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Old 17-10-2021, 13:39   #631
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Re: Jimmy Cornell goes Electric, with a Cat

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Originally Posted by donradcliffe View Post
If you want more thrust at slow speed, simply reprop your current diesels. As the life of a diesel is 40 years or 10,000 hours, it's going to be a long time before they need replacement. Replacing a working diesel with a motor, battery, and diesel generator makes no sense at all.
I think Big Beakie's source, re the electric being more efficient on the two identical boats, points to there being a real difference. My point is that to protect our motors we have to stop them over revving. So we prop them to get them to max revs at full throttle. We also tend to install overly powerful motors because we need large thrust at very low speeds, when docking, anchoring, steaming into headwinds. So the props on our too large motors are set coarse for us to not over rev when going flat out in a calm, which we never do and hence are inefficient for when we want lots of thrust - low speeds.

If we were airplanes, we set our fixed pitch props for flying level and fast when light and then use them most for taking off when heavy.

Coarse blades are inefficient at low speeds and the power produced will increase rotation of propwash rather than thrust. Hence my point that a smaller electric, with props designed not to go flat out fast, will be more efficient. I get that variable pitch blades would be nice. They are pretty much essential on powerful airplanes that vary airspeed a fair bit, and my mates inefficient variable hydraulic setup pays dividends even with its inefficiencies at low and high speeds.

I understand that changing will be costly but my motors will be up for renewal in the next 5 years or so (my boat is 21 this year). I like the idea of having a large lithium bank charging on the mooring for when I am home and having a small efficient gen set for motoring in a calm, when I am happy motoring at 6 knots or so. Even when cruising, because my cat sails nicely, I very rarely motor for more than 15 minutes if there is wind.

In a local paper today I read of an increase in people converting old classic cars, like Beetles and Datsuns to electric. The garage doing these conversions has seen increasing demand. The costs will probably continue to come down and I am eager to see the costs reduce and the availability of parts and knowledge improve. As a Physics teacher I was able to get a local solar panel installer and electric car racer in to show off his electric conversion De Lorean, complete with faux flux capacitor. He told me that (although he doesn't need gears for the electric) he had eaten up the transmission coupling because of the much greater torque. The kids dared him to do a burn out and they ran to the street and he skidded the tyres for them as he left. All with only a whirring sound. He just loved electric motors in cars, and so I think we may have those car lovers do the heavy lifting for us, just as boat owners did with marinized car engines 100 years ago.

There is great change afoot and I think those of us who are likely to get new engines in the next few years should keep abreast of the changes.
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Old 18-10-2021, 02:45   #632
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Re: Jimmy Cornell goes Electric, with a Cat

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My point is that to protect our motors we have to stop them over revving. So we prop them to get them to max revs at full throttle. We also tend to install overly powerful motors because we need large thrust at very low speeds, when docking, anchoring, steaming into headwinds. So the props on our too large motors are set coarse for us to not over rev when going flat out in a calm, which we never do and hence are inefficient for when we want lots of thrust - low speeds.

If we were airplanes, we set our fixed pitch props for flying level and fast when light and then use them most for taking off when heavy.

Coarse blades are inefficient at low speeds and the power produced will increase rotation of propwash rather than thrust. Hence my point that a smaller electric, with props designed not to go flat out fast, will be more efficient. I get that variable pitch blades would be nice. They are pretty much essential on powerful airplanes that vary airspeed a fair bit, and my mates inefficient variable hydraulic setup pays dividends even with its inefficiencies at low and high speeds.
Your explanation here and in the previous post makes sense to me.
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Old 18-10-2021, 03:45   #633
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Re: Jimmy Cornell goes Electric, with a Cat

I'm new to the party here so just a few requests...
What size was JC's boat? Is that the O45 which was actually 48' btw. I can't find it on his site. And was it a stock hull?



Big Beakie, Can we have some pics of your boat and solar array, please?


And I need to see the 33" prop on the Crowther? I had a Buccaneer also.
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Old 18-10-2021, 03:49   #634
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Re: Jimmy Cornell goes Electric, with a Cat

I probably am a little more invested in this thread than most. It probably comes from the boat I sail.

