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Kappa 20

Product Code: KAPPA20
 (2 reviews)

Price: $514.53

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The Kappa 20 is a great 203 cm (80") span F5J electric thermal soarer for sports and competition modellers wanting a smaller model. It is very light, well designed, and built to a very high standard. The Kappa 20'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 20 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 two 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 11% 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.

At 203 cm span the Kappa 20 is slightly over the 2 m wing span limit for some competition classes. If competition flying do check with the CD to ensure it is acceptable. If necessary 3 cm can be trimmed from the wing tips without compromising the excellent flying qualities.

For more info see this RCGroups thread and this thread with some useful photos.

Kappa 20 Specifications
Wing span 2.03 m 80 in
Wing area 30.0 dm2 465 sq in
Length inc spinner 112 cm 44.1 in
Flying weight from 623 g 22.0 oz
Wing loading 20.8 g/dm2 6.8 oz/sq ft
Aspect ratio 13.8
Wing airfoil Proprietary
EDA (dihedral) 4.5º
Spinner Diameter 32 mm
Centre of Gravity 78-81 mm from wing leading edge
Controls Rudder, elevator, ailerons, flap, throttle

Kappa 20 Typical Weights
Fuselage 82 g 2.9 oz
Glass layup wings 260 g 9.2 oz
Tail Plane 13 g 0.5 oz
Fin 13 g 0.5 oz
Accessories & glue 18 g 0.6 oz
Total structure 386 g 13.6 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) 36 g 1.3 oz
Speed control 34 g 1.2 oz
Motor 45 g 1.6 oz
Prop & spinner 18 g 0.6 oz
Battery 67 g 2.4 oz
Flying weight 623 g 22.0 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, Corona DS843MG, Hyperion DS09-AMD, Blue Bird BMS-105HV

Kappa 20 Powertrain Recommendations
Powerline Micro 1010 3S 500mAh LiPo, 12x8 prop
Mega 16/15/4 direct drive 2S 500mAh LiPo, 7x4 prop
ADH300L Front Mount 3S 450mAh LiPo, 9x5 folding prop
ADH300L Front Mount 2S 450mAh LiPo, 11x6 folding prop
Dualsky XM2826CA-10 45g outrunner 3S 500mAh LiPo, 10x7 prop (19A, 5.0 m/s)

Reviews 2  

 Review by:

It was never my intention to have an E-glider, as my staple diet for the last 12 years or so has been DLGs and sailplanes, but the grass in the two local fields I use has lately been so long as to prevent proper launches of anything. A hay crop has been taken now, but I've wasted a good few flying weeks.
And so I decided to try an E-glider for when ground conditions are not ideal - and big thanks, as ever, to Neil for his patience and advice. I wanted something that was small enough to carry to the local field without dismantling, but large enough to be interesting. I was tempted by the Blaster 2e, which would have been a nostalgic trip, as my first serious DLG was a Blaster 2. But I liked the look of the Kappa 20, and I am pleased I made that choice. It arrived very quickly, all parts generously bubble-wrapped and suspended inside a sturdy cardboard box. Neil excels at packaging, as well as giving a first-class service in every way.
This is a really beautiful model with impeccable workmanship, and I love the swoopy lines of the wing. I also admire the way the designer has done everything to eliminate drag: aileron and flap actuation is internal with no external horns, and the elevator and rudder gaps have been sealed.
The other reviewer on this page mentions that the tailplane boltholes are slightly off-centre. It certainly looks that way, or is it merely that the longitudinal carbon reinforcement is off-centre? I did a lot of measuring and at first I felt they were spot-on, but then I wasn't quite so sure, so have opened them up a bit so that the tailplane can be aligned absolutely perpendicularly. As Ian says, it won't affect the performance, but....
The other point he makes is that the aileron pushrods need a bend in them. They are situated in the servo wells and rest firmly against the inside of the wing's upper surface. If they are pulled up at an angle to slip into the servo arm, the ailerons will not operate properly and are extremely stiff.
It would be possible, I suppose, to mount the servo on a block and have the arm pointing downwards, but I didn't feel happy about that idea, so I bent the front part of the rod upwards, leaving the rear of the rod flush with the wing's inner skin. This works fine, but the rods are short and very stiff and I had to use two pairs of long-nosed pliers to form the bend. Great care is needed, as a slip under pressure could cause damage. to the wing. The flaps are not an issue, as the pushrods are more free-floating.
For power I will be using a Powerline Micro 1010 Turbo, a simple Hobbyking 30A ESC, and a 3S 500mah Turnigy Graphene lipo.
Servos caused a little head-scratching. The manufacturer recommends D47 and D60 (Ripmax SD100 and SD150) - certainly something thin is needed if one is to avoid bulging servo covers and adhere to the designer's intent of minimising drag. These fit all right, but I really wanted MKS DS65K's for the ailerons, although their arms have a substantial boss and I did not think I could drill a pushrod hole close enough to the servo without the arm protruding below the bottom skin of the wing. But I could - just - and very little throw is needed to get enough movement on the ailerons.
For flaps I will use KST XO8N's, and DS65K's for elevator and rudder. Pull-spring actuation a la DLG's is possible here, or 1mm carbon rod in 1.68mm teflon tubing.
The Kappa fuselage is very slim, but there is plenty of room for all the gear. The belly hatch is a neat access point.
I'm excited about my first venture into E-gliding, and very happy with my choice of glider: the Kappa is a beautifully executed design - light, strong and sleek, and looks as though it means business. Hope to be flying in a few weeks.

 Review by:

Received my Kappa 20 very promptly, and well packaged as one would expect from Hyperflight.
Assembly was pretty straightforward if a little fiddly. The quality, and fit of the various parts was excellent, with one minor exception; that being that the 2 bolt holes to fix the stab to its pylon were slightly offset each side of the center-line, so the stab is a few degrees off perpendicular to the boom. Unfortunately, I didn't notice this until I was admiring the completed model, and i'm sure it has no effect on the model's flight.
I also feel that a slight crank in the aileron pushrods would have been helpful to the assembly.
In flight it is fairly similar to my old Sprite it has replaced, fairly fast for a thermal glider, and requiring full concentration as its slim profile leaves it prone to disappear at height! It sniffs out lift very well, and circles tightly. An excellent model.

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