The boom used in both tests consisted of two segments:
each were 20 m in length and featured a skirt with a
draft of 3 m, as well as a 70 cm freeboard to provide flotation
and prevent over-topping. The skirt was made of
PVC-coated fabric and floatation was provided by filling
the top of the boom with beach balls (70 cm diameter).
To keep the skirt vertical,a 2 kg dive weight was fitted to
the bottom of the skirt every 2 m. Faster currents were
expected in Rotterdam so a chain with linear mass density
of 5 kg/m was attached to the skirt. The two segments
were joined together in a watertight manner (using
a piece of PVC fabric, duct tape and shackles) to make
one 40 m boom.
Figure 7.2 Mooring configuration. Schematic drawing of the planned mooring configuration of the booms and trawls.
METHODS
In the Azores, the boom was attached to a mooring point
on both ends. The mooring points were distanced 35 m
between each other at a depth of ~25 m. As seen in Figure
7.2, four lines were attached to each mooring point, and
these were secured to the sea bed using steel grappling
anchors. Both mooring points were fitted with a 0.5 m
diameter buoy to compensate for the downward pulling
force caused by the boom’s drag force. In Rotterdam, the
boom was attached to the Erasmus Bridge on the South
side and a floating buoy on the North side.