Can they Re-Invent Motor Yachting?

[jfm]

Yeah but a motor boat effectively spends its whole life going up a hill. Number of engines is irrelevant, it's energy usage that's the issue for motorboats.

You have hit the nail on the head Pete. Energy and power are dimensionally totally different things. Power is what drives a boat at 20 knots instead of 1knot; energy is what gives it a 300nm range instead of 1nm. Torque is an interesting bit of detail but not the main event in these physics basics.

You can easily get electric motors with enough power to make our boats do the 20 knots (or whatever) that we want. The problem is getting enough energy on board to give the 300nm or whatever range we want. You really have to understand this to see the problem. The data is below (all my numbers are rounded/ballparky). Source https://xtronics.com/wiki/Energy_density.html

----------------------------------------------- Lithium batteries---------- Diesel fuel
Energy density based on weight--------- 200wh per kilo------------ 14,000 wh per kilo
Energy density based on volume--------- 600 wh per litre--------- 13,000 wh per litre

Remember, wh is a measure of quantity of energy.
The difference here is massive. My boat has 7000 litres/6 tonnes of fuel to give me the range I want. If we assume a generous x3 advantage to batteries on efficiency, the boat needs 140 tonnes of batteries to get the same range as now, which sinks it (and which massively increases the power needed for 20 knots, which is an iterative bit of maths that I haven't included because I don't want to kick the battery while it's down). And the boat needs 50,000 litres of batteries, which leaves no room for cabins so I might as well hang up my boots.

Same ratios for everyone else's boat.

THIS is the problem

But electric is different, instead of one engine you can have a motor at each wheel. So a big boat might look like one of those American fast fishers with a whole row of huge outboards on the stern

This is a bit irrelevant.

When Tesla makes their big electric trucks a success then there will be the ability to have the drivetrains marinised

Nope. Its all about energy density - see above.

But a motorboat has an advantage, there’s plenty of room for solar panels and generators (whatever they are running on). Besides electric motors have a good torque curve (flat line)

Torque curve isn't flat but is irrelevant here.

You could cover the whole boat in solar panels and you still wouldnt generate enough electricity to push the boat along at just a few knots, let alone 20kts. And this is a very generalised statement but torque only gives you acceleration. To maintain a boat and any given speed you need a given amount of power

First and third sentences agreed. 2nd sentence very wrong physics.

Yes but it’s instant torque (full torque at zero revs) so that has to go someway in pushing a boat efficiently

Erk no this isn't the physics of the situation.

Remember also that batteries degrade. Your boat might have 300nm when new, then 200nm when it is a few years old. Niiiice.

 

[jfm]

The reality of hybrid boats is that you can only cruise a few miles at dead slow speeds and then, if you want to go faster or cruise for any distance, you have to start the diesel engines. So, at that point, all the electric motors and batteries are doing is adding weight to the boat and increasing fuel consumption. So, if you want to do a bit of green willy waving to your mates in the marina, you leave your berth under battery power but as soon as you're past the breakwater and out of sight, you switch your diesel engines on

Yup, exactly. The car benefit of energy recovery while braking just doesn't happen on boats.

 

[Deleted User YDKXO]

First and third sentences agreed. 2nd sentence very wrong physics.

I'm aware of that which is why I was careful to use the phrase 'generalised statement'. What I was trying to say was that an engine needs both power and torque to accelerate to a certain speed and power to maintain that speed. An engine with bags of torque and no power is a pretty useless engine and vice versa

 

[jfm]

It exists allready https://www.silent-yachts.com/
... the batteries thing is very bad for the environment, production and dismantling wise. Not during use but to produce.

+1

It exists allready https://www.silent-yachts.com/
Hydrogen is the real solution...

Remember that hydrogen is an energy carrier not an energy source. Hydrogen doesn't occur naturally, so you have to make it from water, which requires energy input (somewhere remote, obvs). So it is like a battery that you have to charge from scratch before use. In contrast, diesel is an energy source: you only need to dig it out of the ground because it is already pre-loaded by nature with energy.

 

[gordmac]

I think the arguement for electric motors giving more efficient propulsion is based on the high torque at zero speed being able to turn a larger diameter therefore more efficient prop. If you have the space for it this may be an improvement, what sort of prop slip do we get normally?

 

[Portofino]

I think the arguement for electric motors giving more efficient propulsion is based on the high torque at zero speed being able to turn a larger diameter therefore more efficient prop. If you have the space for it this may be an improvement, what sort of prop slip do we get normally?

Yep running a geny provides the “ energy “ to power the electric motors .
Here’s an example
https://arconyachts.com/en/shipyards/palumbo-shipyard/sales/columbus-40s

They actually do an all “ E “ version or you can spec it .

Wether this can be shrunk down for the average Joe,s boat remains to to be seen .
It’s all just a social conscience thing, not critical but makes entry into boating acceptable to a slight wider audience, Greta,s ballooning that audience .
As as it sells boats , to tree hugger type , - arty farty folk with zero scientific neurone count .

