is less seaworthy than an Open 60 with a ratio of over 5.0?

What should change on the boat with 2.892 to increase the number, or is 2.892 high enough?

Happy Friday!

Randy

 

Woops! Can you post the curve, Randy?

Not at all, Mike.
I like your technically supported and explanatory posts, with which I can't agree more. And I appreciate your remarkable efforts trying to make clear yourself once and once again.

But this is not without the same appreciation I have for the other posters defending contrary positions, even if I disagree with them (I just do not appreciate pontificating attitudes without enough scientific support). Many have posted very interesting information I did'nt know. And that's most useful for me.

Anyhow I have to recognize I'm somewhat dissapointed with the very few NAs and yacht designers entering these discussions on the several stability related threads. I have some experience on sailing boats, having raced and cruised several types of them, but not that much in their design (as my professional activity is rather oriented to professional vessels). So I strongly would like to learn from experienced designers, who have designed many different types of boats through the years and have lots of feedbacks from their clients. You say maybe they want to keep aloof of the rudeness of some postings, but I've seen several of them actively collaborating in other threads. Then....?

All the best.

 

Whoops is right ... what I have is the Righting Arm curve.

Positive from 0-118 with a max of ~1.8 ft @ ~55 deg

118-180 is Negative with a max of ~1.2 ft @ ~155 deg

+ Area 135 deg ft
- Area 47 deg ft

+Area/-Area = 2.892

I have no scanner but I could try to post a digital image ...

 

Well, it looks that you don’t only have to “educate” the ignorants of this forum, but the vast majority of boat designers that actually design oceangoing sailboats.

That “mission” is surprising because, as it seems clear to me, neither you or Guillermo are oceangoing sailboat designers and it seems evident, that the NAs that are specialized in doing so, have an accumulated experience that will give them an incomparable superior experience and knowledge on the subject.

I really don’t understand what gives you the knowledge and ability to teach them how to do seaworthy ocean sailboats. It seems that it should be exactly the opposite.

You could claim that your particular view is based on a superior sailing experience, but that is not true. Many of modern NAs are also more experienced sailors than you and have sailed all kind of boats. Some of the “ignorants” that have opposed your marginal views on seaworthiness are very experienced sailors with sailing ocean experience with all kinds of boats, a much bigger experience than yours.

I have nothing against heavy boats. Contrary to what you have suggested, I have experience with heavy boats and their motion. I have owned one for almost a decade and I have learned much of my seamanship with a Flemish friend, sailing (many times) in heavy weather in a heavy steel 60ft.

Fact is that for many years I have thought like you (about boats and seaworthiness) and the boats I favored were heavy long keelers, like Cabo Ricos, Island Packets or Vancouvers.

I have changed my opinion, not on the seaworthiness of those boats, (narrow heavy boats with long keels), but I believe now that it is not the only way to achieve a satisfactory seaworthiness. Those heavy boats, if well designed, are seaworthy, but there are other types of boats, not necessarily heavy that, if well designed are also seaworthy.

I have changed my opinion based on statistic data and on the different ways the best modern NAs solved the problem, and understanding how they got their seaworthiness from their boats.

I can if you want (It is obvious to me that all respectable NAs would refuse to Design an Oceangoing cruising boat that they wouldn’t consider seaworthy).

This is how Farr Group present themselves. See what they say about the cruising boats they design:

"Founded by Bruce Farr and Russell Bowler in 1981 as Bruce Farr & Associates, the present-day Farr Yacht Design (FYD) has grown to a design team comprised of 17 members providing an enormous range of talent and skills.

Farr designers are also leaders in developing fast, comfortable custom and production cruising yachts. Their well thought out concepts in cruising designs satisfy owners with .. kind handling characteristics in all conditions, with safe, well engineered hulls and superior performance.

With backgrounds in sailing fostered as youths and honed in affiliated professions from drafting, design, boat building and sail making to race rule management, computer science and engineering, the designers at FYD all share a superior and comprehensive understanding of boat design, construction and performance.

To supplement in-house experience and knowledge, the design group benefits from on-going research and development carried out at leading wind tunnel and tank testing facilities. Top industry consultants, specialists in their fields, are also retained regularly to assist in delving deeper into specific areas.

… They have designed over 400 different yachts …

Each design created by FYD benefits from knowledge gained through top level research."

http://www.farrdesign.com/profile.html

But we can find better examples that show up to what level modern boat designers consider their oceangoing designs seaworthy ( designs that are contrary to what you call “ Naval Science “).The boat that Jean Marie Finot has designed for his own personal use, an oceangoing sailboat (the Cigale), goes against all notions you have of what a seaworthy boat is, but it is clear that he wouldn’t design an unseaworthy boat for himself.

