|By Contributing Editor: Don "No Knocks" Nix FLYERDON@aol.com|
Fact (A) - Its quite likely that no other single facet of modeling generates as many myths misconceptions, misunderstandings, errors (and more than a few lies), or as much............ outlandish goofiness as model fuel .one of our absolutely necessary, non-optional items for powered flight.
Fact (B) - Of all the above, the one fact that rouses the most questions - and without doubt the most wrong answers - is the ongoing nonsense about the amount of oil required in model fuel.
Myth: Model Glow Fuel must contain XX% oil to operate properly, perform well and protect the engine.
Fact: There is no such fixed number .at least not a valid one.
Why not? Think about it: In order for this to be true, all oils used in model fuel - all of them - would have to be identical in every characteristic. Does anyone honestly believe they are? I doubt it.
While lubricants compounded for full-size engines - automotive, recreational vehicle or aircraft - are rarely, if ever, suitable for use in model engines (for many reasons), nevertheless, there are a number of base lubricants that are available for our highly specialized use. However, most of these must be modified slightly or extensively by the use of a variety of additives and modifiers.
While Klotz model oils are perhaps the most well-known to
the average user, and are quite good, they are by no means the only lubricants available
to model fuel blenders, and there are currently a number in use. Each has its own
At this point, we should point out that were speaking
of the so-called "synthetic oils" popularly used in modern model fuels. Castor
the oil of choice, and, indeed, the only suitable model engine oil for many
years, is more of a common
However, few model fuels intended for R/C use today contain only castor oil as the lubricant. For the purposes of this discussion, we will only deal with fuels containing either straight synthetics, or a blend of castor and synthetics.
So what does all that mean?
Lets draw a little picture here Suppose at some point in your life, you become concerned about living a long and healthy life, so you decide to consult a doctor for advice as to how to accomplish this. When you come to the subject of food, you say, "Well, tell me, Doctor .if I wanna still be healthy and virile at 90, how do I eat?" The good doctor replies, "Mboy, if you will eat two pounds of food a day, youll be fine!"
My guess is your response would be something like, "well, what kind of food, Doc? After all, no two are exactly alike .is that two pounds of lettuce or two pounds of pork chops?" If he replied, "It doesnt matter. Just as long as you eat that two pounds every day, youll probably outlive your kids." My bet is that youd run, not walk, out of that quacks office!
Why, then do we blindly follow someones Word From On High when they say (in words engraved on stone tablets), Thou shalt use no fuel that does not contain XX% oil." It makes absolutely no sense to me, nor do I think it will to you, if you just stop to think about it. All foods are different; so are oils.
If thats true, why do the instructions with my engine specify a fixed percentage of oil? Simple - to protect themselves. All engine manufacturers have been burned (figuratively and literally) in recent years by "bargain priced" fuels containing either inferior oils, or insufficient amounts of oils. Every one that Ive talked to will admit off the record that they know that fuels containing good oils wont need as much as their instructions say. But they also say they know they have no control over that, so they are going to print a high number, in hopes that amount of even a cheap oil will be sufficient. Frequently, it isnt.
So why not just put a lot of oil - at least 20% or more - in fuel and not worry about it? A lot of reasons all good ones. For example:
So, what is the right amount?
It all depends
kind of oils, in what combinations, & with what additives, etc. And for what use?
Ducted fan and helicopter engines typically need more oil,
Next installment: Synthetic or Castor oil .which is best?
Scale Aero© and Details© 1998