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Key Features

  • Top-quality balsa and plywood construction
  • Covered in Hangar 9® UltraCote®
  • Fiberglass cowl and wheel pants


Seagull Models goes the extra mile with the new Decathlon .40, an affordably priced, high-quality aerobatic high-wing aircraft for sport and scale modelers. Intermediate to advanced aerobatic pilots looking for superb sport performance at a very reasonable price can’t go wrong with this Seagull plane.

CG (Center of Gravity): 3 1/8–3 1/2, 3 1/8–3 1/2
Control Throw (Ailerons): 3/8 in, 3/8 in
Control Throw (Elevator): 3/16 in, 3/16 in
Control Throw (Rudder): 3/4 in, 3/4 in
Flying Weight: 7–8 lb, 7–8 lb
Hardware Included: Y
Recommended Environment: Outdoor
Spinner Size: 2.25
Wingspan: 67.75 in (172 cm)

Parts Listing

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Product Support Tips

What engine should I choose?

Choose the lightest weight, highest power engine you can find, for the best performance within the engine recommendations. The Evolution 46NT is a very good choice for this plane for great performance with low weight.

What radio system should I choose?

You can use any 4-channel radio system, and you will need 6 servos.

What servos should I choose?

Standard servos are more than adequate for the plane. But keep in mind that the better servos you use, the better the plane will fly.

What can be done to increase the performance of the plane?

Using a computer radio, you can mix elevator and aileron to rudder to make knife-edge track straight. Keep in mind the lower the weight of the plane; the better it will fly, so keep additional weight to a minimum.


The hinges are not pre-installed as stated, the hinge slots are cut, the hinges are installed in the surfaces, but it is required to remove them and glue them as described in the steps on pages 4-7.

Installing the Aileron Servos

You can use 1" servo arms on the servos to get the arm of the servo outside of the wing, part number JRPA212 will work well for JR servos.  Standard length arms will work however.

Wheel and Wheel Pants

Use some threadlock on the nuts holding the axles on the landing gear to prevent them from loosening.

Aligning the Horizontal Stabilizer

Step 4

Pay special attention to the cautions in the manual, which mention not pressing hard with the knife when removing the covering from the horizontal tail. If it is cut to deep, it will fail.

Vertical Stabilizer Installation

Step 4

Pay special attention to the cautions in the manual, which mention not pressing hard with the knife when removing the covering from the vertical tail. If it is cut to deep, it will fail.

Wing Strut Installation

1) Cut a slot in the covering on each side of the fuselage for the aluminum plate to exit the fuselage.
2) Mount the aluminum plate into the ply mount in the fuselage using the provided wood screws after pre-drilling the holes.  The exact position of the plates is not critical.  The mounting hole of the plate for the wing struts should to be far enough outside the fuse to provide room for the strut to clear the fuse.

3) Thread wing strut mounts into the pre-installed nuts in the wing panel, using a drop of threadlock on the screws to prevent them from loosening.  In case the covering in your kit is not removed at the screw locations, hold the wing up to a light, and the holes should show up as a darker spot on the wing.  The locatations are approximately 11" from the wing tip, and one is approximately 1 5/8" from the wing trailing edge, while the other is approximately 3 3/4" from the wing leading edge.

4) Attach the wing strut clevises to the wing strut mounts, adjust the length of the strut by loosening the set screw on the strut and pulling or pushing the metal rod to make the strut the length needed and re-tighten the set screw.  Then attach the wing struts to the fuselage strut mount using the provided screws and nuts.  Use a drop of threadlock on the screws to prevent them from loosening in flight.

Balancing and Flight Preparation

The balance point is 8-9 cm which is approximately 3 1/8" – 3 1/2” behind the leading edge of the wing, measured at the fuselage or at the wing tip, as the wing is square. This is from the very front of the wing. This kit balanced without any added weight. Move the battery pack around as much as possible to achieve the proper CG withough added weight. Add lead only if necessary. Do not fly the model with an incorrect CG!
The control surface throws listed on page 23 for the elevator and aileron are incorrect.  The correct throws are listed in the grey shaded box on page 22.

Product Support