How can I calculate the drag coefficient for a given wing design?

I am building an RC plane (for the first time. I am doing it for a competition) with a twin boom configuration like this:

My wing shape is like this:

I decided that the lift should be 0.8g and I need to use this equation to find the wing area (as per the instructions)

$$F_l=\frac{1}{2}\rho v^2 S C_d$$

$F_l=0.8$

$\rho=1.225$

$v=12m/s$

Can you help me in figuring out the value of $C_d$ considering that I am using Clark Y aerofoil design?

After that, I will measure $b$ using the aspect ratio.

$$\frac{b^2}{S}=\text{Aspect Ratio}$$

My instructor asked me to obtain a wing span of 80-100cm. So I will have to choose Aspect ratio as well.