June 2014: CAD, CNC, 3D Scanning and Windsurf, Surf & SUP Design and Manufacture

Traditionally, boards (windsurf, surf, kite or paddleboards for example) were designed on paper and shaped by hand, or even shaped by eye and ‘feel' whereby the shaper knew what they were looking for. The process emphasised the skill of the shaper - creating a ‘good’ board was as much an art as it was a science, and really determined a 'really good' shaper from a 'good' one. 

Some would argue that, in the early days as well as today, shaping was more of (or at least as much of) an art than a science – so much applicable design knowledge was in the designers head, and transferring it to a shaped blank depended on the shapers skill as a craftsman.

CAD and its influence on windsurf board design

Repetition – in other words manufacturing custom boards of the same design consistently so that if someone said “I’d like to buy the same board as that guy”, then they’d get the same board and with it the same performance and feel. However this bought issues – designers took steps to ensure they could replicate characteristics from one board to the next using a variety of methods including patterns and templates – e.g. rail templates, rocker jigs and specific measurements such as length, width, mast-track, fin-box and foot-strap placement (rocker jigs would be used to set a boards overall rocker, or how much curve was built into the bottom of the board when you look at the board from the side - see diagram below demonstrating rocker and rail shape)

This concept worked more often than not (to a point), but it was entirely possible that you could use two boards, of theoretically identical design, yet get a completely different result.

The reason for this most likely came down to hand shaping the blank and hand building the board – despite best intentions, the latest blank would be subtly different in terms of shape, and these differences would be exacerbated (usually exponentially) during construction. 

To try and minimise this syndrome and introduce a measure of consistency and repetition in shape, designer Kevin Trotter started using CAD software, in particular Maxsurf,  to create outline and rocker jigs, and design boards in the 1980’s. This resulted in ‘fair’ curves, consistent rockers and symmetrical boards, and was the first application of CAD technology to the design of windsurf boards.

Through the 80’s and 90’s, not much changed in terms of the fundamental approach to shaping and building custom windsurf boards – of course there were improvements in technique both in terms of shaping and construction – but essentially it was all done in the same way it had been, just better.

As well as the techniques of construction developing, a repository of design knowledge was developing that contributed directly to the ongoing drive towards repeatability, incremental changes and improvement.

The introduction of CNC 

In 1996 Styrotech took the next step and extended the CAD work that’d been done making templates, outlines and rocker jigs to shaping the decks and bottoms of board blanks using a 3-axis CNC machine (as per the image left).

The combination of CAD and CNC gave the designer the ability to merge multiple different curves, on different axes, into a smooth, fair shape. What's more, by using a CNC machine, it was possible to precisely re-create these shapes on a board blank, and do it again and again - repition and accuracy.

The first CNC shaped boards required the rails be hand shaped and the blanks hand finished, however, given the board was milled (cut) ‘on a machine’ it was symmetrical, fair and true to the original. At this point features (such as the hole in the deck for the mast-base block, and the hole for the fin box) began to be cut into the blank, and this had twofold benefits – it saved construction time (hence reducing cost), and improved accuracy.

Extending what CNC could do

The applications and capabilities of CAD software, in particular Solidworks, developed quickly in the late 1990’s and early 2000’s such that it became possible to design all aspects of a board, (rocker, rails, vee, concaves etc. and all interrelating measurements) in its entirety using CAD (Solidworks & Maxsurf).

Previously CAD couldn’t do all this at once, in the same file so, when you could design a board from start to finish using one CAD file, it was a bit of a “hallelujah” moment.  But it was now possible to take it further – a 5-axis CNC machine (which Styrotech CNC had) could CNC mill the board (deck, bottom, rails, cavities for fin-box, deck block and foot-straps): the board blank was ‘done’  meaning it could go straight from the table of the machine to the laminating bay where construction could begin. The blank featured precision and accuracy, and could be made numerous times, hence coining the term 'custom production'. And, if testing this board indicated that something should change, then this one particular thing could be changed without knowingly or unknowingly changing something else.

