25-Jun-24 - 06:58 PM

Thermal Circle Text - Thermal Circle 35

Written by Hayden Daley - 08 September, 2021.

Welcome to this edition of the Thermal Circle in this edition the new Spektrum IX 20 SE as well as new F5J sailplanes from Airstrike and a new scale model from Model Flight. The new flagship radio from Spektrum looks good offering many features as listed below. Many thanks to the Model Flight company for providing the Spektrum text. Please enjoy Thermal Circle 35.

Daves Toys is now the largest stocker of F3J,F3B and F5J models. If you wish to buy the latest sailplanes at a good price this company comes highly recommended the service provided is very good and all shipments are insured against damage and other problems. To contact Dave Toys also known as Airstrike on 0415412096 in Australia.

Available from:
Available from:

Spektrum IX 20 SE

The most powerful, intelligent, and feature-packed Spektrum™ transmitter to date, the 20-channel iX20 has given accomplished pilots the tools they need to fly today’s most advanced, high-performance aircraft. This Special Edition version includes all of the original’s programming and connectivity innovations and adds exclusive upgrades, making the iX20 SE a uniquely pro-class flying experience.

Like the iX20, the iX20 SE features Hall effect sensor gimbals that offer advanced precision, low maintenance, and exceptionally smooth operation. For this Special Edition transmitter, the gimbals are constructed of premium machined aluminium that maximizes ergonomic comfort. A high-quality, lanyard style neck strap adds hands-free convenience. A Special Edition aluminium dual transmitter case is included for transporting the iX20 SE safely and in style — perfect whether you’re going to the local field or to compete with the world’s top pilots.

Crafted by Mirco Pecorari and AircraftStudioDesign, the iX20 SE transmitter demonstrates a singular understanding of the features and ergonomics desired by high-level RC pilots. Most apparent is the giant, 5-inch, 720p colour touch-display with leading-edge Android technology. The Spektrum AirWare™ App has a refined, user-friendly interface. Speech-to-text functionality makes it easier than ever to set up custom telemetry warnings, reports and more. Just talk to the iX20 SE, and it will listen.

The iX20 SE also offers the best of Spektrum Smart Technology with Bluetooth, Wi-Fi and voice recognition connectivity along with third-party app availability, capacitive-touch switch sensing and third-party module support via the integrated serial communication port. It’s compatible with Smart telemetry, supporting Smart batteries and Smart ESCs with multiple screens and warnings.

For advanced pilots who fly high-performance aircraft — and any hobbyist who appreciates next-generation innovation — this Special Edition version of the iX20 opens the door to unlimited possibilities.


This Special Edition version of the most powerful, intelligent, and feature-packed Spektrum transmitter to date includes all of the original iX20 programming and connectivity innovations plus exclusive upgrades, for a uniquely pro-class flying experience.


Designed and ergonomically engineered by Mirco Pecorari from AircraftStudioDesign, the iX20 fits a wide range of pilot needs. Its quad-bearing, Hall-effect sensor gimbals offer long-lasting precision with an ultra-smooth feel that’s conveniently adjustable from the front of the transmitter. For this Special Edition transmitter, the gimbals are constructed of premium machined aluminium.

More iX20 Ergonomic Features:

  • Adjustable stick length and tension

  • Easy-grip slide levers with firm-centre detent plus spring tension adjustment accessible from the front of the transmitter

  • Contoured, non-slip rubber grips

  • User-adjustable mode configurations (1, 2, 3 or 4)

  • User-adjustable switch assignments with touch sensing

  • Pushbutton power switch with sleep mode

An aluminium dual transmitter case is included with the iX20 Special Edition for transporting it safely and in style — perfect whether you’re going to the local field for the day or to compete in international contests with the world’s top pilots!

The giant 5-inch, full-colour, easy-to-read touchscreen interface cold-boots (from OFF) in less than 30 seconds and wakes from sleep in one second or less. Its processing speed is approximately 250% faster than that of the iX12. The state-of-the-art touchscreen technology provides information in crisp, clear detail and allows you to make precise changes quickly and easily. You literally “tap” into the iX20’s programming, and model setting changes take effect instantly. Because this is a fully functional Android interface, it will work with an evolving list of apps from the Google Play store.

