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Old 04-02-2020, 16:42   #106
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Re: Replace Diesel with electric engine

Thanks for you insights; I understand that cars and boats are different use cases and that the analogy isn't perfect. But I wanted to be clear that even most "cruisers" aren't motoring for extended period at hull speed or 100% output. Most are generally trying to achieve a good compromise between fuel efficiency and speed, hence "cruising speed", and sizing a generator for that speed (should one want to replicate normal diesel engine use) still results in a smaller engine than required in a diesel-only situation. Batteries are there to supply transient spikes of very high power as needed as well as shorter range electric-only operation. Note, most batteries can supply far more power than any practical diesel (provided the motors/controllers are sized appropriately) for short periods providing a transient high power mode that doesn't exist in most diesel applications, one which might create enhanced safety from an emergency "turbo" mode.

I'll reiterate that a series hybrid can be designed to provide 100% the power/speed that is enjoyed by diesel-only, should one want to go that route, and there are huge wins from having that large battery and electric-only operation option. It might cost more (in some circumstances), but nicer/better things typically do, and given the predicted longevity of Tesla batteries (now predicted to exceed 25 years in normal automotive use), the ongoing costs may in fact be lower than diesel-only. And there's a lot of space between full-diesel-emulation mode and totally diesel-free use.

A series hybrid even makes sense in a power boat application, I'd submit, especially for those that appreciate the noise free benefits of getting into and out of anchorages and marinas silently. But in sailboats the advantages multiply given the "auxiliary" nature of the engine in the first place. It may not be economical for most to replace fully functioning diesels, but that doesn't mean it wouldn't make for a more enjoyable product if one did.

I don't know where this idea that electric propulsion isn't green comes from; of course there are concerns in mining any raw material, and lithium is no exception. But as my use case will likely be nearly 100% solar and wind powered, and I'm re-using batteries from a wrecked car, I don't think it gets any greener than that. As Lithium overtakes lead acid so too will its recycling/reuse stream. Even for those charging primarily from the dock, that electricity is far more cleanly created by almost any industrial source than a local diesel generator or worse, engine driven alternator, and as more of the grid migrates to wind/solar, that will become even more true.
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Old 04-02-2020, 16:54   #107
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Re: Replace Diesel with electric engine

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Originally Posted by MichaelPrichard View Post
But I wanted to be clear that even most "cruisers" aren't motoring for extended period at hull speed or 100% output. Most are generally trying to achieve a good compromise between fuel efficiency and speed, hence "cruising speed", and sizing a generator for that speed (should one want to replicate normal diesel engine use) still results in a smaller engine than required in a diesel-only situation. Batteries are there to supply transient spikes of very high power as needed as well as shorter range electric-only operation.
I have avoided getting involved in these discussions, as I am not planning a repower any time soon, but what you have written aligns completely with my thoughts on the subject. I've always been curious why so many here think you will run at 100% capacity for days on end - that just ain't cruising. I look forward to reading more of what you have to say on the subject.
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Old 04-02-2020, 18:15   #108
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Re: Replace Diesel with electric engine

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Originally Posted by GrowleyMonster View Post
On much of the ICW, this can be difficult, especially if you take to heart the part of the rules that say you shall not impede. Wind force and direction doesn't always allow you to sail outside the bouys on a nice easy run or reach. You still need mechanical propulsion at least some of the time. So an EP system should be designed around those demands if ICW cruising or similar is anticipated.
The sculling oar is enough to make sure you do not impede on other vessels. It takes small amount of electric power for this in this case 500 watts for 5 ton boat already enough.

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Please, no. Don't try to use plastic pulleys. And that $23 controller believe me is not up to the task. Ratings are what the mfgr says they are, and are shall we say, a bit optimistic.
First of all, small electric motors are cheaper but can output the same power as larger ones by using higher rpm. The higher rpm also has higher efficiency of the motor which is offset by increased gear reductions so the efficiency is not obvious.

I already know the pulleys can work because they are used in high power 4000W electric mountain bicycles. yes they are 3d printed.

