Motion Comfort

[Randyonr3]

Motion Comfort???

I've heard this term used when describing how a boat reacts, but my question is where...
This is not another debate on full keel or fin keel.. But rather where dose one boat have more "Motion Comfort" over another..
While sailing Our Beneteau, offshore about 100 miles or so, in 20 to 25 knots of wind, we're healed about 10 to 12 degrees, and have a boat speed in the 8 to 10 knots... swells are 8 feet every 15 seconds (not bad)
And the wife has just finished cooking a full breakfast, and I'm setting in the cockpit, with a plate of hotcakes and eggs, and a cup of coffee on my knee..
So where dose this "Motion Comfort" come into play on a full keel that I'm told I dont have..
My boat weighs in at 24k for 42 feet, and built in the early 80s..
am I missing something here, because I feel pretty comfy with motion my Boat has............

[Target9000]

It comes from a formula that Ted Brewer created to help describe the speed at which boats rise and fall in swells. Its that simple.

The theory is that faster rising and falling will be less comfortable than slower. It does not take into account rolling, heeling, or any number of other factors. Its name is a misnomer since it predicts only one factor out of a GREAT many that pertain to comfort. Also comfort is arguably subjective.

Ted Brewer says this, " 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."

Notice: "tongue in cheek"

Get over it. Enjoy your boat. Let people believe what they want.

[Target9000]

Errr, unless motion comfort is different than comfort ratio. Which is what I originally interpreted your post to say. Sorry if you meant something different.

[Adelie]

In the same conditions would most boats with higher "Motion Comfort Numbers" be more comfortable?

How about in rougher weather?

I have no basis for comparison personally?

As I understand it the numbers are only indicative of likely relative comfort. They will not indicate whether a particular boat will be comfortable in all conditions for a particular individual.

Frankly Brewer has indicated he came up with the formula half tounge in cheek.

[Mexdon]

Motion Comfort....originally labeled motion comfort ratio was introduced by designer Ted Brewer to have measurement of speed of movement up and down as a yacht encountered waves and swells. The faster the rise and fall meant less comfort is the idea behind the theory.

Use the link to see what it says about your boat.

Motion Comfort Ratio

[Cheechako]

Has little to do with the full keel. More to do with the hull shape, amount of overhang and short waterline etc. Narrow boats, with very round bilges and long overhangs will roll and pitch in the right water. It's an interesting thing. When I lived aboard in Seattle, I used to watch boats at the dock during windy weather. There was one rather new design by a noted designer that always rolled a lot tied to the dock. It was supposedly an offshore fast design. It rolled so much that once it looked like it might actually have a mast clash with the boat next door.

[boatman61]

Originally Posted by Mexdon

Use the link to see what it says about your boat. Motion Comfort Ratio

OK.... so I've a 12.53 Comfort Ratio...
I saw no table to see if thats good or bad...

[Target9000]

