Installation of new electric boat charging bollards

[IanD]

30 minutes ago, MtB said:

 

I had a brief lock-side chat with an electric narrowboat owner last summer. The brief info gleaned from the chat was he had 3.5 tonnes of LA full traction batteries, CCed about five hours a day on average, and charged with a diesel genny for 6 hours every third day. All electric cooking, dunno about heating. No solar. 

 

 

Boat worked well for them and very pleased with it, they said. 

 

 

Solar makes a big difference; I reckoned on propulsion typically using about 14kWh/day for 8 hours cruising, 2kW of solar panels in summer replaces half of this. Domestic use is on top, obviously...

 

I doubt that he had 3.5 tonnes of LA, the biggest DIN 2V standard cells are 1860Ah -- *way* bigger than most hybrid boats use -- and these weigh about 100kg each, so 24 would be 2.4 tonnes -- and would need an *enormous* generator (and inverter/combo) to charge up in 6h (>100kWh input), allowing for equalisation and inefficiency. Most LA boats (including Hybrid Marine) use 800Ah-1000Ah which weigh about 1.0-1.25 tonnes.

Edited May 5, 2022 by IanD

[MtB]

2 minutes ago, IanD said:

 

Solar makes a big difference; I reckoned on propulsion typically using about 14kWh/day for 8 hours cruising, 2kW of solar panels in summer replaces half of this. Domestic use is on top, obviously...

 

I doubt that he had 3.5 tonnes of LA, the biggest DIN standard cells are 1860Ah -- *way* bigger than most hybrid boats use -- and these weigh about 100kg each, so 24 would be 2.4 tonnes -- and need an *enormous* generator (and inverter/combo) to charge up in 6h, allowing for equalisation and inefficiency. Most LA boats (including Hybrid Marine) use 800Ah-1000Ah which weigh about half as much as this.

 

 

Just what the chap told me.

 

I have to say, I doubt his technical competence as I commented that his batts must be getting sulphated with only six hours of charging as this would never get them back to 100%. He understood the point but said that that traction batts don't need to ever be fully charged as they don't sulphate. 

[IanD]

1 minute ago, MtB said:

 

Just what the chap told me.

 

I have to say, I doubt his technical competence as I commented that his batts must be getting sulphated with only six hours of charging as this would never get them back to 100%. He understood the point but said that that traction batts don't need to ever be fully charged as they don't sulphate. 

 

Wow, that's great news -- maybe he should tell the battery manufacturers and all the battery experts that they're wrong then? 😉

 

I wonder how long he's been doing this, and how much battery capacity he's lost by now?

[MtB]

Just now, IanD said:

 

Wow, that's great news -- maybe he should tell the battery manufacturers and all the battery experts that they're wrong then? 😉

 

I wonder how long he's been doing this, and how much battery capacity he's lost by now?

 

I think the boat was about ten years old. He said lithiums were just coming on the market when he had it built and he didn't trust the technology so stuck with LAs. My guess is down to about 50% by now! 

[Guest]

2 hours ago, peterboat said:

Found the advert 232k and transferable moorings 

 

 

Not quite a typical example is it?

 

Its clearly being marketed as an alternative to a house or flat in the countries capital.

 

I doubt they would be asking that sort of figure if it was moored in Castleford.

 

 

Edited May 5, 2022 by The Happy Nomad

[MtB]

 

Which also supports his assertion he had 3.5 tonnes of battery. He can handle the loss, so far! 

[IanD]

10 minutes ago, MtB said:

 

Which also supports his assertion he had 3.5 tonnes of battery. He can handle the loss, so far! 

Ten years without ever charging to 100% and equalising -- I'm surprised he's got even 50% capacity left, and no shorted cells.

 

3.5 tonnes would mean 130kWh of batteries, which is insanely big for a narrowboat (or even a wideboat!), and would need a humongous (cost too...) generator and inverter to charge them up in any reasonable time. But maybe he doesn't bother... 😉

Edited May 5, 2022 by IanD

[peterboat]

2 hours ago, MtB said:

 

I find that amazing!

 

 

I find it amazing that some beaters live in hovels!!! 😩

[peterboat]

3 hours ago, MtB said:

 

I had a brief lock-side chat with an electric narrowboat owner last summer. The brief info gleaned from the chat was he had 3.5 tonnes of LA full traction batteries, CCed about five hours a day on average, and charged with a diesel genny for 6 hours every third day. All electric cooking, dunno about heating. No solar. 

 

 

Boat worked well for them and very pleased with it, they said. 

