F-84 Thunderstreak (oz6565)

 

F-84 Thunderstreak - plan thumbnail image

About this Plan

F-84 Thunderstreak. Radio control scale model for .049 IC ducted fan.

Quote: "Republic F-84F Thunderstreak, by Walt Musciano.

THE MOST notable undertaking in model aircraft design since the end of World War II has been the ducted-fan. This novel idea has enabled modelers to build and fly scale jet fighters without unsightly propellers or the heat problems of the resonant jet engine. Refinement of the ducted-fan concept has experienced a remarkable surge by model designers and manufacturers during the past decade and it appears to be the fastest growing activity of this great hobby.

Ducted-fan powerplants produce less thrust than propeller powerplants of the same displacement. This makes it important to be very weight conscious during their design and construction.

This model is a simple 1/2-A powered, semi-scale sport flyer which utilizes light construction and is the ideal subject for an initial ducted-fan scale project. It is for this reason that I have taken extra care to describe the construction steps more thor-oughly than usual.

Midwest Products produces a series of ducted-fan units in various sizes. Midwest is the first to market a selection of ducted-fan units for .049, .20, and .40 cubic inch displacement engines, enabling the model builder with limited experience to try his hand at simple R/C ducted-fan-powered model airplanes. The design of the Midwest Products Axiflo ducted-fan units includes an integral streamlined fuel tank and a longer duct than most other ducted-fan units. The Midwest Axiflo duct encloses not only the five-bladed fan but also the engine, engine mounts, and part of the fuel tank as well. This simplifies the inlet duct and tail pipe installation. The Midwest Axiflo RK-049, RK-20, and RK-40 ducted-fan units are sold in kit form and the prefabricated components are easily assembled.

Needless to say, you must use very lightweight and compact R/ C equipment in this project. The need for lightweight servos, receiver, and battery pack is self-evident; however, the necessity for compact units is equally important because most of the fuselage volume is occupied by the air intake duct, ducted-fan unit, and air discharge tail pipe, and there's very little space left for the R/C equipment. This model is fitted with two R/C channels operating the elevator and ailerons.

The tremendous advances in engine technology have made the present day engines, such as the Cox Tee Dee .049 and .051, powerful and light, and, when combined with the efficient Midwest Products R K-049 ducted-fan unit, we have a good formula for success.

An overwhelming majority of ducted-fan-powered model airplanes are scale replicas of full-size jet fighters and it's very difficult not to agree with this selection. This project is no exception and is the Republic Thunderstreak, a well-known US Air Force jet fighter of the '50s. My selection of this plane was governed by two basic requirements I established as being necessary for this lightweight, low-powered, initial ducted-fan model: first, the plane couldn't be a modern jet fighter with angular, rakish, space-age contours, but rather an early jet fighter that combined the look and feel of propeller-driven aircraft with the present-day realities of jets. Second, the wing had to be shoulder-located atop the fuselage or in mid-fuselage, because the model was to be constructed without landing gear in order to reduce weight and air resistance, as well as to improve appearance in flight, therefore hand-launching was a necessity. This made it very important to be able to grip the fuselage without worrying about interference from the wing.

In building the model, use cyanoacry-late adhesives and carefully select all wood for maximum strength and light weight. It's always good practice to cut lightening holes in the structure wherever possible without sacrificing strength. In this way material that's not contributing to the model's structural integrity can be eliminated. All plywood should be light plywood and never use thick or heavy material when thinner or lighter material will do. Sand all wood with a sanding block before cutting to shape.

Before starting construction, very carefully assemble the Midwest Axiflo RK-049 ducted-fan unit, following the manu-facturer's instructions.

Because lightness is so important, you can lighten the Axiflo unit somewhat by replacing the red fiber duct skin, which is supplied with the kit, with 1/64 plywood. Use the supplied duct skin as a pattern when cutting the plywood to shape. Roughen the stator pins as the kit recommends and set them in place in the stator mount ring with thick cyanoacrylate. Next form baking soda fillets at the stator bases and wet these with regular cyanoacrylate. This should produce a light but strong stator installation.

As previously mentioned, this model is hand-launched and, becauseducted-fan-powered model airplanes accelerate more slowly than propeller-driven models, the launch must be of fairly high speed. This fast launch has a detrimental effect on the engine operation, causing it to slow down and often stop during the launch. The problem is caused by the inertia of the launch slowing the fuel in the long tubing from the tank to the engine, which is located forward of the tank. This can be overcome by converting the Cox Tee Dee engine so the crankcase pressurizes the fuel supply. The engine should be converted to the crankcase pressure type fuel system as illustrated on the drawings..."

Direct submission to Outerzone.

Update 30/07/2019: Replaced this plan with a clearer copy, thank to Circlip, RFJ. Also added article, thanks to RFJ.

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F-84 Thunderstreak - completed model photo

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