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

You are right, but not within the constraints of the SOR. The 300W the human is able to contribute is only used to make him feel good and govern the main propulsion motors power output. Losses are irrelevant, but weight is not, and the small generator gains you not having to mechanically transmit the power from the pedal to the prop. A derailleur is indeed the most efficient, until you have to build one that whitstands 6kW continuously while beeing weight constrained.

We can discuss what is the most efficient way in terms of weight and power, if it's a small, high reving, submerged motor coupled to a planetary gearbox, or an inboard with shaft drive, with or without gearbox, but for that we need more data from the OP.

 

At slower speeds paddle wheels can be efficient, which might open up use of friction drive units- some are very small (but how wet can they get?):

Velogical shrinks the rim drive to "world's lightest" e-bike drive https://newatlas.com/velological-worlds-lightest-e-bike-drive/31976/

Rick’s advice on paddle wheels from another thread- maybe use a plastic BMX wheel with the Velological? 16’ Tri configuration?

https://www.boatdesign.net/threads/pedal-driven-paddle-wheel-boat.33011/reply?quote=370937

 

It isn't derailleurs themselves that are the weak point. Their beauty is they operate on the lazy side of the chain. What I replace CONSTANTLY on my high powered eBikes are chains and cassettes. Obviously these have been optimised to offer between 6 and 11! gears in a very constrained width because that is what the market has asked for. Chains have got narrower, sprockets thinner.
The mid drive ebike market is now asking for something else: moped gauge chains running to a wide spaced 3, 4 or 5 speed cassette. Whoever develops and launches such a system will hoover up the mid drive ebike market. People with ebikes are sick of buying a £30 chain every 1500 miles!
Ebikes need very few gears, but they do need gears. They do not need to worry about their transmission weighing 500g more than the latest Shimano 1x11.

 

Yes, at one stage I was thinking a lot about designs for retracting propulsion systems for foiling HPBs. Just lightweight affairs, preloaded using bungees and a trigger. For getting motor assist to help get foilborn then hit a single trigger to snap the driveshaft and prop up out of the water. Strikes me as quite easy to do. Basically a shaft drive that runs down the middle of a centreboard type affair. But I was primarily looking at SUP, kayak, rowing etc foiling, if you're pedal powering, obviously there's a need to keep the prop in the water.

The next prototype of my boat that drops in a complete ebike for propulsion will likely have this 'shaft drive in a centreboard case' system, not to retract the prop on the water, but to retract it when towing the (folded up) boat on land, where the very spindly two bladed high aspect propeller will be retracted into a void at the transom to protect it.

The power to keep a boat on foil and the power to GET a boat on foil are two very different things as we all well know.

I was also looking at a pure human powered foiling SUP, which would be the first one capable of sustained flat water foiling, rather than the much publicised short duration pump foiling. It would be a fast raceboard with 6 knots cruising speed, but a foil Dropoff speed of circa 5 knots (big foils).
Of course its foils need to be entirely out of the water to get to its 6 knots. So I devised a mousetrap of highly preloaded bungees to flip the three foils down once the paddler got to 6 knots! (Port and starbord main foils just aft of the center of balance, front steering foil at bow also controlled pitch with shutt strut) The trigger was a big, like one foot square hinged flap on the foredeck so the paddler would sprint up to flat out, then swap sides with the paddle, flapping the trigger in the fraction of a second the paddle blade passed over the foredeck clipping the trigger and deploying the foils on its way past. The trigger once deployed lay flat and had a deep groove in it for the paddle blade to actuate the steering of the shutt strut. Just little tweaks here and there that would require a few big paddle strokes first to get the foiling glide time long enough to tweak the steering. All very complex and entirely carbon and epoxy, probably rewiring a lot of autoclave/ prepreg work that I am not set up for.

Few problems with this. It's using stored energy making it illegal for any kind of sport, even HPB. It was reloadable on water, but would have taken a few minutes winching the bungees back up like a mediaeval crossbow! It was also likely to be highly dangerous. The worst thing would be to trigger the foil release on dry land- it would have been built so light, a foil release on dry land would have destroyed it and probably fired a splintered carbon hydrofoil across the carpark at about 150 mph.

I think these type of boats will 'be a thing' too, (electric assist to get on foil or keep on foil once knackered- not my human mousetrap!) but I have to focus on the job in hand!

 

The beauty of course of just having a battery and motor that only has to operate for max 30 seconds at a time to get a foiler foiling is you can use small RC lipos etc. Not have to worry much about motor cooling.
Even if your total run time was 5 mins at WOT, if getting on foil takes 20 seconds, that's 15 times you can get back on foil after a stop. Long enough for anyone spending say an hour or two on the water paddling.
But I m getting sidetracked. The above is 5% motor/ 95% human, which as an ageing former athlete is very interesting to me, bit it's quite niche. (Athletes want 100% human power so it would take a great change of ethos).
What I'm talking about is something more like 80% motor, 20% human, and full time motor assist of some sort, with the human input fairly optional. Not aimed at athletes, but everyday people.

