Transformations are applied to visible surfaces only. Surfaces selected should form a coherent model capable of being analysed in Hydromax. This means that care should be to taken to trim intersecting surfaces where necessary and make sure that potential ambiguities such as multiple openings in the hull are resolved.

It is important that the parent model be reasonably close in form to the required final design as it is not feasible to make major changes to the search parameters before the hull starts becoming unreasonably distorted. Experience suggests that reasonable variations of Block, Prismatic or LCB are of the order of up to plus or minus 3 to 5%. These limits may be lower for vessels that have moderately high prismatic coefficients – as the prismatic increases the scope for variation seems to improve.

The parametric variation tool is ideal for making small adjustments from a suitable parent design. It is not intended to be used for gross design modifications. The scope for parameter variation is greatest for designs that are not extreme; as the design and its form parameters become more extreme the scope for parametric variation is reduced.

Because of the non linear nature of the transformation and the requirement that fairness be maintained, it is often found that long fore and aft overhangs distort proportionally more than the underwater body. The shorter the overhangs of the vessel are the less noticeable this effect will be.

It is not possible to constrain Displacement, Length, Beam and Draft simultaneously; the maximum permissible is any three parameters out of the four available.