Phony Folkerts (oz10299)

About this Plan

Phony Folkerts. Radio control FAI pylon racer model. Wingspan 56 in, wing area 605 sq in, for .40 power.

Quote: "Phony Folkerts. The next time you get fooled on the FAI circuit, it could be by a real phony. Although its looks are somewhat fake, its speed around the course is for real. Phony Folkerts, by Bob Root.

In deciding to build a competitive new FAI racer, the design requirements seemed to suggest a minimum sized 'thing' configuration. However, I have always felt that model racers should look like full-scale airplanes. The model presented here as the Phony Folkerts represents a compromise between these extremes. Although the model retains some of the basic outlines of the Folkerts SK-2, and SK-3, it cannot be suggested that it is stand-off scale, unless one stands off 400 feet to watch it race.

However, racing is what this design does best. It has been quite competitive in the Northwest in FAI, and finished well at the 1973 NATS, with Jim Booker and Bob Root placing third and fifth respectively.

The Phony Folkerts fuselage cross section was minimized for low drag by designing the basic fuselage to be just large enough for the necessary equipment. The FAI width and height requirements were then faired into the small cockpit area as smoothly as possible. A fiberglass fuselage was incorporated to minimize structural volume, while allowing complex curvature and rapid construction. Although this type of construction deviates from the author's usual methods of wood construction, the results have proven worthwhile. A high quality, lightweight, fiber-glass fuselage is now readily available.

While the design and construction of the original plug, mold, and model took all winter, the second one was built in two weeks by fellow competitor Jim Booker. The fiberglass work and much of the original plug and mold building techniques were supplied by Tony Howard. He has been producing high quality, limited production, fiberglass kits for several years. Either a glass fuselage, or a complete kit, is available from Miniature Aircraft Designs. See details at the end of this article.

A few notes are included for those who may be interested in building a wooden version, but the equipment room or the cross-sectional area will have to be compromised. The complex fuselage shape does not lend itself well to wood construction.

Construction is shown for four separate types of landing gear. Violett Aero Modeling Corp retracts were used on the original model. Although this plane weighed less than 4-3/4 lb, very careful building was required. A separate article on installation of the retracts, with details of the full wheel doors, appears in this issue of AAM.

Jim Booker built his model with belly mounted wheels and 'outrigger' stabilizing skids. This landing gear is simpler and lighter than retracts, but not as realistic. Jim has successfully flown this model without the skids, but the minimum skid length required for reliable takeoffs has not been determined. They shouldn't be too long, or they will cause excessive drag during takeoff.

Typical balsa fuselage cross sections are included on the plans as an aid to wood construction. A sketch of one possible building method is also shown. The curved upper and lower parts of the fuselage can use planked construction or formed balsa blocks. Form the engine compartment with balsa blocks or epoxy and fiberglass covered foam blocks.

If the above is not too clear, it is suggested that the reader refer to the author's Firecracker FAI racer article in the January 1972 issue of AAM. A complete discussion of a wooden fuselage is included. If a fuselage is constructed from scratch, it is important to note that the minimum width and height (occurring at the cockpit on this model) must be 3-3/8 in and 6-15/16 in. The basic fuselage is 2-1/4 in wide, with the extra width occurring only in the fairing above the wing.

Construction. If a fiberglass fuselage is used, the first step is to file a Tatone No. 3 mount to fit. The front end must be filed somewhat to fit within the fuselage. Depending on the engine, the engine lugs may also have to be narrowed. An HP will fit with a minimum amount of material removal. The ST G-40 requires quite a bit of filing.

For maximum adhesion, polyester resin should be used to bond the fire-wall and bulkheads to the fuselage. Use a fillet of glass matt or micro-balloons, mixed in resin for reinforcement. The front wing mount bulkhead should be drilled for the 1/4 in hold-down dowels before it is installed in the fuselage. The mating 1/4 ply plate, which is later glued to the front of the wing, should also be drilled at this time, to insure that the holes match. However, the aft wing mount should not be drilled and tapped until the wing is completed. Note that the rear wing hold-down is bonded and screwed to the aft bulkhead before installation in the fuselage. A layer of fiberglass cloth on each side of this hold-down will insure that the tapped hole will be durable..."

Phony Folkerts, American Aircraft Modeler, July 1974.

Direct submission to Outerzone.

Update 22/3/2022: Added retract installation article, from AAM, July 1974, thanks to RFJ.

Quote: "Real Retracts for the Phony Folkerts. By Bob Root.

The retractable landing gear installation used in most models suffers two disadvantages, both of which are undesirable in an FAI racer. (1) Retracts usually result in excessive weight, and (2) the open wheel wells cause considerable drag. A typical model retract installation, with open wheel bays, reduces drag by only about 25% of that which can be achieved if the wheels are completely faired, ie close-fitting doors.

A fully enclosed retractable landing gear system was developed, in an attempt to produce a realistic FAI pylon racer with less drag than the 'thing' airplanes, with their fuselage mounted wheels. The following article describes the installation of Violett Aero retracts in an FAI racer wing. Doors are used to completely seal the wheels when retracted. The landing gear and doors are powered by one 180° servo.

The basic ideas presented here could be used to install other types of gear and actuation systems. However, the Violett gear have the advantage that there is considerable pushrod movement available at each end of the throw, with no gear movement. The method used to drive the inner doors takes advantage of this to get the doors moving ahead of the wheels.

The drawing shows the basic characteristics and components of the system. The servo arm is modified as shown and bolted to two extra arms, with the proper spacing to prevent interference between the four push rods. The retractable gear pushrods are attached to a 1800 servo in the normal manner. The inside door actuating pushrods are attached to the servo at approximately 900 to the retract arms. Therefore, the doors open in the first 900 of servo motion, allowing the wheels to come out. They close most of the way in the second 90° of motion. With the gear down and locked, the doors are almost closed, resulting in good ground clearance.

It can be seen in the drawing that the gear and doors are actually hooked at angles slightly different from 1800 and 900. This is done to insure that the doors are open as the gear extend. If another type of retracts are used, these angles will have to be changed, resulting in more door extension when the gear are down.

The outside doors are simply attached to the landing gear struts with thin wire clips, as shown. The strut is then free to move aft in a hard landing, without disturbing the door.

The following method can be used to produce close fitting doors, which match the wing contours. First, the landing gear mounts should be installed in the cores. These are small plywood boxes, per Violett's recommendations. They seem to work well, and they are light and easy to make. Next, the doors are carefully cut out of the wing skins..."

Supplementary file notes

Article.
Article (retracts).

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