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Old 01-07-2020, 10:58   #226
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Re: Replace Diesel with electric engine

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Originally Posted by Adelie View Post
The Maramu has a much longer waterline than the Greenline and as a sailboat a shape more optimised for low drag, so it will use significantly less energy per ton to maintain a given speed.

Let's use data from another sailboat to make an estimate.

I used Uma data as a baseline: they use 4.2kW electric to go 5kt. Psychosnail calcs that they would need 8.1kW ICE to go 5.0kt. So about 1.93 times what was measured for electric propulsion.
I used a LWL of 29.2', and a displacement of 15,000lb.

Assuming 41.2' LWL and 40,000lb displacement for the SuperMaramu
Psychosnail calcs 15.9kW ICE to make 5kt.
Using the same ratio as Uma, the Maramu would need 8.2kW. Let's be conservative and say 9.0kW even.

The OP is intending to install a 48kW-hr bank. At 9.0kW usage that would be enough for 5h20m at 5.0kt, that's about 26nm. That's a bit more than half way thru the canal which is 44nm lock to lock. Half way is 22nm which would take 4.4hr using 39.6kW-hr, leaving a bit more than 8kW-hr in reserve.

If there was a 2.2kW Honda putting out 2.0kW then 30.8kW-hr would be used from the batteries to get that far. It would then take about 15hr to fully recharge.

Yes there is distance from anchorage to locks at each end. But the several hours waiting for and sitting in the locks also provides time for the generator to top the batteries back up.

Note none of this involves any solar or wind power. That would just improve the reserve power situation.
While much of the above is true, with my Greenline 33 there's only a 1kt calculated hull speed differential, but a much greater wetted surface with the Amel's canoe body alone, sans drag from the long, low keel. With the 7kW I need for 5kts (2.7kts below my hull spead), with a semi-displament hull optimized for displacement speed rather than top speed of 14kts, no way 2kW more is gonna do it for the Amel. Psychosnail's calcs make a lot more sense.
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Old 01-07-2020, 12:02   #227
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Re: Replace Diesel with electric engine

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Originally Posted by PineyWoodsPete View Post
While much of the above is true, with my Greenline 33 there's only a 1kt calculated hull speed differential, but a much greater wetted surface with the Amel's canoe body alone, sans drag from the long, low keel. With the 7kW I need for 5kts (2.7kts below my hull spead), with a semi-displament hull optimized for displacement speed rather than top speed of 14kts, no way 2kW more is gonna do it for the Amel. Psychosnail's calcs make a lot more sense.

In a previous post you indicated you made max speed (6kt per manufacturer) using 7kW. This post you say 5kt using 7kW. I’m going to assume the first.

The extra energy required from 5kt to 6kt should be close to 50% for a boat that length. Let’s say 33%, to be conservative. So 7kW / 1.33 = 5.26kW at 5kt for the Greenline in flat water no wind.

Yes the Amel has more wetted surface area and more displacement. But it also has a much longer waterline which makes 5kt a lot lower on the drag-speed curve.

The Greenline with a semi-displacement shape really drags a lot of water than a displacement hull like the Amel.

I’m going to stand by my estimate for the Amel power requirements to reach 5kt.
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Old 01-07-2020, 13:04   #228
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Re: Replace Diesel with electric engine

The benefit of getting rid of ALL FUEL is tremendous.

I have never had to look for a fuel dock. I never have oil or fuel smells. Quiet! No vibration! My bilge stays spotless. No heat soak from an engine or generator. Dramatically less maintenance, repair work, spare parts and fluids. As reliable as a TV. MUCH easier to maneuver during anchoring, mooring, and in marinas.

Sure, there are some things I lose, but the gains are substantially more important to me. Every single person who has been sailing on my boat has been amazed by the advantages of going all electric.

I recently purchased my last internal combustion engine (a Ferrari V8).

I sold my powerboat for a reason. Sailing is simply a much nicer experience. An electric motor provides the same infinite range as the sails. Electric is simpatico with sailing.

