P-38 LIGHTNING

Model Airplane News, Feb 2005 by Bell, Rick, Davisson, Budd

HOBBY LOBBY

Innovative twin-tail fighter

ANY FAN OF WW II WARBIRDS IS BOUND TO find the Lockheed P-38 exciting. Its distinctive profile was a revolutionary design in its day, and it performed many roles as it served in all theaters of war. It was the main mount of many top U.S. aces in the Pacific theater, including Major Richard Bong, who shot down 40 enemy aircraft. P-38s were also used in the famous mission that intercepted and shot down Japanese Admiral Yamamoto-the man behind the Pearl Harbor attack.

I've wanted to build and fly the P-38 for many years, but the thought of trying to keep two glow engines running in sync has always scared me off. I've seen many P-38s do the deadly one-engine dance and crash, so when Hobby Lobby Intl. debuted the electric-powered Flying Styro kit of the Fork-Tailed Devil at the 2004 Southeast Electric Flight Festival, I knew that my prayers had at last been answered!

KIT CONTENTS

The kit is a combination of an RC model and a well-detailed static display model.The wing halves, stabilizer, fuselage nacelles and center pod are made of molded Depron foam and are factory painted. When you open the box and see the many vacuum-formed parts, don't be put off, as most of them aren't needed for a flyable model. The kit also includes a 14-page, photo-illustrated assembly manual, CNC-cut lite-ply parts, waterslide decals and four colors of touchup paint. For maximum strength, the Lightning is designed as a one-piece model. The battery and receiver are accessed through the bay for the nose gear, and they are covered with a removable hatch. The rest of the radio system is in both fuselage nacelles; you'll need to add a couple of servo-extension leads and Y-harnesses to reach the receiver. The landing gear is for display only; it isn't recommended that you fly the model with the gear attached.

POWER SYSTEM

Many options are available here, and you must have the power system on hand before you start to build. Two brushed Speed 300 motors geared 7.7:1, a single ESC and a 7- or 8-cell NiMH battery will get you airborne with minimal expense. I really wanted to bring the Lightning to life, though, so I decided to use two Axi 2208/34 brushless outrunner motors and two Thunder Power 2-cell, 1300mAh Li-poly batteries (wired in parallel for a total capacity of 2600mAh). Since two brushless motors can't be operated reliably from a single ESC, I used two Jeti Advanced 8A brushless ESCs. I also wired the motors in parallel (see the "Powerlines" column in the June 2004 issue of Model Airplane News for more information) and used a Y-harness to connect both ESCs to the receiver. I disabled the battery-eliminator circuitry (BEC) of one of the ESCs by removing the red wire (power) from the receiver plug.

LET'S BEGIN!

Because the P-38 is a lightweight foam model, select your adhesives carefully. I used a combination of UHU For foam-safe contact cement (available from Hobby Lobby), Bob Smith Industries foam-safe thin CA and kicker and a little 5-minute epoxy. Basic assembly goes quickly; the level of detail you add to the model is up to you.

Start the assembly by joining the wing panels. The wing is molded in halves that contain a balsa spar for strength. A balsa dihedral brace is glued to the rear of the spars. To join the panels, I used a thin smear of epoxy here and on the wing roots. The ailerons are prehinged, and the torque wires for them are in place.

The center pod now fits to the wing. Be sure to accurately center it, as it will be used to position the fuselage nacelles later. Use a couple of large T pins to hold the pod in place when you mark the wing for the center section cutout. After the pod has been glued into place, add the balsa floor in the nose of the pod; the rear edge of it is glued onto the leading edge of the wing.

Fuselage nacelles Before the nacelles are installed on the wing, the motors have to be mounted to the firewalls and glued into the nacelles. The precut firewalls are designed for the 7.7:1 gearboxes and Speed 300 motors, but two lite-ply discs are supplied for other motor configurations. I used Axi radial mounts to attach the motors to the center of the discs and then glued them to the firewalls. When 1 fitted the prop hubs to the prop adapters, I ran into a slight problem: the holes are too large. A 6mm-o.d. bushing is needed for each prop hub to properly center them. I found that by shrinking two layers of 3/16-inch heat-shrink tubing on the adapter shaft, the hubs were perfectly centered. After placing the firewall/motor/ESC assemblies in the nacelles, use the spinner backplates as a guide to position the firewall. I placed 1/32-inch balsa shims every 90 degrees to evenly space the backplates before gluing the flrewall into the nacelles.

The nacelles are now glued onto the wing along with the stabilizer. The center of the nacelles is spaced 6 3/8 inches from the center of the pod. Draw reference lines on the bottom of the kit box to use as a guide.

* Radio installation Three servos are needed for the ailerons and elevator; I used Hitec HS-55 sub-microservos. They are installed in recessed ply mounts in each wing panel, and the superchargers are cleverly disguised access hatches. I used small, rare-earth magnets to hold them in place. The other radio components are installed as follows: I used double-sided tape to secure the ESCs in the nose of the nacelles, attached the batteries to the underside of the balsa floor in the center pod and fastened the receiver to the underside of the wing in the center pod with Velcro® and fastened the receiver to the underside of the wing in the center pod. There's plenty of space to thread the Y-harnesses and servo extensions through the wing and into the center pod.