# Would a pedal-driven propeller move a ship more efficiently than a bank of oars? **URL:** \ **Category:** Factual Questions\ **Created:** [June 5, 2007, 7:43pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885 "2007-06-05T19:43:09Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [June 5, 2007, 7:43pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/1 "2007-06-05T19:43:09Z")
Suppose you have two ancient Greek [triremes.](http://en.wikipedia.org/wiki/Trireme) One carries 170 men to pull the oars, in the traditional fashion. The other also has 170 men but has been modified: Instead of pulling an oar, each man pumps a pair of pedals like those on a bicycle; the pedals are connected to drive chain that turns a screw-propeller. Set the two in a race. Which ship goes faster? Tie the two ships stern to stern. Which proves to have more power? I think it would be the pedal-driven ship in both cases; human legs are stronger than human arms. Has this ever been tried? ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [June 5, 2007, 7:59pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/2 "2007-06-05T19:59:33Z")
[QUOTE=BrainGlutton] I think it would be the pedal-driven ship in both cases; human legs are stronger than human arms. [/QUOTE] Not only are legs stronger, but the application of power through a pedal system is more continuous than through an oar system. When those oars are out of the water, no power is being used to propel the boat. On the other hand, I’m not a rower but I think it’s more than just arm power in rowing. ---
**Author:** ![steronz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steronz/32/11765_2.png) [@steronz](https://boards.straightdope.com/u/steronz)\ **Post date:** [June 5, 2007, 8:00pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/3 "2007-06-05T20:00:01Z")
I’m not a rower by any means, but the limited amount I’ve done has taught me that rowing is definitely a full body experience. You brace your legs against something and pull; your legs, back, stomach, chest, arms, everything is working in concert to move the oar(s). I believe crew boats have sliding seats to better make use of leg power. Wiki confirms: > [@](#): > > The distinction between rowing and other forms of water transport, such as canoeing or kayaking, is that in rowing the oars are held in place at a pivot point. This allows the oars to act as a lever of force, rather than a paddle. In flatwater rowing, the boat (also called a ‘shell’ or ‘fine boat’) is narrow to avoid drag, and the oars are attached to rowlocks at the end of outriggers extending from the sides of the boat.[4] These boats also have sliding seats to allow the use of the legs in addition to the body to move the oar and so drive the boat. > **[Rowing (sport)](https://en.wikipedia.org/wiki/Sport_rowing)** > > Rowing, often called crew in the United States, is the sport of racing boats using oars. It differs from paddling sports in that rowing oars (called blades in the United Kingdom) are attached to the boat using rowlocks, while paddles are not connected to the boat. Rowing is divided into two disciplines: sculling and sweeping. In sculling, each rower (or oarsman) holds two oars, one in each hand, while in sweeping each rower holds one oar with both hands. There are several boat classes in which a... ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 5, 2007, 8:02pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/4 "2007-06-05T20:02:09Z")
Seems like the oars might have an edge, by virtue of having more surface area in the water. 170 slaves, two men to an oar, that’s 85 oars in the water. I think you would have to have a pretty sophisticated transmission to efficiently convey the power of all 170 slaves to a single propeller. Is there a history of pedal powered devices (using pedals on cranks) prior to the invention of the bicycle? ---
**Author:** ![Duke\_of\_Rat](https://avatars.discourse-cdn.com/v4/letter/d/ad7895/32.png) [@Duke\_of\_Rat](https://boards.straightdope.com/u/Duke_of_Rat)\ **Post date:** [June 5, 2007, 8:07pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/5 "2007-06-05T20:07:15Z")
Seems to me that the 50% or so of the time the oars are not doing any work would make it pretty easy for the prop to come out on top, but rowers use their backs as well as arms to row-the peddle guys would have only their legs. The loss of any thrust 50% of the time and the efficiency of the oars compared to a prop that works all the time at what would probably be better efficiency than an oar would allow for drivetrain losses and still be better IMHO. Prop design would make it easier to use the same power and make the ship go faster (smaller diameter/higher pitch) or more thrust for the pull-off (large diameter, shallow pitch) where the oars are just oars. Dang it, there were no posts when I started typing this, but what **Dag Otto** said. And as for surface area of oars vs surface area of the prop, you might not be able to drive a prop with exactly equal surface area as all the oars, but what is there will be working while the oars are in between strokes. ---
**Author:** ![ArmenE](https://avatars.discourse-cdn.com/v4/letter/a/e9bcb4/32.png) [@ArmenE](https://boards.straightdope.com/u/ArmenE)\ **Post date:** [June 5, 2007, 8:10pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/6 "2007-06-05T20:10:44Z")
Just wanted to chime in to say that when rowing, the oars are not out of the water anywhere near 50% of the time. The oars swing forward through the air quite quickly, and then take a (relatively) long time to be pulled through the water. ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 5, 2007, 8:25pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/7 "2007-06-05T20:25:27Z")