My cat used about 180 litres for an 8 month cruise last time we headed north, motoring whenever we wanted. She sails very well, especially to windward and we sail her as much as we can. Being a 38ft cat she has heaps of deck space and solar potential. I also have 4 stroke outboards, that don't have the same torque as diesels or electric, and they require more regular replacement. (But the Hi Thrust Yamahas are very good bits of kit, 15 years old and run like new.) (All that being said, she almost used 150 litres of fuel crossing Bass Strait in a calm under power at 7.3-7.5 knots a couple of years ago, pushing her above normal to get to Eden before a nasty headwind)

Which makes her a good candidate for going electric when it is possible. We motor little (apart from Bass Strait and I not going back to Tassie), have great potential solar capability and in calms require little power to motor at a reasonable speed. I also have no engine driven alternators, watermakers or hot water systems. There is a real possibility that we could cruise a whole season and not need to motor any more than 30 miles in a day, which is doable with solar/electric with large panels.

The same cannot be said for many of my cruising peers. Heavier monohulls, with smaller deck area, greater horsepower needs and less high speed distance potential require much more energy storage and have greater power needs.

A swift sailing light cat, could probably go electric/diesel/solar today for many owners but getting the energy into an electric system will be problematic for heavier monos and slower multis that rely more on motors. My friends who tried electric on their heavy steel Ganley tore it out after a year.

The very boats that are the easiest to convert are the ones that use little fuel. So in my case I would not save much on fuel costs as I probably pay $300 for a Barrier reef cruise over half a year. The refit cost can only be justified financially when the motors need replacing. Then again, it is awfully easy to bang on a new set of engines and use them sparingly.
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Old 19-10-2021, 12:55   #635
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Re: Jimmy Cornell goes Electric, with a Cat

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Yes, but what about sailing?
Was not possible, first beating into the wind and tacking with current and wind against, then very light wind, got stuck and decided to motor.
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Old 19-10-2021, 15:29   #636
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Re: Jimmy Cornell goes Electric, with a Cat

Catsketcher's comments on overreving confused me until I realized he is currently running outboards. His plans for an electric plus diesel generator make a lot more sense now.
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Old 19-10-2021, 16:23   #637
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Re: Jimmy Cornell goes Electric, with a Cat

Catsketcher, if you went with the electric drives, would you use saildrives or would you use some form of stern drive that you could pull clear of the water while sailing?
Guess there are advantages to both. The saildrives may give you regen and the stern drives less drag for better sailing.
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Old 19-10-2021, 17:45   #638
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Re: Jimmy Cornell goes Electric, with a Cat

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If I have my main stowed away with its bag zipped up.....it's going to take me a few minutes at a minimum to get it up and get the reef in. It's a big boat with a heavy hydranet main. Do you really think I'm better off letting the boat drag towards the lee shore for 3 minutes more, or have my engines started within 10 seconds?
Well, 3 minutes to raise your sail is a problem with your boat. I can take cover off and raise sail in 10-15 seconds.

But this is the wrong thing to do, if anchor is dragging and there is no sea room you should drop second anchor to stop dragging, then retrieve fouled anchor. At this point you have plenty of time to raise sail, once sail is up, then retrieve second anchor and sail off.

If you try your way, such as "start engine", then it doesn't start: now maybe you lost your boat on rocks. Or maybe a line wraps the propeller or something happens, or the storm is too strong for the engine. I would have dropped second anchor and be safe because it is a more reliable method to handle the situation, and also disproves your argument because neither engine or sail is the right method here.
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I know which I would do. Once that boat is held on the engines, then I can think about raising sails.
You are doing things in back to front order. Engine should never be used and is abomination and scourge of sailing. Electric motor could be allowed but is used only in confined circumstances or in wind speed 3-5 knots and lower.

Electric motors can output several times their continuous rated power. The limitation is thermal overheating of the copper, or potentially the rare earth magnets. neodymium has a relatively low temperature capability. Adding elements such as dysprosium can increase the temperature ability, as well as water cooled electric motor, or even something ridiculous like using silver wire. A 22kw motor can therefore run at many times this power for a duration of few minutes and perhaps 100kw for up to 30 seconds.
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That's pretty good if one 20kw motor can push you into 30 knots. Mind you, 20 kw is a pretty decent size for an electric. If I followed the rule of thumb I'd have 2x10kw on my boat, which is only a little smaller than yours.

I'm thinking the secret sauce here is all in the prop selection. Regarding your props, was it a coincidence that the ideal selection for the diesel and the electric were the same, or did you compromise on one or both to have the same props?
Your calculation for power required is assuming something like a 5-15% overall efficiency rather than 90% efficiency that you should really be aiming for. Take the beam (width) of the vessel and divide by 2. This is the minimum propeller diameter to consider.

