Motion Comfort and Chronic Seasickness

[sneuman]

Was thinking about last year's Rule 62 disaster. During the Nov. Carib 1500, a Jeanneau 45DS diverted to the Bahamas because of two crew members (including one who was a very experienced sailor) who became "chronically seasick". The boat was swamped at a harbor entrance and one of the crew was lost.

I myself don't have much of a seasickness problem, but I understand how horrible it can be (at least for an initial adjustment period) for many people.

My question is how much role, if any, did the 45's relatively poor (at least by the numbers) motion comfort numbers play in this disaster? Had it not been for the mal de mer, these folks never would have diverted and gotten themselves into a (presumably) unfamiliar harbor with a vicious sea whipping up the entrance.

[goboatingnow]

Originally Posted by sneuman

Was thinking about last year's Rule 62 disaster. During the Nov. Carib 1500, a Jeanneau 45DS diverted to the Bahamas because of two crew members (including one who was a very experienced sailor) who became "chronically seasick". The boat was swamped at a harbor entrance and one of the crew was lost.

I myself don't have much of a seasickness problem, but I understand how horrible it can be (at least for an initial adjustment period) for many people.

My question is how much role, if any, did the 45's relatively poor (at least by the numbers) motion comfort numbers play in this disaster? Had it not been for the mal de mer, these folks never would have diverted and gotten themselves into a (presumably) unfamiliar harbor with a vicious sea whipping up the entrance.

Having sailed this model. Its not on any way un-sea kindly. Well it's similar to other modern designs. My experience is that people sensitive to bad sea sickness ( and women seem particularly sensitive ) get sick irrespective of the boat.

Dave

[sailorboy1]

What is the motion control number for the boat in question?

It doesn't necessary go along with a lower displacement/length ratio. All the newer boats have a lower DLR because they carry the waterline back more. But they become the same as the older once you consider the heeled water length.

On my Hunter 410 the DLR is a LOT less than my last Cal-39. BUT the Comfort number was about the same. I was concerned about the low DLR, but now that I've sailed it I can say it is at least as confortable motion (better really).

I think a lot of the older ratio numbers and general rules don't apply well to newer bottom designs.

[Vasco]

Size doesn't really make any difference as far as pleasure craft go. Maybe on a cruise ship with all their stabilizers but on a small (relative term) boat it makes no difference in storm conditions. 100 feet or 50 feet or 200 feet, it's all uncomfortable. If you're prone to seasickness, only time at sea (for me it took two years) or staying ashore will cure you.

[Jamel]

Ginger biscuits are good to help prevent seasickness. However the best preventitive is a Norwegen navy remedy, " Dencorub" a linament cream (australia), rub a little behind the ears where those seasick patches are applied.

[Kettlewell]

I can't comment on the specific boat in this example, but I do know that sea sickness is a huge factor in both comfort and safety, and it is also an often overlooked factor. In my experience, owning eight different cruising boats you can sum things up this way: more weight is better, a deeper more traditional hull shape is better, and noise is a huge factor that is often not examined. Old, traditional wooden boats with deep full bilges would have the occupants near or below the waterline, lessening the motion drastically, and the thick and absorbent hull materials reduced the sound stress dramatically. Having said that, people have designed modern, fast, high-freeboard boats that they claim are good for seasickness issues, but I must say I have not been on one offshore yet, so I can't speak to that. My wife found catamarans to be tough on seasickness due to the violent and quick motion, and all the noise; however, many others will disagree. She is prone to sickness, while I am not, so I ended up with a heavy, relatively deep design, that allows her to go down right around the waterline and lie down in a quiet place, which helps her a lot. Also, she does not like pitching motion, but can take long slow rolling motions. Again, other folks may have different reactions.

[sneuman]

Well, the reason I asked is that one of the women apparently had a fair amount of sea time in various conditions. I realize this could have been a particularly bad trip for her, or it could be the boat. It's been my experience that my wife has gotten seasick on an Ericson 38 (motion comfort = 25) but doesn't on our Tayana 37 (motion comfort = 40) in roughly the same conditions.

That makes me wonder if it was the sailor or the boat.

