Electric Boats

[Bacchus]

3 minutes ago, Alan de Enfield said:

 

You mean like an out-drive (leg) ?

 

Our Fairline 23 when on the Thames (the Hard standing)

 

 

 

 

 

 

 

Similar sort of thing I suppose, but not on a swivel - picture of the beta marine one (actually there would be a moving part through the hull, but sealed in a pod):-

 

[Tony Brooks]

12 minutes ago, ditchcrawler said:

Why not just replace the hydraulic motor with an electric one and save the losses in a pump, motor and pipes

 

If it,s what Google images show as a DC30 then it has a wide hollow keel and the motor is mounted with about 2/3 of its diameter below the level of the main bottom part of the hull with maybe 4" of space below it. As the stern gland is in the same part, it can get very wet down there. Fine for a hydraulic motor, but I doubt it for a 40V + electric one.

[MtB]

2 minutes ago, Bacchus said:

 

 

Similar sort of thing I suppose, but not on a swivel - picture of the beta marine one (actually there would be a moving part through the hull, but sealed in a pod):-

 

 

Curious. I wonder why they are putting a four blade prop on a narrerboat.

 

 

[Jen-in-Wellies]

15 minutes ago, Bargebuilder said:

I'm not questioning you, but you've mentioned the billions that oil companies are spending on pro oil propaganda many times, but what are they spending it on?

 

Perhaps my life is a sheltered one, but I can't think of an occasion when I've been aware of being influenced to keep using or to use more oil.

Her you go.

https://www.theguardian.com/environment/2021/jun/30/climate-crimes-oil-and-gas-environment

And the billions being spent (over years)

https://www.theguardian.com/business/2019/mar/22/top-oil-firms-spending-millions-lobbying-to-block-climate-change-policies-says-report

 

Edited August 21, 2021 by Jen-in-Wellies

[IanD]

1 hour ago, Alan de Enfield said:

 

I've only (knowingly) heard one leccy-boat, as he passed I asked him, in all innocence,  if his bow thruster was stuck in the on 'on' position, he was not best pleased and didn't bother to answer, maybe it was stuck, and he was a bit miffed, or maybe it was his new electric boat and he realised he'd made an expensive mistake.

The problem is that the cheapest (and most common) way to build an electric boat is a relatively small (10kw or less) high-speed motor -- usually air-cooled -- geared down to drive the prop via a toothed belt, easily available because it's used for things like golf carts. The motor isn't quiet because there's a high-speed fan (3600rpm or more) pushing cooling air through it, the toothed belt whines, and this noise escapes through any vents needed to let cool air in and hot air out. This is what most of the electric boats out there do, and it's why they whine.

 

The next cheapest way is a standard air-cooled motor directly coupled to the prop, these are usually sized to run at 1500rpm-1800rpm for full power (10kW-15kW). The fan is still noisy but not as bad as above, air-cooling still lets sound escape through cooling vents. The prop is a tiny egg-whisk which is noisy and not very good for starting/stopping. Not as cheap or noisy as the above geared solution, but still not designed for the job. This is what most of the better (more expensive) commercial solutions use. Less whine (direct drive) but still not as quiet as they could be.

 

The most expensive and quietest way is a lower-speed water-cooled PMAC motor with direct drive to the prop like the Engiro 205W-12013 (15kW continuous at 1080rpm), which means a bigger quieter prop, no cooling fan noise, and no need to have vents to let cooling air in and noise out, can be sealed in -- I'm pretty sure this is what Finesse use. Needs extra hardware (pump, keel cooler, water cooling plate for controller) which adds even more to the cost, motor plus hardware plus controller is maybe £5000 or so. No noise except from the prop, and this is low because it's bigger and low-speed.

 

https://www.voltsport.co.uk/engiro-motors-all/Engiro-205W_12013

 

Note that the motor weighs 100lbs and uses neodymium magnets, which gives a clue as to why it's expensive...

Edited August 21, 2021 by IanD

[peterboat]

25 minutes ago, Bargebuilder said:

I'm not questioning you, but you've mentioned the billions that oil companies are spending on pro oil propaganda many times, but what are they spending it on?

