Setting the fins on the 12 foot Baron paulownia wood surfboard
The Baron fins are ultra thin. In particular the long tip of the boomerang fin has a chord ratio of 1.6% when the usual chord ratio range used for underwater foils is from 9% to 16%.The principle behind the long thin fin tip on the boomerang fin is that it has extreme flexibility which allows it to conform to the water flow, thus exerting a low amount of lift along with very low drag.In the case of the annular wing tunnel fin, a chord ratio of 6% is used ( The tunnel is the same thickness as the boomerang fin but has a shorter fore and aft length and thus a higher chord ratio ) although this is thin it is nowhere near as thin proportionally as the boomerang fin tip. Tunnel fins are able to handle low chord ratios better than planar fins do anyway, due to the fact that they are low pressure fins, and in fact 6% is a standard chord ratio for our tunnel fins. The ultra thin boomerang fin tip is a development of the bulb tipped flex fin used on the previous Baron board ( the prototype known as the D 11-9 )and the bulb tipped fin used on the original 'Resolute Salmon' 12 footer. The bulb tipped fin moved from side to side as the fin upstand flexed , using the same motion as a swimming fish abd giving a very sinuous feeling to the ride. The bulb itself however did not flex, as it was made thick enough to keep the chord ratio within the conventional range. Hopefully the new thin tip will be an improvement. The flex is so soft that the tip at the trailing edge can be moved from side to side at least four or five inches with gentle finger pressure, the fin takes on a substantial curve at the same time.Altogether this well proven kind of fin combination produces a large amount of lift using the principle of low pressurefins moving large water volumes. . .. a characteristic which keeps the drag down. It also has brilliant handling qualities and is completely vice free in it's behaviour.Given the current trend for less and less fin area in a search for low drag, fin systems of this general type ( which we have been riding for at least 8 years ) are heretical, but they are wickedly efficient and give a delightful advantage to the rider .
Labels:
annular wing,
Baron project,
boomerang fin,
chord ratio,
drag