For reference....
Alberg 35 Sloop, Motion Comfort=36.48
Alberg 37, Motion Comfort=39.3
Allied Mistress 39, Motion Comfort=35.62
Allied Seawind, Motion Comfort=39.69
Allied Seawind II, Motion Comfort=36.89
Alpa A42 (S&S), Motion Comfort=44.85
Alpa A42 (S&S) Half-loaded, Motion Comfort=51.22
Amel Maramu, Motion Comfort=36.05
Amphitrite 43, Motion Comfort=37.67
Amphitrite MS45, Motion Comfort=40.15
Antigua, Motion Comfort=44.99
Baba 35, Motion Comfort=41.94
Bayfield 40, Motion Comfort=35.26
Bolger Ataraxia, Motion Comfort=36.21
Bolger Barnowl, Motion Comfort=37.85
Bolger Leeboard Catboat, Motion Comfort=38.08
Bolger Schuyt Houseboat, Motion Comfort=35.83
Brewer Orca, Motion Comfort=45.23
Brewer Sandingo, Motion Comfort=35.5
Brewer Sunshine, Motion Comfort=46.05
Brewer Thursday´s Child, Motion Comfort=44.32
Bristol 35.5, Motion Comfort=35.23
Bristol 40, Motion Comfort=36.57
Bristol 41.1, Motion Comfort=37.85
Bristol 45.5, Motion Comfort=42.97
Bristol Channel Cutter, Motion Comfort=36.89
Brolga 33, Motion Comfort=37.36
Buehler Archimedes, Motion Comfort=52.8
Buehler Dragonfly 50, Motion Comfort=48.88
Buehler Emily, Motion Comfort=37.55
Buehler Juna, Motion Comfort=45.93
Buginese Schooner, Motion Comfort=43.95
CSY 37, Motion Comfort=35.57
CSY 44, Motion Comfort=46.66
CSY 44 Pilothouse Ketch, Motion Comfort=47.94
CT 34, Motion Comfort=37.68
CT 54, Motion Comfort=51.36
CT50, Motion Comfort=50.7
Cabo Rico 37, Motion Comfort=36.61
Cabo Rico 38, Motion Comfort=38.96
Cabo Rico 42, Motion Comfort=36.77
Cabo Rico Tiburon 36, Motion Comfort=39.23
Cal 2-46, Motion Comfort=39.72
Cal 48, Motion Comfort=36.06
Caliber 47LRC, Motion Comfort=38.51
Cambria 44, Motion Comfort=35.56
Camper Nicholson 32, Motion Comfort=43.52
Cape Dory 36, Motion Comfort=35.5
Cape George 31, Motion Comfort=42.16
Cape George 34, Motion Comfort=44.69
Cape George 36, Motion Comfort=47.54
Chatam 330, Motion Comfort=41.76
Cheoy Lee Clipper 36, Motion Comfort=37.41
Cheoy Lee Clipper 42, Motion Comfort=38.59
Cheoy Lee Offshore 31, Motion Comfort=35.45
Cheoy Lee Offshore 50, Motion Comfort=43.51
Cheoy Lee Robb 35 Yawl, Motion Comfort=37.77
Cherubini 44, Motion Comfort=42.05
Cherubini 48, Motion Comfort=41
Chris Craft Sail Yacht 35, Motion Comfort=37.32
Colin Archer 37 Pilot Cutter, Motion Comfort=54.67
Columbia 38, Motion Comfort=35.01
Columbia 40, Motion Comfort=38.29
Columbia 41 Shoal Sloop, Motion Comfort=38.21
Columbia 45, Motion Comfort=40.32
Columbia 45 Sloop, Motion Comfort=35.82
Columbia 50 (Tripp), Motion Comfort=46.64
Columbia 56, Motion Comfort=49.97
Columbia 56 MS, Motion Comfort=49.97
Columbia 57, Motion Comfort=49.77
Colvin Saugeen Witch, Motion Comfort=35.29
Concordia Yawl, Motion Comfort=38.99
Corbin 39, Motion Comfort=42.7
Cornish Crabber Pilot 30, Motion Comfort=35.37
Coronado 35 Ketch (SK), Motion Comfort=36.01
Coronado 35 Sloop (SK), Motion Comfort=36.01
Coronado 41, Motion Comfort=37.95
Creala 40, Motion Comfort=39.34
Crealock 40, Motion Comfort=37.23
Crealock 40 Twin Stay, Motion Comfort=39.34
Dickerson 41, Motion Comfort=37.83
Dix Hout Bay 30, Motion Comfort=37.3
Downeast 45 Ketch, Motion Comfort=45.4
Dreadnought 32, Motion Comfort=47.49
Duncanson 29, Motion Comfort=39.9
Duncanson 40, Motion Comfort=43.71
Endeavor 37, Motion Comfort=38.19
Endeavour 40 Sloop, Motion Comfort=36.59
Endeavour 43 Ketch, Motion Comfort=39.54
Ericson 39, Motion Comfort=35.25
