Today I found my self sorting through the rubbish that I hauled out of my old shaping room at Pearson Arrow. Inspired by my last post about Tanner, I sought out an old bag of fins from a period where I was studying thick foiled fins and their cause and effect in coordination with noserider design. I was operating on a hunch that you could alter the amount of drag on a given board by simply thickening or thinning the foil of a fin.
One of the problems with a building a proper noserider is it is often difficult to really hone its over all speed into a particular break or rider weight with out building a few boards. Often referred to as "dialing in" this process can be expensive and frustrating. Especially because once a board is glassed, making alterations to the rocker of a board, the only other heavy influence on a noseriders speed, is pretty much out of the question. Unless you're willing to pick up a saw and cut off the tail and reshape it. I did that too, but simply put- attacking the fins was a much simpler and cheaper solution.
I was messing around with wing-like templates at this point because angular lines are much easier to correctly proportion the foil shape and thickness so that I could be sure that it was the foil affecting the flow of the water and not some other unseen variable. Adding thickness to the fin created a more "true" foil shape. From these experiments I realized something that seems pretty simple now, the more correct the shape of the foil to nature, with no flat spots like you see on modern "plate" fins, the smoother the fin felt to ride. The thickness had a definite cause and effect to over all speed, as probably seems obvious looking at these pictures, but it was the smoothness that I became captivated by.
This led to several other fins...
The red one is actually a noserider fin too. Its foil was accurate to the point of using digital calipers to double check the over all foil shape and flow though out the fin. Pretty wild I'll admit. It was an experiment to see what happened when you keep the foil shape true but then reduced the over all area of the fin dramatically. The blue one is left over from experimenting with CAD designing the fins and foils and CNC cutting them, then moulding them. The wood one is a master plug that the mould came from. The idea at this point was perfection- how does it feel when the foil shape is mathematically correct- and eliminating hand foiling at this point was the only logical step. At this point I had gotten sucked into a few tangents and was just playing around with different ideas. I had stumbled into a project building an old Greenough
flexspoon and was really wrapped up in what he was doing with the shape of his fins. Alot of people tend to look at the
Greenough 4A and think that it was all about the template. His templates were amazing and way ahead of their time, exactly the reason we are still generally riding the same thing today. I suspected though that he was way past the template and the foil shape was something he was concerned with.
Revelation was struck when I got a package in the mail from Paul Gross, a longtime Greenough disciple. In it contained the schematics for building a true, period correct Greenough fin. You can see in the pics that the base flares out, but the bottom foil is just a scaled shape of what the overall shape of the foil was. There was a letter contained with the schematic, and Paul had told me that George had struggled with getting his boards to position themselves correctly in the "neutral" part of the wave, the part I suspect would be what we would consider the optimal place to position our noseriders. It turned out that George had discovered the same thing as I, only 40 years before and had honed his foil in to solve this problem. The term is "aspect ratio" and it refers to the thickness of a foil in relation to the length. It is often referred to in percentages and is commonly overlooked.
I still continue experiments to this day, but in a lesser capacity- but with a much firmer grasp of what happens when you "cut" though the water with a fin. Simply filing the leading edge of a fin blunt will slow it down dramatically, and conversely thinning it out or sharpening the leading edge will speed the same board up. These solutions seem so simple now in reflection, but the foil- a term that is often thrown around with abandon, is one of the most important aspects of a board. At least in the opinion of this shape geek. <(") Carl
