Maui Ultra Fins - The Delta Concept - Boards Windsurfing

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Maui Ultra Fins – The Delta Concept

Dave Gollick from caught up with the men behind MU to discuss their brand and their new concept, check it out…

Koster on the team

Maui Ultra Fins – The Delta Concept

Rick spent the last 30 years as an Aerodynamics Engineer for the Aerospace industry. As a keen water sports enthusiast spent many holidays on Maui in idyllic conditions. Rick has been experimenting with fin shapes for many years and because of the ideal conditions quickly gained a reputation in the local area. Demand became apparent and soon the Maui Ultra Fins company was formed.

Many years later Maui Ultra Fins is an international company with a worldwide distribution network and many top international Pro team riders. The ability to push the envelope with new and radical designs makes MU Fins stand out. Some critics may have been harsh of some of the designs but the proof is clear.

In 2008 Rick made a major breakthrough with the X-Wave. This upright wave fin redefined the standards for wave fins. With a lot of scepticism MU pushed forward developing the concept and now the X-Wave has got its position at the top in the hands of many including top wave pro Robby Swift and Philip Koster. Maui Ultra now produces over 26 different fin models each designed to perform in its specific area. From Freeride designs in the form of the ‘Ride’ to specialist Weed applications and super fast Slalom fins, Maui Ultra has a fin for all abilities and conditions and with the addition of the ‘’Delta Series’’ everybody has been catered for.

Rick Hanke with the Delta Fins at the German Boot Tradeshow


An Interview with Rick By Dave Gollick of Windsurfingfins

Rick what was reason for designing such a radical fin?

The primary goal was to design a fin, which could be used in shallow water.

At which discipline was this aimed at?

Understanding the aerodynamic characteristics of this fin allowed me to adapt it for both speed and wave applications, which means it could be a general purpose fin. The short length gives it the ability to be agile in the Waves.

It looks extreme with a very high rake, short depth and very wide base. What is rationale behind this?

The shorter length gives the ability for the fin to be used is very shallow sports, particularly inland water such as the Netherlands. In addition, the rake angle of 55 degrees gives it the ability to shift heavy weed, which again is normally present in shallow water.

How does this radical design work as a speed fin?

Due to the wide base we were able to make thinner foils (3.5-5.0% relative thickness) the fin has enough absolute thickness to be stiff with no danger of break away. Thin foils provide less drag and allow high speed and this make for an ideal speed fin.

We have seen a shift towards more traditional shapes in the speed fins lately; low aspect, short and wide looking. What is the advantage of the Delta?

With a high angle of attack the Delta wings create a vortex, which separates from the leading edge and holds the flow on the surface. With flow separation at a very high angle of attack, around 30 degrees when compared to normal fins of around 10-12 degrees, upwind performance as greatly improved.

Rick, the Delta looks extra ordinarily wide, why does it over hang the box so much and what advantage does this provide?

As the fin depth has to be low the width has to be increased in order to give the required surface area to translate to the more traditional sizing. The lift curve (lift VS angle of attack) is only half of that of a traditional fin; this means we have to use twice as much angle of attack. But this is not a disadvantage because the fin is not so direct and the control is improved, especially at high speed.

So in short this fin can be used in shallow water situations, with or without weed being present, which gives many windsurfers in these areas the chance to get out on the water. Is there a size chart that gives us a conversion comparison to traditional sizing?


The Final Product

With many requests for shorter fins for shallow and weeded areas and the combination of 12 months testing MU are proud to present the Delta Wing Series. The result is fins that can handle both shallow as well as weeded areas.  100 prototypes have been put through their paces in order to find the perfect outlines and profiles. A fleet of some 70 Pro’s and amateurs provided the feedback needed to perfect this radical fin. Generally the main advantage of the Delta wing series is to allow safer travel over windsurfing spots with shallow areas. This has allowed certain spots such as tidal channels to become used for speed sailing as well as general freeriding. A Wave version and multi fin set-ups are currently in trials and have produced some interesting results.

The wide base and shorter length allows the use of thin foils, which promote speed. This also gives the fin a stable ride and a good upwind ability. The slight negative with a fin of this type is that it does not plane as early as a traditional fin and additional training is needed to perfect slashy gybes.

On a positive note the speed Delta version has currently achieved over 80Km/h during testing last year. Roberto Hoffman the MU World Cup Slalom rider commented –

“The Delta fin is a great alternative to a traditional weed fin. The first feeling you get is slightly different compared to what you get with a traditional straight fin, but after a few runs the feeling is that you have a very solid, fast and agile gybing fin under your board. You have to use a little less pressure on your back foot when going upwind, but the down wind leg is fast and easy to control. I think the fins offer up new possibilities in sailing shallow water locations, having great performance and perfect control!”

The final word

In general the Delta Series is a general-purpose fin for any windsurfing spot that has shallow and/or weed issues. The different models cover Slalom, Speed and Freeride disciplines and give windsurfers in these areas the chance to enjoy their sport. The Delta series was never designed to compete with the traditional fin in normal sailing spots and if compared give a different feeling in both performance and control.

Thanks to


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