motor sailplane

[hello183]

I wanted to design my own airplane

I am really intending for it to be constant chord, 1.5 meter wing span, and to weigh around 300 - 500 grams (like 10 to 17 ounces.). It should have around a 22 cm chord for about 6.8 aspect ratio and 3300 cm2 wing area (511 sq inches). It should have around a 3 - 5 oz / ft2 wing loading. The airfoil i was planning to use an S7055, and the control surfaces and the back of the fuselage I wanted to build with sticks. I have been struggling with the idea. And I think it could fly nicely if I designed and built it correctly. The fuselage I drew was 112.5 centimeters long. It could use maybe a 2208 brushless motor. What do you think of the idea? Should there be things I should reconsider? I have not built many things but I have built some frame structures and also some tiny airplanes, which I just threw around in my backyard. I will post the pictures but first could you just tell me if the general is ok (like is it possible for me to build a structure that light?, should I shorten the fuselage size?)

 

[Piotrsko]

Not using any engineering, TLAR. If it looks right it could probably be right.

 

[hello183]

ok, the drawings don't look bad but since i havent really used radio equipment, I wondering if I should maybe buy a simple airplane, I liked the stevens aero square one. Maybe i'll get that and learn from it first before trying this design. I might do that so I can get a good idea for the sizes of some things.

 

[quorneng]

hello183
It is certainly possible to build that light but you might have to get clever with the materials used.
The only issue with such a light wing loadings is it don't want to fly fast. It you try it will come down pretty quickly. In gliding terms it will lack 'penetration'.
Just give you an idea this is home design with a constant chord wing 1.4 meter span with a 21 cm chord.

A bit heavier than your proposal at 743 g but that is with a big 3000 mAh 3s that gives it a power on 'cruise' duration close to one hour!
Just the wing by itself, including the aileron servos, weighs 134 g.
Well mannered It glides really nicely even with its simple Clarke Y wing section. Given the opportunity It thermals well too.

 

[hello183]

thanks, quorneng. Low wing loading would be fine in my case because I'd like to fly slowly. It would also want to come down slower, which is good too. For starting, what do you think? Should I try first building the Square one to learn radio control? Should maybe I try building some other airplane. I'd like it to be a sailplane, though, and no bigger than 1.5 meters for now. It would make sense to build from a kit before making a design of my own.

 

[quorneng]

Without a bit of experience of building it would make sense to start with a kit. No design required you just have to develop the building skill which is usually more than enough to start with. More important you know a kit plane will fly if built and balanced correctly. If it doesn't then the problem is how you built it.
If of course you both design and build build and it doesn't fly properly without quite a bit of experience you will have no idea whether it is your building skill that's at fault or whether your design has a fundamental aerodynamic problem.
It can be argued that a "ready to fly" foam motor glider is a good way to start learning RC flying. Simple and pretty robust it will fly straight away but learning to fly it really well as a glider and in variable conditions will take a bit longer.

 

[hello183]

I see but I am not very interested in flying as much as I am with building. So, I think for me a kit would be better, even if it costs more and takes more time.