Specifications
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5.9 Hull and hatchcover
Hull and hatchcover form a watertight compartment that provides buoyancy and houses
batteries, sensors and electronics. This section only describes all items on the exterior and some
basic functions in the interior of the compartment. Separate sections are devoted to battery
compartments, electronics unit, motion sensors and temperature sensor.
5.9.1 Packing frame and buoy weights
For safe transportation the buoy must be packed in the packing frame in which it arrived
originally. It is advisable to leave the buoy in its packing frame during all transport. To take the
buoy out of the frame, just remove one of the poles and slide the buoy out of the frame. Use a
hoisting crane to support the buoy. For handling and transport see Table 5.9.1 with dimensions
and weights.
Table 5.9.1. Buoy and packing frame weights and dimensions.
0.4 m 0.7 m 0.9 m
Buoy
DWR-G DWR-MkIII DWR-G/
WR-SG
WR-SG DWR-MkIII/
DWR-G
Approximate buoy weight
including batteries,
antennas and chain
( AISI316 and Cunifer10 (Cu) )
17 Kg
105 Kg
111 Kg (Cu)
95 Kg
101 Kg (Cu)
150 Kg
161 Kg (Cu)
225 Kg
236 Kg (Cu)
Packing frame weight * 35 Kg 45 Kg
Frame height * 1.20 m 1.42 m
Frame width/buoy width
(including fender)
* 0.78 m 1.0 m
Buoy height (as transported,
mooring eye-hatchcover handles)
0.50 m 0.73 m 0.95 m
* The 0.4 m GPS buoy is not packed in a frame
For testing purposes it may be helpful to put or leave the buoy in the frame, e.g. pitch, roll
and horizontal accelerometers tests. This setup is not suitable for testing the fluxgate compass as
the metal parts of the packing frame can influence the compass reading.
5.9.2 Hull, Cunifer10, corrosion and painting
The hull has three functions: providing buoyancy and protecting the sensors and electronics
inside from water and impacts. While doing so it faces three enemies: ship collisions, corrosion
and fouling.
At 0.9 m diameter the buoyancy force initially increases 62 N with every cm of
immersion. Just before full immersion the buoyancy of a 0.9 m diameter hull including chain is
1630 N. For loads on the buoy larger than this threshold the buoy will sink.
Datawell hulls are designed to withstand head-on collisions. Ship collisions typically are
not fatal although the buoy will be dented. If the propeller screw hits the buoy, then the buoy
will be damaged but even then it can often be repaired. The hull of the Waverider stays
watertight even if largely deformed. Cunifer10 (copper-nickel alloy) is also available as hull
material, see below. Though its strength is less than that of stainless steel, it can take large
deformations.
It is known that the corrosion risk of unprotected AISI316 stainless steel is to a certain
degree unpredictable. Pitting is the predominant form of observed corrosion. However,
sacrificial anodes on the stabilizing chain below the hull will mainly take care of corrosion of
the AISI316 stainless steel hull. The use of sacrificial anodes is strongly recommended, even for
painted buoys. Without protecting anodes, blistering paint or pinholes in the paint cause
accelerated local pitting of the AISI316 stainless steel. Pitting has been found to be aggravated
by the use of paints containing chlorinated hydrocarbons, acids or reducing agents.
Depending on local conditions such as water temperature and water quality, anti-fouling
paint may be necessary. Severe fouling may affect the mooring performance due to increased