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Old 12-12-2018, 11:57 AM
LordGothington LordGothington is offline
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There are a lot of questions about 'why', which I will answer. But what I care about is the 'how' So, I am hoping we can focus on the 'how' instead talking about what a terrible idea this is. Buying a boat is already a stupid idea -- why stop there!

Quote:
Originally Posted by romantic comedy View Post
You say that there is no room for a gen and an engine, but yet there would be room for a dive compressor and HVAC, and a large battery bank , (and additional tankage)?
Well, the dive compressor is a stretch -- especially when I consider also needing enough dive gear for 2 people. It was just the first example of something that would require a high load for more than a minute but less than an hour. It is not a good example. Let's just say that sometimes I need to spend an hour blow drying my hair, but it makes the boat too hot, so I have to run the AC as well. The point is that I expect to sometimes want to drive a load that goes beyond what a reasonable battery bank could provide. But I don't need to run that load all the time.

If we assume that I am definitely going to install a new battery bank plus some other stuff -- and that I need a generator to top off the batteries -- then it seems like something has to go. So, one idea is to replace the current drive system with an electric motor. That gets rid of an engine and exhaust system, and means I can use the existing tankage to instead supply the generator. An electric motor is definitely much smaller than the Atomic 4 + exhaust system + fuel tank. Also, I can get rid of the two starter batteries -- so that frees up more space for the added LiFePO4 batteries.


Quote:
Originally Posted by romantic comedy View Post
What size battery bank and how would you charge it? It would need to be quite large if you were heating, cooking, running radar, running computers, and running air conditioning all off electric.
I have not done the math yet, I am still exploring what is even feasible. My gut instinct is 4x 100A LiFePO4 batteries. I think that should provide a balance where if I am being conservative I can run a generator for an hour a day or less to top off the batteries. Additionally, if I am doing something short term with a high load (like running the magically small dive compressor), I can run the generator during the period of high loads.

The AC might be too much for the batteries alone. That would be something that I might only run on shore power -- or maybe that is when I fire up the generator.

Quote:
Originally Posted by romantic comedy View Post
My question is why...[
I decided that instead of spending $1500-2000 a month on rent, I'd rather spend it on stupid boat projects. So now I cruise full time.

Right now it is basically like camping full-time -- there is no fridge, the condensation drips from the ceiling when it gets cold at night, I use an oil lamp to light the boat, and I have to pay $30-60/night if I want electricity and WiFi, etc. And that assumes I am even near a marina.

I'm also not wild about gasoline on a boat, and eventually this A4 is going to need to be replaced or need an expensive rebuild. So I want to have my options mapped out clearly in advance. While replacing a dead A4 with a diesel engine is a common and non-controversial option, I am not sure it is the best option for me. A vast majority of the time I motor for less than 10 minutes -- which is not stellar for a diesel engine. Also, I like electricity. If I can only be good at generator propulsion or generating power, but not both, I choose power.

Quote:
Originally Posted by ndutton View Post
OK Lord, it's clear you have given this a lot of thought although I'm a little confused on whether or not you plan to run a 48V 200A generator/alternator off of the A-4 or install a diesel genset instead.
The dream is to eventually replace the A-4 with a diesel genset. But given the high cost of doing that -- and the possibly disappointing results, I am trying to find ways to test the idea before committing 100%.


Quote:
Originally Posted by ndutton View Post
[*]The electric drive alone does not save much, if any, space. If space saving is the goal I think you'll be disappointed.
I would agree that simply replacing an Atomic 4 with a diesel electric setup is not going to save space. However, if I am already planning to add a large battery bank, and also want an efficient generator to charge it, and that generator runs on diesel -- now we see space savings. It seems clear that:

electric motor+motor controller+batteries+diesel genset+diesel tank

takes up less space than:

atomic 4 + atomic 4 exhaust system + gas tank + batteries + diesel genset + diesel tank


Quote:
Originally Posted by ndutton View Post
[*]If intending to use the A4 to power a generator/alternator, the Hanley drive requires an early model head and cooling system.
I probably meet those requirements. I have an very early model engine -- though the cylinder block (?) has been replaced -- so I do have the front oil fill tube. Everything else is early early model. I don't even have a thermostat and recirculation loop, it just runs at maximum cooling all the time. (This is a separate issue that should perhaps be dealt with).