Huge and easy to read, the 5-inch, Android-powered touchscreen offers a high-resolution 720p HD colour interface with the power to graph expo curves and the like with greater accuracy and view new telemetry gauges in a way that won’t leave you second-guessing.

Long-time Spektrum™ users will feel right at home the first time they pick up the iX20. That’s because its Spektrum AirWare™ Touch app program is built on the same Spektrum AirWare firmware used today. The giant, colour touchscreen interface simply makes menu navigation and setting changes even easier than they were before.


Maybe you’re the proud owner of the most feature-packed model on the planet, maybe not. Use just four channels or all 20. The iX20 intuitive programming uses simple language and logic to help you easily set up and operate any aircraft type, and to custom-tune and add features whenever you like. With its X-Plus™ channel expansion capability, the iX20 also allows you to add up to eight additional channels with an X-Plus Channel Expansion Module (SPMXP8000 – sold separately). Just plug the module into a compatible receiver, bind it to the iX20, and then assign the extra channels to any functions you want.

The iX20 allows you to customize menus based on particular receiver features, adding or removing items that are or are not relevant. Just go into the receiver list drop-down menu and use the on/off buttons to turn items on or off (and to select channel count if the receiver you want is not listed).

The iX20 “My List” provides you with your own custom menu list, accessible on the bottom left of the home dashboard. There you can select the menu items you want and reorganize the list however you wish. Enjoy quick access to the features you use the most!

When connected to Wi-Fi, the iX20 transmitter gets even smarter. Spektrum™ AirWare™ Touch app update alerts are automatic, plus you can download model setups and add third-party apps. The iX20 can connect with just about any Bluetooth device. This means you can use wireless earbuds or even your phone’s earpiece for voice alerts. Music, voice alerts and more are heard privately with outstanding clarity. A micro USB port allows you to charge the internal Li-Ion battery with an ordinary USB-to-Micro USB cable. It can also be used to connect flight controllers, recognize accessory devices and provide a convenient link to your PC or laptop.

The iX20 is the ultimate tool for making sure your prized aircraft and equipment stay in perfect condition. It offers built-in telemetry compatibility that can give you real-time information on critical data like battery voltage, motor temperature and more. The transmitter is compatible with installations using telemetry-enabled receivers and sensors, and it supports those using the innovative, all-in-one telemetry of Spektrum™ Smart Batteries, ESCs and receivers with multiple screens and warnings.

The iX20 takes raw, real-time telemetry data and makes it far easier to view graphically with gauges that put vital information into a context that’s clear and precise. Using the voice alert system, you can program the iX20 to tell you when specific telemetry values reach or exceed the limits you define. You can also have it call out a sequence of telemetry values on demand with the flip of a switch.
Customizable telemetry dashboard pages and custom gauge panels allow you to set what data you want to see and organize it as you choose, with adjustable cell sizing and auto text-size adjustment.

Just talk to the iX20 and it will listen. Its speech-to-text functionality, made possible by Android, allows you to access and set up custom telemetry warnings, reports and more through its voice recognition software.

Keep tabs on important information without ever taking your eyes off what you are flying. The iX20 programmable voice alert system can call out what flight mode you have chosen or report telemetry info automatically or on-demand. If an alarm goes off, you won't have to look at the display to see what's happening. The iX20 can tell you. Create any voice alert by just typing in the words. In addition to a built-in speaker, the iX20 has a headphone jack that allows you to monitor voice alerts using earbuds so you don't bother other pilots. You can also use Bluetooth to connect with wireless earbuds or your phone’s earpiece.

The iX20 has the most program mixes ever offered in a Spektrum radio. In each mix, a curve is available for each position. For example, if you assign a mix to flight modes, you may have up to 10 flight modes; you’ll also have up to ten different curves for total flexibility. Having a
curve for every position provides much more flexibility and power for complex mixing, and can reduce the number of program mixes it takes to achieve the desired setup.

