Pilots just starting in RC indoor precision aerobatics should start in this category. First, obtain an appropriate model, either used or new. Typical models made of epp or depron foam are the most popular and readily available, and are designed to exclusively to perform indoor RC aerobatics. Models typically span about a 30inch wingspan and weight slightly above 100 grams, usually less than 200 grams. Just like outdoor models, the lighter the model is, the overall better it will perform aerobatics. With some practice, the models can also be used to compete in some of the lower, easier class of indoor RC precision aerobatic competition.
It is worth noting that flying indoors in itself has a learning curve. Box limits are absolute and gaining a comfort level close to walls and the ceiling can take some time. Hence, initial indoor flying benefits from flying with durable and easily repairable planes.
The first model option, with no assembly required, is the E-flite UMX Yak 54. The Yak is reasonably affordable and can be obtained with a handful of 1S lipos, with about 200 Mah or higher capacity and a multiport lipo charger. Add a DSMX compatible transmitter with a little tuning on rates and expo, and the Yak is capable of very credible precision aerobatics. This plane really is a quick and easy option for getting a start with indoor aerobatics. The lightweight carbon fiber reinforced mylar covered foam framework is surprisingly durable and amenable to repairs with foam safe CA and tape.
The next model option is the RC Factory Clik. This EPP foam kit is available in the USA from Twisted Hobbies, and most definitely requires assembly. Construction is relatively straight forward using foam safe CA (brittle, but quick) or a flexible glue, like Beacon Foam-Tac. Foam-Tac can be used as a traditional glue, or as a contact cement and adds a minimal amount of time to the build. The EPP structure of the Clik is quite durable and flexes in crashes, and potential crash damage is further minimized when assembled with Foam-Tac.
The number of optional motors, ESCs, lipos, and servos to equip the plane are plentiful. Equipment options make a big difference in the flying weight. Numerous options/ packages to complete the plane can be found on the Twisted Hobbies website.
A typical Clik intended for flying outdoors (calm mornings and evenings) can be expected to weigh in at 140 +/- grams. For outdoor flying, a larger motor (15- 20 grams) and lipo (250-400 mah, 20-30 grams) is beneficial to maintain an overall higher flight speed and reduce crab angles. A Castle Creations Talon 15 and APC 9x3.7 are good starting points. At the higher flight speeds, larger servos are needed to maintain good control authority. For an outdoor Clik, 7-9 gram aileron servos suffice (20+ oz/in torque), with rudder / elevator servos in the 5-7 gram range (8- 12 oz/in torque). The receiver need not be full range, and should be the lightest possible with connections matching the servos. A typical Clik intended for indoor flying should weigh less than 120 grams; the lighter the better. Small changes in weight are much more noticeable in indoor spaces; increasingly so as the space gets smaller (especially ceiling height). With careful building and equipment selection, 120 grams can be achieved.
An attempt was successfully made to pursue lighter components and some moderate lightening of the airframe and components to produce a Clik V4 with a flying weight of about 100 grams. Associated equipment used to achieve that condition included Dualsky XM2212MA-25 2160 KV, motor at 10.5 grams, a Castle Creations Talon 15 ESC, a PT 9x3i carbon fiber propeller, a Hyperion 2s180 lipo battery, one JR DS188 for aileron servo at 6 grams, 12 oz/ in torque, 0.08 seconds, and Power HD DSP33 servos at 5 oz/in torque, 0.07 seconds for rudder and elevator controls.
Models flying in this category should be capable of flying simple maneuvers such as rolls, loops, and stall turns. Its up to the pilot to master precision slow or point rolls, round loops, etc, within the limited indoor flying space available.