Myths in big wave surfboard design

Surfboards don't react to wave size, they react to the speed of the water flow.



To the average surfer, when waves reach a life threatening size this affects them emotionally so much that they put it in a different realm. In reality that's just another example of spurious information, of 'clutter' which has no design use whatsoever.



To most surfers the design factors which determine whether or not a surfboard is good for big waves are social and or emotional... in other words almost completely irrelevant in design terms.



Surfboards  react according to the laws of physics... how the board came into being has no bearing on how it works, it works entirely as determined by physics.



Waves don't care about the social standing or reputation  of the person who built the surfboard, nor does the surfboard. The rider sometimes does, and that can be the proverbial spanner in the works. . . the operator error. 



The bottom line is, boards react to water flow, not the ladies gossip circle.



There are one or two other differences on bigger waves, mainly the need to move faster to get into the faster moving swell, but that's about it, and the awe and mystery surrounding big wave boards in the minds of Joe average is based only on fear. Fear isn't a hydrodynamic factor.

Surfing and skiing physics: mass, speed, and drag

Larger more massive skiers have an advantage in downhill terrain:



http://books.google.co.nz/books?id=fkx2m_5fjyIC&pg=PA255&lpg=PA255&dq=greater+body+mass+downhill+ski+racing+advantage&source=bl&ots=Lmy1HYla8H&sig=l8SzPuHptEhFIn4geCQNF4ymmQE&hl=en&ei=AwCxTP_CJYyWsgPI_ZSwDA&sa=X&oi=book_result&ct=result&resnum=9&ved=0CEQQ6AEwCA#v=onepage&q&f=false



With surfing the situation is slightly different as the proportion of air drag to surfboard ( water) drag is lower than the proportion of air based drag to ski based ( snow) drag is with skiing.



From this we can deduce that the advantage in terms of drag reduction which a heavier board and rider combination has is greatly increased when surfing against the wind. This is because when surfing against the wind the proportion of air drag to water drag increases.



It is also interesting to note that rider posture has a big effect on air drag. . . upright postures are markedly less efficient. That's why I crouch when speed increases, even though correct 'style' might demand a more upright pose.

Surfing speed in big and small waves

I have often been asked how it is that we have recorded speeds of over 35 mph and up to 37mph on relativey small ( e.g.. head high) low period beachbreak , when tow in surfers on waves up to ten times bigger only achieve speeds in the mid 40'sIt seems strange at first as a 60 foot wave has ( all else being equal ) about 100 times the power of a 6 foot wave. Surely a surfer on a 60 foot wave should be able to go 3700mph if a surfer on a 6 foot wave can do 37mph?The answer of course is that they can't. A surfer on a 60 foot wave only travels about 1.5 times a s fast as a surferat peak speed on a 6 foot wave ( approximately that is ) .Why is this ?One reason is that drag increases by the square as speed increases ( approximately anyway ) so increses in power do not get a proportionally high increase in speed. This only partially explains the small increase in speed with large increases in powerA second reason is that waves of low power allow a more efficient energy transfer into horizontal motion than high powered waves. With high powered waves the glide path has to be more vertical in order to overcome the lifting power of the wave, thus a lot of the lifting power of the wave is wasted. The reason for this is that the rider only has a fixed amount of acceleration due to gravity available . . . the acceleration and force due to gravity do not increase proportionally as the power of the wave does. . . if it did the rider would go a lot faster on bigger waves than they do.