[Bash]

Ted Brewer states that when he developed the formula for a motion comfort ration, he was working tongue in cheek. The formula, MCR = Disp / (2/3*((7/10 * LWL)+(1/3 *LOA))*Beam4/3, basically rewards displacement while penalizing waterline.

The formula, while flawed, is not without some value. For many years I raced an Olson 30, an ultralight which has a motion comfort ratio of 9.75. That boat would absolutely beat up its crew, so much so that when I finally turned 40 I had to "retreat" to a heavier boat, an Express 37 with a motion comfort ratio of 18.11. That boat felt like a Cadillac after the Olson 30, but is not nearly as comfortable as my current boat, which has as much ballast as the entire displacement of the Express 37.

Regardless, the formula doesn't say much more than that heavier boats tend to respond less to wave action. It's kinda like hypothesizing that you'll feel less road vibration in a Dodge Caravan than in a Ferrari. Duh. But where the formula is weak is in how it deals with beam. We know that greater beam provides greater stability, and that greater stability downwind actually increases comfort. However, Brewer's formula doesn't factor this in. The only way his formula absolutely works in terms of beam is if the boat is sitting dead in the water, sails down, bow pointed into the prevailing waves.

Most of us don't sail that way.

[Bash]

....one other deficiency in Brewer's formula, by the way, is that doesn't account for underbody shape, such as the boat's chines. Indeed, a boat with a shoal draft keel will rate the same as a boat with a deep draft keel as long as their displacements don't vary. And the formula doesn't see any difference between a full keel, a fin keel, or bilge keels. Ultimately, it's just about weight vrs length.

[Kettlewell]

We know that greater beam provides greater stability, and that greater stability downwind actually increases comfort.

I don't know that we know that. At least in my experience, some beamy, stiff boats have a very snappy motion, which is hard on some people. Again, back to my wife, she doesn't mind a long slow roll downwind, but hated a catamaran's very jerky back and forth but shorter motions. I have subsequently spoken to other folks that have had the same reaction. I have also spoken to some who believe that very narrow slack bilged boats are actually more comfortable, but I have never tried one.

[MarkJ]

Originally Posted by sneuman

My question is how much role, if any, did the 45's relatively poor (at least by the numbers) motion comfort numbers play in this disaster? .

I doubt whatever you are suggesting had an effect.

A fool and his life are soon parted.

They could have gone on 30 nms and found a 17nm wide deepwater opening leading to protection from waves.

They did not do it and paid the consequences.

I have sailed in full keel boats and yes people get sea sick in them too. Only a fool would take a full keel boat into the spot the Jeneau went in; only a fool would take any boat in there.

I do hate these threads because they so often start as troll questions (Salty Monkey being the worst offender). Instead of thinking about the boat look at the chart, and take some folks prone to seasickness to sea in ANY sort of boat in those conditions. Then add the factor of stupidity.

People die.

[Randyonr3]

Originally Posted by MarkJ

I doubt whatever you are suggesting had an effect.

A fool and his life are soon parted.

They could have gone on 30 nms and found a 17nm wide deepwater opening leading to protection from waves.

They did not do it and paid the consequences.

I have sailed in full keel boats and yes people get sea sick in them too. Only a fool would take a full keel boat into the spot the Jeneau went in; only a fool would take any boat in there.

I do hate these threads because they so often start as troll questions (Salty Monkey being the worst offender). Instead of thinking about the boat look at the chart, and take some folks prone to seasickness to sea in ANY sort of boat in those conditions. Then add the factor of stupidity.

People die.

Very well said Mark, Very well indeed..............

[denverd0n]

Originally Posted by MarkJ

Then add the factor of stupidity. People die.

Like they say, you can't cure stupid.

For sea sickness, I still like Admiral Lord Nelson's cure--two hours of sitting under a tree.

[sneuman]

Bash,

I was speaking anecdotally (this boat pounds a lot, this one not so much ...) and only used the formula as a rough comparison once Don suggested going in that direction.

I know the numbers are controversial, at best.

[sneuman]

Mark -- I do resent the troll accusation. Rest assured, if I ask a question, it's because I genuinely like hearing the range of opinions (especially yours!) that are available on CF