There was a thread back a ways that was about roll rate and comfort Vs.
safety. Just thought if anyone was interested there are two lists on the
boatdesign.net/forums that show Ted Brewer's " motion comfort ratio" of
quite a few different sailboats. May be useful as a comparison chart for
anyone looking at buying a boat. First list is of boats with a
comparatively high MC ratio, and the second list is of boats with lower
ratios.

http://www.boatdesign.net/forums/showthread.php?t=20655
Scroll down to find the lists in two posts.

Red

Red wrote:
There was a thread back a ways that was about roll rate and comfort Vs.
safety. Just thought if anyone was interested there are two lists on the
boatdesign.net/forums that show Ted Brewer's " motion comfort ratio" of
quite a few different sailboats. May be useful as a comparison chart for
anyone looking at buying a boat. First list is of boats with a
comparatively high MC ratio, and the second list is of boats with lower
ratios.

http://www.boatdesign.net/forums/showthread.php?t=20655
Scroll down to find the lists in two posts.

Red

More
http://www.mahina.com/boats.html
http://www.tedbrewer.com/yachtdesign.html
http://www.image-ination.com/sailcalc.html
and the best
http://www.johnsboatstuff.com/technica.htm
G

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.

On 2008-02-27 02:01:49 -0500, " said:

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.

I'd be a bit less inflammatory if I wrote on the subject, but I have to
say that I agree for the most part.

Then again, if we're heeling between 15 and 25 degrees, my lovely lady
knows not to complain as that's normal for our lovely
lady/beast/vessel. If she were longer and heavier, the acceptable heel
numbers would be a bit lower.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

On Wed, 27 Feb 2008 10:55:51 GMT, Jere Lull wrote:

On 2008-02-27 02:01:49 -0500, " said:

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.

I'd be a bit less inflammatory if I wrote on the subject, but I have to
say that I agree for the most part.

Then again, if we're heeling between 15 and 25 degrees, my lovely lady
knows not to complain as that's normal for our lovely
lady/beast/vessel. If she were longer and heavier, the acceptable heel
numbers would be a bit lower.

It is somewhat interesting that the antiroll fins on a cruise ship
will kill the roll completely, but the ship still pitches noticably in
one foot waves.

Casady

" said:
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.

No, it's defensible on several grounds. It was invented by a
knowledgeable NA, it does model
that "bigger + heavier = more comfort" which is true, and it is widely
quoted.

None of that makes it a valuable quantity for comparing boats IMHO.
For example, if you take two boats of very similar dimension &
displacement, the one with longer
overhangs will have a higher "Motion Comfort Index." Why? Because old
salty prejudices favor boats
with long overhangs. Long overhangs were fashionable in the early
1900s but they don't make a boat
more comfortable at sea, if anything they make it wetter, slower, and
less "comfortable" by most
definitions of the word.

.... 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.

And you'd be more comfortable yet in a cheap hotel. Where does this
fit into the 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.



Jere Lull wrote:
I'd be a bit less inflammatory if I wrote on the subject,

Yeah, but where's the fun in that?


Then again, if we're heeling between 15 and 25 degrees, my lovely lady
knows not to complain as that's normal for our lovely
lady/beast/vessel. If she were longer and heavier, the acceptable heel
numbers would be a bit lower.


And most likely, slower in lighter air.
95% (or more) of all sailing is done in winds of less than 15 knots.
Therefor, any boat
which does *not* have to reef or reduce sail in 15 ~ 18 knot winds is
a *less* capable
vessel. But again, old salty prejudices lean the other way....

Fresh Breezes- Doug King

On Wed, 27 Feb 2008 07:29:41 -0800 (PST), wrote:

No, it's defensible on several grounds. It was invented by a
knowledgeable NA, it does model
that "bigger + heavier = more comfort" which is true, and it is widely
quoted.

It also assigns a very low comfort number to the Frers 41 which jibes
very closely with my experience. It has a quick squirrelly motion
offshore and is a bit of a vomit comet.

