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Old 27-05-2016, 17:50   #1
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Lagoon 420 hybrid + modern tech

It is my understanding that the hybrid system of the Lagoon 420 was essentially a failure due to battery issues and high gas usage. What if this system was revisited using Tesla batteries, folding props (giving up regenerative capability for efficient sailing), and modern high power solar (to make up for a lack of regenerative prop spin)? It would seem to me that the weight would come weigh down (lower battery weight and one less engine) and modern solar would provide far more "passive" charging without a sacrifice of speed while reducing generator load to reduce gas consumption. Thoughts?
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Old 27-05-2016, 18:10   #2
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Re: Lagoon 420 hybrid + modern tech

It would be marginally better, but not substantially so. The fundamental problem is that there isn't enough power in sunlight for propulsion, and batteries aren't energy dense enough to compete with liquid fuels.
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Old 27-05-2016, 18:16   #3
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Re: Lagoon 420 hybrid + modern tech

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It would be marginally better, but not substantially so. The fundamental problem is that there isn't enough power in sunlight for propulsion, and batteries aren't energy dense enough to compete with liquid fuels.
Not even the new lithium ion batteries? There must be reason that most trains share this propulsion system.
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Old 27-05-2016, 21:52   #4
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Re: Lagoon 420 hybrid + modern tech

I'd say it's lack of funding and lack of huge demand so development would make sense. Proper engineering (Toyota, Tesla) can create amazing things.
Existing systems are full of compromises and awfully overpriced.
Hybrid in it's current state with proper (powerful) solar setup will not completely eliminate using of fuel, but will allow some comfortable silent cruising and in many cases will allow to keep engines from starting.
We recently had big discussion on this.
Parallel hybrid drive
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Old 27-05-2016, 22:12   #5
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Re: Lagoon 420 hybrid + modern tech

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Not even the new lithium ion batteries? There must be reason that most trains share this propulsion system.
Trains use diesel-electric because an 18 drive wheel mechanical transmission is insainly complicated.

The Li batteries help, but they are still about 1/50th the energy density of diesel fuel by weight. So for every gallon of diesel you need about 350lbs of Li batteries. It really isn't comperable.
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Old 28-05-2016, 00:56   #6
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Re: Lagoon 420 hybrid + modern tech

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Trains use diesel-electric because an 18 drive wheel mechanical transmission is insainly complicated.
The big problem that electric drives solve is the clutch. You can imagine the hammering a clutch would take trying to get a train moving. Electric motors, because they have maximum torque at zero RPM are ideal for this. Similar reason why they're used on big ships.
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Old 28-05-2016, 03:54   #7
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Re: Lagoon 420 hybrid + modern tech

The 420 has argueably been the maker's most criticised model. As a sailing boat, probably the worst performer, and certainly not an exquisite example of French chic styling. Even the most ardent Lagoon critics, and plenty exist on this forum, must give some credit for innovaton. At least some points for trying to develop a production hybrid diesel electric sailing vessel that promised regeneration whilst sailing or at anchor.

Perhaps in hindsight, the model was premature. With the advent of lighter, smaller LiFePO4 batteries and more efficient solar panels the whole boat could have been lighter in weight? Then the hulls could have thinner and more efficient when sailing. Regeneration via the propellors when sailing may have then been enhanced. The design could have been made more aesthetically pleasing without the huge weight penalty of large generators, battery banks, etc. Perhaps, perhaps?

The L420 was only one of the many, largely unsuccessfully attempts at a viable diesel electric cruising catamaran. Part of an evolution that will one day happen.
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Old 28-05-2016, 10:26   #8
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Re: Lagoon 420 hybrid + modern tech

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Trains use diesel-electric because an 18 drive wheel mechanical transmission is insainly complicated.

The Li batteries help, but they are still about 1/50th the energy density of diesel fuel by weight. So for every gallon of diesel you need about 350lbs of Li batteries. It really isn't comperable.
This is not about replacing the energy of fuel. That is a lost cause. It's about efficiently using it and storing for later use. Precisely the area that has made quantum leaps since the 420 attempted.
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Old 28-05-2016, 10:33   #9
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Re: Lagoon 420 hybrid + modern tech

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The big problem that electric drives solve is the clutch. You can imagine the hammering a clutch would take trying to get a train moving. Electric motors, because they have maximum torque at zero RPM are ideal for this. Similar reason why they're used on big ships.
Makes sense
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Old 28-05-2016, 10:34   #10
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Re: Lagoon 420 hybrid + modern tech

Another way of stating this is, how far would a tesla go with a generator in the trunk and a full tank of gas? Answer: a long way
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Old 28-05-2016, 12:39   #11
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Re: Lagoon 420 hybrid + modern tech

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This is not about replacing the energy of fuel. That is a lost cause. It's about efficiently using it and storing for later use. Precisely the area that has made quantum leaps since the 420 attempted.
The problem is that there hasn't been a quantum leap in the electrical side. Electric motors have gotten no more efficient, in large part because they were already pretty close to maximum efficency.

