It appears that we must take a Whisperlite to Morocco as we cannot be sure of finding gas canisters in Marrakesh. When using gas we use about 30 grams per camp, using a heat exchanger pot. I would guess 40 grams with a standard pot. We have a maximum capacity of 1.2 litres for petrol. Can anyone hazard a guess as to whether that will last 15 camps. I can take either pot. We cycled in Morocco for a similar time several years ago with the same setup, with an ordinary pot. I know I bought more petrol at some intermediate point, that time. but I also remember giving a lot away to a taxi driver at the airport
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 1.2 lts of petrol weighs 1200gs, divide by 30, equals 40. Should be 40 camps. Divide by 40gs, equals 30. Therefore 30 camps. Should have more than enough petrol for the trip. You could get away with carrying 1/2 lt, but I'd carry 3/4 - 1 lt just to be sure. You don't want to run out in the middle of nowhere.
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use a stove that will run on parrafine/kerosene it's safer it costs less burns hoter than petrol so will go further downside is smell if it gets on cloths and pre-heating the stove. my stoves- optimus 199 and primus omnifuel never any problems if you clean and service as instructions after every trip.
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| Edited: 20/03/10 20:58 |
I've measured unleaded petrol and kerosene usage over 3 trips using a Whisperlite. For petrol, I get an average of 35 ml/1 L of water boiled, and for kero, about 30 ml/1 L water boiled. I prime with the same fuel, and use MSR Titan cookware.
That's all in developing countries, where fuel quality can be dodgy. MSR figures seem to suggest you should be able to boil 1 L of water with 23 ml of White Gas, and 18 ml kero. I've never got anywhere near that - partly because I do some simmering with evening meals (tho' rarely for longer than 5 mins).
I guess you could view this as a range, and multiply out your expected requirement for boiling water to find out how much fuel you need. There's also some serious stovies on this forum who probably have more accurate consumption figures. Hope you have fun on your trip!
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The only thing I can be sure of buying in Morocco is unleaded petrol. Thanks A C If I do not simmer and use 2.5 litres per camp I should get 15 camps from 1200ml. If I take my heat exchanger pot I should get to about 19 camps. That is comfortable and would allow some melting of snow for water.
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Sounds about right. Are you planning a circular route, or going in and out by the same route? If the latter, you could take an extra 0.5L in a coke bottle, and leave it in a cache around 5 days out. That would leave you a reserve in case of miscalculations or unforeseen snow melting, which uses a lot of fuel imo.
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Its a circular route. Until I know how things are going I will only melt snow as a last resort. I agree snow melting takes a lot of fuel, twice as much, or more if melting for the next days drinking too. A lot of this figure 30-35/litre figure will vary as to how efficiently I prime and how few separate burns I can bring it down to.
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 Parafin should be available locally, I have found that the less developed an area is the more parafin is used. I moved away from Parafin when it started getting a pain to buy it in the UK and europe, although it seems to be making a come back. My fuel of choice is aspen t4 much cheaper than coleman fuel and burns very clean. often available in garden shops as naptha as it runs chainsaws and leaf blowers. Perol is quite safe in use with a little care. Steve D
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 > 1.2 lts of petrol weighs 1200gs <pedant>
Petrol isn't water. It has a density somewhere between 0.71 and 0.77, depending on the blend. So 1.2l of petrol weighs between 850g and 920g.
</pedant> It's interesting to see reports of 30ml average petrol required to boil 1l, since that's not far off what is needed with a decent meths setup, and yet meths is less energy dense than petrol. I thought that, like the gases, it was twice as energy dense, but, having checked the figures, it's about 35% higher. Given that petrol and ethanol are of similar densities (as above, and 0.78 for ethanol), it's not so surprising that you need broadly similar amounts of meths and petrol.
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This is the table a chemistry teacher mate Ian produced some time ago. He wrote: "The attached spreadsheet shows data for a selection of fuels from propane
(Epigas etc) through heptane (probably what Coleman fuel is and also quite
similar to petrol) to decane(the smallest molecules likely to be found in
paraffin/kerosene). Kerosene is a term which covers the range of fuels with
molecules larger than petrol but smaller than diesel. Paraffin is also used
to describe some fuels within that range. The confusion around the names
turns out to be fairly irrelevant, once you calculate the heat output per
gram, since that varies very little across this range.
I threw data for Meths in just for interest!
None of the alkane fuels (all of them except Meths, which is an alcohol),
has any real adantage in terms of output per gram. You might like to
consider output per cubic centimetre as volume is also an important
consideration I presume. This analysis shows that the bigger molecules give
the advantage.
Since the paraffin or kerosene you buy would almost certainly have larger
molecules than decane, the advantage in terms of output per volume would be
even greater (more still if you use diesel)." The columns have got a bit mis-aligned, but it should make sense and give some indication of fuel values. Fuel Molar mass Molar heat of combustion/kJ Heat ouptut in kJ/gram Density g/cm3 Heat output in kJ/cm3 Propane 44 2220 50 0.582 29 Pentane 72 3509 49 0.626 31 Heptane 100 4853 49 0.684 33 Decane 142 6778 48 0.73 35 Meths 46 1367 30 0.79 23
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That's not at all how it looked before I submitted it! I hope you can make sense of it...
