CHK Thermik-Star spezial

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101 Wingspan Thermal Glider for REFLEX XTR² CHK Thermik-Star spezial with and without electric drive Thermik-Star is a very nice thermal glider (softliner) by the small but choice manufacturer CHK in

It was available with electric drive or without, with V-tail or T-tail, with bigger (like here) or smaller wings, and with spoilers or without.

1 101 Wingspan Thermal Glider for REFLEX XTR² CHK Thermik-Star spezial with and without electric drive Thermik-Star is a very nice thermal glider (softliner) by the small but choice manufacturer CHK in Regensburg, Germany. It was virtually the entry level model of this manufacturer, well suited to beginners, but a fully fledged floater. It was available with electric drive or without, with V-tail or T-tail, with bigger (like here) or smaller wings, and with spoilers or without. Unfortunately, the model is no longer produced and the manufacturer closed. For REFLEX, the model is 'equipped' with a 'medium powerful' electric drive, V-tail, and the bigger wings with ailerons, but without spoilers. Additionally, there is the same model with lighter batteries, and without drive as a pure glider. Flight behavior is very pleasant and good-natured, thermal performance is very good. This is all fully revealed in REFLEX. 1

The diagram shows the calculated speed polar for gliding. Both horizontal and vertical speed are shown in m/s. By calculation, Thermik-Star should have a lowest sink rate of 0.

2 The diagram shows the calculated speed polar for gliding. Both horizontal and vertical speed are shown in m/s. By calculation, Thermik-Star should have a lowest sink rate of 0.38 m/s at an airspeed of 8.3 m/s and the shallowest glide of 0.43 m/s at 10.0 m/s. That is a 23.2 glide ratio and a decent value for such a model (and for the 1.7 kg / 3.75 lb weight). The values are not measured, but the model in REFLEX gives the impression of being that good. Thermals with 1 meter per second vertical speed are sufficient to let the model go up and away. It will be difficult to land it gracefully against thermals. Good tricks are slowing down (nose up, the model may drop the nose, but not a wing) and side-slip (rudder is effective enough). Sometimes, substantial rudder is required together with ailerons, even though there is some differential. It's useful to have a mixer automatically combining 70% rudder with full aileron. Circling in thermals is nearly self-stable. In REFLEX, ailerons deflect also as flaps (flaperon), both up and down. In the parameter file, maximum deflection is set to 30 degrees to have spoilers like on the real model. But up deflection has no effect in REFLEX in the first place, so down deflection is needed instead. In that case, the model will be not fully controllable and you will have to use rudder instead of ailerons. Then again, the model s controls may be assigned to transmitter channels so all is working like in reality (see below). 2

3 The REFLEX model s drive is set up like on my real model. It has a brushed motor Plettenberg HP 200/25/5 with 4.4:1 gear, an aero-naut CAMcarbon 14x8" folding propeller, a Schulze smart-45bo ESC and a 7 cell Sanyo RC NiCd battery. This drive was recommended by (and bought from) CHK and is very efficient. So a fully charged battery will give many climbs to thermal altitude. The diagram shows the drive s calculated thrust/speed curve. Thrust T is in Newton and speed v is in m/s. The normal speed range of Thermik-Star should be 6 to 15 m/s, best is then 11 m/s. In REFLEX, the calculated green curve is approximated by the red line. This seems to give a realistic flight behavior, like that of the real model. The electric drive replaces not only a high-start but also spoilers. It's easier to land 'on the spot' and just safer to land with a drive, provided you save some battery capacity for that. In REFLEX, only total motor run-time is counted (power-on time), so the now set 6.5 or 15 minutes, respectively, can be extended in thermal flight. The drive's weight seems to be good for the model since it's 'penetration capability' in strong wind is better with it. Hand launching the model requires at least 6 to 8 meters per second launch speed, but 10 m/s are better. 3

4 That even applies to the pure glider without drive, which is here set to a 500 g lower weight. Given 1.5 to 2 m/s 'Thermal current' in Reflex, it's easy to reach thermals from 10 m 'Launch initial altitude'. By the way, the new glider sound is assigned to this model, but the electric powered variant has still the original drive sound without glider noise (hiss). For more information in German on my real model see my Web page. In English, there were only the web pages of the manufacturer CHK. Some reports on the model could be found in the Web using search engines, but most of them were in German. The REFLEX models There are three basic models: Thermik-Star E (with an electric drive with NiCd batteries), Thermik-Star E new (with LiPo and NiMH batteries), and Thermik-Star G (pure glider without drive). They are flown with standard transmitter settings. The demo flights Thermik-Star E und Thermik-Star G (hit F9 in REFLEX) show the model s impressive thermalling and slope soaring performance. The electric model s motor run-time is set to 6.5 minutes or 15 minutes (new), respectively. REFLEX counts this run-time when the drive is not completely off, no matter how much power is set. Therefore, you may extend the duration of a flight as you like by shutting off the motor completely while flying in thermals. You should save up some of the motor run-time so you can use the drive for the landing procedure. Back to the effect of ailerons deflected up as spoilers (spoilerons): Normally in REFLEX, the ailerons can only act like flaps (flaperons) when deflected down. In this case there s virtually no aileron effect. In REFLEX, this minor problem is solved by assigning transmitter channels to model controls (model specific channel assignment) and generating the control deflections using transmitter mixers, just like with the real model. Thus there are the models Thermik-Star E tx, Thermik-Star E new tx, and Thermik-Star G tx ( tx for transmitter ). All these models are prepared in the same way for use with transmitter mixers. Ailerons and virtual flaps both have 30 maximum deflection, the two V-tail controls 25 in the REFLEX parameters. In REFLEX, under Control... (menu Model or Shift-F7) you ll find the following assignment, suitable for Multiplex transmitters, but to be adapted to other transmitters. The Multiplex transmitters always have the two-servo aileron mixer assigned to channels 1 and 5, and the V-tail mixer to channels 2 and 3. Other transmitters are different or adjustable, respectively. 4

5 Control Channel reversed Aileron left 1 Aileron right 5 X V-tail left 2 V-tail right 3 X Motor 4 Channels 5 and 3 are reversed here because the Multiplex transmitters need a special servo setup. This may be different for other transmitters as well. Anyway, you have to set up your transmitter for 100% (of 30 ) up and 22% down maximum deflection of the ailerons. There should be some differential, so the ailerons go down only 22% and up only 48% as ailerons. When the ailerons are deflected 100% up as spoilerons, one of the ailerons should go down for aileron effect. The two V-tail halves should deflect 100% (of 25 ) for rudder effect, but only 72% for elevator effect. Besides, they should go up 35% when spoilerons are deflected to counteract their pitching-down moment. No such correction is needed for running motor. 70% rudder with 100% aileron deflection (Combi mixer) is recommended. This is all based on recommendations of the model manufacturer CHK. It will give a somewhat sluggish control response of the model that is not unpleasant for thermal flying, though. In any case, with these control settings the REFLEX model behaves very realistically. Enjoy! Burkhard Erdlenbruch mailto:burkhard@erdlenbruch.de More REFLEX models and the latest versions are on my page 5

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