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Old 27-07-2011, 06:47   #151
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Re: Electric Propulsion

[QUOTE=Dick Pluta;738543]
Quote:
Originally Posted by daddle View Post
Agreed. So you just shot yourself in the foot? Your equation proves that one diesel HP is equal to one electric motor HP. Thanks.
QUOTE]

EXACTLY!!! 1 HP is 1 HP no matter where it comes from!!!

It is torque alone that matters. Your propellor dosn't understand HP. It only knows how hard you are trying to twist it.

The problem is that horsepower is a misleading rating. A toy motor puts out about 1/2 ft.lb. If you ran it at a million RPM it would put out an astonishing 32000 HP. At 1000 RPM it has nothing. Similarly, my diesel puts out 100HP at 2000 RPM. At idle it has just enough to keep itself running. If I apply a greater load, it simply stalls. Why? Because it does not produce its maximum torque until 2000 RPM.

I tried to make a little chart that illustrates this. I think I have attached it. It's a JPEG. It shows that the diesel makes very little torque at idle, while the electric can produce maximum torque immediately. The demand line shows that the diesel doesn't produce enough torque to drive the load until about half throttle. The electric has it immediately. The only reason a diesel has to be "bigger" is to shift the torque curve upward so that you can get more "horsepower" at a lower RPM. If you need 100 HP at 1000 RPM it does no good to have it at 2000 RPM.

It's a tough thing to understand. Even trained engineers don't always get it. Try this. You're trying to remove a screw. You apply a little torque to the screwdriver. Nothing happens. You apply a little more and then even more. Finally you overcome the resistance of the screw and it turns. There's horsepower in there somewhere but it doesn't really matter. It's all about TORQUE!

As a prime mover, electric is great. The problem is not the motor. It's getting the electricity to drive it.
Dick:

Very interesting and understandable explaination on the difference of diesel vs. electric when it comes to torque. Thanks! I think it also explains one of the real nice atributes I've found with my electric system. Namely, I can now "approach the dock at the speed I wish to hit it". Since I have found I have much more control over speed at the low end of moving. Yes, I agree the electrical storage is a limitation. But, it is one I can easily compensate for. Another thing as technology advances in that area (and I am pretty sure it will) I can upgrade to them as they come along. For example you can now have a choice of flooded, AGM or Lithium Ion batteries for EP systems. I went with AGM because for me I thought they were the best choice considering storage, charging, cost and maintanence needs. After four years of operation I'm happy with that choice. But, I also keep my eyes open on new battery technologies too for the future improvments which can be easily made with an EP system. In the meantime I make up for the limitations of electrical storage by augmenting it with elements like the Honda 2000 generator to extend the range and provide rapid charging when at anchor. But, to me this is no different than many cruising boats that already have a diesel propulsion system but, also have an additional diesel generator on board too. Though having something like the Honda 2000 has a lot of other uses on board for me. I not only use it to extend the range of my EP system beyond it's twenty mile spec range. I also use the generator to charge the 12 volt house bank on occassion when 90+ F degree temperatures make the freezer work a little overtime and the solar panels can not keep up, using the 2 gallon wet/dry vac to quickly drain/clean the bilge or clean up after projects. I also use it to power my hookah dive compressor system so I can clean the bottom of the boat. Though what I'm really waiting for is for solar panel technology built into the sails.
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Old 27-07-2011, 06:50   #152
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Re: Electric Propulsion

[QUOTE=Adamante;738578]I am not sure I would agree with that generalization. [QUOTE]

Well, we all know that generalizations are only generally true.


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Maybe it depends on one's individual cruising style, but I note that many cruisers will often motor when faced with adverse winds and sea state, in addition to motoring in calms.
Well yes exactly. I thought I said that is one of my points.

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Anyway, I think we are doing a pretty good job of beating this one to death. (now where is that dead horse icon...)
I found it. It was hiding right over here.

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Old 27-07-2011, 07:42   #153
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Re: Electric Propulsion

Well I must admit this thread is much better then the majority of discussions on EP in the past. At least no one has said We are a bunch of screw balls wasting our money.
Best statement awards to:
"Based on how I use it", "the systems are upgradeable", and "The technology is improving rapidly".

This however is why I'm posting.
"Ask Lagoon why all of their hybrid owners are repowering with Yanmars. Electric propulsion is nice on a daysailer, but not on a cruising boat."

