Tom wrote:
IMO, Ted Brewer's motion comfort ratio is BS. Brewer is an interested
party and he admits that the "ratio" was made up as a kind of joke.
There is absolutely no evidence that it works. As a general theory is
is indefensible. On any given day I'd bet you'll be a lot more
comfortable in a Catalina 30 than you will be in a 5.5 meter both in
terms of motion comfort and amenities but you certainly will not learn
that from the "comfort" ratio. Any comfort motion rating system that
says that the Colin Archer ketch is the pinnacle of comfortable is
just plain cr@p. I'd rate the "comfort ratio" as significantly less
important than the color of the mast step in my boat comparison list.
Of course, TB has a different view. You can see his rational he
http://www.tedbrewer.com/yachtdesign.html.

-- Tom.

Hi Tom,
While I have no experience in yacht design whatsoever, I can see what
Brewer was trying to accomplish. The following is a partial copy of his
description from his website:

"COMFORT RATIO (CR): This is a ratio that I dreamed up, tongue-in-cheek,
as a measure of motion comfort but it has been widely accepted and,
indeed, does provide a reasonable comparison between yachts of similar
type. It is based on the fact that the faster the motion the more
upsetting it is to the average person. Given a wave of X height, the
speed of the upward motion depends on the displacement of the yacht and
the amount of waterline area that is acted upon. Greater displacement,
or lesser WL area, gives a slower motion and more comfort for any given
sea state.

...The intention is to provide a means to compare the motion comfort
of vessels of similar type and size, not to compare that of a Lightning
class sloop with that of a husky 50 foot ketch."

So while I agree that there may, or may not be, hard "science" behind it
(and I admit I wouldn't know), it seems useful as a comparison when
looking at similar type boats for a given usage. And it seems to agree
with the descriptions and discussions that were put forth in that
earlier thread by Roger Long and others.

Red

On Feb 28, 5:05 pm, Red wrote:
Hi Tom,
...So while I agree that there may, or may not be, hard "science" behind it
(and I admit I wouldn't know), it seems useful as a comparison when
looking at similar type boats for a given usage. And it seems to agree
with the descriptions and discussions that were put forth in that
earlier thread by Roger Long and others. ...

Hi Red,

Sorry I went ballistic over all this. It is great to be talking boats
again in the group and I appreciate your post. Obviously, I don't
think the CR has any value at all, but I'm certainly not an expert
either. I'll Let Roger speak for himself, but he's selling boats that
would rate miserably on the Brewer CR (because they have lightly
loaded water planes) and has written a paper on their seakindliness.
Do keep in mind that Brewer is selling boats designs that are more
expensive to build, slower and have less usable interior space than
they typical mass market boats. It happens that the only generally
used metric that they rate well on is the one he made up... And, while
I actually like many of his designs a lot I'm waiting to see some
empirical support for his CR before I give it any weight at all...

-- Tom.

Tom wrote:
Sorry I went ballistic over all this.

Ha! Going ballistic seems to be something most of us here do at least
once in awhile (I'm guilty), so no prob.

It is great to be talking boats
again in the group and I appreciate your post. Obviously, I don't
think the CR has any value at all, but I'm certainly not an expert
either. I'll Let Roger speak for himself, but he's selling boats that
would rate miserably on the Brewer CR

I would welcome Roger's further enlightenment on this subject.

Do keep in mind that Brewer is selling boats designs that are more
expensive to build, slower and have less usable interior space than
they typical mass market boats. It happens that the only generally
used metric that they rate well on is the one he made up... And, while
I actually like many of his designs a lot I'm waiting to see some
empirical support for his CR before I give it any weight at all...

-- Tom.

I understand. What I have seen though, are ratings that Brwewer himself
has done on numerous boat designs other than his own, and he still finds
the CR to be useful for comparison in those cases - not comparisons
*against his own designs*, but against similar boats for similar usage
regardless of who designed either of them.

Red

On Feb 28, 6:29 pm, Red wrote:
...What I have seen though, are ratings that Brwewer himself
has done on numerous boat designs other than his own...

I have not seen these. Do you have a link? However, what I want to
see is experimental evidence that people actually experience less
discomfort on boats with high CRs. I think the physics of the CR is
so simplified that there is little reason to believe there will be
much correlation between high CRs and more comfortable boats or even
boats with slower rates or smaller magnitudes of heave, pitch and
roll. The argument that it only works for very similar boats seems to
suggest it is broken, too. Very similar boats will behave so
similarly that it may be the only way to tell if you're more
comfortable is to calculate the CR...

Sigh, since the horse is dead it won't mind me beating on it. I think
Brewer's basic premise is wrong. One more reason I think the CR is
bogus is that it assumes that the sails can always provide roll
damping. This is often not the case underway and is seldom if ever
the case at anchor. A boat with a high CR will almost certainly be
unlivable at anchor if there is even a suggestion of a ground swell.
It is axiomatic that cruisers spend 90% of their time at anchor. So,
even if Brewer is, by some ineffable chance, right about the CR
underway you're still likely to gain a whole bunch more "comforts" on
a low CR boat at anchor than you will lose underway.

-- Tom.

Brewers' designs are known to be sea kindly. Maybe he is on to something?
Gordon

On Feb 28, 6:29 pm, Red wrote:

...What I have seen though, are ratings that Brwewer himself
has done on numerous boat designs other than his own...

Tom replied:
I have not seen these. Do you have a link?

No Tom, I have seen these comparisons in magazines he writes articles
for. If I can dig one up I'll send you the info.

Red

On Mar 1, 3:22 pm, Red wrote:
On Feb 28, 6:29 pm, Red wrote:

...What I have seen though, are ratings that Brwewer himself
has done on numerous boat designs other than his own...

Tom replied:
I have not seen these. Do you have a link?

No Tom, I have seen these comparisons in magazines he writes articles
for. If I can dig one up I'll send you the info.

Red

Thanks. It'd be interesting to see the citations, but don't panic
over it.

Cheers,

-- Tom.