LAST MONTH WE modified and completed the Hobbistar 60 MK III's wing. During this process the fuselage servo-mounting areas were reinforced, as was the tray mounting. This month we will finish the airplane, and next month we will make a few test flights to get it properly trimmed.

    There is a lot of assembly work to do and not much space, so let's get to it.

Every model builder has his or her own preferred assembly sequence. Mine usually involves starting at the front and working backward but stopping just before installing the main landing gear. Then I work forward from the tail, installing the main gear last.

    Since the fuselage is constantly being rotated and repositioned during assembly, I try to delay installing parts that "stick out," such as the main gear and horizontal stabilizer, as long as possible. This means servo installation is usually the first step. Then I mount the engine.

    However, there is one thing to check before starting power-plant installation. It is a good idea to reinforce the firewall from the inside. As with the servo-mount reinforcement from last month, the Hobbistar 60 is a poor example because the manufacturer has already installed firewall braces. But most ARFs, especially those with a nose gear, could use this extra help.

    A photo shows the installation of 1/2 spruce—not balsa—triangle stock to brace the firewall of a different ARF. Use five-minute epoxy—not cyanoacrylate—for maximum strength and extra positioning time. Make sure the triangle stock does not cover the blind nuts. Usually only two pieces of spruce on the sides are required.

    While you are in there, apply thin cyanoacrylate to those four blind nuts that will hold the engine mount in place. Make sure not to get any adhesive in the center holes.

Click on photo to view large image with caption

Many ARFs use the popular clamp-on mount. How to install an engine in this mount was covered in the "From the Ground Up" installments about engines. (If you do not have this article, it has been reprinted in Sport Aviator's Pri-Fly section at www.masportaviator.com.)

    The basic idea is to center the engine in the mount and position the rear of the engine's bolt plates firmly against the two rear clamping bolts in the mount for proper alignment. If your ARF uses the reinforced fiberglass mount, adjustable or rigid, go to the previously mentioned area of Sport Aviator for mounting details.

    Install the mount onto the firewall. Use the bolts and washers provided, but make sure to use removable thread-locking compound. The clamp-on mounts are strong and allow easy installation.

    However, the mount's metal construction allows some engine vibration to be transmitted to its mounting bolts. Tighten them securely. Remove the two clamp plates and position the engine on the mount in roughly its final position.

Page 1 • 2  • 3 • 4