I’m with Bill on this one… The better you get water to stick to fin, the better performance…water sticking to fin is drag…better performance encourages more speed…go figure…
Not that I’m opposed to subjective testing. I built a board specifically to try some of Bill’s fairy dust or whatever he puts on the fins to increase drag. I’m just not going to make any broad sweeping generalizations about my results, yes or no. I do it all for my own selfish amusement. Mike
nailed it, Chrisp.
Acceleration is everything.
Which is why fin thrust is much more critical then fin material friction co-efficient.
The single most critical manuver in surfing?
That bottom turn when steep and deep that slings you up into the fall line.
All about the G’s…
In the instance, cited above, is exactly where the effect I described is most pronounced! Not in theory, but directly experienced.
Yeah chrisp , important point that’s overlooked too much…a board that doesn’t have enough straight line speed to make most waves , has got some very fundamental flaws somewhere…the sweet spot is there for a reason.
a relavent point (maybe) is that thicker fins , with more surface area are definately faster than the thin ones.
TRUE.
I’ll will put that to the test too. Wood fin built by warrior1515 with Bill’s template. Thanks again Bill. Think its around 5/8 inches thick. Compared to a Rainbow flex fin. Mike
I’m running the same template, with a pre-fin, on my 7’ 10’’ right now. Speed, driven by the wave, and turning response are quite significant, bordering on dramatic. You’re going to have some fun with that thing.
EDIT: Testing? I did that in 1960, some 54 years ago, after an hour long discussion with Phil Edwards, about his fin design theories. I call it my ‘‘Edwards Tutorial.’’ It changed my approach to both board and fin design.
Nor am I.
By definition, anecdotes are subjective – stories of individuals’ experiences and perceptions.
Isaac Newton published his personal experiences and thoughts (i.e. physics) just 327 years ago. But they have been well tested, replicated, expanded and quantified by many others since then.
Quantum physics are a bit younger, having been described by a handful of individuals in the mid-1920s. They too have been reasonably well substantiated and quantified.
Regarding the comment above about thicker fins being faster. Assuming this is true, is it due to the thickness or due to the inherrant stiffness that comes with the thickness???
If I recall correctly, stiffness is directly related to the cube of thickness. The two are inseparably linked. I believe stiffness is also affected by length.
Speed is a function of acceleration (rate of velocity change over time). Factors that affect acceleration (e.g. friction/drag) affect speed.
Earth’s gravitational acceleration is constant. Centripetal acceleration is determined by (changes with) turn radius and surfboard velocity/speed.
Force is a function of velocity, time and mass.
Also known as Centripetal Force & Centripetal Acceleration (physics).
Design factors that affect Centripetal Force/Acceleration will affect this aspect of surfboard performance**…**
Maybe increased fin drag makes it more difficult to drop into waves resulting in a later steeper drop, or once riding keeps you in a higher steeper line.
phebus, I hope your wrong about that. At my age later drops arn’t a good thing. I’d rather be up quickly and try to time the steepness and curve into my bottom turn. Mike
No less a personage than Lindsey Lord addresses fin thickness and foil. (AKA, Rudder) Zero flex, with an efficient hydrodynamic foil, are the major contributors to fin performance. The thickness is required to obtain the proper foil camber. The ratio of thickness to foil chord, that I have experience with, ranges from 10% to 12.5%. And I’ve had excellent results, going back over 50 years. Lindsey Lord suggests up to a maximum ratio of 13.7%. Or about 3/4th inch on a fin with a 5 1/2 inch base. The fin shape, leading edge angle, and fin position play a role too. Size also matters.
Balance. These conceptual theories are not black and white. Stepping off your fat single fin pigs may help to provide some balance to your experiential learning.
Are you really talking about drag and speed or harnessing and controlling power; momentum.
Force = Mass x Acceleration
Acceleration is the change in velocity over time.
Momentum = Mass x Velocity
Velocity is distance traveled over time.
An object with constant velocity has zero acceleration and therefore no force. An object whose velocity is increasing over time is accelerating and has a force proportional to its mass.
A surfboard cruising in a straight line at a constant velocity has zero acceleration.
Power = Work/Time
Work = force required to displace an object over a given distance in a specified period of time.
Without acceleration, there can be no force. Without force, there can be no work. Without work, there can be no power.
where’s griffin when you need him?
it’s about foil
its about release
its made from G10
Bill that koa fin looks like a Griffin template
your design is probalby older though
That basic fin design dates from 1964. I’m not aware of any of Griff’s single fin designs. As I recall, I based that fin on the shape of the pectoral fin of the White Tip Reef Shark.
…I had an interesting conversation with an aeronautical engineer years back, and he claimed that the standard 10mm thickness of the production fins was not enough to produce a foil that worked at optimum efficiency…so I foiled up a 10" fin , 15mm thick , and the difference in speed and performance was immediately noticeable…the standard fin box , with a 10mm slot is restrictive…probably to save materials in the production process , rather than produce better performance.