Originally Posted by malbert73
I don't understand how you think beamy flat boats are more likely to self right than narrow boats. I must have misunderstood, right? The main way the volvo
or open ocean boats self right from inverted are when the keel cants, or with some waves and their 10+ foot heavily ballasted keels.
Do you see any keel canting?
Again what matters narrow or beamy is the position of the CG. A beamier boat with an equivalent B/D ratio, the same draft
and type of keel compared with a narrow boat will have more positive stability (it will need a bigger wave to capsized it) and will have also more negative stability (it will need a bigger wave to put it back on its feet).
Besides the energy needed to capsize
the boat another key factor is the proportion between the energy needed to capsize
the boat and the energy needed to re-right it, as well as the AVS. You can obtain that measuring the areas for positive and negative stability on a RM curve and making the proportion.
The proportions between the two areas has nothing to do with the boats being beamy or narrow but with the CG position. The same with the AVS.
Let's assume two boats with the same length, same weight, same B/D ratio same type of keel, same draft
, one narrow other beamier. Let's assume that the proportion between the negative and positive stability is similar. That should not be very far since they will have a similar CG. Let's assume that proportion is 3 to 1.
The beamier one will have more positive and negative stability, the narrow one less positive stability and less negative stability in about the same proportion. let's say that difference in stability (negative and positive) is of 50%.
Let's assume that the energy needed to capsize the narrower boat is the one of a breaking wave with 2m. That means that the boat would right itself up with a breaking wave of 0.66m, or with a normal non breaking bigger wave.
The wave energy needed to capsize the beamier boat will be bigger. It will correspond to the one of a wave 50% bigger, that means a 3m breaking wave and it will also need the energy of a bigger wave to right itself up, in this case a 1m breaking wave, or a correspondent bigger non breaking wave able to roll the boat till its AVS point.
What is the boat in you would want to be, the one that needs a 3m breaking wave to be capsized and 1m wave to be re-righted or on one that will need a 2m wave to be capsized and a 0.66m wave to be re-righted?
In the end there are boats better or worse designed in what regards final stability and one very important factor is the force the boat is making to re-right itself (proportional to its weight) after a 90º knock out, but beamier or narrow boats are not by itself more or less seaworthy even if in what regards smaller boats beam can be very important to give it an overall better positive stability.
Yes jim you are right this should be about build quality but it was not me that have said that the Sense 55 was a boat not suited for offshore
work, a marina boat.