Tools and Building Order: In addition to adhesives, you will need a flat, level work surface that is at least 6 feet long and 2 feet deep. Basic tool requirements include a hobby knife, a supply of sharp No. 11 hobby-knife blades, at least one 1/2-inch-wide hobby chisel-blade knife, epoxy application brushes, 10 clamps (black steel binder clips work well), a combination square, and a hobby iron and trim iron meant for applying plastic film coverings.

    Performing a few modifications requires wood, an extra servo, new nose gear, and a few other items I'll outline later.

    A photo shows the Hobbistar 60 Mk III as it comes out of the box. There are many more parts here than in an RTF kit. The major surfaces are prebuilt and precovered, but who is going to put all these little components in place? Small pieces are taped to the wing and fall off when the tape is removed. That doesn't happen with RTFs!

    Yes, RTF models can spoil us. But ARF construction is easier than it looks, and it's more fun than RTF assembly.

    A good place to start is the wing. A completed wing is required before you align and mount the tail surfaces onto the fuselage. Mounting one aileron servo and constructing simple aileron control rods is good practice for completing the more complicated triple-servo and control-rod installations that the fuselage requires.  

Click on photo to view large image with caption

Let's start building. As with all modern ARFs, the Hobbistar's photo directions are amazingly complete and contain many helpful tips. But since this article is meant to illustrate ARF assembly, I'll repeat some of them.

    Assemble the wooden wing spar. Most ARF wing spars are two to three laminated pieces for extra strength. The Hobbistar uses three pieces. Laminate the pieces together using 30-minute epoxy for maximum strength and clamp in place. The spar assembly is clamped to a large square to ensure that the spar is straight. Getting it aligned and straight is critical for wing-half alignment.

    While the spar is curing is a good time to plan wing modifications. As do all ARFs except the Midwest Aerobat, the Hobbistar 60 uses a single servo, mounted in the wing's center-section, for aileron control. That installation is next.

    One of the greatest advances in our sport during the last 15 years has been the development of the two-servo aileron control system. I'll cover this installation next month, but I will note any changes required along the way.

    The Hobbistar 60 employs Mylar laminate hinges for all control surfaces. Use those; competition experience has proven them to be reliable and durable.

    Test-fit the hinges into the aileron and attach to the wing. Mark the center of each hinge on the wing and aileron. Drill a 3/32-inch hole at "hinge center" in the wing's TE and the aileron. This hole allows the thin cyanoacrylate to reach every part of the hinge.
 
    Before attaching the aileron, remove enough wood from around the torque rod at the wing's center-section that it can move approximately 70¡ in each direction. Place two pins in the center of each hinge to ensure hinge alignment, and insert the hinges back into the aileron.

    Put five-minute epoxy inside the aileron's torque-rod hole and along its rod channel. Bevel the aileron's rod channel near the hole, making room for the rod's curve as it makes the 90¡ bend. This allows the aileron to fit tightly against the wing's TE. This is important, as you will see later.

    Putting epoxy inside the aileron torque-rod hole reinforces the balsa. Without epoxy, the metal rod gradually crushes the surrounding wood. The aileron then loosens slightly, and you start to hear a vibrating sound called "flutter." The ailerons vibrate rapidly, the servo gears strip, and soon you are flying a rudder-only aircraft. This often is not as much fun as it may appear to be.

    Once you have applied the epoxy, attach the aileron to the wing. Do not get epoxy inside the hole where the torque rod exits its TE wing bearings. Putting a small dab of petroleum jelly at this point will prevent a problem.

    Press the aileron tightly against the wing. Remove the pins and press again. The TE should fit tightly against the aileron. If you plan to use only the center aileron servo, deflect the aileron 30¡ in one direction while pushing the aileron's center against the wing. Apply a few drops of fresh thin (only) cyanoacrylate to the center hinge.

    Wait 30 seconds, move to the aileron section near the wing's center, and repeat. Do this for all hinges. Remember to hold the deflection. Turn the wing over and do the same on the other side of each hinge. If you plan to use flaperons, deflect the aileron all the way until its bevel hits the wing's TE. Glue the hinges. Full deflection usually causes a roughly 1/16-inch gap between the wing and the aileron.