Why Paddles Instead Of Propellers? (Human-Powered)

[jyl]

Every human-powered boat in common use is propelled by your arms via paddles. Okay, proper rowing technique for some racing sculls also uses the legs via a sliding seat, but that's pretty specialized stuff.

Why don't we see more leg-powered boats? A large diameter, slow rpm propeller would seem very efficient. The friction losses in a bicycle type drivetrain are not high. The legs are much more powerful than the arms. The arms would be free to control a rudder, hold a fishing rod or shotgun, brace with paddles.

Anyone seen such a thing, or know the pros and cons?

[stomachmonkey]

You ever cruise a lake in a paddle/peddle boat?

Kinda sucks.

Much better control with oars/paddles.

[peppy]

Like these?


Walmart.com: KL Industries Sun Dolphin Five Person Pedal Boat in Cream / Blue: Fishing & Marine

[stomachmonkey]

Originally Posted by peppy

Like these?


Walmart.com: KL Industries Sun Dolphin Five Person Pedal Boat in Cream / Blue: Fishing & Marine

Can't really toss that on the top of a car like a canoe or kayak.

[Flieger]

I always thought these penguin-power kayaks from Hobie Cat were cool:

Hobie Cat Company - Mirage Sport

[nota]

oars are cheap and work well in very shallow water
and work on almost any small boat

props are complex costly and need more draft [deep]
and are very eazy to damage
and the whole boat needs to built around the prop drive system
and have lots of friction loss in the systems
that hobie thing needs alot of draft
and I bet it is very eazy to break

I had a addon outboard hard operated prop unit [yardsale junk]
it suckked big time, lots of effort gave little force
forget even moving up wind in more the 5 mph winds

[red-beard]

Paddlewheels are very efficient in the water, more so than a propeller. But, they are not very good at higher water speeds and do not mate well to highspeed engines. Paddlewheels also do not work well in rough seas.

[jmaxwell]

This one even uses a prop!

Walmart.com: Nauticraft Escapade Pedal Boat with Arch and High Windshield: Fishing & Marine

[doug_porsche]

I am guessing Torque also fits into to it.

Torque on the WalMart boat is 6 or 8 inches. The torque on the paddles are 2 or three feet.

I dont think you would want to paddle the canoe across the water if you could only put the paddle in the water no deeper than 6 inches and HAD to lock your fore arm and could only rotate the paddle around your wrist.

Or in car terms, yes I do think of most things in car terms. The different between a VERY long stroke motor, that turns at SLOW rpms (Canoe), or a short stroke motor turning at very high, comparatively, rpms (WalMart boat).

Torque defines how fast it can go
HP is how fast it will get to the top speed.

[Racerbvd]

A local shop use to carry a pedal powered Prop driven kayak Cat. Looked cool but as other have pointed out, weren't very efficient and you had to be a very good "Spinner" to get any where, course here in FL, we sometimes need to use the paddle to puch off a Gator...

[HardDrive]

Anything mechanical, by its very nature, breaks. Paddles have less that can go wrong with them. If you were in a remote area without outside contact, would you rather rely on paddles, or a slightly more efficient mechanical device?

[jyl]

I found this

The WaveWalker Minnesota - Hydroped

Pedal powered kayak. The propeller unit is retractable for landings. Supposedly cruises at 5 mph, does 9 mph for a good cyclist. Either is ripping fast vs a regular kayak. Video below. I sort of envision having a standard kayak paddle, for bracing strokes, launch/land, extra speed.

Worlds Fastest Pedal Powered Production Kayak. - YouTube

[jyl]

Here's a guy who installed a Hobie Mirage unit in a wood kayak.

It's All in the Legs

I think the leg power thing has some merit. You'd want to be able to use the paddle too, and not give up a sleek, efficient hull or a low CG.

When you get caught out after the wind and chop have picked up, especially if you're paddling against a stiff wind, it can be hard to make headway. A 10 mile crossing can take several hours. Weak paddlers need towing, people start pissing in their boats, the whole thing is not fun. Having a leg option would be nice.

[island911]

Originally Posted by HardDrive

Anything mechanical, by its very nature, breaks. Paddles have less that can go wrong with them. If you were in a remote area without outside contact, would you rather rely on paddles, or a slightly more efficient mechanical device?

Yeah! I mean who has ever heard of anyone being up a creek w/o paddle?


Seriously? ...Paddles have less that can go wrong with them?

I can't remember the make, but I've seen a nice 2-person trimaran that had a deployable foot powered pod. ...off the side of the center hull, for minimal depth. The reason for this feature - because a paddle on a sailboat gets in the way, is difficult to use for prolonged periods (no wind) and can get lost quickly.

oh, and btw, it was gear or toothed-belt driven . ..just to confound HardDrive with mechanical goodness, I suppose.

Found it. ..a Fulmar 19

MULTIHULLS.com - FULMAR Canada

[Flieger]

Originally Posted by doug_porsche

Torque defines how fast it can go
HP is how fast it will get to the top speed.

You have it backwards. Horsepower defines the top speed. The gear ratio spread (which affects the thrust) and ultimately the amount of area under the power curve define how fast the car can reach top speed.

[island911]

Originally Posted by Flieger

You have it backwards. Horsepower defines the top speed. The gear ratio spread (which affects the thrust) and ultimately the amount of area under the power curve define how fast the car can reach top speed.

Not quite. Power also defines how fast the car can reach top speed. That torque that you refer to is at a specified rpm (power).

Splitting hairs, I know, but you are an engineer, right?

[Flieger]

Yes, I am an engineer. Notice I said that the amount of area under the power curve defines how fast the car can get to speed? The critical range is only the rpm drop between the gears, so the gear ratios also affect it.

[Moses]

Originally Posted by Flieger

I always thought these penguin-power kayaks from Hobie Cat were cool:

Hobie Cat Company - Mirage Sport

I've used these. AMAZING! Tuck the blades in shallow water and use the paddle only. Typically you use the pedals and your arms. My favorite kayak.

[Flieger]

I saw them on Bill Dance Outdoors when they were fishing in some swampy Oxbow lake off the Mississippi river.

[sc_rufctr]