When looking at the control point net in perspective view and rotating the model, one can immediately recognise a fair design. There are some important guidelines to keep in mind when modelling a surface regarding control point net fairness:

1.      You should always aim to have a regular and “fair” net. The net amplifies errors in the surface; the surface is always more fair than the net.

The advantage of using NURB surfaces in general is that even when the control points are very unfair, the resulting surface is always fairer; especially for high stiffness surfaces.

2.      The rows and columns should not overlap as this makes further fairing of the surface much more difficult.

Overlapping rows in profile view

Overlapping columns in plan view

3.      One area that is often overlooked when using Maxsurf to design a hull is the longitudinal spacing of the columns in the net. It is possible to create hard corners in Maxsurf by moving several control points close together and this characteristic is commonly used to create chines and knuckles in a design. A side effect of this is that if the columns of control points in a design are irregularly spaced the surface can show irregular rates of change of curvature. In general, try to make sure that the columns of control points in a surface change their spacing smoothly.

Poor column spacing

Good column spacing

4.      It is helpful if the rows and columns are near orthogonal, it is especially beneficial to try to keep the columns as vertical as possible since this makes manipulation in the body plan view much simpler.

Recommended control point net in Profile view

Recommended control point net in Plan view. Often it can be recommended for the curved columns to be approximately orthogonal to the centreline as well as to the outer surface edge.

Note that these are guides only and should not be considered rigid constraints (except that the net should be reasonably regular, and rows and columns should not cross other rows or columns, though they may become compacted).

Finally, continue reading the Basic Fairing Summary section.