Pedal Power or Oar Power - which is more efficient?

Discussion in 'Boat Design' started by SailorDon, Jun 6, 2015.

  1. SailorDon
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    SailorDon Senior Member

    I have to agree that sliding seat rowing is good for the body, but IMHO, sliding your butt back and forth hardly seems "classy".
    Sliding seat rowing is very fast and very efficient and it's the only way to go for a contest of speed, but not "classy".

    It's a personal and subjective thing, but here is my interpretation of "classy" rowing.
    [​IMG]
    Can you imagine an Olympic sculler in his racing shell wearing a straw boater hat? [​IMG]
     
  2. gggGuest
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    gggGuest ...

    On the chain thing, its worth remembering that the typical motorcycle installation has *two * 90 degree changes of direction, and these have greater losses than parallel shafts. Chain is at its best with two parallel shafts separated by a reasonable distance.

    With pedals and a screw there would only be one 90 degree change, as is the case with many automotive installations. The other big argument against chain drive is that it comes with a significant maintenance overhead, which is likely to be rather greater in a marine environment.
     
  3. portacruise
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    portacruise Senior Member

    You can get the 2 parallel shafts for chain if you mount the pedal station at right angle to the boat length, as a number of designs have done.
    The maintenance issue is solved with a sealed oil bath and 90 degree change can be done with a single twisted chain.
    http://microship.com/bobstuart/spinfin.html
    Lighter, easier, cheaper and faster to repair than gears.

    PC

     
  4. NoEyeDeer
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    NoEyeDeer Senior Member

    Yale already built and tested a hydrofoil single scull back in 2008. It worked. It did use a sliding rigger setup, instead of a sliding seat, to minimise pitching. However, the "pulsing" of the rowing stroke wasn't a problem in practice.

    There's currently a project to develop a hydrofoil quad scull. Dunno if it will work or not, but sounds like fun.
     
  5. NoEyeDeer
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    NoEyeDeer Senior Member

    I find that if I'm leaning for a long catch with a fixed seat, I often find myself thinking it would make more sense to slide my butt back instead of leaning over to touch my toes all the time. It's naturally more comfortable to bend my knees on the back stroke anyway, and once I've bent them a bit it just seems natural to bend them a bit more.

    I don't know if you have ever rowed with a sliding seat (I seem to remember you had a knee problem) but it really does feel quite natural. The first time I jumped in a scull, after only doing fixed seat rowing before, and not even any of that for several years, I found the sliding seat very easy to use. You don't have to row them flat out all the time, and if you're not racing you can choose how much you want to bend your knees.
     
  6. Turnpoint
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    Turnpoint Junior Member

    I think that pedal power is more efficient than oars if setup properly--for longer distances. For short sprints it could be a wash.

    Similarly to Richard Woods, I also had a boat in the race to Alaska. The boat is mostly designed as a fast sailing boat, 24 foot catamaran, with a single pedal drive unit. We kept the length to 24 feet to minimize weight and wetted surface area to make it efficient at pedal power. We were spinning a 20 inch prop with efficiency of around 79%-- numbers from Javaprop. Our long distance cruise speed is 3.5 knots (we can keep that speed for long periods by taking one hour shifts pedalling). Our fastest we can pedal the boat is 6 knots for less than a minute.
    Also similarly to Richard we had to pedal our boat 6 miles out of Victoria before we had enough wind to sail, but we were closer to the front of the pack with the boats that were faster under human power. There were two boats that were neck and neck with us for this section--- Bareffoot Wooden boats (monohull of similar weight to us but with less wetted surface area) and team Pure and Wild (Proa of similar weight and slightly less wetted surface area). Barefoot Wooden boats had a three man team, with two crew on sliding seat rowing stations to mantain 3.5 knots for this duration. Team Pure and Wild had a two man crew with one guy pedalling and the other crew rowing about 80% of the time to maintain that speed (ther prop was smaller and not optimized so most likely in the 64% efficiency range). For the first mile of the race we were all able to drive our boats at 4 knots.

    This is all anacdotal...but it was very surprising to me that we could keep up with the Barefoot Wooden boat team in these conditions while having only one person pedalling at a comfortable pace. This experience makes me believe that pedal power can be very efficient for longer distances with the proper prop design.

    Brandon
    Turn Point Design
     
  7. Jamie Kennedy
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    Jamie Kennedy Senior Member

    On the plus side for a propeller you can get the optimal lift-drag-thrust working the entire time. For efficiency it would be a large diameter slow turning prop, and this would also reduce transmission losses. When it comes to designing it for optimal performance with the wind and sea as well as into the wind and sea, and being able to operate over a range of input power depending on the distance you are travelling, you might have to go to a controllable pitch propeller to have versatility and efficiency in all situations comparable to an efficient rowing setup. The propeller would definitely have some advantages in conditions where it would be difficult to row, like sideways to the waves. In flatwater oars assist in stability allowing the boat to be more slender with less wetted surface, and weight. I rough water this advantage goes away.

