Electric Flight - September 2013

EDF

;ere are two types of jets — the first were prop jets, which had a motor and propeller. Before the power and performance we now enjoy with electric motors and batteries, we needed the prop jet. ;is is no longer necessary and therefore, this article will concentrate on EDF jets.

EDF jets have a few di;erent approaches to construction and design. ;ey include fully enclosed and exposed electric-ducted fan units, their type of construction, impeller diameter, and the method of inlet air ducting. At the heart of all jets is the ducted fan unit, which is made up of an outer shroud (also known as a duct), an inlet right (lip) at the front of the duct to help smoothly guide the airflow into the fan unit, and a multi-blade impeller that is precisely fitted in the duct, which is driven by an electric motor. ;e impellers attach to the hub which itself is attached to the motor’s prop shaft. Many jets are equipped with an internal air ducting that channels the air into the impellers and exhaust tubes that direct the thrust out the rear of the jet. Depending on the design of the jet, the model may have what is called a cheater hole, or holes that allow more air to be drawn into the ducted fan, which give it a bit more power.

EDF jets can come in any size and construction. ;is rather large airliner is constructed out of foam.

JET CONSTRUCTION

Foam: ;ese EDF planes will have a lower price,
o;er quick assembly time, are generally smaller
in size, and are durable and easy to repair.
;ey can be powered by less expensive, less
powerful systems, and controlled by budget
servos and radio gear. ;ey still o;er the pilot
the speed thrill and are some rather solid-flying
jets. One thing to keep in mind is that the foam
jet is often molded around the ducted-fan unit
and will be di;cult, at best, to remove. Make
sure that these planes have plenty of airflow
through the body to keep everything cool, and
this includes the ducted-fan unit, battery, and
speed control.

Fiberglass/balsa/plywood: ;ese planes will range from mid- to larger-size aircraft and their price can range from inexpensive to very expensive. In most cases, the body is fiberglass and the wings and tail feathers are built-up balsa. Most of the time, any access hatches and ducting work will be molded into the fiberglass. Damage to the wings or tail feathers will be easily repairable by the average modeler. However, damage to the fuselage will most likely be repairable by buying a new fiberglass fuselage.

Composite: When you are looking for the best, this is the category you need to check out. ;is group of planes will require a good outlay of cash or open credit card, but do have a lot of pre-molded design work. ;e sophistication and complexity of these jets will vary greatly and the price tag will also reflect that. Again, it is what is included in the box and the quality of the power system and components used that determines the final outlay of dollars. Size is a factor as well as features such as flaps, retractable landing gear or brakes, these things cost more but you’ll enjoy better performance. ;e tradeo; here is if you are looking for the fastest speed and performance that is on par with a turbine jet, this is the category of aircraft for you!

Landing is where you will need to keep the speed up because of the needed air flow over the control surfaces.

GROUND CONTROL

One of the most important things to consider is the quality of your radio gear. On lighter and simpler EDF jets, you will not need expensive or powerful servos. However, as the weight and speed of your jet increases, there is a flight load increase, which will demand more from your servos. ;is translates to better, stronger, and more costly equipment that you will need. Not only do you need more powerful servos, you will need a better, higher-end transmitter and receiver.