Firebird (oz90)

 

Firebird (oz90) by EJ Webster from Keil Kraft 1960 - plan thumbnail

About this Plan

Firebird. Keil Kraft kit plan for a 32 in wingspan control line stunt and combat model for 2.5cc engines, with particular styling.

Update 08/09/2013: Have re-sized this plan to full-size at 32in wingspan, thanks to RogerC.

Update 30/09/2020: Added kit instructions, thanks to Martin Cox.

Quote: "Building and Flying your Keil Kraft Firebird.

The Firebird is a robust and easily built model which is capable of a really good performance, even in the hands of the not-so-experienced pilot. Any 2.5 cc motor in reasonable condition will enable the model to perform loops, bunts, eights and square manoeuvres, whilst with a really hot motor, you will have a formidable combat plane.

In order to get the very best from your Firebird, take care to build and align the model accurately, and for maximum strength it is advised that all joints are pre-cemented. This means lightly coating the two surfaces to be joined, allowing the cement to set and then recementing and joining the surfaces. Keilkraft or Britfix cement are recommended as being the very best and most reliable for all purposes.

Follow the building sequence below and you will find no construction difficulties. Whilst waiting for the cement to set on one part, you can proceed with another, so re-ducing building time to the minimum.

Building Sequence

FUSELAGE:
1. Cut the engine bearers to length and cement to the fuselage. Allow to set. The hearer spacing as given on the plan will suit almost all 2.5 cc motors at present on the market, but if you are fitting a motor with a closer hearer spacing (e.g. the O.S. Max 15) move the top hearer down, filling the gap above it with scrap balsa.
2. Cement the two 1/32" plywood side skins in place and lay the assembly on a flat surface, weighting it down to ensure good contact between sides and fuselage and leave it overnight until completely set. Particular care should be taken with fuselage joints to avoid introducing possible sources of weakness.
3. Sandpaper the fuselage and give two or three coats of K.K. sanding sealer, sanding smooth between each coat. Drill the engine hearers to suit your engine and drill holes to take the tank fixing bolts.

WING:
1. Cut the trailing edge pieces and spars to exact length. Pin one trailing edge strip in place on the plan and pin one of the 1/2 x 1/8 leading edge strips to the plan at the building jig position. This will support the ribs during building.
2. Cement all W2 ribs in place on the trailing edge taking care that they are parallel and vertical, using modelling pins as necessary. Cement a 1/4 x 3/16 spar in position, then ad ribs WI and a leading edge strip. Allow to set then add the other trailing edge piece. When this has set, remove the wing from the plan and complete the leading edge as detailed on the plan.
3. Drill the 1/8 ply bellcrank mount to take a 6B.A. bolt. Place a washer on a bolt, thread it through the hole, add another washer and a nut which should be tightened firmly.
4. Bend the inner ends of the leadouts to the shape indicated in the sketch on the plan, clip them on to the bellcrank and solder the ends of the loops closed. Cut the flap push rod to approximate length, bend one end as in the side view on the plan and attach to the bellcrank by soldering a cup washer to the end.
5. Place a washer on the bellcrank mounting bolt, followed by the bellcrank and another washer. Check that the bellcrank is the right way up and then add a 6 BA nut. Adjust this nut so that the bellcrank moves freely but without rocking and solder the nut in place. Cut off any surplus length of bolt.

6. Hold the wing so that the spar is at the bottom and thread the leadouts through the holes in the ribs of the inboard panel from the centre section to the tip. Cement the bellcrank mount securely to the spar and ribs W1 so that the head of the bellcrank mounting bolt lies just in front of the spar. Next cement the bellcrank brace in position on the inboard side of the bellcrank mount. Add the remaining wing spar.
7. Cement pieces W3 (wingtips) in place, first marking the positions of the leadouts on the inboard tip. Note that the leadouts are on the underside of the tip. Add pieces W4 and W5, notching one of the W5 pieces to clear the front leadout wire. Slide 1 inch lengths of tubing on to the leadouts and sew and cement in place to W3.
8. Sheet the centre section top and bottom with 1/16 sheet, making a cut-out in the upper sheeting to allow the push-rod to pass through. Install the outboard tip weight - about 3/4 oz of lead or solder between the spars where shown on the plan and secure in place with cement and the two 1/16 sheet webs.
9. Cement the outboard flap to the flap joiner, having first rounded the edges, bolt the flap horn securely in place and hinge the flap to the outboard wing. Use tape to form the hinges as shown on the plan. Connect the push rod to the flap horn so that the flap is neutral when the bellcrank is at the centre of its travel and bend the ends of the leadouts to form clips (see plan).
10 Slide the fuselage over the wing from the inboard tip and check that it is a snug fit. Cement the fuse-lage to the wing making sure that is is square. For additional strength, cement silk or linen fillets to the wing/fuselage joint from the spar position forward. Now add the other flap, hinging it to the trailing edge and cementing to the flap joiner.


