HYDRO FOILMatt Crowther for Dive International
MENTION FORCE Fin a few years ago and someone would probably pipe up with something like, "Aren't those the fins that make you look like a duck?" Today the company can afford to laugh - many divers regard the American manufacturer as one of the industry's innovators, bravely pushing the design of underwater propulsion in new, if slightly unusual, directions. Personally, I've never gone out and bought a pair, although I have used the original FORCE FIN on a number of occasions, and I know many divers who find them excellent - so I was looking forward to properly testing this fin.
The FOIL looks very different to any previous designs, and the first thing that struck me was the size of the blade. It has to be the smallest surface area of any fin I've ever seen. For a start, it's incredibly slim (only as wide as the foot pocket). Actually, it does flare out slightly at the end, but still, it's hard to see how enough water is displaced to create adequate forward thrust. Brian Bickell of sic. [now POSEIDON DIVING SYSTEMS LTD.] the UK importer of FORCE FIN, later explained that it is the combination of design features that achieves this.
The other major cosmetic change is a vertical split, which cuts the last two thirds of the blade in half. FORCE FIN has stuck with its open-toe foot pocket, which is molded as one piece of material with the blade. When the fin is properly fitted, the strap section should support only the top of the foot. As you fin, the strap transmits energy to and from your thigh muscle, which is far stronger than your calf muscle, and less likely to become cramped. Conventional fin pockets transmit some energy from the calf muscles through the lower foot and toes.
For a state-of-the-art fin, the FOIL is very simple. It doesn't have a conventional fin strap and quick-release buckle system, but uses a length of bungee cord to hold the fin in place. A soft neoprene pad cups the heel of the foot, and a small webbing tab offers a useful finger-hold with which to pull the strap on and off.
I used an extra-large size, which fitted my size-nine drysuit boots perfectly. However, one of my regular buddies has heavy-duty boots fitted to his suit (also size nine) and found the foot pocket far too narrow. If you buy a pair in a shop they'll probably only ask for your shoe size, so remember to check the width of your boots.
I liked the simple bungee strap, and found the fins incredibly quick and easy to don and doff. But it can't be adjusted, which seems to have been a deliberate decision. Strange!
In the water, the fins take a bit of getting used to . I hadn't realized how much I rely on my fin blades to balance underwater. With the FOILS on, I initially felt quite unsteady, rocking from side to side as I breathed. This was no reflection on the fins' overall performance, but you need to give these fins several dives before they start to feel natural.
The rigid material used to construct the FOIL is a characteristic of all FORCE FINS, and one half of a system designed to minimize the effort required to make each return kick. As you kick down, the blade bends against the water, forming the correct shape to achieve maximum thrust - as you would expect. Then, rather than having to work against the water on each up-stroke the blade springs back into place ready for the next kick. To ease this resistance further there are small bumps on the sole of the foot section (VORTEX GENERATORS), which help to break the water's surface tension. The system really does work. And I reckon that the FOILS do it even better than their predecessors, because the small blade offers so little resistance to the water.
I used the FOIL FORCE on some demanding British dives, using a twin set and single cylinders, often swimming against currents. The power they offered me was excellent, even at low work rates. When using a standard finning style I found them very comfortable, or I could use smaller kick-cycles for quick bursts of speed , again with hardly any effort. My buddy commented later, that, on several occasions, he had noted how I had moved through the water with relative ease, at times when he had been struggling. Also, a word of warning for those of us who like to scull with their fins - you can, but not that well.
The key to the efficiency of the fin is in the curled edges on the end of the each blade, which direct water through the split, creating forward thrust. Of course, the curls alone wouldn't work properly without the split, and the special compound material.
I have to admit the FOIL FORCE have grow on me. They are definitely one of the best designs I've used, and I wouldn't hesitate to use them again. If you try a pair, don't judge them immediately. My best advice is to forget what you think a fin should feel like, and just enjoy. You'll get used to onlookers wondering what's on your feet.
It's hard to ignore the price of the fins - at nearly 200 pounds, they don't come cheap. However you can expect other high-performance fins to top the 100 pound-mark this season. The FOIL FORCE FIN available in blue, yellow, gray and black, costs 194.20.
For more information in the UK, phone sic. [now POSEIDON DIVING SYSTEMS LTD., Telephone: 01420 84300]---Matt Crowther for Dive International
Reprinted with the permission of Dive, © Dive International Publishing, Ltd., 1999