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|Lovely Day at rest displaying its airbrake flaps (click small images to enlarge and get more information).||Designer Mike White with his unusual model (click small images to enlarge and get more information).|
Control of the model is by rudder and elevon, as well as trailing edge air brake flaps. Five servos are used in total.
edge airbrake flaps
The inner part of the trailing edge incorporates an airbrake flap which consists of a short moveable surface which can be extended upwards to about 85 degrees, and down to around 5 degrees.
The power system comprises a Thumper 3536/910 (910Kv) outrunner turning a Cam Aeronaut 12 x 6.5 folding propeller. This combination draws 27 amps from a 2S 3,000mAh lipo, equating to about 200 watts of power. The wing span is 95 inches and the model has a wing area of 10 sq .ft. area. The flying weight is 80 ounces (5 pounds) which means the wing loading is 8 oz / sq ft and the power loading is 40 watts per pound.
This power system gives four climbs to 800 feet which is set on the Winged Shadow altitude limiter (see below). With the 2,500mAh receiver battery total flight time is long enough to give 4 flights in excess of 20 minutes each in still air conditions.
|The insides of the model. Space is at a premium.||The insides of the model. There's not a lot of room in here.|
The very low wing loading, just 8 oz/sq ft, and the abundance of power means that launching is easy, there being no 'sag' after launch. All that's required to get the machine safely away is to give a very positive forward push.
Airbrake flap operation
At small angles of deflection the airbrake flaps have the effect of applying some up elevon. In this condition there is little drag increase. When deflected upwards, the airbrake flaps cause a nose up pitch. To counteract this I set up a transmitter mix, so that as the airbrake flaps are extended, down elevon is applied. Establishing the correct mix requires some experimentation, as no two models are exactly the same. Also the balance point does make a difference to the nose down trim required.
At high angles of deflection the airbrake flaps produce a significant increase in drag. In the landing approach, the airbrake is progressively but not too quickly applied. With the down elevon transmitter mix I have set (elevons about a quarter inch down) she settles into a nose down pitch attitude with very little speed increase.
I am experimenting by setting the airbrake flaps about 1/8 inch down for the launch to locally increase the camber of the wing. In this condition I hope that the climb rate will be higher with a little less power set. This setting stays for the cruise while looking for thermals.
|Lovely Day passes close by designer Mike White for the camera.||The airbrake flaps are located at the trailing edge of the wing next to the elevons.|
The altitude limiter is an electronic gizmo which senses a pre-set altitude and shuts the motor down when this is reached. It may be used again when the altitude is reduced. I like gadgets!!! Used with the electronic recording altimeter fitted it makes for interesting flight testing and general flying.
I also fitted a Winged Shadow thermal detector. When lift is detected the rudder moves from side to side. This is switched out at the transmitter for the climb, and switched on for the cruise. I did have a few sweaty moments during the first use as I had forgotten to switch the detector out. As you can imagine the climb and ensuing, almost uncontrollable antics, were a scream but nevertheless very worrying, until I remembered to switch the thing off.
|The airbrake flaps in the raised position.||The model flies well, but rudder response is poor, perhaps due to the short moment arm.|
The project was successful and I am happy with the way the model flies. The air brakes may be even more effective if they were larger but as they are, they seem to work fine when the elevon pitch mode is mixed to compensate the nose up trim change. I would have liked to have the servo wire leads easier to connect when attaching the wings. At the moment they are a bit messy and the room inside the fuse is at a premium. Thanks to my flying buddy Peter Lloyd-Davis for being the launch master and for taking the flying shots.
|Lovely Day technical data|
|Span||2,413 mm||95 inches|
|Root/tip chord||570/292 mm||22.5/11.5 inches|
||0.00 sq m||10.0 sq ft (1,440 sq in)|
|Flying Weight||2,268g||5lb (80oz)|
|Wing Loading||00g/dm||8 oz/sq ft|
|Battery||2S 3,000 mAh LiPo|
|Motors||Thumper 3536-910 (Kv 910)|
|Prop||CAM 12x6.5 folder approx 00,000 rpm|
|Max Power||27A / 200 Watts|
|Power Loading||000 W/kg||Approx 40 W/lb|
|Control functions||Elevons, airbrake-flaps, rudder & throttle. 2,500mAh 4-cell NiMH receiver battery|
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