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In
water only your head weighs anything
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problems of floatation physics as regards the human being can be
explained by means of simple diagrams, just as SECUMAR's company
founder Jost Bernhardt did in
1958 in his basic investigations ("Der Mensch im Medium Wasser",
and in: Die Kommandobrücke, Hamburg 1958): |
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| 1
If a human being submerges himself in water, he is weightless,
i.e. he even floats with a little bit of buoyancy. By the way, clothing
hardly plays any part here, unless it has a buoyancy of its own
(e.g. as is the case with protective suits against the cold). |
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| 2 By swimming movements, e.g. by 'treading water' you
can keep yourself and your head above water in order to be able
to breathe. However, when you become exhausted or unconscious you
can't keep your head above water any more: it sinks forwards
and down - hence into the water. |
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| 3 Additional buoyancy could replace the swimming movements,
in order to keep the head above water. A buoyancy aid, as shown
here, does this for example. The buoyancy around the body, above
all in one's back and at the base of the torso is indeed able to
lift the whole person out of the water, but it leads to a reinforcing
of the tendency to tip forward and down. When one became exhausted
or unconscious, it would mean one's breathing apparatus would inevitably
go under water. Now we understand: exactly
this is why a buoyancy aid is
not a lifejacket! The task of the buoyancy aid is only
to support active swimming and is supposed to aid you when you carry
out this water sport. An active rescue function is not demanded
of it nowadays. |
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4 Only a lifejacket,
which provides for sufficient volume of buoyancy in front
of your chest, around your neck and under your chin, keeps your
head safely above water. Only such a buoyancy chamber protects
an exhausted or unconscious person from drowning. What is decisive
for the performance of such a piece of personal protection equipment
(PPE, as it is today called in accordance with standards) is the
correct position on the body, the correct distribution
of buoyancy around the head and/or shoulders, as well as sufficient
load-bearing capacity (at least 100 Newton). A buoyancy reserve
is recommendable. The new European standards classes are correspondingly
structured: the greater the demands placed on the performance
under more difficult weather and sea conditions, the more load-bearing
capacity is required, the more stabile is the position of the
ship-wrecked person in the water and the better are his chances
of survival.
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| related
Downloads: |
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The man in the aqueous element
A contribution to the problem of life-preservers |
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