Crane (oz14433)

About this Plan

Crane STOL. Radio control sport model, for OS Max .45 FSR engine.

Quote: "AN R/C STOL. The Crane was designed to investigate a variety of aerodynamic devices. The results were fascinating! by Andy Lennon.

DESPITE THE ready availability and reliability of radio equipment offering more than four basic channels, R/ C modelers seldom utilize the extra control capacity for more than retractable landing gear. The use of aerodynamic devices such as flaps, variable-pitch propellers, slots, spoilers, etc, is not unusual on today's full-scale light aircraft but has not seen much development in R/C models.

The Crane was based on a proven design, the Gull, which, in turn, was a complete redesign of the successful El Seven . It employs a variable-pitch propeller, full-span leading edge slots, full-span slotted flaps, spoilers for roll control, and an inverted semisymmetrical-sectioned, all-moving, horizontal stabilator, the latter partially leading-edge slotted.

It was test-flown in late June 1982 by J.S. (Jack) Schroder, a director of the Montreal R/C Club, of which I'm a member. Jack is an R/C pilot of consummate skill and in real life a retired executive jet captain. His assistance and constructive criticism are deeply appreciated. Confidentially, I think he really enjoys the challenge of flying my 'creations.'

The Crane flew right off the board, requiring only increased spoiler angle accomplished by moving the mini-links one hole down on the spoiler horns.

During the next five weeks many flights were made and two problems surfaced. The first was a too-narrow tread on the main landing gear, leading to tipping in moderate cross winds unless care was taken.

The second, and more serious, was a tendency to enter a shallow dive at top speed in coarse pitch and maximum rpm. This was controllable. Up-elevator, beyond the limits of elevator trim, corrected the situation, but the tendency was disturbing and finally lead to disaster.

In late July we made a flight to further explore this diving phenomena, but the model failed to respond to the up-elevator command and continued its shallow high-speed dive into the ground. Both transmitter sticks were fully back and there was no time to deploy the flaps.

Examination of the radio equipment indicated it had survived this crash and was working. The motor had slowed to idle judging from the prop, on which only one blade was damaged, as was the prop hub. The fault was traced to broken gears in the elevator servo.

The impact was so forceful that of the model's structure, only the slats, flaps, and wing tips were salvageable. The motor required a new crankshaft.

Back to the drawing board. I made design changes to correct the faults and built a new model, Crane II, that flew in early September..."

Quote: "With construction, my personal preference is to make all parts before assembly is initiated, starting with metal parts, then plywood and balsa, and lastly any component requiring fiberglass and epoxy.

You have your own preferences, so you'll do it your way. There is, however, a sequence of assembly to follow that makes the job easier. For example, in bending flap torque arms in 3/32-inch music wire, put on the brass bearings before the final bends. It's hard to force brass tubing to flow around a 90° bend!

Assemble the slotted flaps first. The mid-span flap support locates the rib in the wing to which it must be epoxied, as you'll see in photo 4. A left and a right are needed.

Silver-solder the spoiler arms to the torque tube after sliding on bearings and stops, and solder the stops where indi-cated. Make left- and right-hand versions.

Assemble the wing halves - again, left and right - locating flap support ribs as indicated above (photos 1 and 2). Sub-assemble the three components of the center section main spar. Figure 3 shows wing assembly with dihedral; make sure that both wings' leading edges are in line. Sub-assemble the stabilator pivot and control horn in the solid balsa of the center section and proceed to assemble and skin the stabilator as shown in photos 5, 7, and 8.

Assemble the fuselage balsa bulkheads (photo 14) and apply the landing gear fairings on all three legs, as described in the drawings (plate 1) and in photos I 1 and 12. The lower legs will need balsa 'elbows' at the wire bends, cut from block balsa..."

Crane, MAN, December 1983.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ, Pit.

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