Originally Posted by HVVega
I found this article a few months ago about yacht stability over the past 50 years. Might explain a bit of why people want bigger boats these days.
Yacht stability article
That book is over 20 years old
He is talking about the boats from the 50's and 60's versus the boats from the 80's.
He is talking about static stability. Posterior test tanks had shown the relative importance of static stability versus dynamic stability. Regarding dynamic stability huge advances where made in the last 20 years. Only that explains that in the last decade, from the many hundreds of very light mini-racers (22ft solo sailed) that crossed the Atlantic racing, there are almost no recorded capsizes. Last year, a modified mini-racer circumnavigated no stop, without any major problems.
Regarding static stability he is saying what I was saying in a previous post. What happens is this:
The positive GZ curve (arm) of modern boats is much better than the one from the older boats. The values are considerably higher, but as it is said on the article, the area that counts for the energy needed to capsize a boat is the one behind the positive part of the RM curve (moments). The Rm curve is obtained multiplying each value of GZ by the mass of the boat. As the mass of older boats is much bigger (for the same length), the RM curve is bigger.
That's why I have said that compared to an older boat, you would need a bigger new one to have the same static stability.
But the weight of the boat is a much better indicator of the cost of a boat, so, for the same price you will have two boats with the same weight, an older type (smaller) and a new design (bigger). As the GZ is better on modern boats, the modern boat will have a slightly better positive stability.
Bottom line, for the same price, generally a modern design will be a better sailing boat than an older design, on speed and also on positive stability, not to mention dynamic stability, were big improvements were made.
Off course, there will be always exceptions, not on sailing performance (modern boats are always better) but on seaworthiness. Old boats tend to be made as all around boats while modern ones tend to be more specialized. Most of them can do offshore passages but in most cases you have to equip them for the job. The ones that are specifically designed for offshore work are relatively rare and that reflects the market and the sailors needs: Who needs a boat specifically designed for a type of sailing that is seldom or never made by most sailors? That would make that boat a worse coastal cruiser and a significantly more expensive boat. And that lead us to the object of this thread