Diesel is like driving a bus. An awful experience in every way, and stressful due to the fundamental lack of reliability of diesel engines on sailboats. If you don't agree with that last statement, you are in denial. Compare your stress level related to your diesel with that related to your fridge motor. Spare filters, being able to switch quickly between them, watching the vacuum gauge, checking all the oil and fluid levels, belts, alternator brackets, charging devices, cooling system, water flow, etc etc etc. You know it! And all those things are providing stress as you get into a situation (like entering a harbor, anchoring, mooring, rescuing a MOB, etc) where you depend on that undependable infernal combustion device.
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Old 01-07-2020, 14:51   #229
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Re: Replace Diesel with electric engine

I've always always wondered about all those hundreds of broken down diesel semi's sitting at the side of the road, now I know! They're waiting for an Electric heavy lift tow truck. Unfortunately, they haven't been invented yet.
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Old 01-07-2020, 15:31   #230
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Re: Replace Diesel with electric engine

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Originally Posted by Bill Seal View Post
I've always always wondered about all those hundreds of broken down diesel semi's sitting at the side of the road, now I know! They're waiting for an Electric heavy lift tow truck. Unfortunately, they haven't been invented yet.
Don’t worry, Elon’s on the case now and they’ll all be in the shop soon.
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Old 01-07-2020, 17:11   #231
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by Adelie View Post
In a previous post you indicated you made max speed (6kt per manufacturer) using 7kW. This post you say 5kt using 7kW. I’m going to assume the first.
The extra energy required from 5kt to 6kt should be close to 50% for a boat that length. Let’s say 33%, to be conservative. So 7kW / 1.33 = 5.26kW at 5kt for the Greenline in flat water no wind.
Yes the Amel has more wetted surface area and more displacement. But it also has a much longer waterline which makes 5kt a lot lower on the drag-speed curve.
The Greenline with a semi-displacement shape really drags a lot of water than a displacement hull like the Amel.

I’m going to stand by my estimate for the Amel power requirements to reach 5kt.
The paragraph in question:

"On the often very inhospitable wide-open Monterey Bay and the usual summer 15-20 kn prevailing NW winds, 5-7' swell and 2-3' wind waves, I can make little effective way to windward with the full 10kW electric w/ 17" 5-bladed prop and 2:1 reduction gear. It will pull the full 150A only for several minutes before settling to about 130A @ max throttle. The boat specs give a range of 10nm @ 6kn max power, ideal conditions, and 20nm @ 4kts..."

The motor/generator is actually 7kW, and I used the roughly equivalent HP figure mistakenly above - more accurately, 9.3HP. Sorry for the confusion. My max speed has never gotten close to factory's very optimistic 6kts in benign conditions
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Old 01-07-2020, 17:20   #232
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Re: Replace Diesel with electric engine

Again.. a well maintained modern diesel will out perform any electric battery propulsion system for a cruising vessel at this time. Period.
If you want to venture forth with electric or no engine at all we will help you when you get into trouble.
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Old 01-07-2020, 19:58   #233
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by PineyWoodsPete View Post
The paragraph in question:

"On the often very inhospitable wide-open Monterey Bay and the usual summer 15-20 kn prevailing NW winds, 5-7' swell and 2-3' wind waves, I can make little effective way to windward with the full 10kW electric w/ 17" 5-bladed prop and 2:1 reduction gear. It will pull the full 150A only for several minutes before settling to about 130A @ max throttle. The boat specs give a range of 10nm @ 6kn max power, ideal conditions, and 20nm @ 4kts..."

The motor/generator is actually 7kW, and I used the roughly equivalent HP figure mistakenly above - more accurately, 9.3HP. Sorry for the confusion. My max speed has never gotten close to factory's very optimistic 6kts in benign conditions
As a professional skeptic I should have been more dubious of a manufacturer's claims about product performance.
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Old 01-07-2020, 21:13   #234
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by u4ea32 View Post
The benefit of getting rid of ALL FUEL is tremendous.

I have never had to look for a fuel dock. I never have oil or fuel smells. Quiet! No vibration! My bilge stays spotless. No heat soak from an engine or generator. Dramatically less maintenance, repair work, spare parts and fluids. As reliable as a TV. MUCH easier to maneuver during anchoring, mooring, and in marinas.

