Investigation of the effect of pointed extremities on the error in determining displacement by the draft survey method for general longitudinal deformations of the ship's hull

The work investigates on 3D models of objects with simplified contours based on a parallelepiped the effect of the sharpening of the buttocks and waterlines on the error in determining the displacement by the draft study method is investigated when the hull experiences general longitudinal deformations relative to the middle part of the vessel in the form of deflection, bending and torsion during the initial landing of the vessel straight, as well as on a even keel and the absence of a construction pitch. A pontoon with the following dimensions was chosen as the object of study: the maximum length / length between the perpendiculars / width / height of the side / draft (in full load) in meters are LN/LꞱꞱ/B/H/T=85/83/16,5/3,3/2,5. The contours of the extremities were changed by the rise of the buttock lines and/or the sharpness of the waterline with by changing the coefficient of total completeness of the extremities (with a length of 0.15LN≈0.154LꞱꞱ) δ*∈[1.0...0.33]. The bending arrows of the ships' hulls were selected within the existing real relative range from 0 to 0.005 in fractions of the length of the hulls along the structural waterline. The ships were fitted in such a way that the average values of the draft scales for deformation hulls coincided with the values in the absence of general longitudinal deformations. As a result, graphical dependences of the relationship between the coefficients of hull completeness and the relative error in determining displacement by the draft survey method for general longitudinal deformations of the hull are obtained. In particular, the dependence of the influence of the sharpness of the waterline and the buttock lines at the extremities separately and their combined influence was obtained. It is found that with the general longitudinal deformation of the hull, the displacement error depends significantly less on the change in the sharpness of the buttocks than on the sharpness of the waterlines when using the draft survey method.