S.E.5a WWI Scout

Model Airplane News, Jul 2003 by Simmance, John

Designed by H.P. Folland, the S.E.5 was a Royal Aircraft Factory singleseat "scout" aircraft. After solving early design and engine delivery problems, Royal Aircraft Factory designated the new plane the S.E.5a. It had shorter, stronger wings and a headrest for the pilot. The S.E.5a soon acquired a formidable reputation for downing enemy aircraft.

Maj. James Byford McCudden, V.C., flew S/N B4863-"aircraft G" model. It had a geared Hispano-Suiza engine with a 4-blade propeller, short exhaust pipes and a steel-tube undercarriage. Striving for perfection, McCudden often modified his own aircraft, and he scored 53 "kills" with it.

The model S.E.5a is fairly complicated to build and isn't for beginners but for advanced builders. I first flew my design in Colorado at 6,000 feet above sea level during the summer of 1996. Spanning 71 inches, it weighed slightly more than 17 pounds and was easy to fly. I originally drew it on paper, and then I redesigned the model in CAD as a lighter structure weighing about 15 1/2 pounds, depending on the engine used. With a wing area of 1,862 square inches, expect a wing loading of around 19 ounces per square foot.

CONSTRUCTION NOTES

This model sacrifices simplicity for construction authenticity to resemble the full-scale aircraft. Skilled modelers won't need much in the way of detailed instructions; t those who do should visit the Model Airplane News "Click Trip" site. If you decide to cut your own parts from the patterns given on the plan set, do it this first and make all the wire and metal parts at this time, too. Alternatively, order the laser-cut plywood and balsa parts package. It doesn't include any 3/8 or 1/4-inch ply parts; you make them by laminating 1/8-inch-thick pieces of plywood together to make 1/4- and 3/8-inch thick parts.

* Fuselage. The landing-gear design doesn't easily allow the lower wing to be removed to allow access to the radio compartment. Therefore, for access and to preserve the cockpit area for scale details, the fuselage is split at the upper longeron level, and the entire upper fuselage can be lifted off from the rear of the cowl to behind the cockpit. This part is secured by four long bolts that pass through the bottom of the fuselage, and it supports the cabane strut structure. This arrangement provides maximum airframe strength under flight loads.

Before you start to build the fuselage, build the upper wing center section because you'll use this assembly later to position the cabane struts. The fuselage is formed around a central self-aligning box structure; the engine firewall is slanted to provide the correct side thrust and downthrust. The design incorporates a cooling duct to carry hot air from the engine compartment out through the fuselage between the undercarriage legs.

* Tail surfaces. The tail surfaces are built flat over the plan with half ribs. You'll add the undersides later and sand them to an airfoil shape. The stabilizer halves slide over tubes that are secured in the fuselage. The stab halves are held in place on the tubes by the rigging wires. To simulate the flying surfaces' narrow frames and trailing edges, 1/32-inch ply parts are edged with narrow strips of balsa. The effect is quite convincing when the structure has been covered. The fin, rudder and elevator plywood profiles have cutouts to accommodate nylon hinges; this minimizes the need to cut hinge slots in the stabilizer and balsa tail block.

* Wing construction. The wings are best built on a jig; go as far as you can toward completing them before you remove them from the jig. Make the wingtips out of two laminations of 1/32-inch ply that you form to the camber shown on the plan. If the wingtips aren't cambered, they won't fit properly.

The ailerons are built as part of the wings and then cut free and finished; small Robart Hinge Points secure them to the wing. To fit the servos inside the thin wings, I show custom low-profile servo mounts. With small changes in dimensions, they'll fit any small servo. The S.E.5a is a big model, but it flies slowly and doesn't need huge, high-torque servos.

* Cockpit detail. The cockpit is wide open and benefits from detailing. I installed cockpit seat supports and a wicker seat made out of cane and raffia, which looks very authentic. The pilot seat can be set on the supports to accommodate a hips-to-head pilot figure. The "Vickers gun butt" protrudes into the cockpit over the left of the instrument panel.

* Final assembly. After the model has been built but before it has been covered, install the radio and its components. Position the radio gear as appropriate. I used rubber bands to mount my receiver and battery on the tank compartment cover, and I mounted the switch and charger jack inside the cockpit. I also ran the receiver antenna through a tube in the fuselage; it's invisible and functions well.

A computer radio is needed to program differential aileron and to coordinate rudder/aileron mixing. At first, I used glow heat on the engine when it was idling, but it tended to speed up the idle after the engine had been running for a long time, so I removed it. I used a microswitch that engages at low throttle. A newer, onboard glow system that senses when the plug is cooling, regardless of engine speed, would work better.