eBike technologies will transform pedal power for personal watercraft. Discuss.

Discussion in 'Boat Design' started by jakeeeef, Mar 12, 2023.

  1. jakeeeef
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    jakeeeef Senior Member

    Well, the title sets out my stall.
    I have long believed that 'pedal assist' eBike technologies will finally take pedal boats into much wider markets.

    I'm currently building a prototype of a folding, trailerable (by an eBike), ebike pedal assist powered amphibious vehicle. Aiming for Kickstarter launch next year, but let's see how the prototype development pans out. I think it will be the smallest, lightest amphibious vehicle ever made, along with a few other firsts.

    Regardless of my project, which will sink or swim largely on the marketing, I believe pedal assist technologies will make pedal boats viable outside of the one off HPBs and the occasional very low volume runs of pedalboats we see now.

    I've built a number of pedalboats (pedal power only- no electric assistance), and pedaled a few others too. Here are my thoughts:

    They are all displacement craft. This means to have the necessary LWL for bearable performance they need to be relatively long and awkward to store, or multihulls with complex folding mechanisms. Most often the ones that hit the market are short, wide and glacially slow, usually designed by inventors or mechanical engineers who have come over from the bicycle side without the first idea of or interest in naval architectural principles.

    Usually the ones that hit the market display a combination of limited marinisation, the wrong gearing,the wrong prop, the wrong hull design. Very often they manage to combine all of these limitations, but the basic forgivefulness of the liquid medium means they are still capable of forward motion to some limited degree, thus they are deemed a successful design by their makers but the market sees the shortcomings and always decides.

    Pedal boats do not generally feel pleasant to use on the water. Because they lack a terrestrial bike's flywheel and momentum effect of the wheels running on the road, they are always a slog. That first pedal stroke you take starting a bike on a steep hill: that's what every revolution of the cranks feels like on a pedal boat. Correct gearing helps a bit but there's no get out I've ever found for this scientific reality until electric assistance.

    They require a lot of moving parts compared with rowing, kayaking etc, so marinising the components is expensive, makes the boat heavy etc. (This one is immutable whether pedal assist or not)

    My thoughts on eBikes are that they are set to change everyday transport for millions as we embrace decarbonisation. Maybe, more like little e- microcars for some, as the winter limitations of open bikes are known to us all.
    The principle though, of pedaling alongside an electric motor is fantastic. It keeps you warm. It gives a small power boost when needed, such as to get a hull planing or foiling. It means you can still get home ( slowly!) when the battery runs flat. The importance of regular exercise on health is growing and growing. Pedaling alongside the motor reduces the vehicles energy usage and carbon footprint too.

    The thought of pedalling on the water, but for the first time ever at a useful speed in a conveniently storable boat, and without the sloggy feeling of traditional pedal boats makes me very excited indeed. I think other people are going to want to feel it too.

    I'm aware of the Manta electric assist foiler, and I'm hugely excited someone has done this, but watercraft that require getting wet, wearing a wetsuit, a decent level of fitness and skill etc are always niche and not what I'm talking about. I'm talking about boats anyone can get in and enjoy.

    I'm working to position myself in this market before the eBike technologies and legal framework we need are there. eBikes in the UK / EU currently are limited to 250w and in the US 500W, neither of which are much use to get a boat planing or foiling for a wide range of users. But I believe much more powerful pedal assist ebikes are on the way.

    The bikes themselves, around 4-6 kW exist, just not legal to use on road in a number of places because they currently come under motorbike law, so number plates, indicators, insurance etc required, which very few people bother doing.

    Legislators though are looking at lighter regulatory burden for powerful ebikes under a certain weight. When this happens, not only will we take a lot of cars off the road, we'll also see an increase in available technologies and reduced prices such as on torque sensing motors.

    Torque sensing is important for what I want to do. Pedal assisting a 6kW motor with your puny 300W of power is pretty pointless. But with torque sensing it can be set up to only produce its 6kW WHEN you produce your 300w. So you have to pedal like f@@@ to get it planing or foiling, if you set it accordingly. When you pedal slower, it goes slower. You can pedal more and greatly increase range, or pedal with no assist at all to increase range indefinitely.

    The idea is to get people out on the water, exercising, feeling good and like they are really getting somewhere in a boat that's convenient to store and easy to use. Something that pedal boats have always struggled with.