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Y You would want to carry several spares. My recommendation is a nice Kelly pure sine wave controller. Remember
kelly controller is a bad price compared to vesc which can do sine output and cost a small fraction also free software and regen much more flexible.



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You want any reasonable performance level, you want at least 200ah at 48v.
Already have sculling oar which is reasonable performance. 40ah at 12v is equal to hours of sculling.

Am considering making a powered sculling oar to gain the efficiency advantages compared to what is an undersized prop (20% efficient compared to 85%) and the stuffing box friction.


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Regen truly comes into its own when you are regularly and consistently logging 10kts or better.
regen has nothing to do with a specific speed of 10kts or 4kts. It is related to the cube of the speed and the turbine used. If the turbine is large enough or the water is funneled to it, or the turbine is on a wing that sails across the current in figure 8, the power can be huge at low speeds.
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Often you can get a measure of how practical something is by looking at how many people use that particular something.
Then you will miss on practical things that few people are using.
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Sculling oar? I somehow doubt that efficiency claim, but 1/10 HP at 85% is still not very powerful or sustainable for long periods.
it's more like 1/4HP and 85% which is enough to go against 15 knots of wind and maneuver in most harbors and marinas most of the time. It can be sustained for hours at a time.
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Old 04-02-2020, 19:00   #109
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Re: Replace Diesel with electric engine

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Originally Posted by CarinaPDX View Post
Comparing electric/gas cars to electric/diesel boats is problematic. Hybrid cars like the Prius have a great advantage in stop-and-go city driving due to the energy recovery. On the highway their advantage is much less; they are only slightly more efficient than a similar-sized gas car, where the hybrid's smaller engine gets passing power through electric motor augmentation. A boat is an entirely different matter - when under power there is an approximately constant power output. If we are talking about powering for hours the batteries cannot add much to the generator output for supplying the motor. Designing a cruising boat's propulsion for only brief periods of full output is fine for local sailing but not for long range cruising as most cruisers use their boats. If you have a 5kW genset then your motor will have a 5kW sustained output, with battery-augmented operation to the motor's 7.1kW output for a few hours (assuming your control system can stop the genset from charging the batteries when that extra power is needed). If that is enough for your usage pattern then go with it. Assuming you have the extra money to spend. Also, don't fool yourself into thinking this is a green solution - it isn't. From the extra manufacturing energy, the conflict minerals, and the lack of recycling for Li-ion batteries this isn't even close to being green yet, if ever.



Greg


Actually the Prius’ are significantly more efficient than similar cars because the engines use Atkinson cycle rather than the more normal Otto cycle. That produces less power than a comparable size Otto engine but that is made up for with the electric motor.

I’m dubious that most cruisers run their engines flat out when making passages offshore.
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Old 04-02-2020, 19:05   #110
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Re: Replace Diesel with electric engine

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Originally Posted by Ken Fry View Post
I've sailed quite a bit, but I do other things as well, so I am not truly steeped in sailing. Therefore, my perception could be wrong, but at least in the US, everyone I know tacks or gybes according to the apparent wind. If the apparent wind passes over the bow, you are tacking; if it swings over the stern you are gybing.

In an iceboat, you tack even when the true wind is from the stern, provided you are keeping up speed, because the apparent wind crosses the bow. If you are not in that ice boat, you might call it a gybe, but the sailor will call it a tack, because the boat never slows enough to put the apparent wind aft. (And even from the shore, you can see, if your eyesight is good, that the sail goes over as it does in a tack -- i.e., no need to control it.)

I've sailed in rivers where this nomenclature (tacking and gybing being related to the apparent wind) is routinely used. One sails up the Hudson to go from NYC to Albany (and down to go south), but depending on the day, you might be tacking or gybing (or reaching all the way, if the weather gods are with you).

I have sailed in a few channels (but not for days at a time) and have thought that the nomenclature still applies... but it has never come up.

