Lagoon 420 hybrid + modern tech

[cwjohm]

Could you please explain more in detail why this is needed? If you have a genset with a decent tank, why do you need to have a battery lasting for 48 hours on 1 motor?

Yes, I should have been more precise. The trouble is there is two themes in this thread. The first is EP for cruising passages and the second is living without diesel engines in a fixed spot via solar.

So, I should have said "electrical capacity".

Dealing with passaging in cruising in passaging in my view for safety you need at least 4 hours at full power. Actually I have experienced situations where you need more time than this but really it is of no consequence because any reasonable time criteria sets you electrical requirement for EP.

In my boat you would need at least two 40kw electric motors so you need an 80Kw instant electrical requirement or a 320Kw longer term requirement. This can either come from generator or batteries but in either case you are talking considerable cost and weight. Also in the strict EP case you have one point of failure (the generator) whereas with dual diesels you always have a backup.

You also need to consider the possible 48 hour motor in passaging. Even the best sailing boat cannot sail when there is no wind. In this instance in my boat the sizing of the generator would equate to one motor or 40Kw electrical capacity. If I was designing an EP boat I would probably install a pretty large battery bank which would provide a significant part of my emergency requirement assuming that that the motor times could be minimised on passages but battery size / generator capacity is balanced by a financial equation.

In the case of hybrids you can have dual 40KW diesel/generators but for a lot of cost what do you really gain as against diesels alone.

In either case there is no substantial fuel savings.

In the case of standalone subsistence without diesels this has been well covered here.

At the end of the day though as Stumble pointed out in the first instance this is a simple matter of physics and energy densities, and diesel is so far ahead of any other methodology at this time that an EP boat for safe and cost effective passaging will not arrive for some time yet.

There are some candidates for batteries that offer vast improvements in energy densities so I would assume there will be an effective EP solution in the decades to come, but for now there is no real option other than diesels unless your boat is very localised and requires only short distance motoring in relatively benign waters.

[Stumble]

Originally Posted by myocean

Could you please explain more in detail why this is needed? If you have a genset with a decent tank, why do you need to have a battery lasting for 48 hours on 1 motor?

I like to thank BigBeakie for his valuable comments.

You don't need a big battery bank, heck you don't need a battery bank at all for an EP boat. What you need is the ability to power the propulsion motors at high speed for a minimum of 4 hours, and at cruising speed for some period of time (I think at least 24 hours).

What people perpetually fail to understand is how much power a boat needs while operating at full power, or even cruising speeds. House loads like AC, cooking, lights, are all a rounding error in regards to the amount of power a boat need to push it at close to hull speed.

To put number to it, my boat requires something on the order of 35kw to reach hull speed. By comparison my house and the two neighbors next to me each have 120amp power from the grid. Meaning that our three houses COMBINED can at the absolute max draw the same amount of power my boat demands at 8kn. In reality a boat at hull speed is probably huffing down about the same amount of power as the entire side of my street.

So why the big batteries? Because the only other option is to have a generator sized to put out the same amount of power your propulsion motor needs at maximum. So in my case I would need to install a 35kw generator to power my 35kw needs. The other option is of course a larger battery bank and a smaller generator. It's the matching of these sizes that's important, not the actual size of either.

So how big does the battery bank need to be? Will it depends on the size of the generator. But if we assume a normal house load generator for a boat the size of mine (40') as a 6kw, and let's assume I can convert 100% into propulsion...

For 4 hours at full power I need 140kwh. Over that same four hour time frame my generator would put out 24kwh, so I need to make up the remaining 116kwh from batteries.

Again this is simple math, a 100ah 12v battery has a total capacity of 1.2kwh, and a usable capacity of 600wh. So to provide four hours of full power I need to install 194 100ah 12v batteries.

Clearly that won't work, so let's assume I install a massive 20kw generator on my boat... I still need the same 140kwh but now my generator is providing 80kwh over that four hour time frame. Leaving just 60kwh that needs to come from the batteries. So I only need 100 batteries.... Crap that won't work either.