 

Perhaps my life is a sheltered one, but I can't think of an occasion when I've been aware of being influenced to keep using or to use more oil.

10 million with Facebook this year! They also lobby governments, Toyota are also doing similar. 

All the hydrogen adds for transport are backed by fossil fuels companies, because most hydrogen is made from natural gas, the problem being methane leaks causing massive global warming issues!

The best adds are ones that you don't recognize as one

 

[peterboat]

21 minutes ago, IanD said:

The problem is that the cheapest (and most common) way to build an electric boat is a relatively small (10kw or less) high-speed motor -- usually air-cooled -- geared down to drive the prop via a toothed belt, easily available because it's used for things like golf carts. The motor isn't quiet because there's a high-speed fan (3600rpm or more) pushing cooling air through it, the toothed belt whines, and this noise escapes through any vents needed to let cool air in and hot air out. This is what most of the electric boats out there do, and it's why they whine.

 

The next cheapest way is a standard air-cooled motor directly coupled to the prop, these are usually sized to run at 1500rpm-1800rpm for full power (10kW-15kW). The fan is still noisy but not as bad as above, air-cooling still lets sound escape through cooling vents. The prop is a tiny egg-whisk which is noisy and not very good for starting/stopping. Not as cheap or noisy as the above geared solution, but still not designed for the job. This is what most of the better (more expensive) commercial solutions use. Less whine (direct drive) but still not as quiet as they could be.

 

The most expensive and quietest way is a lower-speed water-cooled PMAC motor with direct drive to the prop like the Engiro 205W-12013 (15kW continuous at 1080rpm), which means a bigger quieter prop, no cooling fan noise, and no need to have vents to let cooling air in and noise out, can be sealed in -- I'm pretty sure this is what Finesse use. Needs extra hardware (pump, keel cooler, water cooling plate for controller) which adds even more to the cost, motor plus hardware plus controller is maybe £5000 or so. No noise except from the prop, and this is low because it's bigger and low-speed.

 

https://www.voltsport.co.uk/engiro-motors-all/Engiro-205W_12013

 

Note that the motor weighs 100lbs and uses neodymium magnets, which gives a clue as to why it's expensive...

I can't hear my lynch motor it doesn't have a fan the armature apparently directs cooling air? I have a bilge fan on it to be certain it's ok.

For me the ease of altering gearing on the motor plus if I ever get a prop jam the belt snapping is a plus rather than other expensive damage being caused. 

[IanD]

26 minutes ago, peterboat said:

I can't hear my lynch motor it doesn't have a fan the armature apparently directs cooling air? I have a bilge fan on it to be certain it's ok.

For me the ease of altering gearing on the motor plus if I ever get a prop jam the belt snapping is a plus rather than other expensive damage being caused. 

There's no reason that a prop jam would cause any damage with a direct drive motor -- unlike a diesel engine most of the inertia is in the prop. Very unlikely to damage the motor, less likely to damage the prop than a diesel geared down with a heavy flywheel. Basic mechanics... 😉

[Bargebuilder]

37 minutes ago, peterboat said:

10 million with Facebook this year! They also lobby governments, Toyota are also doing similar. 

All the hydrogen adds for transport are backed by fossil fuels companies, because most hydrogen is made from natural gas, the problem being methane leaks causing massive global warming issues!

The best adds are ones that you don't recognize as one

 

Ah, that's why I wasn't aware of pro oil propaganda, I don't take a newspaper and I've never been on Facebook.

 

They won't be aiming their investment at me anyway, as I won't be swapping my diesel car or boat for electric any time soon. 

[Bargebuilder]

1 hour ago, MtB said:

 

Curious. I wonder why they are putting a four blade prop on a narrerboat.

 

 

To increase the disc area ratio: a common trick where a bigger diameter is not possible because of clearances  or maybe desirable if picking up rubbish from the bottom is a concern.

[nb Innisfree]

32 minutes ago, Bargebuilder said:

To increase the disc area ratio: a common trick where a bigger diameter is not possible because of clearances  or maybe desirable if picking up rubbish from the bottom is a concern.

Prob with 4 blades is less clearance between them, wider 3 blades is generally more efficient, and cheaper. 

