CHRISTCHURCH AND DISTRICT MODEL FLYING CLUB

Dewoitine D520.

We all admired Clive’s model of the D520 at the AGM. Here’s the story.

I had not heard of this aeroplane until Neil Longman donated a kit to me, which sat on the shelf in my model room for a year. I decided to find out more about it, & thought it was Italian, but it turned out to be a French WW2 fighter. That was a revelation in itself. I found drawings, articles & photos in the usual place. What did we do before the Internet? I used the kit as a fill in when I wasn’t repairing one of the existing fleet, so progress was pretty slow, the basic structure taking some two years.

On perusing the kit against the photos & drawings it became obvious that it was far from scale. Remembering Dave’s Spitfire, I decided to bring the model to a more scale appearance & to add an U/C. I also wanted to convert it to electric power. The kit was mainly blue foam, not the lightest material in the world.

I started on the wing by adding aileron servos with hidden linkage in lieu of one central servo. The undercarriage proved problematic as the wing is quite thin in this area so I had to hunt about for some small mechanical retracts which would be strong enough to take the weight of the model. I finally found some excellent ones in Channel 4 at a very reasonable price. Fixing the retract servo presented a real problem as it stuck out of the bottom of the wing, but luckily this plane has a large central under wing fairing and I used this to hide the servo. The model is equipped with a substantial spar used for the original fixed u/c location. I used this & the leading edge spar for locating the retract blocks. What covering to use? Balsa sheet or epoxy resin? Both too heavy & Heat shrink film melted the foam, so I settled on tissue & white glue thinned 50%.

Having finished wing I started fuz only to realise that the supplied plastic cowling was hopelessly out of scale, necessitating the addition of a new nose structure complete. The wing fairings were also missing so I made some from the blue foam off-cuts. As this is intended to be an electric model I made up a GRP battery holder & added a rudder, which was not part of the original kit. I hid the elevator horn inside the fuz & covered the whole model with tissue & white glue thinned 50%. This took a considerable time, but resulted in quite a good finish for painting. Small dinks where filled with lightweight water based filler & primed. I framed up the canopy, added the slider rails & cut the canopy to size. The cowling details were added & the whole airframe primed all over using acrylic car spray.

My first attempt at painting the camouflage was a complete disaster. I used an acrylic spray can to add the matt green, but the paint ran under the masking & I ended up with a total mess on my hands. I had to sand the whole lot down again & reprime the structure. Luckily I had only done the fuz first. About the same time I saw an article on painting camouflage using an airbrush technique so decided to go down this route. The making up of an airbrush rig & compressor is a completely different story for which I will write a separate article some time. Needless to say I required some help, never having done anything like this before. As usual there is always someone in the club who is willing to give help & advice; in this case Ken Spokes offered his assistance. I finally managed to paint the model using thinned acrylic paints. The pilot was hollowed out to save weight & an instrument panel fitted. The canopy & rear glazing panels were glued on with a tiny amount of epoxy. I decided to go brushless for the firs time on this one so I raided the piggy bank & purchased an AXI 2820-10 motor & controller.

Having completed the model it was time to find out if it would fly? I asked Trevor Hewson to do the initial test flight as I was not confident I could fly it, due to a pretty high wing loading. On doing the pre flight checks we found that the rudder had more travel on one side than the other which we had to adjust out on the radio, also the ailerons did not centre very well. We improved the aileron centring with a little oil on the hinges but they still were not very good. Trevor decided that they were good enough to fly. We inserted a new fully charged eight cell pack, and having run out of excuses, committed her to the air.

On take off it was evident that there was plenty of power from the brushless set up but the ailerons were making control difficult. After a couple of circuits with the undercarriage left down, Trevor set up for a landing. On touching down, the wheels, that are held on to the axles by grub screws, managed to twist through ninety degrees which had the effect of stopping the model dead. The battery ejected out of the hatch as it was meant to do but managed to remove the front bulkhead on the way out, other than that there was no other damage.

I replaced the bulkhead, which took all of five minutes, this being the only damage. The rudder problem appeared to cure itself after some use, so a sticky centring through lack of use seemed to be the problem. I ground flats onto the u/c legs to stop the wheels turning corners on touch down. The aileron centring was a real problem; however I tried to cure this they would not centre consistently. Having thought the problem through, I decided that the hidden linkage with its very short travels was to blame. I decided to change this for a more conventional set up & having modified the linkage the problem disappeared. All that remains now is to fly here again & see if all the effort was worth it, but this is a story for another time.

Clive Spencer

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