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Old 26-01-2016, 07:07   #241
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Re: Ideal Generator?

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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.
I'm having difficulty following the logic of this post --

"Even the Royal Navy . . makes mistakes, they are not infallible."

But that is exactly my point. Are you infallible? Never make mistakes? Better than the Royal Navy? Hmmm.


"But, don't try to convince others that the risk is higher than actual statistics prove."

Since there are zero statistics available, at least that anyone here has been able to find, I'm not trying to convince anyone, that the risks are higher than these non-existent statistics show.

What I have shown is that the risks are not trivial, are not insignificant, and that catastrophic propane explosions are not extremely rare.


Anyone who is convinced that "it can never happen to me; it only happens to idiots" is of course welcome to that point of view.

Nor am I arguing that everyone should rip out their propane systems. I am only arguing that complacency concerning propane on board is a very bad mistake.
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Old 26-01-2016, 07:36   #242
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Re: Ideal Generator?

As this formerly interesting thread has devolved to a propane vs induction argument, it is hereby unsubscribed...
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Old 26-01-2016, 08:06   #243
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Re: Ideal Generator?

You know really, when you get to looking at systems, a Cat has some distinct advantages.
The twin hulls have of course twin rudders, and is dead easy to run independent autopilots, of course independent engines is another point, probably easy to run independent fuel tanks if they aren't already with a cross feed and or fuel transfer pump.
You can more easily mount a massive Solar array.

I have no Cat experience, guess though the downside is they don't like to be loaded down like a cargo ship? And I'm guessing again, but would assume harder to heat in high Latitudes? Heating can of course be overcome.
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Old 26-01-2016, 08:28   #244
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Re: Ideal Generator?

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You know really, when you get to looking at systems, a Cat has some distinct advantages.
The twin hulls have of course twin rudders, and is dead easy to run independent autopilots, of course independent engines is another point, probably easy to run independent fuel tanks if they aren't already with a cross feed and or fuel transfer pump.
You can more easily mount a massive Solar array.

I have no Cat experience, guess though the downside is they don't like to be loaded down like a cargo ship? And I'm guessing again, but would assume harder to heat in high Latitudes? Heating can of course be overcome.
Oh, great! Now we've just finished with induction vs propane, and now cats vs monos!! :nono:

As we know, it's a very, very complicated, and inflammatory question.

Yes, what you mention are clearly disadvantages of cats which no one can deny. But I think these are not fatal. Heating is fairly trivial (more heat and better insulation), and loading -- well, you don't take as much crap, and you make sure the cat is big enough to carry the essential load -- I think that's manageable.

The advantages you mention are also real and very important, neatly solving all the problems discussed in this thread. I know I'm opening a can of worms here (to say the least), but I will continue:


Add to everything above, cats don't have ballast, so skim over the top of the water (if you don't overload them), and so are more easily driven, for better motoring as well as easier sailing. Much less likely to sink. Huge pluses.

Downside for my kind of use, and in my purely subjective opinion, is that I am a bit afraid of some aspects of them in heavy weather -- gusts aren't absorbed by heeling, and there is a very small risk, but a not trivial risk, of capsizing, something irrelevant in moderate latitudes, but of possibly more concern at high latitudes. Even at the latitudes I sail now (up to over 60N), cats are very, very rare, and one reason probably is the very stiff weather and sea states we get up here. I guess this is somehow manageable, but based on my limited experience at least, I just can't even imagine doing my last North Sea crossing on any kind of a cat, and I do really need the capability of operating in such conditions with confidence and safety. So this is an open question.

Then another downside for my particular use is relative fragility of the necessarily light construction of decent performing cats -- I didn't even want a plastic boat at all, but a stoutly built metal one, so I worry about ice and so forth in a cat.

A possible downside, but maybe just a question of getting used to it, is the motion, which I found disturbing during my admittedly limited miles on cats.

A huge upside of cats like the Chris White Atlantic cat, and of the Catana recently discussed, and probably of many other cats, is the excellent inside helm position and splendid view -- a pilothouse is on my must have specification list in any case. I know of no mono, which has a "pilothouse" like the A57 has.


