Yard Stik
The completed airframe before covering (above). The simple structure is strong yet light. Tom is a happy pilot (at right) just after sharing a thermal with a soaring vulture.
The motor should slide on to the stick as a snug press-fit. Drill through the plastic mo- tor frame and secure the motor to the stick with a small screw. (A slide-on motor will need to be shimmed on the thinner yardstick fuselage.) For a firewall motor mount simply trim
the front tip of the fuselage stick at a 6-de- gree angle and glue the ¹⁄₃₂-inch ply motor mount and braces as shown on the plan. The motor will later be screwed to the motor- mount. The battery mount is ¾ × 2³⁄₈ × ¹⁄₃₂-inch
ply. Round the corners slightly with sand- paper and glue to the fuselage stick as shown.
Propeller and wheel diameters vary, so be-
fore bending your landing gear wire, measure your wheels and propeller to be sure you’ll have enough prop clearance. Adjust the land- ing gear length if needed. The landing gear is bent from .062 music wire as shown and
bound to the fuselage with clear monofila- ment fishing line and 5-minute epoxy. Sewing thread or unwaxed dental floss could also be used, but the fishing line dries clear. Attach the .032 music wire tail-skid. Build the wing next. Cut the ribs and the trailing edge sections from stiff ¹⁄₁₆-inch bal- sa. The tip ribs and spars are ¹⁄₈-inch balsa. The spar ends should be cut as shown on the plans for the dihedral angles. A photocopy of parts glued to cracker box cardboard makes a good template for cutting ribs and spar ends. The two outer spars are tapered from ¹⁄₂ inch at rib R-3 to ³⁄₈ inch at rib R-4. The wing is constructed as four separate
panels. Build the tip panels first, from the R-1 rib at the polyhedral break to the R-4 tip rib. Pin the trailing edge to the wax paper covered plan. Put the spar in place and trial fit the ribs, trimming as needed to fit per- fectly. Glue the ribs to the spar and the trail- ing edge, making sure the R-1 is angled with
the spar end. Cut and add ¹⁄₈-inch square turbulator spars and the ¹⁄₈-inch hardwood dowel leading edge. Don’t forget the ¹⁄₈-inch square balsa brace next to R-4. It helps keep the rib from warping when the covering shrinks. When both tip panels are completed, working on one wing at a time, pin the R-1 rib of one outer wing panel to your building board and block up the wing tip 2³⁄₄ inches. Then build the center section panel of the re- spective wing with the trailing edge pinned in place. Add spar and ribs, then turbulator spars and leading edge, gluing each item to the outer panel as you go. Repeat for the oth- er wing, making sure to build a right wing and a left wing. When right and left wings are completed,
pin one center panel flat on the building board and block up the other panel 1¹⁄₂ inch- es at the polyhedral break. The center R-1 ribs should line up. Clamp and glue them.
Trio of Yard Stiksshowing a progression of design and electronics (above left). Built in 2003, the red Yard Stik originally used a 14W brushed motor
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with gear box. It now features an older CD-ROM motor. The yellow and red Yard Stik is powered with a geared brushless system (above right).
FEBRUARY 2012
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