What’s the difference between having your front fins angled in toward the nose of the board and angled more vertical? What are the riding characteristics of both? I’m really interested.
Da Cheetah
Hi DC - you’re talking about something called “toe in” - basically - the less toe in you have ( ie the straighter your fins are with reference to the stringer) the stiffer your board will be - although it will be faster in a straight line. The more toe you’ve got, the slower your board but more manouverable it’ll be. I’ve only recently come to understand how sensitive this thing is - really tiny changes in toe in produce dramatic changes in performance. My next board’s going to use the 4wfs so I can adjust it easily after installation.
Not only do fins that are toed parallel to the stringer have more initial tendency to track. But, they also lose their flow sooner as they go through greater angles of attack. You can make up for this by moving camber forward in the fin foil and adding girth. But, now you creating more drag at higher velocities again. Toe helps two ways. It adds initial instability (a tendency to want to turn) and it positions the active foil such that the flow of water maintains flow without airation through greater degrees of angle of attack in the direction that fin turns towards. So, the Right side fin maintains flow of tighter right turns and similarly with the left fin turning in the left direction.
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Toe helps two ways. It adds initial instability (a tendency to want to turn) ...
I have somewhat of a disagreement on this point.
If you take a thruster config, and angle it less than 5 degrees (angle between stringer-line and direction of travel), it will RESIST turning. There is a drag increase on the outside fin that will correct the position to straight.
When you travel nearly straight, toed in fins are like a snowplow for skiing. They keep you straight, in a very lossy inefficient manner.
This facet of thruster design wreaks havoc with every person who first tries to turn one. Ultimately, you catch on, the rail has to be lowered to make the board turn, and turning the board without lowering the rail is fruitless.
When you take a beginner and teach them to surf on a board that may be turned easily without lowering the rail, it is like night and day.
The angle of the toe-in is itself a compromise. More toe is a slower board going straight. But one that turns better. So it is an optimization problem. Assymetric foiling doesn’t help - it improves turning at a given AOA, but it also increases drag when you are going straight. If surfers always had something like the 4wfs, I have doubts assymetic foils would ever have caught on. People would figure out you can set the toe greater on a fin with a symmetic foil than one with an asymmetric foil. Then, with toe-in optimized, which one provides better performance - the asymmetrically foiled fin toed to the nose, or the symmetrically foiled fin toed across the nose?
With all my criticisms of the thruster, it is still the defining configuration for surfboards, and has been for over 20 years. It has its limitations, though.
blakestah,
You always crack me up with your riding your board flat is better point of view. Most surfers want to surf off their rails. I've tried not to be critical of your posts in the past. But, you're pretty insistant. So, I've got to say here and now. The percentage of people that want to ride flat and allow their tail to redirect behind them is very small and from the videos you've posted of you fin system that's just what appears to be happening. Now I could be wrong and in twenty years everyone may want to surf like a firetruck with steering from the back. But, I just don't see it.
Everyone allows their tail to re-direct behind them. Surfboards with angled fins are rear-steering. This applies to thrusters, twin fins, and quads. Whether a surfer realizes it or not -the rear of a surfboard cuts a wider arc than the nose in turns. The rear has a re-director (the fin), whereas the front does not. The best turning boards track in the front half of their planing surface (with a deep single concave), and then have a double concave towards the rear that fades to flat. It fades to a double and flattens specifically so that the rear may be re-directed around the turn.
And the point was not that surfers want or do “ride flat”. Riding flat is an extreme - it is not particularly easy or desirable I state that to make the point clear. The issue is that on a thruster surfers HAVE to dip the rail to steer. The rail lowering is critical for fin engagement. This point is particularly difficult for beginners. Once you teach someone to surf on a board that turns well, but lacks this requirement, it becomes clear.
Further, I do not think or claim my single fin system is ubiquitously better than a thruster. It has plusses and minuses. It is better for a performance single than any single fin. Obviously, for particularly rail-oriented aspects of surfing, rail fins help. But for turns taken at less of an angle, you get more drive, and more thrust, from my single. And it is ALWAYS faster.
But, feel free to be critical. Take that unit that Herb has and test it out and show what an idiot I am.
…blakestah is rigth. and also i ride a single fin with an stabilizer behind and prove to be better than 3fin in most ways…
Cheetah, you’ve just got to try out as many different set-ups as you can. That way you find out the optimum for you, even if you have to document everything, camber, toe in, fin size and positioning. It’s a lot of fun and you learn a lot, using your own feeling and sensitivity. Get advice here, but try it yourself, everyone is different.
I’m not much of a multi fin man, but they have their place due to the rail fin function and lack of fin depth, allowing a lot of lateral movement, making them fun to surf for most people. I will state again though, that flat surfaces on foils are not dynamic. A correctly designed and positioned fin, or set of fins, will out-perform others.
Thanks to everyone for the information. Since I’ve joined this site I’ve been learning alot of things. And hope to make a few friends thanks alot!
DaCheetah