 

Just think of how much easier and cheaper it would have been with some solar as well

[IanD]

32 minutes ago, peterboat said:

Just think of how much easier and cheaper it would have been with some solar as well

Don't forget that solar 10 years ago was around 3x more expensive than today...

 

Still cheaper than 130kWh of LA and a massive generator/inverter though 😉

Edited May 5, 2022 by IanD

[ditchcrawler]

17 hours ago, PD1964 said:

You all live on fantasy forum land.

Don't most people on here

[Ronaldo47]

Could the traction batterys  have been NiFe cells? 

[PD1964]

4 hours ago, ditchcrawler said:

Don't most people on here

Yes and definitely on the canals 👍👍

[peterboat]

1 hour ago, Ronaldo47 said:

Could the traction batterys  have been NiFe cells? 

Doubt it 

[IanD]

24 minutes ago, peterboat said:

Doubt it 

Especially since they were reportedly "LA full traction batteries"... 😉

[Rishworth_Bridge]

I'm not sure that everyone on here is a fantasist but we certainly have our share. As one of what appears to be only two owners of electric-drive boats on the forum (currently moored on one of the Islington eco-moorings), let me offer a few thoughts.

1. Parallel hybrids, although better than straight diesels, are significantly less efficient than true electric drives because (a) their large diesel engines never work hard enough to get close to the efficiency of small generators and (b) they are restricted to small, diesel-sized propellers because their diesels lack the torque to drive the larger, more efficient propeller that electric-drive boats can have. If their owners lack the insight to switch to electric drive when locking they will also miss out on the third strand of fuel saving that an electric-drive boat enjoys, not ticking over.
2. Actual figures will vary from boat to boat but I think a 30% fuel saving (relative to a modern 2 litre diesel) for a PH vs 50-70% for an electric drive isn't too far out. I can't provide exact figures as I don't have an accurate consumption figure for our generator at the reduced output at which we have to run it but a saving of between 58 and 67% is my best estimate. Moreover, there is at least one electric-drive boat around with a significantly better performance than ours and another due to be shown at Crick.
3. We cruise more than most boats, averaging about 600 miles/annum and I reckon that we save about £250 per annum on fuel (at historical prices) relative to having a modern diesel plus a similar amount on our licence fee.
4. Capital costs for electric-drive depend greatly on how one approaches it. Going to a single supplier for all components will typically cost £40K. Mixing and matching can significantly reduce that. Our system cost £30K (plus installation). Of this, the generator was much the most expensive single item at £12K, with batteries (60 kWh of traction cells) and motor/controller at £7K each and inverter/charger at £5K. We couldn't afford Lithiums even though they would have given a more efficient system. If I were to repeat the build I would buy a suitable industrial generator for about £5K, spend £1K on sound-proofing it and put the saving towards Lithiums.
5. I don't have any figures but believe that the capital cost of a PH installation is similar to a mix and match electric drive.

Changing tack, the discussion about charging has got positively silly. We, with an all-electric boat, not just electric drive, can do 2 days on a full charge without taking the batteries much below 50%. Lithiums would do at least 50% better and improved batteries, to which I drew attention in a previous post, are likely at least to double that again. Ironically, press releases from Toyota and Tesla on just such improvements came out within 48 hours of that post. At 15-20 kWh usage per day recharging a boat with Lithium batteries (so no charging tail) from a 32A socket  should take something like 16-22 hours per week, split however the boater chooses.

 

Finally, the MeterMacs system used on the few public charging points that CRT currently have is contactless, using a website to make payments and switch power on and off. Other than the fact that the names used for the three pieces of information one has to enter to access power are different on the website from the signs on the site, all has worked well.

Edited May 5, 2022 by Rishworth_Bridge

[peterboat]

7 hours ago, Rishworth_Bridge said:

I'm not sure that everyone on here is a fantasist but we certainly have our share. As one of what appears to be only two owners of electric-drive boats on the forum (currently moored on one of the Islington eco-moorings), let me offer a few thoughts.

