Stars for comfort

If you look on Wikipedia the definition of “comfort”, you will see that it is understood as a subjective feeling like love, which are difficult to define and measure. For this purpose, the on-Board comfort can be decomposed into a number of components. One of them is smell, and if it’s the exhaust, you don’t feel well, even if the ship is not moving. If the on-Board bad food and drinks (or you abused them), it will also cause discomfort. Other factors like temperature, wind, humidity also affect the level of comfort, however, we focus on three aspects: noise and vibration, human movement and postural stability, as well as on the accelerations experienced by the body during oscillation of the vessel.

Scientific evidence suggests that our body is sensitive to accelerations caused by high – and low-frequency fluctuations in horizontal and vertical planes, but there is a specific frequency where the sensitivity is maximum. It is 0.2 Hz, which corresponds to a period of five seconds. What do you think: what is the most common frequency of pitching most of the ships at anchor? Correct: five seconds. That is why many people react negatively to pitching, and one of our tasks is to estimate how many of them will suffer from seasickness.

If the person is a long time to experience the effects of vibration, it also becomes uncomfortable. Try to travel a thousand miles in sedan class “luxury” on a Fiat Cinquecento. It may take same time, but it will feel very different, because in a small car you will feel more acceleration, which will cause fatigue.

In MARIN, we need to measure everything, so for comfort we use three measures: rating of comfort, the true angle of the force of gravity acting on the person and the dose value vibration. The data obtained by us (Fig. 1 and 2) help to explain why different people react to the same fluctuations of the vessel in different ways. The most sensitive young people, especially women, who already have experience seasickness, while with age the sensitivity to it decreases. That is, in the General case, the older you get, the less likely to develop motion sickness. However, the sensitivity manifests itself from birth and reaches a peak closer to ten years: if I go out to sea with his eight-year-old daughter, she will terribly suffer from pitching, while my three year old son will only rejoice.

If we talk about the primary adaptation to fluctuations of the ship those who had never been in such conditions, the addiction is starting to show after pitching 10 hours; 30 hours, the susceptibility is reduced by half, and after 80 five times. Surely you know the situation when you have just arrived on Board the guests beginning to stir, and the crew feels well, and is surprised that sea-sickness manifests itself with so little pitching. The fact that they are already pricecialis, while yet.

All this affects not only the health but also on how we cope with the problems on Board. Guests on the boats are usually resting, and the team must fulfill certain responsibilities, it becomes increasingly difficult with the growth of oscillation of the vessel. However, what role is played by the size of the ship?

The international organization for standardization (ISO) asked MARIN to figure it out, and now I conduct research in this direction. Imagine that five different motor boats with length from 60 to 300 m, start simultaneously and go the same route with the same course at a speed of 12 knots (Fig. 4). A 60-metre yacht the comfort index will be significantly lower than the 300-metre liner, that is, the larger the ship the it more comfortable. However, if we allow each of these courts to choose optimal speed for them and of course, the designated pattern will no longer work, since will become a very important parameter is the variation of acceleration in time — which we call the rate of jerks.

Its impact on comfort, depending on the position of the body (a man stands or sits). I don’t understand why people pay money to ride on a roller coaster and scream for joy (for example, my daughter!), and when you experience exactly the same acceleration on Board the vessel, do not look so happy. Maybe the fact that they expect from the ride and not expect from the boat?

I once had an opportunity to evaluate the acceleration when vibrations of one yacht, and I found out that they are much higher than those on a roller coaster, that is the people on it must be very uncomfortable in pitching. I wrote about this in the report, and later met in Monaco designer of this boat, who, smiling broadly, showed it to the people.

“You gave me a good argument for sales — he told me. — Because I can provide people with a feeling as on a roller coaster!”

This example suggests that the data obtained can be used in different ways, and our goal is to give people the opportunity to choose the yacht in terms of comfort on Board: it doesn’t have to be the highest, most importantly — it needs to meet their expectations. ISO wants to learn how to measure comfort in a conditional litres per kg to define it more objectively, and this is a very difficult task, because the feeling people are subjective. Based on our research, we try to enter a yacht of the same star rating of comfort, like hotels, to standardize the psychological expectations of the people.

A similar technique is used in the automotive industry for assessing the safety of passengers. Buying a sports car, you hardly expect five-star protection for the child, and the sale of Ferrari is not falling. In the case of car security depends on where the passenger sits, and evaluated in a series of crash tests at different speeds; we’re trying to define conditional “wall” for passengers of the yacht, depending on speed and space on Board.

Conditions in different areas can vary greatly, so we are now working with typical Mediterranean and Caribbean seas excitement (Fig. 5), where 35% of the waves have a period close to five seconds. For comfort, we calculate the true angle of gravity at five points (owner’s cabin, dining room, wheelhouse, the crew accommodation, “beach club”) where people are most active. Wave height, as well as the course of the vessel, are specified arbitrarily we chose a wave of 1 m at the rate of 135°, where the combination of yaw, pitch and roll, and conducted measurements on two of the most important for recreational vessel speeds — 0 and 12 knots.

Based on the values of vertical accelerations in different parts of the vessel (Fig. 3), we can say that in the center 1/3 of the hull length from the stern of the acceleration is minimal, so there are prone to motion sickness people will feel most comfortable. This is very important, for example, in cases where the customer can choose the layout of the yacht. In the bow the master cabin, it will have a very different feel than the same cabin on midship, so two of the same design of the yacht will get a different rating.

  • MARIN works with large-scale models of vessels since 1932, and during this time there have tested more than 10 thousand buildings with different lines and almost 8 thousand propellers. The organization employs more than 400 people, and today MARIN tasks are not limited to building and testing models: the company has a media center simulating the behavior of a ship and the possibility to carry out measurements and calculations ship characteristics.

Unfortunately, we cannot directly apply the rating of comfort with cruise on the yacht, as it’s larger boats with other passengers on Board which behave differently. Operating modes of the liners can be adapted to the activity of passengers, while the super-yacht is very difficult and even impossible to predict what the owner will want to do in ten minutes and where you decide to go.

Of course, this is an oversimplification of the picture, but it’s what pushes our society. Why not go to meet him and not to offer people to assess their own level of comfort by using two buttons? We designed the app Comfort Mate, which uses acceleration sensors in mobile devices for vibration measurement, while the user assesses subjective feelings.

From these data, you can output statistics by ranking the yacht according to the degree of comfort, but while it seems useless, because people install software, play around with it in cars and airplanes, making our database appear the boat moving at a speed of 900 km/h. the Application Comfort Mate is rather an example of what we can work in this direction, but for serious research on the ship you need to install special instrumentation, and the help of volunteer boat owners does not apply here.

Our research initiative group for the ISO started a year ago and will last another two years. The result will be a specific method of calculating the index of comfort for a particular yacht that does not require special software, and the values obtained can be converted into the number of stars and objectively compare on this parameter in a different court. This will give the opportunity to people buying yachts and taking them in the Charter, to make more informed decisions.

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