 

I think the idea of pedal assisted electric drive is excellent but in a displacement, not planing/foiling boat. I think the displacement version would be a more commercially viable proposition because it would appeal to more people. Between 20% and 10% proportional human contribution. My own 14ft rowing/electric outboard makes quite big bow and quarter waves at 1000W and I think that would be the power level to aim for to make use of a reasonable battery size. Most people moaning about lithium batteries have probably forgotten that their mobile/laptop/cordless tools use them - and that liquid lead acid batteries produce hydrogen gas when charging - and that petrol/gas is quite a big fire risk which we've all learned to live with.
EDIT Add the facility to vary between max and min human input, and electric only or human only.
But what happened to the interceptors idea?

 

I like your ideas and enthusiasm, being a cyclist and canoeist myself. With perseverance, and a lucky break with a cheap technological advancement, you may have the next toy for those who can afford it. The nay sayers have points, but all can be overcome if you research, have heaps of money, some ingenuity, and time.
Nested car topper or car boot sizes, and able to store in a small upstairs apartment would be huge selling points, and almost impossible to do.
Modern batteries can overheat, and blow up, with many houses lost to battery recharging fires, but there are billions of batteries out there being used, so not bad odds.
For hundreds if not thousands of years, people have been floating about in leaky tinder boxes of wood, and many miles of hemp fibre rope, and floor boards soaked in oil, lanolin, fuels, foods, and other hazards, while carrying a constantly burning wood stove; would you call that 'safe' ?
For decades ships and submarines have floated about with high explosives, volatile fuels, and a substance that is deadly for at least a million years; would you call that 'safe' ? Electric submarines have been around a while, and sure some have failed, but they're still being made and used.
I think we can live with 50 or so volts, (not enough to stop your heart usually) and a few KW of power, encased in waterproof, fire proof, explosion proof cases, specially made to stop the smoke from escaping even under salt water. All modular and hermetically sealed. It's not hard, just expensive.

Go for it before the killjoys put useless restrictions down to help justify their existence. I had a great 32cc 4 stroke motorised touring bike, with low range power for very steep hills, before the cops made all petrol motors illegal here, and all E bikes MUST have an EU sticker, and 250W max, or they're illegal. In my state I'm allowed an unregistered 4Lb of thrust from an electric outboard motor, on a canoe only, and only if I get a written exemption from the head bureaucrat of boating here. Now really, what is the point of that ?
Best of luck and good fortune to you, and have fun while doing it.

 

I only mentioned the existing 150 hp electric PWC, because the o.p. used the word "PWC". If the o.p. is talking a maximum speed around 6 knots, they are not talking about what is usually called a "PWC".

I trust you know that there are entirely human powered "planing" boats, that need a lot less than 6 kw to plane with the human operator on board.

First off, "planing" doesn't mean the same thing to everyone. If you mean that the bow (front) (and sometimes the stern=back) is somewhat lifted, but still stay in the water, virtually all modern whitewater playboats (except race boats, creek boats and squirt boats) and surf boats do that, even at fairly slow speeds. It makes them easier to maneuver and play with, and it makes it easier to surf waves. I think short surfboards did that first.

If you mean that the bow comes entirely out of the water, high end athletes can do that with some whitewater and surf kayaks and canoes, even on flatwater, for brief periods.

Most whitewater and surf paddlers can do it for long periods while front surfing a wave. But gravity provides the power to slide down against the current at the front of the wave, so I guess that doesn't count.

There are also a number of single and double human powered hydrofoils, like Flyak, that can go fairly short distances, with nothing but the foil immersed, under purely human power. Some have used an in-air propeller, though some have been paddled. They have mostly been banned from canoe and kayak races. I'm not sure why.

I don't know how much power high end athletes generate in spurts. But I recall, many years ago, in relation to human powered aircraft, something that said some could generate about 2 HP, though I don't recall for how long.

Horses can generate a lot more than 1 hp in sprints. If you use one or more horses to power your boats, I wonder how that would change things. Though horses are heavier than humans.

The problem is, to plane at relatively low power, whitewater and surf boats are shaped so as not to be very efficient over long flatwater distances, because less power is available from humans over long distances. At those power levels, those boats cease to plane, except in the sense of somewhat lifting the bow and maybe stern. AFAIK, displacement hulls are more efficient than planing boats at single-human power levels over long distances.

An interesting question is what possible use would a low power pedal/electric in question have. I guess it might make sense in permanently or sporadically flooded cities, like Venice, but otherwise, I think they would mostly just be for recreational use and exercise - in which case, why include a motor? If you go with paddling clubs, they would mostly consider it cheating, just as most bicycling clubs consider eBikes cheating. I think most people in those clubs are more tolerant of pedal boats than they would be of pedal/electric boats. And sometimes a few people in them add small sails, especially kite sails.

