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· Mermaid Hunter
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i have read a lot of threads about stoves on boats. of course, the usual debate is alcohol or propane.

<snip>

that was a real piece of reality for me. no propane on my boat!
There are only so many options.

People all over the world, ashore and afloat, cook on propane or butane. There are maintenance requirements as for so many other systems but they aren't onerous. Propane all in all is pretty safe.

Alcohol has two big issues - the flame is very difficult to see and the energy content is low. The latter means extended cooking times.

Kerosene has odor issues if combustion isn't well managed and the appliance choices are limited. For most you'll have heat issues - fine in northern latitudes, not so great in the tropics.

Electrical heat - resistance or inductive has a growing following but you are completely dependent on your generator running for every meal.
 

· Mermaid Hunter
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Units are important. There are a couple of people on this thread with near saintly patience. Kudos to Puddin' Tain and GeorgeB who have been getting it right.

Units are important. If you are using units like amps/hr (or /min or /sec) you don't understand. If you use amps to measure power (W, kW) or energy (Ws, Wh, kWh, or (unfortunately since it adds voltage dependance) Ah) you don't understand. Carry the unit terms through your calculations and you'll see you the error of your ways. This is Jr High School algebra and you should understand it.

I don't intend to offend anyone directly. I hope to help you understand just how important this material is, and that if you get the units straight you will be an electrical rock star.

anonymous said:
If a microwave is used sparingly, as they nearly always are, the DC amp usage is pretty low. An inverter is needed. But your 1200 watt example need not be that high. A small microwave at 700 watts AC will use about 70 amps DC through the inverter. 5 minutes of use to heat something up or make popcorn or whatever will use 70 divided by 12 or a bit less than 6 amps DC.
This is a great example. Lets walk through it.

First remember that watts are a measure of power that is NOT voltage dependent. That makes them great for dealing with voltage conversions that happen at inverters or battery chargers. Let's use my little Tappan microwave instead of the undefined one above. It is sold as a 600W microwave because that is the output of the microwave transmitter in the oven. If you read the label on the back you'll see it draws a maximum of 850 watts; the difference is due to the efficiency of the transmitter, losses in the power supply, and the control board, clock, etc. So we use 850 watts.

Actual RMS AC voltage (what you read on a volt meter) for US spec appliances should be between 117 and 120 VAC at 60 Hz (Hertz is just the frequency of the alternating cycle (AC) power). Let's use 120 to keep things simple.

850 watts (volt·amperes neglecting power factor which isn't relevant until we talk about refrigerators, air conditioners, or other device with significant rotating loads) / 120 volts = 7 amps ON THE AC CIRCUIT supplied by the inverter. We'll go back to watts to work our way through the voltage conversion in the inverter since it is voltage independent. My Mastervolt 2kW inverter has an efficiency of 95% - actually pretty decent. 850 watts on the AC side turns into 850 watts/0.95 = 895 watts on the DC side. If my batteries are fully charged and providing 13.6 VDC the microwave will draw 895 watts / 13.6 V = 66 amps. That's a lot of amps. If I heat up a casserole for 8 minutes I'll use 66 amps * 8 minutes / 60 minutes/hr = 8.8 Ah from my 675 Ah battery bank, about 1.3% of capacity. Not bad at all.

Lets look at a spaghetti dinner on an induction cooktop. Assume 3 minutes at 1500 watts to boil the pasta water and 11 minutes to cook the pasta at a lower setting - say 600 watts. We also heat canned spaghetti sauce (I'm making this simple so we don't have to saute meat and mirepoix, and sauce and paste, yadayadayada) at about 300 watts for the same total time.

3 min * 1500 W + 11 min * 600 W + 14 min * 300 W = 15300 W·min (aren't watts wonderful?)
Through the inverter 15300 W·min/.95 efficiency = 16105 W·min
Again with fully charged batteries that means 16105 W·min / 13.6 V / 60 min/hr = 20 Ah
Not the end of the world, but that does mean that if spaghetti is representative of a cooked meal and you make two a day aboard and that if refrigeration draws about the same 20 Ah you could cook with propane and have two big refrigerators and a separate freezer and come out ahead. If that's a good trade-off for you, fine - just make the decision with your eyes open and don't kid yourself that there is some magic efficiency changing the rules of physics.

Now one watt is roughly 3.4 BTUs, so a 1500 W induction hob is equivalent to a 5100 BTU propane stove burner. It can't be different. Force 10 and Eno propane cookers (for example) have large burners that run between 8000 and 8500 BTUs. The smaller burners hover around 3400 BTU. So in our spaghetti example above, the propane stove will boil the water faster than the induction hob, but that only reduces the initial 3 minutes. It isn't relevant to heating the sauce or cooking the pasta at reduced heat.

In fairness, most propane cookers have an electrical solenoid in the propane locker that draws a surprising amount of power. Many draw about 1 A the entire time they are switched on. So our spaghetti dinner on a propane cooker consumes 14 min * 1 A / 60 min/hr = 0.23 Ah. Not much, but it should be counted.