Forward Programming is a Spektrum technology that enables you to configure smart receivers and related products wirelessly and directly from the transmitter. It’s simple. Forward Programming uses the existing bi-directional communication link between a transmitter and receiver to do the same sophisticated programming that once required a cable, Bluetooth dongle, PC or a mobile phone. Plus, Forward Programming uses intuitive Spektrum AirWare™ firmware language so it’s simple to use.

Easily fine-tune programmed features while flying without awkwardly having to access a specific menu or land just to tweak an adjustment. On-The-Fly (OTF) lets you adjust mixes and other programmed values conveniently “on the fly” by simply using one of the four auxiliary trim controls (not the primary trim controls) you select.

Turn timers on or off, or activate programmed voice alerts with just your touch. An industry first, the iX20 uses capacitive-touch technology so that any of the ten toggle switches, the I-switch button, or gimbal sticks react to the soft touch of a finger and without interrupting the programmed mechanical movements also assigned.

The iX20’s enormous internal memory — large enough to hold 250 models — means you’ll rarely if ever, need to juggle models between the transmitter memory and SD card or Bluetooth memory devices. Nevertheless, transferring model programs is simple and seamless with the iX20 and other Spektrum brand radios. You can easily share models between “G2” systems and iX-series radios via SD card or Bluetooth. Note: The iX20 can import SPM and iSPM file types, but can export only iSPM type files.

Having multiple antennas built-in assures RF performance regardless of how the iX20 transmitter is oriented while you fly. In addition to the visible antenna, another is designed into the transmitter front case. It’s a proven effective system that enhances signal reception
while reducing polarization.

A camera is built into the iX20 transmitter and can be used to take still photos and videos. The lens is located in the rear centre of the transmitter. It’s easy to capture images of your own aircraft and add them to the Model Details menu.

Go further with the iX20 when you explore what the integrated auxiliary serial port has to offer. It’s a next-level link that lets you accessorize the iX20 transmitter with an alternate RF system, such as the TBS Crossfire CRSF protocol technology, and still enjoy extremely low latency performance.

The exclusive functionality of the Spektrum™ wireless trainer link gives iX20 users the ability to link up wirelessly with other Spektrum transmitters. It’s hassle-free. Once bound to another transmitter or component, ModelMatch™ technology will allow the iX20 to re-link
without going through the bind process all over again.
With Wireless Trainer Link, You Can:

  • Wirelessly “buddy box” with another DSMX®/DSM2® transmitter when teaching someone to fly.

  • Assign gimbal functions to a second “camera” transmitter when flying a camera drone so you can focus on avoiding obstacles and maintaining visual contact while the camera operator lines up the shot.

  • Link with specially equipped Spektrum™ FPV headsets to wirelessly control head tracking.


  • Spektrum™ iX20 SE transmitter

  • New iX20 Special Edition dual transmitter case

  • New iX20 Special Edition lanyard style neck strap

  • 10,500mAh Li-Ion transmitter battery pack (installed)

  • Short and long optional stick ends

  • Screen protector

  • USB magnetic adapter cable

  • Magnetic micro USB adapter

  • Orange grip set

  • Orange switch nut set with wrench

  • Quick start guide

  • iX20 decal sheet

Available from:
Available from:

Phoenix K8B Scale Sailplane

The Ka8B from Schleicher is a single-seater from the 50s, which due to its robust construction is mainly used as a training aircraft for beginners. This faithful replica from Phoenix - with a wingspan of an impressive 4.50m - is manufactured using the latest laser-cut technologies as a light and high-strength wood construction, which inspires with an enormous level of detail.


  • Extremely light and high-strength, laser-cut wooden construction

  • Two-part wings

  • Two-part fuselage

  • Detailed cockpit

  • Removable canopy

  • Prefabrication level of 95%, fully covered and painted

The model is made in extremely light and high-strength, laser-cut balsa wood construction. The design impresses with an enormously high degree of prefabrication, which means that the construction effort is almost reduced to the installation of drivers and electronics. The model is prepared for spoilers (EFL491009) and is also completely covered with top quality Ultracote.
The KA8B from Phoenix Model has numerous scale details. Many beautiful detailed solutions make the model look like the original. A special highlight is the detailed cockpit and the finished painted pilot figure. But the model is not only similar to its prototype on the ground but the KA8B also has an impressively true-to-life flight image in the air. The 4 piece wing and removeable tailplane make for easy transport. It can be fitted with an electric motor (around 2000 Watt) for self launching or it can be easily aero-towed behind a 50cc or larger tow plane.

