Preliminary Experimental Research on Righting Performance
of Lifejackets with Clothing
Keiko Miyazaki
1, and Susumu Ota
11National Maritime Research Institute, Japan
Abstract
In July 2017, the Marine Accident Investigation Branch of the United Kingdom reported an accident of a fishing vessel resulting in the fatalities of three seafarers. These seafarers were found in a face-down position, while they were wearing lifejackets certified in accordance with the International Conventions for the Safety of Life at Sea and the International Life-saving Appliance (LSA) Code, so-called “SOLAS lifejackets”. Following the research initiated by this accident, the European Commission submitted two documents, emphasizing the necessity of a new righting test method for lifejackets with clothing. The Maritime Safety Committee, at its 101st session, considered these documents and agreed to review the LSA Code and the Revised Recommendation on testing of life-saving appliances, in respect to the in-water performance of SOLAS lifejackets, taking into account that the current righting test of a SOLAS lifejacket is conducted only with a swimming costume.
In order to develop robust testing methods for the righting of lifejackets with clothing, the righting phenomenon of lifejackets with clothing should be examined. The purposes of our preliminary research are to evaluate the repeatability of righting tests with clothing and to obtain fundamental information on such tests. For these purposes, we conducted righting tests with clothing using three human test subjects under various conditions and compared the results of tests conducted just after entering the test basin with dry clothing in order to evaluate the repeatability of the tests. In addition, we repeated the righting tests using the same clothing without getting out of the test basin in order to obtain further information for reference. We further measured the forces required to dive into the water with and without clothing in order to roughly specify the buoyancy of clothing under lifejackets. The test results indicated that righting tests with clothing were sensitive to slight differences in clothing conditions, human actions and time elapsed. Our study showed that the righting test with clothing had poor repeatability and standardization of clothing could not solve the poor repeatability of the righting test with clothing.
Keywords: lifejacket, righting performance, righting time, dry clothing, clothing condition, repeatability, human test
subject
1. INTRODUCTION
In July 2017, the Marine Accident Investigation Branch of the United Kingdom reported an accident of a fishing vessel resulting in the fatalities of three seafarers (1). These seafarers were found in a face-down position and the coroner reported that the deaths were caused by drowning, while they were wearing lifejackets certified in accordance with the International Conventions for the Safety of Life at Sea (SOLAS Convention) and the International Life-saving Appliance (LSA) Code, so called “SOLAS lifejackets”. Taking the report into account, the United Kingdom Maritime and Coastguard Agency (MCA) and others carried out research on the righting performance of SOLAS lifejackets under various clothing conditions and found that the addition of more clothing had a detrimental impact on the righting performance of the lifejacket (2). The European Commission subsequently submitted two documents emphasizing the necessity of a new righting test method for
1Correspondence to Keiko Miyazaki, Center for International Cooperation, National Maritime Research Institute, National Institute of Maritime, Port and Aviation Technology, 6-38-1 Shinkawa, Mitaka-shi, Tokyo 181-0004, Japan; E-mail: miyazaki-k@m.mpat.go.jp
lifejackets with clothing. The Maritime Safety Committee (MSC), at its 101st session, considered these documents and agreed to review the LSA Code and the Revised Recommendation on testing of life-saving appliances, i.e. resolution MSC.81(70), in respect to the in-water performance of SOLAS lifejackets, taking into account that the current righting test of a SOLAS lifejacket is conducted only with a swimming costume.
We considered that the amount and the distribution of air trapped in clothing are the main causes affecting the righting phenomenon. Kawashima, et al. (3) mentioned the lack of buoyancy of the rubber-coated raincoats worn under lifejackets by seafarers. Murayama, et al. (4) mentioned the disadvantage of wet cotton underwear for thermal insulation which is worn under lifejackets. Amagai et al. (5)(6) examined the buoyancy of life-vests which might be worn by seafarers and the heaving of a man with the life vest in regular waves. Nakahashi et al. (7) clarified a
subjective evaluation of outer clothing which might be worn under lifejackets. Martin J. Barwood, et al. (8) investigated the buoyancy of a combination of work suits and lifejackets. Conor V MacDonald, et al. (9) examined the righting time of infant lifejackets and pointed out the difficulty of using infant test subjects.
