Understanding the Ratios

[Adelie]

Originally Posted by Don Lucas

When it comes to it if you are looking at an older design from the "ratio days" you would get better info by chasing down an owner of a given model and getting the real story.

Talking to owners is just a good way to get a lot of Buyer's remorse (negative responses) or Post-purchase rationalization (positive responses) which has more to do with the psychology of the owner rather than an objective assessment (sp?) of the merits of a vessel. You need outside observers to get good info on the relative merits of anything, especially something they have spent a huge amount of money on. While there are individuals who can objectively assess something they have a vested interest in, they are few and far between and pretty much impossible to identify.

Originally Posted by mitiempo

I don't think an offshore boat can be chosen strictly by the numbers, if at all. Many refer to D/L ratio as a measure of weight carrying ability for example. A larger boat with a smaller D/L ratio can carry the load a couple cruising may need as well or better than a smaller boat with a larger D/L ratio.

Originally Posted by mitiempo

I think the so called "offshore" design with its long keel, attached rudder, and D/L ratio over 300 went away a few decades ago - the Valiant 40 for example. Considered reasonably extreme in the 70's when she was designed but heavy compared to many newer designs. Fin keel and rudder on a skeg. Still a great boat to cruise in though. Or the Peterson 44/46.
Although larger, the Sundeer 60 has a D/L of about 82 and was designed as a couple cruiser. Many have circumnavigated and more have crossed oceans successfully. The Saga 43 is a great offshore cruiser with a D/L of 160 as is the Saga 35 with a D/L of 151. These all have spade rudders, thought to be too dangerous to take outside of the bay 40 years ago.
Times have changed and the boats have as well. A good offshore boat has to be well built but doesn't have to be a heavy, narrow full keeler with attached rudder and long overhangs any more.

Size of boat, the Sundeers being a classic example, make up for a lot of design shortcomings/compromises. It gives a lot more roll inertia which significantly increases the size of the wave needed to capsize the boat. Given the Gaussian distribution of wave sizes this DRASTICALLY reduces the likelihood of capsize. It increases the area for roll damping, which combined with the smaller proportionate sail area needed to propel the boat (an induce aerodynamic rolling), decreases dangerous rolling in waves near the natural frequency of the boat’s rolling. Size of boat also gives you greater load carrying capacity.
Good designers can make big boats reasonably safe, fast and keep the buyer happy with amenities. It takes a great designer to do so with a small boat.

I think 4 things are leading to the perception and reality that going offshore in a lighter boater is safer than it used to be:
A. Larger boats for the reasons discussed above.
B. Better rescue services that are easier to call using newer technology. Cruisers used to be completely on their own. Percentage-wise there are a lot less people just disappearing without a trace while cruising.
C. Better forecasting and dissemination of same has allowed people to do a better job of not going out into impending bad weather and to avoid the worst of it if they are already out.
D. Modern materials are stronger and more durable for the weight.

By far the most important of these is size of boat. Consider the question of whether there is a 30’ boat with a D/L of 82 that you would feel is safe enough to cross the Atlantic or Pacific in.

Originally Posted by barnakiel

Gotcha!

Originally Posted by barnakiel

You completely obliterated the human factor.
For gods' sake PLS read some on the Dashews' background then tell others which boat is good for offshore work.
Off course, an IMOCA is an excellent offshore boat. For Vincent Riou. Please note not all of us are anything like Vincent!
To other sailors, a boat that will accept less than celestial sailing skills is perhaps a better choice.
BTW Long overhangs were never, to my understanding, confirmed to add to seaworthiness of a boat.
Cheers,
b.

Long overhangs were a product of when handicapping rules for racing measured the at rest waterline. It was a rule beater, as the boat sped up and heeled, the actual waterline length increased.

Likewise the highly raked attached rudders, 40*-55* on older full keel boats was a rule beater from when the handicapping rules measured keel length.

I’m in the middle of reading Marchaj’s ‘Seaworthiness, the Forgotten Factor’, so I have all this trivia on tap.

