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Old 21-01-2016, 16:47   #226
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Re: Ideal Generator?

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The paranoia over propane is sort of like the paranoia of gasoline in a sport fisher. An electrical fire is a very bad thing, fires are my number one concern on a boat, but if your on board you probably have a better than even odds of putting it out, or at least not being hurt. A gasoline or propane explosion on the other hand, one second your laughing, drinking a beer and then instantly your in the water hopefully with third degree burns, or maybe still on the boat being burned alive.
Like a Commercial airliner crash, very unlikely event, but usually very bad consequences, so many people are afraid to fly.


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As can be seen from the statistics posted, it's just not very common for propane to blow up. Given even a modest amount of care, it shouldn't keep you up at night.

On the other hand the idea that you can count on putting out one of those far more common electrical fires is not realistic on a typical fiberglass boat. Usually they start inside a wall or behind a panel and by the time you find out about them, the fiberglass is burning. If you've ever seen a fiberglass boat burning, you will be lucky to get overboard before the toxic fumes knock you out. Let alone putting it out. I've seen a couple of them burn and it's wild.
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Old 25-01-2016, 15:04   #227
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Re: Ideal Generator?

I think some of you guys are looking at things backwards when comparing Propane and Induction cooking efficiencies - a far better way is to look at your Propane consumption and work backwards from there.

Propane has a lower heating value of 46,350 kJ/kg (i.e. the water vapour produced by burning the gas doesn't condense to liquid).

In more sensible units, that 12.875 kWh/kg - but in reality the equivalent level is rather lower because Induction is more efficient at transferring heat to the water - 74% versus 44% - so you're actually at 3.5 kWh of electricity burned to replace a pound of propane, or 174 kWh in a 50 pound bottle.

Now, a quick look through the site suggests that most people don't actually use very much propane when cooking - How Much Propane Do You Use ? gives a variety of numbers which seem to centre on about 0.2 lb per day - equivalent to 0.7 kWh of electricity. At 24V, that's 30 Amp-Hours - as I understand it about what can be expected from a 100W solar panel in the tropics. A pain to fit on some boats, and the additional batteries you'll need will be potentially worse, but as a tradeoff for only carrying one fuel and getting rid of an explosive, heavier than air gas from a confined space? Sounds very promising to me if your electrics can cope.
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Old 25-01-2016, 16:29   #228
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Re: Ideal Generator?

700Wh per day from a 100W solar panel is optimistic. One might get that on sunny days, but not on average days, certainly not year-round. Normally, one should have at least 140W solar panel to produce an average of 700Wh per day. Then about 5% will be lost to the inverter and wiring, so I would plan on 150W of solar capacity to replace 0.2lbs per day of propane. Of course, many people use substantially more than 0.2lbs per day of propane and many (including me) use substantially less.

Before switching from propane cooking to induction cooking powered by photovoltaics, I would recommend keeping an accurate log of how many days of cooking one actually does from one propane cylinder in order to reasonably estimate how much solar capacity will be needed. I would except that I would get by with 50W and some others would need more than 500W.
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Old 25-01-2016, 18:32   #229
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Re: Ideal Generator?

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I think some of you guys are looking at things backwards when comparing Propane and Induction cooking efficiencies - a far better way is to look at your Propane consumption and work backwards from there.

Propane has a lower heating value of 46,350 kJ/kg (i.e. the water vapour produced by burning the gas doesn't condense to liquid).

In more sensible units, that 12.875 kWh/kg - but in reality the equivalent level is rather lower because Induction is more efficient at transferring heat to the water - 74% versus 44% - so you're actually at 3.5 kWh of electricity burned to replace a pound of propane, or 174 kWh in a 50 pound bottle.