When a person wears clothing under a lifejacket, air can be trapped between the human body and the lifejacket, and consequently can have an impact on the righting phenomenon, including the righting time. This may be the reason why righting tests for lifejackets are conducted only with a swimming costume in accordance with resolution MSC.81(70). In order to develop robust testing methods for the righting of lifejackets, the righting phenomenon of lifejackets with clothing should be examined.
The purposes of our preliminary research are to evaluate the repeatability of righting tests with clothing and to get fundamental information on such tests. For these purposes, we conducted righting tests with clothing using three human test subjects under various conditions and compared the results of tests conducted just after entering the test basin with dry clothing in order to evaluate the repeatability of the tests. In addition, we repeated the righting tests using the same clothing without getting out of the test basin in order to obtain further information for reference. We further measured the forces required to dive into the water with and without clothing in order to roughly specify the buoyancy of clothing under lifejackets.
2. METHOD FOR RIGHTING ETSTS
2.1 Outline of the tests
Righting tests of three lifejackets have been carried out using three human test subjects according to paragraph 2.8.5 of resolution MSC.81(70), which is reproduced in the appendix to this article, except clothing and number of repetitions of the tests with clothing.
2.2 Specifications of lifejackets
The specifications of the lifejackets donned by the human test subjects are given in table 1. Figure 1 shows photos of the lifejackets.
Table 1 Lifejackets buoyancy Lifejacket Measured buoyancy (N)
1 203
2 203
3 124
Lifejacket 1 Lifejacket 2 Lifejacket 3 Figure 1 Appearance of lifejackets
2.3 Specifications of human test subjects
The specifications of the human test subjects are given in table 2. Figure 2 shows these human test subjects, expressed as “H.T. Subjects”. Hereafter, “H.T. subject” or “H.T.S.” is used in the figures and tables. Table 3 indicates the weight and height ranges of the human test subjects according to “Table 2.1 - Test subject selection for adult lifejackets” of resolution MSC.81(70). In this table, “1” denotes that at least one subject should be selected from the range and “X” denotes that sufficient additional subjects should be selected from the range when selecting 12 human test subjects for the type approval tests. Although human test subject M was out of the weight and height range specified by resolution MSC.81(70), being out of the range does not create any problems in terms of the evaluation of the repeatability of righting performance. This preliminary research had the approval in accordance with the ethics rules on the experiments of human in our institute. Then, informed consent was obtained from each participant prior to the tests in accordance with the rules.
2.4 Specifications of clothing
The specifications of clothing worn by the human test Table 2 Human test subjects
Human test
subject Male/Female Height (m) Weight (kg)
L Male 1.84 75.6
M Male 1.77 56.1
S Female 1.59 41.9
H. T. Subject L H. T. Subject M H. T. Subject S Figure 2 Human test subjects
Table3 Height and weight range of test subjects * Height range (m) Weight range (kg) 40- 43 43- 60 60- 70 70- 80 100 80- 100- 110 110- 120 >120 < 1.5 1 X X X 1.5 - 1.6 H.T.S.S X 1 1 X X 1.6 - 1.7 X X 1 X X 1.7 - 1.8 H.T.S.M X X 1 X X X 1.8 - 1.9 X H.T.S.L X X 1 1 X > 1.9 X X X 1
Note * Extracted table from resolution MSC.81(70) table 2.1 - test subject selection for adult lifejackets
subjects are shown in table 4. We used long-sleeved cotton shirts, woollen sweaters and waterproof jackets of two types, type I and type II; both were made of nylon. The hem and the collar of type I jackets were loose. On type II jacket, the hem was squeezed and the collar was tight. Water pressure resistances were different, but it did not make any difference in terms of permeation of water in the righting tests.
The woollen sweaters were got dry cleaning, and both the long-sleeved shirts and the waterproof jackets were washed and just dried, prior to the tests for respective combinations of the human test subjects and the lifejackets. Neither trousers nor shoes were worn in order to simplify the clothing conditions for obtaining basic information.
Six sets of the aforementioned clothing were prepared for each human test subject to investigate the repeatability of righting time of the human test subjects just after entering the test basin with dry clothing, for the reason that the righting tests just after entering the test basin with dry clothing are deemed representative tests with clothing.
Figures 3 shows the example of clothing for a human test subject. The waterproof jacket shown in the bottom right figure was worn under different conditions. Table 5 specifies the clothing conditions for the tests including the conditions of a swimming costume only.
