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This ZIP contains an Excel spreadsheet. It was made by Alasdair Sutherland who is at this forum as well. Just google for his name to find the original file. Now it contains the IM data from Wikipedia. The spreadsheet suggests weight and power for most realistic rendering of an original airplane at model scale (1:6 here).

With a wingspan of nearly 200 inches (5 meters) and only 22.7 lbs (8.7 kg) the 1:6 model would be like a huge bag of air. Probably it will come out a bit heavier but will still be sort of a powered glider, even if with a bad glide angle. Scale power would be only 0.47 hp but more wouldn't hurt. The model would have parkflyer wing loading and fly at parkflyer speed (18 mph). So much about handling.

Anyway, if we take the balance plan for granted the distribution of load (weight) on wing and stab is clear:

Take the quarter chord point (leftmost point) for the pivot of a lever. The airplane's weight pushes down on this lever in the C/G (rightmost point) at a lever arm of 1.6 m, the stab lifts at a lever arm of 12.5 m. The lever arm ratio 1.6 / 12.5 = 0.128 is the same for original and model. It means the stab lifts 12.8% of the weight, so the wing has to lift the rest - 87.2%.

If I got the book correctly, the stab's area is 0.23 (23%) of the wing area. Due to the stab's low aspect ratio it's less effective than the wing (only 17% effect instead of 23%) so it needs more angle-of-attack than the wing to produce a certain lift. Since 18.7% of the total area (23% of the wing area) have to produce only 12.8% of the whole lift there should be still less AoA needed on the stab than on the wing. Correspondingly (I think), the sketch in the book shows less incidence of the stab than of the wing.

Just a nice consideration while having my sunday afternoon coffee... :-)



The evening coffee was less successful:

The neutral point (middle point in the sketch) is 1.25 m aft of the wing's AC, that's exactly 10% of the distance between wing and stab (ACs) - curiously. Only guessing, but this could be even plausible. The NP is approximately the balance point between the wing area and the effective stab area. Assumed the reduced effect of 17% compared to 23% is due to small aspect ratio, a factor of 0.59 - which is a fair estimate of the effect of wing downwash - would make that 10%. They might even have a fuselage effect factored in, which usually shifts the NP forward, even if I'm not sure if that applies to the IM. If in this case the NP is shifted rearward, the 0.54 estimate from my textbook could apply.