Ericson 41, Motion Comfort=35.57
FISHER 30, Motion Comfort=41.43
Fantasia 35 MK II, Motion Comfort=50.99
Fast Passage 39, Motion Comfort=38.72
Folkes 39 Cutter (Steel), Motion Comfort=41.86
Formosa 46, Motion Comfort=37.8
Formosa 51, Motion Comfort=53.28
Freedom 45, Motion Comfort=35.18
Fuji 32 Ketch, Motion Comfort=35.73
Fuji 35, Motion Comfort=40.74
Fuji Ketch 45, Motion Comfort=43.45
Gail Storm (Exp. Design), Motion Comfort=35.5
Gartside Cutter 30 Ft, Motion Comfort=49.91
Gibbons 42, Motion Comfort=35.57
Gilbert Scarper Flo, Motion Comfort=37.77
Giles 38, Motion Comfort=40.78
Golden Hind 31 MKll, Motion Comfort=39.33
Grampian Classic 31, Motion Comfort=36.13
Gulf 32 Pilothouse, Motion Comfort=39.57
Gulfstar 50ft Ketch, Motion Comfort=38.56
Hallberg Rassy HR39, Motion Comfort=35.7
Hans Christian 38, Motion Comfort=43.52
Hans Christian 41T, Motion Comfort=46.46
Hardin 45 Ketch, Motion Comfort=43.36
Hartley 36, Motion Comfort=48.17
Hartley Fijian 43 Cutter, Motion Comfort=45.16
Heritage 35 By McCurdy & Rhodes, Motion Comfort=37.83
Herreshoff Araminta, Motion Comfort=36.78
Herreshoff Block Island Boat, Motion Comfort=50.35
Herreshoff Bounty, Motion Comfort=46.24
Herreshoff Diddikai, Motion Comfort=47.75
Herreshoff Double-ended Sloop, Motion Comfort=40.29
Herreshoff Joann, Motion Comfort=54.69
Herreshoff Leeboard Ketch, Motion Comfort=41.04
Herreshoff Lifeboat Ketch, Motion Comfort=44.19
Herreshoff Manana, Motion Comfort=49.81
Herreshoff Mobjack, Motion Comfort=50.33
Herreshoff Nereia, Motion Comfort=40.23
Herreshoff Persephone, Motion Comfort=51.95
Herreshoff Restricted Sail Area Cruiser, Motion Comfort=38.13
Herreshoff Santee, Motion Comfort=47.97
Herreshoff Unicorn, Motion Comfort=51.8
Herreshoff Wagon Box, Motion Comfort=42.98
Herreshoff Walrus, Motion Comfort=54.75
Hillyard 9 Ton, Motion Comfort=46.72
Hinckley 38, Motion Comfort=37.9
Hinckley Bermuda 40, Motion Comfort=35.57
Hinckley Pilot 35 Sloop, Motion Comfort=36.58
Hinckley Sou Wester 51, Sloop, Motion Comfort=44.91
Hinckley Sou´wester 42, Yawl, Motion Comfort=36.21
Hood No Compromise 54 (sloop), Motion Comfort=37.1
Hout Bay 30 Gaff Cutter, Motion Comfort=37.97
Hughes Columbia 391, Motion Comfort=38.89
Hustu 70, Motion Comfort=49.29
Hylas 54, Motion Comfort=38.79
Irwin 37 Mk V, Motion Comfort=36.93
Irwin 46 Ketch, Motion Comfort=39.53
Irwin 52, Motion Comfort=47.6
Irwin 65 Ketch, Motion Comfort=46.75
Island Packet 45, Motion Comfort=35.29
Island Packet 485, Motion Comfort=35.6
Island Trader 36, Motion Comfort=35.16
Islander 44, Motion Comfort=39.56
Jason 35, Motion Comfort=35.03
Kelly Peterson 46, Motion Comfort=38.18
Kettenburg PCC, Motion Comfort=39.38
Knutson 35, Motion Comfort=35.74
Landfall 39 (Sino Amer.), Motion Comfort=42.14
Laurent Guiles Vertue, Motion Comfort=46.91
Lecomte Northeast 38, Motion Comfort=36.12
Liberty 49, Motion Comfort=43.07
Little Harbor 44, Motion Comfort=42.43
Lord Nelson 33, Motion Comfort=35.55
Lord Nelson 35, Motion Comfort=35.86
Lyle Hess 32, Motion Comfort=35.26
MacNaughton Passagemaker, Motion Comfort=42.55
Malo 41, Motion Comfort=38.13
Mariner 35, Motion Comfort=42.3
Mariner 39 C-cockpit, Motion Comfort=38.46
Mariner 40, Motion Comfort=47.22
Mariner 47 (Cruising Version), Motion Comfort=45.55
Mariner Ketch 36, Motion Comfort=43.44
Mason 44, Motion Comfort=41.87
Morgan 37OI MKII Sloop, Motion Comfort=36.84