[Bargebuilder]

4 minutes ago, nb Innisfree said:

Prob with 4 blades is less clearance between them, wider 3 blades is generally more efficient, and cheaper. 

Most definitely, you would only choose a 4 blade if 3 didn't offer the 'grip' on the water that was needed.

[peterboat]

1 hour ago, IanD said:

There's no reason that a prop jam would cause any damage with a direct drive motor -- unlike a diesel engine most of the inertia is in the prop. Very unlikely to damage the motor, less likely to damage the prop than a diesel geared down with a heavy flywheel. Basic mechanics... 😉

What happens to your inverter speed controller? Mine snaps a cheap belt its always good to have a cheap failure point and that's really basic mechanics! Shear pins for example and drive plates I have seen a couple broken through jams

[MtB]

1 hour ago, Bargebuilder said:

To increase the disc area ratio: a common trick where a bigger diameter is not possible because of clearances  or maybe desirable if picking up rubbish from the bottom is a concern.

 

You miss my point, which is to wonder why they are proposing a four blade prop on an example installation picture, produced for marketing purposes. The boat has not even been designed yet, let alone built. 

 

From this I take that they recommend a four blade prop as the default, and I am wondering why. 

[Mad Harold]

14 minutes ago, MtB said:

 

You miss my point, which is to wonder why they are proposing a four blade prop on an example installation picture, produced for marketing purposes. The boat has not even been designed yet, let alone built. 

 

From this I take that they recommend a four blade prop as the default, and I am wondering why. 

Maybe because it looks better.

To draw a comparison with light aircraft,most have two blade props up to about 250-300hp.It's only large diameter props that are three blade or more.

The theory is that one blade's turbulence interferes with the other.

There was once an experiment with a one blade prop (suitably balanced) and it was found to climb better than with a two blade prop,but was slower in the cruise.

Most props for homebuilt aircraft are made by a few caftsmen out of laminations of wood,and the performance can vary tremendously.

One of the aircraft I owned was very slow off the mark and the take off run was very long,it became known as "The Huddersfield Ground Gripper".

Changed the prop from a different maker with the same diameter and pitch,and the difference was quite marked.

I rather think that propeller making is a rather 'dark'art.

 

[IanD]

1 hour ago, peterboat said:

What happens to your inverter speed controller? Mine snaps a cheap belt its always good to have a cheap failure point and that's really basic mechanics! Shear pins for example and drive plates I have seen a couple broken through jams

The reason you need shear pins with a diesel is there's a big heavy flywheel rotating at typically 2x prop speed, meaning it needs maybe 10x the force to stop it that the prop does. With a direct drive electric it's the other way round, the inertia of the motor is much smaller than the prop, about 5x IIRC when I worked the numbers out.

 

So the force on the coupling in a jam is maybe 50x smaller than with a diesel; stop the prop and the motor just stops too. Ironically your geared motor is worse, with a 3:1 gear ratio the motor needs 9x more force to stop it -- so your belt will very likely break.

 

A modern speed controller will just current limit at the programmed peak current and then ramp this down since the motor is stalled, no damage caused.

 

It really *is* basic mechanics, at least according the the course I did at uni 😉

[IanD]

50 minutes ago, Mad Harold said:

Maybe because it looks better.

To draw a comparison with light aircraft,most have two blade props up to about 250-300hp.It's only large diameter props that are three blade or more.

The theory is that one blade's turbulence interferes with the other.

There was once an experiment with a one blade prop (suitably balanced) and it was found to climb better than with a two blade prop,but was slower in the cruise.

Most props for homebuilt aircraft are made by a few caftsmen out of laminations of wood,and the performance can vary tremendously.

One of the aircraft I owned was very slow off the mark and the take off run was very long,it became known as "The Huddersfield Ground Gripper".

Changed the prop from a different maker with the same diameter and pitch,and the difference was quite marked.

I rather think that propeller making is a rather 'dark'art.

 

It's not a dark art, the principles are well understood by marine engineers. But a lot of people in the canal world either misunderstand or misinterpret them, as can be seen by the repeated suggestions that high engine torque at low speeds is somehow a good thing when driving a prop...

