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FREERIDE FINOLOGY

21/10/2015
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FREERIDE FINOLOGY

The fins that power our free ride boards are an overlooked part of the engine that drives our fun on the water. We take a look at the market with key industry players, a buyer’s guide and of course to kick it off, a lesson from the master teacher, our very own Peter Hart.

Words and Photo – Peter Hart

”Here a 120 free-move board  is cracking around like a board half its size, thanks partly to the thin, curvy rails but also to the relatively small free-ride fin (35 cm) with a lot of sweep in the tip. But beware – the fin shape and size, have to compliment the design of the board. For example  putting  a small, raked fin into  a  more race speed oriented model as an attempt to make it more manoeuvrable, may not work because it would not fully release onto the plane. To be manoeuvrable, a board has to be well-trimmed and planing freely.”

“I knew I was good!” You chunter to yourself as suddenly and unexpectedly you experience a feeling of light, efficient symmetry with arms and legs equally but gently loaded and the board planing straight and level without you having to twist and contort. And good you may be. But essentially you’ve chanced, albeit momentarily, upon a perfect set-up where the lateral forces of a well-set sail are perfectly matched by the size of the fin; and the fin itself matches the width of the tail.

The aim is to feel like that the whole time across a wider range of conditions. And part of the solution comes from dialling into the information coming through your back foot from the fin; and then recognising when a change up or down can restore balance or tilt performance in a certain direction, towards top speed or acceleration, for example.

Ask a racer which is their most influential item of kit, and they’ll point to the fin. Free-ride boards are more forgiving both to set-up and to sail but you ignore the importance of the fin at your peril. Space is short and the subject huge but here are some points to ponder as you look to grow your free-ride fin quiver.

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What is a free-ride fin?
Like the board itself, the classic free-ride fin seeks to blur the boundaries and provide the best of every world. The powerful, upright mid section gives you something to hoof against and converts the sail’s power into instant lift, acceleration and planing speed. The swept back tip holds the tail in through carving turns, makes the gybes feel smoother, less ‘skippy’ and allows you to vary the shape and steepness of the arc.

The limitations of the given fin.
The fins given away with the free-ride boards have improved enormously over the years. The size offered will tend to work best with the middle of the board’s recommended sail range. For example, say you have a 130 ltr free-ride board with a quoted sail range from 6 to 9 sq m, the standard fin (perhaps around 48 cm) will work best with sails around 7 to 8 sq m. It’s when you flirt with the extremes of sail size that you’ll benefit from a fin change.

The symptoms of too big and small.
When the fin is too small for the board and/or the sail size, the board slops from edge to edge. It never full releases onto the plane. It sits deep in the water and although you may feel you’re pointing upwind, you’re actually crabbing sideways. It’s easy to overload the back foot and spin out. If it’s too big, you feel you’re fighting the fin as soon as you start to plane. It’s like having jack-hammer under your back foot. It’s hard to bear away and in extreme cases, you’ll tail walk.

Reasons to change fin size.
Matching fin to sail size is the primary objective but not the only one. Going slightly bigger offers extra lift and acceleration at slower speeds – good if you’re feeling your way into the straps for the first time; and also if you’re sailing in enclosed waters where you need to get going quickly in a gust, stay upwind; and where you haven’t the space to get up to full speed.

Relating fin design and size to your board.
The free-ride board category is enormous. The choice of fin(s) depends on where your board lies on the speed, manoeuvrability spectrum. At the speed end where the boards are aping slalom shapes (aka ‘Free Race) with their flat bottoms and harder, straighter edges, you’ll err towards a deeper, straighter fin, with less sweep in the tip (if any). At the ‘squirrily’ end where the boards have more curve in the plan shape, thinner rails and more’ v’ underneath (aka ‘Free-move’), the fin can be smaller with more rake. The ‘v’ displaces a little water, increases resistance – hence you can get away with a smaller fin.
And finally …

Get a plastic ‘cheapy!’
Beware of planing obsession! Free-ride boards, especially the bigger ones, make excellent light wind training platforms for practising and nailing the basics – tacks, gybes, backwind sailing etc. – at which point the big planing fin is a bit of a liability. For very little money you can pick up a small plastic training fin – or cut down an existing knackered, fibre-glass one. With a shallow (30cm or less) and preferably wide fin, the board is more manoeuvrable off the plane and you can mess about in knee-deep water.

