Sunday, September 16, 2012

Vortex Generators on Extra Force Fin Development

Early designs, circa 1995, of the Extra Force Fin were peppered on the backside with small coned vortex generators

Early Extra Force Fin Prototype

I found that a fin of any length beyond that of the orginial Force Fin design created eddy sheading.  You can  witness this on other flat fin designs, by watching others as they kick. Their flat fins will swing side to side, or shudder and shake during the power down kick phase. The too many vortex generators of my earliest Extra Force Fin designs was overkill.

Extra Force Fin SCUBA diver

Through observation and experimentation, I learned to balance placment to Energy Saving Zones (ESZ).

Vortex Generators, Extra Force Fin

Sunday, August 12, 2012

Scalloped Edges, Helicopters and Force Fin in Aviation

In "Small Beginnings - Leading Edge" commentary in Aviation Week and Space Technology, August 6, 2012, by Graham Warwick, the latest development in helicopter rotor blade design is introduced:

"The main rotors have short blades with scalloped leading edges inspired by humpback whale tail flippers, that increase lift, by delaying stall."

"Model tests in a  Munich University wind tunnel suggest that a bio-inspired rotor blade with a sinusoidally scalloped leading edge produces more lift than a conventional blade at high angle of attack."

Over 20 years ago, I was invited to a special after hours dinner as part of an underwater photography event at the Monterey Bay Aquarium.  At the time, I was working with my Assistant, Jimmy Gray, on the Extra Force Fin.

While examining the humpback whale models overhead, I had an epiphany. If I could scallop the edges of my Force Fins, I might mimic the highly fluid way in which whales move through water.

Aviation is just starting to catch up with Force Fin.

The Extra Force Fin was designed for my commercial diver friend, Skip Dunham, then President of Kirby Morgan Diving Systems, Inc.

Skip Dunham with early Extra Force Fin prototype - pre scallop edges and Chris Swann , Author of  "The History of  Oilfield Diving on my 32' Radon Diving Vessel, Otra Vez, off Santa Cruz Island, Channel Islands National Park.