I now install a 30kw generator, leaving a paltry 20kwh that the batteries need to provide... So I just need... 34 batteries. This might be just doable....

So to replace my 35kw diesel and to get a minimum amount of emergency power I just have to instal a 30kw generator and a 3500lb battery bank.


Of course the electric power advocates say they don't need four hours of run time. And they are right about 99% of the time. But Diesel engines aren't sized based on how much power you will generally need, but based on a worst case scenario. Building a reasonable electric system to motor a few hundred yards in and out of the marine is trivially easy, but building one that has the power to motor into a 50kn headwind to keep the boat off the rocks is next to impossible, while a diesel can do it with room to spare.


Now on the duration side, assuming I slow down to 4kn, I am using about 9kwh from the motor. If I want to be able to do this for 24 hours then the only option is a 9kw generator but this is massive compared to what I need for house loads. It will work, but when I run it at night to power the AC it's going to operate at around 1/2 rated capacity, which is getting close to the dangerous range for a diesel. It's barely enough load to keep it up to temprature.

[myocean]

Greg, for your calculations it might be useful to look at the automotive sector.
Do you know what capacity a Tesla battery has and what the use of such batteries means for future boating solutions?

[gjorgensen]

Originally Posted by myocean

Greg, for your calculations it might be useful to look at the automotive sector.
Do you know what capacity a Tesla battery has and what the use of such batteries means for future boating solutions?

The model S is available with 70 kWhour or 90 kWhour battery packs running at 375 volts nominal. Because the pack voltage is so high, 240 V AC is the preferred charging voltage, although 120 V AC works as well. The cost of that 90 kWhour pack is currently estimated at around $40,000 but probably dropping significantly over the next 24 months.

[Stumble]

The Tesla S has a couple of options, but the 85kw battery weighs in at 1200lbs. So figure this gets you about two and a half hours of motoring at full power. If you add two you are reasonably there with a little reserve. At a cost of about $90,000 and a all up weight of 2,500lbs.

Once the batteries are depleted however you are still left with a very expensive boat that effectively has no motor. Recharging this battery is going to take some time.

Astandard wall plus is 20amps at 110v so an output of 2.2kw. Assuming a 100% efficient charger it's going to take 77.2 hours to charge.

If you happen to have a 50 amp shore power plug that can operate at 100% rated draw it will only take 31 hours to recharge.

Now if you want to try to recharge this from solar panels... Park it for a month and it will likely be close. If you had 5 X 360w panels you would expect 1.8kw/hr at peak generation, or about 10.8kw per day under ideal circumstances. So to recharge this bank is going to take around 18 days of perfect solar generation to operate the boat for 4 hours or so.

Now this assumes everything else on the boat is off, no lights are used, you turn off the fridge... Etc.

In effect you have replaced a $10k motor and $15 of diesel with a $100k battery, a $7k electrical system, and a couple grand in solar panels. BUT you save $15 in diesel so that's a plus.

[BigBeakie]

Dealing with passaging in cruising in passaging in my view for safety you need at least 4 hours at full power. Actually I have experienced situations where you need more time than this but really it is of no consequence because any reasonable time criteria sets you electrical requirement for EP.

I just asked a friend who is a circumnavigator. and has cruised for 18 years on his cat, about how often he has needed to run WOT for safety. Answer was twice, for about 30 minutes duration each time. Once was running into a coral pass against runout tide (when a storm was coming, so didn't want to wait till slack tide) & the other was in strong current & no wind off the BC coast. He did not count lee shore anchorages as it was just to get some pointing clearance & then he sailed out.

But I am inexperienced, and this is an important point. You need to size the EP for the worst case scenario.

What was the scenario that required you to motor at full speed for 4 hours? If it was big wind, why couldn't you sail?

I am genuinely keen to hear the experience of others who have needed to run for extended time at WOT.

[Redreuben]

It's pretty obvious that despite modern lithium batteries the energy densities still aren't there. Interesting to read about the diesel turbines though. As far as avoiding the use of fossil fuels using biodiesel makes way more sense than going electric. But I doubt environmental reasons motivate anyone here.


