Cricri aerobatic aircraft and other complex projects Page
Details of fuselage fitout:
SS wire control lines cut and crimped (double crimps) to fit. Much attention to the pulley’s for steering connections, with several adjustments to fit without contact with fuel tank. Front Air scoup redone to hide screws for access removal of the panel. Fuel cocks fitted, with flop tubes. Rubber ‘u’ tube over lower flange to minimise the chance of abrasion to front of tank. Instrument panel moved rearward to clear Dynon, which was set too high for panel in standard position.
Celeron (phenolic laminate) nose leg bush was drilled accurately, but a few passes with the round file left it slightly loose. Built up with epoxy, rear surface only (ie non weight bearing) to give a firm fit.
Moved instrument panel rearwards by 18mm (cf plans) to find the ideal pivot point to let pivot system work with adequate clearance all around. I redid the instrument panel, version two to improve instrument layout and clearance. Canopy hoops were fabricated in fibreglass and with threaded inserts for 4mm attaching screws.
1.Vacuum molded instrument panel (2nd version).
2. Fuel pumps mounted on brackets attached to engine pylons.(later abandonded as too heavy)
3.Rubber wedges to support fuel tank 6mm forward.
4. Strobe and headphone jack mounting bracket behind seat.(later relocated to beside seat for better access when mounting cockpit with headset already on)
5. Fuel tank lateral threaded brackets with spacer. Note “S” to accommodate alignment
6. Castle nuts and split pins for all engine mount fasteners
Initial fuselage fit-out
All over summer I worked away at fitting out the forward fuselage, having borrowed a crimping tool from Murray Smith for the wire control connections. These were straightforward, except the plans advice to form a small kink in the spare segment only served to twist the wire and I abandoned this. The wire end is a bit short (5 mm) at the rudder end..
Pulley wheels fitted but several removal and adjustments with remake of the holder brackets at least once to get a fit around the fuel tank—which itself did not quite fit in the recess if it was to clear the elevator control pivot arm. I moved the fuel tank about 6mm forward from its natural position by sitting it on rubber wedges.
Fabrication of Fiberglass instrument panel
Second attempt worked, keeping the Dynon low to clear the cowling when hinging forward. Air speed indicator provided by Graham Allen, with correct flight speed marking already. The vacuum moulding keeps the curing cloth tightly against the tight bend of the female mold.
Several attempts before finally settling on 0.8mm braided ss wire running in 6mm nylon tube. The tension in the circiut is reasonably low and is sustained by a spring in the "pull to close" side of the circuit at the carburetor end. With the throttle friction screw backed off the throttles are feature light and synchronous. Its one of my best innovations on the project.
Wiring and Finishing out fuselage
Appropriate gauge Tefzel wire run thru split automotive conduit thru front section fuselage
Brass fuel cocks with limiters for open and closed, Battery 1 of 2 i, in series, shifted to rear of seat for weight and balance later on. The two grey boxes hous the regulator for the 6volt ignition modules.
Optional transponder wiring coiled in case of need for a transponder later.
The batteries started in the location here, but ended up behind the seat as the aircraft was nose heavy when weighed.
Fuselage fitting out … cont
A miriad of smallish tasks undertaken and completed. Ribs for engine mount tubes milled out of 10mm 2025 aluminium, drilled and tapped as per plans. Elevator stops adjusted extensively to give the -11degress +6 degrees shown on the plans. This was a stretch to achieve, then I find the written description only requires -9 and +4 degrees, as long as the setting at +0.5 has the stick at 5 degrees forward of vertical.
Turtledeck cut out and fitted to its angle bracket, after selecting a nice PPG 2 pot white for the aircraft, painting the skin inside the turtledeck (and also inside the undercarriage covers) prior to fitting these items. The paint is OK but I will have a professional do the main paint finish.
3 weeks laying Tefzel wire of appropriate gauge to every required destination—plugs for Dynon 10A and Transceiver. Bus for circuit breakers and 2 amp fuses for CDI systems. Most wires routed without ties in light split automotive conduit. Ultimatly the far ends were cut to length prior to organising the wires in bundles and securing against vibration damage.
CDI 2 amp Fuses
These were added to C3 frame later after the desirability of fuses for every line became evident. Blade fuses of 2A for each CDI circuit.
See Wiring diagram for details. 7 circuit breakers installed on frame 3.
An initial fault with radio plug corrected with some advice from XCOM.
Labeled circuit breakers and 4 x 2amp blade fuses fitted. All circuits except the alternator circuit are fused - one way or another. In rertrospect the circuit breakers add unnecessary weight and knowing the finished weight now, I wouldn't have used them. Blade fuses all round would have been fine. You rarely achieve anything useful by resetting blown fuses in flight.
