Dick Sarpolus' F-86 Sabre Jet EDF
Designed by Dick Sarpolus.
Free plans from Fall 2012 Park Pilot.
Building profile models has been popular almost as long as airplanes have been around. The realism lost with the slim profile fuselage is a fair trade for the ease and speed of building the model. Another tradeoff is using a propeller to power a jet aircraft. We make that sacrifice because putting a propeller on the front or aft end of a jet model is usually easier and lower in cost than any other way of simulating jet aircraft power.
This F-86 Sabre Jet was originally designed with an electric motor and propeller in the nose, and I was happy with it. It’s a well-known fighter that looks cool with its swept wings and jetlike styling, even with the “stick” on the nose.
When I showed the design to Jeff Troy, Park Pilot’s editor, he suggested trying an alternate version using an electric ducted fan (EDF) for power. I checked with BP Hobbies and selected the 70mm unit made by ELE, which came with the motor. This seemed to be the largest setup that I could fit into the Sabre and still offer the performance I wanted.
I wanted to stick with my design’s easy-building, profile construction, and just slap the EDF unit into the middle of the profile fuselage, but a major concern was the profile fuselage sections directly in front of and behind the EDF. I figured that they would or could kill a lot of the unit’s thrust, but I had to try it. I built another Sabre with the fuselage layout modified to accommodate the EDF unit above the wing.
Holding the model and running the fan unit at full-throttle, the thrust seemed impressive, so I hand launched the model and watched, somewhat surprised, as it climbed out steeply just as soon as it came out of my hand launch. The EDF Sabre had good performance. It was aerobatic, and in every way a good sport flyer.
An unexpected bonus of this design is its capacity to take off from the ground. Power up, and the Sabre simply slides across the dry grass field, gets up to flying speed, and jumps into the air. Who needs landing gear?
Aviation history is interesting, and I recently learned that the original version of the Sabre, the FJ-1, had a straight wing, basically “borrowed” from the P-51 Mustang. To improve its performance, the North American engineers used data obtained from the German aircraft industry after World War II on the benefits of swept wing design, adding a swept wing to their F-86 design. The resulting F-86 Sabre was successful, as most MiG-15 pilots who engaged a Sabre over Korea will attest. Nearly 10,000 F-86 aircraft were eventually produced.
Read the entire build article in the Fall 2012 issue of Park Pilot.
The two aileron servos are installed in the upper surface of the wing panels to keep the bottom of the airplane clean for belly landings. The F-86 offers many scale color schemes to choose from when finishing your model.
Here’s Dick’s 70mm EDF unit installed in the profile fuselage. The fan unit is held in the fuselage with hot glue.
Here’s the F-86 EDF, taking advantage of its power to come off the ground from a slide-over-grass run.
Despite its small size, the F-86 must be assembled with all its flying surfaces set at the correct angles.
I changed the fuselage layout from scale, lowering the wing position so that a 70mm EDF would be able to fit over the wing. Because the wing is now at the bottom of the fuselage, I mounted the aileron servos on the top surfaces of the wing to keep the bottom clean and free of all equipment.
I chose the ELE 70mm fan unit. It comes with the brushless motor and an eight-blade fan, and it calls for a 40A ESC. The fan unit is held in place with a few dabs of hot glue. I haven’t checked the current draw, but use a high-C-rated battery pack. This thing blows air like a mini leaf blower.
The F-86 hand launches easily with an underhand, swing-arm toss, but the fan unit delivers enough power to let this model slide over dry grass for easy ROG takeoffs. Once I figured that out, I tapered the fuselage bottom from below the wing upward toward the tail, approximately 3/4 inches higher at the tail end so the jet could rotate slightly for a smoother takeoff — always nicer than sudden leaps.
This model has made me a big fan of EDF units, and I plan to do a lot more with them. This stuff is fun!