Ojimak F-22 Raptor

[legion]

From what I could translate of his blog, he uses 120 gr/m*2 paper.

[Renaud]

You cannot change the thickness (i.e. weight) of the paper according to the scale you intend to build your plane... This makes large planes too weak.
For those who don't understand that: make sure you understand a surface is the product of two factors, but a volume the product of three factors. We say 1 m2 but 1 m3, it is not the same

1)suppose your plane has a 1dm2 (that is 10cm x10cm) flash area - and weights 10 grams
so the ratio weight:flash area is 10:1 That is 10grams per dm2
A flyable glider must not exceed this limit

2) Then you enlarge your plane by 200%.... (length x2 and span x2)
flash area rises up to 4 dm2 (1dm2 x2 x2 = 4 dm2)
The same way, you doublesize the thickness of the paper (what you must not do!)...
.... and weight rises up to 10grams x2 x2 x2 = 80 grams

the ratio weight/flash area is now 80:4 ... that is 20 grams per dm2

Since it ought not to be above 10 , this means that the plane is too heavy, it couldn't fly .

Had you used the same paper, weight would have grewn up the same as the flash area, and the ratio weight: flash area would have remained unchanged.