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Those figures are failry close to those I calculated from bond enthalpies a while back (quoted figures online and in the various reference books vary quite a bit). However, being a chemist, rather than an engineer, I suspect he's done a 'perfect chemical energetics' calculation. Rather than use the combustion energy (which assumes all the energy released in the burn is available), the better figure is the Lower Heating Value, which excludes the energy lost to vapourise the fuel, and by the water vapour that's created in the burn; this can only be recovered by a condensing boiler. ;-) The other issue is the 'friendliness' of the various fuels for handling purposes. Whilst the higher fractions such as kerosene and paraffin have higher energy contents, they're quite unpleasant when spilled, as they don't evaporate, and leave oily residues behind. Meths leaves only a small purple stain behind, and nothing if you can find stuff without a colouring. The point about energy density per gramme is well made. This spreadsheet is a pretty useful list of LHVs for different fuels.
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 This is the table that didn't format well above.
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| Edited: 23/03/10 19:41 |
All these tables, etc. are all well and good, (even though I have trouble understanding them, not being a chemist, etc,), but still doesn't tell OP how much fuel they need for trip!!! Or what's the best to use.
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| Edited: 23/03/10 20:52 |
I can't answer the OP's Q but can explain the above table. If you take the molar mass as grams then the 3rd column says how much energy for that amount. the 4th how much energy per gram. Density is a decimal (relative to water) (being 1) so 100ml times by the decimal will weight that many grams for reference 100ml of water weighs 100g (don't get into weight being newtons please) and the final column I dare say isn't very useful for a gas as it'd be pressurised anyway so take up less room so I don't know what that's about. Hope that helps a bit and someone will be along in a bit to help the OP. I could suggest using petrol with your stove from now until your expedition to get the used to it and a better idea how much you will need?
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Interesting tables but I think Apple Crumble's real experiential data is the most reliable. The difference between the propane/butane I am used to and the "heptane approximation" I will be forced to burn is: that gas lights without priming and without a fireball and I know I can cook in the porch of our Laser, 30 grams will boil about 3 litres with a heat exchange pot Petrol takes extra fuel everytime you light up which burns inefficiently, and dangerously. I would not like to start a petrol burn in my Laser porch. I am hoping to boil 3 litres with 75 grams of petrol with a heat exchange pot. I have heard it said that heat exchange pots cope more efficiently with less controllable stoves. With ordinary pots a lot of heat just escapes up the sides. The table makes it sound as if 75 grams per camp will be easy. AC's experience shows that it will not be easy. The heat exchange pot and delicate and few primings will be my only chances. I do cross the Tizi 'n Test pass on day 8/9 if I am short of fuel I will know and we will have to stop cars and siphon petrol out of their tanks in exchange for lucre or hitch to a petrol station.
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Derek, you may well do better than me, particularly if you're only boiling water - as I said, I simmer a bit. I think it would be wise to regard the MSR figures (on their website) as the lower range, and mine as an upper range. Priming is a bit of a pain, but I don't think its that wasteful of fuel. You only need maybe 1-2 ml to prime - too much leads to the dreaded fireball, as I'm sure you're aware. Does your Whisperlite have a fibreglass wick in the priming pan? This helps a lot, and its worth either making one up,or buying a Whisperlite maintenance kit, which I believe includes one. Sounds like petrol may be your only option, which is a shame - not only do the additives constitute a health hazard, but its very flammable in the event of an inadvertant leak. I'm always a bit leery, and avoid it if I can. You've clearly done your research, I take it kero/paraffin is a no-go? Will you be leaving some gear in a town at the start of the route, then returning to it? If so, it could be worth taking along your gas burner as well - you may get lucky and find some canisters. If not, you can just dump the gas burner with the rest of your gear while you're walking. On a similar note, and if allowed, you may be able to eek out your fuel at some stages of the walk by lighting small fires for cooking - with the usual caveats about low/no impact camping. I'd be interested in comparing notes on your fuel usage when you get back - more information is always good. Happy hiking! Edited to add - I think the heat exchanger is a good idea, a lot of heat is lost around the side of the pot with the supplied windshield. I've wondered if Capt P's Caldera Cone type set-up could be used to good effect - I guess it would be lighter (and more adaptable?). Not sure if anyone has tried this.
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| Edited: 24/03/10 00:12 |
We arrive at Marrakesh airport and have to get a bus out to Amezmiz,hopefully the same day. We return by bus from another town, then might have some time in Marrakesh. I am trying to avoid the scenario of a gear dump in Marrakesh. Iam sure paraffin is available somewhere. I do not want to spend time looking for it or gas canisters really. If we have to store something for another reason we could do it near the airport. There is more likely to be a stone left unturned out by the airport I imagine.
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> I've wondered if Capt P's Caldera Cone type set-up <cough> Trail Designs' Caldera Cone setup </cough> For a petrol stove, I'd suggest a Ti version. I'd also want to play with the inlet and exhaust holes, and make them bigger to cope with the higher air demand of the more energy-dense and higher power fuel; a petrol stove at full whack pumps out a hell of lot more power than a meths burner (my Sigg Fire Jet happily glows orange to yellow when running flat out).
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> There is more likely to be a stone left unturned out by the airport I imagine. You might attract unwanted attention if you start concealing things near airports...
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