Wing span
Wing area
Wing load
Structure 2 Flaps, 4 Ailerons, 2 Spoilers
4 pieces wings and winglets
Wing area
Flying weight
Radio gear
10 servos (or 6 servos)
1320mm (up to the rudder end)

Flash is a glider developed by Thomas Schmidt (Germany) and Let model that is classified in such a unique category as between scale models and sports model such as F3J. The prototype of Flash had been developed based on the Sperber Junior, a glider real world and was named Sperber II. Flash is a evolved model from Sperber II. However we can not figure out an original Sperber from the skinny fuselage of FLASH. FLASH has won to get its own originality.
In general, those models called as F3X fly in the thermals being generated below about 300meters high. The FLASH is one of big models wider than 4m. It can fly at 300 - 450 meters high, using motor power. This layer in the air with this altitude is comparatively stable, which is different from the eventful air near the ground surface. The flight performance of FLASH is superior to the scale models, because FLASH has good thermal duration capability. Therefore the FLASH is the model that can be enjoyed as both the scale model and the F3J thermal ship. It is to my regret that the wing is not molded. The FLASH is not a quite new model. Though many years passed, since it was unveiled, the uniqueness still remains.

Thomas Schmidt(Germany) / Let Model. (Czech Republic) Mail to RC-sailplane.com

TUN Modellbau(Switzerland) And Partners of LET MODEL

FLASH climbs into the blue sky with this angle. Dihedral is comparatively heavy. FLASH dedicates the thermal duration. It is doing loop-the-loop.
Terrible. But loop-the-loop was successfully. The aero foil is abach (wooden). On the contrary, it seems to be stabler

The control is comparatively easy, because of fewer stall.

It flew over our head. It was so powerful.

Passing is very exciting with cool sound. This picture may give an impression that FLASH is well on a thermal.
The front view is also cool with wide wing and skinny fuselage. Flash is ready to dive.

Flash was only 5m high from my head. FLASH restarted to ascend again.

FLASH is approaching for landing. The flap and spoiler are coming. The man who hold FLASH is Mr. Yamada, a pilot with skilful. The model at lower left is his FLASH. He crashed his FLASH. The know-how obtained from his FLASH are inherited to my FLASH. Mr. Yamada and his friends.
The big Motor is outer runner, The 5 pieces of batteries are both for the receiver and for counter ballast.
The battery is of FLIGHT POWER 5 cells 3200mAH, so powerful. The radio gear bay appears after removing its cool canopy. This bay reinforces the fuselage so that the open portion could not be opened more by combining both sides of fuselage.
Because canopy is white, it does not look a canopy, but part of fuselage.

The battery is equipped on the bay. Mr. Yamada mainly installed motor as well as selection of motor, amp and propeller. Mr. Hirata installed servo and receiver and wiring.

The receiver is made by FUTABA, G3 type which has 12 ports with battery ports and two virtual ports. 13 physical ports are occupied fully.(one of port is used by battery indicator.

The rudder and its fin are molded. It seems that Aerofoil may be molded easily.

The elevator is directly driven by the servo built in the tail fin.

The elevator can be easily removed.

This photo is presented by Canadian flier.
Spoiler works well. if the butterfly is used simultaneously, it will be effective. This is the cross section at the root of aerofoil. The hook was for binding two aerofoil pieces by the spring. It is not necessary in usual.
The FLASH yellow version The retractable gear unit is an option. Winglets are molded.




1)Aerofoil profile
It is of Helmut Quabeck(HQ), which is used for the scale models in usual.

Abach (block board) is adhered on the styrene foam core. It is one of conventional method. But only winglets are molded.

3)Flap, aileron
4 ailerons, 2 flaps and 2 spoilers are equipped on the main wing. Hinge is taped, but covered by Oracover. It is also conventional.

JR DS362 are used for all. Any servos with torque 3kg are required.


1) Fuselage structure
(a) Fuselage of glider version and radio gear.
Twelve servos are required totally, which are for four ailerons and two flaps and two spoilers, an elevator, a rudder and motor. Physical ports of FUTABA G3 receiver. The last one is used for battery. The retractable gear is not installed in the white FLASH shown by above pictures.

