4.4 Conclusion: the importance of concept
In this section we have looked at how the generation of an initial concept can dominate the design decisions which are made thereafter. The amount of space available in a boat is dependent on the keel shape; the decision to try for aerodynamic perfection in an aircraft may increase the power required to fly it.
The process of generating concepts is important for two reasons.
First, it helps to define the design space (that is, the 'problem space' and the 'solution space') which may be returned to and re-examined via various iterations in the process. All details are not defined; there is still room for variation, decision and choice. This freedom identifies the design space. Of course this freedom is limited and concept design has defined the limits of this freedom at subsequent stages in design.
Second, in any practical situation it is ultimately very important to get the concept 'right'. Remember we are limited at future stages by the concept chosen. This is sometimes encapsulated in a piece of design 'wisdom' that says 70–80 per cent of product costs are determined at the concept stage. This is not to say that generating concepts costs a lot in time and money, but that as the design progresses to manufacture and market there is little that can be done to influence the costs incurred. Hence the importance of reducing weak ideas early in the process.
In Section 1 I discussed various types of model, such as scale drawings, three dimensional models, and so on. How do such models assist in the definition of the 'design space'?
What type of models might be used in the conceptual design of sailing boat hulls? (Think in terms both of the form of the hull and the overall performance of the boat.)
Models assist the definition of the problem and they provide tangible ways of communicating and testing possible solutions.
In the example of sailing boat hulls there are a number of models, in the form of accepted types of hull design, which have proved themselves over many years. The designer doesn't have to start with a blank sheet of paper. Where the designer intends to use conventional materials then the problems are well known and the designer can move on to models which assist the testing of ideas.
However, where new materials or processes are involved (such as the introduction of steel or new polymers for hulls) then mathematical models may need to be used to explore the material properties – especially if they have not been used in hull construction before.
You would probably still find quite a bit of sketch modelling also going on.
Computers are now used extensively to model variant designs based on the basic principles presented in Figure 23. They can provide a capability for mathematical modelling (e.g. buoyancy testing, material weight and efficiency in the water) as well as providing images for visual evaluation and marketing.
Testing with scale models is rarely undertaken these days – they may be nice to look at but they are just not accurate enough to provide the information required for design. Sea-testing a prototype hull may also be considered part of the modelling process.
In the following sections, I'm going to look at examples of how an initial concept can be carried through to manufacture, via a prototype.