Electric motor and propeller selection for electric/hybrid boats

[MtB]

27 minutes ago, cuthound said:

 

Sadly, they can and do get in at Braunston and clog up the section between Napton and Dunchurch Pools.

 

 

Good point. 

 

There was even one here at Enslow a few years ago, not that it could go anywhere. Put in at Kingsground! 

 

Not seen it for quite a while now though. 

[peterboat]

1 hour ago, cuthound said:

 

Sadly, they can and do get in at Braunston and clog up the section between Napton and Dunchurch Pools.

Is it a widebeam section? 

[cuthound]

1 hour ago, peterboat said:

Is it a widebeam section? 

 

Technically no, but Dunchurch Pools Marina has a few widebeams moored there who occasionally venture out.

[Hudds Lad]

2 minutes ago, cuthound said:

 

Technically no, but Dunchurch Pools Marina has a few widebeams moored there who occasionally venture out.

Very rarely, most of the movements published as notices seem to be ones that come to Dunchurch to be pulled out for blacking and then for the return trip once done.

There was one moored badly in a narrow bit last year i think on the stretch between Napton and the turn at Braunston, think it was the infamous Miles Away, but only a problem if two boats tried to pass where it was. And one moored on the stretch between the turn and Braunston marina who was sat on the back being surly towards anyone who looked his way.

Only other one we've seen this year was towards Napton who was moored in a perfectly sensible spot. In our experience they're really not the problem they're made out to be round there. Must add we've never come upon any moving whilst we've been cruising though.

[cuthound]

14 minutes ago, Hudds Lad said:

Very rarely, most of the movements published as notices seem to be ones that come to Dunchurch to be pulled out for blacking and then for the return trip once done.

There was one moored badly in a narrow bit last year i think on the stretch between Napton and the turn at Braunston, think it was the infamous Miles Away, but only a problem if two boats tried to pass where it was. And one moored on the stretch between the turn and Braunston marina who was sat on the back being surly towards anyone who looked his way.

Only other one we've seen this year was towards Napton who was moored in a perfectly sensible spot. In our experience they're really not the problem they're made out to be round there. Must add we've never come upon any moving whilst we've been cruising though.

 

They are notified now, but this wasn't the case when the marina first opened.

 

I recall meeting a widebeam soon after Braunston about four years ago. There was overgrown bushes on my side, so rather than get my newly painted boat scratched, I chose to quickly moor up on the towpath side. The widebeam owner was not impressed, but why should I risk my boat when his is unsuitable for the waterway?

Edited September 24, 2023 by cuthound
To remove a space pretending to be a letter

[Lady M]

With the towpaths becoming more overgrown, your sensible avoidance tactic will now be harder to achieve.

[cuthound]

12 minutes ago, Lady M said:

With the towpaths becoming more overgrown, your sensible avoidance tactic will now be harder to achieve.

 

Yes, I do wonder if CRT's towpath vegetation policy of only close cutting the vegetation back for 100 metres per kilometre will come back and bite them on the bum if someone needs to moor urgently where the vegetation is uncut and breaks an ankle because they couldn't see a hole on the towpath edge.

 

I'm sure the "no win, no fee" lawyers would have a field day.

[Lady M]

This concerns me too.  CRT approach that the towpath does not form part of the navigation is frustrating.  Also, I noticed two or three actual gaps in the towpath near Napton recently.  Something I don't recall seeing since my earliest canal holidays.  However, the point was that you can't hop off to hold the boat on a rope while another boat passes in a narrow, overgrown stretch if you are unable to access the towpath due to excessive vegetation.

[Robint777]

Greetings Ian

 

Are you able to share your thoughts on pros and cons of the following link in terms of using this specific suppliers props on an electric propulsion application in the 15 to 30kw range of motors?

 

https://bruntonspropellers.com/autoprop/

 

I look forward to hearing your thoughts

 

Robin

[ditchcrawler]

2 minutes ago, Robint777 said:

Greetings Ian

 

Are you able to share your thoughts on pros and cons of the following link in terms of using this specific suppliers props on an electric propulsion application in the 15 to 30kw range of motors?

 

https://bruntonspropellers.com/autoprop/

 

I look forward to hearing your thoughts

 

Robin

What sort of boat are you planning to fit this to, Robin? O welcome to the forum .

[Robint777]

4 x 60ft long 36inch pontoons.  2 pontoons Starboard and 2 to Port closely spaced together with electric propulsion possibly located between each pair.

https://plasticpontoon.com/36-inch-diameter-modular-plastic-pontoons/

 

With liveaboard accommodations built on top.

 

24ft ish beam.

