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Kappa 25 F5J-400

Product Code: KAPPA25
 (1 review)

Price: $684.02

1 in stock

Available Options

* Layup, Colour (serial#):


The Kappa 25 is a great 2.5m (100") span F5J electric thermal soarer for sports and competition modellers wanting a smaller model. It is light, well designed, and is built to a very high standard. The Kappa 25's advanced structural design ensures it is strong enough for its intended mission, and its finish, completeness and attention to detail is outstanding. The model really is almost ready to fly, with all the wing control horns and pushrods ready fitted, so the only work required to finish the wings is to fit the servos. The fuselage just requires the tailboom, fin and tailplane mount to be glued into place, and the tail control runs installed.

Special features of this model include:
  • A well designed low drag fuselage with a large underwing hatch giving good access to the powertrain and RC, making for easy RC installation and maintenance.
  • A high aspect ratio wing with proprietary airfoils optimised for F5J flying - the wing excels in tight thermal turns, allowing the model to be confidently climbed away from small, weak thermals.
  • Despite its extremely good thermal performance the wings maintain a good L/D up to higher speeds, allowing the Kappa 25 to easily return from far downwind.
  • The wing has slightly swept back wing tips, making it approximate to the Schulman planform. This is meant to improve performance and handling, especially near the stall.
  • Superb quality of construction and attention to detail. The model had been constructed by master builders who must have invested hundreds of hours in each airframe. The level of finish achieved is very rare.
  • The all the control surfaces are sealed and the wing control horns are all hidden inside the control surfaces, further reducing drag.
  • The level of completeness of the airframe is exceptional, allowing the model to be finished in just a few days.
  • The wing breaks down into two pieces and the tailplane is easily removable, allowing the model to be easily transported to contests.

The model is available in three composite layups:

Glass - Mostly glass covered flying surfaces, with carbon local reinforcement and a strong carbon spar. This is the lightest version.

DBox - The flying surfaces have a carbon DBox at the front. The rest is mostly glass with carbon local reinforcement and a strong carbon spar. This version weighs approx 30 g more than the Light version but is stronger. This layup costs approx 9% more.

Spread Carbon - All the flying surfaces are covered in lightweight spread carbon, with extra carbon local reinforcement and a strong carbon spar. This version only weighs approx the same as the Light version but is much stronger and less susceptible to hanger rash and handling damage. This layup costs approx 24% more.

For all wing layups the fuselage is all carbon. For all electric models (irrespective of the fuselage construction) we recommend the 2.4GHz aerials are exited from the fuselage, so they are in the outside airflow. One horizontal and one vertical aerial usually works well. There is too much electrical equipment in an electric glider fuselage for the RC signal to be reliably received inside the pod.

All models are supplied with high quality sewn cloth padded wing bags, to ensure the wing stays in perfect condition. The aileron and flap linkage hardware is included, as is the rudder and elevator horn. But the tail pushrods are not included. We recommend either using pull-spring control runs, as is popular on discus launched gliders. See our DLG hardware for suitable items. Alternatively use lightweight pushrods made from 1mm carbon rods running in our 1.68mm PTFE outer tubes.

Kappa 25 Specifications
Wing span 2.5 m 98 in
Wing area 38.7 dm2 600 sq in
Length inc spinner 122 cm 48.0 in
Flying weight from 760 g 26.8 oz
Wing loading 19.6 g/dm2 6.4 oz/sq ft
Aspect ratio 16.0
Wing airfoil Proprietary
EDA (dihedral) 4.5º
Spinner Diameter 32 mm
Centre of Gravity 68-71 mm from wing leading edge
Controls Rudder, elevator, ailerons, flap, throttle

Kappa 25 Typical Weights
Fuselage 87 g 3.1 oz
Glass layup wings 386 g 13.6 oz
Tail Plane 13 g 0.5 oz
Fin 13 g 0.5 oz
Accessories & glue 18 g 0.6 oz
Total structure 517 g 18.2 oz
Wiring 10 g 0.4 oz
Pushrods 9 g 0.3 oz
Receiver 8 g 0.3 oz
Rudder servo 5 g 0.2 oz
Elevator servo 5 g 0.2 oz
Wing servos (4) 40 g 1.4 oz
Speed control 34 g 1.2 oz
Motor 45 g 1.6 oz
Prop & spinner 20 g 0.7 oz
Battery 67 g 2.4 oz
Flying weight 760 g 26.8 oz