This is also specific to the 420 not the 410. A little history first.
Lagoon entered into contract with Solomons Technologies to develop a hybrid Cat back in 2002 for 3 410 cats. Of the 3 cats all 3 are still EP's. One is on the Cape of Mass. after a young couple with 2 kids spent last summer traveling up from Florida mostly on the IWC under Genset. They had a few problems with a controller but since there is redundancy (4 Controllers, 2 per motor) they were able to continue at 50% motor speed on the one side. They had issues with the New genset (proper cooling) but have since corrected the problems. This boat is 8 years old.
The second one is owned by a guy down in New Orleans and is now (last I heard) somewhere in South America cruising. This was actually the first boat built with this system, also a 2003, and you can read the story of it's travels from France on it's maiden voyage at:
First Electric Lagoon Crosses Atlantic to Annapolis...Then Heads to Tortola
The 3rd boat owned by Cindy and I is located at Solomons MD. Built in 2004 and the last of the 410's built with the Solomons system I'm quite pleased with the performance and dependability of EG.
As for the 420's the system was totally different than the 410's. Dave Tether who was one of the original owners of Solomons went through a number of personal "issues" with the company and left to form a new company Emotions. Lagoon decided rather than going through anyone else they would develop their own system which among other things was sold before all the bugs were out of the system as well to, what I consider, under trained owners in how to properly operate the system. In most cases the system would produce but not in all cases such as buying an EP boat and putting it in charter with a bunch of idiots that may not even know how to sail yet operate a sophisticated system. Don't forget at the time this was pretty new to everyone let alone a renter. For that matter most owners were expecting a "plug and Play" system that Lagoon promoted as such. Anyone who owns a EP system knows that this isn't the case and soon owners were burning up the batteries at an alarming rate as well as having problems with the auto-start generators. Early on a number of systems were converted back to diesel and I have no idea how many but I know not "ALL" were converted over. Since then Lagoon has not ventured back to EP. Dave Tether has continued to develop his system on a 500 Lagoon and there were several other Lagoons converted with his systems. He also has several other boat manufactures developing EP systems including the TANG boat. From what I understand it's problems lie in the complexity of the boat not in the drive system. Dave is also working with Calder and both of them were down on my boat a few years ago to look at the modifications that were made on EG.
Battery technology (the weakest point of the system) is moving along, I'm hoping for the Lithiums at some point will be affordable. The new controllers under development are digital, and will replace 1 for 2 and be much more durable. The motors are good for 150,000 hours and operate on board for less than 50% of their rated output at maximum speed. I've operated at 35kts of wind on the nose with severely short period seas of 6 to 8 feet and maintained 4 knots.
Would I attempt to enter a rage down in the Abacos? NO WAY but then would you? The point is if I know I'm going to get into something nasty I make sure the batteries are fully charged, with the genset if necessary and damn the fuel usage, continue to run the genset until I feel safe the danger has passed and then put the sails right for the conditions and go on my marry way regenerating through the props.
If any of you have read my other posts you know that we where new to sailing 3 years ago with a new to us boat and a new to just about everyone Hybrid system. I have made it a point to learn as much as I can about our system even to the point of developing wiring diagrams that Lagoon doesn't provide anyone. I've developed and upgraded the EMS (energy management system) to give me a better understanding of the state of charge and condition of the batteries to extend the life of them to hopefully the point the LiPo's are affordable. Other than that...
THE SYSTEM WORKS FOR THE WAY WE USE THE BOAT.

Steve in Solomons MD
Lagoon 410 SE
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Old 27-07-2011, 07:54   #154
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Re: Electric Propulsion

Hi Steve,

Thanks for the detailed report on your Lagoon. Very informative and nice to hear something based on real world useage.

Can you give us the specs or power ratings on your EP version vs the diesel powered boats or point us to a link with the specs?


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Old 27-07-2011, 08:08   #155
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Re: Electric Propulsion

Hallo Steve , can you tell me something about the regenerating capability's of your system
and the type and size of props on your Lagoon 410
I understand you have the 9 Kw motors as supplied by Solomon Technologies .