Sure, there are some things I lose, but the gains are substantially more important to me. Every single person who has been sailing on my boat has been amazed by the advantages of going all electric.

I recently purchased my last internal combustion engine (a Ferrari V8).

I sold my powerboat for a reason. Sailing is simply a much nicer experience. An electric motor provides the same infinite range as the sails. Electric is simpatico with sailing.

Diesel is like driving a bus. An awful experience in every way, and stressful due to the fundamental lack of reliability of diesel engines on sailboats. If you don't agree with that last statement, you are in denial. Compare your stress level related to your diesel with that related to your fridge motor. Spare filters, being able to switch quickly between them, watching the vacuum gauge, checking all the oil and fluid levels, belts, alternator brackets, charging devices, cooling system, water flow, etc etc etc. You know it! And all those things are providing stress as you get into a situation (like entering a harbor, anchoring, mooring, rescuing a MOB, etc) where you depend on that undependable infernal combustion device.
Somehow I must have inherited the lucky gene, as in over 60 years of motor boats and auxiliary sailboats with gas or diesel engines they have proven much more reliable than TV's, computers and fridges. In fact, the only tow ever needed was due to out-drive shaft failure in a 17' I-O runabout. In the three years we spent south-of-the-border, never a failure of our cat's twin diesels with ordinary maintenance and Baha filtering of all fuel.

Sure, we like to impress guests with our current silent 7kW motor/gen. inline with the 165HP diesel, but even with it's 48V 12kWh lithium bank the realistic range is 15nm in flat and windless conditions - which never happen on Monterey Bay. It's nice to diesel out for whale watching at a sedate 8-10kts or so, then switch to electric as we follow them feeding. And nice for leaving/entering harbors, and for the last quiet 5 miles or so back home - usually downwind.

I would be interested in details about your "infinite range" electric motor setup though. That and the '57 Testa Rossa 250 you might have in the barn!
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Old 02-07-2020, 00:49   #235
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by PineyWoodsPete View Post
Somehow I must have inherited the lucky gene, as in over 60 years of motor boats and auxiliary sailboats with gas or diesel engines they have proven much more reliable than TV's, computers and fridges. In fact, the only tow ever needed was due to out-drive shaft failure in a 17' I-O runabout. In the three years we spent south-of-the-border, never a failure of our cat's twin diesels with ordinary maintenance and Baha filtering of all fuel.
I think the key to your luck is hidden within the innocuous phrase "ordinary maintenance" and "Baha filtering"; maintaining a pair of 25 year old Yanmar 2GM20s isn't rocket science, but it's also not "fun" for most non-diesel enthusiasts, just always considered the price one pays to enjoy their sailboat. Certainly it was for us and our FP Athena 38.

u4ea32's long list of "ordinary maintenance" items mirrors exactly our experiences over most of the last 5 years with this boat until this year now that we've replaced both engines with a twin 7.1kW E-Tech POD drive setup using 4 Tesla battery modules for 21.2kWh of total juice. Adding a switch to induction for cooking and a trolling motor/AGM battery for our dinghy has made us completely fossil fuel free.

Early tests put us at 2kW for 4 knots, 5kW for 5.5knots and 8kW for 6.5 knots; 40+ miles, 23 miles, 17 miles respectively. We're still tuning it and likely need bigger props as we're maxing out rpm at only 60% of available power, but it's a great start for a self-designed system which incorporates retractable legs for the POD drives making for drag-free sailing and always clean props.

Regen has topped out at 900W at 9 knots, but still produces 350-400W at 5-7 knots and even dribbles in 150-250W at 4 knots in < 10 knots of breeze. We think one of the motors might not be regen-ing at all, so perhaps these numbers will increase.

If we add a 2.2kW Honda generator as an emergency/supplemental "range extender", we could theoretically cruise at 4 knots indefinitely (fuel allowing), but thus far don't have the need as we're just day sailors for now. I'm hoping that we'll have a non-reciprocating generator option when we do go cruising, but could also just double or triple our electric storage capacity for the same cost as a diesel genset, and we haven't even plugged in our 600W of solar yet...