1. Parallel hybrids, although better than straight diesels, are significantly less efficient than true electric drives because (a) their large diesel engines never work hard enough to get close to the efficiency of small generators and (b) they are restricted to small, diesel-sized propellers because their diesels lack the torque to drive the larger, more efficient propeller that electric-drive boats can have. If their owners lack the insight to switch to electric drive when locking they will also miss out on the third strand of fuel saving that an electric-drive boat enjoys, not ticking over.
2. Actual figures will vary from boat to boat but I think a 30% fuel saving (relative to a modern 2 litre diesel) for a PH vs 50-70% for an electric drive isn't too far out. I can't provide exact figures as I don't have an accurate consumption figure for our generator at the reduced output at which we have to run it but a saving of between 58 and 67% is my best estimate. Moreover, there is at least one electric-drive boat around with a significantly better performance than ours and another due to be shown at Crick.
3. We cruise more than most boats, averaging about 600 miles/annum and I reckon that we save about £250 per annum on fuel (at historical prices) relative to having a modern diesel plus a similar amount on our licence fee.
4. Capital costs for electric-drive depend greatly on how one approaches it. Going to a single supplier for all components will typically cost £40K. Mixing and matching can significantly reduce that. Our system cost £30K (plus installation). Of this, the generator was much the most expensive single item at £12K, with batteries (60 kWh of traction cells) and motor/controller at £7K each and inverter/charger at £5K. We couldn't afford Lithiums even though they would have given a more efficient system. If I were to repeat the build I would buy a suitable industrial generator for about £5K, spend £1K on sound-proofing it and put the saving towards Lithiums.
5. I don't have any figures but believe that the capital cost of a PH installation is similar to a mix and match electric drive.

Changing tack, the discussion about charging has got positively silly. We, with an all-electric boat, not just electric drive, can do 2 days on a full charge without taking the batteries much below 50%. Lithiums would do at least 50% better and improved batteries, to which I drew attention in a previous post, are likely at least to double that again. Ironically, press releases from Toyota and Tesla on just such improvements came out within 48 hours of that post. At 15-20 kWh usage per day recharging a boat with Lithium batteries (so no charging tail) from a 32A socket  should take something like 16-22 hours per week, split however the boater chooses.

 

Finally, the MeterMacs system used on the few public charging points that CRT currently have is contactless, using a website to make payments and switch power on and off. Other than the fact that the names used for the three pieces of information one has to enter to access power are different on the website from the signs on the site, all has worked well.

I know that Ricky has a full electric boat making its way to Crick, I was chatting to the owners at Sheffield, he is ex Army same as myself nice couple they were. I have heard that there will be a number there.

You like myself are really doing electric boating, in my case solar is my main charging method, but I do have a 6kw vetus genny bought secondhand for 1300 squids which was a bargain to say the least. My secondhand LifePo4s were for me a best buy light, powerful and rapid charging definitely a best buy. Are you going to Crick?

[Rishworth_Bridge]

Not going to Crick. Done it 3 times as a show boat and that's quite enough. We'll be somewhere near Aylesbury.

[Rishworth_Bridge]

A further thought about peterboat's comment. I thoroughly applaud the use of a 2nd hand generator. I bought a continuously-rated, 6 kVA, ex-standby unit with just 24 hours on the clock for £1,500 in anticipation of having Ampère built but was talked out of using it by our electrical engineer on the grounds that we needed something more powerful. I didn't discover until it was too late that our 8 kVA F-P has to be downrated to 70% (5.6 kVA) for "continuous running" so we would have charged marginally quicker (and been £12,000 better off) if we had stuck with the original. To be fair, this was his only significant misjudgement and his advice was invaluable in many other respects, leaving us with a boat which hasn't had a single electrical problem in 7 years. The original generator is still in Stockport if anyone wants one.

[IanD]

9 hours ago, Rishworth_Bridge said:

I'm not sure that everyone on here is a fantasist but we certainly have our share. As one of what appears to be only two owners of electric-drive boats on the forum (currently moored on one of the Islington eco-moorings), let me offer a few thoughts.

1. Parallel hybrids, although better than straight diesels, are significantly less efficient than true electric drives because (a) their large diesel engines never work hard enough to get close to the efficiency of small generators and (b) they are restricted to small, diesel-sized propellers because their diesels lack the torque to drive the larger, more efficient propeller that electric-drive boats can have. If their owners lack the insight to switch to electric drive when locking they will also miss out on the third strand of fuel saving that an electric-drive boat enjoys, not ticking over.
2. Actual figures will vary from boat to boat but I think a 30% fuel saving (relative to a modern 2 litre diesel) for a PH vs 50-70% for an electric drive isn't too far out. I can't provide exact figures as I don't have an accurate consumption figure for our generator at the reduced output at which we have to run it but a saving of between 58 and 67% is my best estimate. Moreover, there is at least one electric-drive boat around with a significantly better performance than ours and another due to be shown at Crick.
3. We cruise more than most boats, averaging about 600 miles/annum and I reckon that we save about £250 per annum on fuel (at historical prices) relative to having a modern diesel plus a similar amount on our licence fee.
4. Capital costs for electric-drive depend greatly on how one approaches it. Going to a single supplier for all components will typically cost £40K. Mixing and matching can significantly reduce that. Our system cost £30K (plus installation). Of this, the generator was much the most expensive single item at £12K, with batteries (60 kWh of traction cells) and motor/controller at £7K each and inverter/charger at £5K. We couldn't afford Lithiums even though they would have given a more efficient system. If I were to repeat the build I would buy a suitable industrial generator for about £5K, spend £1K on sound-proofing it and put the saving towards Lithiums.
5. I don't have any figures but believe that the capital cost of a PH installation is similar to a mix and match electric drive.