Figures 4-1 to 4-4 are photos of lifejackets with human test subject M. Figure 4-1 is the photo of lifejacket 1 with a swimming costume only. Figures 4-2 to 4-4 are photos of lifejackets 1 to 3 under clothing condition B. The appearance under clothing condition C is almost the same as that under clothing condition B.
2.5 Control experiment
As control experiments, the righting tests of lifejackets only with a swimming costume, i.e. under clothing condition A, were conducted according to paragraph 2.8.5 of resolution MSC.81(70). In these tests, the human test subject: first enters the test basin; second, conducts the righting tests six times, and gets out of the test basin. As the buoyancy of the swimming
Table 4 Clothing
Clothing Composition Subject H. T. weight (g) Dry Shirt
(long-sleeved) 100 % cotton
L 235
M 204
S 170
Woollen sweater 80% wool and 20 % nylon
L 415 M 394 S 354 Waterproof jacket, Type I *1 Nylon, water pressure resistance 15,000 mm L 270 M 265 S 249 Waterproof jacket, Type II *2 Nylon, water pressure resistance 50,000 mm L 257 M 243 S 198
Note *1 The hem and the collar are loose.
*2 The hem is squeezed, and the collar is tight
Shirt (long sleeved) Woollen sweater
Waterproof jacket Type I (the hem and the collar are
loose)
Waterproof jacket Type II (the hem is squeezed and the collar is tight) Figure 3 Example of clothing
Table 5 Clothing conditions Clothing
condition Item
A No clothing other than swimming costume B waterproof jacket Type I and swimming costume Shirt (long-sleeved), woollen sweater, C waterproof jacket Type II and swimming costume Shirt (long-sleeved), woollen sweater,
Figure 4-1 Photo of H. T. subject M with lifejacket 1 under clothing condition A
Figure 4-2 Photo of H. T. subject M with lifejacket 1 under clothing condition B
Figure 4-3 Photo of H. T. subject M with lifejacket 2 under clothing condition B
Figure 4-4 Photo of H. T. subject M with lifejacket 3 under clothing condition B
costume is negligible, six righting tests can be conducted continuously under the same conditions. Figure 5 is a photo of the test basin.
2.6 Detailed test procedure with clothing
The righting tests were conducted with the aforementioned clothing, i.e. under clothing conditions B and C. The test using the same clothing was repeated 18 times to obtain additional data on the fluctuation of righting time owing to the repetition of righting. In the repeated test, after the 12th righting test, the human test subject deflated the clothing with their hands, in other words, the human test subject removed air trapped in the clothing by tamping down the surface of the lifejacket.
The detailed procedure of the test with clothing was as follows:
.1 put the dry clothing and lifejacket on over the swimming costume;
.2 enter the test basin;
.3 conduct the righting test 12 times; .4 deflate the clothing with the hands;
.5 conduct the righting test six more times; and .6 get out of the test basin and take off the clothing and
lifejacket.
In the righting test, the righting time was measured in accordance with paragraph 2.8.5 of resolution MSC.81(70), namely, the period from the time when the test subject's feet are released (starting time) to the time when the mouth of the test subject comes clear of the water (end time). Each righting test was aborted at 15 seconds from the starting time for the safety of the human test subjects, and “righting failed” was recorded.
3. RESULTS OF TESTS
3.1 Results of tests with swimming costume only
Figures 6-1 to 6-3 show the results of control experiments under clothing condition A, i.e. wearing a swimming costume only. The ordinates and the abscissas indicate the righting time in seconds and the test number, i.e. 1 to 6, respectively.
In these figures, the circle, square and triangle marks denote the direction of righting, which are respectively: “turning around head to foot axis”; “turning around side to side axis” and “diagonal turning”. “Righting failed” is expressed with the rhomboidal mark at 15 seconds. The results of the tests under clothing conditions B and C are shown in the same way.
3.2 Results of tests conducted just after entering
the test basin with dry clothing
Through the righting tests with clothing, we observed that air was trapped by the clothing under the lifejackets. It is apparent that trapped air affects the righting phenomenon including the righting time. We obtained 18 righting times through testing continuously as mentioned in section 2.6. The results of the tests indicate the general tendency that the righting time becomes
shorter when test number, i.e. 1 to 18, increases, namely, deflation progresses. From this point of view, the representative righting time with clothing should be the righting time of the human test subject just after entering the test basin with dry clothing. Hereafter, these tests are expressed as “the first tests” and the tests just after the first tests are expressed as “the second tests”, and so on. Six righting times of the first tests were obtained under clothing conditions B and C for respective combinations of the human test subjects and the lifejackets, by preparing six sets of the clothing for each human test subject.