Are you saying that, in your neck of the woods, the direction of water flow in the channel determines the nomenclature, instead of the direction of the apparent wind?
No, I mean that tacking is always done upwind and gybing downwind. When there is a narrow channel, you therefor tack up the channel or gybe down the channel. The words up and down refer to tack and gybe, not to going upriver or downriver. In that context, one would say “sail up river” or “sail down river”. I think we mean the same
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Old 04-02-2020, 19:24   #111
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Re: Replace Diesel with electric engine

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Originally Posted by MichaelPrichard View Post
But I wanted to be clear that even most "cruisers" aren't motoring for extended period at hull speed or 100% output. Most are generally trying to achieve a good compromise between fuel efficiency and speed, hence "cruising speed", and sizing a generator for that speed (should one want to replicate normal diesel engine use) still results in a smaller engine than required in a diesel-only situation. Batteries are there to supply transient spikes of very high power as needed as well as shorter range electric-only operation. Note, most batteries can supply far more power than any practical diesel (provided the motors/controllers are sized appropriately) for short periods providing a transient high power mode that doesn't exist in most diesel applications, one which might create enhanced safety from an emergency "turbo" mode.
Exactly. It’s bewildering to read comments stating the genset must be sized for full power to the electric motor, like if no batteries are available for that full power when it is needed. For a sailboat with auxiliary electric motor, the genset is sized to provide power for motor-sailing when wind alone is not enough for progress.

At the same note, I cannot understand that owners of motorsailers or even motorboats comment that this setup won’t work for them. Duh!
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Old 05-02-2020, 15:07   #112
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Re: Replace Diesel with electric engine

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Originally Posted by CarinaPDX View Post
Comparing electric/gas cars to electric/diesel boats is problematic. Hybrid cars like the Prius have a great advantage in stop-and-go city driving due to the energy recovery. On the highway their advantage is much less; they are only slightly more efficient than a similar-sized gas car, where the hybrid's smaller engine gets passing power through electric motor augmentation.
The first sentence is in some ways true, but might better read: "Comparing electric gas cars to electric diesel boats should be done with care, if you're the person who is going to spend the money."

The second sentence is incorrect. The principal advantage of the Prius in stop-and-go driving might seem to be its regen, but that is the (much) smaller part of the fuel savings. The fact that the engine can operate much nearer to its efficiency peak for a much, much larger portion of its operating time is the main advantage, in city driving. Another is that the engine does not run at all at stop lights, etc., and typically not at all until it can operate at high load.

Your highway analysis also does not square with reality. A Nissan Altima is just a very tiny bit smaller in usable space than the Prius. Both are EPA rated as mid-size. The Prius gets 58 city and 53 highway, the Altima gets (in its most efficient version) 28 city, 39 highway. 53 is a substantially larger number than 39. The substantial advantage for the Prius is, again, that the engine can run at a more efficient setting. Specifically, it is much more highly loaded (in BMEP terms) than the Altima's engine, largely because the engine is smaller and of lower designed output.

In crude terms, the difference is from the well-known effect that an engine runs most efficiently at its torque peak. In a standard engine fitment, large enough to provide adequate acceleration, that means that, at cruise speed, the engine is woefully under-loaded. The Prius engine is also under-loaded at cruise, but nowhere near as dramatically. To bring the Prius load up, power is used to charge the batteries, so the total power consumed at cruise is very close to ideal.

It is easy to find a Ferrari that is of about the same mass as a Prius, and comparable in aerodynamic drag. Even though the Ferrari looks small and streamlined, its drag is actually higher, but not dramatically. A reasonable approximation is that the cars both use the same HP to cruise at 55 mpg. The BMEP of the Ferrari engine (of hundreds of HP) is very very low, and thus efficiency is very very low, perhaps 18%. The Prius BMEP is high and efficiency is high (approaching 38%). The difference in fuel consumption is on the order of 2.5:1: you can expect 20 mpg from the Ferrari and 53 from the Prius.

Without the electric motor, the Prius would be such a dog that people would not buy it. (Although it would still blow the doors off a 60's VW Beetle, then considered a perfectly nice car by millions.) The electric motor fills in when required to provide adequate acceleration.

My Zing is a series hybrid, so in it, the engine runs only at peak efficiency or not at all. There is none of the Prius's occasional part load operation. That same strategy can be applied to boats (and, as I hope you know, has been applied to diesel boats and trains and very large construction equipment for many decades). The Prius was, in its fundamentals, anything but new.

