Mixing Fuel

[Allen Eshleman]

I have read here about some people mixing fuels.  For example, some mix 10% nitro and 5% nitro fuels of the same brand, I presume, to get 7.5% nitro fuels.   Some mix in extra castor.

In mixing fuels effectively:   are they stirred or shook or both or just poured together?  Is there a danger that you end of with different consistencies of fuel in the same container?

Is there a problem with pouring the last ounce or so of one container into the next one?

   

[Garf]

I mix my own fuel from scratch. The main thing is always keep containers capped when possible, and filter fuel between flying sessions.

[Steve Helmick]

I've mixed my own, years ago. The first rule is to mix oil(s) and alcohol together first, and then add the nitro last. It mixes better that way. I think I probably put the small percentage ingredients in last (propylene oxide, nitro benzine, amyl acetate, etc.). My measuring tools were a quart sized Pyrex pitcher and a 10cc graduated cylinder. I think I made about 1 quart at a time, pouring the measured ingredients into a gallon can, then shaking it gently, and decanting into pint cans or later, high quality quart plastic bottles.

About 4 years ago, I mixed up some fuel for Gary Gingerich's Yatsenko .76, which he used at two different NW CL Regionals, over the course of 3 years. He was very happy with the fuel. Just used the quart pitcher...don't tell my wife! That pitcher eventually (somehow!) got a chip on the spout area, and we replaced it with one that's almost identical from Anchor-Hocking (Wal-Mart), and I got the chipped one. 

Now, I generally have to buy gallon jugs of R/C fuel (10/18) and add Randy Smith's "Aero-1", aka "Snake Oil". If I'm adding Aero-1, I add it to what's left in the bottom of my fueler rig, shake it well, and then top it up from the new gallon. I'm not very scientific about it, but the AAC .46VF doesn't complain. In your case, I'd say if you dump two different mixes together before you drive to the field, it'll be ready to use when you get there.  Steve

[Randy Cuberly]

I typically mix my own fuel.  It's not really very hard but should be done carefully and it's best to filter all components during mixing.
You can get the necessary ingredients in any good...GOOD...speed shop.  Methanol, Nitro Methane ( Not nitro ethane), AA Castor Oil, and Klotz lubriplate Synthetic oil.  The measuring devices can be obtained from any chemical supply place...hundreds on line...I use 1 quart cylinders graduated in 1/10 ounce increments...You can use 1 liter cylinders graduated in CC if you prefer and do the simple conversion from metric.  It's best if the cylinders are made of Nalgene...a little more expensive but well worth the extra cost because they last forever and don't contaminate any of the components.   Several gallon size plastic jugs, and a funnel.
   
There's 128 ounces in a gallon so just multiply that by whatever component percentage you want in the fuel and that's all there is to it.  128 X .20 = 25.6 oz of oil, 128 X .10 = 12.8 oz Nitro Methane, 25.6 + 12.8 = 38.4 (oil and Nitro), 128 - 38.4 = 89.6 oz of Methane...for simple 10/20.  Simply divide the oil content in half and use half in castor and half in Klotz, for 10/10/10.

  I know this is simple stuff and it's not my intention to talk down to anyone,,,just trying to keep it simple for those not accustomed to doing this sort of thing.
Klotz my be a little difficult to obtain in some speed shops...Sig still sells it in Gallons!

I prefer Klotz because it already has all the necessary additives to provide clean lubrication.

Randy Cuberly

[Garf]

I use a 250 Ml graduate cylinder and mix a quart at a time starting with castor,  then add nitro, transfer to quart bottle, then fill to half full with methanol. Next, shake for all I'm worth. When the foam settles, top off with methanol and shake again. I use no additives but I have tried ether and acetone at  various times.

[Steve Helmick]

BAD idea to start with castor and nitro. They do not want to mix. That's why you start with castor, then add the alcohol.  Steve

[Randy Cuberly]

BAD idea to start with castor and nitro. They do not want to mix. That's why you start with castor, then add the alcohol.  Steve

Steve,
You're absolutely correct about not starting with Nitro and Castor...when I wrote my post I simply put the castor and nitro together to determine the amount of methanol needed.
I mix the nitro with klotz then add that to the methanol then add the castor and shake gently.

However I would add that if you should put the nitro and castor together they will mix alright when added to the methanol... it will take a little longer and should be gently shaken for about a full minute before using!

I seldom mix fuel in less than gallon quantities.  When feeding PA65s etc., even gallons don't last very long.

