...Fin Theory...

I’ve recieved some inquiries regarding fins…This might help some to understand a little more… There are many variables involved in determining surfboard performance. There is a wide variety of board shapes and styles of riding. Your ocean knowledge and ability are factors. So are the surf conditions. I feel you have to experiment with different fin combinations to achieve at your preferred fin set-up. Here are some of the basic concepts of fin set-ups and how they affect performance. The “Thick Base - Fully Foiled Fin” is a smooth, loose-feeling fin, that turns tight and releases well. With a fully foiled fin you can use a deeper fin with out the drag you would feel with a conventional fin. The reason is that a foiled fin releases water efficiently and a “flat” fin creates turbulence drag. My personal favorite is: depth 10",rake 10.5",width of base 5",Thickness at base 1.125". It has an 1/8" glass core, laminated to that is 1/2" Baltic birch plywood on both sides, foiled, glassed. The theory behind the “Thick Base - Fully Foiled Fin”…George Greenough had perfected the high-aspect, laminar flow fin, a development, which made him literally the fastest man in the water. The key lay in constructing a fin which could harness the wave’s energy without generating drag-inducing turbulence along the trailing edge of the fin as it moved through the water…Laminar flow basically is over a very narrow range. Water only goes back an inch and a quarter or so before breaking into turbulent flow. So the fin must be narrow. Look at any high-performance fish and you’ll see my fin is basically the same - it’s the same plan and foil shape as a large tuna…you’ll notice their tail is very narrow and quite high. With that kind of fin by the time the turbulence shows up in the water the fin has already left it behind. Hence no turbulence to affect performance. Another great fin is a “Liddle Flex Fin”… Greg Liddle’s theory:“I cannot emphasize enough how important it is to have a flexible fin or fins. The fin allows the board to behave appropriately. To trim at high speed with little effort. To maneuver smoothly and particularly to release during down the line high speed turns. A rigid fin with the inappropriate foil will not make this happen with these boards. The board will pivot awkwardly and die out of a turn with no forward acceleration. It will feel wrong to the initiated.” “It is essential that the fin have this particular type of flex, not a soft bending over flex, but a high tension flex that bends concave and gradually into the base of the fin. It lets power on and off even and smoothly resulting in a high speed and flowing style of surfing.” Another good fin is the “Wingnut Long-Rake” fin made by Rainbow Fin Co. is a fairly deep (10") fin medium stiff with plenty of rake and not too much tip. It’s a good fin for longer, driving turns. Smooth sweeping turns and extended trim are more difficult with many of the contemporary multi-fin boards. These boards often have a “stage-y” feel that is more suited to those who prefer “triple-pump” bottom-turns. The tri-fin set-up is only “faster” if it is pumped or rapidly turned from rail to rail. In straight-line trim the tri-fins are just so much drag. Some of the more progressive tri-fins have other design features, such as accelerated rocker, thin volume or narrow planshape that adds more drag, and requires even more energy from the surfer’s to fully use the leverage and projection of the tri-fin design. A “2 + 1”, or a “single fin with training wheels”, is a larger single fin in a center box, supplemented with smaller, Thruster-like side fins set on the rails. The most common set-up is a center fin box holding a 6" to 8" single fin. Side fins are sometimes glassed-on, but FCS plugs are common. The center fin is sometimes placed further up in the box, serving to narrow the “wheelbase” of the combined fins to give the board a looser rail-to-rail feeling. To summarize, the single-fin seems best suited to those who want to trim, glide and perform smooth sweeping turns. A single fin is stable yet pivotal. If you enjoy more energetic surfing, go for a multi-fin, with the “2 + 1” being a reliable compromise. I hope this has been of some help, and that you enjoy experimenting… Paul Jensen