Gideon
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Old 27-07-2011, 08:13   #156
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Re: Electric Propulsion

Quote:
Originally Posted by Hyprdrv View Post
This was actually the first boat built with this system, also a 2003, and you can read the story of it's travels from France on it's maiden voyage at:
First Electric Lagoon Crosses Atlantic to Annapolis...Then Heads to Tortola

Steve in Solomons MD
Lagoon 410 SE
While keeping up with this thread, I keep thinking of this guy with the Lagoon 410, Waypoint. There's a couple videos on Youtube. He seems to love having an electric system and promotes it quite well.

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Old 27-07-2011, 08:49   #157
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Re: Electric Propulsion

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Originally Posted by fastcat435 View Post
Hallo Steve , can you tell me something about the regenerating capability's of your system
and the type and size of props on your Lagoon 410
I understand you have the 9 Kw motors as supplied by Solomon Technologies .

Gideon
I was wondering about props too, and was surprised no one has mentioned them yet. I would presume that electric would use a little "larger" prop (in diameter or pitch or both) than diesel, gaining a little propusive efficiency. Can any of the electric operators confirm or comment on this?

edit - Well, higher pitch would probably not increase efficiency. The point is that there is most likely a different propeller match.
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Old 27-07-2011, 09:48   #158
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Re: Electric Propulsion

Quote:
Originally Posted by Lee Jerry View Post
I was wondering about props too, and was surprised no one has mentioned them yet. I would presume that electric would use a little "larger" prop (in diameter or pitch or both) than diesel, gaining a little propusive efficiency. Can any of the electric operators confirm or comment on this?

I am using the same smallish two-blade prop that I had with the diesel. It was inefficient before and it is inefficient now, but minimizing drag while sailing is more important to me than a more efficient motoring. Control in reverse has improved significantly. With a bottom in need of repainting (slime and quite a few barnacles) I regularly get 3.6+ knots in calm conditions using only 10 Amps. I have not tried regeneration yet. So far, I do not see the need for a different prop.

A few comments... ours is the first (and only) electric boat at the marina. It is quite an attraction; I have people asking to see the installation all the time. They are always amazed at the simplicity of the system. The most frequent comments are in the line of "I should install something like this in my boat" and “I wish I could have electric”. Every single person that has sailed with us has been impressed. Some friends have said that if they ever buy a boat, it will be electric. Based on my un-scientific survey, I can say that 100% of the people who have seen our system would consider electric for their boats. Leaving aside the problems with the Lagoons, which have been meticulously explained by Hyprdrv, I have yet to see someone with electric considering going back to ICE (and I would guess that most of those Lagoon owners that went back to diesel did so because they were burnt buy a bad product).


Although electric is quite versatile, if I had to regularly motor against strong winds and currents in choppy seas and for long periods of time, I would have kept the diesel and waited for a breakthrough in battery technology. If I did not have access to shore power, and not being willing to add wind and solar chargers, I would have kept the diesel. IMHO, it is not only “is electric suitable for me”. In seeing how the immense majority of the sailboats in the area I sail are being used, I think that the questions are “is electric suitable for me?” AND “would I switch?” I think that for a large number of people the answer to the first one is yes.


Alberto
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Old 27-07-2011, 10:25   #159
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Re: Electric Propulsion

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#1 above is incorrect. The rating for diesels from all reputable manufacturers is 'shaft horsepower. That is the power you can extract from the engine. The prop will see maybe 5% less due to losses in the transmission. All the other losses in the engine are accounted for in that calculation. Of course the alternator takes some power if charging, but that should be ignored for this comparison as the electrical loads of the boat subtract from the electric driven case as well.
Recreational engines are generally rated for maximum intermittent brake power (power available at the cranshaft or flywheel) at max rpm - everyone wants to boast of the most power. This rating will account for all standard parasitic loads, including the alternator. If however, your engine has a second or high output alternator, that would not be included and would have to be corrected for comparisons. Max continuous power will be at some lower engine speed, typically anywhere from 100-500 rpm less. Shaft power is the power available at the prop shaft (after the gearbox, bearings, etc.); 5% gear losses would be a little on the high side for only a gear.

For example, take this Yanmar engine advertised at 39.6 kW. From the datasheet: max brake is 39.6 kW, continuous brake is 36.0 kW and max shaft is 37.5-38 kW (from graph). These include the standard 80A alternator, but a second alt is an option.

