Sal, I think I see the problem why you need your head examined. I don't know if I would ever dare to fly such a valuable model and would at least try to minimize all risks and uncertainties. What I regularly do is calculating a model's flight behaviour (and its balance as part of that) in advance (and even try it in a simulator). That works pretty well but has its limitations. The other method is building a chuckie from slab balsa or foam and test-gliding it. My point is that this method has its limitations as well, and both methods especially in this case.

As the sketch from the Russian book suggests, the airfoil pitching moment plays a vital role here. It's not evident in this clipping how the NP has been calculated. But it wouldn't be too hard to do such a calculation for your model with the dimensions from a top view and some airfoil data. (There are even free tools.) Here's the weak spot since there won't be any moment measurements. But you never know and besides the moment coefficient may be guessed what is better than nothing and probably accurate enough.

A small test model wouldn't be better either, because you had to replicate the wing and stab airfoils exactly enough so the lift curve slope and moment coefficient (the critical points here) are roughly the same. I doubt that is possible. Bummer.

So if you have a top view and the airfoil shape we could try to calculate (guess) the neutral point and a suitable C/G position. In my experience that is sufficient for the maiden flight. (Even for me considering I'm chicken.) Would be fun to do.


As to the Russian book, after sleeping over it I think it uses the Ilya Muromets as an example to show an unstable condition. The text seems to argue that if and when the airplane is pitched up the lift increase on the wing would be bigger than on the stab so the pitching up is even aggravated. That is instability (we would say lability in German) but that doesn't mean the airplane is not balanced. The moments are always balanced only at a certain pitch angle and corresponding airspeed, but the pilot has to correct immediately if this angle and/or speed is disturbed. Even that isn't too bad, after all we know that from flying helicopters, we are just not used to it in flying airplanes.

Looking at the pictures of the Ilya Muromets I can well imagine it flew that way. The short nose (nearly non-existent) and the big stab let it look like a tandem configuration. Even a tandem would have the C/G ahead of the NP, but in the Web I found a site which says the IM was hard to fly. That's no evidence but at least indication. My point is that means you shouldn't fret about the maiden flight. Even if it's unstable it can be flown and it has been done before. I think even if it's still not balanced it can be flown by an average pilot. What helps is the slow flight speed, the big stab and elevator on a long tail moment arm, and its sluggishness. A small free-flight test model wouldn't help at all because it would simply crash by all means if it's quite balanced yet unstable like (supposedly) the original.

Now that's my new theory. I'm still surprised myself (aha effect). In my Web search I came across a picture of an Ukrainian 1:10 IM model. Maybe you can make out the builder and ask him.

And yet another afterthought: You can buy a perfect pilot for the model, a modern flight stabilizer or at least a gyro for the elevator. Take one that has a "lock mode" like those for helicopter models (heading lock) to have a certain pitch angle locked and controlled by the transmitter stick. Modern fighter airplanes aren't inherently stable as well and have artificial ("electronic") stabilization instead. Maybe the first airplanes weren't stable because they traded stability for more lift (really lifting stab), or they just didn't know better, who knows. Anyway, this should have occured to me earlier...

Like a stabilizer system today turns an actually too small and squirrely beginner model into a stable and calm flying platform, it would make your model fly not only set up unstable but even out-of-balance and even in a bit wind. Duh! :-)