If you google “human powered boats” you’ll discover a lot of links to people trying to set speed records with muscle power alone. Virtually every boat in these competitions is pedal-powered. Here’s [a competition](http://traylorfwd.home.mindspring.com/neat_little_race.html) in 1994 where a 58-year-old man and his son in a pedal-driven boat kept pace with Olympic athletes using traditional paddles and oars. The challenge with the triremes would be figuring out a linkage that could transmit the force from so many different people efficiently. But in general, pedalling delivers more power than rowing. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [June 5, 2007, 8:47pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/8 "2007-06-05T20:47:59Z")
[QUOTE=Fear Itself] 170 slaves . . . [/quote] Nitpick: Get _Ben Hur_ out of your head. Galleys were not always rowed by [slaves.](http://en.wikipedia.org/wiki/Galley_slave) I don’t think Greek galleys ever were; not sure about the Romans. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [June 5, 2007, 8:58pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/9 "2007-06-05T20:58:45Z")
Any galley intended for battle could not be rowed by slaves, since what do the slaves do when the galley gets boarded? They revolt and join the boarders. Or consider that one dropped oar can foul the entire bank. You would no more man your expensive war galleys with slaves than you would man modern tanks and bombers with slaves. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 5, 2007, 9:05pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/10 "2007-06-05T21:05:02Z")
[QUOTE=BrainGlutton] Nitpick: Get _Ben Hur_ out of your head. [/QUOTE] Mea culpa. I was probably still thinking about my screenplay on the life of Turkish privateer and Ottoman admiral [Turgut Reis](http://en.wikipedia.org/wiki/Turgut_Reis) > [@](#): > > Turgut Reis later sailed back towards Corsica and docked his ships at Girolata on the western shores of the island. Taken by surprise while repairing his ships, Turgut Reis and his men were attacked by the combined forces of Giannettino Doria (Andrea Doria’s nephew), Giorgio Doria and Gentile Virginio Orsini. Turgut Reis was captured and was forced to work as a galley slave in the ship of Giannettino Doria for nearly four years before being imprisoned in Genoa. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 5, 2007, 9:26pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/11 "2007-06-05T21:26:48Z")
[QUOTE=Fear Itself] Seems like the oars might have an edge, by virtue of having more surface area in the water. 170 slaves, two men to an oar, that’s 85 oars in the water. I think you would have to have a pretty sophisticated transmission to efficiently convey the power of all 170 slaves to a single propeller. Is there a history of pedal powered devices (using pedals on cranks) prior to the invention of the bicycle? [/QUOTE] I don’t why you think the oars would have a larger surface area than a prop. Did the OP limit the size of the prop? I don’t care how big your oars are, a prop can be designed to have at least the same area if not more. [old joke] slave master to galley slaves: “I have good news and I have bad news. First the good news, you all get an extra ration of rum at lunch. Now the bad news, the queen wants to go water skiing after lunch.” [/old joke] ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 5, 2007, 9:33pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/12 "2007-06-05T21:33:34Z")
[QUOTE=Rick] I don’t why you think the oars would have a larger surface area than a prop. Did the OP limit the size of the prop? I don’t care how big your oars are, a prop can be designed to have at least the same area if not more. [/QUOTE] But can a single prop have a larger surface area than combined surface area of 85 oars in the water at the same time? That’s one big mutha propeller. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [June 5, 2007, 9:53pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/13 "2007-06-05T21:53:00Z")
Would there have to be only one screw? (gosh that sounds odd) ---
**Author:** ![Hypno-Toad](https://avatars.discourse-cdn.com/v4/letter/h/b2d939/32.png) [@Hypno-Toad](https://boards.straightdope.com/u/Hypno-Toad)\ **Post date:** [June 5, 2007, 9:54pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/14 "2007-06-05T21:54:20Z")
A large prop is better at absorbing and transmitting larger power loads. Better than spinning a small prop faster, which just churns the water. [Here](http://www.navweaps.com/index_tech/tech-001.htm) is a discussion of propellors in modern ships. Also, as mentioned above, the linkage of the pedalers to the drive system needs to be addressed. The right gearing could probably increase the efficiency significantly. One thing that occurrs to me is that although the rowers minimize the amount of return time on their backstroke, the propellor blade is transmitting power to water throughout its rotation. I just don’t know if this is a significant factor. [Here is](http://www.navweaps.com/index_tech/tech-034.htm) a more basic essay on propellor design from the same website. Really makes me think that a properly design pedal system would be better than the rowers. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [June 5, 2007, 10:12pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/15 "2007-06-05T22:12:50Z")
[QUOTE=Rick] [old joke] slave master to galley slaves: “I have good news and I have bad news. First the good news, you all get an extra ration of rum at lunch. Now the bad news, the queen wants to go water skiing after lunch.” [/old joke] [/QUOTE] Mythbusters tested this, and found you actually can water ski with a crew of trained rowers. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [June 5, 2007, 10:16pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/16 "2007-06-05T22:16:35Z")