Randy Cuberly

[Dan McEntee]

 I have one question. Once you calculate what you want for oil content, you start with that  amount, then add the alcohol. Do you use a full 128 ounces? The oil has quite a lot of volume, and when adding the alky you'll end up with more that a gallon if you are mixing in a jug. Do you fill up your container to a certain point and allow for the nitro to come out at an even gallon? Am I making sense?
    Sure was easier to just pick up a few gallons at the SIG contest each year!
   Type at you later,
    Dan McEntee

[Chuck Feldman]

I mixed my own fuel for years. I had a glass graduated cylinder that had a 0 to 100 scale on it. I added the oil to the amount I want to use then the methanol up to 90. That left a space of 10 for the nitro. What could be simpler than that. Once mixed I poured it out into metal cans. Now that I am retired and cannot scrounge up the fuel ingredients I just buy fuel as needed.

[Steve Helmick]

I have one question. Once you calculate what you want for oil content, you start with that  amount, then add the alcohol. Do you use a full 128 ounces? The oil has quite a lot of volume, and when adding the alky you'll end up with more that a gallon if you are mixing in a jug. Do you fill up your container to a certain point and allow for the nitro to come out at an even gallon? Am I making sense?
    Sure was easier to just pick up a few gallons at the SIG contest each year!
   Type at you later,
    Dan McEntee

Well, no, it really doesn't make any sense. If you mix 1 quart of oil, one quart of nitro and two quarts of methanol, you get one gallon of fuel, 25% oil and 25% nitro. Although, I usually used the ounces scales on the Pyrex quart pitcher. Don't trust the volume of any cans or jugs...or fuel tanks, for that matter. The reason to add castor oil and alcohol together first is that it helps the nitro mix into the castor oil.

If you're using Klotz, it would matter less, because I suspect the synthetic part of the oil would make the castor mix with the nitro easily enough, plus it's pretty low viscosity compared to castor. But I haven't mixed any fuel from scratch using Klotz, only UCON. I still followed the order, just because the alcohol helps rinse out the residual oil left in the measuring pitcher. I probably overpoured the alcohol a tad to make up for the residual oil, but not very much, then poured the nitro as accurately as possible into the pyrex pitcher.    Steve 

[55chevr]

Some good stuff here.  I have mixed racing fuel for years. Methanol and nitromethane and depending on air density and temperature an igniter.  Never mixed 2 stroke fuel but I might just try it.  The oils have my interest as I added caster to Sig fuel for Fox 35 use.

Joe

[Brett Buck]

I have read here about some people mixing fuels.  For example, some mix 10% nitro and 5% nitro fuels of the same brand, I presume, to get 7.5% nitro fuels.   Some mix in extra castor.
   

    For 7.5, or some intermediate value, I suck some out of the 10% and some from the 5% into the same syringe, that, and squirting it into the airplane, seems sufficient to mix it. Once I figure out what I want, I then mix up a big jug with a pyrex mixing cup, or similar.

    Brett

   

[Trostle]

I have read here about some people mixing fuels.  For example, some mix 10% nitro and 5% nitro fuels of the same brand, I presume, to get 7.5% nitro fuels.     

This might not be a direct answer to whatever is being asked here, but thought I would share what I know some fliers do.

I order fuel in cases, four gallons to a case, to my order in two different blends. Each gallon jug will have a mix of 20% oil - half of that being castor and the other half being synthetic oil.  (The engines I run are quite happy with this oil content.)  One set of gallon jugs will have a total of 10% nitro, the rest is alcohol.  Another set of jugs will have a total of 25% nitro, the rest is alcohol.  I have a chart that provides the amount of these two blends combined in a large calibrated syringe so that I can fill a tank with any amount with a nitro content ranging from 10% to 25% and the total oil content remains the same.  It is a useful tool when trimming an airplane/engine run and getting a desirable run under different temperature ranges and pressure altitudes.  Having different head shims and various size venturis also helps.

Keith

[Dan McEntee]

    Math has never been one of my strong pints! I guess I get the "1 gal.=128 ounces" in my head and it starts with that. I never heard it explained by starting with the oil calculation, then adding the alky calculation, and then nitro to get the total desired volume. This makes sense now. Now the question comes up about adding oil to a gallon if it's a full, unused gallon. Say you got a gallon of Morgan Omega 10%. I think that stuff is 17 or 18% and you want to bump it up to 22%. How do you calculate the required amount of oil, and do you have to pour anything out of the jug to allow for the extra oil volume, because it just doesn't blend in and not increase volume. And doesn't pouring off any to allow for the extra oil, dilute the solution that you started with?
   Thanks a lot,
   Dan McEntee

[Garf]

I have been starting my mixes with 20% castor and 5% nitro for a long time now. I pour the castor/nitro into a 1 qt bottle and add methanol to the mix to half full, then shake it for all i'm worth. I have never had separation. All I need to do then is top off the bottle with methanol. I'm on my fourth 5 gallon can of methanol with no problems.