Marchaj comments on how long overhangs and highly raked rudders have lived on long after the circumstances that led to their adoption.

[barnakiel]

Originally Posted by mitiempo

I don't recall suggesting an Open 60 is a good offshore boat.

But a Sundeer 60 is hardly a skittish racer. It is a well balanced couple oriented boat(...)

C'mon - you are trying to dodge the issue: is an IMOCA a good offshore boat or is it not?

And should a cruising boat fit the skills and abilities (or lack of thereof) of her crew or not?

b.

[Randyonr3]

Originally Posted by barnakiel

should a cruising boat fit the skills and abilities (or lack of thereof) of her crew or not?

b.

You just hit on a very inportant issue.. something I havent thought of in a long time.. Our Boat, in the wrong hands, could possibly be the worst handeling boat made..
When we origionally left Coos Bay with ours and headed south, I thought I made a 100k mistake as the boat was all over the place while we were trying to head dead down wind with the boat wing on wing.. like trying to stear a wet banana peal....
after as couple hours we decided to bring her around and drop the sails and motor for awhile..
Turned her off a few degrees and brought the boom over to the other side, she laid over about 12 degrees and took off like rocket and ran as stable as she was sitting on a set of tracks..
Found out that dead down wind in following seas is something our boat dose not respond to very well..
But you take her off a quarter and I'll put her up against any boat for stability and speed.. We'll almost any..

[mitiempo]

Originally Posted by barnakiel

C'mon - you are trying to dodge the issue: is an IMOCA a good offshore boat or is it not?

And should a cruising boat fit the skills and abilities (or lack of thereof) of her crew or not?

b.

I am not trying to dodge any issue. An Imoca is probably a good boat for its intended purpose - to race around the world with a skilled skipper on the edge most of the time. It isn't a yes or no answer. For the racer it is a good boat. Certainly not for a cruiser.

Of course a cruising boat should be matched to the abilities of its crew. The kind of cruising boats we have been discussing are not the kind of boat that demands the skills the Amoca does.

[Adelie]

Originally Posted by mitiempo

I am not trying to dodge any issue. An Imoca is probably a good boat for its intended purpose - to race around the world with a skilled skipper on the edge most of the time. It isn't a yes or no answer. For the racer it is a good boat. Certainly not for a cruiser.

Of course a cruising boat should be matched to the abilities of its crew. The kind of cruising boats we have been discussing are not the kind of boat that demands the skills the Amoca does.

OK, how about my question: Are there any 30' boats with D/L of 82 you would think appropriate for offshore?

[barnakiel]

Originally Posted by mitiempo

I am not trying to dodge any issue. An Imoca is probably a good boat for its intended purpose - to race around the world with a skilled skipper on the edge most of the time. It isn't a yes or no answer. For the racer it is a good boat. Certainly not for a cruiser.

Of course a cruising boat should be matched to the abilities of its crew. The kind of cruising boats we have been discussing are not the kind of boat that demands the skills the Amoca does.

Oh yes, you do! ;-)

This is how I see things:

"... for its intended purpose ..."- Are not all boats built for their intended purpose?

IMOCA is built for blue water, offshore sailing. It IS then: a blue-water, ocean-going craft. Full stop.

"... certainly not for a cruiser ..." - Right! They are somewhat lacking in furniture department. What about these boats:

www.oursonrapide.com

JP Dick's radical Verdier cruiser | The Daily Sail

MARTEN 65: Canting-Keel Cruiser by Owen Clarke

Let's face it: a Deerfoot in the 80'ies was what these boats are today!

Big hug,
barnie

[mitiempo]

Adelie

There are a few, but not many, at least over here. The Pogo 10.50 designed by Groupe Finot comes to mind with a D/L of 87. I don't think many North American designed/built boats would be, but in Europe there are many lighter faster boats that are very capable offshore.