 

[jfm]

I'm aware of that which is why I was careful to use the phrase 'generalised statement'. What I was trying to say was that an engine needs both power and torque to accelerate to a certain speed and power to maintain that speed. An engine with bags of torque and no power is a pretty useless engine and vice versa

The world is full of torque/power misunderstanding, starting with every motoring journalist ever. The statement "an engine needs both power and torque to accelerate to a certain speed and power to maintain that speed" is profoundly wrong. I mean it isn't correct on any level whether generally or precisely.

1. An electric engine can make torque with zero power but by definition it and the vehicle it drives will be stationary in that state.
2. An IC engine cannot make torque without also making power at the same time.
3. A vehicle (or anything else like a lift, a crane or a conveyor belt) needs BOTH power and torque to accelerate and to hold a constant speed. This is 100% opposite of what you just said.

For anything that is being made to move against drag by a motor/engine, there must exist BOTH torque and power in the engine. If there were just torque but no power it would be stationary, and if there were power but no torque you would be in lala land because that is an impossibility. This is a fundamental bit of physics, profoundly fundamental. These are basic building blocks of the science here.

An engine with bags of power and no torque is inconvenient in a car but is not generally useless. By definition it must operate at an incredibly high speed, and you can get plenty of torque just by adding a gearbox. Inconvenient in a car because big ratio gearboxes are big and noisy. But such engines are perfectly fine in other circumstances eg an aeroplane jet engine

 

[jfm]

I think the arguement for electric motors giving more efficient propulsion is based on the high torque at zero speed being able to turn a larger diameter therefore more efficient prop.

Really it isn't. The high torque/zero rpm moment lasts for a few seconds out of a 1 hour/10 hour cruise. It's irrelevant.
For sure an electric motor can be more efficient than a diesel, in terms of how much of the energy taken from the battery/diesel get turned into energy to push the boat, but none of that solves the fact I need 140 tonnes of batteries on my boat (indeed, I include a very generous x3 efficiency factor in favour of electric in my maths).

 

[MapisM]

none of that solves the fact I need 140 tonnes of batteries on my boat

Yup, that's the crux of the matter.

A few years ago I had an opportunity to visit Planet Solar, which is supposedly the pinnacle of electric-only boats.
The whole deck is covered with solar panels, which makes her a totally useless vessel for anything else than an experiment.
She carries around almost 10T of lithium batteries to keep going at night (albeit at reduced speed).
And yet, 7 kts or so is the best cruising speed she can maintain on glorious sunshine days.

If that's going to affect the future of pleasure boating, it's a future I'm not even remotely hoping to witness, let alone enjoy!

 

[Bouba]

You have hit the nail on the head Pete. Energy and power are dimensionally totally different things. Power is what drives a boat at 20 knots instead of 1knot; energy is what gives it a 300nm range instead of 1nm. Torque is an interesting bit of detail but not the main event in these physics basics.

You can easily get electric motors with enough power to make our boats do the 20 knots (or whatever) that we want. The problem is getting enough energy on board to give the 300nm or whatever range we want. You really have to understand this to see the problem. The data is below (all my numbers are rounded/ballparky). Source https://xtronics.com/wiki/Energy_density.html

----------------------------------------------- Lithium batteries---------- Diesel fuel
Energy density based on weight--------- 200wh per kilo------------ 14,000 wh per kilo
Energy density based on volume--------- 600 wh per litre--------- 13,000 wh per litre

Remember, wh is a measure of quantity of energy.
The difference here is massive. My boat has 7000 litres/6 tonnes of fuel to give me the range I want. If we assume a generous x3 advantage to batteries on efficiency, the boat needs 140 tonnes of batteries to get the same range as now, which sinks it (and which massively increases the power needed for 20 knots, which is an iterative bit of maths that I haven't included because I don't want to kick the battery while it's down). And the boat needs 50,000 litres of batteries, which leaves no room for cabins so I might as well hang up my boots.

Same ratios for everyone else's boat.

THIS is the problem

This is a bit irrelevant.

Nope. Its all about energy density - see above.

Torque curve isn't flat but is irrelevant here.

First and third sentences agreed. 2nd sentence very wrong physics.

Erk no this isn't the physics of the situation.

Remember also that batteries degrade. Your boat might have 300nm when new, then 200nm when it is a few years old. Niiiice.

Well, I feel like I’ve had a right kicking, and I didn’t even intend to support electric boats as I don’t generally support electric cars! But the reality is, there are electric boats, cars, trucks, planes and submarines (although submarines have an advantage). And there are electric planing boats. And it takes a lot of physics to prevent scaling up

 

[MrB]

Anyways it seems Fairline is copying the Bluegame feature by extending the Targa 53 and making it become a 58, and creating a similar stern layout.

The new Sunseeker 87 has a similar stern layout and I'm guessing it's a stretched 86.

 

[PowerYachtBlog]

Speaking of re-evolution. This is an amazing boat, and unfortunately in Europe it will pass very much under the radar, because it does not has the glitch we die for.

But it's balance, the versatility of the aft cabin is amazing. Hey I am still surprised no one thought of it at this level and size before. This is Maretimo second X model after they launch its 60.
Beyond the aft cabin feature, there is also so much versatility in this boat, range, not really over powered in its size, and very thought out balance.
It's a pity some details, (although it does look very well made) is not to the panache of some of the Europe's high end production builders.

https://youtu.be/llve_xZaNFk