No one that I've read about that is switching to electric is claiming superiority in all categories over diesel, but many are enjoying a superior experience for how the vast majority of boaters, especially sailors, use their boats; traveling in/out of their local marina to sail for the day or weekend without any "ordinary maintenance" to worry about...
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Old 02-07-2020, 01:08   #236
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by PineyWoodsPete View Post
Somehow I must have inherited the lucky gene, as in over 60 years of motor boats and auxiliary sailboats with gas or diesel engines they have proven much more reliable than TV's, computers and fridges.
I do apologize for appearing to pile onto PineyWoodsPete, especially since I'm fascinated by your new boat and do largely agree with most of your comments, but I did really want to quibble with this line: while there are some truly lousy TVs out there, and computers the world over generally suck, which I blame on software (as a former Apple HW Engineer), the world is full of refrigerators that run over 30 years with.... and this is the key part.... zero maintenance, ever. Most people don't even vacuum the heat exchanger coils on the back every 10 years. And those lousy TVs will mostly operate as well as they did when they were new up until the $0.25 under-spec'd capacitor burns out 5 years later. But the point is, they'll operate that way with zero maintenance. Running a diesel with no oil changes, replacement belts, impellers or filters will kill the engine in a few hundred hours of use. Of course, no one should ever operate something as magnificent as a well engineered diesel thusly, and I maintain my converted 2003 Duramax powered Suburban (22mpg thank you very much) to the best of my ability because I can't afford a Tesla yet... (end rant)
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Old 02-07-2020, 04:34   #237
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Re: Replace Diesel with electric engine

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Originally Posted by yvest View Post

Taken from :
https://www.voiles-aventures.com/new...ie-les-moteurs


Note : This Graph is from a Porsche study comparing diesel of around 55 hp, to electric motors.

And it clearly shows that indeed, at the typical rpm where the diesel are used on boats, around 2000 rpm, the equivalent(in terms of max power) electric motor delivers more power.
And in a performance car where 0 to 60mph times are a popular measure of performance, that low end HP, is very valuable since it means off the line, you have more power, so acceleration is better.

In a cruising boat that goes 0 to 6mph...and typically stays there for hours, that acceleration doesn't mean much.

Also, it's faulty logic to assume the same motor RPM for both propulsion types. It's prop shaft RPM that need to be compared (with identical propellers)
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Old 02-07-2020, 08:19   #238
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Re: Replace Diesel with electric engine

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And in a performance car where 0 to 60mph times are a popular measure of performance, that low end HP, is very valuable since it means off the line, you have more power, so acceleration is better.

In a cruising boat that goes 0 to 6mph...and typically stays there for hours, that acceleration doesn't mean much.

Also, it's faulty logic to assume the same motor RPM for both propulsion types. It's prop shaft RPM that need to be compared (with identical propellers)
The instant power for the electric engine can be very useful for harbour maneuvers.

As to prop shaft RPM vs motor RPM, the point is that the power curves of the engines cross at around 2700 RPM :


So effectively if you choose a 25KW electric (34hp), you end up with something like that :


Meaning that you still get the same power as the diesel at 2400 rpm (and more before), which is the typical Diesel RPM usage.

So clearly and especially for a cat with two engines, going from 55HP diesels to 34HP electric makes perfect sense.

Sure you lose the top power of the Diesel at its max, but you are still better than the Diesel on all the range up to the "typical high end cruising usage of the diesels".
(and on a cat typically a single one is used for long distance motoring, but not at its top power/RPM)
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Old 02-07-2020, 09:17   #239
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Re: Replace Diesel with electric engine

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The instant power for the electric engine can be very useful for harbour maneuvers.
About the only advantage is you can switch from reverse to forward without pausing in neutral as you just reverse the current flow and the mechanical linkage doesn't change.

Otherwise, I don't think I've ever used even 25% throttle in harbor maneuvers. When I do see people gun it, it's usually because they've already lost control and gunning it just makes it worse.

Basically, once you have enough power to maintain hull speed against a decent head wind, you have plenty of power in the harbor.
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Old 02-07-2020, 09:20   #240
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Re: Replace Diesel with electric engine

Maybe I'm color blind or stupid, but it appears that the electric motor magically increases RPM while keeping torque and power constant. ????
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