Power requirement for 10m canoe

This forum has had in the past users that got banned for ad hominems. In this thread, there are two ad hominems. One is against a supposed group of anti-electric posters. The other clear.

Please avoid ad hominems, or better, remove them with the edit button.

To be fair to Gonzo, his posts on the subject of this thread are probably the best the OP got. The customer clearly has misconceptions about the vessel and capabilities and cost. Even the OP may have a bit of confusion, the 11 knot speed, the two hour requirement and the 2km do not make a ton of sense unless they are ferrying in many loads of people the short distance or need the speed for other uses.

If you want to avoid ad hominem; it is easy. Use substantive arguments on the subject matter.

About my whirling dervish remark. I was trying to make the point that shooting anchors will also not meet the speed requirements and essentially supporting Gonzo with humor. Perhaps it was in poor taste, so I deleted it.

 

This is not a personal attack, just a reflection of reality: similarly, imagine if I went in any and all of the engine threads and posted how diesel doesn't work because it leads to human extinction repeating this over and over, the same argument then complained about "personal attacks" if anyone said I was at all biased against engines, and then I would argue I know about engines because I made coconut oil manually and its too labor intensive.

To achieve 90%+ efficiency the propeller diameter needs to be about the same as the width of the boat. This makes a huge difference in electric propulsion where battery weight and cost is significant. Typical recreational boats have 25% efficiency just at the propeller alone, the more efficient designs approach 40% at a particular speed. The engine itself has similar inefficiency, and the two are compounded with an extremely low overall efficiency of 5-10%.

Furthermore.. consider that fish/birds etc are all fuel powered but their efficiency (energy per mile) far exceeds anything we can produce.
Bird flies 7,500 miles nonstop, breaking world record https://www.livescience.com/bar-tailed-godwit-record-flight.html
"Staying in the air for 11 days straight, a bar-tailed godwit flew from Alaska to New Zealand."

There is no model plane/drone whatever with 80cm wingspan or less that comes anywhere close to what nature does every year. The same feats are practiced by fish/whales in the ocean. There is a long way to go to improve and declaring electric as infeasible means you are unwilling to explore new ideas, because after all, the original people there did not use electric or combustion and somehow they got there. Simply taking existing design that use gas and swapping out with electric is infeasible and also uses zero imagination.

So he said himself they were "unc0ntacted" until the 70s So my question if these people used 11knot speed canoes since ancient times, or if it is just a bunch of privileged westerners who are jet-set making arbitrary requirements without consideration for future generations. If it is for eco-tourism, I would argue that using combustion engines could not be allowed, and if this means reducing speed, and using alternate techniques like kedging through rapids, then these must be considered. The journey to the place without causing emissions would be part of the tourism experience. It doesn't matter if it takes 6 hours instead of 2 hours, because they are going to sit in a lodge for days anyway. The extra time on the boat without engine noise can be used to educate the tourists. Putting a 40hp gasoline engine and calling it eco-tourism would definitely be a form of fraud and disrespecting the native people of the region as well many who oppose oil exploration and the government has also done this:
Ecuador Declares Temporary Moratorium on New Oil and Mining Concessions | Amazon Watch https://amazonwatch.org/news/2022/0913-ecuador-declares-temporary-moratorium-on-new-oil-and-mining-concessions

So back to my simple suggestion is that a 30ft canoe going 11 knots is a completely unreasonable requirement. This is what needs to go away not the concept that electric is infeasible. There is no real justification for this speed other than perhaps some rapids are very fast. For this, a system that works in bursts of high power, or kedging should be employed. The boat should have oars, especially navigating downstream where the oars can be used to maintain steerage and the current does the work. My boat which is also 10 meters and 2.5 tons can achieve 3 knots at 300 watts using an electric drive that is overall not even 50% efficient.

 

TYour response is political rather than technical, so I will ignore the ranting and stay within the technical. The argument would be off topic if we were discussing diesel engine specifications. This is the same as your comments on this thread which do not address a 30 foot canoe with electric power running at 11 knots for two hours. Those are constraints.

In case you haven't looked at the calendar lately, that was 50 years ago

 

Back to the original (ridiculous) requirement.

Lets say that a 40hp gas engine can power this boat 11 knots. A high efficiency electric drive of 90% propeller efficiency could do the same using 10kw, because the gas motor has extremely low efficiency at the propeller. I've seen videos of these boats in Ecuador and I have an idea of what they are trying to replicate, the current boats are incredibly inefficient at the propeller creating a very small stream of fast moving water and turbulence.

