K4 (oz14452)


K4 (oz14452) by Bill Bowne 2021 - plan thumbnail

About this Plan

K4. Radio control sport model for electric power. Wingspan 30.7 in, wing area 168 sq in. Foam construction.

Direct submission to Outerzone.

Quote: "K4 (named for the KFm4 airfoil) started as a simple test bed for the KFm4 airfoil. As I drew it up, I added the objectives of making a one-piece model, and of making a model that weighed less than the FAA’s 250 gram registration limit. Well, objectives 1 and 2 went well, but I missed on # 3 by a fraction of an ounce.

K4 is an good utility flier, much like a small Ugly Stik. It can handle surprisingly high winds, is easily portable, and is pretty robust. So much so that I wound up giving it away to a returning R/C flier as a refresher model. It is a very easy bird to fly, but building it requires some careful planning (especially with the servos).

Most of the K4 is 6mm Model Plane Foam (MPF). The spar is 1 x 6 mm carbon fibre, all hinging is with Blenderm tape. Power is supplied by a 1300 Kv 'Blue Wonder' motor, turning an APC 7X4E. Electricity comes from a 3S350 lipo, via a 10 (or 12) amp ESC. The aileron servo is a Turnigy XT900, with the rudder and elevators controlled by Turnigy XT500’s. All servos are held in with hot glue.

Glues used: Clear (NON-Foaming) Gorilla Glue (GG), thin CA, hot (gun) glue, and Foam-Cure/Foam-Tac.

To make the model one piece, I squeezed the aileron servo through the wing top, with the pushrods running between the rudder and elevator servos. For the aileron torque rods, I laminated light ply bases, beveled them to match the ailerons, and clear GG’d nylon micro control horns to the wooden torque rods. If you use different servos, you may need to adjust the servo positions, so plan ahead!

Wing: CA the spars together with the 1/16 joiner. On a jigged surface (I use two flat boards, hinged together and covered with plastic sandwich wrap, aka 'Saran' wrap), glue the middle wing panels together and GG the spar into the wing. When cured, spread thin layers of clear GG (use an old playing or credit card to ensure only a thin layer of glue is applied) on the top and bottom panels and glue those to the middle. Weight the whole thing down and let it cure, then sand in the airfoil and cut out the aileron servo slot.

Assemble the torque rods, bevel them, glue them into the ailerons, and bevel those. The aileron hinge is on the top (as is the elevator hinge).

Hot glue the aileron servo into place, then hinge the ailerons and add the aileron pushrods (I used 1/32 music wire for all pushrods).

Fuselage: Trial fit everything! Glue the rudder & elevator servo mounts in place, then hot glue the servos into them. Sew the landing gear to F2 with braided fishing line (not monofilament), then soak it with thin CA and set it aside..."

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K4 (oz14452) by Bill Bowne 2021 - model pic

  • (oz14452)
    by Bill Bowne
    30in span
    Electric R/C
    clean :)
    all formers complete :)
  • Submitted: 13/02/2023
    Filesize: 577KB
    Format: • PDFvector • CADfile
    Credit*: BillBowne
    Downloads: 491

K4 (oz14452) by Bill Bowne 2021 - pic 003.jpg
K4 (oz14452) by Bill Bowne 2021 - pic 004.jpg

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