“Free-ride boards are more forgiving both to set-up and to sail but you ignore the importance of the fin at your peril”


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FREERIDE FIN DEVELOPMENT PROCESS
Dietrich (Rick) Hanke, Founder and President, www.mauiultrafins.com
‘’Freeriding is one of the most popular windsurfing disciplines. Boards and sails have to cover a wide range of sizes in order to match the sailing conditions and rider weights. The same is valid for the fin. The fin must provide a side force over a wide range of speed and courses without the danger of flow separation (spin-out), the fin must be fast (low drag) and easy to be controlled also under choppy and high wind conditions. Further, gybing too should be easy and without losing speed.

The design process which is applied at Maui Ultra Fins is the same for all types of fins and can be divided in several important steps:

1 Optimization of the profile (foil)
2 Optimization of the outline
3 Manufacturing of prototypes
4 Testing under real conditions

The most important and time consuming part is the selection of the foil and the optimization of the foil parameters like relative thickness, nose radius, position of maximum thickness and speed. At Maui Ultra Fins I use a fluid dynamic comput-er program where the forces (lift, drag) can be calculated as a function of all the parameters and combinations. The resulting foil polars give the design engineer all the required information on the way to an optimized foil. The fin outline has to be optimized in accordance to the required fin area, the box dimensions, the required stiffness (no breaking), the flexibility and the overall drag, which is additionally influenced by the aspect and taper ratio. For a complete new fin about three to five prototypes are designed. When all parameters are selected the fins will be drawn with a CAD program which also delivers all data for machining the fin with a CNC machine in G10 material. The relevant data is then transferred to the manufacturer and the prototypes are ready for testing by windsurfers with different levels at different places in the world. By comparing all results in performance and behaviour (feedback form) the final fin design (box-sys-tems, length range and printing design) for the series is selected and the fins are produced.Simply said, fins are the sails in the water. The fin must compensate all side forces of the sail which are transferred to the board in order to sail a straight course. That means that we must handle this part very carefully because the total performance of the board depends also very much on the fin performance.

Each damage – especially at the leading edge – reduces the fin performance. Therefore it is recommended to use your fin cover when you are back at the beach and do not stick your fin in the sand. Small damages to our G-10 fins can be sanded. If the damage is bigger you can use epoxy resin or super glue to fill the damaged part and create a smooth surface by wet sanding. (280 to 600 grade sanding paper).’’

FREERIDE FIN BUYING TIPS
(Graham Turner, founder and owner, www.juiceboardsports.co.uk)
‘’Unlike 10 years ago, nowadays the standard fins coming with freeride boards are well suited to the board. The most popular freeride fins we sell in the shop are ones with a curved tip, slightly raked back and with a fine entry profile. The US box is still popular as it allows people to move the fin forward and back. We like to really talk with people and discuss their fin needs but in general we would sell a more raked profile for smaller freeride boards and swept at the tip for bigger freeride boards. Upgrading from the basic design is very popular also, something like a ready to race style. There is a slight premium in price of course but what you get is a slimmer profile throughout , like a top end race fin but detuned slightly for comfort. It would be a fin more for somebody who works the board to plane and enjoys driving and pushing the fin as opposed to just being on the board for the free ride. As we say you’re either a driver or being driven and it’s important to recognize which you are when choosing your fin. Material choice can depend a lot on the waters you sail in – if you are somewhere rocky or  shallower, stay away from carbon or polyester,  g10 is best as you can sand it down and offers durability and longevity.  Modern  weed fins are really good and often overlooked, they are as quick in weeded waters as they are not picking up drag. Another important point is what sort of freeride board you have, if it is a soft feeling, carve/comfort biased board, they don’t like race ready, stiff fins. Equally if you have a more race orientated board, stay away from a softer, flex tip fin.’’

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