Seaworthiness

[DGreenwood]

Guillermo
Certainly this will drive a revival of IMS and does not necessarily mean that your safety is going by the way. In fact I suspect this will drive a general improvement in the fleet safety specs...even by your strict standards.

Why does it seem such a reduction in standards to you?
Why dos this get your goat? (another silly American term)
Lightweight and speed are codependent. Racing is the reason for ORC to exist. If safety standards are required by racing rules, then they will carry over to the production yachts.
I just don't get why you think that changing the rule so that older slower boats can't take the prize from faster (and possibly safer) boats is such a travesty?

I just can't grasp what seems to be a rule being proposed here that weight=safety. Huh?

[Raggi_Thor]

There is no need for sarcasm and a language we wouldn't aloud at home.

I think it's too simple to say
Heavy = Slow and safe
Light = Fast and dangerous

For example, (some) heavy displacement boats have less wetted surface relative to their weight and sail area, so they are fster in light winds.
Some light boats have excellent righting moment and are strongly built and will not sink.

And as usual, excuse my spelling.

[masalai]

I am inclined to see your point Raggi, some production yachts seem to be driven by competition to cut costs ergo quality or integrity of construction or other sacrifices to get the sales & thereby stay in the market.

My views come from anecdotal sources & observation but serve to invoke a feeling for a trend.

[DGreenwood]

Originally Posted by Raggi_Thor

I think it's too simple to say
Heavy = Slow and safe
Light = Fast and dangerous
.

I agree! In fact I know experienced sailors who would say that heavy=slow and dangerous...but I would not go so far as to say that.

I would say that the assumption that light boats cannot actually be safe, or safer, is far from correct.

[MikeJohns]

Originally Posted by Guillermo

Yes DG, all of us learn. But what cannot be done is to believe we are 'top guns' as soon as we learn a couple of things, and then do not listen and even refute what more knowledgeable people are saying, without having enough basis. That's what is annoying.
Cheers.

I agree with this.

If there is a large body of research observation and prediction that shows problems with certain types of vessels it is more sensible to acknowledge that you accept the risk/benefit tradeoff rather than denying the risks. To go further as some people do and continually throw mud at more traditional designs that have been shown over time to be very able both in performance and safety seems to be the hallmark of the devout-believer.

As for the desire to learn: Anyone truly wanting to learn would enter a meaningful discourse both acknowledging their faults and availing themselves of a wealth of literature on naval architecture and hydrodynamics. It appears that the more vocal advocates of designs with inherent flaws do not avail themselves of this opportunity but appeal to popular culture as the basis for their “truth”. Belief systems and popular culture can continually change but the underlying established sciences of Naval Architecture and Marine Engineering do not and for very good reason. To label professionals as staid conservatives opposed to technological change because they question the strength, stability and comfort of some modern designs is not sensible.

I understand very well why Guillermo gets frustrated with some posters style. In my opinion some posters can get overly passionate and have a tendency to overlook, willfully ignore or misinterpret any evidence to the contrary of their current viewpoint. If you work and are qualified in this field and somebody says something that is questionable then it should lead to an educational discourse, the stance of the believer against all odds tends to be frustrating, especially if you have covered the material before with the same poster.


To everyone

Remember this forum is visited, archived and linked to search engines. If questionable statements are made they should be questioned in turn. But lets question the content of peoples posts rather than their character.

[MikeJohns]

Originally Posted by Raggi_Thor

There is no need for sarcasm and a language we wouldn't aloud at home.

I think it's too simple to say
Heavy = Slow and safe
Light = Fast and dangerous

For example, (some) heavy displacement boats have less wetted surface relative to their weight and sail area, so they are fster in light winds.
Some light boats have excellent righting moment and are strongly built and will not sink.

And as usual, excuse my spelling.

Absolutely

[Raggi_Thor]

And it's allow(ed), I meant, probably
Good night to all you down under,
six hours to work now.

[Man Overboard]

It might be more instructive to take a look at the seaworthiness/performance issue from a more empirical angle. I personally am looking for solid answers that can predict the behavior of both heavy and light displacement boats, as well as the effects of beam in relation to performance and sea kindliness / seaworthiness. The ‘what about this boat, what about that boat’ debate that is constantly going back and forth proves very little; unless backed by data, mathematical proof, scientific study, formulas or at least some sort of verifiable quantitative observation.

For instance, take these two comments by Ragnar and Mike; opinions that were glossed over that deserve more attention, each having an effect on seaworthiness.

Ragnar

For example, (some) heavy displacement boats have less wetted surface relative to their weight and sail area, so they are faster in light winds.