This would realistically require a minimum of 20kwh lithium battery would cost $5k-$10k. The propeller would need to be a carbon fiber propeller of large diameter and potentially 2 contra rotating propellers of likely custom design. It would require a deep draft unless several propellers were used to sweep enough water. It is unclear if they frequently hit rocks with the propellers, but if this is the case it becomes a situation where a more durable metal propeller that is smaller and less vulnerable is also much less energy efficient.

Electric motors in this power range such as etek motors are $500. The motor controller also few hundred dollars. A planetary gear box of 2 stages is likely needed. This would cost a few thousand for the drive system. So it is after all, very feasible and possible.

In fact.. even going with an inefficient 40hp and 60kwh battery which weighs 260kg (not too heavy) it could simply replace the existing solution that way and use the small inefficient low aspect metal propeller. But considering the local people who were uncontacted since 50 years ago never did use such ridiculous amounts of power on a boat, it remains obvious that it is not needed and never was. It would be wrong to apply this "solution" and it would be a huge environmental burden similarly to the electric car which is a joke if you consider how it barely reduces environmental impact in fact depending on usage patterns such a solution could actually be more degrading to the environment.

 

That is absolutely incorrect. The power applied to the propeller is the only value that is relevant. Whether that power comes from a diesel, an electric motor or a water turbine is irrelevant. We are now entering on the realm of pseudo-science where electric HP is "stronger" than fossil fuel engine HP.

 

Outboards are rated in HP as delivered to/at the prop since the mid 80s.

 

That is correct. My response was to seandepagnier's claim that a 10Kw electric motor is equivalent to a 40HP (~30HP) electric motor. Further, as you pointed out, the 40HP rated outboard is already taking into consideration gear losses, which are not considered for the electric motor.

 

you could use any engine of any type with a 90% efficient propeller. The typical 40hp gas outboard is using a propeller with approximately 20% efficiency in this particular case. Why? because it is designed to push a boat 20-30 knots with perhaps as high as 60% efficiency in the ideal load and speed. Instead it is overloaded pushing this much heavier canoe of 2.5 tons at 11 knots and the efficiency is very poor. It has nothing to do with the type of power source and everything to do with the propeller being inefficient and mismatched.

I see this all the time, people putting 6hp gas engine on a 24ft sailboat without even changing the propeller at all. Even with an inboard which has the correct pitch of propeller, the efficiency is 25-40% Why? because the propeller diameter is too small. In nature, the animals have tails relative to their body size to maximize efficiency but for some reason the same is not true in boat propellers. The reason has to do with cost of gear box, cost of propeller, weight, and extra draft required as well as fuel at $5 a gallon being too cheap to matter if you care nothing about cost to others by external effects of pollution.

My sculling oar is 80% efficient, and human power of 100 watts can push my 33ft boat 1.6 knots and is about the same surface area as the rudder. When I compare to a trolling motor with a tiny propeller it consumes more than twice the power (250 watts) and pushes the boat slower (1.4 knots)

You all have seemingly never used a larger diameter propeller and have never used electric propulsion. Then claim to know about batteries when it is obvious to supply even 60kwh with lithium batteries is technically possible as well and keep the same inefficient propeller.

The canal boats used a single horse to pull a barge weighing up to 10-15 tons all day long. The speed 3-4 knots. Show me a gas engine of 1 horse power that can do
Horse Drawn Barge History - About - Tiverton Canal Co: One of the last Horse-Drawn Barges in Great Britain https://www.tivertoncanal.co.uk/about/horse-drawn-barge-history
Horses and Canals 1760 - 1960 - Canal Junction https://www.canaljunction.com/craft/horsedrawn.htm
Towing barges with horses https://www.energie-cheval.fr/en/menu-principal/utilisations/halage/
"can transport up to 80 tonnes of solid waste. Pulled by two horses, the journey along the bank lasts 10-15 minutes, at a speed of 5-6km per hour depending on wind and currant."