Morgan 45 Ketch, Motion Comfort=35.19
Morgan 462 Sloop (1981), Motion Comfort=35.15
Morgan 462(1979), Motion Comfort=42.04
Morgan 512, Motion Comfort=43.82
Nauticat 331, Motion Comfort=35.36
Nauticat 44, Motion Comfort=43.69
Navy 44, Motion Comfort=39.62
New York 46 (Roberts), Motion Comfort=48.23
Nicholson 31, Motion Comfort=38.72
Nicholson 33, Motion Comfort=36.59
Nicholson 35, Motion Comfort=36.14
Norseman 447, Motion Comfort=35.61
Ohlson 41 Steel, Motion Comfort=43.85
Passoa 47, Motion Comfort=35.54
Passport 47+3, Motion Comfort=37.84
Pearson 385, Motion Comfort=37.22
Pearson 40, Motion Comfort=35.73
Pearson 43 (1968-72), Motion Comfort=46.38
Pearson Invicta Mark II, Motion Comfort=40.08
Peterson 44, Motion Comfort=37.92
Quoddy Pilot, Motion Comfort=38.98
Rafiki 35, Motion Comfort=36.69
Rawson 30, Motion Comfort=40.12
Reliance, Motion Comfort=53.47
Rhodes Bounty II, Motion Comfort=40.8
Rhodes Reliant, Motion Comfort=44.95
Roberts 28 - Steel, Motion Comfort=37.66
Roberts 35 Cutter, Motion Comfort=38.21
Roberts 420 (cat-ketch), Motion Comfort=41.28
Roberts 45 Pilothouse C. C., Motion Comfort=39.65
Roberts 470, Motion Comfort=37.49
Roberts 53 Aluminum, Motion Comfort=35.57
Roberts 53 Steel Ketch, Motion Comfort=40.77
Roberts 55 Cutter, Motion Comfort=48.98
Roberts 58, Motion Comfort=42.83
Rossiter Curlew, Motion Comfort=37.61
Rossiter Pintail (27 F), Motion Comfort=39.97
Rustler 36, Motion Comfort=35.88
Sailmaster 56 MS, Motion Comfort=49.97
Sea Trader, Motion Comfort=35.59
Seafarer 31 Yawl, Motion Comfort=35.09
Seafarer 34, Motion Comfort=37.08
Seafarer 38 Ketch, Motion Comfort=37.27
Shamrock III, Motion Comfort=52.49
Skye 51, Motion Comfort=43.22
Slocum 43 Cutter, Motion Comfort=37.73
South Coast One Design (C&N), Motion Comfort=46.27
Southern Cross 31, Motion Comfort=38.8
Souwester 51, Motion Comfort=43.84
Sovereign 30, Motion Comfort=43.38
Spencer 44, Motion Comfort=39.76
Spencer 53, Motion Comfort=35.31
Spray 38 Centennial (Roberts), Motion Comfort=46.39
Spray 45 Centennial (Roberts), Motion Comfort=47.35
Stellar 53, Motion Comfort=40.71
Stevens Custom 40, Motion Comfort=37.16
Swallowcraft Scylla, Motion Comfort=36.87
Swan 36, Motion Comfort=37.64
Swan 48, Motion Comfort=42.16
Swan 57 CB Sloop, Motion Comfort=39.42
Tahitiana 32, Motion Comfort=49.38
Talbot 48, Motion Comfort=48.61
Tanton 43, Motion Comfort=38.34
Tashiba 36, Motion Comfort=36.28
Tashiba 40, Motion Comfort=41.25
Tayana 37 Cutter, Motion Comfort=40.78
Tayana 48´ Deck Saloon, Motion Comfort=35.77
Tayana 52, Motion Comfort=35.57
Tayana 55, Motion Comfort=37.66
Tayana V-42, Motion Comfort=43.33
Tayana V-42 MKII, Motion Comfort=45.35
Tayana Vancouver 460, Motion Comfort=51.33
True North 34, Motion Comfort=45.92
UWB 333, Motion Comfort=41.15
Union Polaris 36, Motion Comfort=40.06
Vagabond 39PH, Motion Comfort=42
Vagabond 42, Motion Comfort=43.43
Vagabond 47, Motion Comfort=48.71
Valiant 50, Motion Comfort=37.95
Van De Stadt 40 (1954), Motion Comfort=38.41
Waterline 50, Motion Comfort=41.14
Watkins 36, Motion Comfort=36.58
Wauqiez Hood 38, Motion Comfort=38.14
Westsail 28, Motion Comfort=41.08
Westsail 32, Motion Comfort=43.61
Westsail 42 Cutter, Motion Comfort=44.6
Westsail 42 Ketch, Motion Comfort=44.6
Willard 8-ton Cutter, Motion Comfort=40.27
Young Sun 35, Motion Comfort=36.09
Young Sun 43 PH, Motion Comfort=43.13
Zinnia, Motion Comfort=48.48

