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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> RC Fuels >> A fuel experiment
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A fuel experiment - 10/16/2003 11:36:37 PM   
Jim Thomerson



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Joined: 10/9/2002
From: Austin, TX, USA
Status: offline 		Ok, We have a plastic gallon jug of fuel, 80% methanol, 20% oil. It is half full. It is left uncapped for 30 minutes at 80 degrees F, 70% relative humidity, 5 mph breeze. How much water does the fuel absorb? How much of the methanol evaporates? No BS replies please.

Jim

< Message edited by hobbsy -- 10/17/2003 3:45:38 AM >
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RE: A fuel experiment - 10/17/2003 1:42:38 AM   
Hobbsy



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Joined: 12/2/2001
From: Colonial Beach, VA, USA
Status: offline 		Is that calculable?

< Message edited by hobbsy -- 10/17/2003 3:45:56 AM >

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RE: A fuel experiment - 10/17/2003 3:08:10 AM   
Jim Thomerson



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Joined: 10/9/2002
From: Austin, TX, USA
Status: offline 		Not by me, who doesn't always spell so well either. However, one can hope that in this modern age of science and technology someone might have a clue; something better than arm waving and urban legend.

Jim

< Message edited by hobbsy -- 10/17/2003 3:46:17 AM >

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RE: A fuel experiment - 10/17/2003 12:12:22 PM   
Ross Kean



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Joined: 6/4/2002
From: Fredericton, NB, CANADA
Status: offline 		It can't be calculated because there is no way to measure the exchange rate of the moisture-laden air above the surface of the fuel. The exchange rate of air, the available surface area, the rate of methanol evaporation and a host of other factors makes this calculation essentially impossible. Having said this, I would seriously doubt that there would be enough absorbed moisture to have any serious effect on the fuel in 30 minutes! Perhaps if you were actively bubbling the air through the fuel at several litres per minute you might have a problem!

Ross

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RE: A fuel experiment - 10/17/2003 3:33:23 PM   
Sport_Pilot



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From: Acworth, GA, USA
Status: offline 		The evaporation rate can be calculated, not sure about the breeze effect, I would think the jug would have to be tilted toward the breeze. I no longer have tables for methyl alcohol but I do recall the boiling point at 14.7 PSI to be only 148 degrees or so. So I suspect the evaporation rate to exceed the effect of the breeze, so that without turbulence their would be no substantial amount of air getting in. Methanol evaporates rather quickly at that temperature so the main problem would be decreasing the amount of methanol causing the percentage of oil and nitro to increase. Now if you left it uncapped for a length of time in a cool area, allowing the vapors to condense and contract with little evaporation then moisture could be a big problem.

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RE: A fuel experiment - 10/17/2003 3:37:03 PM   
David Cutler



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Joined: 9/13/2002
From: Los Angeles, CA, USA
Status: offline 		I would have thought one click more throttle would have a thousand times the effect on the engine revs than 30 minutes of fuel exposure to the air on your jug.

I really wouldn't worry about it. there are much better things to worry about.

-David C.

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RE: A fuel experiment - 10/17/2003 6:25:25 PM   
Jim_McIntyre



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quote:

How much water does the fuel absorb? How much of the methanol evaporates?


I prefer practical tests to theoretical calculations, too many variables to account for.

I'm no chemist but wouldn't some specific gravity device (hygrometer?) give you the delta in alcohol content?

As for water content, pour the contents in a container with a larger neck, stick it in the freezer for a few hours, scoop out the ice, transfer it to a measuring cup and thaw... of course you would have to know the water content prior to the test... so you could perform this twice (before and after).

< Message edited by Jim_McIntyre -- 10/17/2003 1:26:28 PM >

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RE: A fuel experiment - 10/17/2003 7:36:45 PM   
Sport_Pilot



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quote:

I'm no chemist but wouldn't some specific gravity device (hygrometer?)


The drag racers use a hygrometer to determine the ratio of nitro to alcohol, but with oil and several differant weights of oils its impossible to tell with a hygrometer.

Not sure I understand your test, but methanol is used as a gas deicer as well as a windshield washer antifreeze. That is it will mix with water and prevent the water from freezing.

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RE: A fuel experiment - 10/17/2003 11:12:25 PM   
Jim Thomerson



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Joined: 10/9/2002
From: Austin, TX, USA
Status: offline 		Maybe we just set the jug on a scale, and see if it gains weight from absorbed water or looses weight due to methanol evaporation. Or maybe it will just sit there defying us.

Jim

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RE: A fuel experiment - 10/18/2003 2:28:12 AM   
w8ye



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From: Taylortown, OH, USA
Status: offline 		The Methanol would only be 99% pure to begin with and the remainder being mostly water.

Enjoy,

Jim

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RE: A fuel experiment - 10/19/2003 8:30:09 PM   
Mr.B


 

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Joined: 10/15/2003
From: HBG, SWEDEN
Status: offline 		On top of that, aint Nitro about 50% water?
B!

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RE: A fuel experiment - 10/21/2003 6:54:56 PM   
yard-dart



Posts: 927
Joined: 3/6/2002
From: West Monroe, LA, USA
Status: offline 		SOLUTION! Don't leave tha cap off of your jug and you won't have to worry about it.

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