I thought up the Flying Star idea after learning about the "Most Unusual Model" event at the VMAA Trophy an interclub competition held annually in Victoria.
The event usually attracts Flying Witches, Stop Signs, Flying Saucers, Porsches & even Flying Lawnmowers as well as a plethora of other non aeronautical devices. I reasoned that if any one of these objects could defy laws of gravity and the laws of Aerodynamics then a Flying 5 pointed star would be a definite possibility. After all, is not a Star a heavenly object ?
The Ninja Star was designed with the help of Malcolm Hardy's "Winfoil" CAD program, without which I would have had to build many mock ups before arriving at my 1.0m span prototype model. The model described in this issue is the 1.12m Ninja Star version 2, it is a surprisingly quick and easy to build model and even more surprising for a such a radical design is quite easy to fly. Suitable for intermediate flyers/builders that want to try their hand at something different.
The model's name was coined by a fellow LDMFA club member after watching one of the prototype's test flights. I forgot my pre-flight check and took off with aileron throws reversed, as soon as Ninja Star rotated I cartwheeled the model giving the impression of a Ninja throwing star, hence "Ninja Star".
All wood construction with plywood fuselage sides and formers. Spars are spruce & balsa with solid wing tips made from ply & balsa sheets.
The model needs to be framed up flat on a large building board. Chordwise you will need at least 860mm, slightly larger for comfort and at least 1.2m width. A 1m x 1.2m x 25mm sheet of Medium Density Fiberboard (MDF) is ideal.
The plan shows 12.5mm square x 250mm hardwood bearers which provide the spacing to suit the typical .46 Engine beam mount dimension. Be sure to adjust the bearer spacing at this stage to suit the engine you intend to use. Do not use a radial mount.
Position both fuselage sides, outside down, & mark out the bearer, firewall and F2 positions. Glue bearers in place, position & glue firewall, tank floor and former F2 into place ensuring that fuselage sides are square in all respects.
When set trial fit engine, if bearers need adjustment (filing, grinding) now is the time, but do not drill engine mounting holes. At this stage you will need to cut the nacelle/cowl sides to give clearance for muffler and needle valve.
Determine throttle control and fuel line locations and drill holes in firewall to suit. Fasten nose gear bearings to firewall at this stage.
Place R1 on the outside of fuselage sides, but DO NOT GLUE. Draw a line on the fuselage sides along the upper contour of R1.
Cut eight 9.5mm sq. stand off posts P to size using the R1 outline drawn on fuselage sides as a height guide, CA all the Posts P in position, 4 on each side.
Place plan over building board and cover with plastic cling wrap or similar glue proof covering.
Do not stick pins through the spars, cross pins over the top of them. Pin the spruce spar in place followed by the diagonal 6.5mm sq. trailing edge/bottom spars both sides. Pin rear 6.5mm balsa spar in place. Position leading edge stock in place. Do not pin.
Position fuselage in place over spars and leading edge, noting that the rear cut outs in the fuselage for the diagonal spars may need some relief.
Glue fuselage into place but do not glue leading edge yet. Glue gussets G2 in place both sides (flat on board), ensuring the outer edges are in line with the outer edge of R3.
Position and glue B4, rear floor, F4 and F3 into place, noting that F3 is installed at a slight angle to allow for piano wire main gear crossover. If you intend to use dual elevator servos be sure to put two servo cut outs in rear floor. Position and glue ribs R1 in place, but as before, do not glue the leading edge yet. Position ribs R2, R3, R4, R5, and R6 into place. All ribs should sit flat on the board and be square and parallel, R4 is glued hard up against R3.
Install the 6.5mm sq. top spar, careful to note that itŐs inner ends fits flush against the fuselage sides. When satisfied that all ribs are a good fit press leading edge firmly into position and glue all joints.
Glue the Horizontal Stabilisers HS into place. Position and glue the wing webs W1 and W2 into place, NB these are NOT sheer webs, and the grain should be horizontal.
Cut the 12.5mm sq. forward leading edge to shape and glue into place. Use R2 as a reference to position the forward leading edge the same on both sides. Trim Braces B1 and B2 to size and glue into position.
Unpin and unstick your creation from the building board. Cut off any excess spar, leading edge protrusions from wing tips, and sand flush.
Install spinner to engine and position engine so that rear face of spinner is 1.5mm ahead of front face of fuselage. Drill engine mounting holes allowing for 1 degree right thrust and install blind nuts.