This would be a good topic for discussion, Mike touches on the subject in his statement a few posts back, and ties in the importance of displacement-length ratio and prismatic coefficient.

Mike Johns

Umm ..... actually a displacement hull is a displacement hull whether there are two of them or one, the cat gets its superior performance (sometimes) because we can optimise the hulls wrt wave making. That is the hulls are long and narrow. we dont have to add beam to give a better form stability, and long narrow hulls are superior displacement forms.
A lot of cats are absolute dogs because of issues poorly understood by the designer despite a high form stability and light displacement.

So long as we are talking displacement hulls and as I explained before; the performance does not depend on the displacement but on the shape (Cp) and the ratios and the GZ curve.

I would add Mike, that it would also be useful to consider the midship coefficient which in essence along with Cp constitutes the block coefficient. Water plane coefficient should not be ignored either along with a whole host of other formulas, which I believe you alluded to in the last sentence of your quote.

Consider for a moment Ragnars comment about wetted surface and heavy displacement boats (some). What are the implications of a heavy boat optimized for low wetted surface area?

We know that a sphere has the least surface area per unit volume of any shape; not too many boats made in the shape of a sphere. But an egg shape is very similar, and related to the sphere. The closer the hull resembles an egg, the more optimized for low wetted surface the hull will be.

There is a problem with pure egg shaped hulls though. An egg shape provides no form stability; which means that all stability must come from weight, more importantly, weight optimally placed (low Cg) which of course adds to wetted surface. Weight based stability taxes performance heavily; it is only 100 percent useful just before your mast hits the water. At 20 degrees of heal, your righting arm is only 34 percent effective. If you are a racer, you may view this as 66 percent to much lead; if you are a family out for a cruse you may view this as 66 percent reserve. If it were as easy as picking which group you were in there wouldn’t be a 60 page debate going on here. The fact of the matter is there aren’t any pure egg shaped boats (maybe submarines) Sailboats with egg shaped bottoms have substantial freeboard. So as soon as the boat starts to heal, which it must, the wetted surface increases anyway do to the changing water plane coefficient, and not in an efficient manner. It is really not possible to have a sailboat that does not have some amount of form stability. It makes since to optimize for form stability, and to balance that with ballast. As soon as we start to squash our egg shaped boat and widen it, adding beam, it only makes since to remove ballast. For every mono hull, there is an optimum beam to ballast ratio. (Righting arm ratio) And for every size/type boat there is an optimum displacement range.

Until we can quantify how some of these issues affect those who sail these vessels, I don’t think we can get a grasp on what is truly seaworthy. We need more facts about what design criteria is most critical to seaworthy boats. For example, we know that a crew that faces high accelerations fatigues faster, and makes more mistakes than a crew in the same conditions that are spared the high accelerations. I find it hard to believe that there is no data or studies on fatigue factor due to accelerations at sea. It would not be hard to mathematically calculate the minimum length and maximum beam for any given sea condition to achieve a satisfactory comfort level.

Lets try to focus on more facts and less hearsay.

[masalai]

As a rank amateur, but keen observer who likes to gather knowledge, I think the size of the task is going to keep any resolution out of reach.

There are far too many variables to assign values & integrating formulae to reach any acceptable consensus amongst the participants (we who participate in this thread).

How about 6 categories of sailing weather/sailing purpose: Inshore cruising ,inshore daysailing, inshore racing, offshore (ocean crossing in weather opportunities) both racing & cruising, Out to sea for long passages in any weather that comes up. I think that is 6

Then set about to identify: heavy or light, mono - cat - tri That makes 6 categories that covers as many styles of boat as possible without going nuts with sub categories

That is about 36 sets of design criteria for fun sailing (as opposed to sailing for profit where I assume the operator is thinking of the paying punter coming again next year).

That way the lightweight boys will not be shitting on the heavy protagonists etc. etc..

[MikeJohns]

Originally Posted by Man Overboard

..............................

Lets try to focus on more facts and less hearsay.

Tom
In these sorts of exchanges you get one simple clear shot to get your message across . The less complicated the better


Anyway here is some factual data from existing vessels in a seaway for you to consider, Cp and it's attendant angle of entry are the most important cofficients, and (in line with the current debate) displacement is a red herring. ( Yes and the midship coeff. )

cheers

[DGreenwood]

Mike
Do you have a pic or drawing of the Silver Searcher? Something seems wrong with those specs?

