Tyro Trainer (oz13336)
About this Plan
Tyro Trainer. Radio control powered glider trainer model.
Quote: "A glider is almost a perfect R/C trainer, but there's nothing to keep it in the air while you're practicing. Add just enough power to make it climb gradually, by itself - now you do have a trainer!
The Tyro Trainer is a powered R/C training glider designed to meet three objectives:
1. Smooth, slow, stable, and forgiving flight characteristics so that a beginning RCer with some free-flight experience can handle it from the start, including launchings and landings.
2. Quick and easy conventional (balsa and covering) construction.
3. Low cost airframe and engine.
These objectives have all been met.
Wingspan is 74 inches, overall length 40. Power is a Cox Babee .049. The prototype weighs 30 ounces with Heath GD-19 radio equipment. The wing loading is 9 oz/sq ft, resulting in a low stalling speed, and corresponding low approach and landing speed. Nevertheless, the airplane is rugged, and easily repaired when damaged.
Rudder and elevator control are used. The generous dihedral provides lateral stability so that the airplane will fly hands off, even when trimmed to glide in large circles. The .049 engine provides adequate power to take it up several hundred feet on a tank of fuel.
The engine is mounted on a removable forward hatch, eliminating the need for ballast. For powerless soaring, a plain hatch and some weight in the nose is substituted. Standard size materials are used throughout construction. Scraps left from cutting out the fuselage sides are used for the stabilizer frame - a single sheet of 3/16 x 2 x 36 balsa makes the elevators and rudder, with the leftovers being used to make the fin and sub-rudder.
CONSTRUCTION: All wood is balsa unless specified otherwise. All glue used in the prototype was Franklin Titebond except when epoxy is called out, when Hobbypoxy #1 or #4 is used as specified.
WING: The wing should be built first so it can cure completely while the rest of the glider is under construction, and any warps that develop can be worked out. A secondary reason is that this writer finds wing construction the least enjoyable and most tedious phase of model building, and tries to get through it before his enthusiasm wanes.
The original wing was built with 1/16 sheet ribs and the leading edge sheeting on the top surface only. It was unsatisfactory due to recurrent warping, and was replaced (after more than 80 flights) with the one shown on the drawing, using 3/32 sheet ribs and 1/16 leading edge sheeting top and bottom. This wing has proven to be much more warp resistant.
A third variant suggested for consideration would retain the top and bottom leading edge sheeting, but utilize 1/16 sheet ribs with 1/16 x 3/16 cap strips top and bottom. This would be even stiffer than the second design, and would result in smoother covering. If this configuration is chosen, make all the C ribs like B, to allow for the cap strips.
Cut and notch wing ribs by your favorite method. For this model a 1/16 plywood rib template was made; and ribs traced with a fine ball point pen. For A and B ribs, trim C ribs to accommodate the 1/16 center section sheeting. Note that A ribs are each made in two pieces to accommodate the spar dihedral joint.
Start the wing by notching the trailing edges 1/8 deep for the ribs. Note that no notches are used at ribs A and B, and at the tip ribs. An easy trick for notching is to use the edge of a fine flat warding file. A few trials on balsa scrap will show which file is right..."
Tyro Trainer, Model Builder, January 1975.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
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