FINAL DETAILS:
1. Round off the edges of the tailplane and elevator, hinge together with tape, then cover with tissue, using clear dope or sanding sealer as adhesive. Clear dope and cement firmly to the fuselage. Bend the elevator push rod to shape and attach it to the flap horn. Next attach the elevator horn to the other end. Bolt the elevator horn to the elevator so that both flap and elevator are neutral together. This is an important step, though quite a simple one, so make sure that you get it right.
2. Cement the fin and fin fairing together and when set, round off the edges (except that which cements to the fuselage and tail) and cover on both sides with tissue. Clear dope and then cement the fin in position. The front end of the fin fairing should be offset so that it is over to the left (inboard) side of the fuselage and the rear edge of the fin should be over to the right (outboard) side. Mounting the fin at this angle helps to maintain line tension.
3. Cover the wing with heavyweight Modelspan, using one piece for each wing panel (four pieces in all). Spread tissue paste round the outline of a panel, dip the tissue in water, squeeze out then carefully open out the tissue and shake off any surplus moisture. Lay the tissue in place and gently pull the edges until the tissue is laying evenly in place, then trim the edges. This method of covering may sound startling if you haven't come across it before, but we can assure you that it works ! Repeat for the other panels. When dry, apply three coats of clear dope. The flaps should be covered in the same way as the tailplane.
4. Colour the model as required, taking care not to clog the hinges and leadout tubes with dope. Install the tank as shown on plan, bolt the engine in place, connect to the tank and your Firebird is complete.

FLYING
The Firebird has been flown on line lengths varying between forty and fifty five feet. Three-strand steel wire is recommended and a length of fifty feet seems the most comfortable, except on rare calm days when another five feet can be used. With the recommended 8 x 8 prop. (Truflex for preference) the model is fairly fast, which means that there is plenty of line tension at all times — a very comforting thing.

There is no need for the launcher to run with the model. He should be instructed to hold the model by the outboard wing panel and release the model by gently pushing it forward - with a powerful engine, all he need do is to let go! Make sure that the elevator is neutral or very slightly up and the plane will fly smoothly away. You will find that it flies very smoothly and can easily be flown 'eyes off' - a useful attribute for combat when you want to keep an eye on your opponent!

If you have any experience of stunt flying, you will find no trouble at all in performing any manoeuvre with your Firebird. Should you be a newcomer to stunt, make sure you are thoroughly accustomed to the model before trying anything. You will find that your plane will turn very tightly indeed without losing much speed or falling in on you. As you become more experienced, open out the loops until you can fly four or five smooth, round loops at a constant speed. Remember, the only way to real proficiency lies through constant practice. We wish you good sport!"

Direct submission to Outerzone.

Quote: "Hi Mary, I still have my model, built 1965 with a ED Racer up front."

Supplementary file notes

Instructions.

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Firebird (oz90) by EJ Webster from Keil Kraft 1960 - model pic

Datafile:
  • (oz90)
    Firebird
    by EJ Webster
    from Keil Kraft
    1960 
    32in span
    IC C/L
    formers incomplete :(
  • Submitted: 03/04/2011
    Filesize: 436KB
    Format: • PDFbitmap
    Credit*: keven64

Firebird (oz90) by EJ Webster from Keil Kraft 1960 - pic 003.jpg
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Firebird (oz90) by EJ Webster from Keil Kraft 1960 - pic 004.jpg
004.jpg
Firebird (oz90) by EJ Webster from Keil Kraft 1960 - pic 005.jpg
005.jpg
Firebird (oz90) by EJ Webster from Keil Kraft 1960 - pic 006.jpg
006.jpg

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User comments

Hi Steve and Mary, Thanks for running a great site. I attach several photos of the KK Firebird I built recently from a plan downloaded from Outerzone [more pics 003-006]. I had built two Firebirds when I was a kid and I recall that they were wonderful flyers. it was great to find the plans on your site and it allowed me to build another one again. There are some minor distortions on the plans, the key one being that the fuselage cut out for wing is slightly asymmetric. As the plan does not provide a template for the rib, the only reference to allow the rib template to be drawn up is the fuselage cut out for the wing. Take note that when drawing the rib, not to just trace the entire cut out shape but to draw a top half of the rib and then copy and flip over produce the bottom half. This way, you will get a symmetrical rib template. Many thanks.
TonyLeong - 09/09/2016
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Scaling

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