[Howard Rush]

I have read here about some people mixing fuels.  For example, some mix 10% nitro and 5% nitro fuels of the same brand, I presume, to get 7.5% nitro fuels.   Some mix in extra castor.

In mixing fuels effectively:   are they stirred or shook or both or just poured together?  

I didn't notice whether anybody directly answered the questions, so this may be repetitious.  Just put them in the same container and give them a shake.  I generally wait awhile until I'm sure they're mixed. If you mix them in the syringe, I'd pull in a little air and move the syringe back and forth a time or two before putting the fuel in the tank, but this may not be necessary.
Fuel doesn't have to be of the same brand.  

One caution is that if you mix fuel from scratch or fuels of greatly different nitromethane content, the mixture will get cold. If it goes below the dew point, water could condense into the fuel. Just allow the jug to warm back up to ambient before you take the top off.

Is there a danger that you end of with different consistencies of fuel in the same container?

Not if you shake the mixture reasonably well.

Is there a problem with pouring the last ounce or so of one container into the next one?

Not if it's clean.  If it has a bunch of grass or other jive in it, you can pour it through a coffee filter.  

  

[Randy Cuberly]

    Math has never been one of my strong pints! I guess I get the "1 gal.=128 ounces" in my head and it starts with that. I never heard it explained by starting with the oil calculation, then adding the alky calculation, and then nitro to get the total desired volume. This makes sense now. Now the question comes up about adding oil to a gallon if it's a full, unused gallon. Say you got a gallon of Morgan Omega 10%. I think that stuff is 17 or 18% and you want to bump it up to 22%. How do you calculate the required amount of oil, and do you have to pour anything out of the jug to allow for the extra oil volume, because it just doesn't blend in and not increase volume. And doesn't pouring off any to allow for the extra oil, dilute the solution that you started with?
   Thanks a lot,
   Dan McEntee

Hi Dan,
I do not recommend trying to do this actual calculation.  It's a lot more complicated than the simple mixing instruction I gave previously which is based on percentage of volume, and one major problem is that most often you have no way of knowing whether the commercial fuel was mixed by weight or by volume.  It makes a significant difference in what the various volumes are in the fuel mix.
Adding more oil to the fuel decreases the percentage volume of all the other components in the fuel....If you add 6 ounces of oil to 10% nitro fuel it is no longer 10% nitro fuel it is less.
If you really want to do this I have a spread sheet i can send you that will calculate the amounts for you but the problem still exists of not really knowing what you are starting with.

Randy Cuberly

[James_Mynes]

If you really want to do this I have a spread sheet i can send you that will calculate the amounts for you but the problem still exists of not really knowing what you are starting with.

Randy Cuberly

Randy,

I'd like a copy of that spreadsheet if you don't mind.

TIA,

Jim

[Allen Eshleman]

Thanks guys,

I got my answers.  Mostly I have been mixing 5% and 10% nitro fuels from Brodak to get  7 1/2 %.  This I have done with the half castor/half synthetic fuels.    The other day I was flying a B-40 powered plane with a gravity flow tank.  It leaned out half way through the flight tow times..  The first time it was dirt in the filter.  The second time it wasn't that.  I think I am just going to open the needle a tad.  I was using a mixture of
Brodak,  Fox and a bit of Tower fuels - a use the last drop mixture. 

I like the coffee filter idea for pouring.  Thanks again.   I will also be doing some shaking which I haven't been doing.

[Paul Smith]

I was schooled to always put in the oil first so you can't forget.  Also the oil is sticky & gooey so the methanol will wash it into the fuel and not leave it stuck to the measuring device.

I would add the nitro next, even though it won't blend with the nitro immediately.  Finally, top off with the cheapest thing, the methanol.

I've given up on rounding up chemicals and just buy mine from Randy Ritch.

If I went back to mixing I would calibrate a one gallon plastic jug using water.  I would put marks on the outside with an industrial strength Sharpie.  Then I could transfer the marks to other plastic jugs.  I could then mix the fuel directly into the jugs without any intermediate measuring cup.

[Brett Buck]

I like the coffee filter idea for pouring.  Thanks again.   I will also be doing some shaking which I haven't been doing.

