DSK wrote:

Also, be prepared to explain why _your_ explanation disagrees with the
explanation of the professional naval architects who devised this measure.

MC wrote:
Oh but it does. It is closely related to the definition of the
metacentric radius. Do you know what that is?


No but I know several different ways of calculating, and few methods of
approximating with less rigorous measurements, metacentric height. If you
calculate metacentric height for a series of all angles through 180, you would
get a sort of radius. And it is a very very different thing from the capsize
screen. Let's make sure we're talking about the same thing...

Well that explasins everything. The metacentric radius is really basic
naval architecture -look it up and then you'll understand the most
common capsize screen formula -which is not what you've posted below.


CSR==(Beam / Disp ) ^ 0.333

with a lower result being more desirable when comparing similar vessels. Ring
any bells?


Yes, but you got the equation wrong. LOL The correct equation is
directly proprtional to the metacentric radius (the formula of which I
gave you before and which defines the initial stability) with the
assumption that the boat is quite slab sided (tumblehome is small). The
idea of the screen was to try to give a simple estimate (from numbers
that most people have readily to hand) of how stable the boat might be
upside down with the assumption that the water plane lateral moment
would not be very different from that expected from just the beam and
typical prismatics and sections. Empirical tests showed that this
assumption was reasonable for a rough and ready estimate -but only as a
guide. It's not an estimate acceptable here for offshore certificates.
In fact, if one were to follow the logic of this formula there would be
almost no difference between the initial stability inverted and the
right way up as it does not take any account of the VCG or coach roof.
For example, it predicts some inverted stability for a vessel with a 180
lps -e.g. a life boat -and that's clearly wrong! That anyone would
seriously use this formular in trying to decide seaworthiness is a most
unwise practice -naval architects don't!

OK?


Cheers