Show me a gas engine of 5hp that can push 80 tons at 3 knots. I know you will argue these horses can output more than 1 horse power in this case because of the shorter duration: I am already taking that into consideration. It is technically possible to get close to this figure, and the closest you would find is a british seagull motor which even today is more fuel efficient than modern engines despite being near 70 years old when it comes to pushing very large heavy boats because it has a slower turning larger propeller and larger gear reduction, but is horribly inefficient actual engine, and still doesn't have anywhere near the required propeller diameter. To achieve efficiencies close to theoretical maximum would require a custom design. There is nothing on the market that you guys can just buy and clamp on and because of this you probably think it is impossible.

Can we stop with the mirrors and echo chambers of ignorance trying to hold people back from realizing their goal? There is more and more and more incentive _not_ to use fossil fuels and they are even being made illegal in some places such as Amsterdam. I can only hope the OP can understand that many people simply have no experience and are biased over fear of what they dont understand (the unknown to them) which is after all human nature and repeated all over society in countless forms.

 

Oh good heavens, he is even arguing against himself now.

Electric will be too expensive and too heavy, but our inexperiences and biases are the problem.

Not to mention the massive carbon prop in a debris filled river..oi vey.

 

My pet mouse has a longer tail than a hamster of the same size; explain that.

 

Assuming that by "same size" you mean the same total length, the only thing I can think of trying to explain such a strange phenomenon is that the body of the hamster is larger than that of the mouse. Have I got it right?

 

The propeller efficiencies referred to by this mr seandepagnier are not even remotely reminding of real world performance. I want to know what sources those numbers come from (in particular 20% for "gas engine" and 90% for "any engine....").

We have lost the original poster long ago. He asked a completely relevant question about the expected power required to propel a given load at a given speed and operating radius. His client had stated a SOR including electric propulsion. Nota bene on a "lean budget"! This could have resulted in an interesting engineering discussion about optimization. Instead we get these ridiculous postings suggesting the OP arrange horse drawn barges or the out-of-the blue rantings about phantom efficiencies of electrical propulsion. If they were delivered with a smile and a sense of humour and finesse it would have been fine, but now.......it's just stupid.

If you do not understand the physics behind the propeller and the conversion of mechanical shaft power (whatever phenomenon causes the rotation) into thrust, then why do you think your speculations are relevant, or even interesting in the context brought up by the original question? What the OP needs for the task are realistic numbers that refer to the customer's SOR, explaining what can be done, and what cannot.

If you want to have a political debate about "echo-tourism" (which certainly deserves a critical survey in my opinion) then open a separate thread about it, but please stop cluttering a technical thread with unrealistic nonsense.

 

Thank you for putting this back into perspective. This isn't the first thread I've posted in, so I'm getting kind of used to everyone spending a bunch of time telling me how "unethical" this eco tourist spot is, as well as being told how ignorant I am.

If I may clarify: Torqeedo is the brand of choice because they have a distributor in the region, and the ecolodge currently has a Torqeedo 2.0 engine. Since it is being discontinued, they plan on upgrading to a 3.0. Perhaps we could persuade them otherwise if we can prove this is deficient to their needs. We have not been given a budget constraint in dollar amount, but the understanding is there is that we should keep costs minimal.

If the SORs need to be renogotiated (and it sounds like they most definitely do), I am more than willing to readress them with the client. It would be incredibly helpful to get assistance in asking the right questions to get this project on the right track.

11 knots is a top speed, not cruising. This is being built to give tours on, so cruising speed is 8 knots per customer request. Customer is requesting no roof so that the tourists can take in the surroundings (side note: interestingly Torqeedo has made a boat for the locals and it was rejected by the tribe for being....too slow). This prevents a solar paneled roof option, so sufficient power needs to be stored on the vessel.

Depth of river is in excess of 20 feet, but there are debris considerations. The river is of sufficient width that I believe an outrigger is a possibility.

The vessel needs to ferry 10 passengers sitting in rows of 2 up and down river. Stem to stern length of 10m

Material type is fiberglass.

By estimation, we expect this vessel fully loaded to have a weight of 3,500 lbs/1600kgs.

Current considerations are minimal.

I appreciate everyone's responses so far, and the apparent enthusiasm there is for this project. I wholly invite further challenges to this project as outlined. Our group is still very much at the "we don't know what we don't know" stage, so the more prodding the better. And yes, I am going to press for us to reach out to another school with a naval architecture program to assist with our project.

