How to compute thrust to weight ratio of a Cessna 172?
A good estimate for a personal aircraft thrust requirement would be more like 25% of aircraft weight, and remember, the "ton" of Cessna includes fuel and pilot too!

So: 1 ton x 2000lb/ton x 1kg/2.2 lb = 909 kg Cessna

213 kg thrust/909 kg weight = 23.3 % thrust to weight ratio.

But a lot depends what your plane design is.  You can test thrust requirement for level flight by gliding, then multiplying weight x altitude lost/distance flown = thrust.

So it helps a lot to have a good, strong wing too, and more thrust will be needed to climb.  15 kg may not be enough for your plane, but as long as you are on internet, you may wish to study "ultralight aircraft" to get some better information.