Kestrel F5K 1.5m

The Kestrel F5K is a truly beautiful model that brings together all the skill and knowledge of the OA Composite team. The Kestrel’s design is informed by the experience acquired designing, manufacturing and competing at the highest level with discus launched gliders. This has allowed them to create a four servo polyhedral wing electric DLG type glider that blows away the competition.

Anton Ovcharenko of OA Composites, and Christophe Bourdon designed the wing with an original and innovative geometry, with polyhedral, and with forward sweep (on the 1/4 chord line). The polyhedral gives the model brilliant handling and great stability, and makes it possible to climb in weak lift even at the limit of eyesight. The airfoil is optimised to use large flaps and ailerons for maximum control on landing, for excellent manoeuvrability in slow flight and for accurate circling in small thermals and disorganised patches of lift. The progressively reducing control surface chords optimize the distribution of lift (and drag) at high angles of attack and allow large control inputs even at minimum speed, with the airflow staying attached and roll axis control staying progressive and sweet.

The family of airfoils has been optimised for superior versatility in the critical flight phases, which are high speed cruise, where the glider must be able to accelerate fast to get to a distant thermal quickly, and also flight at high angle of attack when carrying ballast in turbulent, windy conditions. The result of this work is a glider that can accelerate and maintain speed with less altitude loss and is very easy to thermal even in difficult conditions.

The Kestrel F5K incorporates a two-piece wing and easily dismountable tailplane and fin, allowing for easy transportation. The four aileron and flap servos are installed directly in the wing allowing direct linkages and a narrower fuselage and thus less wetted area and drag. The tail servos are mounted under a hatch below the wing, so all of the servos are easily accessible. The wing roots incorporate plugs and sockets for auto-connecting servo wiring and the fuselage end of this is ready wired to servo plugs to fit to the receiver. The nose of the fuselage has been kept short to create as little drag as possible, even at high slip angles, and to keep the inertia as low as possible which improves characteristics in all flight phases. Despite the short nose there is a lot of space in the fuselage for the powertrain and for ballast, though this is not supplied. The generous tailboom length and substantial tail areas ensure good control authority and stability, which will not fail to please the most demanding pilot.

The carbon parts fit and finish is excellent. The models have attractive colour schemes and a high gloss finish. The kit is very complete and the accessory bag contains all the small parts needed to complete the model. The model is supplied with a recessed 27mm carbon firewall with four holes on a 12m circle suitable for 1806 motors and 25mm diameter spinners. An alternative to fitting this is to use one of our Electric DLG CNC Motor Mount, however this will require a few mm to be removed to get it to fit.

The Common Kestrel is a formidable hunter, capable of fast flight as well as exploiting surprisingly small thermal currents. And in flapping (powered) flight the bird can hover easily at a very high angle of attack in order to locate and liquidate its prey. Like the bird, the OA Composites Kestrel F5K is modest in size, but beautifully incorporates all the best aspects and flight characteristics of larger F5J models.

(C) 2023 Christophe Bourdon and Neil Stainton.

Kestrel F5K Specifications
Wing span	1.5 m	59 in
Wing area	20.2 dm2	313 sq in
Length inc spinner	95 cm	37.4 in
Flying weight from	270 g	9.5 oz
Wing loading	13.4 g/dm	4.4 oz/sq ft
Aspect ratio	11.0
Wing airfoil	C Bourdon proprietary
EDA (dihedral)	6.2º
Spinner Diameter	25 mm
Centre of Gravity	60 mm from wing leading edge
Controls	Rudder, elevator, ailerons, flaps, throttle

Recommended RC
Tail servos	KST X06, KST X08, KST A08, MKS HV70, MKS DS65K, MKS DS75K, CHA LV06, CHA DS06
Flap servos (8mm max thickness)	KST X08N, KST A08N, MKS DS65K, MKS DS75K-N, MKS HS75, CHA LV06
Aileron servos (7.5mm max thickness)	KST X06N, KST X06H, KST X06, MKS HV70, MKS DS65K, CHA LV06, CHA DS06
Receiver	7 channel rx to match your transmitter,

Electric Powertrain Recommendations
HyperFlight 1806	2S 450mAh LiPo, 6x3, 6x4 folding prop
ArmSoar 1507	2S 450mAh LiPo, supplied 6x3 folding prop
ArmSoar 1806	2S 450mAh LiPo, supplied 6x4 folding prop
XPower F2307/14	2S 450mAh LiPo, 6x4 folding prop

Electronc Speed Controls (ESC) Recommendations
HyperFlight 28A BLHELI-32	28A, 2A 5V BEC, JST plug ready fitted
HyperFlight 30A BLHELI-32	30A, 3A 5V BEC, XT30 plug ready fitted
HyperFlight 40A BLHELI-32	40A, 3A 6V BEC, XT60 plug ready fitted
HyperFlight 40A BLHELI-32	40A HV, 3A 7.5V BEC, XT60 plug ready fitted

Kestrel Control Throws & Mixes (for CG at 60mm)
Rudder	15 mm each way
Elevator	7mm up / 7 mm down
Ailerons	8mm up / 12mm down
Flaps	7mm up / 10mm down
Recommended snap-flap (elevator->camber) mix
Full up elevator	3 mm down flaps, 1mm down aileron
Full down elevator	1.5 mm up flaps, ailerons in line with flaps
Recommended Flight Mode Aileron Settings
Speed	flaps trailing edge in line with top of top of fuselage, ailerons in line with flaps
Cruise	1.5mm down flaps, ailerons in line with flaps
Thermal	6 mm down flaps, aileron in line with flaps
Landing mode	as much down flap aileron as possible, ailerons down 3mm

Kestrel F5K Typical Weights
Fuselage	40 g	1.4 oz
Wings (light)	102.0 g	3.6 oz
Tailplane	6.0 g	0.2 oz
Fin	5.3 g	0.2 oz
Wing joiner	4.0 g	0.1 oz
Accessories & glue	9.0 g	0.3 oz
Total structure	166.3 g	5.9 oz
Receiver	5.0 g	0.2 oz
Rudder servo	6.4 g	0.2 oz
Elevator servo	6.4 g	0.2 oz
Flap servos (2)	17.2 g	0.6 oz
Aileron servos (2)	12.6 g	0.4 oz
ESC	6.0 g	0.2 oz
Motor	20.0 g	0.7 oz
Prop & spinner	7.0 g	0.2 oz
Battery	23.0 g	0.8 oz
Flying weight	269.9 g	9.5 oz

Kestrel Wing Approx Weights
Light	95g - 105g
Standard	105g - 115g
Strong	115g - 125g