Why don scale models fly at scale weights?
Can anyone please explain to me in lay persons terms why we can scale our planes to 1/4 the size but not 1/4 the weight of the full scale versions? In example, if a full scale Piper Cub, theoretically weighs 1200 lbs, why wouldn’t the 1/4 scale version be able to fly at 300 lbs? Your input would be appreciated. From : Don Stackhouse Stan, there are a number of factors at work here. 1. Lengths scale linearly with scale factor, but areas (like wing area and the cross-sectional area of structural members) scale with the square of the scale factor, and volumes (which determine weight) scale with the cube of the scale factor. All this assumes we’re duplicating the same structural design and materials, if we change any of those it gets more complicated. In plain english, this means that if it’s half as big, it will have 1/4 the wing area and 1/8 the weight. Sounds good so far, but now for #2: 2. Reynolds number, a.k.a. “Scale effect”. Length times velocity times air density, divided by air v
