Aerodynamics of foamy RC jet

[long-love-rc]

Well, I am not any expert on aerodynamics at all!

But I cannot help to be curious: why all RC jets can be very stable, while in the real isn't. For example, real F-16 is not stable staticly which must relies on complex avionics to keep it stable. However, RC f-16 is very stable once its CG is well kept and trimmed.

So their aerodynamics must be very different, although they somehow looks alike. I cannot help think all RC jets(those we are familiar the foamy ones) share same aerodynamics traits.

Can anyone talk a bit on this? Thank you very much!

[Evan D]

Modern real ones are made unstable to fly a wider envelope. Models are made to be more stable since we don't have the computers and FBW to fly them for us.


You'll have a bunch of "experts" here in a minute to tell you all about it. :)

[tab28682]

Well, I am not any expert on aerodynamics at all!

But I cannot help to be curious: why all RC jets can be very stable, while in the real isn't. For example, real F-16 is not stable staticly which must relies on complex avionics to keep it stable. However, RC f-16 is very stable once its CG is well kept and trimmed.

So their aerodynamics must be very different, although they somehow looks alike. I cannot help think all RC jets(those we are familiar the foamy ones) share same aerodynamics traits.

Can anyone talk a bit on this? Thank you very much!

The answer is actually pretty simple.

While an F-16 is statically unstable at the CG location of fhe actual aircraft, we simply change the CG and move it forward on models like this to give some amount of static stabilty. Typically a 5-10% stabilty margin gives us what we need to be able to fly this type of aircraft as an RC model.

I have never encountered a model that could not be made stable enough to fly with the CG properly located, including F-117 and B-2 models..

Some model jets do have slightly larger tail surfaces, which also helps.

[xviper]

If you fly them with enough power/thrust, even a flat cardboard airplane will fly well. Oh wait, isn't that how FliteTest became so popular? Who needs aerodynamics when you can forcibly yank a thing through the air, kicking and screaming?

[xviper]

This thing should NOT fly and yet ...........................

We all know that elephants can fly but should they? (I challenged Otto to make one and in a few weeks, he did.)

[themudduck]

LOVE the flying elephant!!

Aerodynamics of models vs full-size can be a very interesting (and very long) subject. All planes fly according to the same basic physical rules (thrust, lift, gravity, drag) regardless of their size, but besides the CG which is very important , there are some other mysterious things at work... Say you scale a full-size F16 down by shrinking it, let's say 1/10th size. So the model is smaller and it weighs less... about 8 pounds instead of 26,000 lbs. But, its flying through the same air. I mean, the air isn't scaled down. So that has an effect on what's going on.

[long-love-rc]

Thank you all experts for sharing your thought! very informative

[kallend]

Modern real ones are made unstable to fly a wider envelope. Models are made to be more stable since we don't have the computers and FBW to fly them for us.


You'll have a bunch of "experts" here in a minute to tell you all about it. :)

Actually there are some well qualified aero experts who do post on here. No need to be snide about expertise.

[Evan D]

Bingo! :)

Actually there are some well qualified aero experts who do post on here. No need to be snide about expertise.

[Splat]

My dad used to always tell me that you can make anything fly as long as you throw it hard enough lol

Thrust overcomes drag and creates lift which overcomes gravity. 😁

[long-love-rc]

My dad used to always tell me that you can make anything fly as long as you throw it hard enough lol

Thrust overcomes drag and creates lift which overcomes gravity. 😁

Ha, to fly elegantly, there is still quite some delicacy to appreciate!

[Turbinefancy]

The answer is actually pretty simple.

While an F-16 is statically unstable at the CG location of fhe actual aircraft, we simply change the CG and move it forward on models like this to give some amount of static stabilty. Typically a 5-10% stabilty margin gives us what we need to be able to fly this type of aircraft as an RC model.

I have never encountered a model that could not be made stable enough to fly with the CG properly located, including F-117 and B-2 models..

Some model jets do have slightly larger tail surfaces, which also helps.

This sums it up succinctly!