Induced drag and different wing types - parasitic vs. induced drag

[sur]

TL;DR Summary: School project about induced drag - I do not have a wind tunnel - and a comparison between rectengular straight wing, C-wing, and box wing (not airfoils)

I want to know how to derive/ seperate induced drag from the parasite drag

So, I am making an experiment where I'm supposed to launch (in a fairly constant environment) model gliders with wing small aspect ratios and try to prove that box wings/ C- wings are the better option than straight wings. I have already designed a model with modular wings (symmetrical airfoil). I will measure the model's velocity and it's range.
How on earth would I differentiate between induced drag and parasite drag? Is there maybe a formula for that or do I need CFD software to calculate it or an easier option for those...?
If you have any ideas and/or ideas for improvement feel free to express them

 

[jack action]

After measuring the lift coefficient ##C_l## and drag coefficient ##C_d##, you can evaluate the induced drag ##C_{di}## and parasite drag ##C_{do}## this way:
$$C_{di} = \frac{C_l^2A}{\pi s^2 e}$$
$$C_{do} = C_d - C_{di}$$
source: https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/induced-drag-coefficient/

 

[Lnewqban]

What are box wings and C- wings?

 

[sur]

What are box wings and C- wings?

These are names for wing shapes:
box/ closed wing (source: Pinterest)

C-wing (source: Sciencedirect.com)

 

[Lnewqban]

Thank you!

It seems that this is an act of balance among what you gain and what you lose with each configuration, assuming similar conditions.

Those two wing shapes try to reduce pressure bleed at the wing-tips, but increase area and corners, both feeding parasite drag, as well as additional weight that requires more lift, which increases induced drag.

For the box type, you have the additional problem of one plane interfering with the airflow of the other, as well as intentional different AOA for each for stall control (typical of traditional biplanes).

The internal structure of the box wing could be lighter than an equivalent monoplane thanks to the closed wingtips, while the opposite should apply to the extra weight and flexure of the C-wing.

As you see, there are many things to play with, while assuming similar travel velocity and useful load to move between two distant locations.

Please, see:
https://en.wikipedia.org/wiki/Parasitic_drag

https://en.wikipedia.org/wiki/Lift-induced_drag

https://en.wikipedia.org/wiki/Drag_curve

 

[sur]

View attachment 338508​

After measuring the lift coefficient ##C_l## and drag coefficient ##C_d##, you can evaluate the induced drag ##C_{di}## and parasite drag ##C_{do}## this way:
$$C_{di} = \frac{C_l^2A}{\pi s^2 e}$$
$$C_{do} = C_d - C_{di}$$
source: https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/induced-drag-coefficient/

How would you measure the whole drag coeficient? (Maybe I have missed something while reading)

 

[jack action]

You measure the drag force ##F_d## acting on your wing at a known velocity ##v## and then calculate your ##C_d##:
$$C_d = \frac{2F_d}{\rho Av^2}$$