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#1
posted to rec.boats.cruising
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Roll Pitch & Comfort
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 |
#2
posted to rec.boats.cruising
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Roll Pitch & Comfort
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 |
#3
posted to rec.boats.cruising
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Roll Pitch & Comfort
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. |
#4
posted to rec.boats.cruising
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Roll Pitch & Comfort
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/ |
#5
posted to rec.boats.cruising
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Roll Pitch & Comfort
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 Best way to reduce roll is to put some sails up! Dennis. |
#6
posted to rec.boats.cruising
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Roll Pitch & Comfort
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 |
#7
posted to rec.boats.cruising
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Roll Pitch & Comfort
" 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 |
#8
posted to rec.boats.cruising
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Roll Pitch & Comfort
"Red" wrote in message ... 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 There is a degree of subjectivity in that. The two largest factors affecting comfort are the condition of the person's inner ear and their body morphology. The inner ear obviously is the source of balance but body morphology is interesting. These boat studies tend to be old and don't account for obesity and the roll pitch comfort of the human body itself as a result of mechanical displacements of large amounts of fat tissue. A thin person may be quite comfortable in those old fashioned vibrating belt machines but an obese one would experience extreme discomfort as they fly about all over the place. An obese person's fat tissues can couple into the motion of the boat in a positive sympathetic mode, increasing the motion of the boat and also of the person itself. This mechanical regime would increase until non linearities in the adipose tissue or transient boat displacements introduced harmonics and dampened the overall response. The concepts of comfort with regard to boat motion are indeed true, but the specifics, namely rates and axis should be reconsidered due to the ever increasing size and elasticity of boat passengers. This is exceedingly true in the States, where eating has become full time sport. Nigel |
#9
posted to rec.boats.cruising
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Roll Pitch & Comfort
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. |
#10
posted to rec.boats.cruising
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Roll Pitch & Comfort
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. |
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