Now, a quick look through the site suggests that most people don't actually use very much propane when cooking - How Much Propane Do You Use ? gives a variety of numbers which seem to centre on about 0.2 lb per day - equivalent to 0.7 kWh of electricity. At 24V, that's 30 Amp-Hours - as I understand it about what can be expected from a 100W solar panel in the tropics. A pain to fit on some boats, and the additional batteries you'll need will be potentially worse, but as a tradeoff for only carrying one fuel and getting rid of an explosive, heavier than air gas from a confined space? Sounds very promising to me if your electrics can cope.
You are right - induction cooktop is very efficient, we have a small backup one when we run out of propane (with a turkish tank in Greece .
I am heating tee with el tea pot, it takes 16ah to boil 1.5L.
Baking is with elec convection oven.
So propane is really only for my Magma grill
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Old 26-01-2016, 01:51   #230
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Re: Ideal Generator?

We love our induction plate. Hardly use gas any more.

(Running it of 3500W mastervolt inverter, and 1000AH LIFEPO4)
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Old 26-01-2016, 03:26   #231
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Re: Ideal Generator?

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As can be seen from the statistics posted, it's just not very common for propane to blow up. Given even a modest amount of care, it shouldn't keep you up at night.

On the other hand the idea that you can count on putting out one of those far more common electrical fires is not realistic on a typical fiberglass boat. Usually they start inside a wall or behind a panel and by the time you find out about them, the fiberglass is burning. If you've ever seen a fiberglass boat burning, you will be lucky to get overboard before the toxic fumes knock you out. Let alone putting it out. I've seen a couple of them burn and it's wild.
Those statistics don't show anything about how common or rare propane explosions are.

I can't find any statistics, but cooking gas explosions (mostly Butane in the UK) are one of the most common disastrous events on boats here, with several boats completely destroyed every year, and with fatalities occurring on a regular basis, similar to or greater than the number of boats which sink or are burned in fires. Here is an extremely useful article on the subject: Crash Test Boat - Gas explosion

Risk management on a boat is a complex thing, and of course anyone can spend as little or as much time and energy thinking about this risk versus that risk as he wishes. Fire on any boat (not only plastic) can kill you or destroy your boat, as can sinking, as can falling overboard, as can carbon monoxide poisoning, so all these things, together with gas explosions, are first-order risks which wise skippers will manage in one way or another, all of them. You can of course just do something cursory and forget about it, and rely on good luck, as many skippers do -- your choice. As far as I can tell, however, 90% of cruising boats have substandard practices on gas safety, and/or have gas systems in unsafe condition, so in my opinion this is a risk worth paying more attention to.


But if you could simply eliminate an entire class of these first-order risks at one stroke, why wouldn't you consider doing that? Imagine a boat without through-hulls, or a boat which couldn't catch on fire. Completely eliminating the risk of a gas explosion is of roughly similar value.

There is no such thing as life without risk. But risks should be taken rationally, and you should get something, at least fun, out of taking them.

God willing I will soon be cruising remote places at high latitudes, which is risky for a lot of reasons, such as no rescue services, cold water which will kill you in less than an hour, and harsh weather. I am taking those risks with my eyes open, but I am eliminating other risks as I can.

Thus the next boat will have watertight compartments with the through hulls outside of the main passenger space (a la Dashew), to greatly reduce the risk of sinking (a really serious question in Arctic waters). It will have a sealed engine room nearly eliminating the risk of CO poisoning and engine room fires. And it will have no propane or butane on board. That by no means eliminates all the risks, but in my calculation, is a rational management of them. YMMV.
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Old 26-01-2016, 03:36   #232
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Re: Ideal Generator?

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Those statistics don't show anything about how common or rare propane explosions are.

I can't find any statistics, but cooking gas explosions (mostly Butane in the UK) are one of the most common disastrous events on boats here, with several boats completely destroyed every year, and with fatalities occurring on a regular basis, similar to or greater than the number of boats which sink or are burned in fires. Here is an extremely useful article on the subject: Crash Test Boat - Gas explosion

.
You can debate if it is applicable to UK boats but those statistics clearly show propane is not the most common source of onboard fire (of which explosion is a subset).

