Some Observations on the Efficiency of Wooden Blocks During Hydraulic Test and Final Docking

Abstract

At the time of hydraulic test and drydocking, there are possibilities that the bottom shell of large vessel and the foundation of dock are locally damaged.
As an example for the former, we measured the reaction in the blocks and deflection in the bottom shell, etc. at the hydraulic test of No. 3 C. O. T. (C) of 125, 000 DWT tanker in the building dock, and calculated the reaction and deflection on modelled conventional framed structure, considering the hull to be supported by springs composed of wooden blocks and foundation.
We had little defference between measurement and our calculation and it proved that our assumed calculation was correct and proper.
As an example for the latter, we have selected the case as our countermeasure against the damage (her bottom shell had partial plastic deformation by block reaction), which we experienced at the final docking of 215, 000 DWT type tanker.
We have changed our previous practice of softwood liner touched with bottom shell to the practice of sandwiching it in between hardwood blocks.
We could, consequentially, succeed to prevent any damage on and after.