Diesels are not quite as "peaky" as petrol engines are, but they also have a substantial difference in efficiency with load, varying from 0% efficient at idle with the drive disengaged, to mid to high 30's at high load. (Idling with just alternator load? Perhaps 5% efficiency, nearly half of which is lost in the alternator -- unless it is a fancy one, in which case the loss is 25%.) At a mid speed cruise condition, the engine might be 15% efficient, whereas by running it intermittently at high load, efficiency can average perhaps 25%, accounting for the small charging-discharging electric losses. These numbers are in the correct ballpark, but obviously can vary quite a lot -- some marine engines are hideously inefficient, some are remarkably efficient (when compared at their torque peaks). Many smaller ones (300 hp on down) utilize 1950's technology. And in the leisure marine segment, all of them are incredibly filthy in comparison to their road-going equivalents (in the US).

In the book "Polluting for Fun" or something similar... (it's maybe from the eighties or nineties?) the point was made that a jetski of that era polluted as much in one hour as a Volvo car did in a year. That was correct, and most outboards were little better. Diesels were, and are, somewhat better. Things have improved in slow small steps, but if you look up the emission standards for marine engines vs car engines, you will not find encouragement if you are interest in polluting less.

There are thousands of pages of additional details on this stuff available on the web. If you have the time, you might find it interesting to pursue. Also, the Bosch Automotive Handbook is a great resource for clearing up confusion.
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Old 05-02-2020, 15:19   #113
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Re: Replace Diesel with electric engine

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I think we mean the same
Yes, we do. You are quite knowledgeable, and I thought that perhaps there is somewhere (in the Amsterdam canals, for example) where the terms are used differently for a reason that might make surprising sense. Thankfully, that is not the case!

In my experience, if you tack up a narrow lake, then you will also tack down it, because the wind always shifts... but only if you've been itching to put up the spinnaker! At least on Cayuga lake, where I did some sailing, I think the rule was that if the beat up the lake was exhausting, then when you turn around, the wind will both shift 180 and strengthen.... unless you make the appropriate offering to the lake. http://www.cruisersforum.com/forums/...es/redface.gif
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Old 05-02-2020, 15:46   #114
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Re: Replace Diesel with electric engine

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Actually the Prius’ are significantly more efficient than similar cars because the engines use Atkinson cycle rather than the more normal Otto cycle. That produces less power than a comparable size Otto engine but that is made up for with the electric motor.
That is correct, although modern variable timing engines are often 32% efficient, and the Prius is 38%, both figures at peak torque, and that difference does not account for the dramatic Prius advantage over non-hybrids. At fully disengaged idle, both are 0% efficient. Which I mention not to be annoyingly obsessively detail oriented (I am obsessively detail oriented, and have many other bad traits) but because loading the engine to peak torque as much as possible is the fundamental hybridizing goal.

Put another way, a Nissan Altima engine, swapped into a Prius would provide 32/38 x 58 mpg... 48.8. That is significantly more than the 28 or so that the Altima gets in the city.

Having built a plug-in hybrid, (and electric boats, etc.) this stuff has been my thing for quite a while, and I'd like to make sure that the Prius engineers get credit for a phenomenal job, and to also suggest that my experience demonstrates substantial gains through hybridizing, due mainly to the loading factor... having the engine run at peak efficiency or not at all. There are many other small factors involved in the Prius -- it really is beautifully and creatively engineered. I am not simply trying to pick nits.
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Old 05-02-2020, 15:56   #115
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Re: Replace Diesel with electric engine

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Originally Posted by CarinaPDX View Post
Also, don't fool yourself into thinking this is a green solution - it isn't. From the extra manufacturing energy, the conflict minerals, and the lack of recycling for Li-ion batteries this isn't even close to being green yet, if ever.

Greg
I'm from Georgia. Them's fightin' words, Greg. OK, not really... but I am a commie-pinko-tree-hugger-electric-boat-and-car-builder-and-enthusiast and you appear to be quite different from that. But I'm sure we can get along. I will admit, I have guzzled plenty of gas for no good reason other than my own fun -- including flying aerobatics, racing motorcycles, having a couple sailboats in the old days (in fact, all this was in the old days) with petrol auxiliary power, etc.