If you don't have statistics to counter these statistics, apocraphal comments about being more dangerous are not statistics.

Yes, propane used stuipidly can result in fires and explosions. Just as electric can result in fires (and in rare cases explosions). The statistics provided clearly show electrical fires are far more common.

That said, I have both systems and used with care, I am not afraid of them.
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Old 26-01-2016, 03:58   #233
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Re: Ideal Generator?

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You can debate if it is applicable to UK boats but those statistics clearly show propane is not the most common source of onboard fire (of which explosion is a subset).

If you don't have statistics to counter these statistics, apocraphal comments about being more dangerous are not statistics.

Yes, propane used stuipidly can result in fires and explosions. Just as electric can result in fires (and in rare cases explosions). The statistics provided clearly show electrical fires are far more common.

That said, I have both systems and used with care, I am not afraid of them.
Look, I am not telling you how to manage risks on your own boat. That is entirely up to you to decide what to worry about. There are more than enough things to choose from.


But one thing which I will not refrain from criticizing in your post is this phrase "propane when used stupidly . .. " Propane is dangerous not only when "used stupidly". This is false, and I really suggest you read this:

https://assets.digital.cabinet-offic..._trenchard.pdf

Gas explosions occur even on boats with very high quality, disciplined procedures for using gas, and on boats with high quality maintenance, and not at all only "when used stupidly". Gas explosions are a certain risk, roughly similar to the risk of sinking or fire, in the same order of magnitude at the very least. It happens a few times a year, just like a few boats sink and a few boats burn down to the waterline. None of these in the tens or hundreds, but all in the several units per year, so the same order of magnitude. It only happens to stupid people, and so can't happen to you? It's up to you to decide.

Like sinking and fire, gas explosions are rare enough that it is possible to do nothing at all, spend zero time thinking about it, and not suffer a disaster. But that is very much like -- "I have been driving 20 years and never had a collision in my car, therefore I won't wear a seatbelt." You can roll the dice if you want, and the odds are certainly in your favor, but if you roll wrong once, it may be your last. Therefore many skippers think that complacency (". . . only when used stupidly. . . ") is the wrong approach to this.

Stupidity certainly increases the risk (of gas explosion, fire, sinking), and dramatically, but I would say that complacency increases these risks just as much.
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Old 26-01-2016, 04:04   #234
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Re: Ideal Generator?

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But one thing which I will not refrain from criticizing in your post is this phrase "propane when used stupidly . .. " Propane is dangerous not only when "used stupidly". This is false, and I really suggest you read this:
.
The point is to differentiate people who hold up idiots doing stupid things as a reason to throw the baby out with the bath water. If an idiot can kill himself with a propane system, I have no doubt he can kill himself with an electrical system.

I watched an RV burn to the ground last summer. The owners knew there was an electrical issue but continued to leave it plugged in with the power on. I'm not going to say electrical systems are inherently unsafe due to this. This was stupidity on the owners part.

Used wisely, propane is very safe. Yes, there is still risk but the same holds true for electricity. You can never completely eliminate risk. Every story of propane problems I've come across has been directly attributable to poor procedures or known problems that were ignroed. I would consider that stupidity on the owners part not a safety problem with propane.

Again go back and look at the data posted. Propane is just not on the radar. Yes, propane fires do happen but the electrical fires are far more common, so if you are really interested in reducing risk, your focus should be on the electrical system.
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Old 26-01-2016, 04:31   #235
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Re: Ideal Generator?

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The point is to differentiate people who hold up idiots doing stupid things as a reason to throw the baby out with the bath water.

Used wisely, propane is very safe. Yes, there is still risk but the same holds true for electricity.
OK. Electricity demands at least as much care, as propane, agreed. It's another major risk.