 

As much Solar as I can locate on roof with backup genset onboard

[IanD]

7 minutes ago, Robint777 said:

Greetings Ian

 

Are you able to share your thoughts on pros and cons of the following link in terms of using this specific suppliers props on an electric propulsion application in the 15 to 30kw range of motors?

 

https://bruntonspropellers.com/autoprop/

 

I look forward to hearing your thoughts

 

Robin

 

I would have said that for a boat on the UK canals it's not a good solution, a conventional prop works fine (especially for electric drive which doesn't have poor efficiency at low prop load) and is cheaper, a *lot* more robust, and cheaper/easier to repair if it does get damaged.

 

For a power/sailing boat in open waters an autoprop/feathering prop does have advantages, especially with a diesel engine -- better efficiency under power, lower drag under sail. Neither matters for an electric canal boat.

[peterboat]

8 minutes ago, Robint777 said:

Greetings Ian

 

Are you able to share your thoughts on pros and cons of the following link in terms of using this specific suppliers props on an electric propulsion application in the 15 to 30kw range of motors?

 

https://bruntonspropellers.com/autoprop/

 

I look forward to hearing your thoughts

 

Robin

I looked at these for my boat and couldn't see any reason to fit one, there were others on the market that were better but given the canal environment how long before a mattress destroyed it beyond repair? I think I will look at 4 bladed ones when the new more powerful motor goes in

[Jen-in-Wellies]

1 minute ago, Robint777 said:

4 x 60ft long 36inch pontoons.  2 pontoons Starboard and 2 to Port closely spaced together with electric propulsion possibly located between each pair.

https://plasticpontoon.com/36-inch-diameter-modular-plastic-pontoons/

 

With liveaboard accommodations built on top.

 

24ft ish beam.

 

As much Solar as I can locate on roof with backup genset onboard

Welcome to the forum.

I'm guessing this isn't intended for UK canals. Can you tell us where about you are going to be building and using this?

 

[IanD]

1 minute ago, Robint777 said:

4 x 60ft long 36inch pontoons.  2 pontoons Starboard and 2 to Port closely spaced together with electric propulsion possibly located between each pair.

https://plasticpontoon.com/36-inch-diameter-modular-plastic-pontoons/

 

With liveaboard accommodations built on top.

 

24ft ish beam.

 

As much Solar as I can locate on roof with backup genset onboard

But where are you going to go with it, how much time moored and how much travelling?

 

If you're in deep water then the damage problem largely goes away, but if it's always (electrically) powered there's still no real advantage to an autoprop.

[Tony Brooks]

I can see no advantage in such things unless sailing is involved. Probably more prone to damage than a conventional prop. I am having difficulty seeing how an adjustable variable pitch prop would be much of an advantage to electric propulsion.

[Robint777]

3 minutes ago, IanD said:

 

I would have said that for a boat on the UK canals it's not a good solution, a conventional prop works fine (especially for electric drive which doesn't have poor efficiency at low prop load) and is cheaper, a *lot* more robust, and cheaper/easier to repair if it does get damaged.

 

For a power/sailing boat in open waters an autoprop/feathering prop does have advantages, especially with a diesel engine -- better efficiency under power, lower drag under sail. Neither matters for an electric canal boat.

I am going electric, but exploring benifits of brunton for a coastal cruising application on pontoons. Is there any downside in your mind for this?  sorry for the newby questions,  still wrapping my mind around the torque etc at low rpm to understand if brunton offers an improvement

4 minutes ago, Jen-in-Wellies said:

Welcome to the forum.

I'm guessing this isn't intended for UK canals. Can you tell us where about you are going to be building and using this?

 

TBD,  I had initially just wanted to speak with IanD but was not sure how to communicate other than through this forum with him.  meaning yes,  not a canal boat

 

6 minutes ago, IanD said:

But where are you going to go with it, how much time moored and how much travelling?

 

If you're in deep water then the damage problem largely goes away, but if it's always (electrically) powered there's still no real advantage to an autoprop.

coastal cruising with a higher mounted accommadation similar to below.  maybe 80/20 anchored / cruising

 

17 minutes ago, IanD said:

But where are you going to go with it, how much time moored and how much travelling?

 

If you're in deep water then the damage problem largely goes away, but if it's always (electrically) powered there's still no real advantage to an autoprop.

I was wondering if an autoprop would be able to maximize the thrust at any given RPM of the electric motor thereby becoming a bit more efficient as  a whole.

[IanD]

26 minutes ago, Robint777 said:

I am going electric, but exploring benifits of brunton for a coastal cruising application on pontoons. Is there any downside in your mind for this?  sorry for the newby questions,  still wrapping my mind around the torque etc at low rpm to understand if brunton offers an improvement

TBD,  I had initially just wanted to speak with IanD but was not sure how to communicate other than through this forum with him.  meaning yes,  not a canal boat

 

coastal cruising with a higher mounted accommadation similar to below.  maybe 80/20 anchored / cruising

 

I was wondering if an autoprop would be able to maximize the thrust at any given RPM of the electric motor thereby becoming a bit more efficient as  a whole.