Quote:
#2 is incorrect. There are no other inefficiencies. The particular property of propellers is that they cannot use that extra torque at low speeds. Huge torque at low speed is useless to the typical cruising boat. You'd need a variable pitch prop, like on a tugboat, or Dashew's boat, to make any use of it.
Prop torque is generally highest at low forward speed and decreases as forward speed increases. Picture the inflow (resistance to turning) hitting the blades from 'abeam' at zero speed and aligning more with the blades as forward speed increases.

Quote:
It's interesting that I asked for proof of this claimed 250% disparity between "diesel hp" and "electric hp" and have received none at all. Interesting but not surprising. Consider my small boat. She has nominal 20hp/15kW Beta diesel. At around 1200rpm at the prop she has about 100Nm of torque. Not surprisingly the Thoosa 12000 (12kW) datasheet claims about the same: 1270rpm and 90Nm. Do you think the prop can tell the difference? Does it taste different of something?
I don't think it is that hard to see where it comes from. As previously mentioned by others, it mostly comes from the difference in ratings for diesel (max) versus electric (continuous) for typical operating (cruise) speeds.

Look at the Yanmar above. A typical cruise speed might be 3/4 throttle. From the power graph of the prop curve, that gives about 24 kW at 2600 rpm. Take out 4% gear loss (1 kW) and the second alternator (1 kW) and you're down to 22 kW - almost half the diesel 'rating'. Perhaps accept a small decrease in performance (due to 'fuel' supply limitations) and your 2.5 factor is clearly in sight. Max speed for the electric will still be close to the diesel by the ability to exceed the rmotor ating.

Another factor not previously mentioned (that I recall) is the different conditions for reporting the ratings. ISO conditions for the diesel are pretty mild - 77 F and 30% humidity. Typical marine operation will be at higher temperature and humidity, both ambient (for 'typical' fair weather cruisers) and certainly in the confines of an engine room. Therefore, the diesel will often produce much less power than rated. Conversely, electric motors are typically rated at 104 F and don't suffer at high temp (until failure). Batteries perform better at high temp too.
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Old 27-07-2011, 10:39   #160
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Re: Electric Propulsion

Skip,
Here are some specs on the electric motors.
http://www.solomontechnologies.com/p...T74_specs1.pdf
I don't recall ever seeing a comparison of the EP verses the Diesel.

I forgot to mention another problem with the 420 was the hull design. It seems that Lagoon changed the design for the placement of the batteries rather than speed so the boat suffered from a performance standpoint (I've been told) as well right out of the box.

Gideon,
Regen is ok where we sail mostly, in the Bay. For regen to really come alive you got to be in the bigger stuff, at higher speeds, say above 20kts of wind and boat speeds in the double figures. I still see 2 amps at 10kts SAILING and that's enough for day cruising. Off the dock under power, sail all day, and back on the dock I'm pritty close to equal, as long as there is some wind. That's another thing that gets me. Once out of the creek we put up the sail. I see tons of boats still under power to get some place. As an EP boater you maximize the sailing not the power boating. MAybe it's just me...

Dan,
Yes that boat is Waypoint, the same one that the previous posting showed the performance from France. Bruce should be somewhere down south of the boarder by know.

Lee,
The props are 18" produced by WildCat in 2007. An upgrade from the originals.

Alberto,
I couldn't have said it better.
Anyone who has sailed with me is Way impressed with the system. I remember being out and just dropped the sails coming in. A 40+ mono was on my tail and yells over "Are you electric?" I answer Yes and ask how can you tell? He says "you can here me can't you?" with a smile? I was grinning from ear to ear. I don't think the name "Electra Glide" hurt either.
Also the bigger systems are expensive right know. I would guess that if I was to go out and buy my system today it would be in the $30k range. Even a fresh battery pack of AGM's is around $6k but their good for at least 6 years. At least mine are, 12 Northstar batteries at 210AH each in series for 144v and way a 140lbs each, yes that's a lot of weight but the LiPo are 1/3rd the weight at 3 times the cost but coming down, I'll say smoothly.)

Short term plans are Massachusetts (grandchild) and South Carolina (Golf).
Long term plans/goal, the Caribbean.