    What do people think? How much of a thing will pedal assist boats be ten years from now? Crazy or am I onto something?
     
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  2. Andrew Kirk
    Joined: Jul 2021
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    Andrew Kirk Pedal boater.

    Bigger power needs a bigger battery capacity, weight and expense. For a boat in displacement mode to reach 9 mph needs a hull of around 32 feet! Planing is always going to need big power so I think you're setting yourself an impossible task unless you accept lower speeds without planing.
     
  3. jakeeeef
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    jakeeeef Senior Member

    4-6kW for one up planing on a lightweight boat, is what I'm thinking. I don't class this as big power. EBike batteries are relatively cheap and very scalable. Ie., You can take a few spare batteries with you.
     
  4. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    I am of similar thoughts and beliefs jake-e.
    But I am applying it to a HP hydrofoil with e-assist as it's challenging to remain "aloft" for long under HP only.
     
  5. clmanges
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    clmanges Senior Member

    Nope.

    Not to say someone may not jump on this and try to produce and market such things, but I don't like the idea. If you want more speed from muscle power, the first thing needed is an efficient hull, which translates to 'long' (and relatively skinny).

    Put an Enviolo transmission in it (and maybe a variable-pitch prop) and leave the electrics at home; it would weigh less, be cheaper to build and buy, and be safer. A well-designed pedal boat won't need it; bikes need motor assist (which, strangely, they've gotten along fine without until quite recently) because of hills, which aren't generally a thing on the kind of water a pedal-boat would generally be used on.
    Relative to what? A good ebike battery--one that won't catch fire or just inexplicably fail for just any old reason--costs in the $500-$1000 range. And did you know that a lot of insurers refuse to cover ebikes? What do you suppose they'll think of your wanting to mix high-power electrical systems with water?

    Also, stick to displacement hulls; I still see foils as being problematic in a lot of ways (price being one), and I doubt you'd find many people who feel the need to plane ... especially since planing hulls are famously sluggish at displacement speed.
     
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  6. comfisherman
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    comfisherman Senior Member

    Isn't that kind of like asking the question will electric motors make anything faster than just Pedal Power....

    While the obvious answer is yes I'm not exactly seeing the Revolutionary part of it.
     
  7. jakeeeef
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    jakeeeef Senior Member

    On dry land, this is true. There is a pretty linear relationship between how much power you pu in and how fast you go.

    But if pedal assist opens up planing and or foiling, it represents a more significant upward move in the performance.

    Plus what I said about how unpleasant pedal boats are to use. With pedal assist they might become a lot more rewarding
     
  8. comfisherman
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    comfisherman Senior Member

    I find paddling unpleasant, and have found that Motors have revolutionized that experience for me...
     
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  9. Andrew Kirk
    Joined: Jul 2021
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    Andrew Kirk Pedal boater.

    4-6 Kw from an average E bike battery will drain the battery in 15 minuted. Except that you can't draw that kind of ampage in the first place. Generally you only want to draw 1C from a li-ion battery for a sustained period. That means you need a 6Kwh battery, which is more electric motorcycle than E bike. I built an EV before they became generally available. Expensive and far less practical than the advertisers imply.
     
  10. mitchgrunes
    Joined: Jul 2020
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    mitchgrunes Senior Member

    An eBike mechanic told me that Li-ion batteries have had some fires (that are hard to quench - water and ordinary chemicals aren't enough) and a few explosions when holes develop in the battery, as well occaisionally as when charging. He said the problems are biggest where they use salt(s) on the roads, because most battery cases corrode in saltwater. Seawater has several types of salt.

    Do the good solutions involve extra heavy battery cases?

    When you say PWC, do you mean the high powered little boats that do plane, and whose operators sometimes make a nuisance of themselves around other boats, by passing very close? In which case www.taigamotors.com/products/orca already exists.

    That example is advertised at 160 peak HP. On an eBoat of that power, is there any point to pedals? :)

    I suppose an ePWC can be a lot quieter than a typical gas PWC.
     
  11. EGComposites
    Joined: Feb 2023
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    EGComposites Junior Member

    LiFe is the answer then. Those are safe since even airplane industry uses them. High or low discharge...the options are there.
    Great idea with amphibious PWC.
    I'm a big fan of pedal assisted recumbent in the form of velomobiles. Thought of that years ago but was and will remain only a thought:)
     
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  12. portacruise
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    portacruise Senior Member

    Hi, Jake, thanks for posting!

