Lagoon 420 hybrid + modern tech

[robert sailor]

The biggest challenge is to have a sailboat that will actually sail well in light air, difficult with cruising cats as they have evolved into big boats with little rigs. If you put a rig large enough to really sail well in light air the manufacturer has a large liability so it's hard to believe Lagoon even started down this path.

[Octopus]

I've been the proud owner of a Lagoon 420 Hybrid for the last nine years and have been very happy with the propulsion system and delighted with the whole boat.

Like all boats its design is a compromise and some elements of the design were very radical. The design delivered class-leading accommodation and liveability, for its size, but sacrificed sailing and motoring performance. The boat is heavy, not just because of the twelve lead acid propulsion batteries, weighing in at 840 kg (850 lbs), but also because of the wide capacious hulls and the large superstructure.

Even so, the motoring performance at 6.5 knots cruising speed and 7.5 knots maximum in calm seas, is adequate for most occasions, partly because the class-leading accommodation makes it a joy to be aboard.

Originally Posted by SDChristian

It is my understanding that the hybrid system of the Lagoon 420 was essentially a failure due to battery issues and high gas usage.

I've always been happy with the fuel consumption, so I'm not sure why you think it is poor. It's possible that some people found it poor because they went at full power all the time, because they were not content with its cruising speed. The genset uses 6.1 l/h at maximum output (17.5 kW) and about 4 l/h at cruising speed. I've always thought that anything less than a liter per nautical mile is OK for such a big boat.

The two electric motors are nominally rated at 10kW and the Kubota diesel engine that drives the 17.5 kW generator is 29HP, but together these push the boat through the water at a speed that is only about one knot slower than the 80HP non-hybrid Lagoon 420 hybrids, powered by twin 40HP engines, so it is pretty clear that the hybrid arrangement is more efficient.

It is right that the lead acid batteries are the Achilles heel of the system. This is not just because of the enormous weight, but also because of the complicated control system required to protect the batteries. I'm just waiting for my lead acid batteries to fail, so that I can replace them with LiFePO4 batteries, which will make an enormous difference. It will not only halve the weight of the battery bank, but it will double the usable capacity and I'll be able to ditch Lagoon's complicated electronic control system. It will also be more efficient, because I will be able to charge them at full power, so I'll no longer have to run a 17.kW generator at its most inefficient low-loading, just to trickle charge the batteries for the last hour of charging, to get them fully charged.

I'm not convinced about the viability of solar power to propel the boat. It's fine for re-charging the batteries and keeping up with normal loads, but not for the heavy propulsion loads, unless you are motoring on very short trips.

Some people have installed folding props to reduce the drag when sailing, but this has three drawbacks that I've been unwilling to accept. First, you would lose the ability to generate serious amounts of power under sail, which is very satisfying to recharge the batteries for free. Second, I use the prop drag under ReGen to slow the boat down, when we are going a little too fast for comfort. Third, you lose some manoeuvrability under power as you can't go straight from forward into reverse and get instant thrust. One of the real joys of the hybrid is it's outstanding manoeuvrability under power, owing to the instant torque. Note: the other great joys of the hybrid are: the silence of the whole propulsion system, the low maintenance, the side-effect of abundant AC and DC electrical power for other purposes (cooking, cooling, heating, washing, water-making etc. etc.).

The sailing performance of the 420 hybrid is relatively poor in light winds, owing to its heavy displacement and conservative sail plan, which give it a low SA/D ratio. On the other hand, its performance in stiff winds is great. Last year, I sail a thousand miles from Portugal to Scotland in constant winds of 20 to 30 knots and there is no boat I would rather have been on in those conditions.


Chris

[StuM]

Originally Posted by ranchero76

4. Good power setup (say 20-30 kWh battery bank and at least 2-3kW solar panels) is something that any modern big boat should have regardless of having electric propulsion.

For us liveaboards sailors with only 30-50% of those batteries and panels already taking up an inordinate amount of space and weight, just how "big" are you talking about?

[ranchero76]

Originally Posted by StuM

For us liveaboards sailors with only 30-50% of those batteries and panels already taking up an inordinate amount of space and weight, just how "big" are you talking about?

50-55ft plus

[SDChristian]

Whelp, there you have it.

[GALAWA]

ranchero76 's post is an interesting example of denial of basic electrical facts and figures.
4. Good power setup (say 20-30 kWh battery bank and at least 2-3kW solar panels) is something that any modern big boat should have regardless of having electric propulsion.

30 KWh of batteries can only deliver 30KW during 1 hour = 40 shaft HP during 1 hour. And what do you do when your batteries are flat ?
Charge them with 3 KW of solar panels ? 3 KW solar panels need 10 hours of high sun ( 2 sunny days ?) to accumulate 30 KWh in the batteries.

An remember that the standard equipment of a 44 ' cat is at least 2 x 40 HP diesels. There is reason for that !

...at least 3 KW of solar panels..
1 square meter of solar panels yields 160 watts of peak power; So 30KW will require 187 sq meters of solar panels. The maximum you can cram on the bimini + above the davits of a 44' cat is 700 watts.
So where do you put 187 sq meters of solar panels on a 44 ' cat ?

30KWh of lead AGM batteries cost 6 000 $ and weight 7 200 kg = 7.2 metric tons ! On a 44' cat ?

30KWh of LiFePO4 batteries cost 12 000 $ and weight 300 kg . This weight is better but does not address the power and autonomy issue.

Ranchero76 has since hinted that he thought of 60' cats.
But then the power requirements are 2 x 100 HP and the maths are still against electric motors cum solar panels.