Changing tack, the discussion about charging has got positively silly. We, with an all-electric boat, not just electric drive, can do 2 days on a full charge without taking the batteries much below 50%. Lithiums would do at least 50% better and improved batteries, to which I drew attention in a previous post, are likely at least to double that again. Ironically, press releases from Toyota and Tesla on just such improvements came out within 48 hours of that post. At 15-20 kWh usage per day recharging a boat with Lithium batteries (so no charging tail) from a 32A socket  should take something like 16-22 hours per week, split however the boater chooses.

 

Finally, the MeterMacs system used on the few public charging points that CRT currently have is contactless, using a website to make payments and switch power on and off. Other than the fact that the names used for the three pieces of information one has to enter to access power are different on the website from the signs on the site, all has worked well.

 

Thanks for bringing some sanity back to the discussion -- most of which agrees almost exactly with what I've been saying (in spite of me not having a boat yet), so I'm glad to know that my fantasist ravings seem to be borne out in real life... 😉

 

The parallel hybrids on the market today (e.g. Hybrid Marine) are less efficient than series hybrids overall because the diesel is too big and the electric motor is too small, and they can't do fast charging (using the motor/generator) when the boat is moored (alternators only with the gearbox in neutral) so efficiency as a generator when moored is terrible -- your fuel consumption figures agree closely with my estimates, which is good news for me when I get my boat (series hybrid) next year 😉

 

I would argue with your comment about propeller size -- parallel hybrids (or diesels) can have a bigger slower propeller if that's what the owner wants (I discussed this with Hybrid Marine) simply by choosing a higher ratio gearbox (e.g. 3:1 instead of 2:1) and a bigger diameter bigger pitch prop, this is no different to an electric boat -- but the hull then needs building with a deeper draft than standard to accommodate this, so this isn't normally done.

 

The cost problem is -- as we've both said -- largely down to the need for a generator, which as you (and Peter) have said can be reduced if you can find a cheap secondhand one. At some point in the distant sunlit uplands future when there's a system-wide charging network this will disappear, but who knows how long this will take... 😞

 

Your generator running-times are (I assume) longer because of LA batteries, and I guess you don't have much (if any) solar? My estimate (LFP, 2kW solar, 9kVA Kohler, 7.5kW charging limited by Quattro) was about 7 hours per week in summer, but that's with solar providing about 50% (7kWh/day) of the required energy -- without this that would be 14 hours/week (almost double in winter with little solar) which again is very close to your figures. I'd probably run it for an hour or so every day (while travelling) because this will also give hot water (generator heats the calorifier with a high-yield "solar" coil), an immersion heater is less efficient but could then only run the generator a couple of times a week -- as you say, it's down to the user to decide when to run it.

 

I'm glad to hear that the charging points are contactless and done via the web, since this is far cheaper and more reliable than an insert-card-reader system 🙂

Edited May 6, 2022 by IanD

[Rishworth_Bridge]

Thanks Ian.

I believe that my comments about propellers are justified. We chose to have a deep draft (30") for aesthetic reasons so had no problem fitting a 20" prop. However, the most efficient current boat of which I know (Firecrest - they have speed/power curves in their blog) is only 24" draft and has a smaller, 4-bladed prop. The new eco-boat to be exhibited at Crick (by Cadal Craft) actually has a parallel hybrid (for reasons to do with taking it to the Continent) with 3:1 reduction. However, reduction gearing doesn't get you away from the fact that diesel torque starts low, increases to a maximum at about 2/3rds maximum revs, and then falls again. I can't be sure but suspect that even with 3:1 reduction a 2 litre diesel wouldn't be able to start our prop. Given that most of the electric motors offered for (inland) boats run at about 1,500 rpm (ours is 1,000), much the same as diesels with 2:1 reduction, they have to be fitted with diesel-sized propellers so don't max out their potential. If I were doing a new installation, I would be tempted to gear down a 1,500 rpm motor by something like 2:1 and then fit the biggest prop I could, bearing in mind that, as well as increasing the number of blades, pitch can be substituted for diameter, albeit with some loss of efficiency.

