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34 M.S. MERDİVENCİ, A.G. AVCI, B. BARLAS

The total VDV of 12.10 ms-1.75 experienced by the crew during the trials far exceeded the action
limit of 15 ms-1.75 recommended in BS and the maximum daily dose of 21 ms-1.75 permitted by
the European Directive. The higher VDV of the first trial in comparison to that of the second
was to be expected given the increased sea state during the former. It is also interesting to note
that the total VDVs were dominated by the VDV of the Z axis and that the impacts in Y axis
had very little effect on the VDV despite the relative importance suggested by anecdotal
evidence that lateral impacts have on discomfort. This would appear to support the argument
that, although it is generally held to be measure of discomfort, based on translational
accelerations alone, VDV does not adequately represent the level of discomfort reported
onboard high-speed craft. During our cruise on 14th of April 2015 on Ağaçlı, Black Sea coast of
Istanbul, the maximum acceleration value on z direction is around 35 m/s2 which is almost 3.6
g. The real time accelerations of the cruise is given in Figure 7 and Figure 8 respectively. It can
be seen from the figures that, when the boat speed is getting high, the measured acceleration
values in z direction is getting high as expected. The properties of sea trial is given in Table 9.

20 V=26.1 km/h
15
10

5

V=6.6 km/h

0
-5

Figure 7: The first part plots of the raw accelerometer signal of z direction.

The boat travelled around the coast of Ağaçlı and during the cruise, the sea state was 1 and there
was no significant waves which would affect our acceleration measurements. We increased the
speed at every 20 seconds in first trial and additionally we have moved on a curvy line 6 times
at our second trial. Approximately 15 minutes after the start of the trial, the boat returned to the
starting point.

GiDB|DERGi Sayı 3, 2015