Monday's Child >> Waffle^n (Re: Legend 356)

[Guest]

Monday\'s Child >> Waffle^n (Re: Legend 356)

From Ted Brewer: "CAPSIZE SCREENING FORMULA (CSF): Some years ago the technical committee of the Cruising Club of America following up from the Fastnet 79 disaster came up with a simple formula to determine if a boat had blue water capability. The CSF compares beam with displacement since excess beam contributes to capsize and heavy displacement reduces capsize vulnerability. The formula is the maximum beam divided by the cube root of the displacement in cubic feet; B/Displ.333. The displacement in cubic feet can be found by dividing the displacement in pounds by 64, of course.

The boat is acceptable if the result of the calculation is 2.0 or less but, of course, the lower the better. For example, a 12 meter yacht of 60,000 lbs displacement and 12 foot beam will have a CSF Number of 1.23, so would be considered very safe from capsize. A contemporary light displacement yacht, such as a Beneteau 311 (7716 lbs, 10'7" beam) has a CSF number of 2.14. Based on the formula, while a fine coastal cruiser, such a yacht may not be the best choice for ocean passages."

Now let's look at the Legend 356: Beam = 12'; Displacement = 13,900 lbs so the CRF = 1.99638 which equates in anyones language to 2.0.

The Legend 356 meets the CRF ...Just. And that's a might fine piece of design judgement.

I'd be willing to take a Hunter/Legend 356 across the Atlantic either single handed or with a crew of my choice to prove the point that published GZ curves are now nothing more than pretty pretties and are totally meaningless: Cat 'A' = Cat 'A' Period.

 

[lezgar]

Monday\'s Child >> Waffle^n (Re: Legend 356)

Your formula is not enough. You have forgotten the centre of gravity and bouyancy. Two boats can to have the same beam and displacement and with your formula the same number, but if their centre of gravity and bouyance are different one could be very safe and the other very dangerous.

 

[Guest]

So who buys a boat according to GZ curves?

I'll bet that most people who buy a boat either new or 2nd hand buy the boat because of what they see in the interior. I'll bet that over 99% of potential purchasers don't even both to walk the deck to see if the gear is substantial enough to suit the running rigging. I'll bet also that nobody every asks whether the deck is properly bonded to the hull and whether the chain plates are suitable for a simple circumnav.

Just how many people who buy boats actually sail? IMO, most people buy sailing boats as a weekend status symbol and when they put out, they put out under motor for a quick trip round the marina ... or if they are really adventurous, for a quick max 2 hour trip round the bay.

GZ curves and AVS are NOW as much use as a fart in a thunderstorm. We've now got the RCD and as it's the bible, all we need to know is whether it's Cat 'A' 'B' 'C' or 'D' - and of course everyone knows EXACTLY what those categories mean ...

 

[Bergman]

Re: So who buys a boat according to GZ curves?

Agree with you about boat buying criteria. Most people including me give great weight to interior - and why not, thats where you live.

But cannot share your faith in RCD rating. The Legend does not fit my mental picture of an ocean cruising boat - but of course I could easily be wrong.

The point is that there are so many variables that no single item of information can tell the full story. Least of all a simple categorisation. Compared with the directive for small commercial craft the RCD seems to ignore how the boat is fitted out - no requirement for epirb, SSB, duplicate liferaft etc.

Just as a thought if you buy on basis of RCD and boat capsizes do you have a claim for liability against builder, or against EU (or anyone else).

Personally I doubt it - which perhaps demonstrates what this rating is worth.



<P ID="edit"><FONT SIZE=-1>Edited by bergman on Mon Feb 25 19:50:48 2002 (server time).</FONT></P>

 

[kidnapped]

Re: So who buys a boat according to GZ curves?

Let's think Latterly .... Are all these measurement carried out when the yacht is 'as launched' ... little/no fuel/water? Is the design waterlenghth based on same criteria? or does it allow for loading factor?
If there is a design 'cargo capacity' what is it? Weigh your own loading ... with /without fuel water ... then subtract leaving spare 'cargo'. Can this spare be put on the keel ... bulb either side of fin ... to increase stability. Extra ballast could be taken off if load factor increases due to cruising gear etc.