[Target9000]

Originally Posted by boatman61

OK.... so I've a 12.53 Comfort Ratio...
I saw no table to see if thats good or bad...

12.53. You must go airborne half the time.

[Cheechako]

is a higher number better or worse?

[MarkSF]

Originally Posted by boatman61

OK.... so I've a 12.53 Comfort Ratio...
I saw no table to see if thats good or bad...

Higher is better. But it's a screening formula, a rough guide. It goes up with boat size. So you'd expect a 21 ft boat to have a much lower number than a 40ft one.

What counts is, are you comfortable sailing yours, in the places and conditions you sail in?

[Mexdon]

Originally Posted by boatman61

OK.... so I've a 12.53 Comfort Ratio...
I saw no table to see if thats good or bad...

The higher the number the more resistant the boat is to movement....this is the up and down movement and not rolling. The motion comfort ratio does not relate to rolling motion.

[sneuman]

Originally Posted by Cheechako

Has little to do with the full keel. More to do with the hull shape, amount of overhang and short waterline etc. Narrow boats, with very round bilges and long overhangs will roll and pitch in the right water. It's an interesting thing. When I lived aboard in Seattle, I used to watch boats at the dock during windy weather. There was one rather new design by a noted designer that always rolled a lot tied to the dock. It was supposedly an offshore fast design. It rolled so much that once it looked like it might actually have a mast clash with the boat next door.

I've made the same observation. Some boats "settle down" very quickly after encountering a passing wake, while others gallop like an unbroken stallion. I got to test out my theory on this about a year ago, when I was asked to teach sailing to the gentlemen who had bought the worst boat in the marina for this sort of unbridled motion. Indeed, it was not a nice boat to be aboard even in a rather slight chop.

So, more than any number, I would find this the best indicator.

[Bash]

Originally Posted by MarkSF

It goes up with boat size.

Yeah, it goes up with boat size.

So we needed Ted Brewer to tell us that larger boats tend to be more comfy than smaller boats?

[Target9000]

It goes up with boat size GENERALLY. But you can see in the list I posted, this doesn't always hold true.

Spencer 53, Motion Comfort=35.31
Spray 38 Centennial (Roberts), Motion Comfort=46.39