Recommended Servos
Rudder & Elevator Ripmax SD100, Blue Bird BMS-101HV, KST X08, MKS DS65K, MKS DS75K
Ailerons Ripmax SD100, Blue Bird BMS-101HV, KST X08, MKS DS65K, MKS DS75K
Flaps Ripmax SD150, KST X08, MKS DS75K, MKS DS6100, MKS HV6100, Hyperion DS09-AMD, Corona DS843MG, Blue Bird BMS-105HV

Kappa 25 Powertrain Recommendations
Powerline Micro 1015 3S 800mAh LiPo, 15x8 prop
Powerline Micro 1010 3S 600mAh LiPo, 12x6 prop
ADH300L Front Mount 3S 450mAh LiPo, 9x5 folding prop
ADH300L Front Mount 2S 450mAh LiPo, 11x6 folding prop
Mega 16/15/4 direct drive 2S 800mAh LiPo, 10x5 prop
Dualsky XM2826CA-10 45g outrunner 3S 800mAh LiPo, 10x7 prop (19A, 5.0 m/s)

Reviews 1  

 Review by:

Review from Australia

I have only just completed the model and had half a dozen trimming flights. The Kappa arrived at my home in Queensland, 10 days after ordering, which I think is brilliant, well done HyperFlight, some Australian company’s cant process and deliver an order to me in that amount of time.

The model was removed from the box with much anticipation, no damage, plenty of bubble wrapping had been used for shipping. The workmanship and finish of all the model parts is excellent. I have just returned to modelling after 25 years and I have never owned any thing like this before, so I spent a couple of weeks looking and planning before I started the build, thinking "would have liked a basic set of construction details etc with control throws, etc.". Google to the rescue.

She went together easily after deciding the position of the fin and rudder. a bit of a grey area, found photos on RC groups, of fin and rudder mounted on top of the boom and some with the rudder extending to the bottom of the boom. Went with the second option. Cut the boom to give me 1200mm to the LE of the rudder and then extended the rudder down to the bottom of the boom. Possibly wrong choice, she came out tail heavy, even with a rearward CG of 75mm. I have 22grms of weight taped to the back of the esc. All motor / esc wires were shortened as much as I could and the battery is pushed as far forward as it will go. I used 1mm carbon fibre inside PTFE tubing for the rudder and elevator pushrods. R&E servos are fitted at the rear of the hatch area is a fiddly job.

Wing servos were then wrapped in tape and then glued in place with ply servo frames. I went a bit overboard and epoxyed in some extra small blocks around the servos. The wing wiring harness was soldered up to the mini deans plugs with a lot of swearing, not a job I enjoyed. The receiver aerials were exited - 1 thru the top and 1 thru the side of the fuse. With everything mounted including the extra 22 grms and battery she came out at 870 grms - a little over weight. my servos, esc, motor and battery are heavier than the items in the model spec sheet.

The radio - Futaba 10j - was programmed as per full house sailplanes and with the motor on a switch. Spent a week looking and checking and double checking then down to the club field.

Range checked out OK.
Cool, early morning, no breeze
A good firm hand launch, no motor, she just flew straight out and kept going.
no control inputs until a flair to land.
Next, turn on the motor and launch, needed down to maintain a steady climb, climb rate was good, all control throws were to much, first flight was just over 4 min.
The next five flights were used to check and adjust control throws.

I am very happy with the way Kappa flew, and she will only improve as I continue with the tuning process.

Gear used: Dualsky eco 2216 Kv 980
Motor: Hyperion G7- 900 x3s
Esc: Hefei 45a.g
Servos: Ail / Ripmax 150, Flap/ Corona, R&E / Hitec HS45hb.

I am not happy with any of the servos I used / they do not centre very well. Apart from that I am very pleased with the plane.


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