But I was exactly not holding up idiots doing stupid things. The example I gave was the Royal Navy! With better safety procedures and better standards of maintenance, I daresay, than any of us have! That report is especially valuable and especially instructive, exactly because it was a case not of idiots, but of very well trained people, blowing themselves up with propane.

They certainly thought they were "using propane wisely". But they made two mistakes which coincided to cause a disastrous explosion. A gas line was not tightened down sufficiently when a bottle was changed. Can any of us be sure that it can "never happen to us"? Certainly not. And -- the gas locker was not perfectly sealed, although it like the rest of the boat was otherwise very well maintained, as the MAIB confirmed.

After reading the Lord Trenchard report some years ago, I started leak testing my gas locker once a year. I take out the bottles, plug the drain, and fill it up with water, and leave it overnight. Damned if I didn't find leaks on two occasions. It seems that the gas line, copper on my boat, has thermal expansion and contraction, and can unseal itself. So I have started resealing it every year.

Do you leak test your gas locker? Are you sure that it is gas-tight?

The other thing which happened on board Lord Trenchard was the gas alarm was apparently intermittent, so on the fateful morning there was no alarm. Do you test your gas alarm? Do you even have one? Most cruisers I know don't even have a gas alarm.

Other possible points of failure are: (a) cracks in the metal gas line; (b) chafing on the flexible gas line where the stove gimbals; (c) loose gas connections anywhere; (d) failed flame sensor on the stove; (e) leaks inside the stove.

I rely on frequent inspections and testing of these issues, and very much on my gas alarm, with respect to leaks in the system inside the hull volume.

Is it safe? Well, relatively safe, yes. Based on the investment of a fair amount of effort, which improves the odds a lot. But is it risk-free? Certainly not. I don't lose sleep about it, but I would really prefer not to have gas on board at all. As much as for the sake of avoiding the risk, it is to avoid all the effort expended -- wasted -- on gas safety, which I would prefer to invest elsewhere.
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Old 26-01-2016, 05:00   #236
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Re: Ideal Generator?

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Do you leak test your gas locker? Are you sure that it is gas-tight?

.
My gas locker and fuel tanks are bottom vented. They are specifcially NOT gas tight. Any escaping vapors will flow out the bottom and disperse.

This is similar to the reason it's not a concern to have a gasoline powered car.

Of course, I have the benefit of a catamaran where they are mounted on the bridge deck, so bottom venting is a viable option. Also the engine is outside the hull (outboard), so even if there is a fuel system leak there, it won't be an issue (in terms of explosion or fire).

Yes, the propane lines to the stove could leak but far easier to check those as described by others by turning off the tank and checking if it holds pressure. Plus we have a propane sniffer in the bottom of the hull adjacent to the stove.

Could something go wrong? Sure there is always another situation you didn't think of but it's to the point, I wouldn't worry about.
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Old 26-01-2016, 05:14   #237
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Re: Ideal Generator?

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. . .

Again go back and look at the data posted. Propane is just not on the radar. Yes, propane fires do happen but the electrical fires are far more common, so if you are really interested in reducing risk, your focus should be on the electrical system.

Both of the reports posted are about "Why Boats Catch Fire". Not a word about gas explosions, which is a different hazard, so this is just not relevant.

I don't find any statistics anywhere, but Googling boat accidents in the UK in 2015, I find:

4 boats totally destroyed by propane/butane explosions
3 boats totally destroyed by fire
5 boats sunk, 4 of them at their moorings while the owners were gone.

That's not completely scientific, because not every accident makes it into the googleable press, but it shows that these hazards are at least roughly comparable to each other in terms of frequency.

The UK is a good microcosm for this, because of the large number of boats per capita, and much higher proportion of sailboats and boats used on the sea.
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Old 26-01-2016, 05:21   #238
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Re: Ideal Generator?

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Both of the reports posted are about "Why Boats Catch Fire". Not a word about gas explosions, which is a different hazard, so this is just not relevant.