It is evident that he does not agree with your rather restricted view of boat seaworthiness.

He says about that boat:

“Ce bateau a été conçu par des architectes pour leur propre usage. Il est la synthèse de leurs expériences de navigation et de construction de plus de vingt cinq mille bateaux de croisière et de course”.
Sécurité, robustesse, facilité de manoeuvre, vitesse et agrément de vie à bord, sont les caractères principaux qui nous guident »

A translation :

« This boat was designed by the Architects for their own use. The design is the result of their sailing and their building experiences of more than 25 000 cruising and racing boats.

Safety, strength, maneuvering easiness, speed and quality of life aboard were the principal directives that have guided us in this design”.

Jean Marie Finot is one of the most prominent modern sail boat designs.

He says about is Group (that includes Philipe Conq):

"About 30 000 racing and cruising sailboats built in France, Italy, Japan, the United States, Canada, Netherlands, Turkey, Brazil
Reliable experience
-Permanent concept of the innovation
-Passion for the art and the elegance
-Love of the sea, of the wind and of the speed
-Intransigence on the solidity and the safety. "

If you have any doubts about the prominent role they have played and still play in the Design evolution of modern sailboats, I will recommend you these two articles:

"Leading the Design evolution", by James Boyd, Published in the February 2000 edition of Yachting World Magazine.
“Groupe Finot” by Steve Callahan, published on the May 2000 edition of “Professional Boat Builder”.

The evaluation Groupe Finot makes of the Pogo 40 (one of their designs), strongly contrasts with yours, but of course they know the boat and you don’t, I mean stability data, Stix, AVS, scantlings and so on.

Groupe Finot about the Pogo40:

“For the Structures shipyard, we designed the Pogo 40 in the new spirit of offshore boats that are going back to the essence of sailing.
It is meant for those who want open sea, long journeys or transatlantic racing.”

http://www.finot.com/bateaux/batproduction/structures/pogo12/pogo40_ang.htm


But it is not only Jean Marie Finot and Philipe Conq that say that the 40class type of boats (like the POGO) are oceangoing seaworthy boats and also good oceangoing cruising boats. See what two other prominent NAs (Owen and Clarke) say about the 40class boat they have designed:

“Designed for true offshore competitive performance but also as a dual role yacht in which the family can take off cruising, rolling off fast effortless miles to those holiday destinations. The characteristics of a solo race boat will make her a reliable and steady short handed fast cruiser, with the foot released a little of the accelerator and a cold beer released from the ice box! “

http://www.owenclarkedesign.com/default.asp?m=da&id=11194

Regarding seaworthiness, I have nothing against your particular choice of boat, but I have to say that I have something against the particular arrogance that you and Guillermo insist, against all evidence, on that choice (narrow, heavy, full keel boats with a S/D inferior to 16) as the only acceptable choice on seaworthiness.

When you call ignorant to all who don’t share your idiosyncratic idea of boat seaworthiness, you are calling Farr, Finot, Owen or Clarke ignorant. They clearly don’t share your views on the subject and three of them even say that the 40class boats (like the POGO) are oceangoing seaworthy boats and boats fit for cruising.

I don’t know about the other forum members who don’t share your opinion and therefore are ignorant, but in what I am concerned, I feel a lot better to be on the side of the Ignorant, like Farr, Finot and the others. I even would be very worried if it was otherwise. Look at the difference in qualifications, to produce a relevant opinion on sailboat design and seaworthiness, I mean, between you and them.

Fact is that your choice of criteria for having seaworthy boats is today a very marginal one, considering all the different trends that modern and significant NA have chosen to produce seaworthy oceangoing sailboats, and an almost inexistent one in the boat production market.

I also find that putting all Seaworthiness emphasis on Capsizing and recovering from capsizing, forgetting all other factors, is not the right way to look at the subject.

The better or worst ability to recover from a capsize is an important factor, but by no means inferior to the better or worst ability to RESIST to a capsize.

Regards

 

Minimising self righting ability.

Get a multihull.

 

i think this is a slickcraft ss 160

if anyone knows more about it or could tell me the year it would be great. its 16ft. with a what i think is a 55 horse outboard merc. seems all original. boat needs definate upholstery work. this boat sea worthy? i know little about boats. if anyone could give me a number they think it might be worth ill put it up for sale. im thinking 1200 bucks.