Build and Fly a C/L Model Aircraft




Introduction: Build and Fly a C/L Model Aircraft

About: Tinkerer from childhood on. After my retirement, together with my wife, fully committed to creative production. I prefer simple solutions for non-existing problems.

Say 'model airplane' and most people think about somebody with a transmitter in his/her hands. Less known, but still alive, are free flight and control line airplanes, without R/C. Most youngsters don't know about this "pre digital" hobby. A model aircraft flying in circles on a line around the pilot, who has a handle in the hand to control the up/down movement. This project wants to inspire people, to build a balsa wood airplane from a drawing. Special for this project is that the motor of the aircraft is powered over the control lines. The on/off switch is on the control handle and the battery is carried on the person.

Watch the VIDEO of the project here:


  • - Beginners model; with some help from age 12 on.
  • - Simple construction with full size plans.
  • - Common tools and easily obtainable materials.
  • - A balsa wood mid-wing C/L airplane; wingspan 16".
  • - Electric DC brush airplane motor; 6 to 9V, 5A, 37W.
  • - Power supply over control lines. (6M. or 20F. long)
  • - Control handle with on/off micro switch.
  • - Sealed battery, min. 7.5AH, carried with you.
  • - In- and outdoor useable.
  • - Finally, cost about 40 $ excl. battery, charger; flying is free!

With a control line aircraft you can fly 'feelingly', this is an advantage with respect to R/C. The line between the handle and the model let you feel force feedback; acceleration power, motor vibrations and air pressure on the flaps like the control stick in a 'real' airplane. Success!!!

Step 1: What Do You Need ?

The best start is a beginners C/L model with a full size plan. My choice was the Scoot by Ron Warring. You are free to choose any other C/L model of the same wingspan. The Scoot full size plan and the parts list, you can download below as PDF files, for print out. Most of the stuff you can buy in the local hobby shop or over internet. For the Scoot you buy balsawood; 3mm or 0.12inch for elevator and rudder, 6mm or 0.23inch for the wing, and 10mm or 0.4inch for the fuselage. Plywood from 2mm or 0.08inch for nose, tumbler and line guide. For the handle, plywood from 6mm or 0.23inch thick. The balsa I bought was enough for 2 models.

Step 2: Cutting and Sanding Balsawood.

First you cut out the outline of the model parts. They are full size when you print on A4 paper. Draw the outline on to the balsa wood by pen or with carbon paper. Cut out the parts with a hand bow saw or a Stanley knive. Take care; take time to do it right! Be careful with the wing and elevator cutout in the fuselage. The sanding is done with two grades sanding sponges; 60 and 180. Follow the shape of the section when sanding the wing, elevator and rudder.

Step 3: Landing Gear and Motor

The landing gear is made out of a rod spring wire. It's hard to cut and to bow. As you can see; it can be done! The wheels are fixed on the axis by a wire terminal connector. Now it's time to attach the landing gear to the fuselage. I placed an extra dowel to block the landing gear to slide to the front. The 2 brackets for the motor attachment are made of alluminium strip 2mm or 0.08inch thick and 2cm or 0.8inch wide.

Step 4: Painting and Attachment Wing and Elevator

Before attaching the wing, elevator and rudder to the fuselage you can paint the model with acrylic transparant varnisch, as primer. Paint it in thin layers and more times. Line out and correct the wing, elevator and rudder related to the fuselage before putting the pegs in. For the hinges of the elevator I used very thin fiber pieces. Use always the best glue for the job.

Step 5: Attachment Line Guide, Tumbler, Rod, Handle

Now it is time to build the elevator control system. We need a triangle shape tumbler, a thin rod and an elevator lever piece. The tumbler is made from thin ply, the lever piece I bought in the shop. The steel rod is 30cm or 1foot long. It has been made exactly to keep the neutral position. For the line guide I choose alluminium square profile of 1cm or 0.4inch and 1mm or 0.04inch thick. Use rings on the 3mm or 0.12inch bolt and nut, this to connect the tumbler with the wing.