   I know it is tempting, and I know several people who use them, but I would strongly suggest something other than a coffee filter. I have seen too many cases where some fibers, apparently from the filter, got into the fuel and caused all sorts of havoc. You can get metal filter media of any arbitrary mesh size from McMaster or even well-equipped  local hardware stores, so if you feel you want to filter it while decanting, that's a much more reliably way to do it.

    However, I don't filter it into cans at all, even when mixing it up.  As far as I have been able to tell, there is nothing in the fuel from the factory (Powermaster or SIG) that needs to be filtered out. I run filters in the upline and used the same ones for years and years, and dozens of gallons of fuel, and never found more than an occasional speck of dirt. As long as you handle the fuel properly (don't stick your syringe tube that has been laying on the ground into the jug, etc), nothing it going to get into it.

   Dirt occasionally gets in from handling, and fuel tanks and pipes frequently shed no matter how careful you are, so I still strongly suggest using filters in the airplane, but I don't worry too much about the filtering the fuel for material from the factory cans/jugs.

     Brett

[Howard Rush]

There was always grass in the last bit of fuel in the jug when we flew in Arlington, which is the last time I burned fuel. 

[Juan Valentin]

 We add a few drops of Armor All to prevent foaming to the mix.
                                                                                                 Juan

[Brian Hampton]

I had a glass graduated cylinder that had a 0 to 100 scale on it. I added the oil to the amount I want to use then the methanol up to 90. That left a space of 10 for the nitro. What could be simpler than that.

You may not have realised it but you were mixing using the metric system. If your cylinder was 1 litre then that's near enough to a quart.

[john e. holliday]

When I was playing with F2C, we had and I still have a 200 CC cylinder we mixed our fuel with.   It is easy to mix when you go by percentage instead of weight.

[Randy Cuberly]

There was always grass in the last bit of fuel in the jug when we flew in Arlington, which is the last time I burned fuel.  

I always wind up with tiny bits of broken up asphalt in mine...I always use an up line filter and a tank to engine filter and still sometimes get clogged filters on the engine line.  Worst was dandelion fluff...couldn't see it and it wouldn't flush from the filter.  Go figure.  Cost me a flight in a contest.

Randy cuberly

PS:  Jim Mynes...sent the spread sheet to you e-mail.

[Steve Helmick]

I have been starting my mixes with 20% castor and 5% nitro for a long time now. I pour the castor/nitro into a 1 qt bottle and add methanol to the mix to half full, then shake it for all i'm worth. I have never had separation. All I need to do then is top off the bottle with methanol. I'm on my fourth 5 gallon can of methanol with no problems.

It's not cold or even cool, usually, where you live, which makes a huge difference. Unless you use a LOT of nitro, you shouldn't have a problem with castor settling out. Upwards of 30%, I'd guess, but I never mixed anything with castor in the old days and I think the fuel I made for Gary Gingerich was 0% nitro (by request) for his Yatsenko .76. It did have some castor, maybe 5%. Here, Fox Blast looked like there was a snow storm going on inside, one Memorial Day weekend in the '60's. I took it into the Men's Room, ran hot water on the can, and shook it up to get the castor to remix. Worked ok as long as I got my flights in while the fuel was warm enough to keep the castor from turning to flakes.  Steve

[Garf]

I have a funnel made up with a screen made of MicroMesh screen. All components that go thru a funnel get filtered. If you fly on grass, you can't help picking up some trash in the fuel. When I refill the flight kit bottle, I put the remaining fuel in a 1 qt bottle thru the filter funnel, then top off the qt using my reserve fuel, then pour the qt back thru the filter funnel to the flight kit bottle. I still use filters on all my planes.

[Steve Helmick]

You don't want to filter out the castor oil on a cold day; you want to warm up the mix and get it back in solution. Otherwise, you're running your engine with little to no oil.

If you use uniflow, you can help yourself a lot by using either muffler pressure or putting one of those plastic Master Airscrew fuel filters on the inlet with a short section of hose. The filter will collect some micro seeds and bugs, so you do need to be able to clean or replace it.  Steve

[BillP]

I don't mix my own anymore but the only time I ever needed a filter was with the Red Max castor 15-20 yrs back. I used a piece of ladies stocking to get the big white chunks out and one of those disposable cone shaped paper paint filters to get the finer particles. When I changed to Fox and Sig castor the problem didn't exist. In the early days I mixed fuel with stuff from the local pharmacy and it was clean too. I run filters on my engines anyway. Never had a problem with castor not mixing quickly or sticking to the sides of a container here in Florida temps, even with zero nitro fuel.

bp