    "I'm currently building a prototype of a folding, trailerable (by an eBike), ebike pedal assist powered amphibious vehicle. Aiming for Kickstarter launch next year, but let's see how the prototype development pans out. I think it will be the smallest, lightest amphibious vehicle ever made, along with a few other firsts."

    I have a great interest in this concept of lightest amphibious vehicle!

    I have had a lot of fun builing my own one man amphibious inflatable vehicle which fits in an Airline carry-on case and weighs well under 30 lb (including drive system, spare parts, etc.) maximum speed three knots and minimum range of 12 miles at two knots in still water down to 4 inches draft. So I can see that your concept is entirely possible, but I haven't been able to get mine smaller and lighter than that...

    A similar concept has also been done by substituting sail power assist for e-bike assist using pedaling to help when there is little or no wind, but the weight and space needed is considerably greater, well over 100 lb for the ones I have seen in the past...

    Peddling is a lot easier and enjoyable when going downhill on a bike, or the boat equivalent which is with the wind or river current at your back. The electric part can be used to help you get up the hill / upwind/ upcurrent more slowly, at a comfortable level of exertion..
     
    Last edited: Mar 12, 2023
  13. Rumars
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    Rumars Senior Member

    I see several areas of concern.
    Power to weight ratio. A 6kW motor can plane about 100kg, from that we substract 15kg for the boat, 5kg for motor and drivetrain, 25kg for a 6kWh battery. This leaves us with 55kg for the driver, wich isn't exactly standard median today. You can of course reduce battery weight for less then one hour runtime, you can accept less then full planing speed, or you can fit foils, but I doubt you can significantly reduce the other weights using existing technology.

    Gearing, it's heavy, complex and robs power. The big problem with pedal assist in a fast craft is the need to accommodate the human input of 50-100 rpm. This leaves you with several options: use a motor that develops its power at a similar rpm, then gear everything up to the needed prop rpm, wich requires a large and heavy motor. Or use a smaller motor, gear it down to accommodate the human input, then gear it back up for the prop.

    Propeller. Speed comes from rpm, so in order to plane you either gear it up considerably, or you use a big prop with the associated draft penalty, wich probably means you have to make it retractable, adding weight and complexity. If you want to be able to move the boat under pedal power alone, you either use the big prop or some form of gear shift.

    Ebike tech. I don't believe we will see any significant legal modifications in pedelecs, simply because legislators are also concerned with speed and not only power. A 4-6kW powered bike can easily reach 100km/h and has no business on a bicycle lane. The funny thing with EU law is that you can pedal your bicycle to 50km/h but electric assist has to cut out at 25km/h, and light electric motorcycles are limited to 45km/h. While I can believe that in the EU light motorcycles (mopeds, scooters) will eventually go to a 60km/h limit, you don't need 4kW to do it. There actually are some old 2 stroke mopeds that because of legal technicalities are still homologated for 60km/h and they do it with 2.7kW while weighing 78kg.

    What I see as realistic:
    Accept some lower "semi-displacement" speed or go foiling. Use a pod drive motor and have the pedals drive a small generator instead of a physical pedal to prop connection. For emergency propulsion fit the craft with oars or paddles.
     
  14. portacruise
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    portacruise Senior Member

    Yes, I think e-drive modules are the future of Transportation. We are still close to the beginnings of personal e-transportation, with dozens of ideas in development for alleviating range, Rare Minerals and ecology issues. We don't know how long the lithium battery era will last or whether it will evolve to something not involving batteries, if it turns out that lithium is not sustainable or cheap in mass production/recycling.
     
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  15. clmanges
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    clmanges Senior Member

    This is the road to least efficiency since you're adding generator losses to the existing motor losses.

    The most energy-efficient multi-gear drive system used on bicycles is the derailleur, at about 98%.

    The only 100% efficient drives are coaxial direct drives where the power is transmitted directly to the axle; typical of these are kids' trikes, penny-farthing bicycles, and simple unicycles.

    I've seen pedal-boats with this system (someone check me if I have the details wrong); they're two-person catamarans with the operators sitting transversely, facing each other and directly pedaling the prop shaft. To make these work, the prop has to be designed to give its best performance at around 60-90 rpm. There are also the paddle-wheel resort rentals we all know, which waste gobs of power pushing a bathtub-shaped hull through the water.
     
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