Step 6: The Finishing Touch

All is coming together in the last step. Testing is a important part of prototyping. For example: I had to calculate the (copper wire) line for diameter and strenght. I wanted to use soft cable, but the isolation made it to heavy for use. It worked out that enamel winding copper wire was the best option. Other example: Was their enough power left for the motor after cable losses? From a 12V battery was 5.2V left for the motor by a current of 5.4A. So a motor power of 28W (can be 37W). Don't forget to balance the plane. First the motor has to be directed 5 degree to the right, to pull the lines. Second; taking the plane at 1/3 from the wingtip it needs to be horizontal. Else, use lead to counter weight. I used 20gr or 0.7ounce lead around the fuselage. Roll always the line (copper wire) to a cable drum, else the wire can easily damage.

Step 7: Conclusion

Flying the Scoot for the first time was a surprise. All my calculations; motorpower, line losses, battery, etc. made that the model was flying and reacting sufficient to my control. The switch on the control handle is a godsend; I can solely start de airplane from a flat surface and decide when to stop. It is even possible to do some power on/off tricks during flight. I am shure that this concept can be enhanced. I was carrying a sealed battery of 3 Kg or 6 Pound in a strong bag (thanks Kaspar!). The goal of this project, building and testing an easy and cheap way of C/L flight, has been reached. The fun, making from a plan a model airplane, was great; even bigger the fun to fly. I hope that this instructable let people choose for the old craftsmanship; working with balsawood and a simple electric circuit.




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    36 Discussions

    Awesome! Brought back some cool memories. I built one from a balsa kit early 70's with the .049 and I bought an electric motor plastic one late 70's that you held on the spring terminals of a 6volt lantern battery to charge its onboard battery. It didnt really work very well at all.

    Kids nowadays.... they'll never know the fustration and determination of getting an .049 to run right! :)

    2 replies

    I also made a control line airplane. But it's gas powered

    you are a genius & you bring back memoirs of years gone by i remember the plastic replica planes on guide wires/gas engine.if you were not careful youd get dizzy& fall there goes the plane!!!! good for you,

    Sweet! Ole skool!
    I used to buy the Cox models at K-mart, back in the 70's!

    I love this project. It takes me back to my youth in the 1960s when I taught myself control-line flying with what was called a profile P-51 Mustang that looked strikingly like the plane in this instructable. It was powered by a Cox .049 glo-engine, a cantankerous little beast that was nearly impossible to adjust the mixture properly. If the constantly changing mixture didn't end the flight prematurely, the inevitable crash on the city playground pavement did... It got to the point where the glue holding the pieces together weighed more than the plane. I did get a whole flight out of it, finally, after about ten attempts. I like the electric power used in this version. It has to be more reliable than my old .049 was, though I do kind of miss the smell of castor oil...

    4 replies

    I had one of those, too. Never could get it to run so we just swung it around a lot.

    Your story is so recognizable; the smell and the noise. I kept a logbook in those days and yes; the P-51 Mustang and also my PT-19 Trainer is in. I scanned the Cox leaflet from around 1962. Watch this!


    Yep, that's the foldout that came with my first kits and Cox engines. I knew every word of it back then - it's great to see again after all these years. My brother and I got one of the plastic kits one Christmas but it self-destructed before it got halfway around the circle. Undaunted, the balsa Mustang came next, which also crashed, but at least it was repairable. All it took was a gust of wind in the face to slacken the lines and all was lost. The day a flight actually ended on the wheels after running out of gas I became a pro...

    I suggest a bigger one with a couple of car batteries in a backpack..

    U control, I remember it well. Exciting form of model airplane flight. The RC stuff had miniature vacuum tubes and expensive. This is a nice project and you are right the feel is much more personal. With the larger wingspan models you don't get dizzy with the increased radius lines. I'm rambling because of all the fond memories. Thanks for sharing.

    Blast from the past here :-) We used to fly C/L with diesel engines, to solve the problem one poster had re feeling giddy, walk round in a small circle, NOT turn round and round. Things we did were 'Combat' flying, two of you in the ring, with paper tapes stuck to the rudder and the idea was you cut the ribbons with your prop. We also built a semicircular "Aircraft carrier' deck and did carrier landings. Thanks for the memories of 60 years ago.....

    1 reply

    Do like Larry Renger did--fly in figure 8 loops continually so you don't have to turn your body. On a windy day he would keep the plane flying for 5 or more minutes more after the fuel ran out.

    I love the smell of nitro in the morning . . .

    I've still got a couple of Cox 1/2As and an OK Cub. Adjusted right, they really scream.