Quote:
Originally Posted by ndutton View Post
[*]Converting to electric drive will cost somewhere around $6K. If fitting a diesel genset, figure another $10K by the time you're done. Big money in my opinion for an electric range and air conditioning.
Hence the desire to break up the conversion into smaller steps -- and perhaps realize along the way that I don't need to go whole hog. I assume the $6K includes the cost of the batteries? I think the motor is around $1K and I think another $1K for the motor controller,etc? And $4K for the batteries? I am probably spending $4K on the batteries anyway.

Quote:
Originally Posted by ndutton View Post
[*]If driving a gen/alt with the A4 or a diesel, a 200A 48V genny is about the same size as an A4, maybe slightly smaller so I'm not seeing the space savings.
The space savings is in having an electric motor+genset instead of A4+genset. The primary purpose of the genset is for keeping the house batteries topped off and power high load electronics. The secondary use is long distance motoring.

Quote:
Originally Posted by ndutton View Post
[*]I think driving a big gen/alt off of the output end of an engine, any engine, is preferred to a belt drive off of the flywheel if for no other reason than avoiding side loads on the crank.
By output side, I am guessing you mean the output of the transmission where it hooks up to the propeller shaft? I considered that as well. It seems to have two potential drawbacks

1. it requires the transmission to be engaged -- which is more moving parts to break. Since the engine and transmission share an oil system, I do not think it is viable to remove the transmission?

2. I believe the transmission is reducing the RPM, and for the alternator we want to be increasing the RPM?

I do not have a good solution though -- and that is really what this question is about. People are distracted by the 'why' but what I actually want to know is the 'how'.

Quote:
Originally Posted by joe_db View Post
Basically you are trying to create a miniature version of a diesel electric tug, cruise ship, submarine, or locomotive.
Yes. This is a stepping stone to eventually building a turbine-electric boat someday.

Quote:
Originally Posted by joe_db View Post
1. Engine to prop is more efficient than engine to generator to motor to prop, every transition loses power.
Yes. Going electric would definitely decrease fuel efficiency. But for a sailboat that is mostly sailed, that isn't really a concern. There are sailboats out there with electric motors that are charged purely via solar. But, they don't have a good plan B for when they do actually need range. The genset provides that plan B for when you absolutely must motor a long distance.

If all you are focused on is propulsion, then converting an existing boat to diesel electric will never pay for itself. In my use case, powering the electric motor is a secondary use of the genset, not the primary.

Quote:
Originally Posted by joe_db View Post
Specific to A4s, the Atomic 4 is about the worst engine I can imagine for this job. The A4 was NEVER intended to do anything but move boats. Gensets on boats use engines with standard bell housings that make adding a generator quite easy. Diesel engines are better suited to be generators for the most part, although there certainly are gasoline marine generators. In either case these will be WAY more reliable and efficient than kluging a generator onto an Atomic 4.
Exactly! My A4 is great at moving my boat and not very good at generating electricity. What I think I want is a system that is great at generating electricity, and (because you can't have everything), not as great at moving the boat. That is because I value electricity for creature comforts more than motoring efficiently.

Given enough space I could install all the creature comforts, plus a diesel genset, and keep the A4. But, given the space constraints something has to go.

Given the high upfront costs and potentially disappointing end result, I am looking for ways to break the conversion process up into smaller steps. One way to test the waters is to convert the existing A4 into an inefficient generator. If everything is peachy except for the noise and fuel consumption of the hacked up A4 genset, then it could make sense to yank the A4 and put in a diesel genset, because at that point I will have proven that the idea works. And, if it turns out I don't want to go that route after all -- I still have a functioning A4.

