Pedal Powered Boats

Discussion in 'Boat Design' started by Guest625101138, Jul 14, 2008.

  1. upchurchmr
    Joined: Feb 2011
    Posts: 3,095
    Likes: 163, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    I57

    Interesting experiment with the rudders and switching the outriggers. Turning an idea into something usefull is the best part of this forum.
    Congratulations.
    Perhaps you could think of a way to try this one. Bow rudders a generally very powerful, just hard to control. If you put a short "rudder" attached on the bow, no deeper than the current bow you could have it straight ahead and not affect drag, except for a few square inches of wetted surface. During a turn, the bow would get a push, the stern also at the same time and you might get a better response. I don't have a suggestion as to how large.

    Marc
     
  2. atomas
    Joined: Jun 2011
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Portugal

    atomas New Member

    Recumbent HPB project

    Hello all! greetings from Portugal!

    I'm new to this forum, and first of all I want to congratulate all to the useful information that you post on this blog about HPB.

    I'm currently in the start-up phase of my recumbent catamaran, and I have 2 main doubts that I hope someone could help.
    1 - I made 2 hull designs that have subtle differences basically in the front of the hull. One is more agressive than the other, and I would like no now if there could be any susbtancial difference in the hydrodynamic performence.

    You can see the drawing here

    2 - I will make the hull model to construct the mould in fiberglass. I planed to make a fisbone like model in wood and fill in with styrofoam. The problem is that I want to had a finishing material to guarantee a smooth and polished surface, ready to apply gelcoat to make the mould. Do you know witch material should I adopt for finishing purpose and the same time, neutral to styrofoam?

    Thanks,

    Artur

    More information about the project in my blog:www.purepedal.com
     
  3. upchurchmr
    Joined: Feb 2011
    Posts: 3,095
    Likes: 163, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Atmos,
    If you use styrofoam, you need to fiberglass it in order to have a solid enough shape to make a mold from. I don't think there is any way around lots of sanding, then painting before you attempt to make the fiberglass mold.

    Many mold makers will make a strip planked male hull shape in order to relatively quickly get a strong enough shape for making the mold. I believe you should still fiberglass it so that the mold will match the male shape you make exactly.

    Or you could just make two strip planked hulls, fiberglassed and be able to go pedalling quicker and for a cheaper price. If you paint the hulls you can avoid lots of labor to make a nice finish on the wood. Then if you decide the hulls work the way you want you will have the male hull shape to make a mold.

    I don't think there is any difference in the two hull shapes you showed, except the Solution B will turn a tiny amount easier.

    Have fun.

    Marc
     
  4. Coach Dave
    Joined: Jun 2011
    Posts: 70
    Likes: 4, Points: 0, Legacy Rep: 40
    Location: Malabar, FL

    Coach Dave Junior Member

    pedal powered generator

    I built a pedal powered generator unit that I used to run a trolling motor on a canoe back in 2009. See picture #1. I made a wooden flywheel to supply energy during the "dead zone" at the bottom of the pedal stroke. The flywheel was sized to spin a 500 watt electric scooter at the right RPM to power the trolling motor. The seat back is leaning against the unit. Picture #2 shows us carrying the pedal unit to the lake. Picure #3 is the trail marker to Fontana Lake in the Great Smoky Mountains where we went canoeing/kayaking/camping in September 2009. Picture #4 is a side view. The trolling motor is mounted at the bow and is free to rotate 360 degrees. I have a drum on the trolling motor shaft with a rope around it to point the motor in any direction. No rudder - the trolling motor provides thrust in any direction that you want to go - forward or backwards. I also liked the fact that there is no mechanical linkage from the pedals to the prop. The downside is the poor efficiency in converting pedal power to thrust. We went 20 miles on the lake camping at water accessible sites. Picture #5 is a view from the rear. Picture #6 shows us cruising along the lake. Picture #7 - We unloaded our camping gear at Double Island and Michael tries out the pedal unit. Notice how high the seat is above the water line. A power boat went by, the wake rocked the canoe, Michael and the pedal unit went overboard. The water is 400' deep! No worries - Michael can swim and the seat base is filled with foam. We got Michael and the pedal unit back in the canoe. The pedal unit continued to work fine - we went about another 10 miles with it. When I got home I took the saw to the seat base and made it about 6" shorter to lower the center of gravity. Picture #8 - the survivors of our first ever pedal boat camping epic journey.
     

    Attached Files:

    1 person likes this.
  5. alanrockwood
    Joined: Jun 2009
    Posts: 130
    Likes: 16, Points: 18, Legacy Rep: 116
    Location: USA

    alanrockwood Senior Member

    Coach Dave,

    Do you have an estimate for the loss of efficiency using the generator-motor concept? I think motors and generators can be built to be quite efficient. It seems to me that an overall efficiency of >80% might be possible, possibly even in the 90% range. If so then the simpler coupling of the pedals to the prop for the electro-mechanical drive might more than justify a possible small loss of efficiency.