For going through waves the efficiency is much less because of the propeller being dragged sideways through the water. Imagine variable pitch where the blades dynamically changed pitch through each rotation to maintain maximum efficiency. You would need to couple this system with gyros to achieve significantly higher thrust efficiency in waves:

https://hackaday.com/2020/06/25/buil...al-swashplate/

The speed of the shaft is modulated within a single revolution and constantly accelerating and decelerating in tune to the waves to achieve a much higher efficiency. You can do this with paddles timing strokes to waves, but a diesel engine can _never_ do this without some kind of elliptical gear box but how would this work at arbitrary frequencies and what additional losses and complexities and weight would it entail? Diesel is an inefficient machine where most of the energy goes to heat, it cannot optimize or adjust to a dynamic environment and will always be sub optimal and should not be in general use. Consider it something of ancient history already obsolete and fools cling to it as a drunk his bottle.

For my boat and 32 inch propeller, it takes 100 watts against 10 knots. Since it takes 4 times the power to go against 20 knots (assuming no waves) This is already 400 watts. By 30 knots (10x the power) this is really 1000 watts needed

This would be the power to essentially hold the boat maybe going 0.25 knots forward, and if I did get turned sideways I would not have enough power to face the wind again. But no where near 20kw or such figures proposed.

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And I need to see the 33" prop on the Crowther? I had a Buccaneer also.
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Old 19-10-2021, 19:24   #639
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Re: Jimmy Cornell goes Electric, with a Cat

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Originally Posted by BigBeakie View Post
JM,

When you come on the boat, how are you going to test the diesel vs the electric? Top speed at WOT, for sure. Compare speeds at same RPM's, that's obvious. Both on at WOT with helm centered, and see if boat goes to port or starboard? ( not sure that would show anything, ie course difference)

I have a few ideas for our sea trial test plan, but am looking for other ideas.

Anyone?

A port/starboard twin engine is an ideal test bed. Top speed is irrelevant -- most diesel boats have enough power to slam hard against hull speed, so top end will be similar.


The real test is rough head conditions. We recently went up the Delaware Bay in 20 kts at 000 apparent, with short period 2-3 foot seas. Our boat is a 22000 pound Saga 43 with a Yanmar 4JH2E. We normally do 6.5 kts at 2500 RPM. We were doing 4-5, occasionally dropping to under 2 (sometimes under 1) with the engine running at 3000 RPM (WOT is about 3200 if I recall). We needed every HP that engine could make.


So, here's the test. Wait for a good nasty day. 20+ knots of wind, short period 2-3 foot seas. Go out, turn dead into it. Run one engine at a time at WOT (or to be nice to the engine, 95%). Run a timed 1NM GPS course (not paddle wheel log -- I have no idea what those seas were doing to that paddle wheel's output!). If one gives you a 3 knot average speed, and one a 3.5 kt (either one), I'd call them "equivalent."


Oh, and for true equivalent, I'd also ask about range. We ran that engine at near WOT for 50 NM -- I'd need the electric to do that too! But that's a different question.
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Old 19-10-2021, 19:53   #640
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Re: Jimmy Cornell goes Electric, with a Cat

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Originally Posted by seandepagnier View Post
The reality is when you break it down the truth is people want to motor against strong winds for hours and hours. This is not something that is any good to do yet it is the only real argument for the diesel and yes batteries ultimately limit the energy storage making this absurd scenario unrealistic on electric power.

If you can't sail upwind in 30 knots there is something wrong with the hull and rig: this has nothing to do with electric power.



Ding ding ding! Sean wins the prize! Exactly. The last 5 days of our 4 month summer cruise were a prime example of how horrible a sailor I am, and how needy I am.


1) Upwind in 20-30 through East River and NY Bay to Sandy Hook. No way beating in East River, but I could have waited a day. Beating across New York Bay would have been no problem for our boat -- but we were pansies and chose to motor the extra 12 miles on the protected channel behind Staten Island.
2) 80 NM in a calm from NYC to Atlantic City. Sure, we could have waited for 2 days for favorable winds. And at 4 knots, we could have motored with an electric in 24 hours. But we didn't want to do either. And with a dog aboard who can't figure out how to pee on the mast, we chose to motor at 7+ for 12 hours.
3) 40 NM in a calm from NYC to Cape May. Again, we could have waited. And that wait with a huge solar array would have done some recharging, too.
4) 50 NM from Cape May to C&D Canal. 20+ on the nose. Sure, we could have sailed, but the DE Bay has vast shoals that are incompatable with our 7' draft, and there would have been a LOT of tacking. And it would have been miserable. And longer than 10 hours.
5) Another long day from C&D down the Chesapeake to Annapolis. Happily, the wind shifted 180 degrees, so we had another long motor directly into 20 knots. Again, we were pansies and should have sailed it. Or waited another day.