On Feb 27, 5:29 am, wrote:
" said:
IMO, Ted Brewer's motion comfort ratio is BS. ...

No, it's defensible on several grounds. It was invented by a
knowledgeable NA, it does model
that "bigger + heavier = more comfort" which is true, and it is widely
quoted.

No, the ratio does not say that "bigger" is more comfortable. Just
the opposite. It penalizes length (70% waterline + 30% overall) and
beam to the 1/3. The results of this can be silly. The idea that an
Alberg 30 is vastly more "comfortable" than a Transpac 52 is absurd.

I want to be clear that I'm not disparaging Brewer. He has drawn some
beautiful boats and written at least one very good book. It's just
his "CR" that's bogus. Brewer claims that heave and pitch response
will be slower on a boat with a heavily loaded water plane and low ppi
all else being equal. That's true for heave and probably reasonably
indicative for pitch. He also asserts that roll response will be
slower on heavy narrow boats. That may be true, but misses some major
factors. The problem is that he goes on to assert that boats with
slow initial pitch and roll and heave responses are "more
comfortable". This completely ignores major factors like period,
amplitude and damping. And, of course, begs the questions of what is
comfort is and what conditions we are talking about. Down wind boats
with high "CR" will be slow and have a tendency to roll
uncontrollably. Upwind they will be slow but wet; if you don't rise
to meet a wave you must go through it. Indeed, a high "CR" pretty
much assures slowness. It is true that slower is generally more
comfortable. It is also true that you can sail a fast boat slowly but
you can't make a slow boat fast... Theres more, but my work is
calling.

--Tom.

On Feb 27, 4:08 pm, " wrote:
On Feb 27, 5:29 am, wrote:

" said:
IMO, Ted Brewer's motion comfort ratio is BS. ...

No, it's defensible on several grounds. It was invented by a
knowledgeable NA, it does model
that "bigger + heavier = more comfort" which is true, and it is widely
quoted.

No, the ratio does not say that "bigger" is more comfortable.

Yes it does.
Look at the math.

Increase displacement, "Comfort Ratio" goes up. Increase LOA but not
LWL, the ratio goes up. The funny thing is that if you take the same
LOA and Disp, and reduce LWL, the ratio goes up. If you keep
everything the same and decrease beam, the ratio goes up.

The assumption is that the heavier a footprint a boat has, the higher
load per waterplane area, will give a boat more comfortable motion in
a seaway. There is some real-life justification for that, but to
assume that narrow heavy boats with long overhangs are the ultimate in
seagoing comfort is absurd.

.... Just
the opposite. It penalizes length (70% waterline + 30% overall) and
beam to the 1/3. The results of this can be silly. The idea that an
Alberg 30 is vastly more "comfortable" than a Transpac 52 is absurd.


In this case, "comfort" is defined only by the boat's motion in a
seaway.


I want to be clear that I'm not disparaging Brewer. He has drawn some
beautiful boats and written at least one very good book.

Many moons ago, my family owned a Brewer design. It was a good boat.

It's just
his "CR" that's bogus. Brewer claims that heave and pitch response
will be slower on a boat with a heavily loaded water plane and low ppi
all else being equal. That's true for heave and probably reasonably
indicative for pitch. He also asserts that roll response will be
slower on heavy narrow boats. That may be true, but misses some major
factors. The problem is that he goes on to assert that boats with
slow initial pitch and roll and heave responses are "more
comfortable". This completely ignores major factors like period,
amplitude and damping.

Agreed.
But those can't be reasonably quantified with the very simple
dimensions commonly available.


.... And, of course, begs the questions of what is
comfort is and what conditions we are talking about. Down wind boats
with high "CR" will be slow and have a tendency to roll
uncontrollably. Upwind they will be slow but wet; if you don't rise
to meet a wave you must go through it. Indeed, a high "CR" pretty
much assures slowness. It is true that slower is generally more
comfortable. It is also true that you can sail a fast boat slowly but
you can't make a slow boat fast...

Agreed


Theres more, but my work is
calling.


I'd say your work here is done

DSK

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