The model offers excellent soaring performance so long flight times are easily achieved.

What you need

  • Radio and receiver

  • 5 x servos for ailerons. flaps and rudder

  • 1 x servo if aerotow release is used

  • Motor

  • LiPo battery

  • ESC

  • Spinner

  • Propeller

Wingspan: 4500mm (177 in)
Length: 2105mm (83 in)
Flying weight: 6800gr – 7000gr
Wing area: 123dm2
Wing loading: 55g/dm2
Air Foil: HQ airfoils
Flap: 2 electric flaps 440mm (not included)
Spinner size: Aluminum H hub propeller holder, shaft 8mm (not included)
Motor: brushless outrunner 1480W, 450 KV (not included)
Experience level: Intermediate
Plane type: Glider


Motor: RIMFIRE 1.20 (not included)
Lipo: 6cells X 2 (not included)
Esc: 100A (not included) 

Available from:
Available from:

Voyager F5J is constructed of ultra premium carbon fiber with a 157" wing span. Kit includes  three-part wing, two-part fuselage, elevator, stabilizer, two horns, plug-n-play, two carbon rods, hardware and a building guide to build your F5J Voyager.

Wingspan: 156 in. (3962mm)
Wing Area: 83.6 dm2
Airfoil: Voyager18
Length: 76in. (1930mm)
Weight: 32 oz (908g)
Controls: Elev, Rud, Ail, Flaps
Features: Two part fuselage two part Cross Tail
Parts: Plug-n-Play, two carbon rods

Basic parts that are needed.

Carbon Prop
CNC Motor Mount Brushless ESC with BEC
Altis V4 Plus
4 KST Digital Servos
4 IDS with frames
Hyperion 3S 900HV 

Available from:
Available from:

Neutrino F5J
The wing of the Neutrino F5J consists of 4 parts, the fuselage consists of 2 parts, which greatly simplifies its transportation. The longest part is the wing tip has a length of 1120 mm. The wing Neutrino has serie of airfoils DI8120...820 specially designed for ultra light F5J gliders. It has thickness changing from 6.9% on the root to 5.0% on the tip, that much thinner than airfoils for F3J that are used for F5J early. This airfoils has great performance in wide speed range due to special geometry and the explicit reaction to the change of the flaps position depending on the flight mode.Soon it will be possible to order the assembly works Neutrino F5J with the installation of equipment and electronics

Neutrino F5J
Weight version

Color of top

Product info
The wing and tails made by solid core technology from PMI foam (Rohacell core). Neutrino is available in two versions. Standard version has about 1350 g flying weight. Its wing made from checkered carbon fabric 62 g/m. Standard version can be used with ballast.

Light version has flying weight from 1150 g. In this version wing made from spread carbon 28 g/m2 and has less rigid spar. Light version is not recomended for using with ballast.

Production time
Production time for Neutrino F5J at the moment is about 30...45 days 

Available from:
Available from:

Kappa 35 F5J
Special features of this model include:A well designed low drag fuselage with a large canopy 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 low speed tight thermal turns, allowing the model to be thermalled away from small, weak thermals with ease. This allows competition winning low starts to be made with confidence. Despite its extremely good thermal performance the wings maintain a good L/D up to higher speeds, allowing the Kappa 35 to return from a long way downwind with ease.

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 plane was designed and optimised for electric gliding from the start, it is not a modified F3J design. This has allowed a high aspect ratio to be used and more suitable airfoils. 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 hours. The wing breaks down into three pieces and the tailplane and fin are easily removable, allowing the model to be easily transported to contests.

The model is available in three composite layups: Light - 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 7% more. Light Strong SC - 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 23% more. For all wing layups the fuselage is all carbon. The top of the fuselage is painted and the underside is left in natural carbon black. This looks very attractive. For all electric models (irrespective of the fuselage construction) we recommend te 2.4GHz aerials are exited from the fuselage, so they are in the outside airflow. One horizontal and one vertical aerial usual works well. There is too much electrical equipment in an electric glider fuselage to 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.