However, the number of permanently or sporadically flooded cities could increase due to climate change. That could dramatically increase your market. Maybe you should pray for the rapid collapse and melt of Antarctic Ice sheets! You could also advocate for disallowing fossil fuel powered boats. That's already true in some reservoirs. Electric motors have become more common there.

I have wondered why Hobie and Jackson Kayak both specialize in the stable-but-slow-and-heavy market, when it comes to pedal and pedal/electric boats. (BTW most of what each of those sells is not electric, and most of what Jackson sells isn't pedal either.) I think the designers and engineers at both companies are good enough to make a pedal/electric boat lighter and faster. They just don't seem to think that market is large enough to bother.

 

To clarify, I'm not talking about waterjet propelled high speed water craft. Taken literally personal watercraft simply means watercraft intended for one person. That's how I'm using it anyway.
The term PWC with reference to seadoos etc was picked up by authorities, national governing bodies etc when Kawasaki started getting possessive over it's trademark (Jetski), which they are still sitting on even though they stopped making the things decades ago.
Long before Jetskis, personal watercraft meant just that. I'm using this earlier meaning. Sorry for any confusion. I still use the initials PWC for Jetskis, Seadoos etc.

The battery powered PWC you mentioned has tried to replicate the performance of a 100 hp+ gasoline powered PWC. It's not a great way to go because the deep vee hulls are designed for quick turning etc. Ie., For fun and games not energy efficiency. When you take something like that and electrify it, you've got to be prepared to lose a lot of top speed, make it more efficient and use it completely differently. An electric PWC should by rights only do 20 knots max to have any kind of usable range, but I guess the market just won't accept that right now.
What they have done is tried to keep as much of the performance as they could, resulting in a laughable battery range.
It's intended primarily for environmentally conscious superyacht owners, with the idea of carrying lots of spare batteries and having readily available charging facilities. A very niche thing.

If I was an environmentally conscious superyachter, Id go for efoil boards for my pampered guests to play on. Longer range, more challenging to learn than just sitting on a Jetski (sorry Kawasaki), and a lot easier to launch, store, charge. But I'm getting sidetracked again!

 

I'm still doing the interceptors, Alan, and, confusingly they are going on the same boat.
The ebike 'accommodation' in this prototype hull is all removable, so I'm also able to play with the same hull with some outboard engines.

That's part of the reason I'm playing with interceptors on it, a way to (somewhat) optimise it between planing and displacement configurations.

 

Thanks for the response.
Where in the world wide web is "Hamble"?
Must be in the USA, no?

Okay, a few things for your considerations:
- Direct pedal generator to motor drive (drive-by-wire), no need for a drive train
- Variable shaped foils that change shape according to speed
- Inflatable bladder surrounding the motor/battery pod that inflates and deflates as needed (good for "take-off)
- Computer controlled leveling (borrowed from the R/C world) allowing for a single strut

Not quite what your looking for but might get you thinking further outside the box.

 

Hamble is on the South coast of England, outside Southampton.

On the variable shaped foils- this is the benefit of (otherwise relatively inefficient v-foils- the further they rise out of the water the smaller they get. Vee foils can be twisted so that outer sections have a greater angle of attack than inner sections.

The books say Vee foils are basically inefficient though- I wonder if they will make a comeback? They also create a boat that rolls the right way in turns, which is a nice tendency to have in a boat.

The computer controlled levelling is the big enabling device for companied like Artemis Technologies, although theirs uses AI capabilities too to attempt to read seastates to an extent.

I'm not sure about an inflatable pod around the motor, but perhaps am not visualising it correctly. I am deeply interested however in hulls that change shape according to speed in one way or another. I'm surprised there has not been more of this. A planing hull's actual footprint changes shape according to it's speed of course, but I'm talking about swapping foils round on the fly, pulling planing surfaces in and out to change the actual shape of the hull etc. Trim tabs and interceptors do this to an extent, but I've always fancied building something that changes more major things on the fly like entire rocker or deadrise.

Once again though I'm getting sidetracked and ought to get back to the pedalo!

 

something like IMOCA foils maybe? Not quite vee foils….

 

To the original question, the elegance of an e-bike is that it still feels basically like a regular bike, has relatively the same footprint and weight, and importantly, you can ride one effectively with the motor turned off. I'm afraid I don't see the point of an "e-boat" that requires 30 times the power that an average human can generate (being generous here at 200 watts) for its basic function. It would essentially be a power boat with an on-switch that requires continuously spinning your legs in circles. Why not keep the efficient hull design and portability but just have it be a nice little electric runabout?

(I do dearly hope that e-bikes revolutionize transport, along with vast networks of cycle paths segregated from large vehicle traffic, but that's probably just a dream)

 

No Jake, there is a Hamble in Tennessee USA.
You may want to add a bit more detail in your Location to avoid confusion.