James,
With the thoughts already up in this thread, you have a good start...
As for how much to scale up or down, try this:
You know the area of the model you want to scale...
You have a good idea of the area that suits the engine you will use, from checking successful designs for those engines...
Wing area is figured by multiplying span by average chord. Don't worry too much about that, all you want is the scaling factor. Think of it this way.
Call your inspiration model's area 100%. IOW, scaling factor is 1.
Its wing Area = (1 x Span) x (1 x av Chord)
For 40% more area, you need a new scaling factor - call it 'k'.
So, 1.4 x Area = (k x Span) x (k x Av Chord) which can be written as: 1.4 x Area = K^2 x (Span x av Chord) (k^2 means k squared.)
Original's Area still equals the original's Span x av Chord, so you can cancel those terms out, leaving: 1.4 = k^2. Find the square root of 1.4 (the value of k^2...)
k = 1.183.
Multiply the original's span and all other dimensions by that 1.183 and you've enlarged the entire design by 40%. This scaling factor example is pretty inconvenient, though.
There's usually a range of wing areas that do well with the engine you'll use, so you can round up or down and still be in the zone. For example, if you used k=1.1 instead, area scales up to 1.21 times the original. If you round up to k=1.2, the model scales up to 1.44 times the area (and all else) of the original.
Topic: Enlarging an existing design (Read 1091 times)
