Liberty Belle (oz2485)

About this Plan

Liberty Belle. Half-A radio control sports model, for single channel. 42 inch span high wing rudder-only RC plane from May 1953 Air Trails.

Update 1/10/2024: Added article, thanks to volarlibremente.

Quote: "After years of hard and continuous work, the Radio Control Committee of your AMA was able to announce last year their goal of a 'license free' band an 27-1/4 mc. The Liberty Belle was designed in celebration of the event.

Based on previous experience with small R/C, ranging from the well-known 'Little Ship' at 48 inches with Cub .09 for power to the super-small 33 at 33 in span with a .045 Spitfire, it was decided to design a Half to Three-quarter-A ship. The design was evolved with the actual powerplant choice left until the ship was completecl and the weights checked. Choice of size was a 42 in span, as this gave a good area for a variety of engine sizes and weight variation tolerances.

The ship was completed with the amazingly low weight of 16 oz, no particular attempt being made to save weight other than a careful selection of wood. With this low weight the selection of a powerplant became the popular Wasp which brought the total weight ready to fly at slightly over 17 oz. This weight could have been shaved by using the new smaller batteries instead of the usual 412 B's and Half-A's for servo power, but the ship has proven so lively even with the natural increase of weight with age that it wasn't necessary.

I would like to emphasize the point of wood selection. A little care and time can earn you several ounces. Extensive use of sheet wood is made in the design as it is just the ticket for strong and rapid construction, but it does require wood judgment for maximum efficiency. Weight is of little importance if you are willing to go to a Three-quarter-A engine like the Royal Spitfire or the Cub .074. The wing design has flown over 1/2 lb more with such engines; however, if you are like the writer you will be striving for a true Half-A R/C and won't want to take the easy way out.

Aerodynamically the plane differs somewhat from my previous designs. The principal change is that the stabilizer is set above the turbulent wake of the wing. This was done to raise the stab directly into the prop slip-stream in an effort to lower the required downthrust and to keep the nose down under high power. As a by-product the wing is set at a rather unusual high angle of incidence to the fuselage, which in turn means a relatively high ground angle and awroved take-off characteristics. By using a deep forebody and subrudder the CLA is kept low enough so there is no overbanking tendency in turn entries.

The resulting flight characteristics are all that can be desired. Despite the light wing loading the ship shows a good turn of speed and the steadiness in rough air would do a large ship proud. The flight pattern is typically 'small ship' and the Belle will fly in confined areas. This was proven at the 1952 Nationals where it was flown almost an entire flight within the area bounded by the spot landing circle. One noticeable feature caused by the high incidence angle is that the ship appears to be nose down in flight. The effect is a little startling until you realize that it is not actually underelevated.

The natural choice of receiver was the RK 61 because of its light weight. A Berkeley DE receiver which has a well-earned reputation for its ease of assembly and operation was used. The dust core tuning does a lot to stabilize the operation and improve reliability of the set. The manufacturer's instructions were followed closely.

Control operation is supplied by the Bonner Compound escapement. These escapements are outstanding for their high quality of workmanship and, of course, offer a great amount of control for the weight. Besides the simple 1-2 signaling sequence, the independent throttle control feature makes Banner about top dog in the escapement business today. While it is intended that two-speed be used in the Belle and although both the two needle valve setup for the motor and installation setups for the bleeder valve were tried, to date they have not been installed due to the press of time. However, the ship has been flown with two additional ounces of weight with a performance margin that makes the entire setup only a case of getting the time to do the installation work. The proposed installation is indicated on the plans.

With the CG in the position shown and a careful check on the incidence and thrust settings, the ship is ready for flight. Test-glide several times, checking closely for any turn tendencies. These must be removed before the first powered flights.

For the first flight by all means have the receiver installed and operating. An R/C must be trimmed for straight flight. Any test flying with circular flight is a waste of time. After first flight you can work on the fine trim details. The ship is trimmed to fly straight power off, and any turn under power is corrected with thrust adjustments. "

Supplementary file notes

Article.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction