In addition to this, for any given board volume, doming the decks will drastically reduce flex.
It is trendy for shapers these days to make knowledgeable noises about surfboard flex but the reality is that most of it is bluff.
The flex frequency is also very important, as are the harmonics.
Regarding frequency, although even a high frequency flex or resonance is beneficial, ideally the frequency matches the range of the frequency of weighting and unweighting moves used by the rider. Most surfboards have a very high in the water flex frequency, and the frequency is always much higher in the water than on land.
Harmonics is an interesting aspect of flex and is used by sword makers in order to determine sweet spots on the blade and handle. In my opinion superior harmonics are achieved via mathematically generated curves, as these do not have the anomalies which arbitrary spline based curves inevitably produce.
Here' the Olo of the Sun today, one flexible board ...
Just to clarify in response to a question received today: In discussing flex harmonics I'm not talking about a sound, as the flex harmonics are of a low frequency which is inaudible to the human ear.
What I AM talking about is harmonic nodes ( where the sine curves intersect) and; these do affect performance.
There are at least two main nodes and several secondary ones on my longer boards, these are visible to the naked eye as the low frequency flex pulsates from nose to tail.and back again. . . . . . it is quite remarkable to behold !
Here's a video from Michael 'Tinker' Pearce showing sword harmonics, and the nodes of rotation one of which is known as the centre of percussion. I can show exactly the same phenomenon on my latest surfboard.