Figures 7-1 to 7-6 show the righting times of the first tests for three human test subjects under clothing conditions B and C. In these figures, the ordinates indicate the righting time in seconds and the abscissas indicate the number of the clothing set, which merely clarifies that different sets of clothing were used. Therefore, the line graphs do not indicate tendency but are just for information. Table 6 gives the average righting time discarding the highest and lowest times. In the table, “failure” means the average time is over 5 seconds.
Figure 6-1 Results of tests lifejacket 1 with three H.T.
subjects under clothing condition A
Figure 6-2 Results of tests lifejacket 2 with three H.T.
subjects under clothing condition A Legend
: turning around head to foot axis : turning around
side to side axis : diagonal turning : righting failed
Figure 6-3 Results of tests lifejacket 3 with three H.T.
subjects under clothing condition A
Table 6 Righting time (average of 4 data in 6 data*) in seconds under clothing condition B and C
Lifejacket 1 Lifejacket 2 Lifejacket 3 Clothing
condition B C B C B C
H.T. subject L 3.7 3.7 2.5 2.5 4.2 4.0 H.T. subject M 3.4 4.0 2.6 2.9 failure failure H.T. subject S failure failure 1.8 failure failure failure Note*: Highest and lowest times discarded in accordance with
3.3 Results of tests repeated without changing
clothing
Figures 8-1 to 8-6 show the results of the tests of lifejacket 1, with respective human test subjects under clothing conditions B and C. In these figures, the ordinates indicate the righting time in seconds and the abscissas indicate the test number, i.e. from the 1st test to the 18th test. In these figures, six colours are used for marks and lines for the purpose of identifying the series of tests conducted without changing clothing. The directions of turning, which are denoted by a circle, square and triangle in these figures, varied during the test.
In terms of lifejackets 2 and 3, the general tendency was similar to lifejacket 1. For example, figure 9 shows the results of the tests of lifejacket 2 with human test subject S under clothing condition C, and figure 10 shows the results of the tests of lifejacket 3 with human test subject M under clothing condition B.
4. DISCUSSION
4.1 Results of tests conducted just after entering
the test basin with dry clothing
In terms of the repeatability of righting tests with clothing, it
is necessary to keep the same clothing conditions. Therefore, it is suitable to compare the righting times of the first tests, where the intended clothing conditions are the same.
Figures 7-1 to 7-3 show the results under clothing condition B and figures 7-4 to 7-6 show the results under clothing condition C of the first tests. As shown in these figures, there were differences between the results of the tests under clothing conditions B and C. Furthermore, by comparing figures 7-2 and 7-5, it is observed that the difference in the clothing conditions clearly affects the success or failure of righting. Concretely speaking, as indicated by the results of the tests for lifejacket 2 with human test subject S in table 6, the average righting time under clothing condition B was 1.8 sec, while the righting failed in the tests under clothing condition C, that is, the turning had not happened during the test period of 15 seconds under clothing condition C. Therefore, it can be said that slight differences in clothing, i.e. open/closure of hem and collar of the jacket, clearly affected the results of the tests. This fact implies that open/closure of hem, sleeve and collar will affect righting times even though the same clothing is used. That is to say that it may not be sufficient to specify the clothing in detail to ensure the reproducibility of the tests with clothing.