Building a board still involved using jigs – but the jigs had also improved, thanks to CNC. A good example of this is a rocker cradle. A rocker cradle is an advanced rocker jig, which was a piece of 18mm (or similar) MDF with the rocker curve cut into it, and then the board laminated while sitting on top of it, thus ‘setting’ the rocker. This was good, but not perfect - you could still build twists into the board, and the rocker migh move. A rocker cradle is an exact negative of the shape of the underside of the board, including the rocker, vee, concaves and cutouts, and is made of polystyrene. This cradle is then set on a vacuuming table (a measured, guaranteed flat and solid surface), and the board is vacuum laminated on the cradle – by doing so you’ll not only get a rocker that’s exactly what was designed, but at the same time other design features (e.g. vee, concaves etc.) are incorporated and ‘set’ into the blanks that’s just been laminated. At this point, the board would still reflect the design intent (thanks to CNC), thus reducing the opportunity for the boards shape to change during construction.

Being able to design a board, in its entirety using CAD (see image left - this is a CAD file of a knee board for use in the surf) meant that there was a digital record of the board in a continually growing library of designs and repository of knowledge. This was a logical extension of all of the design work that had gone before, and it made it possible to manufacture a board identical to one made previously; however the real breakthrough was in being able to take this CAD file and turn it into reality using a CNC machine that delivered precision, accuracy and consistent repetition unlike anything before.

The result was that Styrotech windsurf boards reflected the design intent more precisely than anything before them. The techniques Styrotech developed became the industry standard, and are now what’s used in the manufacture of a wide range of different boards.

Thus the same techniques developed for designing and shaping windsurf boards transferred easily to the design of a wide range of boards – Styrotech has since designed, or assisted in the design of further windsurf boards as well as surfboard, stand-up-paddleboard, knee and kite boards, and then taken these designs and turned them into reality using CNC machines.

3D Scanning 

Designing boards using CAD, and then ‘shaping’ them with CNC technology undoubtedly improved the ability of the designer to better replicate their design intention and function of the board.

But, despite the improvements CAD & CNC bought with them, there remained the challenge of reconciling the original CAD design of a board with the actual ‘physical’ object that was built, and how it performed.

At the end of the day, the boards were hand built and finished – ultimately the human factor could have a big affect on the way the board performs. Variation in the finished shape caused by temperature, materials and the very nature of a ‘hand-made’ construction process often lead to misleading feedback being given as to which particular features were resulting in which performance characteristic. What was often perceived a ‘good’ feature of a board might be attributed to a certain design element, when in reality it was caused by another element that had been – intentionally or not – built into the physical board.

Understanding variances from the original CAD design was really hard to identify and quantify in the finished board. Deviations were tiny, and the ability to measure them accurately using traditional measurement techniques difficult.

A good example is one of the concepts for the Styrotech Formula Windsurfing Board. Though never released on the market, the board was one of the prototypes designed in 2002 using Maxsurf and Solidworks. The blank was machined on a 5 axis CNC router, then hand built & finished – the original CAD design can be seen in the image (below left), and the deviation analysis (below right).

 

The image on the right shows deviation - essentially the board was accurate on the tail and through the mid-section, but the nose was low (-11.0mm), particularly on the right hand side. This reaffirmed what the sailing feedback was coming back as - the board was fast upwind, particuarly in light airs, and was a bit of a handful downwind.

Using longstanding measurement techniques, it was virtually impossible to determine with 100% certainty what it was about this particular board that made it effective without knowing exactly how accurately the physical board reflected the original design. This placed constraints on how effectively the knowledge gained from the prototype could be incorporated into subsequent designs, thus meaning that the development process was inefficient and costly.

3D scanning bridged this gap, as it was now possible to scan the completed prototype board and, using Deviation Analysis, compare it with the original CAD design. It became immediately apparent where the actual differences between CAD design and reality were, and this knowledge could dramatically change how the on-the-water performance of a board was interpreted.

Putting it all together - what it means

Using CAD made significant changes and improvements to the way boards were designed. There were limitations, but these were largely overcome with the introcuction of CNC milling technology. The overall accuracy of boards got better, developments could be by evolution as opposed to accidental revolution; the boards were truer reflections of what the designer was trying to create. With the introduction of 3D scanning, the final piece of the puzzle is in place, completing the feedback loop that starts with an idea, and ends with a board.



About the Author

Jonathan Squires With a background in business and product management both in New Zealand and internationally, Jon is currently working with Styrotech CNC as Sales and Marketing manager.

Styrotech have been CNC cutting our PVC foam centerboard blanks for over 6 years now. The resources Styrotech bring to the job make it a seamless process giving us the best results.

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