Tools of the trade - CAD

The challenge of design - information wrangling

It used to be about drawing lines - now it’s about herding cats.

What is CAD?

CAD, or computer-aided-design came about because it’s hard to draw circles by hand. Now it’s more about interactive 3D visualisations, renders, annotated drawings and virtual-reality walk-throughs.

[Essential side-note on hand drawing: Quick visual communication of an idea pretty much always starts with a pencil and a blank sheet of paper. Having to slow down to fit your idea through your CAD system’s framework often just takes too long. Drawing skills are still vital.]

The power of CAD to create flexible curve and surface modelling came to the fore in the 1960’s when Pierre Bezier latched on to an idea for mathematically defining curves for designing cars for Renault. (Bezier’s curves are still widely used - including in rendering the font that you’re reading now!)

Comparing modern CAD systems to a drawing board however is like comparing grapes with Champagne - same origin, very different result. CAD is as much about managing the exploding growth of design information that needs to be tracked, version controlled and safely stored as it is creating drawings. Successful information management is now so crucial to the design process that managing data as part of your CAD process is not only logical, but essential.

Sometimes the data can’t be all in the CAD system, that’s when applying a bit of coding to the problem becomes very effective. Check out our post on coding in design for more info.

Telling a story

Design is so fundamentally about communication that being able to translate a client’s imagining into an animation or a 3D print is powerful. The ability to form ideas, to dream, iterate and then present the results with clarity to someone not versed in reading engineering drawings is extraordinary.

Technologies such as 3D printing, virtual reality and high performance render environments allow clients to understand how their ideas have been realised very early in the design process. This communication allows for fast, early design iterations at a stage in the project where the implications on cost are small and improvements can be maximised.

Parametric vs traditional CAD

CAD started off as a translation of the processes of the drawing-board; lines arcs, third-angle projection tricks. This is where much of it still is today, which is fine in some circumstances. In the right hands, using traditional CAD is a fluid and effective.

The problem is when you have to re-do something, which, let’s be honest, is most of the time.

The very nature of custom design is that it hasn’t been done before - it can be impossible to know the outcome when you sit down to create. With traditional CAD this generally means deleting swathes of work and then starting again when something fundamental has changed.

Parametric CAD allows you to capture relationships within and between components, that can automatically rebuild the model when the design intent changes.

[Another essential side note: parametric CAD is not perfect; sometimes the design intent changes so much that these relationships break, and sometimes it is just quicker to take what you’ve learned from the previous design iteration and start again. Also the ability to see how a design might be parameterised benefits from years of experience.]

A picture tells a thousand words:

A bar stool. Yes, pretty much any CAD system can do this.

Showing the seat defined by dimensions - a traditional approach.

Defining the seat by parameters allows the design to be quickly modified.

Parametric design also allows for the design of families of parts - parts that share similarities, but aren’t otherwise the same. A design family may encompass chairs of differing heights, colours, seat sizes or even number of legs.

Legs - why stop at 3?

Leg geometry defined by parameters.

This is a trivial example to introduce the idea. This becomes powerful when you can begin the detail work of a design with known uncertainties, with the assurance that once the unknowns become known, the design can be ‘regenerated’ safely, with the new information cleanly represented in the original model.

Applying these techniques at superyacht scale - in the iterative FEA of shell doors, in hullform optimisation, in wind studies of sun decks or in lighting analysis doesn’t just make the process possible, it makes it enjoyable. When clients are more able to understand the design process and outcomes, trust is developed and surprises can be avoided.

Data wrangling

The amount of data needed for successful design projects is so vast that intelligent data management is a necessary consideration of every project. Computers’ ability to create information is paralleled by their ability to destroy it at a keystroke :/

Increasingly sophisticated systems have been developed to support data management, file version tracking, change and revision management, and also to support companies where the design team is broken up geographically. These systems that help manage the product life cycle are unsurprisingly known as Product Lifecycle Management (PLM) systems, and allow for complex document management controls, as well as the complex inter-linking of design information. Their flexibility makes them necessarily complex (since no two companies’ processes are exactly alike) but also expensive. They are worth their weight in gold when needed ‘though.

And the winner is…

Both; a hybrid approach.

Most of our projects end up using a balance of both parametric and traditional CAD. Like all craft, the right tool to use is that most suited to the task. If the surface modelling in the parametric system isn’t all that is needed for the job, use the one from your traditional system and vice-versa. The main challenge arising from choosing a hybrid approach to CAD is working out how to efficiently move information between CAD systems, but that’s a discussion for another day!

The wrap

Spreadsheets aid design. PDF documents aid design. The Internet aids design. 3D modelling and visualisation tools also aid design. Bringing together the right tools to manage the challenges of bespoke design is the difference between a recorder solo and an orchestra. Modern CAD systems’ ability to manage the volumes of design information and present them as a photo-realistic rendered result is part of what makes the hard work of custom design look effortless.

I hope this has been helpful. All the best,

Nick.