 

[webcraft]

Re: So who buys a boat according to GZ curves?

Steady on, Nigel . . . you seem to be saying that 99% of people who buy yachts are people who don't intend to sail or don't know enough about it to even give the boat a basic check over before purchase . . . . not a very flattering picture.

I'd put the figure at maybe 50%, still too high, but I do actually come across other yachts on my travels sometimes which are more than an hour from a marina. Please don't tar everyone with the same brush.

I think this correspondence - now running to over 100 messages in 4 separate threads - shows that there are a lot of people around who DO question the RCD classification and who DO believe that stability curves can tell us something about the suitability of a boat for various purposes and conditions.

- Nick

 

[Bergman]

Re: So who buys a boat according to GZ curves?

Well
Err
Yes
But I'm not sure where this leads

Weight of fuel, water etc applies to all boats so if you compare one with another then comparison is valid.

Sure loading the boat to full cruising trim will affect the curve, may change AVS by a degree or 2. Though if properly loaded with heavy stuff low down should not have too much effect.

No-one is saying curve is full story.

Surely the more information that is available the better decision one is able to make. Seems to be the case in most other things. No-one tries to group cars into 4 categories. Makers deluge you with info - power, torque dimensions etc etc. Millions of people seem to be capable of buying cars without the sort of debate we have here.

Don't really see your problem

 

[Guest]

Re: So who buys a boat according to GZ curves?

I have driven between 40000 and 60000 miles a year for the last thirteen years, only twice have I taken my cars to their limits. Once I got everything back and once I had a large accident. I thought long and hard before I bought my boat and take it to it's limit regulaly. That is how I like to sail. If you sail out into the Solent in a two or three for two hours these figures mean nothing (and the interior is more important). If you get a buzz from taking on the elements they are worth checking. My next boat will take me at least a year to find and will be able to take whatever conditions I aim it at!
EACH TO HIS OWN.
ALLAN

 

[Twister_Ken]

Re: So who buys a boat according to GZ curves?

Nigel, you're a naughty lad, straying over here where there are innocents abroad.

Love your formula, BTW. I come out at 1.525. What about your lugger?

 

[Eudorajab]

Monday\'s Child >> Waffle^n (Re: Legend 356)

Couldnt agree more. Id even take a Benny !!

 

[bedouin]

Monday\'s Child >> Waffle^n (Re: Legend 356)

Totally agree. By that logic anyone venturing out into the Irish sea in a Cat 'C' boat (e.g. Contessa 26) must be certifiably insane - but then we knew that anyway

 

[kingfisher]

Yep, liable

It's part of the checks and balances of the New Approach (CE-marking in EUspeak): the fact that the manufacturer can classify his boat on his, is offset by the increased liability under the Product Liability Directive.

Problem is same as with car vs bike accidents: even if I have right of way on my bike, I'm not going to go head-to-head with the car to prove a point.

Besides: capsizes are usually a combination skipper error-design fault.

But if a class A capsizes in a weather pattern within the RCD limits, the manufacturer could be held liable.

Obi-Wan
http://sirocco31.tripod.com

 

[Guest]

Don\'t bank on it

The RCD category should make it harder to sue the builder, not easier.

The RCD category is a classification awarded by the authorities, not by the builder. A builder would have been liable under the pre-existing law if he had held his product out to be suitable for a purpose that it was not fit for. Now he will have the perfect defence because he can say that it was the authorities who classified the boat as suitable for offshore use, not him.

Of course he could still be liable if there was a fault in the construction or design that caused an accident and the fault hadn't been evaluted as part of the RCD categorisation eg. if he hadn't bolted the keel on properly. But the RCD categorisation system should in many cases make it considerably harder to sue him.

eg.: Boat capsizes in mid-ocean with loss of life. Victim's representatives complain that the AVS of the boat was 95 degrees making it patently unsuitable for offshore use. You may have got compensation before the RCD directive, but he has the perfect defence that the boat is rated Category A and the can say that the RCD directive only requires AVS of 95 degrees. End of case.

 

[Bergman]

Re: Yes. But

How will you know it will take anything you aim it at?

 

[PeteMcK]

More than a couple of degrees

More like a degree or 30.