I’ve recieved some inquiries regarding fins…This might help some to > understand a little more…>>> There are many variables involved in determining surfboard performance. > There is a wide variety of board shapes and styles of riding. Your ocean > knowledge and ability are factors. So are the surf conditions. I feel you > have to experiment with different fin combinations to achieve at your > preferred fin set-up.>>> Here are some of the basic concepts of fin set-ups and how they affect > performance.>>> The “Thick Base - Fully Foiled Fin” is a smooth, loose-feeling > fin, that turns tight and releases well. With a fully foiled fin you can > use a deeper fin with out the drag you would feel with a conventional fin. > The reason is that a foiled fin releases water efficiently and a > “flat” fin creates turbulence drag. My personal favorite is: > depth 10",rake 10.5",width of base 5",Thickness at base > 1.125". It has an 1/8" glass core, laminated to that is > 1/2" Baltic birch plywood on both sides, foiled, glassed.>>> The theory behind the “Thick Base - Fully Foiled Fin”…George > Greenough had perfected the high-aspect, laminar flow fin, a development, > which made him literally the fastest man in the water. The key lay in > constructing a fin which could harness the wave’s energy without > generating drag-inducing turbulence along the trailing edge of the fin as > it moved through the water…Laminar flow basically is over a very narrow > range. Water only goes back an inch and a quarter or so before breaking > into turbulent flow. So the fin must be narrow. Look at any > high-performance fish and you’ll see my fin is basically the same - it’s > the same plan and foil shape as a large tuna…you’ll notice their tail is > very narrow and quite high. With that kind of fin by the time the > turbulence shows up in the water the fin has already left it behind. Hence > no turbulence to affect performance.>>> Another great fin is a “Liddle Flex Fin”… Greg Liddle’s > theory:“I cannot emphasize enough how important it is to have a > flexible fin or fins. The fin allows the board to behave appropriately. To > trim at high speed with little effort. To maneuver smoothly and > particularly to release during down the line high speed turns. A rigid fin > with the inappropriate foil will not make this happen with these boards. > The board will pivot awkwardly and die out of a turn with no forward > acceleration. It will feel wrong to the initiated.”>>> “It is essential that the fin have this particular type of flex, not > a soft bending over flex, but a high tension flex that bends concave and > gradually into the base of the fin. It lets power on and off even and > smoothly resulting in a high speed and flowing style of surfing.”>>> Another good fin is the “Wingnut Long-Rake” fin made by Rainbow > Fin Co. is a fairly deep (10") fin medium stiff with plenty of rake > and not too much tip. It’s a good fin for longer, driving turns.>>> Smooth sweeping turns and extended trim are more difficult with many of > the contemporary multi-fin boards. These boards often have a > “stage-y” feel that is more suited to those who prefer > “triple-pump” bottom-turns. The tri-fin set-up is only > “faster” if it is pumped or rapidly turned from rail to rail. In > straight-line trim the tri-fins are just so much drag. Some of the more > progressive tri-fins have other design features, such as accelerated > rocker, thin volume or narrow planshape that adds more drag, and requires > even more energy from the surfer’s to fully use the leverage and > projection of the tri-fin design.>>> A “2 + 1”, or a “single fin with training wheels”, is > a larger single fin in a center box, supplemented with smaller, > Thruster-like side fins set on the rails. The most common set-up is a > center fin box holding a 6" to 8" single fin. Side fins are > sometimes glassed-on, but FCS plugs are common. The center fin is > sometimes placed further up in the box, serving to narrow the > “wheelbase” of the combined fins to give the board a looser > rail-to-rail feeling.>>> To summarize, the single-fin seems best suited to those who want to trim, > glide and perform smooth sweeping turns. A single fin is stable yet > pivotal. If you enjoy more energetic surfing, go for a multi-fin, with the > “2 + 1” being a reliable compromise.>>> I hope this has been of some help, and that you enjoy experimenting…>>> Paul Jensen Paul, a stiff flexer is like a dragster, load it up going into the turn and you get slingshot out when then pressure is taken off of it. You can only get out of it the power that was put into it. Soft wishy-washy fins result in slow weak turns. On the 2+1 designs, I like to keep the large center for punch and the smaller sides to help higher in the face. I have a set up that I call the double helix, the fin layup table is warped like that of the DNA strand. The finished fins can be set up with the bases straight and the tips toed or reverse the positioning with toe at the base and straight tips, I’ve found the straighter ahead with the flaired tips works the best for drive. So far I have only glassed them on. http://www.JimtheGenius@aol.com