Seaworthiness

Vega, I think most of us agree that STIX is currently is the best tool available to assess stability of a sailing boat. Most of us would also agree that STIX is a compromise that does not take all factors in consideration.

Maybe the best way of illustrating that is that Pogo 40 has a much higher STIX than the Norborg.

Guillermo, I would agree with you that not including delta in a seaworthiness assessment is a valid path to go - As seaworthiness mainly should be assessed as a "pre-event". "Post-event" is of course also important when it comes to sailing boats but it should be secondary to "pre-event", IMO.

Mikey

 

This thread has shattered any confidence I had in boat deigners.

It would appear that should any one designer build a boat the other designers will shake there head in disgust and say "no no no" Thats not the way.

You have convinced me never to buy a new designed boat and I shall continue to buy boats from there reputation.

International boat shows will seem different to me fom now on.

 

Originally posted by Mikey
"Guillermo, I would agree with you that not including delta in a seaworthiness assessment is a valid path to go - As seaworthiness mainly should be assessed as a "pre-event". "Post-event" is of course also important when it comes to sailing boats but it should be secondary to "pre-event", IMO."

I don't think that eliminating "pre-event” and "post-event" circumstances is a proper methodology for evaluating seaworthiness. As Guillermo has pointed out, it has merit when comparing two boats, to evaluate other parameters, but the fact that the Pogo 40 has watertight compartments is a significant safety feature that can not go overlooked. It is indeed in keeping with safety features already implemented in the open 60 class boats, and is an example of how safety features that compliment a more extreme design can, and should go hand in hand. Just less than a month ago Mr. Greenwood out of New York has made the following comment:

Originally posted by DGreenwood:
Imagine a cruiser having to meet the buoyancy rules for example (water tight bulkheads). That right there would make them way too expensive.

Source, post # 29:
http://www.boatdesign.net/forums/showthread.php?t=15206&page=2

and now here we have an example of just that.

May I also call your attention to the fact that a boat rolling over is partly pre-event, and partially post-event; yet we don’t discount the post-event inversion as trite. No, indeed we attribute a greater necessity for the boat to self right. So if there is some other catastrophic event, say downloading, or a breach in the hull, I would think that not sinking should rank pretty high up on the seaworthiness scale; especially since it is one of the big complaints of the multihull proponents.

It might be advisable to consider the Pogo 40 as a transitional boat that bridges the gap between coastal cruising boats, and offshore cruising boats. A vessel that is great for coastal cruising, but yet one doesn’t have to fear for their life if they decide to make a passage once in a while… just a thought.

 

Tom and Mikey,
Answers at the STIX thread.
Cheers.

 

Hi Jack, what's up? Don't you agree with evaluating seaworthiness post-event?

Mikey

 

Hi Mikey,--well you know its a bit worrying seeing all you clever guys tossing ideas back and forth not agreeing with each other. I have bought new boats in my life and its possible that I shall buy another.

But if I do Mickey it will be with different approach than before I saw all this.

I was kinda relying you guys knowing what you were doing.

From the man in the streets point of veiw this is frightening stuff. Who is right and who is wrong maybe some of you is right and some of you is wrong and may be all of you is--well you know the rest.

There does not seem to be any evaluating its going nowhere, on and on. NO-- agreements on seemingly anything.

 

Jack, yacht design has always been and will always continue to be a compromise - regardless of how much science moves forward. That is just about the only factor that will NOT change

Buying a boat based on its reputation sounds like a very good idea to me

Mikey

 

Yes Mikey when we are talking about where the head is who cares really that much,-- but you guys are talking about the dangerous stuff--Seaworthiness-- If you clever guys cant agree on what it should be, how do I know who is right. Or if any of you is right.

The point is none of you seem to agree about anything, and that scary.

So is that the end of the thread? the conclusion! , Buy a boat on its reputation? and never mind the stix stuff?

I doubt it very much!!

 

Jack,

They are disagreeing as good engineers should.

To me, it seems like you have just lost your "virginity" when it comes to believing NA's as authorities that have _the_ answer. THere are many answers, many ways to acheive seaworthyness.

It's the same with a house, there are many ways to acheive as little heatloss as possible. there is no _best_ way, but there are many good ways.