I have every reason to believe that the OP understands the degree to which his proposed solution is green or otherwise. Not knowing him, I would not want to jump to the conclusion that he is prone to fooling himself, as you seem inclined to do. Did I miss the forum rule that says "Don't be nice." ?

And the only way to suggest the greenness or otherwise of any power situation is to do the math, rather than via generalized wild conjecture. Greer's solar powered boat that did the Great Loop did so on nothing but solar power. You will not convince me or any rational person, I think, that his effort is not "green." Among other things, the boat has very low embodied energy as compared to the floating hotels that many of the forum members claim to own. (It is pretty skinny for a 48 foot boat.) It's propulsion system is cheap as compared to many diesels. It has 20,000 watts of panels, so about $20,000 worth, if he paid full hit retail Home Depot prices. His motors are are a fraction of the price of a diesel engine that this forum might try to convince him he needs. And his fuel costs are zero, whereas a typical 48 foot boat going around the loop can use $10,000 in fuel in just one lap. In three loops, he could amortize his entire propulsion system, leaving him with utterly free and utterly clean propulsion.

He's doing it, in unarguably green fashion, while many on this forum are arguing that it cannot be done. And he is doing on the cheap.

All my electric sailboats have been less expensive than the petrol alternative. I like the lack of noise and vibration and smell, but also I have not wanted to spend the money for a gas engine... because I like to sail, not motor.

Here is a stunning admission: I hike. I am perfectly OK without hotel level accommodations. I have nothing but admiration for folks like the person participating here who sails without an engine. I have happily called power boats "stink boats" for years.

Also criminally shocking: I have cruised on both a Hobie 33 and a J24 (on the J24, we had one if not both our kids). Is that laughable, or what?? The J24 carried its racing-rules-required engine, always stowed. The Hobie had electric motoring in the form of a trolling motor -- worked well, and was much lighter than the engine I removed, including the weight of its small LA battery. (However, I should not really include the battery weight, because it was the same "house" battery the boat came with. Rationally put, based on real experience: the boat lost 80 lb by ditching the 9.9, it used the same old battery that was already there, and then gained back 15 lb for the trolling motor. Net weight loss: 65 lb. It would sail faster (unmeasurably, of course -- although 65 lb is about 1/3 a standard person -- and the Hobie was wonderfully sensitive to weight).

Additional bonuses, in addition to reduced weight and dramatically reduced cost (9.9 vs trolling motor): it didn't stink so much, it was less of a fire hazard, it was quieter... all while serving my aux power needs amply. There were two solar panels on the rear deck (the engine cover) something of an oddity for a Hobie, (especially 30 years ago) but it had been prepped for some long distance races in which ample power for electronics was comforting.

Incoherent rambling from here on out:

My current project breaks that mold (of using only electric power) in a way that will make you all happy: in addition to its wing, and its electric motors, it has a 30 hp outboard, which will propel it at just under 20 knots on its skinny little hulls. In an ultralight, weight is a driver of performance, and a 30 hp motor and 100 mile range is hard to achieve in an electric alternative of comparable weight. (A Tesla battery pack is not a light thing.) I could compromise the design weight, but compromise sailing performance. Many would ask: Why on earth do you want 30 hp on a boat the is 2500 lbs empty? Its' fun to go fast sometimes when the wind dies. Once in a great while it will be comforting when racing into a harbor to avoid approaching fog, a twister, etc. (I've sailed in places where both are valid concerns... but really, the boat would do fine without its petrol engine. ) and in the Panama canal, plenty of power is comforting.

(Actually, my current project was designed for a particular mission, that I will no longer use it for, in which I wanted to be able to do an hour a day at 18 knots, under power, as required. Instead, I could use one of my electric motors that weighs 22 lbs and consumes 15kW safely for about a minute at a time, and it could run all day at lower power. Hmmm. The Suzuki 30 hp motor is $5000. The tank is installed but removable, and the space is large enough to hold $3000 worth of batteries, which would serve my current needs: I like having quite a lot of power available in marinas, or if I screw up my navigation, or drag anchor. I have sailed into marinas many times in boats without engines, but it can be comforting to have plenty of power to compensate for my occasional bad seamanship, which I think will only get worse if I am lucky enough to further age. So maybe it is silly to carry around a gas guzzler, when electric would work better and be quite a bit lighter.