Figure 7-1 Results of the first righting tests of lifejacket 1 with three H.T. subjects
under clothing condition B
Figure 7-2 Results of the first righting tests of lifejacket 2 with three H.T. subjects
under clothing condition B
Figure 7-3 Results of the first righting tests of lifejacket 3 with three H.T. subjects
under clothing condition B
Figure 7-4 Results of the first righting tests of lifejacket 1 with three H.T. subjects
under clothing condition C
Figure 7-5 Results of the first righting tests of lifejacket 2 with three H.T. subjects
under clothing condition C
Figure 7-6 Results of the first righting tests of lifejacket 3 with three H.T. subjects
under clothing condition C
: H. T. Subject L : H. T. Subject M : H. T. Subject S Lifejacket: 1 Clothing cndtn: B 0 5 10 15 R ight ing t im e [s e c] 1 2 3 4 5 6 Clothing No. : H. T. Subject L : H. T. Subject M : H. T. Subject S Lifejacket: 2 Clothing cndtn: B 0 5 10 15 R ight ing t im e [s e c] 1 2 3 4 5 6 Clothing No. Lifejacket: 3 Clothing cndtn: B 0 5 10 15 R ight ing t im e [s e c] 1 2 3 4 5 6 Clothing No. : H. T. Subject L : H. T. Subject M : H. T. Subject S : H. T. Subject L : H. T. Subject M : H. T. Subject S Lifejacket: 1 Clothing cndtn: C 0 5 10 15 R ight ing t im e [s e c] 1 2 3 4 5 6 Clothing No. : H. T. Subject L : H. T. Subject M : H. T. Subject S Lifejacket: 2 Clothing cndtn: C 0 5 10 15 R ight ing t im e [s e c] 1 2 3 4 5 6 Clothing No. : H. T. Subject L : H. T. Subject M : H. T. Subject S Lifejacket: 3 Clothing cndtn: C 0 5 10 15 R ight ing t im e [s e c] 1 2 3 4 5 6 Clothing No.
Figure 8-1 Results of tests of lifejacket 1 with H.T. subject L under clothing
condition B
Figure 8-2 Results of tests of lifejacket 1 with H.T. subject M under clothing
condition B
Figure 8-3 Results of tests of lifejacket 1 with H.T. subject S under clothing
condition B
Figure 8-4 Results of tests of lifejacket 1 with H.T. subject L under clothing
condition C
Figure 8-5 Results of tests of lifejacket 1 with H.T. subject M under clothing
condition C
Figure 8-6 Results of tests of lifejacket 1 with H.T. subject S under clothing
condition C
Figure 9 Results of tests of lifejacket 2 with H.T. subject S under
clothing condition C Figure 10 Results of tests of lifejacket 3 with H.T. subject M under clothing condition B
Figures 7-3 and 7-4 imply that there are differences under the same clothing conditions. We conducted the righting tests to keep the same donning procedure, the same actions of the human test subjects and the same elapsed time. However, there is a possibility that slight differences occurred in the compression of the clothing by the lifejackets, the quickness of the test or actions of the human test subjects. Such slight differences also affect the reproducibility of the righting tests of lifejackets with clothing.
4.2 Results of the first and the second tests under
clothing conditions B and C
Figures 8-1 to 8-6, 9 and 10 indicate that the results of the tests indicate a general tendency for the righting time to become shorter when the deflation progresses. These figures also indicate that the righting tests with clothing would be sensitive to the time elapsed. In figure 9, in four out of six cases the first righting test failed, and the second righting test succeeded. On the 13th test in figure 10, the righting time increased and the turning direction 0 5 10 15 3 6 9 12 15 18 R ight ing t im e [s e c] Test No. H. T. Subject: L Clothing cndtn: B R ight ing t im e [s e c] Test No. H. T. Subject: M Clothing cndtn: B 0 5 10 15 3 6 9 12 15 18 R ight ing t im e [s e c] Test No. H. T. Subject: S Clothing cndtn: B 0 5 10 15 3 6 9 12 15 18 R ight ing ti m e [s e c] Test No. H. T. Subject: L Clothing cndtn: C 0 5 10 15 3 6 9 12 15 18 R ight ing t im e [s e c] Test No. H. T. Subject: M Clothing cndtn: C 0 5 10 15 3 6 9 12 15 18 R ight ing t im e [s e c] Test No. H. T. Subject: S Clothing cndtn: C 0 5 10 15 3 6 9 12 15 18
changed. This phenomenon implies that the distribution of air trapped in clothing affects the righting phenomenon.
The results of the first and second tests with clothing were also compared in order to investigate the robustness of the righting test with clothing, against actions of a human test subject and time for measurement, taking into account that air trapped in clothing may be gradually deflated in the course of tests repeated with one set of clothing and without getting out of the test basin, depending on various conditions; for example, type of clothing and the tightness of lifejackets, etc.
Table 7 shows the result of comparison. In this table, the results of the first and the second tests were classified into the following four categories:
Success/Success: righting succeeded in both the first and the second tests;
Failure/Success: righting failed in the first tests and righting succeeded in the second tests;
Failure/Failure: righting failed in both the first and the second tests; and
Success/Failure: righting succeeded in the first tests and righting failed in the second tests.
