Flexi driveshaft for full sized boat

Anyone got or remember the details of the boat drive system that was using a stainless steel flex shaft?
I seem to remember it was low power only, but I've been reading up about the efficiency of flex shafts, and it can actually be ok, also stainless steel flex shafts are now pence from China and available in larger diameters than previously. They used to be limited to large RC or weed whacker size (about 5 mm) which was no good for my upto 10 hp requirement. Now they are available at 10 and 13 mm diameters. It might solve a propulsion dilemma I have.

There was a company doing it, I think perhaps with a pedal drive. Anyone know what they were called and are they still going?

 

You'll find it in here:
Pedal Powered Boats https://www.boatdesign.net/threads/pedal-powered-boats.23345/

 

The company I saw that produced a flexible pedal drive used a principle of a flexible sheathed cable rather than the direct Straight flexible Shaft on the link above. I think sheathed cable is also the principal of most weed whacker drives. There are also Asian design trailing shaft Motors and mud Motors that use an enclosed solid shaft drive, and it pivots for use in very shallow water, but the trailing shaft is not flexible.

I'm not convinced that straight flexible shaft drives are practical or safe at high power ratings or even at the power ratings you write about, but I've never tried it at those levels. I've been using straight flexible shaft drives in the range of 100 Watts since May of 1995 and tried to get Rick Willoughby to try them several years later. He was pretty skeptical, but finally came around after a year or so, and built several boats that were powered based on the idea. Some of our written conversations are archived somewhere on the Giant boat design forum and possibly other forums.

 

Is there a reason why a universal joint couldn't be used?It ought to suffer less friction and be less prone to thrashing around.

 

Weight mainly. Cable drives are very light. It also allows the drive unit to be removed from the transom and placed in the boat. I know other solutions allow this too, but I think Flexi drive is the way ahead for my design. It allows the motor to be placed in the boat, away from the transom and the water.