Given the torque characteristics of diesels I've always wondered why strategies used elsewhere, or in one case previously on boats, aren't used. This case is a bl**dy big flywheel, the inertia of which would help accelerate the prop to the point where the diesel could cope. This was common in diesels of 40+ years ago but has been engineered out as engine speeds have increased. The second is a clutch, used in almost all road vehicles to overcome exactly the same problem; I used to have a motorbike with a centrifugal clutch, something which might work well on a propeller. Finally there is the "mild hybrid" option where an electric motor assists a smaller diesel, much like the modern London buses in which an electric motor gets them rolling before the diesel takes over. All these would permit the use of smaller, less thirsty engines (20 hp instead of 40?), though only the last could assist at maximum revs. And that's before we get onto continuously variable gearboxes!

We don't have any solar at the moment. We had 4x100W of flexibles fitted from new but they failed prematurely (not uncommon with flexibles) and, as the power from them would have cost about double that from our generator even if they had lasted 10 years, we didn't replace them immediately. We are about to have another shot with 2x215W of rigids, having finally found some that will fit in the spaces available on our roof without getting in the way of poles, ropes, etc. Having said that, previous experience suggests that, unless we can improve the gain significantly by angling our panels, we will get only about 10% of a day's usage in mid-summer and very little in mid-winter, about 3-4% overall. That's hardly a game changer. However, solar can work very well for a boat which has room for more solar and/or doesn't cruise as much as we do. Take a look at Firecrest's blog for their experience.

[IanD]

4 minutes ago, Rishworth_Bridge said:

Thanks Ian.

I believe that my comments about propellers are justified. We chose to have a deep draft (30") for aesthetic reasons so had no problem fitting a 20" prop. However, the most efficient current boat of which I know (Firecrest - they have speed/power curves in their blog) is only 24" draft and has a smaller, 4-bladed prop. The new eco-boat to be exhibited at Crick (by Cadal Craft) actually has a parallel hybrid (for reasons to do with taking it to the Continent) with 3:1 reduction. However, reduction gearing doesn't get you away from the fact that diesel torque starts low, increases to a maximum at about 2/3rds maximum revs, and then falls again. I can't be sure but suspect that even with 3:1 reduction a 2 litre diesel wouldn't be able to start our prop. Given that most of the electric motors offered for (inland) boats run at about 1,500 rpm (ours is 1,000), much the same as diesels with 2:1 reduction, they have to be fitted with diesel-sized propellers so don't max out their potential. If I were doing a new installation, I would be tempted to gear down a 1,500 rpm motor by something like 2:1 and then fit the biggest prop I could, bearing in mind that, as well as increasing the number of blades, pitch can be substituted for diameter, albeit with some loss of efficiency.

Given the torque characteristics of diesels I've always wondered why strategies used elsewhere, or in one case previously on boats, aren't used. This case is a bl**dy big flywheel, the inertia of which would help accelerate the prop to the point where the diesel could cope. This was common in diesels of 40+ years ago but has been engineered out as engine speeds have increased. The second is a clutch, used in almost all road vehicles to overcome exactly the same problem; I used to have a motorbike with a centrifugal clutch, something which might work well on a propeller. Finally there is the "mild hybrid" option where an electric motor assists a smaller diesel, much like the modern London buses in which an electric motor gets them rolling before the diesel takes over. All these would permit the use of smaller, less thirsty engines (20 hp instead of 40?), though only the last could assist at maximum revs. And that's before we get onto continuously variable gearboxes!

We don't have any solar at the moment. We had 4x100W of flexibles fitted from new but they failed prematurely (not uncommon with flexibles) and, as the power from them would have cost about double that from our generator even if they had lasted 10 years, we didn't replace them immediately. We are about to have another shot with 2x215W of rigids, having finally found some that will fit in the spaces available on our roof without getting in the way of poles, ropes, etc. Having said that, previous experience suggests that, unless we can improve the gain significantly by angling our panels, we will get only about 10% of a day's usage in mid-summer and very little in mid-winter, about 3-4% overall. That's hardly a game changer. However, solar can work very well for a boat which has room for more solar and/or doesn't cruise as much as we do. Take a look at Firecrest's blog for their experience.

