Chopper 64 (oz10373)
About this Plan
Chopper 64. Free flight helicopter model, for Fox .15 engine.
Quote: "Good in '64, better in '65 is the story of our Nats winning helicopter. Performance plus realism as well. Chopper 64, by Glen Lee.
This helicopter was built as a 'test-bed' for various rotor control configurations, but it turned out to be the best flying chopper that I've ever built. It is the most stable model helicopter I have ever seen, having crashed only twice in two years of flying. These two mishaps were my fault. I was trying different methods of getting forward flight.
The shock-mounted cockpit and tail reduce damage considerably if the model hits anything on the way down. They also make transportation much easier.
As to theory of design, this model is a 1964 grouping of many individuals ideas plus my own. Jim Walker's rubber bandpowered 'ceiling walkers' had a prop on each end and were quite stable. Clough built a CO2 engine-powered model about 1949 with the motor on the bottom. It took us about ten years to find that is the best place for it.
Duct-type fuselage doesn't do much except keep your fingers away from the prop and add vertical area. This vertical area is important since it keeps the model stable when the power cuts, the model drops, and rotor blades have not come up to auto-rotation speed. Without it, model sometimes tumbles.
The simple two-blade rotor works very well, auto-rotation dropping speed is about like a parachute. Don't try a model chopper without the blade control stabilizers. They improve reliability about 100%.
Many things have been tried to get these models to fly forward or circle. One successful idea is a universal joint in rotor shaft. Tip rotor just a little bit. Setting one blade at 0 degrees positive angle will make the model go forward, and a little extra weight in the nose will also help. A fuse or timer operatedthrottle on the engine allows automatic take-offs or power-on landings.
Begin construction with fuselage. This is mostly a shield for the prop, so it can be any shape as long as it is large enough to clear the prop by about an inch on the diameter. Circular shape shown is the strongest I have found. It is built by cutting quarter inch balsa sheet into pieces 4-1/2 in long and edge gluing these until you have a plank at least 35-5/8 in long. Pre-glue all joints and let assembly dry overnight. Next, wet one side with warm water and then wrap the plank around a circular form. I found a 5-gallon distilled water jug is about the right size. Tie plank around the form until balsa is dry, then remove and glue last joint together. Dope ring several times, sand it and then dope silk around the outside.
If you can't find a circular form to shape balsa, build it like the Square 8 fuselage with 8 flat sides. Center post is a 5/8 inhardwood dowel about 6 inches long. Drill a hole through the center in a lathe or in a fixture so it will be straight. Use a 1/4 in O.D. brass tube..."
Quote: "Hi Steve and Mary, I don't remember if I ever sent you these files on Glenn Lee's successful free flight helicopter. My father knew Glenn, and my dad and I went to the nationals one year to watch this machine fly. This experience along with a Roy Clough Jr free flight helicopter built by dad were the prime motivators for me to get into RC helicopters. Gene"
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User commentsGlenn Lee, well known back in the '60s and was Nats champion several times.
rchopper56 - 25/08/2018
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