Glue gussets G1 and nacelle floor into place. Temporarily install engine/spinner and contour front of fuselage to blend to spinner. You will be required to build the front section around and inside of fuselage up with scrap balsa block, build up/ grind away/sand until you are satisfied with contour/blend of spinner/fuselage shape.
Cut notches in B1 and B2 to suit your positioning of the 5mm sq. stringers, then position and glue into place, whilst being certain that both sides are the same, add the 1.5mm gussets where inner stringer butts against upper spar.
Blend/sand the 12.5mm sq. front leading edge to shape.
Sheet the upper surface of wing as shown using 1.5mm wing sheeting, add front sheeting between forward leading edge and outer stringer and between R1 and the fuselage side.
Construct and attach wing tips. Use glue sparingly, or better still use Silicone RTV. In the event of accident its better that the wing tip knocks off than structural damage occurring.
Drill the 4mm holes in rear floor just forward of F3, one next to each fuselage side for main gear legs. Install both B3 braces 4mm forward of F3.
Add the Popes Nose B4 and all Servo and hatch mounting rails.
Make up the top hatch, with provision for pilot/cockpit if desired.
Prepare ailerons and elevators for covering - NB DO NOT taper or round off trailing edges, leave sharp 90 degrees.
I used OzCover materials to cover my bare bones, OzCover White on top for a beautiful silky pearl lustre, with Saturn deco Trimming and OzCover Lite on the bottom, with Dulux quick dry aerosol paint. As well as being the easiest Covering I have used the OzCover range, as the name implies is made locally in Australia. Support local industry.
Be sure to apply a finish that will allow easy orientation of model. Make underneath dark, and top bright with a directional colour scheme.
As you apply your iron on film to the model, note that the vertical stabilisers can only be added once that the Covering has been attached to the rear portion of R3. Be sure to add the Vertical stabs whilst there is still sufficient bare balsa to bond with.
To install control surfaces, I use and recommend the furry type CA hinges such as SIG Easy Hinges or Great Planes CA hinges.
Coat inside engine and tank bay with a good fuel proof coating. I use 5 min. Epoxy thinned with 1/3 part methylated spirits.
Radio setup is optional. Basic 4 channel set up is shown on plan. Other possibilities are to use Computer mixing for Rudderators (V Tail Mixing).
RX Antenna Lead will be required to exit through rear former, using a full length of yellow Nyrod for protection. Do not exit antenna through wing tips. Mount up all equipment and test position of CG, both fore/aft and laterally.
I turned up at the field with the prototype Ninja Star and there was only one other foolhardy enough to brave the cold conditions. The breeze suits me fine to test fly a new model as long as it is straight up and down the strip.
The Bush Telegraph must have been humming because within 20 minutes of me unloading this new "contraption" half a dozen more arrived. My self appointed volunteer said, "It will never fly, but I will humour you by helping".
Well it was too windy to try taxi tests so I just stood behind the model and applied full throttle, and away the star went. It accelerated like a pylon model, rotated in about 50 feet and then straight up like a bullet. Well, so far it had exceeded my expectations.
Ninja Star looks totally weird in the air. Orientation takes some concentration. If you can imagine a 5 pointed star flying across the sky, this is it! Even with a directional colour scheme applied it is difficult to tell which is the front, side, back or wing!! I suggest until you are accustomed to flying this shape that a 6 metre crepe streamer is attached to the tail to aid orientation.
The model is VERY stable and flies like its on RAILS. No vices in the air in fact I have flown trainers that don't fly this well. As you would expect it is no pattern ship, but rolls are quite axial & loops are large but precise. Inverted flight is possible, albeit unstable, with about half down elevator being required to hold level inverted flight. It does not tip stall as one would expect, with 5 tips to choose from it canŐt decide. It just settles down to land with a gentle flare like a typical sports model.
One manoeuvre I am not in a hurry to try is a Flat Spin. I can imagine the name "Ninja Star" does not need to be tested to that degree! As explained previously I have cartwheeled the model and the only damage was the wing tips breaking away, proving great structural integrity in the design. Anyone that studied geometry knows a triangle is the strongest structure and the star is full of them!
Oh, and one other thing, before you fly be sure to confirm your ailerons move in the correct direction....or else!
SPECIFICATIONS Ninja Star
Type: R/C Novelty - Sport Model
Ninja Star plans are available from:
Plan No. 653
This page was last modified on the 21-May-02