Sent from my iPhone using Cruisers Sailing Forum

[myocean]

Originally Posted by Stumble

Recharging this battery is going to take some time.

Before you suggested having a 35 kW generator as part of the hybrid system.
Lets say it would just be a 25 kW genset, charging the high voltage battery directly. This would need just 3.5 hrs to fully charge the battery for the next "emergency".
Yes, this is all expensive and still heavy. However, technology is making a lot of progress.

What you have not yet talked about is the potential silence you gain with electric drives. Currently ist still a luxury - for people who can afford it (and they love it). In future it might become more common.

[StuM]

Originally Posted by myocean

What you have not yet talked about is the potential silence you gain with electric drives. Currently ist still a luxury - for people who can afford it (and they love it). In future it might become more common.

Except for the noise of a 25kW generator.

Earplugs are a lot cheaper

[Stumble]

Originally Posted by myocean

Before you suggested having a 35 kW generator as part of the hybrid system.
Lets say it would just be a 25 kW genset, charging the high voltage battery directly. This would need just 3.5 hrs to fully charge the battery for the next "emergency".
Yes, this is all expensive and still heavy. However, technology is making a lot of progress.

What you have not yet talked about is the potential silence you gain with electric drives. Currently ist still a luxury - for people who can afford it (and they love it). In future it might become more common.

Because once you have installed a 25kw generator why not just install a 35kw propulsion engine? it's likely to be cheaper after all, and the electrical system will be a lot easier. Plus you don't have $100k and 3,000lbs in batteries. I just can't see what this system gets you over a propulsion diesel.

I should also point out that a 25kw generator is going to weigh more than a 35kw propulsion motor. The Westerbeak 25kw generator weighs in at 932lbs, while the Westerbeak 42b weighs in at just 419lbs. In part this is because the generator has to develop 25kw at 1800rpm, but also because of the weight of the electrical side of the generator.

The displacement of the generators engine is a little more than double that of the propulsion motor.

[cwjohm]

I just asked a friend who is a circumnavigator. and has cruised for 18 years on his cat, about how often he has needed to run WOT for safety. Answer was twice, for about 30 minutes duration each time. Once was running into a coral pass against runout tide (when a storm was coming, so didn't want to wait till slack tide) & the other was in strong current & no wind off the BC coast. He did not count lee shore anchorages as it was just to get some pointing clearance & then he sailed out.

Like all of these meaningless discussions it depends entirely on how you phrase the question. Old time sailors circumnavigated without engines or gps and if you ask them they would state that they always sailed with safety. Ask yourself whether you would circumnavigate without a GPS today. I met a guy who came across the Pacific in a boat with no motors and managed to get to the coast of Oz aiming for Brisbane but had to divert to Mooloolaba. Even then he had to be rescued by the Coastguard and towed in. Told me he never felt unsafe.

You are doing a 1200Nm passage from Australia to NZ and you get a 40Kn wind on the nose for an extended period. In reality there are only two really safe options - turn and run with the wind and hope you do not hit the Aus coast or put the engines on and motor through. Sailing on a tack broadside to 4-5 m waves is not an option. Your friend may well be happy to turn back. Most would not be happy to turn back. It happened to me and there was no way I was going to turn back.

Coming into Mackay from Vanuatu I again experienced 40Kn winds. I could not turn back as I was navigating through the reef at night. Again it was agreed by myself and the crew that two engines were appropriate given the narrow areas we were navigating in. Again, why night you ask. Well, it is damn hard to predict when you will arrive on a 8 day passage and in my view anchoring in the outer reef in those conditions is frought with danger. Then again your circumnavigator may have a different opinion.

Coming out of the Whitsundays I experienced extreme wind on tides for about 2 hours. This resulted in the washing machine effect you get up there at certain times. I fully admit this was my inexperience in not knowing the local conditions well enough and it will certainly not happen again, but it certainly could do in an area I do not know well.

