Acrobatic Clipped Wing Cub XL - My first post!

by JoshBuilder | August 14, 2018 | (4) Posted in Projects


(pictured: access hatch open after build is complete) 

Project Goal:

Build around an existing set of electronics that I have from a recently crashed plane, build something "3D Capable", good looking, and actually flyable. 

Start:

I chose to base my model off of the clipped wing piper cub, which is capable of some aerobatic maneuvers. I bought 9 sheets of foamboard, lots of hot glue sticks, and I printed out a 3-view photo of a clipped wing cub from google. I also used some flat 1/8 ply from yet another crashed airplane (I had a rough day a few weeks ago haha). 

I chose the scale of my model based on the size of the plane which I was reusing the motor from, the main goal was to have a similar if not larger wing area. The model that the motor is from is a Dynam SU-26m and so I sized up the sheets of foam next to the old plane, and started drawing! I was multiplying the dimensions I measured from the printed image by 6.6 (just an arbitrary number that gave me the right wingspan).


(early on, assembled to see how its coming along)

Challenges:

The first problem I had was gluing my wing when I folded it (this uses a similar wing construction to the flitetest Sparrow I believe it is called. The wing on this model however is 60 inches! I had a very hard time laying the bead of glue all the way down the spar, then back on the other spar, and then holding the wing in position before it cooled. My solution: glue fast like a maniac. 



Next problem, how to securely mount a powerful electric motor to a big foam plane. I used two pieces of 1/8" ply glued back to back and drilled appropriate holes for the motor bolts. I slotted this piece into the nose of the plane and reinforced. 


Key Design Points:

What I did to make this plane my own was make the control surfaces and stabilizers oversized. The elevator and rudder are the right width and height, but a few inches fatter (longer front to back) than they should be. Also, the actual control surface that moves is far larger than in a scale cub. Note, the ailerons I actually chose to have hang right off the back of the wing like a STOL plane so hopefully I can have some slow flying performance! This also allows me to change the size and shape of them if I so choose. 


Strength:

There are diagonal supports on the vertical stabilizer because I don't trust just one glue bead to hold it on, and also there are X shaped cross braces inside the fuselage which provide stiffness as well as a place to put wires and stuff (the esc just happens to be zip tied to a cross brace). The wing has two vertical spars and a wooden dowel inbetween to prevent catastrophic failure hopefully... The landing gear are from the SU-26 and are screwed to a large plastic plate inside the fuselage. 



Final Points:

You can see the battery compartment under the ESC with Velcro to help the battery stay in, and the plane is slinging a 13x6 prop for lots of torque and low speed. As you can see the fuselage is hugely spacious so maybe one day I can put something like a bomb drop in there! And this thing has plenty of power so maybe it can be a glider tow plane we shall see. It has not flown yet all that is left is to balance her, and decorate the outside with colored tape. Lets hope she flys well, the last one didn't but I learned from the mistakes and came up with this! Hope you enjoyed. 


p.s. I obsessively started and finished this within 24 hrs haha 


COMMENTS

CascadeRC on August 16, 2018
I relate a lot to that last line.
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JoshBuilder on August 18, 2018
Haha it is a problem
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Jackson T on August 16, 2018
Nice job! I couldn't design anything in less than a week! That is, after spending a week deciding on the basic dimensions!
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JoshBuilder on August 18, 2018
Yeah it the design process just flew so to speak!
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Acrobatic Clipped Wing Cub XL - My first post!