Table 7 gives the number of cases of respective categories. This table shows that the righting rarely failed in the second tests when the righting succeeded in the first tests and that there were cases where the righting succeeded in the second tests when the righting failed in the first tests. These results imply that some changes in the test conditions increase the possibility of the success of righting in the second tests even in a short period of time. The escape of air trapped in clothing would be one of the factors influencing the test even though the amount of the escaped air seems small.
Figure 11 shows the histogram of the difference between the first and the second righting times, i.e. the righting time in the first test minuses the righting time in the second test, of “Success/Success” cases of the tests for all three lifejackets. The ordinate and the abscissa indicate the number of cases and the range of difference in the righting times in seconds. The range “A to B” in the figures means “equal to or greater than A and less than B”. As indicated in the figure, the second righting time was shorter than the first one in 59 cases out of 69 cases (86%). The figure also implies that an escape of air trapped in clothing may shorten the righting time with clothing even in a short period when some actions are taken by a human test subject.
Table 7 Number of cases of respective categories on pass and fail of the first and the second tests under clothing
conditions B and C
First/Second Lifejacket 1 Lifejacket 2 Lifejacket 3 Total No. of cases
Success/Success 26 30 13 69
Failure/Success 5 4 6 15
Failure/Failure 5 2 16 23
Success/Failure 0 0 1 1
Figure 11 Histogram of difference between the first and the second righting times, other than failed cases, under clothing conditions B
and C for all three lifejackets (Success/Success cases only)
5. BUOYANCY MEASUREMENT
In order to roughly specify the buoyancy owing to clothing, i.e. the buoyancy of air trapped between the human body and the lifejacket, buoyancy measurements were conducted with human test subject M using all three lifejackets, apart from the righting tests. For this purpose, the forces required to dive into the water with clothing were measured by pulling the handle of the weighing instrument set upside down at the bottom of the test basin. Such forces without clothing were also measured. Table 8 gives the measured forces. The readable unit of the weighing instrument is 0.5 kgf. To determine the buoyancy owing to clothing, the difference between these forces with and without clothing was calculated. Table 9 gives the approximate buoyancy owing to clothing under the respective conditions.
As given in table 9, the buoyancies owing to clothing were around 10 to 30 N. The buoyancies owing to clothing with respective lifejackets were different. Though it cannot be said based on a single test, the buoyancies owing to clothing may vary in the plural tests using the same clothing and lifejacket depending on the tightening of strings etc. Such variety of the buoyancies owing to clothing may lead to inaccuracy of righting tests.
Roughly speaking, the buoyancies owing to clothing were one digit lower than the buoyancies of lifejackets mentioned in table 1. On the other hand, the increase of buoyancy owing to clothing had an adverse effect on the righting performance.
6. CONCLUSION
The results of the tests indicated that righting tests with clothing would be sensitive to minor differences in test conditions, such as opening/closure of the hem and collar of a jacket. It can further be said that righting tests with clothing would likely be affected not only by slight differences in types of clothing but also by donning procedures such as the compression of clothing by lifejackets the use of retention devices, and by the actions of human test subjects prior to the
N o. o f c a se s 0 5 10 15 30 25 20
Range of difference between the first and the second turning times
-1 t o -0 .5 s e c. -0 .5 t o 0 s e c. 0 t o 0 .5 s e c. 0 .5 t o 1 s e c. 1 t o 1 .5 s e c. 1 .5 t o 2 s e c. 2 t o 2 .5 s e c. 2 .5 t o 3 s e c. 3 t o 3 .5 s e c. 10 cases 59 cases
commencement of a righting test, e.g. actions for entry into the test basin. The time elapsed also affects the righting test with clothing.
Our study showed that the righting test with clothing had poor repeatability and standardization of clothing could not solve the poor repeatability of the righting test with clothing. Our study also implies that the distribution of air trapped in clothing affects the righting phenomenon.
The righting performance of lifejackets with clothing is important, taking into account the accident mentioned in section 1. Robust righting test methods should be developed to improve the poor repeatability of the righting test with clothing. We plan to develop a stability calculation programme corresponding to the righting test of lifejackets with clothing, to investigate the test results further and try to develop new righting test methods.
