Section 6 Hull Girder Deflections ABS GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT . 2004 97Hull deflection measurements can be conducted by investigating the bearing offset change from one vessel condition to another. For such a task, a strain gauge measurement combined with either the crankshaft deflection measurements or the M/E bearing reaction measurements should be applied. It would also be possible to consider M/E bedplate deflection measurements combined with the strain gauges if the accuracy of the readings can be trusted. Strain gauge method is convenient because of its consistent accuracy, and the error initially introduced will be constant throughout the repeated measurements. This is important information as the primary interest is normally in investigating the change in hull deflection from one state to another (dry dock condition vs. different afloat condition – Section 6, Figure 8), and by doing so, the constant error will be eliminated. Other methods like jack-up, optical, laser and piano wire do not have this advantage of error control. FIGURE 8 Vessel Deflections Change with Loading Condition Dry dock deflections Ballast – still water deflections Laden – still water deflections
