Originally Posted by Bash
No. It's total horsefeathers. Brewster came up with the formula "tongue in cheek," by his own admission. An attempt to sell narrow boats.
People selling narrow boats will sometimes use the ratio to attempt to convince the uninitiated that their boats are superior to boats with greater beam. Another reason to ignore yacht brokers when they get into their spiel. These are people who spend their lives either poisoning the well or fouling the nest.
Check your BS meter for proper calibration. If someone starts telling you that Vessel A is superior to Vessel B because of its capsize ratio, your meter should be pegged to the brown end of the spectrum.
Of course you are right but what is really odd is that months after you have said that this thread goes on and on. You have said that on the 2th page of this thread that has now 5 pages
People just need to read what is said on the USA calculator:
All modern boats have bulbed keels and the tendency is for torpedo keels and more draft
even in cruising boats (look at the new Hanse 415). The CG is lowered this way, instead of using much more weight carried higher with obvious effects on the stability curve giving an higher AVS and a lower inverted stability.
If you want to access the static stability curve of a sailboat, instead of looking the something that only takes in account some factors completely dismissing others get a stability curve. Any boat builder
can get you one.
If you apply that formula to an Open 60, a very beamy boat, probably the safest and more seaworthy sailboat for its length with an huge stability the results would be:
and a note: May be vulnerable to capsize
These boats that are made to race
solo in conditions were the waves can go over 40ft (and they have got them in some cases) have the highest stability requirements among racing
boats and all these ones have higher stability requirements than cruising boats.
Regarding the stability requeirements of an Open 60, they have to be able to return from an inverted position in flat water
by their own means, have an AVS superior to 127.5º and have a area under the positive part of the stability curve 5 times bigger than the area under the negative part.
That means that in a case of inversion a wave 5 times smaller than the one that has managed to invert the boat can re-right it.
And if compared the positive part of the curve of these type of boats (considering only the GZ ) these boats have an huge positive stability if compared with the Contessa type. The max value for GZ is about 3 times bigger.
No wonder that the designers of modern cruising boats have taken for inspiration of the hull
the Open 60 type as reference and I am not talking only about performance cruisers like the Pogo 12.50 but abount mainstream cruisers like the Benetau Oceanis
, the Sense, the Hanse among others.