    I think the main advantage of a good rowing setup is that it provides a full body workout, and is less boring. A rowing machine type of setup could be used to drive a propeller I suppose, for the full body workout, and you might be able to have some sort of flywheel to keep the prop working efficiently through the cycle, or perhaps two rowers rowing in a horizontally opposed setup. You could also row facing forward, which I think would provide a major advantage in making it less boring perhaps than conventional rowing.

    Here's an idea: What if you had an arrangement where you are rowing facing forward with oars, in the Greek fisherman style, but with a sliding seat, while at the same time driving a propeller off of some sort of erg device when pushing off with your legs on the recovery phase with the forward facing oars. Little hard to get the head around, but could be the best of boat worlds and allow you to face forwards, and also vary how much power you want to put into either system depending on conditions. The sliding seat could be on a steep angle, which you could also vary for conditions, to make it easier to use your legs to pull you forward as part of the rowing stroke. Unlike conventional rowing it might be arms first on the catch, then back, and then legs on the final exit and where the oars leave the water. Then a long slow drive with the legs can drive the propeller and push you back up the sliding seat as you prepare for the catch. Could also recharge your batteries with such a system, but hey, that's what the sun is for. ;-)
     
  8. Jamie Kennedy
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    Jamie Kennedy Senior Member

  9. SailorDon
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    SailorDon Senior Member

    I do have a knee problem mostly related to weight on the knee joint.
    I have used a rowing exercise machine with sliding seat and noticed that sliding back on the power stroke caused knee pain. Sliding forward on the recovery stroke, bending my knees was no problem.

    What I need to "test drive" is a sliding seat skiff, like the Heritage 18.

    But this does not answer the original question of the efficiency of pedal vs. oar power. If pedal power is more efficient, why don't they have Olympic pedal boat racing? Why would they stay with oars if they don't perform. I'm thinking that there is no pedal boat design that can keep up with an competitive racing shell. I am more interested in recreational rowing, but the same principles of comparative efficiency should apply.
     
  10. Rurudyne
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    Rurudyne Senior Member

    Why no Olympic pedal boat racing?

    Because they can't agree on if the boats should be swans or ducks. ;)
     
  11. Richard Woods
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    Richard Woods Woods Designs

    That's a bit like saying "why have Olympic archery competitions" when a machine gun is a more effective killing weapon

    And what about a centrally mounted paddle wheel on a catamaran? A lot easier to make and maybe less losses so you gain efficiency.

    Turnpoint certainly "motored" very fast and effectively in the R2Ak, but, as I said before, the surprise to me was that all the boats were doing 2.5-3 knots at "cruise speed" whatever their size or propulsion

    Richard Woods
     
  12. rwatson
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    rwatson Senior Member

    A moot point - if you have knee problems, then pedal wont be the most 'efficient' power for you. :D
     
    Last edited: Jun 28, 2015
  13. SailorDon
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    SailorDon Senior Member

    If the pedal power proves to be more efficient (based on theoretical analysis), the solution is easy!
    I just get a knee replacement. :)
    (And a pedal boat.)
     
  14. SailorDon
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    SailorDon Senior Member

    Perhaps instead of replacing Olympic rowing events with Olympic pedal boat events, they should add pedal boats as a catagory of "Human Powered Vessels".
    There is a precedent in Olympic boat racing.
    Consider the variety of Olympic sailboat racing classes.
    [​IMG]

    But if you prefer replacing Olympic archery with Olympic machine gun competition, go for it! [​IMG]

    IMHO pedal boat technology has not developed sufficiently for establishing class rules for competitive pedal boat racing. Therefore, no collegiate pedal boat competition. No Olympic class pedal boat racing.
    The only pedal boat I have seen in person (other than the pool toy variety) is the Hobie Mirage flipper/fin pedal drive. In an casual contest of speed, I was able to leave two Hobie Mirage drive kayaks in my wake with no problem. I conclude that the Mirage pedal drive is not as efficient as oar power.
     

  15. portacruise
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    portacruise Senior Member

    Depending on the severity, wouldn't a knee replacement be in order (or not) whichever way you go, rowing or pedaling? FWIW- there are different efficient pedaling configurations from full recumbent to upright for bikes (and pedal boats) , but maybe not so much for rowing... Upright seems to be less stressful to my particular knee issues- at least when bike riding.

    Speaking about competition categories, why not allow recumbent bikes to compete directly against uprights, (seems like a bike is a bike)- or should recumbents really merit a separate category?

    OE
     
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