    How was the system with respect to weight?
     
  6. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 59, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    I looked very closely at this option for my solar electric boat; having a pedal powered option as a backup sounded reasonable. Motor and generator efficiency, using good quality brushless units with decent magnets and a good copper fill ratio, is up around 88 to 90% for each, so there will be around 10% power loss in the generator and another 10% loss in the motor, making a total power transmission efficiency of around 80%.

    Propeller efficiency rarely exceeds about 85 to 90% for a really well-matched large diameter, slow rpm prop driving a pedal powered boat, so you could expect a total system efficiency using the pedals - generator - motor - propeller arrangement of around 65 to 70%. This is lower than with a direct drive, where the transmission losses will be negligible (maybe a couple of percent at most), but not too shabby when compared with a conventional propulsion system. It's also still probably more efficient than rowing or paddling.

    One thing that interests me about this option is the ability to add a small battery to store excess pedal power and allow that extra power to be used for manoeuvring, going astern etc. The added flexibility this would give might make the efficiency loss worthwhile.

    Jeremy
     
  7. portacruise
    Joined: Jun 2009
    Posts: 1,145
    Likes: 44, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    There has been a lot of development is electric drive systems for land bike since the 90's by several chaps from Switzerland. Here is a paper which can be followed for other references: http://www.hupi.org/HPeJ/0015/SeriesDriveHybridVelomobiles.pdf

    The series hybrid would appear to be better than the parallel. Load leveling would seem to be the chief advantage as one could take advantage of continuing to pedal while stopped or with wind to store some energy. Better ergonomics and lower maintenance are also a plus.

    The efficiencies have been as high as 90% in direct drive land vehicle situations as I recall, but would be lower due to prop slippage in a boat...

    Hope this helps.

    Porta
     
  8. portacruise
    Joined: Jun 2009
    Posts: 1,145
    Likes: 44, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    More on electric drives, selsyns

    Another reference: http://endless-sphere.com/forums/viewtopic.php?f=2&t=4711

    This topic was also discussed on the bike power assist list may years ago. Some more advantages for boats would be ability to change output gear ratios electronically, thus easily changing torque and rpm, which might allow efficient matches with smaller props when needed. Maybe, hands free steering, and possible stability of very narrow efficient hulls without outriggers....

    The lightest and most efficient systems were configured along the lines of selsyn drives which did not encounter battery conversion losses, as I recall.

    P.
     
  9. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 59, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    Battery conversion losses are negligible with lithium cells, certainly less than 2%. The really big problem is that very high efficiency motor/generators are very expensive, as they need halbach arrays, a high copper fill and little or no iron content. Currently the very best motors (or generators) are probably the Australian CSIRO motors, but they have a very hefty price tag.

    I worked with Selsyn/Synchro systems back in the early 70's (they were the way in which pretty much every radar connected the antenna rotation to the PPI rotation, by using the motor driven antenna to drive rotating scan coils at the base of the PPI tube). Their efficiency is very poor, less than 50%, as they are optimised for position synchronisation and don't allow any relative shaft slip.

    A pedal - generator - motor - propeller system using a pair of CSIRO motors would probably get close to 95% overall efficiency. There's more on these motors here: http://www.csiro.au/resources/pf11g.html

    Jeremy
     
  10. portacruise
    Joined: Jun 2009
    Posts: 1,145
    Likes: 44, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Jeremy:

    Thanks for the link, things have progressed quite a bit since I was last looking at this.

    Great info on the battery losses. I would have expected the round trip losses to be higher because of mechanical> electrical> chemical conversion and then back through the 3 stages.

    Porta


     
  11. Coach Dave
    Joined: Jun 2011
    Posts: 70
    Likes: 4, Points: 0, Legacy Rep: 40
    Location: Malabar, FL

    Coach Dave Junior Member

    pedal powered generator

    Alan,

    My "generator" is the permanent magnet motor salvaged from my son's old electric scooter. It is rated at 500W. I don't have a convenient way to measure its efficiency. It weighs 9.4 pounds. It is cylindrical, 4 1/8" diameter and 5 1/8" long. The propeller is probably not very efficient - a high RPM, low diameter & pitch weedless model which is typical on trolling motors. I suspect there is ample room for each component in the drivetrain to be improved with time, effort and money. I went the cheap route using salvaged parts, got a functional system although I can't claim it is optimized. Mechanically decoupling the power generation from the propeller shaft drive does have advantages. A common application is a diesel-electric locomotive. A diesel engine turns a generator that powers a motor to drive the wheels. The torque/speed characteristics of the motor are tailored to the load dynamically - huge torque at low RPM to high power / high RPM when cruising down the track.

    Coach Dave
     
  12. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 59, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    If that scooter motor is a typical Chinese made brush one then it will be around 80 to 85% efficient; not too bad given the low price of these things.