I don't find any statistics anywhere, but Googling boat accidents in the UK in 2015, I find:

4 boats totally destroyed by propane/butane explosions
3 boats totally destroyed by fire
5 boats sunk, 4 of them at their moorings while the owners were gone.

That's not completely scientific, because not every accident makes it into the googleable press, but it shows that these hazards are at least roughly comparable to each other in terms of frequency.

The UK is a good microcosm for this, because of the large number of boats per capita, and much higher proportion of sailboats and boats used on the sea.
Gas explosions are typically filed under fire, so yes, its very relevant.

As far as your examples...what was the proximate cause of the fire. The RV fire I saw this past summer started at the propane fridge but as confirmed by the fire marshal, it was started by an electrical fault and the propane never exploded. But if you simply read that the fire started at a propane fridge, you could come to the mistaken conclusion it was a propane fire.

I never said, you couldn't have a gas fire/explosion. Also when they happen they tend to make the news (and thus become easily google-able). It's similar to a plane crash. A plane goes down and it typically gets international coverage but if you dig thru the stats, you are far safer flying NY to LA as opposed to driving.

I think we are just going to have to agree to disagree on this subject...so back to the topic. How is the generator design coming along?
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Old 26-01-2016, 06:16   #239
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Re: Ideal Generator?

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......
But I was exactly not holding up idiots doing stupid things. The example I gave was the Royal Navy! With better safety procedures and better standards of maintenance, I daresay, than any of us have! That report is especially valuable and especially instructive, exactly because it was a case not of idiots, but of very well trained people, blowing themselves up with propane.

They certainly thought they were "using propane wisely". But they made two mistakes which coincided to cause a disastrous explosion. A gas line was not tightened down sufficiently when a bottle was changed. Can any of us be sure that it can "never happen to us"? Certainly not. And -- the gas locker was not perfectly sealed, although it like the rest of the boat was otherwise very well maintained, as the MAIB confirmed.
Obviously NOT!

All this has proven is that even the Royal Navy, regardless of how high you regard their procedures, make mistakes, they are not infallible. Propane was NOT the fault of the explosion, it was lack of following proper procedure/maintenance.

If the dangers of propane scare the crap out of you, by all means remove it from your boat. But, don't try to convince others that the risk is higher than actual statistics prove.
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Old 26-01-2016, 07:00   #240
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Re: Ideal Generator?

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Gas explosions are typically filed under fire, so yes, its very relevant.

As far as your examples...what was the proximate cause of the fire. The RV fire I saw this past summer started at the propane fridge but as confirmed by the fire marshal, it was started by an electrical fault and the propane never exploded. But if you simply read that the fire started at a propane fridge, you could come to the mistaken conclusion it was a propane fire.

I never said, you couldn't have a gas fire/explosion. Also when they happen they tend to make the news (and thus become easily google-able). It's similar to a plane crash. A plane goes down and it typically gets international coverage but if you dig thru the stats, you are far safer flying NY to LA as opposed to driving.

I think we are just going to have to agree to disagree on this subject...so back to the topic. How is the generator design coming along?
"Typically" -- is a really big assumption, and an incorrect one here. If you will just google "boat propane explosion" it will be obvious to you that these occur roughly as often as other major disasters like sinking or total destruction by fire. You make a mistake my minimizing this really serious hazard. Boats are destroyed every year, and people are killed and maimed, by gas explosions -- that's just a fact.