 

Sorry to disagree, but that's not how props work. The torque needed to turn a propeller is zero at zero rpm and rises with the square of rpm, so power rises as the cube of rpm. The "high torque at low rpm" of a diesel matters not one jot, because at low rpm the propeller torque is far lower than that which the engine can produce. For example, if the prop is sized to absorb full power at maximum engine rpm (e.g. 43bhp at 2800rpm for a Beta 43), at 1400rpm it will only absorb about 5bhp (even though the engine could output about 25bhp), and at idle speed (800rpm?) about 1bhp (even though the engine could output about 10bhp).

 

Bigger slower props are more efficient and quieter, but the efficiency difference (maybe 10% - 20% or so?) isn't so big as the difference in noise and vibration. Most direct drive electric motors want to run rather too fast (e.g. 1500rpm), there are ones from some suppliers that run slower than this but they're more expensive. You can probably guess what I'll be using... 😉

[Rishworth_Bridge]

I'm not going to get into a detailed discussion with you, if only because I'm not an engineer so have only a qualitative understanding of the subject, but we have had this discussion within the Sustainable Boating Group (where we have a couple of engineers) and the conclusion seemed to be that it isn't the torque required to turn the prop which matters - you can easily do it by hand at zero revs - but that required to accelerate it instantaneously from 0 to 400 rpm when drive is engaged. I can't remember the acceleration formula but the torque requirement is much greater. An electric motor winds the speed up relatively gently so, as well as probably having more torque available, the demand is not so great.

On the subject of propeller efficiency I offer two comments. Working backwards from our overall performance by removing the 'stopped' and 'diesel efficiency' savings suggests that we benefit by about 30% from our larger prop. That said, while the 'stopped' saving can be calculated quite accurately, the 'diesel efficiency' one is only an educated guess based on generic diesel engine consumption curves so I wouldn't argue too hard. However, as propeller slippage (at 3 mph in open water) seems to vary from less than 40% for Firecrest (about 45% for us) to about 60% for boats with typical diesel installations it is hard to believe that the benefits of larger propellers aren't more than 10-20% unless there are compensating factors elsewhere in the overall efficiency equation. I can see that greater grip might require more power and that might be self-compensating, though I'm having a similar discussion with a retired aero engineer who provided me with an overall efficiency equation which contained the figure 0.5 for propeller grip (1-slippage, I assume). I'm still waiting for an answer to my question about what happens if this is changed to 0.4 or 0.6.

[peterboat]

We used to have a propeller designer on here, he advocated big propellers every time and explained why. Now given that it was his living I sort of believe him, it's a shame and our loss that he has left. 

[peterboat]

1 hour ago, Rishworth_Bridge said:

I'm not going to get into a detailed discussion with you, if only because I'm not an engineer so have only a qualitative understanding of the subject, but we have had this discussion within the Sustainable Boating Group (where we have a couple of engineers) and the conclusion seemed to be that it isn't the torque required to turn the prop which matters - you can easily do it by hand at zero revs - but that required to accelerate it instantaneously from 0 to 400 rpm when drive is engaged. I can't remember the acceleration formula but the torque requirement is much greater. An electric motor winds the speed up relatively gently so, as well as probably having more torque available, the demand is not so great.

On the subject of propeller efficiency I offer two comments. Working backwards from our overall performance by removing the 'stopped' and 'diesel efficiency' savings suggests that we benefit by about 30% from our larger prop. That said, while the 'stopped' saving can be calculated quite accurately, the 'diesel efficiency' one is only an educated guess based on generic diesel engine consumption curves so I wouldn't argue too hard. However, as propeller slippage (at 3 mph in open water) seems to vary from less than 40% for Firecrest (about 45% for us) to about 60% for boats with typical diesel installations it is hard to believe that the benefits of larger propellers aren't more than 10-20% unless there are compensating factors elsewhere in the overall efficiency equation. I can see that greater grip might require more power and that might be self-compensating, though I'm having a similar discussion with a retired aero engineer who provided me with an overall efficiency equation which contained the figure 0.5 for propeller grip (1-slippage, I assume). I'm still waiting for an answer to my question about what happens if this is changed to 0.4 or 0.6.

Because I have a lynch motor I run mine geared Cedric says that his motors run better lightly loaded at speed so I have geared for that. My motor self cools and does run cool to the touch, the only thing I am going to change is the speed controller for a 4QD version as allegedly it's better than my old curtis one, it also allows better monitoring as well