It is possible that I might buy something like an Atlantic 57 and just see if I like it for a year or two, while designing the metal mono in parallel. That could work nicely since the design process will easily take two years anyway. If I really like it and feel comfortable, then I just wouldn't build the mono. Otherwise, sell the cat when the mono is completed.


All of this is still idle theory at the moment, since I don't have the money for either of these things yet, but I expect that part will be solved by this time next year, which is why I'm thinking about it now.
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Old 26-01-2016, 09:15   #245
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Re: Ideal Generator?

All this has got me thinking about other ways of generating power from the main engines if possible, and whether you can do anything else interesting at the same time.

Some rather fun technology I stumbled over a few years ago (but was never able to make use of - the application I had in mind for it never worked out) is a magnetic gearbox - essentially it's a planetary gearbox which uses permanent magnetic fields instead of gears, and so is contactless and lubricant/maintenance free.
What the company which make them have done more recently is come out with a version which has a variable gear ratio for speed but constant torque ratio across the gearbox (the difference being made up by putting power into the electric part of the machine or taking it out of it).

That has obvious attractions as a reduction gearbox for any boat in that you get far better matching of the propeller power to motor power. The graph below is a very quick fag-packet calculation of what you'd get for a Yanmar 4JH45 with one of these gearboxes, essentially making perfect matching possible whenever the propeller power demand goes above the power available at idle on the engine.

What is more interesting is the possibility to use this as both a reduction gearbox AND a generator at the same time, and on this one I'm still scratching my head a little to see if it would work. Unlike a car, a propeller shaft will always experience peak torque at peak speed - and such a setup will always be closest to it's torque limits when the propeller is absorbing the maximum power. I **THINK** if the engine is under-loaded this device could extract power and thus operate like a generator (i.e. in the example case below wherever the engine is operating at less than 2000 RPM it could also be used as a generator), but I'm really not sure about that. If my understanding is correct, it should also be possible to cut down the reduction ratio a bit and then use the excess power available from the engine for generation.

Two other nice aspects - in the event of a complete failure of the electrical systems the unit will revert to being a simple fixed-ratio gearbox (presumably set to be at the same ratio as the standard reduction gearbox currently sold by the engine manufacturer), and if I understand it correctly with the diesel engine stationary and braked it can also be used as a fairly low-power electric motor. So in essence it's a fail-safe parallel hybrid system which can draw power from the engine when motoring.
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Old 26-01-2016, 09:31   #246
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Re: Ideal Generator?

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Originally Posted by pdf27 View Post
All this has got me thinking about other ways of generating power from the main engines if possible, and whether you can do anything else interesting at the same time.

Some rather fun technology I stumbled over a few years ago (but was never able to make use of - the application I had in mind for it never worked out) is a magnetic gearbox - essentially it's a planetary gearbox which uses permanent magnetic fields instead of gears, and so is contactless and lubricant/maintenance free.
What the company which make them have done more recently is come out with a version which has a variable gear ratio for speed but constant torque ratio across the gearbox (the difference being made up by putting power into the electric part of the machine or taking it out of it).

That has obvious attractions as a reduction gearbox for any boat in that you get far better matching of the propeller power to motor power. The graph below is a very quick fag-packet calculation of what you'd get for a Yanmar 4JH45 with one of these gearboxes, essentially making perfect matching possible whenever the propeller power demand goes above the power available at idle on the engine.

What is more interesting is the possibility to use this as both a reduction gearbox AND a generator at the same time, and on this one I'm still scratching my head a little to see if it would work. Unlike a car, a propeller shaft will always experience peak torque at peak speed - and such a setup will always be closest to it's torque limits when the propeller is absorbing the maximum power. I **THINK** if the engine is under-loaded this device could extract power and thus operate like a generator (i.e. in the example case below wherever the engine is operating at less than 2000 RPM it could also be used as a generator), but I'm really not sure about that. If my understanding is correct, it should also be possible to cut down the reduction ratio a bit and then use the excess power available from the engine for generation.

Two other nice aspects - in the event of a complete failure of the electrical systems the unit will revert to being a simple fixed-ratio gearbox (presumably set to be at the same ratio as the standard reduction gearbox currently sold by the engine manufacturer), and if I understand it correctly with the diesel engine stationary and braked it can also be used as a fairly low-power electric motor. So in essence it's a fail-safe parallel hybrid system which can draw power from the engine when motoring.
Absolutely fascinating and totally cool. Thanks very much for that. That could be revolutionary. Query how long it will take to develop, however.
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Old 26-01-2016, 09:38   #247
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Re: Ideal Generator?