So I think I can break this up into 3 steps instead of my original 2 steps. It seems to me that while a big alternator has the *potential* to require a lot of HP -- if the alternator is lightly loaded, it should only be marginally more taxing than my current alternator? So I just shouldn't try to motor *and* blowdry my hair at the same time?

This is my new plan:

step 1: install a new house battery system powered by 4 100Ah LiFePO4 batteries. (I need to put together a spreadsheet to calculate my real expected usage, but 4 seems like a good number based on what I have seen installed on other boats).

I don't see how that step is avoidable if I want to be able to do things like leave my AIS/anchor lights on, run my laptop, have sufficient interior lighting, using radar, etc. Especially if I am primarily sailing.

I will do what I can to install solar and/or wind generation - but being on a Yawl makes placing solar panels effectively pretty tricky. If I run it as a 48VDC instead of 12VDC system then I will need a 48VDC alternator -- but it doesn't have to be huge.

In this setup the A4 still drives the propeller. It can also top off the battery bank, but I'd potentially have to run it for several hours per day or charge it up at a marina (which costs $30+/night).

Maybe it turns out that I can generate enough power via solar+wind. Also, I do already own an Honda EU2000i (it is currently used to power my PA system, and not on my boat). Maybe I'll decide that solar+wind+honda is sufficient. Since the A4 and Honda are both gas, I don't have to carry two types of fuel. If this is the case, then I am done!

With out the generator, I am not going to be running any heavy loads for extended time periods. The generator gives me the ability to run a 1500W load indefinitely.

step 2: install an electric motor and a much beefier alternator.

This step allows me to test the electric drive idea. The fuel efficiency will be terrible compared to the direct drive system -- but it should also provide a lot of useful data on how big of a genset I would really need, etc.

With this setup, I expect my cruising speed would probably be reduced. For short bursts, the batteries + hacked up genset could provide enough current, but I'd probably have to reduce my cruising speed for long distance runs. On calm water, my boat does almost 3 knots with the A4 at minimum throttle. It takes quite a bit of throttle to get it above 5 knots. So, maybe for this part of the experiment, I cruise at 3 knots and only go 5 when I really need it.

A majority of my motoring is in the harbor, so 3 knots is plenty. It could definitely be a problem when running against strong currents though.

In general, I don't have to be anywhere, and I'd rather be sailing than motoring. If I have sufficient power and Internet I can stay put until conditions are favorable for sailing most of the time. (But not always, hence the need for a motor than can do long runs when needed).

With this setup I can also run higher loads for longer time periods -- if I am willing to run the engine while I am doing it.

This steps proves that the idea is viable, and gives additional data about what size genset would be appropriate. One reason to move onto step 2 is if step 1 is proving unsatisfactory. But, I also need to consider what happens if my A4 dies.

step 3: after abusing my A4 as a genset, it kicks the bucket and I convert to a real diesel genset

At some point the A4 is going to suffer an expensive catastrophe. For most people that means either rebuilding the A4, or installing a modern diesel engine.

But if steps 1 & 2 have gone well, I could feel confident in the 3rd option, which is installing a diesel genset and going diesel electric. If I *already* have to replace my engine, then the cost of installing a diesel genset is less scary.

In summary, step 1 needs to happen regardless because while I can get by with out creature comforts, I do still enjoy them.

step 2 is a moderate investment, but fully or partially reversible. If the electric drive is a failure, maybe I sell the electric motor, but keep the larger alternator.

step 3 is deferred until I have to replace the A4 anyway -- in which case I would have to pay big $$ for a new engine anyway, so a diesel genset is a less extravagant expense. Or, I decide for other reasons, that I am willing to pay for that extravagance. In the long run, the monetary payoff is not paying for transient slips all the time. It would have to avoid transient slip fees several hundred times for that to be profitable, but as a fulltime cruiser, I have 365 chances a year to do that. (And some times 366).

So, back to my original question which is:

What is the best way to hook a big alternator up to an A4, assuming I am willing to disconnect propeller shaft from the engine.

It sounds like side loading is a big concern with mounting an alternator+pulley system on the front of the engine. But if I mount it at the rear, how do I get the required RPM?
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