HK Spitfire Build Notes

There are some build photos and an RCGroups Thread.

Not completed but OK for first flight 24 October 2008 at Yarra Glen

Initial Notes 21 October 2008

For those that come including some hints from the Thread:

Read the Thread - It is well worth reading through the Thread which is very active.
Cutting Film - The Thread debates the merit of trimming film from the various joints. I chose to cut the film away carefully for the horizontal and and vertical stabilisers. I used white wood glue.
Flight Surface Alignment - Set the aircraft on blocks on a flat table as shown in the photos and then fit the vertical stabiliser last. Use normal symetry measurements.
Rear Wing Mounting Bolt - Do not rely on this being accurately placed as mine was out by 3-4 mm. I will probably fit locating blocks on the rear of the wing.
Elevator Strengthening - I added a 1/16" wire stiffener (torque rod stock) to the joiner between the elevator halves.
Rudder Notch - The notch in the rudder allowing it to clear the alevator joiner bar is not deep enough to allow full rudder swing and needs to be enlarged.
CA Hinges - Use a crayon to mark top and botom hing lines to prevent the CA stiffening the hinge (thanks Roger).
Retracts - I chose to fit the retracts which may have been a mistake.
Wing Servo Wiring - Run the wing servo leads BEFORE fitting the wheel well liners. I did not.
Wheel Well Liners - The liners are VERY brittle and crack easily. They are also too deep so that the lip sits proud of the wing surface. I would build my own liners next time out of balsa and thin ply as others seem to have done. CA although recommended by the Manual does not hold the liners down as neatly as the aircraft deserves and just loves to run all over the wing film! Flash CA seems OK with the covering film but cooks it if accelerator is used.
Retract Servo Box - The thin balsa top wing-surface is not supported on the outer edges of the box and can collapse easily.
Nose Over - The undercarriage wheels need to be be further ahead of the CG when down which can be achieved by packing the rear of the undercarriage mounts by about 1/8" as pointed out on the Thread.
CG - The Manual shows 90mm behind the LE but should be around 75-78mm.
Elevator Deflection - Max 6mm deflection is suggested for the elevator otherwise it is too frisky and probably close to unflyable with the incorrect 90mm CG.
Motor Box - The current version of the aircraft seems to have a stronger motor box but I added lollypop sticks just in case. The motor will be a Turnigy TR 35-42B with a 10x6 Aeronaut folder on a 3S LiPo. Performance should be adequate.

First Flight 23 October

First flight today.

Grass was too long to do an ROG (disappointing) so a colleague hand launched for me. About 2-3mm of Aileron mixed to Throttle to correct for torque with no manual roll correction required on launch. No issues at all really except for the known pitch up which I will cure with a combination of packing on the motor and a little elevator mixed with throttle. No motor vibration at all.

A pussycat to fly with no suggestion of tip stall or other nasties. Decalage may be a little large as a reasonable amount of elevator was required even on fast glide passes out of a shallow dive.

Holds altitude happily at about 30% throttle, less than predicted, and glides forever with folder prop. I have spoilerons but did not use them for this first flight and so landed long. Comments by club members were "It's really quiet" when on low passes with motor off! The Club is currently predominantly fuel powered aircraft.

Battery consumption also seems to be roughly as predicted with 2x2000mAH packs hard up against the firewall to get to the CG at 75mm. Elevator right on neutral for trimmed glide.

Fuse film got pretty wrinkled and that's just our Spring Sun.

All up weight is 1.36Kg.

Excellent.

Finishing Touches 28 October 2008

Correct propellor hub arrived and fitted. Initially packed motor out with washers to get a little down thrust but hub looked ugly against motor cover so used Throttle mixed to Elevator. Also fitted screw top lids on under side of wing for easier hand-launches.

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