Yardbird (oz14653)

About this Plan

Yardbird. Radio control sport model, for electric power. Wingspan 49-1/2 in.

Quote: "Electric R/C. A gentle and forgiving airplane that can literally be flown almost anywhere. Yardbird, by Randy Randolph.

Most of us need no reason to build a new airplane other than to replace one that has had some difficulty with the ground. Most of the reasons we give are just justifications anyway. In the case of the Yardbird, there was a need. Some time ago, I was able to buy, at a ridiculous price, an electric Chipmunk with all the accessories necessary to produce flight. My intent was a nice quiet airplane to fly in the front yard at home. On the second flight from the street in front of my house, I snapped it into the cement - exit Chipmunk. The motor, battery, pushrods and devises were salvaged and became the basis for Yardbird, which does all the things the Chipmunk was supposed to do but much better.

Yardbird looks like a dog, but everything comes together as it should to pro-duce a fine flying, gentle and forgiving airplane. With a full 15-minute charge from the quick charger, it will fly for a minimum of 5 minutes; that's double the flight time I was ever able to get with the foam airplane at our regular field under ideal conditions. A typical flight will produce a climb to about 300 feet, a few loops and rolls, then a slow descent to a rather abbreviated landing. The small wheels make the landing roll short, which keeps the airplane away from the curb in street landings. More often than not, the hot rooftops provide thermal help and the flight has to be brought to an end because of excessive duration and height.

It is not a good idea to allow the wind-driven prop to charge the batteries in the wrong direction for any length of time. A servo-controlled switch would eliminate this problem and will probably be added in the future.

Yardbird is a relatively easy airplane to build and will go together rapidly once the parts are fabricated. While building, please think light - one more ounce will make a difference in the performance, so resist the urge to beef it up.

Wing: Make a template and use it to cut out 26 ribs from 1/16 sheet balsa. Trim 1/16 in from the top and bottom of 4 of them and widen the spar notches to accept the dihedral braces. These are the center section ribs. Strip the spars from hard 3/16 stock and the trailing edge sheeting from medium 1/16 sheet. Cut the spar and trailing edge webs from soft balsa, going with the grain as shown. Make 8 dihedral braces and I trailing edge brace from 1/16 plywood. If glow power is to be used, only 4 dihedral braces are necessary, 1 for each spar.

Build the wing right over the plan by covering it with waxed paper or the plastic film from a dry cleaners bag. Pin the 2 bottom spars and the bottom trailing edge sheet in place over the plan and assemble the ribs to them. Start at the second center section rib and add ribs and webs out toward the tip; the webs only go out 5 bays from the center. Bevel the center rib end of the 2 webs at the center section and add the center rib. It should be set at a slight angle to account for the dihedral. Add the lop spars and the leading edge; do not install the top trailing edge sheeting at this time. Glue the soft 1/8 sheet tip in place with its gussets and remove the wing half from the plan. Turn the plan over and build the right hall wing in the same way on the back of the plan.

When both wing halves are completed, sand a slight bevel into the spars at the center by elevating the tip 2 in and using the side of the bench as a guide for the sanding block. Join the halves at the center with the dihedral braces, and hold them in place with clothespins until the glue sets. Incidentally, I use model airplane cement on most or the structure but Titebond is best for gluing the dihedral braces to the spar joints. Once the trailing edge brace is in place, the top trailing edge sheeting can be added and the center section sheet installed, which goes between the spars both top and bottom..."

Direct submission to Outerzone.

Quote: "I had to send this one, I built one as soon as I got the magazine. With an Astro 05 and the best Sanyo Red Cell SCRs it flew nicely. No ESC, I used a simple electronic on/off switch. Now with an outrunner and Lipos it's even better. I highly recommend the addition of anti-warp diagonal bracing on the tail surfaces, I had to add them and then recover the stabilizer at some point. Features the Randy Randolph airfoil, which he seems to use on every design with good success! The scan is a 400% enlargement of the magazine page, I never had full size plans. Attached some pictures [main pic, 003-005]. Dave"

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