K4fins are a unique innovation in windsurfing,

"we have opened up another page in windsurfing's progression book."

The K4 fin shapes, design, and innovation has come from water time. There is no better way to develop a product

than trying it out with lots of good old quality water time. Coupling this with science

and know how has culminated in something ground breaking.

If you are interested in how K4 fins can improve your boards performance and your own riding, then drop us a line, we are always near a beach here in Cornwall and will be more than happy to discuss the advantages of using K4fins.



What are K4fins on about? The truth is as always in the pudding but....

When Jumping and general sailing you feel the fins under the foot complimenting your movements. When heading up-wind you feel the fins flex and work with the power you're putting through them. When landing they again flex and work with you, rather then against you!

Waveriding is where the fins really excel. In your bottom turn the flex of the fins allow you to drive them hard and fast. As you're going through the bottom turn and your speed starts to drop off the fins give you something back. All that 'stored' energy from flex is given back to you when you need it most. In doing so you don't get stuck through your turn. You can power all the way through to the lip and smack it at full velocity. 

K4fins have created a unique and new material for windsurfing. OptoFlex is a molded resin long fibre matrix that has been carefully manipulated to provide the perfect flex patterns for windsurfing. Our K4 technicians took a long time to create the perfect material with the qualities needed to provide the performance we now appreciate. Lighter, snappier and with outstanding flex memory. The fins are extremely robust too -we haven't had a single return through breakage.

With our k4fins we’ve found that 2.5 to 3.0 degrees is best for most boards. We’ve produced our fins with the heads at different angles, with 1, 2 and 2.8 degrees (marked as 3). So if your board has straight boxes you need the 2.8 degree k4s to give 2.8 degree toe, if your boxes are at 0.2 to 1.0 degree you’ll need the 2 degree k4s, and if you’re boxes are 1.0 degree plus you’ll need the 1 degree. If you have toe nearer 3 degree, the board will be biased towards tight easy turning. If the toe is nearer 2 degree, you’re board will feel faster in a straight line.

Your boards bottom shape and the position of the fins can also affect the amount of toe in needed. Concave boards will need less toe than flatter shapes, and fins closer to the rail will need more toe than fins close together.

We’ve also found that quite often Tri fin fronts can stand more toe angle than the fronts on a quad. This is because often the rear quad fins are straight (have no toe) and the front fins need to be at a reasonably similar angle. It’s no good having the fronts at 3 degrees with the rear fin (that’s only say 3cm behind) having 0 degrees -the water flow will struggle with this difference in angles. This is not the same on a tri fin as the front and rear fins are far enough apart to be independent.


To measure the toe in angle your front fin boxes may (or may not) have is simple. Measure the distance between the front inside edge at the front of the fin box, and then measure the inside edge at the rear of the fin box, this difference (if any) will give you the toe in angle of the fin box in the table below. (Measurements are based on a 10cm long fin box).

DIFF 0mm = TOE 0deg   /   DIFF 1.75mm = TOE 0.5deg  /   DIFF 3.5mm = TOE 1.0deg   /   DIFF 5.25mm = TOE 1.5deg   /   DIFF 7.0mm = TOE 2.0deg

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