Thanks for working through that with me... http://www.cruisersforum.com/forums/...ilies/wink.gif)

Peace be with you all. It's crazy late here. Sorry for the long post. If I had more time I could make it much shorter.
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Old 06-02-2020, 02:07   #116
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Re: Replace Diesel with electric engine

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Originally Posted by s/v Jedi View Post
I have sailed all my life and the first 10 years just in open dinghies with sails only. We could get everywhere, even upwind on a 20’ wide channel. Those were the days you really learn how to sail, how to manoeuvre etc. Those who experienced that have a completely different view on what is safe to do under sail than sailors who start at later age and skipped the dinghies.


Yup. Been sailing all my life, starting in dinghies too.

So eventually it just came naturally to sail a 50 footer on and off the anchor when down island in 2 handed cruising mode. If anything it's actually somewhat easier with a bigger heavier boat.

Stepping it up a level, after some engine problems, how about sailing on and off the dock at Block Island and then in and out through the narrowish channel to Great Salt Pond?

Did this day after day during race week. Even the other racing boats and crews thought we were crazy, which is odd given the boat handling maneuvers that are done normally when racing...

But unfortunately many people here on the forum just don't have that level of sailing experience or confidence with their boat.

In a more cruising context, our engine quit once when exiting south through the reefs from Tobago Keys. We were still in lazy cruise mode, awning up, beer in hand. But as always, some sails were still ready to go, sheets led, etc, and in less than 60 seconds the genoa was unfurled and we were back under way, under sail. In amongst the reefs we didn't even think to lose time checking why the engine stopped.

That situation could have easily ended in disaster but instead was just taken in stride, as not such a big deal.

So regardless of your propulsion system, always be prepared and ready to sail. It just might save you and boat one day.

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Old 06-02-2020, 09:52   #117
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Re: Replace Diesel with electric engine

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Originally Posted by stormalong View Post
Maybe there are so many negative responses because this idea is not viable (yet). Perhaps someday in the future it will be but not today.

We had an expression in the IT industry: Coon skin caps attract arrows.

If this system was viable there would be product offering from bigger players. The negative comments are appropriate.
You can probably understand that "your truth" might not be "the truth'. You have a perspective that appears to ignore physics and history, but that's OK.

General Dynamics, a company well known by many people around the world, started as Electric Boat Company in 1899.

Duffy started in 1970, and has been happily and quietly selling electric boats since then.

Perhaps you don't believe either of the previous 2 sentences, but you can probably understand that the OP will, given his much different perspective.

I note your location. Do you keep your boat in the Langley harbor? I vaguely think I might have seen a Nordic there. I had a place on Hat Island for a while, and it was the travel back and forth to Everett that caused me to design my hybrid rigid wing/electric sailboat. I was travelling back and forth very often, in all sorts of weather, and not exactly for leisure (although the whole exploit on Hat Island falls under the category "Leisure"... I didn't have a "job" out there, but had plenty of work to do every day.)

For my needs, having a boat that could be sailed fast much of the time, but also motored fast (18 knots or so) drove the decision to ditch the MacGregor and its 60 HP gas guzzler, and go with the reliability, freedom from stench, and quiet of electric power. The failing of the Mac, aside from its awful yet useful engine, (which occasionally would not start... and when running would spew as many emissions in an hour as a Volvo does in a year), was that it could not be sailed fast. In addition, I wanted to have "sail on its lines" unsinkability -- which is quite useful (potentially) and comforting. The MacGregor's positive flotation (particulary in cold water) is comparatively useless, because after holing, it leaves the boat still visible above the water, but not able to move under its own power. The skipper, swimming in the cockpit, would have perhaps eight minutes before hypothermia would cause his or her demise if the water is 53 degrees. The heirs might appreciate that the boat can be salvaged more easily than if it sunk... but then taking the insurance money for a sunk boat is certainly easier.