Solar panel output has gotten marginally more efficient, but there simply isn't enough power in a given area of sunlight. Even a 100% efficency solar panel doesn't provide enough power for serious propulsion.

Battery tech has gotten better, but is still orders of magnitude worse than it needs to be. FLA batteries can at best hold hours of power, lifepo maybe adds a few hours to that, where a normal boat can carry days if not weeks of diesel.


Before distance cruisers can be reasonably reliant on electric propulsion let's try and get air conditioning to work off of it first. So far it still isn't practical to run an AC from solar/batteries which draws a fraction of the power that propulsion does on a 40' Cat.
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Old 28-05-2016, 12:40   #12
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Re: Lagoon 420 hybrid + modern tech

The issue is always range and with a cat that sails very well this would never be an issue. With the lagoon it is problematic as they rely more on engine then many other multihulls.
The principle is excellent but the decision must be made as to whether you are a sailboat with an auxiliary or a motorboat with sails.
Ideally sailing well with auxiliary power used rarely defines a sailing cruiser, and one would expect that the auxiliary would then be light and a small proportion of the vessels cost in that instance. In my view, a sailboat rarely needs 100 mile motoring range, if it does it may not be a very good sailboat.
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Old 28-05-2016, 12:55   #13
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Re: Lagoon 420 hybrid + modern tech

I am amazed to sea how romantic ecology minded sailors and vendors of electric cats ignore the basic facts:

1- As STUMBLE said The Li batteries are still about 1/50th the energy density of diesel fuel by weight. So for every gallon of diesel you need about 350lbs of Li batteries.

2- 1 HP = 735 watts : so even if you manage to cram 700 watts of solar panels on your boat, which will produce some 700 watts 5 hours per day, you have only accumulated 4.8 HPxhours in your batteries; after transmission losses you can produce 4 HP during 1 hour on the prop shaft.

3- 1 SHP (shaft horse power) is equal to 735 watts. A cat the size of a LAGOON 420 needs 2 x 40 HP ; Yet LAGOON marketed the L 420 with, if my memory serves me well, 15 KW electric motors on each shaft, that is 20.4 HP . I remember vendors arguing that electric power could not be compared to diesel power, raising such irrelevant issue as torque produced at zero revs, which is irrelevant to the power and energy issue, or some mythical 'electric prop' which you could not compare to diesel prop.

Any one tempted by an electric solution should keep in mind the following minimum requirements.
Aboard, say, a 44 ft catamaran, normally fitted with 2 x 40 HP diesels
1 - Will the electric batteries & motors deliver 2 x 40 shaft HP during one hour as may be needed in a blow
2 - Will the electric batteries & motors deliver 2 x 20 shaft HP during 48 hours as may be needed in a windless crossing
3 -What are the true total weight and total cost of the proposed electric system ?
And do not let yourself be fooled by a mixture of Li ion batteries for weight and lead acid for price, electric power being different from diesel power, or nave faith in technological progress.
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Old 28-05-2016, 13:08   #14
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Re: Lagoon 420 hybrid + modern tech

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The problem is that there hasn't been a quantum leap in the electrical side.
This is exactly right. The math hasn't changed and the improvements we've made in the decade since this boat was introduced are marginal at best.

The energy density of the latest batteries is slightly better than older lead acid batteries (2-5x), but nowhere near fuels. Diesel still has around 14x the energy density of the very best, very latest lithium ion cells. It's closer to 25x the energy density of common cells. These batteries have very good properties - extremely low ESR so they can supply a lot of current with little loss in heat, and no Peukert effect so they can accept almost an unlimited amount of charging current. But you still need a lot of them to get even a little power.

The Lagoon 420 hybrid had two 8 kw motors for 16 kw total. When you consider a 1000 amp-hr 12 volt bank has 12 kw of energy at full charge you start to see the problem. You need a lot of batteries to supply any range, especially when you factor in losses in the motors, wiring, converters, etc. Given the power burn, you're going to spend all your time charging the batteries, and although they produce great low end torque as 44 points out, this sort of charging is less efficient than just running a diesel engine.

I know someone who delivered one of these things just up from San Diego to Long Beach for a boat show. He didn't really stop to think until they got going that 8 kw = 10 HP more or less. Even with the generator it was hard to run both motors over a long distance, so with basically 1 10HP motor they made about 2.5 knots the whole way up.
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Old 28-05-2016, 13:21   #15
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Re: Lagoon 420 hybrid + modern tech

Here we go again
Let's repeat - hybrid+solar will not replace or eliminate engines.
But:
1.About 70% of engine wear accrues at start-up (no, it's not joke). So every time you start engine for short run, you basically kill it. Electric motor will eliminate short engine runs, drastically prolonging their life.
2. Even kids know that any engine most sufficient on high RPM, high power. That's when they should be used. For anything else - there are electric motors, which have close to 100% efficiency on any RPM and load.
3. Sail boats created for sailing. Motoring is intermittent every now and then. So in many cases there should be enough time in between for battery re-charging.
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. There are lots of power hungry toys, they all need power. While these batteries and panels still not cheap, they becoming more affordable. So most parts for hybrid is ALREADY THERE, just install electric motors end enjoy
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