Fatal Boat Explosion Traced to LPG Leak
Fatal Boat Explosion Traced to LPG Leak
Young Man Killed in Boat Explosion; Father Survives Blast
Young man killed in boat explosion, father survives blast - NL Times

Stuart Boy Killed in Propane Explosion on Sailboat
Eyewitness recounts harrowing tale of boat explosion that killed Stuart boy | video, photos

Two Area Men Killed in Sailboat Explosion
https://news.google.com/newspapers?n...,1450477&hl=en


78 Year Old Man in Intensive Care, Three Boats Destroyed, In Propane Explosion
Explosion on boat linked to propane tank -- Port Angeles Port Townsend Sequim Forks Jefferson County Clallam County Olympic Peninsula Daily NEWS

Sailboat Explodes at Comox Marina
Boat explosion rocks marina - Sequim Gazette

Sailboat Explosion Kills Woman
https://news.google.com/newspapers?n...,2915655&hl=en

Boat Explosion Rocks Marina
Boat explosion rocks marina - Sequim Gazette

62 Foot Schooner Destroyed and Sunk by Propane Explosion
Propane tank likely cause of boat explosion

SEATTLE - A huge explosion and then flames; three boats, three boat houses, destroyed
Three boats, three boat houses burn at Seattle marina

Man Critically Injured in Violent Blast which Destroyed 40 Foot Boat
Man critically injured in violent blast that destroyed 40-foot... | www.kirotv.com

Sailboat Explodes, Sinks, Off Nanaimo
Sailboat explodes, sinks off Nanaimo

I could go on, but you get the point. More or less than catastrophic fires, or sinkings? We don't know, but it doesn't really matter -- obviously propane explosions are not very rare. But of course -- don't worry about -- it can only happen to idiots. Otherwise it's just totally safe.



Another chilling fact about propane is that it contains a surprisingly large amount of energy, so it is really very explosive:

"Propane has an energy density of about 50 MJ/kg (megajoules per kilogram), TNT has an energy density of about 5 MJ/kg (see here). In other words, one pound of propane has about the same energy as ten pounds of TNT. Granted, relative to TNT, it is far more difficult to get propane to explode such that all of the material is consumed in one reaction. However, if even just 10% of a one-pound bottle of propane exploded that essentially be equivalent to setting off a pound of TNT." Storing propane tanks below deck - Page 3 - SailNet Community




OK, so anyway, back to the generator:

I've been busy so haven't had much time to think about it, but my current thinking is stopped right about here --

1. I think definitely a low-tech solution using a small regular marine propulsion engine, maybe 20hp, with a jackshaft PTO (properly designed by a real engineer, and professionally built), and twin school bus alternators is clearly preferable to a regular generator, for my specific purposes. The advantages are just huge in terms of serviceability in remote areas, ability to repair any possible problem yourself, possibility of carrying complete spares, etc. If I could think of something else useful to do with the PTO, this solution would be even better, but I'm drawing blanks so far. With all the electrical power on board it hardly makes any sense to drive watermaker or bilge pumps or refrigeration this way.

2. Getting propulsion from this small engine besides power is tempting, but is probably a bridge too far. I have been convinced by people's comments on here that I don't want a saildrive hanging out of the bottom not behind the keel -- too vulnerable. A retractable shaft and prop a la Volvo 60 would be the very t*ts, but is going to be too expensive to justify I think.

3. Complex hybrid systems with either electric or hydraulic drives go against the KISS principle of these systems, so I won't go there.

4. Ergo, I will give up on redundant mechanical propulsion and just concentrate on making the main engine and drive as robust and reliable as possible, with an excellent spares inventory on board, and count on sails in the unlikely event the SHTF with the main engine. A key issue ensuring reliability of main power plant is fuel. So a really good solution here with a day tank, polishing, sumps in the tanks, excellent filtration, will go a long way.

5. Because all of these issues are elegantly and automatically solved in catamarans, it's maybe worth one more look at something like a Chris White Atlantic 57' cat, instead of a custom mono. This has two more very profound advantages of being faster, and being much cheaper, than the custom mono I have in mind. A few downsides, but every decision where boats are concerned involves some downside or another.

6. Solar power is so attractive for so many different reasons, maybe worth trying again to find some low-windage way to have at least some solar power. Maybe flexible panels built into the coachroof, for example.
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