I am not 100% certain that Paulo and I are in agreement on all of this, in fact I am certain we are not, but that is okay. Through discussion I would expect that we will end up perhaps a little closer in our views. This is my understanding of some of the issues being discussed above. ….
Ok, lets see what we can do about this
While these Open Class based designs have demonstrated an enviable record as race boats, and may even be a reasonable basis for coastal cruisers, I personally prefer more moderately narrow beam boats for distance cruising containing significant amounts of offshore use. ….
Me to, but this has to do with personal taste and nothing to do with the suitability of those designs (based on Open boats) for offshore use in what regards seaworthiness.
Most boats based on Open boats are not fast light boats and the ones that are light are for more frugal cruisers than me, or are richer and have money for a bigger boat
Cruising in fast performance boats of this type imply to live in a very frugal way due to the light load capacity and to the simple interior. For living with the same comfort and carrying load of a more traditional cruiser you will need a bigger boat, and that costs more money.
But aside that, Open boats were design not only for offshore use but for solo offshore use. They are very forgiving boats and very safe boats.
I have already show to you that a 40 class racer has a better stability curve than a Vaillant 40, in what regards AVS and in the proportion between the energy needed to capsize the boat and the energy needed to re-right the boat when inverted, or putting in another way, in the proportion of the size of the wave capable to capsize the boat compared with the size of the wave that will re-right the boat. These boats can be not only easy but very seaworthy.
But of course, in what regards cruising boats based on these designs each case is a case and as in any other sailboat it is better to have a good look at the stability curve. That is not different than with any other sailboat, beamy or not. I know of some good narrow boats with a stability curve not as good as some of these boats in what regards AVS and in the proportion between the positive and negative part of the curve, not to mention the righting force at 90º.
As a word about my personal opinion in these discussions, and in an effort to provide a filter which would help provide a fair minded sense of where my personal prejudices tend, when it comes to offshore cruising boats, I am not a fan of the Open Class style boats that Paulo likes. They are clearly faster than more moderate designs, but that speed comes at a price in terms of motion comfort and self-righting. ….
Regarding this some confusion and some disagreement
As I have said before many times for my personal use as a cruiser I prefer more classical boats and not boats derived from Open boats. If I could chose a cruising boat I would chose a XP 38 that is not a beamy boat neither a boat based on Open boats.
That does not mean that I don’t like Open class boats as I like many other types of boats. I can appreciate and understand their advantages and weaknesses and I have posted already about it.
The disagreement :
I don’t consider that boats based in Open class style boats are faster than other modern boats based on more traditional rule like IRC or ORC. Actually only downwind in very heavy conditions a racing Class 40 will be more fast than a racer like a Ker 40. Even in what regards fast performance cruising boats a ker 39 will beat any fast cruising boat derived from the Open classes, the same way a Volvo60 will beat an Open 60.
So what is the advantage?: The easiness of use. You need a crew and a good one to race a ker 40 (or a Volvo), the boat is very nervous and need a constant trim especially downwind while an Open boat is designed to go downwind on autopilot. Upwind, the Ker 40 will slam less and will be more faster but it will be a more nervous boat with less form stability and a less stable platform.
It will be more easy and safe to leave the boat on autopilot and go forward in a class 40 then in a ker 40 type of boat (more narrow and with a huge ballast/displacement ratio).
The ease of use is the main reason that motivates the designers to base their cruising boats on the type of hulls of the Open boats. After all most cruising boats are sailed solo or with the little help of a wife that is not normally much
, so what better model could they have than the type of hull of a boat that is designed just to be sailed offshore solo and have been improved through the years?
And I don’t mean only performance cruisers like the Pogo, but almost all modern designs by all the main Na and main boatbuilders: Beneteau (Sense and Oceanis), Hanse, Jeanneau, Bavaria, Dufour, just to name a few.
I agree that advantages (not the speed) comes with a price in what regards motion comfort upwind with waves but I completely disagree in what regards a lesser ability to self-righting.
That it will depend on each boat but as a rule I don’t think that is true. Generally the AVS of these boats is not lower than the previous boats from the same brand with a narrower hull, but the overall stability is bigger.
Putting in another words, the wave energy needed to capsize these boats is bigger than on previous less beamy models and the proportion between the wave capable of capsizing the boat and the wave capable or re-righting is about the same. As an important bonus these boats have more RM at 90º.
How was this possible? Look at the keels and the drafts. The B/D ratio is about the same but now almost all the keels have more draft and more weight on the bulb, some fast cruising boats have fin torpedo keels and their number is increasing.
You pointed to me once a Claughton paper that related capsizing resistance with beam and that is logical in fact. A wide cat is much more difficult to capsize (with no sails) that any monohull with the same size. So these boats have advantages in what regards positive stability and also in what regards dynamic stability : their keels have much less area than the previous ones and that and beam will make these boats harder to trip on the keel and will make them more able to dissipate the wave energy with any other movement than not a rolling one.
There is a good reason for all main boat builders and main yacht designers going on this direction. I still prefer a boat with better tracking ability upwind and with a better motion in waves upwind, but understand the reasons that makes most sailors prefer other type of boats. Many don't sail much upwind or with waves
As I have explained elsewhere I think these boats based on Open boats make a lot of sense if you will sail extensively upwind and want a forgiving boat that don't heel much. These boats will be very adequate for voyaging with the trade winds that is the way most of the cruisers sail when crossing oceans.
About the rest, I will try to reply in another day, with more time.