At this time we enjoy the weekends in Solomons with a great bunch of Dock Buddies sailing the Bay and having a ball.
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Old 27-07-2011, 11:01   #161
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Re: Electric Propulsion

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At this time we enjoy the weekends in Solomons with a great bunch of Dock Buddies sailing the Bay and having a ball.
Then I'll be looking for Electra Glide, and you look for Bonheur (Dufour 34, red hull). We sail in the Northern Chesapeake bay...
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Old 27-07-2011, 12:31   #162
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Re: Electric Propulsion

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Look at the Yanmar above. A typical cruise speed might be 3/4 throttle. From the power graph of the prop curve, that gives about 24 kW at 2600 rpm. Take out 4% gear loss (1 kW) and the second alternator (1 kW) and you're down to 22 kW - almost half the diesel 'rating'.
I think the prop curve is the prop power requirements. In that case it takes 24kW to turn the prop at 2600 rpm. The engine is capable of around 35-36 kW at those rpms, but since the prop doesn't require that much power the fuel flow is restricted and the engine puts out only the required amount of power: 24 kW.

But if conditions changed and the prop required more power the engine would add more, up to it's limit at which time it'd dump in more fuel than it could combust and you'd end up with black smoke coming out the exhaust.
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Old 27-07-2011, 14:19   #163
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Re: Electric Propulsion

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I think the prop curve is the prop power requirements. In that case it takes 24kW to turn the prop at 2600 rpm. The engine is capable of around 35-36 kW at those rpms, but since the prop doesn't require that much power the fuel flow is restricted and the engine puts out only the required amount of power: 24 kW.

But if conditions changed and the prop required more power the engine would add more, up to it's limit at which time it'd dump in more fuel than it could combust and you'd end up with black smoke coming out the exhaust.
It is unclear (to me) whether that prop curve is for shaft or brake power. However, for our purposes it is immaterial – after all, what is +/- 1 kW among friends. Otherwise, I agree with what you say, but fail to see your point.

My point was to reiterate what others have previously said: that the diesel vs ‘equivalent’ electric motor issue is mainly explained by the difference in rating, where the diesel is rated for max output (but usually run at much lower power) and the electric motor is rated for cruise conditions (but capable of higher output).
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Old 28-07-2011, 02:09   #164
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Re: Electric Propulsion

Quote:
Originally Posted by Lee Jerry View Post
I was wondering about props too, and was surprised no one has mentioned them yet. I would presume that electric would use a little "larger" prop (in diameter or pitch or both) than diesel, gaining a little propusive efficiency. Can any of the electric operators confirm or comment on this?

edit - Well, higher pitch would probably not increase efficiency. The point is that there is most likely a different propeller match.
Hallo Lee Jerry,
we use 3 bladed props tractor mounted ( forward facing ) of 17 x 7 with a DAR of 71 %
(Displacement area ratio )
This is a high efficient prop and normal cruising RPM is between 900 and 1150 ( 5 to 7 knots) in order to save energy
The low pitch is chosen for better regenerating
We are able to use a high resistance prop like this because if the motors are not in use they are lifted out of the water see below.

we are still changing props to find the best combination of propulsion and regenerating.

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Old 28-07-2011, 06:49   #165
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Re: Electric Propulsion

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Originally Posted by Lee Jerry View Post
I was wondering about props too, and was surprised no one has mentioned them yet. I would presume that electric would use a little "larger" prop (in diameter or pitch or both) than diesel, gaining a little propusive efficiency. Can any of the electric operators confirm or comment on this?.
Lee Jerry:

I am using the same 3 blade 16 inch 13 pitch prop I used with the Westerbeke diesel and it works fine for me. So I did not see the need to change it. Going larger would have entailed a shaft and possible shaft strut change. It's possible I could improve things a little bit with a pitch change too., But, I'm if it ain't broke don't fix it guy.

As far as plowing into head seas for hours I did not do it when I had my diesel either. Not my idea of fun and not real healthy for the boat and rigging. I take the inscription at the U.S. Navel Acadamy to heart:
"You can't out slug the ocean. But, you can out think the ocean"
That said I have plowed into twenty plus knot head winds and steep waves to get out of inlets at times. I've been in near gale (35 knot) conditions where I was doubled reefed for hours where I used the propulsion system to point the boat up a little higher so I could make it around points of land without tacking. I've also dropped sail and operated under battery power to punch through a nasty squall line. Which BTW it is much more pleasant experience when hunkering down below than with a diesel. You can actually converse with the crew and hear the thunder moving away from you. I agree with Steve EP also makes you a better sailor but, having electric propulsion also enhances the sailing experience too with it's quiet operation when you need to use it.
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