Fitting Canopy Hoops and Turtledeck Frames
Previously fabricated Klegecell hoops with fibreglass epoxy outer layer were primed and painted in Delfleet white. Secured to rear polycarbonate turtledeck and front panel cover was by drilled a recess for threaded aluminium tube (made on lathe 10 x 6 mm with thread 3mm front, 4mm rear) The tube was set into hoop and epoxied in place, providing a secure anchor for the hoop.
Canopy frame tubes bent of wooden wheel system described earlier to fit on plans, Fiddly, but not much trouble achieving the major bends. The 45 degree angles carefully cut and filed to snug fit, then appropriate angle cut from 4mm ali with 30mm legs was epoxied into the butted tube ends to provide rigidity at the junctions ( and for later canopy screws) With the epoxy cured the angle flanges were riveted in placed as per plans.
Canopy latches fitted, with nutplates secured. Slots filed to correct slight inaccuracy in fitting
Canopy & its Frame and Turtledeck
Turtledeck polycarbonate (1mm) cut out and fitted to its angle brackets. After selecting a nice PPG 2 pot white for the aircraft, painting the skin inside the turtledeck (and also inside the undercarriage covers) prior to fitting these items. The paint standard is OK for inside parts, but I will have a professional do the main paint finish.
(In fact I left most of the aircraftas polished Ali, and did all the paintwork myself - weight and pride - a powerful mix!)
Elevator and rudder deflection angle setting .
Elevator stops adjusted extensively to give the -11degress +6 degrees shown on the plans. This was a stretch to achieve, then I find the written description only requires -9 and +4 degrees, as long as the setting at +0.5 has the stick at 5 degrees forward of vertical.
Epoxy added to limit stops to reduce through. Clamps on the reducing bar were move out by 10 mm to give rudder through of 20 degrees each direction. Full and free movements without play or friction.
Completed earlier, these had been alodined by Paul Muller. Slots enlarged to give a good accurate fit..
Rudder reducing bar clamps moved 12 mm laterally to give 20 degrees of rudder deflection
Nosecone and Front deck hatch
Not much in common but both items done. Farings added to nosecone using klegecell and glass cloth to blend engine mount winglets into the nosecone.
Also, I decided to cut a hatch in upper fuselage skin, keeping an emphasis on ease of servicing this aircraft. On advice (as the skin is stressed) have employed nutplates and 0.8mm sheet for the hatch cover. Doesn’t look great, but how else do you replace batteries, re-tension rudder bungees etc.
Front fuselage hatch:
Bits and pieces done—something different every day. I decided to create a large hatch in the front fuselage upper surface as there are so many maintenance items in this front section—bungees, battery, access to circuit breakers, wiring and fuel hoses. Neville Hay said lack of access was one on his most troubling features. The lower air scoop hatch is partly covered by the rudder tray and doesn’t give much access anyway.
Undercarriage mount brackets:
Mat Connor finally finished machining the complex U/C clamp brackets. I tapped and threaded for AN bolts and have lightly sanded the carbon fibre undercarriage to firm fit in the clamps. My custom made rubber bushes (from urethane liquid) are rather stiff—but may loosen up.
Lateral motion limit bolt hole drilled through the undercarriage. Brackets all mounted to the fuselage after priming the lateral fuse sides and white paint to the undercarriage parts and covered bit of fuselage undersurface.
Wheel axles and boss for brake rotor:
The axles were fitted earlier to the undercarriage with 4 securing bolts and a large 4mm Ali plate to hold the brake caliper. This plate is yet to be adjusted and lightened.
Boss for the brake rotor turned from stock free machining ali, extending 32mm from hub bolt lugs, which it picks up on. The fuselage side of the boss holds a third bearing to carry the torque of the rotor on the axle. The rotor is secured to the boss via a 3mm steel plate machined (by Connett Engineering) with a centre rose pattern duplicating the standard Shimano rotor centre, and this takes the driving (ie braking) forces. Probably overkill and could have been OK just using rotor mounting screws!
Probably spend a month of spare time doing the wheel pants. First, used a mold from Nev Hay that needed extensive modification—for each half of pants. Learned how to gelcoat and take a male cast of the female mold. 6 castings made. Another few weeks trimming, bonding and fitting the the wheel legs, with securing brackets and nutplates to secure. The pictures show it all. (to be added later when I have time!)
Using a unknow brand 2 pot paint system (just because they where happy to colour match small quantities and sell 250ml tins of hardener) the painting consumed a few weeks of masking and preparation. You can tell its an amateur job - but will look passable with some fine sanding and polish. To my eye the two tones of blue go well with the polished aluminium (approved by my wife who has perfect colour senses!)