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Absolutely fascinating and totally cool. Thanks very much for that. That could be revolutionary. Query how long it will take to develop, however.
I think it's more of an issue that at the moment it's a solution looking for a problem - you can do all the same things with conventional technology which is fully developed and in mass production by automotive suppliers at the moment, and wind turbines also have solutions which work. This could work very nicely in both of those applications and indeed is being trialled for them, but is in competition with a lot of other ways of doing the same thing and has some fairly major knock-on effects on other aspects of the design.
What it needs is a company with deep pockets and a certain amount of bravery to place a contract with them to develop it and start selling it en-masse in one of their market areas. Until then it's a brilliant idea that may never take off.
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Old 26-01-2016, 09:50   #248
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Re: Ideal Generator?

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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.

You might want to have a conversation with Chris White about all the cruising goodies that you carry on your boat. I have always liked how you seem to have every cool thing imaginable on your current boat. Unless I am mistaken, that adds up to a lot of extra weight.

My brother had a conversation with Mr. White while sailing aboard a new Atlantic 57. When talking about boat speed Mr. White had made mention that several A57 owners complained that they never have achieved the speed the boat was supposed to be capable of. When he investigated all of these complaints, he found the boats to be loaded with so much cruising gear, they sat too low in the water to ever reach the speed potential of the boat. I may be wrong on this, but I think he said there should be no more than 1500 lbs over its designed weight or speed will suffer a big hit. (Ask Mr. White about this to be sure, I was told this story several years ago and may not be clear on the facts)

Just something to think about if speed is one of your determining factors of going this route.
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Old 26-01-2016, 09:50   #249
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Re: Ideal Generator?

Look up Toyota's PSD or power split device, it is the Prius "transmission" I put that in parenthesis as there are no "gears", no reverse, no neutral etc.
Fascinating to me, but it has the capability of generating quite a lot of electrical power and "split" the engine output in proportion to generating power or providing propulsion, or both and of course as it's a motor / generator it would provide electric propulsion.

BTW, I wasn't saying twin rudders etc were a weak link of a Cat, rather I think of it as redundancy as I assume if you lost a rudder, you can carry on on one.
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Old 26-01-2016, 10:03   #250
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Re: Ideal Generator?

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Look up Toyota's PSD or power split device, it is the Prius "transmission" I put that in parenthesis as there are no "gears", no reverse, no neutral etc.
Fascinating to me, but it has the capability of generating quite a lot of electrical power and "split" the engine output in proportion to generating power or providing propulsion, or both and of course as it's a motor / generator it would provide electric propulsion.
Conceptually that's the same as the Magnomatics device, with the difference that the Toyota uses a mechanical planetary gearbox while the Magnomatics one uses a magnetic one, and hence can combine the variable gear ratio and the motor/generator into a single device. In theory at least that should make it cheaper and more robust while being smaller/lighter and needing less maintenance.
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Old 26-01-2016, 10:07   #251
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Re: Ideal Generator?

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I'm having difficulty following the logic of this post --

"Even the Royal Navy . . makes mistakes, they are not infallible."

But that is exactly my point. Are you infallible? Never make mistakes? Better than the Royal Navy? Hmmm.
You presented the Royal Navy as the epitome of good practices and procedures, yet even they can't control the propane beast, hence everyone is in danger.

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...
But there was a terrible gas explosion some years ago in Poole Harbour on board a Royal Navy training yacht using the absolute best possible practices. The cadets even pumped out the dry bilges with a manual bilge pump as an extra precaution to get any lingering gas out (anyone on here do that?). A cadet lost a leg (IIRC).

So it is impossible to make a gas system on a boat 100% safe.
My point is that obviously the Royal Navy isn't actually "using the absolute best possible practices". If they had, there would not have been a loose connection and leaking locker.

And no, I don't proclaim to be infallible. But I do tighten and check the connection to my propane tank when I change it. And, since my gas locker is vented under the bridge deck, like others have mentioned, any locker leak will simply dissipate, hence testing it is lower on my routine maintenance list.

