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Kiwi Style Foils

Designed and engineered for performance sailing crews.

Mackay Boats started building 470 and Flying Dutchman foils in 1982 (long before we started building 470s). The name we sold them under was “Kiwi Style Foils”. Sailors and coaches from the 80s and early 90s will know them well.

In 2011 we decided to revert back to the KiwiStyle Foils brand so you will start seeing the famous logo again!

Up until recently we made our foils with laminated wood, glassed over with unidirectional and woven glass cloth. This technique had always produced the best finished foils with perfect edges. In the past, Molded foils were never as nice.

Now, with CNC machining and computer modelling becoming common place- and no longer being cost prohibitive, we have been able to use this technology to build perfectly accurate aluminium molds. These are in a different league than fibreglass molds. We can now produce molded foils with the same standard of finish as our wooden foils.

This has opened up a significant advantage. Because we are only working with absolutely quantifiable materials; Glass Fibre with a foam core- we can alter and develop the characteristics of the foils to a very fine degree (with the wooden foils there was always variations in the strength of the wood. No two pieces of wood are exactly the same. It was also difficult to adjust the layers of glass laminate on the surface of the wood while still maintaining the perfect thickness and shape.)

All CNC Mold foils are built starting with an extra hard Gelcoat surface and then different combinations of Epoxy, Carbon and E-glass depending on the class rules.

By adjusting the size, shape and cloth used in the laminate, we are able to make the foils to exact requirements for bend and twist.

 

470 foil development

Much of the development that has taken place in 470 foils is due to our early work. For example we were the first to recognise and prove that minimum thickness foils were faster. We also developed the leading edge shapes that worked best under the 470 rule. These were different from any NACA or other generally available sections.

Our foils were credited by Dave Barnes and Hamish Willcox as being a significant factor in their speed surge of the early 1980s. When we started building 470s in 1994, we supplied our foils as “MacKay Foils” on most of the boats we sold. The developments in the last 6 years have been very interesting!

Leading up to the 2000 Olympics we experimented with flexible centreboards. The idea was that they would twist to windward more when raked forward. The Australian team liked the foils very much and used them to win both gold medals. These foils were 20% more flexible than our standard foil. After the games these became our standard foil.

Between 2000 and 2004 there was a trend towards stiffer foils. Many crews tried centreboards as stiff as possible from the various foils makers. However the feedback was that very stiff foils did not work well throughout the range of conditions. The trend has gone full circle, with most crews preferring more flexible foils.

                                                                                                                                      

At the same time, we must keep in mind that different crews will perform better with different centreboards. Some will like the feel of stiffer foils, others will like the way a more flexible foil behaves.

At this point in time we have 3 different variations on flex and twist. The most flexible is a duplication of what Tom King and Jenny Armstrong used in the 2000 Olympics. We have recently built our stiffest foils for several crews. These measure the same as other very stiff foils on the market. In the middle of that range we have made several medium stiffness foils. Generaly sailors are preferring the softer foils and find these easiest to sail fast in all conditions.

As mentioned above, one of the key areas is the leading edge shape. The sectional shape is not a shape that comes from any readily available scientific data (this is because there hasn’t been enough testing done on foils with flat areas). After a lot of testing we finally got a LE shape that would not stall on the rudder. We then used this LE shape on the centreboard. The drag coefficient on a 470 centreboard cannot be changed much by leading edge shape because of the large flat areas that follow. The most important thing by far is for the foil NOT to stall.

If you can have a higher angle of attack without stalling out then it will help in certain conditions.  

  1. When you tack. 
  2. When the centreboard is raked forward and the flex allows it make a higher angle of attack. This gives more lift but can be dangerously slow if the board stalls. 
  3. When you work the boat hard with body action it is possible to stall the centreboard, especially in waves.

We are quite sure that much bigger gains can be made in this area than realised.

 
ISAF Licensed Builder
Member of NZmarine

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Mackay Boats Ltd

  • 24 Manga Rd, Silverdale
  • Auckland, New Zealand
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