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...

CSR==(Beam / Disp ) ^ 0.333

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

Fresh Breezes- Doug King

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

.... Ring
any bells?



MC wrote:
Yes, but you got the equation wrong.

No, that's the right equation. I see the problem... you don't know WTF
you're talking about.

The correct equation is
directly proprtional to the metacentric radius

Instead of blabbing about the metacentric radius, how about looking at a
well known and widely used formula, and taking the time to understand it?

But no, you'd rather babble, that way you can continue to feel smart.

.. That anyone would
seriously use this formular in trying to decide seaworthiness is a most
unwise practice -naval architects don't!

In the absence of more detailed measurements, it's better than nothing.
And it is a useful measure when comparing vessels of similar size and form.

BTW the CSR is not used anywhere I know of for an offshore rating
certificate, but it is occasionally used as a screen for allowing
vessels to enter a particular race.

DSK

dougies, the capsize ratio is widely discredited as a predictor of anything but
being the capsize ratio. You can find some pretty horrible boats with ratio's
as low as 1.75 and far better boats with 1.95+.

the capsize ratio takes too little into consideration to be much more than a
quite guide.

.... Ring
any bells?



MC wrote:
Yes, but you got the equation wrong.

No, that's the right equation. I see the problem... you don't know WTF
you're talking about.

The correct equation is
directly proprtional to the metacentric radius

Instead of blabbing about the metacentric radius, how about looking at a
well known and widely used formula, and taking the time to understand it?

But no, you'd rather babble, that way you can continue to feel smart.

.. That anyone would
seriously use this formular in trying to decide seaworthiness is a most
unwise practice -naval architects don't!

In the absence of more detailed measurements, it's better than nothing.
And it is a useful measure when comparing vessels of similar size and form.

BTW the CSR is not used anywhere I know of for an offshore rating
certificate, but it is occasionally used as a screen for allowing
vessels to enter a particular race.

DSK

JAXAshby wrote:

dougies, the capsize ratio is widely discredited as a predictor of anything but
being the capsize ratio.

"Discredited"? By whom? Please explain... as of the fall of 2003, there
were a number of offshore races around here that required a certain CSR
for certain classes.


... You can find some pretty horrible boats with ratio's
as low as 1.75 and far better boats with 1.95+.

Well, that's very true given the wide lattitude in defining "horrible"
and "better."


the capsize ratio takes too little into consideration to be much more than a
quite guide.

Kind of like your posts, huh?

DSK

... You can find some pretty horrible boats with ratio's
as low as 1.75 and far better boats with 1.95+.

Well, that's very true given the wide lattitude in defining "horrible"
and "better."

I'm afraid he's correct. Quite a bit of junk out there with good capsize
ratings. And quite a few nice boats on the margin or outside of it.

RB

JAXAshby wrote:

dougies, the capsize ratio is widely discredited as a predictor of anything
but
being the capsize ratio.

"Discredited"? By whom?

everyone, dougies, but you.

Please explain... as of the fall of 2003, there
were a number of offshore races around here that required a certain CSR
for certain classes.

and some races won't allow a Westsail 32 in (too small) but will allow a Hunter
33 (big enough). idiots abound, dougies.


... You can find some pretty horrible boats with ratio's
as low as 1.75 and far better boats with 1.95+.

Well, that's very true given the wide lattitude in defining "horrible"
and "better."

many truly horrible Hunter boats have c/r below 2.00, even down to about 1.75
IIRC.

Any, dougies, should you have taken care to learn what capsize ratio is ou
would have learned that is is nothing but the ratio of the displacement to beam
times some unnatural acts. It says not a thing about where that displacement
is in relation to the buoyancy. It is the kind of thing that makes a
non-too-good sailor like a Cabo Rico 38 look good in the telling.



the capsize ratio takes too little into consideration to be much more than
a
quite guide.

Kind of like your posts, huh?

DSK

many truly horrible Hunter boats have c/r below 2.00, even down to about 1.75
IIRC.

And don't forget the well respected J Boats which off have a bad ratio rating.

RB

DSK wrote:

JAXAshby wrote:

dougies, the capsize ratio is widely discredited as a predictor of
anything but
being the capsize ratio.


"Discredited"? By whom? Please explain... as of the fall of 2003, there
were a number of offshore races around here that required a certain CSR
for certain classes.


Really? Such as?

Cheers

"Discredited"? By whom? Please explain... as of the fall of 2003,
there were a number of offshore races around here that required a
certain CSR for certain classes.



MC wrote:
Really? Such as?

The Annapolis-Bermuda race, for one. There are a couple of
point-to-point SAYRA races where the phrase "CSR will be used as an
indicator of acceptability" but I haven't heard of them booting any
applicants. Of course, nobody has entered a J-30 either.

Fresh Breezes- Doug King