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"But, don't try to convince others that the risk is higher than actual statistics prove."

Since there are zero statistics available, at least that anyone here has been able to find, I'm not trying to convince anyone, that the risks are higher than these non-existent statistics show.

What I have shown is that the risks are not trivial, are not insignificant, and that catastrophic propane explosions are not extremely rare.


Anyone who is convinced that "it can never happen to me; it only happens to idiots" is of course welcome to that point of view.

Nor am I arguing that everyone should rip out their propane systems. I am only arguing that complacency concerning propane on board is a very bad mistake.
It's your choice to discount the BoatUS statistics I presented as not including propane explosions, it makes sense for you to do so as it bolsters your argument. I happen to believe the BoatUS statistics presented do include fires caused by propane explosions, as the whole purpose of the article is to make the reader aware of fire dangers on boats. Maybe the risk of propane explosion is much higher on boats than presented by the BoatUS statistics. Maybe those explosions happen more on boats that are not insured, hence wouldn't be captured in any insurance statistics. Maybe the risk is higher in the UK.
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Old 26-01-2016, 11:03   #252
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Re: Ideal Generator?

The conversation comparing risks of propane keeps referencing risks associated with electrical systems. The op is going to eliminate one of those risks. The folks that say there is as much or more risk from electrical systems have a point. However no one has suggested a practical way to eliminate that risk. Control or mitigate yes, but not eliminate . Few of us would be willing to voyage on a boat sans electrons..... One would be hard pressed to say that adding an induction cook top would increase the risk of electrical fire by any measurable amount. Eliminating propane would obviously reduce the risk of a propane fire/explosion to 0%. It would also reduce the risk of being burned by the cooking devise significantly.
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Old 26-01-2016, 11:11   #253
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Re: Ideal Generator?

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You might want to have a conversation with Chris White about all the cruising goodies that you carry on your boat. I have always liked how you seem to have every cool thing imaginable on your current boat. Unless I am mistaken, that adds up to a lot of extra weight.

My brother had a conversation with Mr. White while sailing aboard a new Atlantic 57. When talking about boat speed Mr. White had made mention that several A57 owners complained that they never have achieved the speed the boat was supposed to be capable of. When he investigated all of these complaints, he found the boats to be loaded with so much cruising gear, they sat too low in the water to ever reach the speed potential of the boat. I may be wrong on this, but I think he said there should be no more than 1500 lbs over its designed weight or speed will suffer a big hit. (Ask Mr. White about this to be sure, I was told this story several years ago and may not be clear on the facts)

Just something to think about if speed is one of your determining factors of going this route.
Thanks for that. Although I am not a cat sailor, I am quite aware of these issues, and if I do decide to take this walk on the dark side, I will be sure to weigh every item of gear which goes on board, and give up anything unnecessary. I think this just goes with the territory, if you want to sail a cat and you want it to perform well.

I will not need a separate generator, which will save at least a quarter ton right there. Other things will be hard decisions, but I think 1500 lbs should be doable. A big difference from the at least 3 tons of stuff I have on my present boat for sure.
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Old 26-01-2016, 11:13   #254
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Re: Ideal Generator?

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. . BTW, I wasn't saying twin rudders etc were a weak link of a Cat, rather I think of it as redundancy as I assume if you lost a rudder, you can carry on on one.
I agree.
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Old 26-01-2016, 11:37   #255
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Re: Ideal Generator?

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The conversation comparing risks of propane keeps referencing risks associated with electrical systems. The op is going to eliminate one of those risks. The folks that say there is as much or more risk from electrical systems have a point. However no one has suggested a practical way to eliminate that risk. Control or mitigate yes, but not eliminate . Few of us would be willing to voyage on a boat sans electrons..... One would be hard pressed to say that adding an induction cook top would increase the risk of electrical fire by any measurable amount. Eliminating propane would obviously reduce the risk of a propane fire/explosion to 0%. It would also reduce the risk of being burned by the cooking devise significantly.
Exaggeration of the risk, for the purposes of justifying, has been the only argument. The real justification is: "I don't want to put forth the work associated with carrying propane on my boat!" Which, btw, is a very reasonable justification, imo.
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