    I agree about the mechanical decoupling advantages, amongst other things it allows the incorporation of features like constant pedal rate, variable prop rate, with some fairly simple controls. Those who cycle a lot seem to prefer a near-constant cadence, so I assume this has some physiological efficiency advantage.

    Jeremy
     
  13. cschaffh
    Joined: Jun 2011
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Minneapolis

    cschaffh New Member

    Pedal Powered designers,

    I learned a lot from hpb forums and its various predecessors and built my first boat in 2003. I've been off the radar for a while, but I am now building a new boat, based largely on Rick W's latest design. I'm partial to stitch and glue building, and I have posted some progress online. Perhaps I can pay it forward for those interested in this technique. It's been great following the latest developments. I'll update regularly and hope to be finished by Sept.

    pedalplusboat.blogspot.com

    Cory
     
  14. cschaffh
    Joined: Jun 2011
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Minneapolis

    cschaffh New Member

    Custom bevel gear box

    Pedal Powered designers,

    Hello again. I thought I would post some information on drive components since this is common to all boats, not just stitch and glue. There are lots of drive ideas in these forums, here is one more. It is a custom box similar to recent ones Rick has made. Materials were purchased on Mcmaster.com and bearings were purchased on grainger.com. I used flange bearings since I knew I would send the design to a shop that could machine the bearing bores accurately. It is a 4:1 ratio. It weighs 5.4 lbs with crank arms. It is not cheaper than the custom mitrpak boxes, but it is higher ratio and should have higher torque capability.

    I won't be able to try it for a few more weeks until the boat is done, but at least the gears have been proven by other boaters.
     

    Attached Files:


  15. Coach Dave
    Joined: Jun 2011
    Posts: 70
    Likes: 4, Points: 0, Legacy Rep: 40
    Location: Malabar, FL

    Coach Dave Junior Member

    I've been experimenting with unidirectional carbon fiber tape to stiffen drive shafts and decided to share what I learned so others may benefit. My starting point is my original 1/4" x 96" stainless steel shaft. The first attachments shows its compliance which I measured at 4.42 Nm/rad. One way to think about that compliance is to consider how much force it takes on a pedal (170 mm crank arm length) to deliver that much torque. With my gear ratio of 4.75 that equates to 28 pounds on a pedal. That is OK when I am spinning easily at low speed but feels mushy when I try to go faster. The next column to the right is for a 3/8" x 96" pultruded fiberglass rod with two layers of carbon fiber spiral wrapped on it. The compliance is 6.69 which is 42 pounds force on a pedal. The fiberglass rod is 0.377" in diameter which increased to 0.488" with the 2 layers of CF and epoxy. I wasn't satisfied with that so I added 4 more CF layers (see the last column) on top of the first 2 layers (6 layers total). That boosted the compliance to 19.90 which is 125 pounds force on a pedal or a factor of 4.5x my original drive shaft. The diameter of the drive shaft is now 0.642".

    The second attachment is a diagram of the drive shaft with 2 CF layers on it. I used unidirectional 11 oz./yd. CF tape for these layers. For my first attempt I bought 3" wide tape thinking I would slit it to the width I needed for each layer. This tape has polyester fill thread securing the 12k tows. Once I slit the tape to the desired width the 12k tows were loose making it really hard to work with when I wrapped it around the FG rod. I wound 3 layers on the FG rod (first layer at +45, second at -45, third layer at +45 degrees). This resulted in a lumpy mess! I didn't bother with epoxy - I pulled all the CF off and decided to start over again.

    Second attempt. I bought 1" wide tape, did not slit it, and wrapped two layers onto the FG rod. What I liked about this approach is the improved dimensional stability - no individual tows that I had to work with. What I didn't like - when you are working with a fixed width tape the angle of the spiral wrap turns out to be whatever it takes to avoids gaps or overlaps as you are winding a layer - not necessarily 45 degrees. The other thing I noticed is that the thickness & width of tape varies due to the tows not being firmly bound together. This yielded a stiffer drive shaft but was still not enough of a change.

    Third attempt. I decided to add more layers. This time I bought 9 oz./yd. unidirectional CF tape. This tape was 5" wide and has thin strips of hot melt glue on one side that bind the tows together. I was able to slit this tape to the width I needed for each layer to be at +/-45 degrees without the tows coming apart. The thickness and width of the tape seemed to have less variation while I was winding a layer than other style of tape that used polyester fill thread.

    Wetting the CF: I wound the first 2 layers, applied epoxy, put on heat shrink tubing, shrunk the tubing with a heat gun, then cured the epoxy in the Florida sunshine - we've been averaging high nineties every day! For layers 3 - 6 I wound all 4 of them then applied epoxy. I use thin epoxy that seemed to wet through 4 layers at a time without any problem. Then came the heat shrink tubing and curing in the Florida sun. A more conservative approach would be to wind one layer then epoxy then anothe layer, more epoxy, etc. Or you could work with two layers at a time - lots of room to optimize and perfect the process. If other folks try CF wrapped shafts let me know what you did and how it turned out.
     

    Attached Files:

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.