 

The distance from London UK to and from Ecuador is about 11,600 miles. Depending on the plane for the cross Atlantic portion, this ECO TOURIST on a per per person basis will consume, just to get to and from a major Ecuadorian airport
about 160 gallons of fuel. Then he or she might jump on say a Dash 8 to a smaller airport and to be then driven in an antiquated inefficient old beater and burn more fuel. The tourist will
be dressed in illegally replicated designer clothing that comes from the main source of carbon dioxide producing countries that burn coal to produce power to make his clothes.

EDIT These fabrics will more than likely be made with fashionable breathing cloth containing Nylon, Polyester, Spandex or Acrylic, all made from hydrocarbons

The Eco Lodge will convince the Eco Tourist that they are so ECO sensitive that they have an electric boat that will ferry them 2 km up (and I assume back for a total of 4 km) and is ECO FRIENDLY. 4 km = 2.5 miles.
10 People on the boat might use 1/2 a gallon for the 2.5 mile trip, or .05 gallons per person. Barring that the math is correct, this is about .8 of a cup of fuel.

After his short 2km trip, this tourist may then jump on the back of a methane producing animal or get into another internal combustion driven vehicle to continue on his/her trip

Then this Eco Tourist will convince himself that he is taking an Eco vacation to help save the world.

Notwithstanding hydrocarbon burn, one should factor in the depletion of the rare earth materials used to make batteries for the electric Eco Canoe

mmm???

 

From this very forum:
Prop efficiency? https://www.boatdesign.net/threads/prop-efficiency.13646/

By example torqeedo quotes 54% maximum efficiency, but this is on a 12ft boat with 1 person and nothing else on the boat. They have different models, but essentially there is only one speed/thrust for which the engine is operating at maximum efficiency and the majority of users deviate from this. Basically, when you put a random motor on something and demand more force at a lower speed than it was designed for the efficiency gets worse (propeller slip) and this is exactly what a 40hp motor designed for 25 knots pushing something 11 knots is. Furthermore, it was never really very efficient to begin with.

Take a close look at:
Tûranor PlanetSolar - Wikipedia https://en.wikipedia.org/wiki/T%C3%BBranor_PlanetSolar
If you are interested in efficiency.

The mouse and tail argument is irrelevant since the tail is not used for propulsion. Look at fish tail relative to its body, whale tail, dolphin tail, and so forth. Nature has optimized the amount of water to interact with. Try rowing a boat with a stick instead of a paddle. For this type of canoe a starting point would be, 2 contra rotating 60 inch carbon paramotor propellers at 200-300 rpm which should yield a significantly higher efficiency. Using a 16 inch aluminum propeller will yield a very low efficiency. I said nothing about specific power sources or electric having 'phantom' power. Consider both gonzo and fallout have hijacked other threads regarding electric propulsion, and neither of these guys have ever designed or used electric motors and are clearly diesel junkies. If they would not be allowed combustion engines they would both likely give up on boating entirely.

I have never used any kind of combustion engine and traveled all over the world. I have built 5 sculling oars with increasing efficiency, and propel boats 4-5 tons using human power up to 2 knots, but 1.5 is typical, and have covered more than 10 miles in a day on such boats which weigh more than twice what the OP's suggested boat is. The submerged blade part is more than 6ft long. If it were any shorter the efficiency would be lower, and with human power efficiency is important.

I said nothing about phantom efficiencies of electric, only that virtually all recreational boats regardless of propulsion system are extremely inefficient due to mismatched and undersized propellers. This is not at all specific to electric.

It is obviously relevant to compare actual real world examples of horses pulling boats to indicate the physical possibilities and to highlight just how incredibly inefficient gas outboards tend to be. If they were not, their capabilities would compare to what horses pulling similar boats can do, but they are not even close. I would conclude that your conclusion of this analysis being "stupid" is a reflection of your own statement.

I would veto your suggestion as it is entirely relevant to why electric is being proposed at all. The fact that the country in question has made recent court cases banning oil exploration is entirely relevant.

The .8 cup of fuel here is not accurate as much more fuel is consumed producing and transporting that fuel and the distance traveled appears to be 20km not 2km. Regardless: you point is clear. The difference in fuel consumed by the canoe here is < 1% of the total amount of fuel the tourist will consume in the trip, perhaps not even 0.1% and this fact should be highlighted.

Yes, I suggested before that using an electric propulsion system here could potentially be worse for the environment. The obvious way to make it more environmentally friendly is by using slower speeds.

For this same reason although it is entirely possible to replicate the speed and power of the original gas solution using lithium batteries for duration of a few hours, it doesn't make sense from an environmental perspective.