[MikeJohns]

DG
I'll look for something if I get time. The synopsis you will find in a number of NA texts. This one is in John Teale's basic NA . Anyway you can run the figures through an auto hull generation and then VPP and see what the software thinks. ( Are you an NA ? Do you have the time , I don't but it would be interesting)

More importantly I was actually expecting someone to point out that if you held all other factors constant and changed D that resistance would increase, which it will. But then that leads to something else................

Hopefully the message is that we should not generalize about displacement and performance (in displacement boats), and that performance will be co-dependent on several other factors. Statements like "It's light so its fast or "it's heavy so it's slow" are not overly well informed (IMHO).

Catsketcher
You deleted your post?
If you want good reserve strength in a lightweight then expect to pay just as much for exotic materials as a heavy stiff boat. Then if well designed and engineered they will be easily driven strong vessels . The compromises for the passage-maker that I see are; load carrying ability and its effect on performance and comfort in a seaway (higher vertical accelerations). It's just which compromises you accept and being honest about them.

My experience is that when you are at sea you wish for a different boat with each shift in the weather. The more experience you gain on passages the more weight you learn to assign to particular characteristics that suit your style. Our personal choice should not lead to denial of the detriments or advantages inherent in any design.

[Man Overboard]

I was actually expecting someone to point out that if you held all other factors constant and changed D that resistance would increase, which it will. But then that leads to something else

Although this is true, I am not sure that is what is being reflected by the data in the example boats. I too looked for info on the Silver Searcher; I could not find any, I have quite a few NA books, haven’t looked through all of them. I did find some additional info on some of the other yachts that were mentioned. I don’t have John Teale's book. The length beam and ½ angle of entrance is similar to Dashew’s Sundeer although I believe Sundeers displacement is about half of Silver Searcher.

[DGreenwood]

Mike
I am not an NA. I am a builder that has been stuck with the job of correcting enough of others F-ups, that I have learned a few things. I only wish that I had the cash to buy toys like VPP.
I do have a lot of sea miles and have been lucky enough to have tried literally hundreds of boats. Only part of these in a real seaway, and only a very small portion of those in trying conditions. Having survived a couple of very ugly situations on very different hulls has made me keenly interested in approaches to comfort and safety at sea.
I was hoping (for a very long time now) to hear some empirical, rather than experiential, information on this subject from this thread. There certainly has been some provided, but it is so mixed in with bickering I can't tell when someone is just making stuff up to win an argument.

Why is it, the music has to stop because one guy misses a note or is not as good a musician? Flinging insults and mining up a persons past mistakes are fruitless effort...better spent making sure that one has not become a little too invested in ones own dogma.
There are experienced seamen here, from all types of boats---there are architects---there are engineers---there are geeks and welders and woodworkers. Why can't there just be a freakin' discussion without all the posing and snorting and pushing. Jeezus!

Rant over.I won't bring it up again. Now back to the topic

MikeJohns My experience is that when you are at sea you wish for a different boat with each shift in the weather. The more experience you gain on passages the more weight you learn to assign to particular characteristics that suit your style. Our personal choice should not lead to denial of the detriments or advantages inherent in any design.

That really says it! At this point the question becomes;
How do you quantify those characteristics so that any average guy off the street (remember those guys---the ones that feed us?) can make a reasonable and safe decision about what suits his style or what is within his skill level. (without resorting to regulating bodies) STIX alone doesn't do it for me.There is so much more to a "seaworthy" boat than it can provide.
I help people choose boats and equipment for themselves all the time, and frankly, most of them buy based on...I don't know what???

[masalai]

From this uninvited interloper, it seems that your sales/marketing hat & strongly supported by your experience gained expertise assisted by a large degree in psychology are what's needed.

Ask the customer to describe what is his and her dream vision of a perfect sojurn on their new boat. How long could they stay on board on a passage. What would be the worst scenario they could handle. Have they had similar experiences etc..

Keep the questions away from statistics & numbers to get a true feel for the punters dreams. If it seems obvious that it will be a marina bound gin palace - Jackpot sell "luxury" and a marina berth. Otherwise use your hard earned knowledge to analyse and advise on appropriate options to consider with these strengths & these drawbacks.

You know which you find likely to suit the needs as you have stated reasonable experience levels from which to make an assessment. That is the only way I can think of to evaluate the variables in this question.

Most "assets" parked in marina pens seem to represent the owners "manhood and economic status" Too many production manufacturers seem to be selling "luxury" Ostrich skin covering furniture (lounge chairs) highly polished wood-vineer finishes everywhere, flat screen TV and so on.

No mention of fuel capacity, load limit, additional safety gear (beyond standard legal requirements to register the boat) buoyancy rating, sea keeping/kindleness, diesel engine maintenance schedule, fire extinguishers etc.etc..