We may suspect that Ranchero76 is a vendor of such electric systems with little offshore sailing experience

[rabbi]

two years ago we passed this "beauty" somewhere in Greece: solarwave


The original builders have sold the boat in the meantime and are now building a better looking one: Solarwave 62 zero emission luxury yacht nears completion and here some photos


I guess electric & solar is OK to get in & out of port but long distance cruising will be at 3-4kn average cruising speed unless the genset runs 24/7

[Stumble]

Rabbi,

It's actually worse than the 3-4kn they claim. The boat can only manage that in flat water with no wind. Add either and the speed drops significantly. Add a 30kn headwind and I would be suprized if the boat can make forward progress, let alone make a passage.

At some point the water and food required totaled X distance starts to add up any you wind up like the space shuttle and fuel... Something like 80% of all the fuel used by the space shuttle is required just to get the fuel off the ground. The more fuel you add the more fuel you need. It's a vicious cycle.

The new 62' has a quoted daily range of 100nm in flat water, given that a trip across the Atlantic will probably take longer, and be more weather dependent than on a Catalina 27. It's a stupid idea as a distance cruiser, but if you can make it to the BVI it would probably be a great boat to move from island to island on.

[myocean]

You may look at this new, state-of-the-art system, including Lithium batteries and
integrated energy management for all electric systems on board:

Deep Blue Hybrid by Torqeedo

Such a solution, including a 'range extender' genset and high voltage 450 V batteries is still rather expensive (like Tesla), but for large boats definitely a viable option!
I am working for this company.

[Stumble]

Originally Posted by myocean

You may look at this new, state-of-the-art system, including Lithium batteries and
integrated energy management for all electric systems on board:

Deep Blue Hybrid by Torqeedo

Such a solution, including a 'range extender' genset and high voltage 450 V batteries is still rather expensive (like Tesla), but for large boats definitely a viable option!
I am working for this company.

I really like what they are trying to do, but the strait up lies in their sales material is hard to swallow. For instance on page 14 of the brochure they imply that 4shaft hp is the same as 1 propulsive hp for gass outboards. Whatever engineering truth there may be to this (which I highly doubt) the fact remains that by law outboards are rated at their propeller and have been for decades. A 4hp outboard is putting 4hp to the prop period.

So they start off the whole sales pitch lying to their customers, from here everything else they say has to be filtered thru this lense.

In fact their entire section comparing shaft, prop, and input HP is just a long list of half truths, nonsense, and lies. Input power for the gas engines for instance is I assume rated as the maximum energy available from the amount of fuel they burn, which is fair as far as it goes, but then they start the electric with the amount of power delivered at the electric motor, forgetting Pukerts, battery losses, charging losses, etc.

If you want to claim that their 2hp is just as powerful as a 2hp gas engine then put them on identicle dingys at the same time and race them. That's all it takes, but for years torquedo has refused to do this, knowing that their advertising is chock full of lies. Until torquedo is willing to test two boats side by side with their 'equivilant' gas engine corrilary it's all nonsense.

One of the actually interesting things that Solarwave is doing is providing a diesel turbine generator instead of a Diesel generator. Due to their smaller size and higher efficiency a small turbine charging a lifepo bank is a really good idea. The batteries can handle the high charging speed when recharging the house banks, or the turning can directly provide power for propulsion. I am not sure if small turbines are really ready for prime time, but it is a fascinating idea.

[casablanca]

Notice that 420 owners love their boats, whether hybrid or diesel. Criticism comes from the others.

We have a diesel 420 and its performance all round is very pleasing.

In our view the 420 configuration (layout, helm position, hard Bimini, accommodation) is the best of all models and its a pity they didn't continue the model. Would not swap it for a later model (421,42) or a bigger boat (440,450,450S).




Bob
CASABLANCA L420 #86

[robert sailor]

Everyone loves their own boat, that's the way it works, ain't life grand!

[myocean]

Originally Posted by Stumble

(...) they imply that 4shaft hp is the same as 1 propulsive hp for gass outboards. Whatever engineering truth there may be to this (which I highly doubt) the fact remains that by law outboards are rated at their propeller and have been for decades. A 4hp outboard is putting 4hp to the prop period.

Prop designers know, that for best performance the prop should rotate rather slow and have a large diameter. But they can't do this for most combustion engines.
This is because a combustion engine does not have the same high torque at low revolutions. With this limitation, it is not feasible to use the same props as for the electric motors, because the combustion engine would not be able to speed up through the low revolution range - just due to lack of torque. So the prop for a combustion engine traditionally can't be designed as it should be to exploit the power which can be made available at the shaft at higher revolutions. Traditionally, especially with outboards, a lot of power is wasted in the high revolution range because the prop is designed to get through the low revolution range with a too low torque.

You may have a look at submarine props. They have the opportunity to go with an ideal prop because they have electric drives. With this, their props are bigger and rotate with lower speeds which is more efficient for the same thrust and at the same time, luckily, quieter.

[44'cruisingcat]

Hmm.. but how many RPM's does a Torqueedo outboard's motor turn at? I'm pretty sure they spin much faster than normal petrol outboards. Like around 10,000 RPM right?


The prop spins at around 1,000 RPM due to the 10:1 planetary reduction gearbox, which gives them the low speed torque, and allows a larger prop. You could do the same with an internal combustion engine.

[myocean]

Originally Posted by 44'cruisingcat

You could do the same with an internal combustion engine.

Yes, right! Ideally you should have more than one gear for a combustion engine, so you can have high torque at low speeds and at high speeds.

The torque thing can be understood by looking at torque/rpm diagrams of combustion engines ("ICE") in comparison with electric motors.

Look at the images Google presents when searching for

torque ICE "electric motor"