Here is a fin system question I’ve been wondering about. It seemed like for years people paid a lot of attention to blending the contact area where glass-ons met the board. The all of a sudden with the press-in systems it looks like the fins are just slapped on - and for a layman like myself that can look like a cheap econonomic choice rather than progression. We worry about flex near fin tips, but they are usually just as much underwater as the base, right? How important really is the base of the fin as far as flow/surfing? Nels
Here is a fin system question I’ve been wondering about. It seemed like > for years people paid a lot of attention to blending the contact area > where glass-ons met the board. The all of a sudden with the press-in > systems it looks like the fins are just slapped on - and for a layman like > myself that can look like a cheap econonomic choice rather than > progression. We worry about flex near fin tips, but they are usually just > as much underwater as the base, right? How important really is the base of > the fin as far as flow/surfing?>>> Nels Where’s Flipper when ya need him??
Where’s Flipper when ya need him?? Right on! I can see him wavin’ to us now. Here’s a doggerel for ya! Flipper left the land cause the sea was “the place” Evolution’s millenium’s just can be erased! You talk about effective aqua-locomotion! Good Surfin’, Rich
Right on! I can see him wavin’ to us now.>>> Here’s a doggerel for ya!>>> Flipper left the land cause the sea was “the place” Evolution’s > millenium’s just can be erased!>>> You talk about effective aqua-locomotion!>>> Good Surfin’, Rich So, what? You guys don’t know either? (relax
Because if all that really counts on fins are length, foil, and thickness, then wouldn’t that make a lot of these mild tail-area concaves BS too? Inquiring minds want to know, but right now it’s beer-thirty. Nels
So, what? You guys don’t know either? (relax
A straight answer:>>> The longer and flatter the surface is where the board meets the base of > the fin the more turbulence. If you look at dolphins pectoral flipper it’s > cutaway with a has a very smooth rake. This what works best for direction > control as far as I’m concerned with minimum tolerence. Foil is another > matter.>>> Good Surfin’, Rich The fillet that occurs between the bottom of the board and the fin base on glass on fins is for structure primarily. For years yacht designers used the same fillet between the bottom of the hulls and their keels.Primarily because that’s what you see in nature. Then the America’s Cup campaigns started doing tank testing to optimize their hull and appendage design. The results are that now all modern racing sailboats have foils mounted without a chamfer. And, when we would rework the facturies bottom to make them ultrarace fare, the designers would always have us make the joint as clean as possible. It has to do with a hyrodynamics property called the end plate effect. The bottom of your board and the sides of you fins are both foils with water flowing along them fore to aft. Imagine them with little arrows depicting the flow latitudinally. Foils that keep the arrows flowing the most parallel to the intended foil shape are the most efficient at affecting the foils intended movement through the water. When you through a fillet into the equation you actually redirect the flow of water across the two foils and fillet into a greater area of disruption or turbulence. So, while intuitively you might think that because fillets abound in nature, so they must be a good thing. They are most often used for structral support more than efficiency of flow.
what a great explanation. sounds like you have done your homework tom. i recall a parmenter article where he surfed a board with glass ons then ground them off and put plugs on. his take was the fcs were better for that exact reason. more surface area, more drive. my hunch has always been that the base/intersection of fin and board is the most crucial part of the system.
So, while intuitively you might think that because fillets abound in > nature, so they must be a good thing. They are most often used for > structral support more than efficiency of flow. Well allright now! Thanks both Tom and Halcyon. You answered a question I could never get an answer for at a surf shop. Nels