Table 8 Forces required to dive into the water Clothing
condition
Lifejacket 1* Lifejacket 2* Lifejacket 3 Scale reading [kgf]
A 13.0 12.0 12.5
B 16.0 13.0 15.0
C 16.0 missing 14.5
Note*: H.T. subject M used divers’ weights to compensate the large buoyancy of the lifejackets.
Table 9 Approximate buoyancy owing to clothing [N] Clothing condition Lifejacket 1 Lifejacket 2 Lifejacket 3
B 30 10 25
C 30 missing 20
7. ACKNOWLEDGMENT
These tests were carried out as a part of a research project of the Japan Ship Technology Research Association (JSTRA) funded by the Nippon Foundation. The righting tests of lifejackets were conducted with the cooperation of Research Institute of Marine Engineering. Ms Reiko Kikuchi proofread this paper. The authors express gratitude to all the persons concerned.
8. REFERENCE
1) Marine Accident Investigation Branch of the United Kingdom, Report on the investigation of the foundering of the fishing vessel Louisa SY30 while at anchor off the Isle of Mingulay in the Outer Hebrides on 9 April 2016 resulting in three fatalities, Very serious marine casualty report No. 17/2017 (2017)
2) IMO meeting document, MSC 101/INF.3, Work programme - Information in support of a review into the in-water performance of SOLAS lifejackets (2019), (https://www.transportstyrelsen.se/contentassets/023c372 9a76b4511b67cd5fefa2b884f/101-inf3.pdf)
3) Kawashima, et al., Experimental Study about Men Falling Overboard with Fishermen’s Protective Clothing, Journal of Japan Institute of Navigation 64 (1981) pp. 187-193 (in Japanese)
4) Murayama, et al., Relationship between Human Heat Retaining and Clothes at Marine Disaster, Journal of Japan Institute of Navigation 87 (1992) pp. 9-20 (in Japanese) 5) Amagai, et al., A Research for Fundamental Factors on the
Life Vest for Fishermen, Journal of Japan Institute of Navigation 92 (1995) pp. 283-289 (in Japanese)
6) Amagai, et al., On the Heaving of a Man with Life Vest in Regular Waves, Journal of Japan Institute of Navigation 94 (1996) pp. 35-42 (in Japanese)
7) Nakahashi, et al., Functional Design and Evaluation of Onboard Worksuit during Fishing, Journal of Japan Institute of Navigation 95 (1996) pp. 201-210 (in Japanese) 8) Martin J. Barwood, et al., Inherent Work Suit Buoyancy Distribution: Effects on Lifejacket Self-Righting Performance, Aviation, space and environmental medicine 85(9) (2014)
9) Conor V MacDonald, et al., In-Water Performance of Infant Lifejackets: Freeboard Height and Self-Righting Time: A Failure, Journal of Ergonomics 6(6) (2016)
9. AUTHOR’S BIOGRAPHY
Keiko Miyazaki: she received a Ph.D. degree in engineering from Yokohama National University in 1999 and is presently the deputy director of Centre for International Cooperation, National Maritime Research Institute, National Institute of Maritime, Port and Aviation Technology. Japan Institute of Navigation member.
Susumu Ota: he received a Ph.D. degree in Engineering from the University of Tokyo in 2003 and is presently the director of Centre for International Cooperation, National Maritime Research Institute, National Institute of Maritime, Port and Aviation Technology. Japan Institute of Navigation member.
Appendix
Extracted righting test procedure from resolution MSC.81(70) Righting tests
2.8.5 Each test subject should assume a prone, face down position in the water, but with the head lifted up so the mouth is out of the water. The subject's feet should be supported, shoulder width apart, with the heels just below the surface of the water. After assuming a starting position with the legs straight and arms along the sides, the subject should then be instructed in the following sequence to allow the body to gradually and completely relax into a natural floating posture: allow the arms and shoulders to relax; allow the legs to relax; and then the spine and neck, letting the head fall into the water while breathing out normally. During the relaxation phase, the subject should be
maintained in a stable face down position. Immediately after the subject has relaxed with the face in the water, simulating a state of utter exhaustion, the subject's feet should be released. The period of time until the mouth of the test subject comes clear of the water should be recorded to the nearest 1/10 of a second, starting from when the subject's feet are released. The above test should be conducted for a total of six times, and the highest and lowest times discarded. The test should then be conducted for a total of six times in the RTD and the highest and lowest times discarded.
Date received Mar. 31, 2020 Date revised Nov. 17, 2020 Date accepted Dec. 12, 2020