Note, "marina recharge" wasn't an option. When we plugged into our home marina, it was our first shore power in 60 days.


So, yes, I want an auxiliary that can push me at hull speed + for hours on end. And then push me dead upwind at some functional speed. And I want it now, without waiting for tomorrow or the next day. I absolutely can sail it instead, and the boat is quite capable of it. But I don't want to.


So, yes, Sean, you have nailed the reason I (one voice) don't see electric as a viable answer.
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Old 19-10-2021, 20:29   #641
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Re: Jimmy Cornell goes Electric, with a Cat

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Ding ding ding! Sean wins the prize! Exactly. The last 5 days of our 4 month summer cruise were a prime example of how horrible a sailor I am, and how needy I am.
1) Upwind in 20-30 through East River and NY Bay to Sandy Hook. No way beating in East River, but I could have waited a day. Beating across New York Bay would have been no problem for our boat -- but we were pansies and chose to motor the extra 12 miles on the protected channel behind Staten Island.
I beat in east river. I tacked in east river. I tacked past roosevelt island in the narrowest part. You said "no way" but I can tell you "way". If 3 boat lengths wide: it is enough to tack.
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2) 80 NM in a calm from NYC to Atlantic City. Sure, we could have waited for 2 days for favorable winds. And at 4 knots, we could have motored with an electric in 24 hours. But we didn't want to do either. And with a dog aboard who can't figure out how to pee on the mast, we chose to motor at 7+ for 12 hours.
?
Quote:
3) 40 NM in a calm from NYC to Cape May. Again, we could have waited. And that wait with a huge solar array would have done some recharging, too.
I sailed sandy hook to cape may in 24 hours. I don't recall waiting for special conditions, and the wind was light. The time you spend at anchor is so long anyway you might as well wait a day or two for wind.
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4) 50 NM from Cape May to C&D Canal. 20+ on the nose. Sure, we could have sailed, but the DE Bay has vast shoals that are incompatable with our 7' draft, and there would have been a LOT of tacking. And it would have been miserable. And longer than 10 hours.
this bay does not have "vast shoals" It is well charted and I recall a lot of cargo ships. I don't think 7ft draft is an issue. It is not exactly the best place to sail, but with a ripping tide, it is not going to take very long. So you spend more time at anchor so what? I recall sleeping while sailing there.
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5) Another long day from C&D down the Chesapeake to Annapolis. Happily, the wind shifted 180 degrees, so we had another long motor directly into 20 knots. Again, we were pansies and should have sailed it. Or waited another day.
I tacked the entire c&d with 15-20 knots on the nose, doing 99 tacks. Was really great experience and lots of people who witnessed cheered me along. Sounds like you didn't learn anything about sailing, when I still learn more each time.
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So, yes, I want an auxiliary that can push me at hull speed + for hours on end. And then push me dead upwind at some functional speed.
25% of the coral reefs are already gone.
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And I want it now, without waiting for tomorrow or the next day. I absolutely can sail it instead, and the boat is quite capable of it. But I don't want to.
So your answer for diesel is "I want"

Well I want a nuclear bomb. Is wanting something good enough of a reason that I should have it?

How does your engine benefit me?

I could take pity if you needed it for survival, but what you are expressing is pure selfishness and benefits no one not even you. You don't learn how to sail: instead you are just wasting your time and quite likely breathing diesel fumes which lowers intelligence making it even less likely you will be capable of anything in the future.
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Old 19-10-2021, 21:10   #642
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Re: Jimmy Cornell goes Electric, with a Cat

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I want a nuclear powered aircraft carrier! No emissions either for propulsion and electricity. Even the steam powered catapults are emission free.


Uh linear motors now
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Old 20-10-2021, 03:39   #643
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Re: Jimmy Cornell goes Electric, with a Cat

I was going to respond to seandepagnier, but it's really not worth it.
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Old 20-10-2021, 03:51   #644
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Re: Jimmy Cornell goes Electric, with a Cat

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I was going to respond to seandepagnier, but it's really not worth it.
Feel the same way. He lost me with propellers half the width of the boat LOL
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Old 20-10-2021, 04:03   #645
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Jimmy Cornell goes Electric, with a Cat

“engines are the abomination of sailing .. and should never be used “

Seriously . Chill out. These days the Diesel engine is probably the most reliable thing on the boat.

The first thing people will do is reach for the starter button

When you have a very suitable “ tool” you use it.

Most “ sailing boats “ are part time mobos these days . That’s the reality , live with it and move on.
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