[mitiempo]

barnakiel

Certainly all boats are built for their intended purpose. Most items are. But the intended purpose of the Amoca is not family cruising - offshore or otherwise.
There are sailors that want to push the envelope, often at great expense as with the Marten 65 which I have read about. Canting keels aren't on my ideal offshore boat because of both the added complication and price. The 6' draft fin on the Sundeer is fine thank you.
The Verdier designed JP54 is interesting, read about it last year. The Ourson Rapide 60 is interesting as well, but neither is as tame as a Sundeer 60 (or 56), which are production offshore cruisers designed to be easy to handle - by a couple, which has been proven by many. I didn't mention the Deerfoot, which were custom boats built before the Sundeer 60 which was both more refined and easier to handle. A 60' boat with a rig of the size found on many 50' boats is not all that hard to sail.

Maybe in 10 or 20 years we will see boats like the JP54 or Rapide in common use by offshore cruisers, but sailors are a pretty conservative group really - many still consider a full keel and heavy displacement as the only real "offshore cruiser".

[barnakiel]

Originally Posted by mitiempo

(...) Maybe in 10 or 20 years we will see boats like the JP54 or Rapide in common use by offshore cruisers, but sailors are a pretty conservative group really - many still consider a full keel and heavy displacement as the only real "offshore cruiser".

Maybe in 10 or 20 years we will see Sundeers in every marina too...

Cheers,
b.

[callmecrazy]

I had the impression the reason heavy, narrow, full keelers with heavy ballast were considered more 'seaworthy' than a boat with a wide beam and initial stability is because, they have a greater righting moment, and being narrow and tender, have a higher propensity to self right themselves from 180` knockdown.

It pretty much has nothing to do with how the boat sails.

[mitiempo]

The location of the ballast and the amount relative to the displacement has nothing to do with the boat having a fin or a full keel.

[callmecrazy]

it's an older design concept that predates fin keels, so if you're looking for a boat with the best capsize ratio, it's probably gonna be an older full keeled boat. Which also happens to be heavy because of older building practices... Ultimately people can find all sorts of good reasons those older boats are still considered 'seaworthy'.

I'm not advocating them...

[mitiempo]

barnakiel

Sundeer is one of several boats I had mentioned. It is also a boat I like. But there are other examples of the changes in offshore capable boats over the years. One of them is the Valiant 40, considered by many to be the first performance cruiser, compared to the Saga 43 from the same design board. The Saga has a longer waterline giving it a D/L of 160 vs the Valiant's of 256. Their displacement is actually fairly close. Sail area is larger on the Saga which is also slightly narrower.

Able's Apogee 50 is a great example of an offshore boat as well.

[mitiempo]

crazy

I disagree - many modern fin keel boats have capsize ratios as good or even better than many older designs.

Fin keels have been around a long time by the way. Here's a link to Arion designed and built in 1951 with not only a fin keel but a spade rudder. She is still afloat and built of fiberglass as well. damian mclaughlin corporation - Arethusa
And she certainly wasn't the first fin keel boat. Actually she has most of what I like in a boat - long waterline, narrow and the rudder aft where it does the most good.

Here's Arion's profile from Yachting Magazine:

[callmecrazy]

I'm not talking about keels. and also not making any argument for or against the ideas.

I'm just saying that was the general way of thinking back then, (that a seaworthy boat must be self righting). It's not about the ballast to displacement ratio, it's about the hull shape and self righting ability (which is part of ballast/displacement). It's also not about the keel shape. Although the depth of ballast is important.

There is no way to determine the self righting ability from ballast to displacement, or any other ratio, other than the capsize ratio.

Comparing ballast to displacement ratios gives you a good idea of how stiff it will sail against the wind (also taking the sail area to displacemnt ratio into consideration), but you have to know how the hull is shaped to determine how tender it will be in the water.

PS: This is direct answer to the OP, not anyone elses post. I'm talking about boats in the 30' range. So, self righting was/is more of a concern with smaller boats intended for 'bluewater' sailing.