Laura's new Hobie kayak had this reciprocating rubber fin propulsion system.

According to Tracy and Laura it is super efficient. Just a small 
bicycle action on the pedals propels the kayak at a good clip.
We did not measure anything but this emulates the action of fish tails
or fish fins. The rubber fins stick straight down through the bottom of the
kayak and swing from side to side 180 degrees out of phase. The fins are
made from rubber so they flex back at fourth as required. Stop in at your 
local Hobie dealer and take a look. Seems to be a break trough in boat 
propulsion.

Paul Lamar
 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org