 

With an electric motor there's no significant efficiency advantage with an autoprop, because the motor (at least, a modern PMAC one) is very efficient (>90%) over a wide range of rpm and power outputs.

 

A diesel engine is different, if the boat spends a lot of time at power levels way below maximum -- which many boats do -- then the efficiency of a diesel engine drops off rapidly, so in this case a variable pitch prop can be very helpful so the engine runs at higher torque and lower rpm. Here's an efficiency plot (from hybridmarine.co.uk) for a typical diesel engine, the blue curve shows typical prop power vs. rpm for a fixed-blade prop.

 

 

Edited January 13 by IanD

[magnetman]

Is it an advantage to not need the variable speed power electronics?

 

Might it be more reliable? 

 

I guess for a brushless / electronically commutated motor it might not make much difference as the electronics are needed in to make it turn but for a brushed motor  it seems the motor could just be On or Off and power demand taken care of by the variable propeller. 

 

Maybe nobody uses brushed motors any more but there could be a potential reliability improvement. If your speed controller stops working it is physically impossible to get a brushless motor to turn whereas the brushed motor will still work. 

 

[IanD]

5 hours ago, magnetman said:

Is it an advantage to not need the variable speed power electronics?

 

Might it be more reliable? 

 

I guess for a brushless / electronically commutated motor it might not make much difference as the electronics are needed in to make it turn but for a brushed motor  it seems the motor could just be On or Off and power demand taken care of by the variable propeller. 

 

Maybe nobody uses brushed motors any more but there could be a potential reliability improvement. If your speed controller stops working it is physically impossible to get a brushless motor to turn whereas the brushed motor will still work. 

 

The reason hardly anybody uses brushed motors nowadays are many -- noise, reliability, efficiency, torque vs. speed, protection/sensing, propeller jam detection...

 

To run at anything other than full speed you still need an electrical/electronic controller, and once you've done this you might as well use a modern PMAC one and get all the benefits.

 

Brushed motors are simple technology from the 19th century before electronics existed, like steam engines. There are much better solutions nowadays... 😉

Edited January 13 by IanD

[MtB]

43 minutes ago, IanD said:

Brushed motors are simple technology from the 19th century before electronics existed, like steam engines. There are much better solutions nowadays... 😉

 

Diesels, for example. 

 

 

[magnetman]

11 hours ago, IanD said:

The reason hardly anybody uses brushed motors nowadays are many -- noise, reliability, efficiency, torque vs. speed, protection/sensing, propeller jam detection...

 

To run at anything other than full speed you still need an electrical/electronic controller, and once you've done this you might as well use a modern PMAC one and get all the benefits.

 

Brushed motors are simple technology from the 19th century before electronics existed, like steam engines. There are much better solutions nowadays... 😉

 

I was thinking that because it is an offshore Boat ultimate reliability might be important. 

 

As for brushed or brushless my brushed electric outboards are much quieter than my brushless electric outboards. Both have underwater pods but the brushless have a slight timing noise whereas the brushed are very quiet. 

 

 

 

It seems to me if one could simply have no electronics at all and draw power by altering the pitch of the propeller one could have a very reliable system. 

I know you think it is pointless but that is not the same as it actually being pointless. 

 

an electric motor can be run at full speed with no load and not use much power. Obviously it can then be switched orf when not needed for propeller rotation purposes. 

[IanD]

2 hours ago, magnetman said:

 

I was thinking that because it is an offshore Boat ultimate reliability might be important. 

 

As for brushed or brushless my brushed electric outboards are much quieter than my brushless electric outboards. Both have underwater pods but the brushless have a slight timing noise whereas the brushed are very quiet. 

 

 

 

It seems to me if one could simply have no electronics at all and draw power by altering the pitch of the propeller one could have a very reliable system. 

I know you think it is pointless but that is not the same as it actually being pointless. 

 

an electric motor can be run at full speed with no load and not use much power. Obviously it can then be switched orf when not needed for propeller rotation purposes. 

Running an electric motor at full speed with little or no load makes no sense, and anyway an autoprop would be noisy as hell and still can't provide the huge range of power levels needed for a boat -- see the  curves I posted. They can give better torque/power matching to an IC engine at part load and maybe remove the need for a gearbox but are pointless for electric drive.

 

If you're so worried about the reliability of the electronics, carry a spare drive module, they're pretty cheap -- and probably still more reliable than many other components in the drive system, including diesel engines with fuel... 😉

Edited January 14 by IanD