People often talk about whether kitesurfing boards have too much flex or too little. But what is too much or too little flex, how do you know and what effect will it have on your riding?
Flex in kitesurfing boards gives you a smoother ride as the flexing of the board absorbs energy as the board cuts through the water. So the board acts like suspension and takes some of the jarring as the board carves over all those waves, this saves your knees from taking the hammering! To much flex is not always desirable however as it create a soggy feeling and give very limited 'pop.'
Flex in a board also has an effect on the rocker line as the more the board flexes, during hard edging for example, the more pronounced the rocker becomes. In practice this can be a very good thing, the board retains a fairly flat profile at low speeds which aids early planing and as the speed and thus the downward pressure on the board increases so the rocker line become more pronounced which gives additional grip in the water. So already you can see how flex plays a crucial role in determining the characteristics of kitesurfing boards with stiff boards naturally favouring bigger, heavier riders, freestyle fanatics and powered up conditions, while more flexible boards favour lighter riders and less pumped conditions.
A lot of kitesurfing boards have solved the problems posed by flex in a board by using tip flex. Boards typically have a stiff centre and flexible tips, this creates a board that is much more adaptable to different conditions. During a powered up moment the tips will flex providing more grip as more pressure is applied to the edge, enabling it to ride out the chop much more effectively whilst simultaneously maintaining a stiff central section to give good pop. In lower wind the entire board profile remains much flatter giving early planing and upwind performance. Many riders will test the flex of a board by bending it right in the middle (either over their knee or by pushing the board into the ground) however this doesn't really give you a good idea of the actual flex you will feel on the water as kitesurfing boards are not loaded up this way when riding.
There is an awful lot more than simply the give in the middle that will make a board feel soft while riding, mainly the rail shape, the fins and the thickness profile. You will often find boards that feel soft on the beach but when you ride it have a very stiff feel and vice versa. In short the only way to tell the flex of a board is to get out there and ride it!
The fashion in new kitesurfing boards is starting to favour a much wider foot stance which means we have to re-evaluate the flex in the board. Due to the downward pressure points (your feet) being nearer the tips there is more space in the centre of the board this can lead to the board flexing the other way during riding, something called 'negative flex,' where the board bends upwards (towards the rider) in the middle and forces the tips downwards. Thus before you simply widen your stance you should think about stiffening the centre section of your board to prevent negative flex.
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