Human powered propulsion - heavy duty & long distance

[icetreader]

Intrigued by the discussion about propulsion for a human powered boat that would cross the Pacific I asked myself what was the traditional approach to moving heavy human-powered boats over long distances.
The answer was sculling - from the Venetian Gondola to the Chinese Yuloh, the Japanese Ro etc: It has worked for centuries, and enables a single person to move large size boats loaded with passengers and goods across long distances.
http://www.simplicityboats.com/yulohpage2.html

The advantages are:
Simple design, using all the main groups of muscles in the body (reduced fatigue), the blade generates continuous propulsion.

Sculling requires the boat to be more stable than rowing, paddling or pedaling do, but that's possible to achieve with a multihull design.

Any thoughts?

[cyclops]

How much energy is lost due to 2 hulls going not straight? Or drag factor at 1 mph?

[CDBarry]

You are correct. Sculling is more efficient than rowing, since it uses lift vs drag.

[icetreader]

Originally Posted by cyclops

How much energy is lost due to 2 hulls going not straight? Or drag factor at 1 mph?

Cyclops,
I don't know the answer, but I suppose that since two straight hulls offer better directional stability than a single hull with curved lines the loss would be minimal.
As for drag at low speed, in average twinhulls have about 25% more surface area than monohulls of same displacement, and this is meaningful especially at lower speed but the twinhulls' better directional and lateral stability compensate for this under "real world" conditions.

CDBarry,
I'm sure there have been studies on improving this type of propulsion, for example by introducing some flexibilty it the "tail".
One can only be amazed from what fish and marine mammals achieve with tail propulsion.

Yoav

[sideditch]

Originally Posted by cyclops

How much energy is lost due to 2 hulls going not straight? Or drag factor at 1 mph?

Not much: because the relief of exit off sets the drag. And as the speed increases, depending on the draft, the "drag" creates lift such as a 'ski' craft and actually decreases the power needed and results in greater speed.

Assuming power other than wind is used of course.
It is a good time to be an explorer in nautical design for boat design as we have seen it in all of history till today remains in the DARK AGES.

Tiny Bubbles, that is all the water needed to move at high speed in water born craft, notice the carefull omission of 'watercraft'.

Regards,
Sideditch

ps Who cares if you are using lawyers for propulsion; you just wind them up and they go on for ever.

[Bergalia]

Originally Posted by sideditch

ps Who cares if you are using lawyers for propulsion; you just wind them up and they go on for ever.

True, but at what cost... and can you be sure they'll pull in the same direction...

[harlemriverman]

http://www.littlerivermarine.com/

[Sander Rave]

<<Sculling requires the boat to be more stable than rowing, paddling or pedaling do, but that's possible to achieve with a multihull design.>>

Still don't know how to quote...

If you got the hang of it, you don't need a stable boat. You just have to balance your weight in the right "swing". If you are talking about energy and efficiency, you don't want the boat to rock, this means loss of energy...

In my experience sculling is great to produce torque, low speed, high mass movement. If you ask me how I want to cross a large wet area by human power, I'd prefer rowing.

[lewisboats]

Originally Posted by Sander Rave

Still don't know how to quote...

"[QU0TE=Sander Rave]
Still don't know how to quote...
[/QU0TE]"
Hit the quote button then just edit the stuff between the quote boxes down to what you want to quote and put your message after the end quote box.