Sorry, both text and sketch seem to be clipped what doesn't really help. Nonetheless I dabbled in translating the text and interpreting the sketch:



Relating to the airplane "Ilya Muromets" we obtain the following. If on the wing the increase of lift force DYwing

= 1000, then on the stabilizer we get less increase -- corresponding to the smaller area its equal to 0,23DYwing,

but because the stab has less length (span, or slenderness or aspect ratio?) the increase will be even less, that is 0,17DYwing.



In the drawing, the dimension should be meters.

Quite surely фокус (the middle point) means Neutral Point.

Since цеитр тяжести means center of gravity, the abbreviation ц.т (the right point) should indeed translate to C/G.

Picture 10: Balance plan for the airplane "Ilya Muromets"



If the wing's angle of attack increases...




Here I stopped because it's too tedious for me and the rest doesn't seem to add much to comprehension. I'd say the book explains the simple balance plan sketched here but I can't really interpret the rest of the text so I'm not sure I grasped its meaning, especially since the rest (following the clipping) seems to mention the Neutral Point, variations in angles of attack and resulting lift forces, that is the really interesting things.

Anyway, I'm quite sure that the middle point is the Neutral point and the point to its right is the C/G. The leftmost point simply should be the wing's aerodynamic center (center of lift), which is assumed at quarter chord. Unfortunately, the sketch is rather coarse and suggests the C/G is at the trailing edge, but it's not.

Obviously, they took the leading edge as a reference what at least was quite common practice. The NP is 1.88 meters behind the LE, and the wing's AC is 1.25 m in front of the NP. That means it is 1.88 - 1.25 = 0.63 m behind the LE. Wing chord is 2.5 m and a quarter of that is 0.625, so 1.88 m is just a rounded value.

Now the C/G is 1.6 m behind the wing's AC, giving 0.63 + 1.6 = 2.23 m behind the LE, wheras the TE is 2.5 m behind the LE.

Still that's a pretty rearward C/G, of course, but I think they had the stabilizer produce lift. I feel affirmed by what I believe to understand of the text, even though no incidences are mentioned. The sketch seems to suggest quite some wing incidence, but that doesn't necessarily mean a forward C/G since the thin and highly cambered airfoil has a huge pitching (down) moment. I think that's why they needed a big stab (like on old free flight models).

Really annoying is that the C/G is (0.35 m) behind the NP, not ahead of it. In fact, the static margin is -0.35 / 2.5 = -0.14 (-14%) what is perfectly good by absolute value but annoying by being negative. That doesn't have to be wrong, though, if you take the pitching moment and the lifting (and thus pitching) stab into account. The rearward C/G could just mean the airplane was trimmed for very slow speed, even if the low wing loading is taken into account. The wings have a big aspect ratio (10 each) so induced drag should not really be a problem. Could be they knew what they were doing (and they had read their Lilienthal).

I would use thin and highly cambered airfoils for the model as well. They should be just fine at model Re numbers and make the model realistic in flight. You should just look for a big hall to fly it since it won't cope with wind very well. ;-)