I've sailed in quite a few different areas, but it was not until sailing from Hat Island that I started to feel that I could hit something big, anytime. (In fact, hitting something big (gently and with intentional care) was nearly standard operating practice some days, just to be able to get in and out of the harbor.

It is probably best to try and keep Langley secret, but it has got to be one of the country's most charming towns!

Poke around your area. On the mainland you will find a company named Boeing, which many others consider a "bigger player." They like the idea of electric power in boats.
https://www.boeing.com/defense/auton...ger/index.page

BTW, you may know that there is a guy on Hat Island who used to commute back and forth every day to take his kids to school, on his traditional cotton-stuffed-planked-swelled-up wooden sailboat. He can calmly tell stories about how, after a haulout and getting the boat back into use, he found a few hundred gallons of water in the bilge about halfway between Hat and Everett. But he is here to tell the story.
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Old 06-02-2020, 13:19   #118
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Re: Replace Diesel with electric engine

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You can probably understand that "your truth" might not be "the truth'. You have a perspective that appears to ignore physics and history, but that's OK.

General Dynamics, a company well known by many people around the world, started as Electric Boat Company in 1899.

Duffy started in 1970, and has been happily and quietly selling electric boats since then.

Perhaps you don't believe either of the previous 2 sentences, but you can probably understand that the OP will, given his much different perspective.
Don't know about "truth" but numbers don't lie. Here's what I've determined from doing the numbers over and over. Lest my motives be suspect let me preface my remarks with a couple of comments. First, I am an electrical engineer by training. Second, for a number of reasons that I won't bore you with, I would really, really like to go electric.

Yes electric is viable. It is possible to replace a standard, diesel engine with an electric system that has the same power and range. However to do so will require installing a more complex and much more expensive electric system than the diesel you would replace. A big part of the extra cost and complexity is installing a generator to give the range under power.

Without a doubt a generator is more expensive than a plain diesel engine and certainly more complex and in my experience is less reliable over the long run.

Jedi is quite correct that one would not need to install a generator with the same max output as the diesel engine one would replace but, depending on the cruising style, circumstances, area, etc one would have to install a battery bank to supply the higher power needed for short term high power draw in situations like close quarters maneuvering, emergencies, etc.

So bottom line, again yes it's viable but based on my calculations, if you buy a commercially available "marine" system you will end up spending double or triple the cost of brand new diesel engine. If you know of a system that is cheaper would be very interested in seeing the information.
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Old 06-02-2020, 13:31   #119
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Re: Replace Diesel with electric engine

This is one of the bookmarks I have on converting from diesel to electric: https://www.electricmotorsport.com/p...ve-system.html
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Old 06-02-2020, 18:52   #120
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Re: Replace Diesel with electric engine

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In the book "Polluting for Fun" or something similar... (it's maybe from the eighties or nineties?) the point was made that a jetski of that era polluted as much in one hour as a Volvo car did in a year. That was correct, and most outboards were little better. Diesels were, and are, somewhat better. Things have improved in slow small steps, but if you look up the emission standards for marine engines vs car engines, you will not find encouragement if you are interest in polluting less.
It was actually "Polluting for Pleasure", (Andre) 1993.

A summary from the back cover:

"In the tradition of Silent Spring and Unsafe at Any Speed comes this frightening, landmark environmental study. The message: seemingly innocuous recreational boats, particularly outboards, are polluting as much as all the cars and trucks in America; and the marine industry has been holding its breath, hoping that nobody notices. Polluting for Pleasure begins with the author accidentally discovering that pleasure boats have been spilling oil into the environment on a magnitude that is staggering. In addition to being 80 times more polluting than automobile engines, the more than 8 million two-cycle outboard engines put more oil into American waters than 15 Exxon Valdez oil spills, annually! Oil, like dirt collecting on the sides of a bathtub, contaminates the shores and marshlands of our lakes and rivers, the cradles of all marine life. This important new book not only studies the problem of pollution from powerboats and the environmental effects, it also offers constructive suggestions for alleviating the problem."
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