In a house, you can use even more insulation, you can reduce the percentage of the windows, use quadrouple-glazed windows, have windows with special gasses, minimize "cold bridges"(don't know what they're called in english), use certain colours on the roofs and outer walls, use speciel heat-regenerators (don't know what they're called either), and make the house smaller, so the heat of the people living there means more. Heck, you can even change the shape, make it a dome, and it'll be more efficient.

All those things are parameters you can adjust. Give me ten engineers, and you will have ten different opinions on how those parametres should be adjusted. And you, as a buyer, will propably have your own opinion too. Do you want to live in a dome? How much of a percentage do you want the windows to have? The colour should be? How large should it be?

Where will your compromise land?

 

Jack,
I think NAs and Engineers around here more or less agree, each one with his own view of things, as it is normal. Interestingly the bigger (and more radical) difference in opinions seems to me to be between the (kind of) group of NAs/Engineers on one side and the (kind of) group of boat-owners/amateurs/would-be-NAs (this said with all respect) on the other. Not bad if debate is creative and respetuous, which many times (not always) has been. Please realize I do not pre-judge which group is right.

And buying a boat on its reputation has never been (and never will be) a bad recipe....

Cheers.

 

I thank you for your explanation, but a house will not roll over and drown you.

Its ok --not a problem please forgive me for my interuption of your argument which I dont understand any way. I wanted to let you know that I am a little surprised at this thread. It will, and has changed my veiws of designers who I thought were sooo smart and could build a boat and all the other designers would say "oh great job" and pat him on the back. Mmm dont think so, not now.

For instance I have never asked who designed a boat, never knew ,did'nt care. But now I might just ask and do some research. I would never have done that before.

I always assumed that when I bought a factory boat it had perfectly matched ballast with sail area etc etc. Now I will be not so sure, and skeptical of what I am told.

You know just stuff like this, Its all different now.

 

Jack, I'm a layman, just like you, so it's not "my" argument as such.

I do know that a house doesn't roll over and drown you, so to speak, but it's the same approach none the less. I could have mentioned how to make a house safe from fires, for that matter, but since I know rather much more about insulation, that was my example.

As always, reputation is not a bad indicator at all.

 

I would add to "group of boat-owners/amateurs/would-be-NAs" Finot, Lombard, Farr, Dix, and many others that design boats for offshore use. There are a great number of designers that don't seem to think that there is a problem with seaworthiness. The fact their boats don't meet your definition of seaworthy only proves that "seaworthiness" is not well defined.

When the Pogo's STIX was posted as being higher than boats of the type you favor, you decide to remove one of the factors that make up the STIX number and ignore it to show the Pogo in a different light. This only shows that we all find ways to rate boats so the ones we like (subjectively) turn out the best by the objective measures we choose.

It was assumed that beamy boats are less seaworthy, yet when the beam of the Pogo 40 was compared to other boats of equal LWL, the Pogo is not very much wider.

It was assumed that the Pogo's stability curve would show that it was likely to have long inversion times. Yet it's 6:1 ratio of positive area to negative area is better than 90% of the boats raced offshore.

Unlike most of the "seaworthy" cruisers the "group of NAs/Engineers" favour, the Pogo is unsinkable.

That leaves what?

That the "group of NAs/Engineers" that are posting here don't like the Pogo is obvious. Proving in any objective way that the boat is not seaworthy has proven to be a problem.

What I have learned is that there is no one objective measure of seaworthiness. All the objective measurements are very valuable to compare a few similar boats. They don't do so well comparing dissimilar boats. This must drive engineers crazy. It leads them to modify formulas to suit the desired outcome ... i.e. ignoring unsinkability so the Pogo does look so good.

Like each person's definition of beauty probably gives a good idea of what their partner looks likes, their definition of seaworthy (and how to measure it) comes from the boats they like. Guilllermo and the "group of NAs/Engineers" that post here will always be able to find some measure by which they can call their dislike of the Pogo rational, after all engineers and scientists think of themselves as rational people. They may be able to convince themselves, but they have not been able to make a convincing case to the group of boat-owners/amateurs/would-be-NAs, Finot, Lombard, Farr, Dix, et al.