(b) Fuselage of motor version

There are many examples of motor installation in case of small size. In case of big model, there are few examples. In addition, the state-of-the-art changes quickly. Even though there was a good experience for the selection of motor, amplifier, battery and propeller, it might not be applied for the current products. For example, there was no LiPo battery a couple of years ago. Therefore we must do trial and error for the products for the bigger models in order to know which is the best combination. Mr. Yamada is one of skillful pilots of motor glider. He has many experiences for installing motor to the scale glider and sports glider. So I depended on all, that is, installation as well as product selection. He had tried to fly his FLASH, before I asked him to assemble my FLASH. He had crashed his FLAS two times, because FLASH was the first experience for him too. But owe to his trial, my FLASH need not to be crashed. The following is one of recommendations proved by Mr. Yamada. Until he found out this combination, much investment must be required. I appreciated his challenging spirit so much.

(Plan-1) Proven by this web site.
Motor:AXI 4130/16
Speed Controller:Hypelyon 80A
Propeller: AeroNote 18x11または17x13
Battery:Flight PowerEVO20 18.5v 3300mA (5S1P) (20C dischargeable continuously, 30C burst dischargeable)

(Plan-2) Recommendation by Let Model
Motor: TM 350-28 14pol 16w
Controller: Hacker Master 70-3P-O
Propeller: Graupner 16x10
Batteries: LiPo (cca 3.200 mAh)

2) Tail plane
The elevator is directly driven by a servo built in the fin. The structure of elevator is made of abach, the same as the main plane. Rudder and fin are molded. Rudder is deriven by a servo installed in the servo bay by the twisted wire. The twisted wire is flexible and easily bent in the guide tube, so the exposed portion at outside of tube must be reinforced by the grew so that the wire can not be bent.

The figure shown below is quoted from "Secret of thermal Soaring", a video software sold by Radio Carbon Art company which figures out the air flow phenomena in the convective layer of the air. According to this figure, RC Soaring layer is only 300 meters thick above the ground surface. The name of RC Soaring layer is given by the author and is not used in the science text book. However, it is easily accepted and recognized by those who enjoy RC Soaring that the thermals are generated and vanished within this layer. We can accept through our RC experience that the thickness of the RC Soaring layer is only about 300m. As for above RC Soaring layer boundary, I can not figure out exactly, but it will be the atmosphere with only blowing wind.
FLASH is a big ship and can be seen even above RC Soaring Layer. The two small ailerons are enough to control its attitude at the high altitude. FLASH will turns with bigger circling slowly. It is the flight of the big ship.

Radio Carbon Art

Quoted from a video "Secret of Thermal Soaring" 

The boundary of RC Soaring layer is not fixed at 300 meters high, varies up to about 540 meters high. Above its boundary, the air flow is becoming stabler and reaches to the convective flow boundary at about 1000 meters high, where the air seems to flow constantly with little change.
By the way, there is another boundary. It is the ground surface where the velocity is equal to zero on the surface. In the famous book "Old Buzzard's Soaring Book by Dave Thornburg, but is not available now, the concept of River of Air. When the RC fliers stand on the bottom and look up, then he will find "the river of air ". The velocity of flow is zero at the bottom of the river of the air. You may figure out air flow layer if you overlapping the concept of " the river of the air".
The predecessor of FLASH is Sperber II which is based on Sperber Junior. Sperber II can be launched by single hand and was not required by throwing by the friend like a big scale model. FLASH can be launched by single hands. But it is safe to ask somebody to throw FLASH as an personal remarks. The motor explained above is very strong which can lift FLASH easily up to the high place and is enable FLASH to fly as a acrobat model. However the dihedral of FLASH is comparatively deep , therefore Knife-edge is not so beautiful. Loop-the-loop is good.

At landing, the butterfly and spoiler work well. The main frame has 4 aileron and 2 flaps. The two middle inside aileron and two flaps are used for the butterfly. The outside aileron is used as aileron at the butterfly, which enable us to control attitude.
CG&Standard Trim :
Center of gravity and standard trims are available as shown bellow.
Items Standard trim etc.
CG 80mm from leading edge
Elevator -7/+9
Rudder -25/+25
Ailerons -10/+15
Flaps -3/+5