Ever been on VHF asking the intentions of a 200m ship behind you and being told by an Australian pilot no less to get out of the F&*@ing way. I have, and the ******* would have run straight through me if I had not rammed on both motors and moved out of the way pronto. Sure I was in the right and I would have won in court assuming I had survived.

Try coming around from the north of Port Vila (Mele Bay) where invariably you go from completely flat water protected by Lelapa and Eretoka Islands to go to Devil's point and the South Easter hits you like a wall as does 3 m waves. Ask the locals advice and they will tell you to hug the coast a run both motors flat out for 3 hours. I had a seasoned crew on board and they were quite shocked at the dramatic change of conditions and we had waited for 3 days for what we had hoped were calmer conditions.

These are just a few of my experiences, and I am sure if I had a chat with your circumnavigator with a little prompting he would say "oh yes, there was that time and yes I know what you are saying. That happened to me once." As I say it all depends on how you phrase the question.

[Stumble]

Motoring into Mobile bay with a 35kn breeze coming strain out of the North. At a minimum we had about an hour and a half motor to get in from the ship channel. It was another 2 hours up the channel to get where we were going. We certainly could have stopped and anchored out for three days waiting on a weather window to go 12nm.

Coming into New Orleans up the industrial canal is about an 8 hour trip depending on your speed.

Any trip up a river.

These are all duration issues not max power. Max power in my mind is when you are dragging an anchor in 65kn breeze and have to pick it up and reanchor. I would like to be able to do this more than once while waiting for a TS to pass by.


Do you need a motor? I guess technically you don't. I have sailed a 54' pig into dock before because I didn't have any other choice. But choosing to do this is almost definitional negligence. Just like not having a GPS, or current charts, or a VHF. None of them are required in most of the world, but I have no respect for any skipper who would choose to do this on a duration cruiser.

[Jeannius]

Originally Posted by cwjohm

Like all of these meaningless discussions it depends entirely on how you phrase the question. Old time sailors circumnavigated without engines or gps and if you ask them they would state that they always sailed with safety. Ask yourself whether you would circumnavigate without a GPS today. I met a guy who came across the Pacific in a boat with no motors and managed to get to the coast of Oz aiming for Brisbane but had to divert to Mooloolaba. Even then he had to be rescued by the Coastguard and towed in. Told me he never felt unsafe.

You are doing a 1200Nm passage from Australia to NZ and you get a 40Kn wind on the nose for an extended period. In reality there are only two really safe options - turn and run with the wind and hope you do not hit the Aus coast or put the engines on and motor through. Sailing on a tack broadside to 4-5 m waves is not an option. Your friend may well be happy to turn back. Most would not be happy to turn back. It happened to me and there was no way I was going to turn back.

Coming into Mackay from Vanuatu I again experienced 40Kn winds. I could not turn back as I was navigating through the reef at night. Again it was agreed by myself and the crew that two engines were appropriate given the narrow areas we were navigating in. Again, why night you ask. Well, it is damn hard to predict when you will arrive on a 8 day passage and in my view anchoring in the outer reef in those conditions is frought with danger. Then again your circumnavigator may have a different opinion.

Coming out of the Whitsundays I experienced extreme wind on tides for about 2 hours. This resulted in the washing machine effect you get up there at certain times. I fully admit this was my inexperience in not knowing the local conditions well enough and it will certainly not happen again, but it certainly could do in an area I do not know well.

Ever been on VHF asking the intentions of a 200m ship behind you and being told by an Australian pilot no less to get out of the F&*@ing way. I have, and the ******* would have run straight through me if I had not rammed on both motors and moved out of the way pronto. Sure I was in the right and I would have won in court assuming I had survived.

Try coming around from the north of Port Vila (Mele Bay) where invariably you go from completely flat water protected by Lelapa and Eretoka Islands to go to Devil's point and the South Easter hits you like a wall as does 3 m waves. Ask the locals advice and they will tell you to hug the coast a run both motors flat out for 3 hours. I had a seasoned crew on board and they were quite shocked at the dramatic change of conditions and we had waited for 3 days for what we had hoped were calmer conditions.

