Yes, the EXTRA Force Tan Delta is insane. I have tested that fin in my younger days against racing monofins and they were really close. Absolute burners.
The real function that we should be talking about is not speed or stiffness, but flexibility. The way a FF works is to flex the blade, some may refer to this as loading the blade or even activating the blade. This flexing or loading that you put into the blade will snap back and propel you, think about bending and releasing a spring. With the different grades of material (original, pro, tan delta) the blade gets progressively stiffer. If the blade is so stiff that you can no longer effectively flex the blade, you end up with a paddle fin. Of course the corollary to this is too flexible. If the spring is too flexible, you easily bend it to its limit and it only returns that limited amount of force.
The stronger you are the stiffer blade you can still effectively flex. Of course a stiffer/stronger the spring the more energy it will store and transmit. Most would say faster, but fins are not fast nor slow, they only transfer your leg kick into propulsion. If you are stronger, you can load more power into the fin, which in turn allows you can go faster. It is for this reason that I strongly recommend that nearly everyone in scuba should dive the FF Pro. It is flexible enough that most diver can effectively use it, but stiff enough not to limit you. Smaller individuals, should probably look at the original.
As TN noted, the TanDelta material has changed over the years, the older stuff (pre-2004’ish) was crazy stiff, the newer material is not as stiff, but has a higher rebound (more efficient). Bob has informed me that he has found a new formula again that promises to be better yet. I still recommend 90% buy the FF Pro, if you find that lacking take a serious look at the Excellerating ForceFin (with Whiskers or Batwings), or its cleaner derivative the Hockey Force (returning to production soon)
The real function that we should be talking about is not speed or stiffness, but flexibility. The way a FF works is to flex the blade, some may refer to this as loading the blade or even activating the blade. This flexing or loading that you put into the blade will snap back and propel you, think about bending and releasing a spring. With the different grades of material (original, pro, tan delta) the blade gets progressively stiffer. If the blade is so stiff that you can no longer effectively flex the blade, you end up with a paddle fin. Of course the corollary to this is too flexible. If the spring is too flexible, you easily bend it to its limit and it only returns that limited amount of force.
The stronger you are the stiffer blade you can still effectively flex. Of course a stiffer/stronger the spring the more energy it will store and transmit. Most would say faster, but fins are not fast nor slow, they only transfer your leg kick into propulsion. If you are stronger, you can load more power into the fin, which in turn allows you can go faster. It is for this reason that I strongly recommend that nearly everyone in scuba should dive the FF Pro. It is flexible enough that most diver can effectively use it, but stiff enough not to limit you. Smaller individuals, should probably look at the original.
As TN noted, the TanDelta material has changed over the years, the older stuff (pre-2004’ish) was crazy stiff, the newer material is not as stiff, but has a higher rebound (more efficient). Bob has informed me that he has found a new formula again that promises to be better yet. I still recommend 90% buy the FF Pro, if you find that lacking take a serious look at the Excellerating ForceFin (with Whiskers or Batwings), or its cleaner derivative the Hockey Force (returning to production soon)