 

There's actually a valid reason for using a 4 blade prop in the system shown, where the prop is very close to the hull. With a 3 blade prop, as the blades pass the hull the pressure tends to give a backwards and forwards rocking force on the shaft because when a blade passes the top half there isn't one passing the bottom half and vice versa, and this unbalanced force can cause noise and vibration. With a 4 blade prop a blade passes both at the same time so there's no unbalanced force, so in this case it can be quieter and smoother than a 3 blade. This is a known solution to reduce prop vibration and noise when it's close to the hull...

 

[and it's what I'm going to use on my electric boat, since everything else is so quiet and vibration-free the prop is all that's left]

Edited August 21, 2021 by IanD

[Mad Harold]

2 minutes ago, IanD said:

It's not a dark art, the principles are well understood by marine engineers. But a lot of people in the canal world either misunderstand or misinterpret them, as can be seen by the repeated suggestions that high engine torque at low speeds is somehow a good thing when driving a prop...

The reason I think prop manufacture is a dark art is because there are quite a few variables in their manufacture.

Diameter and pitch are the simple ones,but many narrowboat props that I have seen are little better than twisted pieces of metal.

Yes they do have washout,but how many have a proper aerofoil cross section?

There will be different amounts of washout required with different cross sections.

Some sections give more thrust at low rpm,and become inefficient at higher rpm.and some are more efficient at high rpm and just churn the water at low rpm.

The other variable is the speed of the boat through the water,hence my thinking it's a dark art.

 

[IanD]

14 minutes ago, Mad Harold said:

The reason I think prop manufacture is a dark art is because there are quite a few variables in their manufacture.

Diameter and pitch are the simple ones,but many narrowboat props that I have seen are little better than twisted pieces of metal.

Yes they do have washout,but how many have a proper aerofoil cross section?

There will be different amounts of washout required with different cross sections.

Some sections give more thrust at low rpm,and become inefficient at higher rpm.and some are more efficient at high rpm and just churn the water at low rpm.

The other variable is the speed of the boat through the water,hence my thinking it's a dark art.

 

I suspect there are a lot of props around made by firms who don't really know what they're doing, as you say they churn out something cheap that looks propellor-shaped but that's about it.

 

Then there are a few firms like Crowthers who understand design and produce high-quality props suited for a given boat but which cost more -- which might explain why they closed, too many people just look at price and don't understand quality 😞

 

The fact that optimum propeller design (including blade profile) depends on boat speed is also well known in marine circles, if not by many in canal circles. For slow boats the optimum tip speed will generally be slower, meeaning a bigger diameter slower-turning prop is better, possibly with more blades if you run out of diameter -- see attached file.

 

In other words it's not a dark art in the sense that it's black magic, it's just that a lot of cheapskate suppliers don't know they're doing it wrong and can't be bothered to learn how to do it right -- or just don't care, they're happy to flog cheap crap.

MP-Aug-Sep14_Powertalk.pdf

Edited August 21, 2021 by IanD

[ditchcrawler]

4 hours ago, Bacchus said:

 

 

Similar sort of thing I suppose, but not on a swivel - picture of the beta marine one (actually there would be a moving part through the hull, but sealed in a pod):-

 

I have the same type of motor but mine connects to a standard propshaft and doesnt get wet in a trad stern boat

[TheBiscuits]

5 hours ago, MtB said:

 

The bit that puzzles me, is how do you get the horse to use the composting bog?

 

 

 

You know nose bags?  Exactly the opposite ...

[ditchcrawler]

1 minute ago, TheBiscuits said:

 

You know nose bags?  Exactly the opposite ...

Just like on the Gt Yarmouth sea front

[Guest]

3 minutes ago, TheBiscuits said:

 

You know nose bags?  Exactly the opposite ...

 

Horse poo catching bags are actually a 'thing'.

 

Often used on military occasions and displays.

[MtB]

27 minutes ago, TheBiscuits said:

 

You know nose bags?  Exactly the opposite ...

 

Can't say I've ever met him.

 

 

[Alan de Enfield]

43 minutes ago, TheBiscuits said:

 

You know nose bags?  Exactly the opposite ...

 

Are they not known as 'bum-bags' ?