These are just a few of my experiences, and I am sure if I had a chat with your circumnavigator with a little prompting he would say "oh yes, there was that time and yes I know what you are saying. That happened to me once." As I say it all depends on how you phrase the question.

Best answer yet. When the great run from Vanuatu turned into 30-40 knts on the nose at Hydrographers Passage and then an 18 hour battle onto Mackay will live with me and my wife forever. Two 40 hp diesels plus reefed main and genoa just about cut it.

[BigBeakie]

Chris & Mike,

Thanks for that very valuable feedback, and examples of challenging conditions. Particularly the Hydrographers Passage thu the GBR, I've heard hairy stories about that before.

Now I'll ask some questions and they are meant to explore whether there are alternative strategies to relying on motoring straight ahead into big wind & seas.

Firstly, the judicious use of a sea anchor to stay put. Could some of those situations have been mitigated by laying in open water and lying to a parachute anchor until more favorable conditions?

Secondly, forereaching into the seas making slow but steady headway, (maybe with opposite motor ticking over to give a rounding up "kick" when needed?) instead of running on a deeper reach and running broadside to large, perhaps breaking, seas? This would not be suitable in tight spots such as Hydrographers Passage obviously. BTW, this is the tactic we used coming back from Lord Howe against horrendous breaking seas( no, no parachute anchor aboard unfortunately).

Thirdly, what HP diesels are needed for a cat to motor into what wind/wave conditions? I guess from both of you I'm hearing that 40HP at WOT is needed to make headway against 40 knot seas? What SOG did that give you?

This will be valuable information to assess the Kw motors needed & size of the EP battery bank AND the DC genset size.

FWIW, I don't think it is feasible (ie weight, space & cost) on an average size cruising cat, to have gensets big enough to run the motors WOT for hours on end. It is feasible to have an LFP bank big enough to run WOT on one motor for 2 hours, and for cruising speed, quite a bit longer. Running 2 motors WOT would not give much more speed but would drain the bank much quicker.

Anyway your thoughts on the viability, or otherwise, laying to a parachute anchor and forereaching would be greatly appreciated in the context of an EP solution.

[cwjohm]

Rob

You do not need a sea anchor as putting out anything from the bow on a cat is both hazardous and dangerous imo. You can simply hove to and if there is such short wave action as you get knocked use the appropriate motor at low revs to steady. You do need a drogue to slow you down aft when running with the wind.

First Point

In the case I spoke of a chincogan with very experienced crew hove to and there they stayed for 36 hours. We, on the other hand motored hard for 6 hours and were able to get out of the weather pattern. Upon speaking to the crew of the Chincogun they agreed they would have motored if they had their time over again. Some monos hove to - all were damaged - ripped sails, steering.

Second Point

Was your wife on board when you did this. Potentially you will have to do it for a long time. Everybody on the boat will be potentially ill, and freaking out.

Third Point

If you still looking at a FF46 you will need the equivalent of 55HP diesels.

Rob

I have now sailed with guys who have hundreds of thousands of miles under their belts sailing cats. None of them hesitate to use the iron jib in difficult conditions. I am sure based on discussions with them that they could use various techniques to minimise the use of the motors, but they just look at me in confusion, and ask my why I would choose the hard way to do things when the safety of the crew is at stake.

I could well understand someone who has a couple of hundred thousand miles under their belt with many catamarans, trying new technologies knowing full well that they have the experience and ability to get out of difficult situations if they want to, but for an inexperienced husband and wife team this is sheer folly.

Are you going to take passengers on your boat. I can tell you from experience on many occasions in tough conditions that when I give the option of sailing from point to point with various tacks as distinct to motoring to a destination when I say sailing will take considerably longer they inevitable opt for the motor.

I can also tell you that Lisa loves sailing, and always pushes for the motors to be turned off, but when things turn, and conditions get tough, she is always happy when the motors get turned back on again.

I fully understand your passion for the new technology. If you want to get it out of your system buy a Tesla. At least if it fails you pull to the side of the road and they do a new download of software. But on a boat doing anything to limit your options is just plain foolhardy.