The main difference is how the power is transmitted to the water. Oars work by drag, pulling an object through the water. Propellors, on the other hand, work by lift, generating a force differential on the two sides of the prop. Lift is more efficient than drag at transmitting the energy. This is why we don’t see side-wheeler or stern-wheeler ships any more, because the propellor (lift) is more efficient than turning a wheel with boards on it (drag). As an aside, the Chinese “scull” with a single oar over the stern, moving it side to side to drive the boat forward. In this configuration, the oar is generating lift rather than drag … clever folks. w. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [June 5, 2007, 10:16pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/17 "2007-06-05T22:16:41Z")
[QUOTE=Fear Itself] But can a single prop have a larger surface area than combined surface area of 85 oars in the water at the same time? That’s one big mutha propeller. [/QUOTE] I dunno, but I’m sure there’s a good reason why powered boats use propellers instead of motor-driven oars. Or paddle wheels. In fact, I got the idea for the OP from the following passage from Part II of George Orwell’s 1941 essay [“The Lion and the Unicorn: Socialism and the English Genius”:](http://gutenberg.net.au/ebooks03/0300011h.html#part14) > [@](#): > > What this war has demonstrated is that private capitalism, that is, an economic system in which land, factories, mines and transport are owned privately and operated solely for profit—DOES NOT WORK. It cannot deliver the goods. This fact had been known to millions of people for years past, but nothing ever came of it, because there was no real urge from below to alter the system, and those at the top had trained themselves to be impenetrably stupid on just this point. Argument and propaganda got one nowhere. The lords of property simply sat on their bottoms and proclaimed that all was for the best. Hitler’s conquest of Europe, however, was a PHYSICAL debunking of capitalism. War, for all its evil, is at any rate an unanswerable test of strength, like a try-your-grip machine. Great strength returns the penny, and there is no way of faking the result. > > When the nautical screw was first invented, there was a controversy that lasted for years as to whether screw-steamers or paddle-steamers were better. The paddle-steamers, like all obsolete things, had their champions, who supported them by ingenious arguments. Finally, however, a distinguished admiral tied a screw-steamer and a paddlesteamer of equal horse-power stern to stern and set their engines running. That settled the question once and for all. And it was something similar that happened on the fields of Norway and of Flanders. Once and for all it was proved that a planned economy is stronger than a planless one. But it is necessary here to give some kind of definition to those much-abused words, Socialism and Fascism. On the validity of his judgment on capitalism I make no comment here, but the example used to illustrate it is an interesting one. ---
**Author:** ![Darryl\_Lict](https://avatars.discourse-cdn.com/v4/letter/d/7cd45c/32.png) [@Darryl\_Lict](https://boards.straightdope.com/u/Darryl_Lict)\ **Post date:** [June 5, 2007, 10:16pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/18 "2007-06-05T22:16:48Z")
I remember when Allan Abbot was building pedal powered hydrofoils back in the 1980’s. He once held the human powered land speed record. The first hydrofoil he built was notable because the thing had to be launched from a catapult. The water had to be very flat, if I recall collectly. The second generation had a set of pontoons which allowed a water start. According to this [site](http://lancet.mit.edu/decavitator/) the Decavitator holds the world human powered water speed record of 18.5 knots (21.3 mph) over a 100 meter race course. Note that it has an air propeller to eliminate [cavitation](http://en.wikipedia.org/wiki/Cavitation) effects from a water propeller. Here’s an interesting [page](http://www.humanpoweredboats.com/Photos/HydrofoilHPBs/HydrofoilHPBs.htm) of human powered hydrofoils, most of which have conventional water propellers. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [June 5, 2007, 10:19pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/19 "2007-06-05T22:19:17Z")
[QUOTE=Rick] [old joke] slave master to galley slaves: “I have good news and I have bad news. First the good news, you all get an extra ration of rum at lunch. Now the bad news, the queen wants to go water skiing after lunch.” [/old joke] [/QUOTE] [possibly older joke] “On a trip like this, how much do you tip the whipper?” [/poj] ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [June 5, 2007, 10:26pm UTC](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885/20 "2007-06-05T22:26:17Z")
I’ve read some “Connecticut Yankee” stories like L. Sprague de Camp’s [_Lest Darkness Fall_](http://www.amazon.com/Lest-Darkness-Fall-Bring-Light/dp/0671877364/ref=pd_bbs_sr_1/104-9877726-4934363?ie=UTF8&s=books&qid=1181082247&sr=1-1) – or alternate-history stories like John Maddox Roberts’ [_The Seven Hills,_](http://www.amazon.com/Seven-Hills-John-Maddox-Roberts/dp/B000EPFVPK/ref=pd_bbs_2/104-9877726-4934363?ie=UTF8&s=books&qid=1181082142&sr=8-2) where technologies familiar to us, such as the steam-powered boat, are invented in antiquity – and I’ve never read one where a character thinks of a pedal-powered boat (which would require fewer engineering breakthroughs than a workable steam engine). [Next page](https://boards.straightdope.com/t/would-a-pedal-driven-propeller-move-a-ship-more-efficiently-than-a-bank-of-oars/406885.md?page=2)