Every time new forms are introduced, there are naysayers and well qualified engineers that predict doom and gloom. History has proved them right sometimes and wrong many times. One of the reasons is that marine engineers started from boats that were built with little science and great practical knowledge born of experience working with the boat building material of the day (wood). From the forms that worked with wood, rules and science were created, mainly in order to reduce the number of bad boats that got built. When the design is freed from the constraints of wood and cargo capacity, the old rules don't work so well. A boat does not need a D/L of 200 or 300 to have sound scantlings. Boats that have D/L well under 200 are not limited to the speeds of the traditional hulls. Greater speeds and lighter boats with the same strength and cargo carrying capacity can make use of different hull shapes. It is certainly possible to build a near zero maintenance boat using GRP using the same shapes and weights as 100 year old wooden boats, but what's the point?

If the position is that you don't want a boat that makes use of years of experience and refined methods to reduce weight and increase sailing performance, fine ... say so. If you don't think a modern boat like the Pogo can sail oceans and use her speed to avoid being in survival conditions, you need to spend some time looking at the available resources that make such passage planning possible. If you are talking about a boat that must sail a route on schedule in any season, you are not talking about cruising pleasure craft, you should be talking to a doctor to have your sanity checked.

There are people that buy cars that they think are safe based on their "crash protection" rating. They don't think about steering, suspension, brakes and driver ability that might avoid the crash in the first place. I think the conservative engineers here are doing the same with boats. The idea of pre-event and post-event stability factors as a reason to exclude "unsinkable" from the formula is a sign of this sort of thinking. I say that the capsize is a post-event. Boats don't capsize on their own, they capsize when they are operated in conditions and in a manner that might capsize them. The "pre-event" could be taking a boat that could not avoid extreme conditions to sea not knowing the forecast. The "pre-event" might be making a passage in a slow boat and not having the ability or knowledge to update your course based on changing weather conditions.

As Paulo has pointed out on more than one occasion, the energy required to capsize the Pogo is much higher than for many so-called "seaworthy" cruisers. That means in the same conditions that would be threatening to the "seaworthy" boat, the Pogo is far from being rolled. Add to that, the Pogo's ability to cover miles and the chance of sailing in those conditions is further reduced. This should be no great surprise, unlike the "seaworthy" cruiser, the Pogo was designed to race in those conditions, not heave to and pray ... and after it all the Pogo will be floating.

As far as buying a boat on it's reputation, it is hard to do much better than Finot and the Pogo 40. They both enjoy a very good reputation.

 

Jack, I welcome you to the discussion, as an ocean cruising sailor your input is invaluable. I ask you to put on your “common sense hat” and comment on my view on this;

There is now (in the EU) a mandatory standard that assesses stability and seaworthiness. It is called STIX. It is not yet world-wide but in time, it will be. Many potential buyers will use this tool as a measurement of how safe a boat is. The higher the number, the safer the boat.

STIX adds 5 to the STIX – the “how safe a boat is number” – if it is unsinkable, that would give say the boat that you are looking at buying 41.3 – because it gets a hidden bonus of 5 because it is unsinkable. The “how safe a boat is number” would have been 36.3 had it not been unsinkable.

Two of the main business rules I work with every day are "keep things simple" and "don't spread important information around". The simpler, the clearer, the closer together important information is, the easier it is to pass on the whole message.

Now, it is possible to assess stability and seaworthiness – how safe a boat is – as pre-event or post-event. As a potential buyer assessing how safe your next boat is, would you like to see pre-event or post-event as the primary piece of information? Which piece of information should be high-lighted? Or should maybe only pre-event, or post-event for that matter, be displayed?

I find pre-event more important and would like to see the “how safe a boat is number” as 36.3U. The U is more than enough to communicate to the guy up-side-down that - OK, it won't sink anyway

Jack, if you were Joe Blog, the boat buyer how would you like to see this very important information communicated?

Mikey

 

If "common sense" equates STIX with how safe the boat is, it become common nonsense.

STIX is a STability IndeX, stability is not the only thing that makes a boat "safe".

There are far more situations where a boat might be in danger of sinking than will find it in danger of capsize or downflooding. If you use "common sense" in rating the overall safety of a boat Unsinkability should far outweigh resistance to capsize.

STIX is only one part of what makes a boat "safe".

Real common sense tells us that NO boat is "safe". No matter what the STIX number might be. As soon as you can divorce yourself from the idea that a small boat can be made "safe", you can begin to see how any narrow-minded focus on one aspect of design will lead to false conclusions.

The only people that would support a "U" suffix are those that wish to ignore how un-safe boats that sink are.