Kappa 35 Specifications

  • Wing span: 3.5 m 138 in

  • Wing area: 60.0 dm2 930 sq in

  • Length: inc spinner 158 cm 62 in

  • Flying weight from 1275 g 45.0 oz

  • Wing loading: 21.3 g/dm 7.0 oz/sq ft

  • Aspect ratio: 20.4

  • Wing airfoil Proprietary EDA (dihedral): 5.0º

  • Spinner Diameter: 38 mm

  • Centre of Gravity: 85-93 mm from wing leading edge

  • Controls Rudder, elevator, ailerons, flap, throttle

Kappa 35 Light Layup Typical Weights

Fuselage & pushrods 166 g 5.9 oz
Wing centre panel 328 g 11.6 oz
Wing Tips 260 g 9.2 oz
Tail Plane 50 g 1.8 oz
Fin 34 g 1.2 oz
Accessories & glue 12 g 0.4 oz
Total structure 850 g 30.0 oz
Wiring 30 g 1.1 oz
Receiver 12 g 0.4 oz
Rudder servo 10 g 0.4 oz
Elevator servo 10 g 0.4 oz
Wing servos (4) 40 g 1.4 oz
Speed control 45 g 1.6 oz
Motor 120 g 4.2 oz
Prop & spinner 28 g 1.0 oz
Battery 130 g 4.6 oz
Flying weight 1275 g 45.0 oz

Recommended Servos
Elevator & rudder MKS DS6100, MKS HV6100, KST X08 Aileron MKS DS6100, MKS HV6100, KST X08 Flap MKS DS6100, MKS HV6100, MKS DS6125 Mini, MKS HBL6625 Mini, KST DS135MG

The kit comes with CNC cut plywood fuselage servo mounts designed for the MKS DS6100 and HV6100 servos, so it is easiest if these are used for the tail surfaces. Kappa 35 Control Movements Rudder 20 mm each way Flap 85 degrees down Ailerons 15 mm up, 12 mm down Elevator 10 mm up, 10 mm down Recommended camber settings (measured at flap root TE) Speed mode -1.5° (flat bottom surface) Cruise mode 0° (flat top surface at hinge) Thermal mode +2° (2 mm down) 

Available from:
Available from:

Aloha F5J
Aloha 3-meter F5J competition sailplane with X-tail. Aloha covers ground! Plus, its 3m wingspan gives the Aloha the edge in working tight, low level thermals, and its DLG heritage ensures great “hang time.”

Wingspan: 118in (3m)
Wing Area: 778 sq.in. (50.2dm2)
Wing loading: Approx. 4.9 oz/sq.ft (14.9 g/dm2)
Airfoil: DI890~DI820; 6.5~5.0%
Weight: 26.45oz (750g) approx. flying weight
Controls: R/E/A/F/Thr
Features: 32mm Spinner Diameter
Motor type: Neu 707/2y/P16
Battery configs: Lipo
Channels7: channels

Aloha F5J is an ultra-light competition sailplane from the maker of the highly successful Boom and Stiletto Lift DLGs. Data and experience gained from these F3K models has taken Jim Aero in an innovative, new direction; a new way of looking at F5J.

Aloha F5J has a 3-meter wingspan and flying weight of only 750g. In typical Jim Aero R&D method,  the new Aloha F5j was designed using computer modeling and followed by experimental testing. Aloha is built to be rigid and light weight. The wing and tails are made with solid XPS core. Its new family of airfoils have a high aerodynamic efficiency over a wide range of flight speeds and exhibit a very low sink rate. In windy conditions or calm, Aloha covers ground! Plus, its 3m wingspan gives the Aloha the edge in working tight, low level thermals, and its DLG heritage ensures great “hang time.”
Two versions of tail are available: V-tail and classic X-tail.
The equipment layout is compact and efficient.
Suggested Motor: Neu 707 with 4.4 gearbox
Suggested Prop: RFM 12.5x7
Suggested Servos: MKS DS75K
Suggested ESC: Castle Talon 35A
That's all from the Thermal Circle happy safe and successful RC soaring.  Hayden Daley 2021.

Available from:
Available from:

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