Thermal Queen (oz11047)
About this Plan
Thermal Queen. Rubber competition model.
Quote: "A 54 inch Queen's Cup Model. Thermal Queen, by Ray Jessop.
WITH the advent of the Queen's Cup Contest in 1948 I decided to have a crack at one of these outsizes in rubber models. After much consideration I decided to build an enlarged version of my 1947 Wakefield model which had proved a consistent performer.
About a week before the 1948 contest, my model was finished; it had a streamlined cabin fuselage with a high wing position, 54-in polyhedral wing, 18-in diameter Wakefield prop with 4 oz motor.
The first two flights gave an average of about 2-1/4 minutes. When it came to the final flight, maximum turns were applied. This was too much for the model, as it climbed away steeply and then stalled into the ground, thus ruining my chances.
Early in 1949 I decided to start on a new Queen's Cup model. This also had a streamlined fuselage and I managed to get the weight down to 6-1/2 oz so that I could use a 20 in dia prop with 6 oz of rubber. This model proved a complete failure.
I finally decided that the fully streamlined model was not the answer for the Queen's Cup specifications, and decided to build a purely functional model having the following considerations in mind.
1. A high power-weight ratio is necessary to obtain a high rate of climb, a 50/50 ratio with 6 oz motor and 6 oz airframe being optimum. Although a 6 oz motor has a terrific amount of power to handle, it can be wound using a large winder, a strong arm and a weak mind.
2. High strength with lightness is necessary, so the model wants to be as simple as possible.
3. The model must have the utmost stability to handle the enormous power.
4. That the prop be of small dia with fairly large pitch and blade area. A free-wheeling prop of this size produces drag of no small measure and is very prone to damage; therefore a folder is desirable.
5. A model of this size lands rather heavily and requires an undercarriage of very large proportions, which would create much unnecessary weight. Then why not retract it and thus reduce drag and keep the weight down?
6. Last but not least, an efficient dethermaliser. All these points were considered in the design which placed second in the Queen's Cup 1949 and which is presented here.
This model exceeded my expectations, being extremely stable with a high rate of climb. The glide is very fiat and more like that of a good glider than of a rubber model. In the 1949 contest, it averaged approximately 2-3/4 minutes with no noticeable thermal assistance and using only 700 turns, whereas the maximum was near 900.
Fuselage. (a) Construct basic box fuselage in usual manner using very hard 1/8 in for longerons. (b) Add sheeting, wire fittings and all diagonal braces. (c) Cover basic fuselage with Silk Span or some other strong tissue, water spray and give four coats of dope. (d) Assemble wing mount in correct position with all gussets, wing pegs, etc, as shown, cover sides with 1/16 sheet. (e) Construct undercarriage, cement the celluloid hinge point reinforcement patches in position..."
Thermal Queen, Aeromodeller, May 1950.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
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