Build It: Eindecker
Written by Dick Sarpolus
A simple, fun profile model
As seen in the Winter 2017 issue of Park Pilot.
Download free plans
Type: Sport model
Wingspan: 37 inches
Wing area: 250 square inches
Length: 28 inches
Weight: 12 ounces
Power system: BP Hobbies BP 12 outrunner; 8 x 4 GWS propeller; BP 15-amp ESC; 3S 1,000 mAh LiPo battery
Dick Sarpolus with the Eindecker.
My longtime friend, Bob Peru, has been active in RC aviation since the days of glass tube radios. He’s always been a scratch builder with traditional materials and techniques. In other words, he makes a lot of balsa sawdust and wood chips.
He’s recently been competitively flying Old-Timer Free Flight RC with ignition engines. That’s why I was so surprised when he told me that his latest project was built from sheet foam and was electric powered—quite a change of pace. Because I’ve been flying a bunch of electric foamie stuff lately, I jumped at the chance to do some flying with his Eindecker.
This little park flyer is fun! Unlike the World War I original Eindecker, this one has ailerons, ample aerobatic capability, and a good power-to-weight ratio for some active flying. With a 37-inch wingspan, it’s not for indoor gym flying but is a good size for a baseball field.
The lightweight model’s good performance comes from the use of a brushless motor and LiPo batteries. Low-priced components are used to keep the cost of this project to a minimum.
The aircraft has roughly 250 square inches of wing area and weighs less than 12 ounces. Depending on the battery used, the wing loading is approximately 7 ounces per square foot, which makes for easy flying. This Eindecker isn’t for aerobatic 3-D fliers, but it’s also not for slow, stable, cruise-around pilots. This aircraft is more for aerobatic, fun park flying.
The brushless motor used is a BP Hobbies (bphobbies.com) BP 12 outrunner with an 8 x 4 GWS (gwsprops.com) propeller. The ESC is a BP 15 amp. There are plenty of small, low-cost, lightweight servos on the market these days. The ones used in this project were Blue Bird (blue-bird-model.com) 306s.
The Eindecker uses an inexpensive power system and radio gear, but provides a lot of enjoyment in flight.
There are several small, lightweight receivers from which to choose. Bob used a Blue Bird receiver with his Futaba transmitter, and a 3S 1,000 mAh LiPo battery pack for power.
Building instructions are brief because this is an easy project. Any of the popular sheet foam construction materials can be used, such as BP Hobbies foam, Midwest Cellfoam 88, Depron foam, or blue fanfold insulation foam. The parts are cut to shape with a sharp modeling knife and/or a razor blade.
The fuselage is made up of two foam layers for more rigidity, and Bob used a spray-on contact cement to laminate them. The wing is perfectly flat—no undercamber and no dihedral—with a 5mm carbon-fiber tube epoxied in place as a spar. Be sure to sand the carbon-fiber tube well so the epoxy holds.
All of the needed foam parts are cut to shape with a sharp modeling knife and are ready to start building.
The leading edges of the ailerons, rudder, and elevator are beveled for hinging, and clear packaging tape is used on both sides as hinges—a popular and proven method. A small plywood firewall is epoxied in place for the motor mounting.
Holes are cut in the foam for the servos, and they can be retained with a few drops of hot glue. Commercial small, lightweight nylon control horns can be used, or you could make your own from thin plywood. Control linkages are thin wire pushrods that attach to the elevator and rudder using a few short pieces of plastic tubing as guides. The ESC and receiver are mounted with Velcro tape, and the LiPo battery pack is also held in place with Velcro.
The wire landing gear is held in place by wrapping it with some thread, applying glue to a small block of wood, and then gluing the block into the foam fuselage with epoxy or hot glue.
Any lightweight wheels can be used, but they should be fairly large if you want to fly from a grass field. This Eindecker gets off of the ground quickly and easily. If the grass is too high, hand launching is easy.
The final finishing could be done a number of ways. Most construction foam for projects such as this is white, and some World War I-style German insignia crosses could be cut from vinyl or low-temperature iron-on material and applied. Bob chose to finish his Eindecker with sprayed-on red enamel. Be sure that the paint you use is compatible with the foam. Water-based acrylic craft paint could also be used.
Dick chose to paint the model using red enamel, which makes it easy to see in the air.
I’ve flown this little Eindecker with 7 x 6, 8 x 6, and 8 x 4 propellers. Performance is good with all of them, but the 8 x 4 might be best. It pulls well and high speed isn’t needed. The motor on the 3S LiPo battery pack draws roughly 9.6 amps and provides approximately 90 watts—plenty for lively performances.
For small, easy-build projects such as this, sheet foam has been adopted by modelers as an alternative to traditional balsa. Hey, whatever material is used, I know flying these airplanes is fun and that’s what it’s all about.
Try a little WW I Eindecker for some up-to-date flying fun!