The "D" Fin
Well I was tossing up what to talk about next, but with a thread on D-fins popping up on swaylocks I have decided to go into the chosen fin for my HWS design or more to the point the magnificent D-FIN; a design that effectively incurs a drag coefficient that reflects positively on the overall design concept of a 1960's nose rider.
The D fin was popularized back in the early 60's before George Greenough came on the seen with his radical high aspect fin profile based around the shape of the tuna fish fin. The most notable feature or difference between fins such as the D-fin and those based around his design concept is the way in which they affect the turning capabilities. D-fins are generally considered as a pure turning fin that provides the user a means of turning a board. George’s designs were considered radical in their time as they not only enabled turning but added a new dimension to fin design known as DRIVE.
Driving fins have a characteristic flex built into their design and coupled with their streamlined foiling; a spring is effectively created driving the boards out of a turn bring it back to speed. Although I love the work of George Greenough, it was a given fact that if I was to design a HWS based around the design concepts of the late 50's early 60's it would definitely need to have a D-Fin attached.
The general profile of a D-fin exhibits higher drag forces then other designs, but this is not considered as a limitation to the overall design when the board in question is being designed with nose riding in mind. By inducing drag forces at the fin position the fin can effectively be used as a cantilever pulling the tail down into the wave or the curl to aid nose riding by lifting the nose up. Further more by positioning the tip beyond the tail position of the board the effective lever arm is increased. A major draw back in their use is the lack of maneuverability. Check out Tom Wegners paper entitled "fins": http://www.tomwegenersurfboards.com/html/fins.html
My fin will be constructed internally of wood before being glassed. This could result in a positive buoyant fin if glassed lightly but I have plans to finish the fin with several layers of glass in turn dramatically increasing its weight, so I am guessing this will not be the case. The plan at this stage is to foil the fin according to a NACA0012 foil for a given cord greater then that of the actual cord length of the fin. In doing so the leading edge and fin surface will follow the profile of a NACA0012 foil but finish short as the actual cord length will be less then that of the designed cord length and in turn reduce the efficiency of the fin by inducing drag at the trailing edge. Length or depth of fin has not been set yet and will not be finalised until the rocker profiles have been set in place; preliminary designs have it set at around 9" to 10".
The D fin was popularized back in the early 60's before George Greenough came on the seen with his radical high aspect fin profile based around the shape of the tuna fish fin. The most notable feature or difference between fins such as the D-fin and those based around his design concept is the way in which they affect the turning capabilities. D-fins are generally considered as a pure turning fin that provides the user a means of turning a board. George’s designs were considered radical in their time as they not only enabled turning but added a new dimension to fin design known as DRIVE.Driving fins have a characteristic flex built into their design and coupled with their streamlined foiling; a spring is effectively created driving the boards out of a turn bring it back to speed. Although I love the work of George Greenough, it was a given fact that if I was to design a HWS based around the design concepts of the late 50's early 60's it would definitely need to have a D-Fin attached.
The general profile of a D-fin exhibits higher drag forces then other designs, but this is not considered as a limitation to the overall design when the board in question is being designed with nose riding in mind. By inducing drag forces at the fin position the fin can effectively be used as a cantilever pulling the tail down into the wave or the curl to aid nose riding by lifting the nose up. Further more by positioning the tip beyond the tail position of the board the effective lever arm is increased. A major draw back in their use is the lack of maneuverability. Check out Tom Wegners paper entitled "fins": http://www.tomwegenersurfboards.com/html/fins.htmlMy fin will be constructed internally of wood before being glassed. This could result in a positive buoyant fin if glassed lightly but I have plans to finish the fin with several layers of glass in turn dramatically increasing its weight, so I am guessing this will not be the case. The plan at this stage is to foil the fin according to a NACA0012 foil for a given cord greater then that of the actual cord length of the fin. In doing so the leading edge and fin surface will follow the profile of a NACA0012 foil but finish short as the actual cord length will be less then that of the designed cord length and in turn reduce the efficiency of the fin by inducing drag at the trailing edge. Length or depth of fin has not been set yet and will not be finalised until the rocker profiles have been set in place; preliminary designs have it set at around 9" to 10".
posted by GRUB at 12:51 pm
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