All the efficiency claims of induction are relative to electrical resistance heating, not gas.

Exercise: look up and understand current (amps), power (W), and energy (Wh, Ah, BTU).

In my opinion (all the above is fact - this is opinion) propane is the best choice for cooking aboard although it does carry some small risk. If you use a gas powered generator like the Honda to top up your batteries to support electric cooking the risk is similar. If you use a diesel generator, a diesel main, or alternative energy the risk is slightly higher for propane.

If you are so concerned with the explosive potential of propane as to rule it out you can make inductive cooking work but your battery bank better be big (off hand, 1200 Ah or so) and you should have the charging capacity to match unless you eat out a lot.
 

· Mermaid Hunter
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So what I've gathered is that, done right, propane and alcohol are both very safe. The danger of a fire or explosion from either of them is a small fraction of the other dangers involved in boating.

But for a person with a small boat who is trying to keep systems simple and costs down it sure sounds like alcohol comes out a winner. Two or three hundred bucks for an Origo and you're done. No solenoids, no hoses, no valves...

At least that's how I'm leaning for cooking in my tiny boat.
I spent a wonderful summer with a girl friend on a Catalina 22 pop-top. We had an unpressurized alcohol stove. The only frustration was how long it took for coffee in the morning. The extra time for everything else could be planned into our day. We did spend a lot on stove fuel.

Propane is a lot more available - more of an issue for sustained periods aboard without ground transportation than weekends...

actually, if you couldn't cook spagetti, it wouldn't effect me a bit.
Spaghetti was just an arbitrary example. Pick another decent meal and I'll run numbers. If you really live on Ramen noodles none of it makes much difference. Down that path lies the discussion of "does boating have to be camping."

The point of my post was not spaghetti but that there are a lot of incorrect calculations in this thread and that getting your units right will make it apparent whether one understands reality or not.
 

· Mermaid Hunter
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Sounds like a great summer!
It was. I cherish those memories still.

Does it really take that much longer? Origo claims 7000 BTU, and I just looked up my home Frigidaire gas range and it say 9500 BTU for the standard burners (not counting my favorite burner, the Power Plus 17000 BTU), so by those numbers it should only take about a third longer to reach boiling. Doesn't seem like a big deal.

My butane camping stove is also 7000 BTU and for some reason it seems faster that the regular burners on my home range. Maybe my patience is better when I'm in the great outdoors :)
What I remember is 15 minutes or so to the start of perking and then 10 to 12 minutes to the right color in the glass knob. On my current propane cooker with the same percolator it takes about five minutes to the beginning of perking and 8 minutes to coffee. 13 minutes compared to about 26 minutes is a difference.

I simply don't believe 7000 BTU for an alcohol burner. I don't see how the heat of combustion supports that. Admittedly I haven't run numbers. If you can point me to specs I'll follow up with the manufacturer and see if they'll support side-by-side test.

The difference between butane and propane is only of interest in very cold weather. Otherwise it's the same stuff.
 

· Mermaid Hunter
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Here's what I was going by: Origo 3000 & 1500 Alcohol Stoves

I'll probably be picking one up this summer. If I do, I'll do a side-by-side with my home range and my camping stove and post the results here.
Interesting. They do say 7000 BTU and claim 10 minutes to boil a quart of water. West Marine advertises the same product with 5000 BTU which gets into the 15(ish) minute range of my experience. I have no explanation, only my observations. Your proposed side-by-side comparison would be useful. Be sure to use the same amount of water, the same pots, the same ambient temperature, and the same measurements.
 

· Mermaid Hunter
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might be a really great idea to research cooking fuels in the locales you plan on cruising so you can figure out what kind of cooking you want to do on board at sea in a seaway and at anchor in bumpy and in smooth anchorages before committing self to anything.
there are many miles between the dream stage and inside usa cruising and out in the world of omygodswhatami gonna cook with., there isnt alcohol nor cng in mexico..nor kerosene... omy now what me gonna do as i refused to use propane on board ,..yada yada yada.....(as well as refused to listen to that crazy ***** who is actually out in mexico cruising and seeking items friends request....)
friends of mine live in mexico in houses. they have lived here longer than have i, and they let me know what is not available here for citizens and turistas and other non military folks.
I think you are misinformed.

Also, you tell people to do research and then beat them up for doing it and finding that what you say does not seem to be true. Our own brand of academic peer review, if you will.

Oh - I'm not in Mexico either. It has been a while since I was there but I'm pretty sure I would have noticed if they had regulated availability of something as fundamental as kerosene.

You should be able to find petróleo in hardware stores. With a little work you can likely find an airport that will sell you Jet A-1. Unlikely to find it in service stations. It would take work to source but it should be possible.

Propane is the best choice of cooking fuel for cruisers today in my opinion.
 
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