About this Plan
Extra-Vert (Extravert). Radio control sport aerobatic model. For ST X25 power.
Quote: "Smitten by the 'Extra 230' look, Gavin Selwood designed this 48 in span lookalike with spectacular results.
A couple of years ago, like most modellers, had a thing about the Extra 230. I also had a desire to design and build an aerobatic model of my own. The basic requirements were that it had to vaguely resemble an Extra 230, be relatively quick and easy to build (no compound curves etc), reasonably light wing loading and, because I'm a reasonably lazy modeller, had to fit into the car without removing the wing.
With these concepts in mind, I set about what was my very first own design project and was quite pleased with the end result. It looked good on paper but as always with own designs, there is always that nagging doubt, would it fly? So with plenty of encouragement from fellow club members, construction commenced.
About three months later, the model was completed and test flown at RAF Benson. It was a complete anti-climax, complete with all the old modelling cliches - flew straight off the board, very groovy, etc, and she would go exactly where I wanted it to go and do exactly what I wanted it to do. After getting used to the model, I managed to perfect what I call the 'Richard Goode' take off. Line her up, full throttle keeping her straight, unstick and keep straight and level fora few seconds, then lift the nose up and roll full inverted. Complete the circuit in the inverted. No vices. Perfect!
I did build a foam wing version for an OS.48 Surpass four stroke and deliberately 'beefed it up' to make it heavier just to see what I could get away with. She flew OK with power on but landings were a fast, wheels on affair. However, don't let this put you off. I'm sure that a foam wing version could be built reasonably light.
The whole exercise was worthwhile and the flight characteristics surpassed my expectations - so much so that I flew it consistently for a whole year and literally 'flew it to death'. The cause was fuel creep under the Solarfilm, just behind the wing mount. Whilst showing off to a new crowd one morning, a low inverted roll resulted in a cartwheel and the model snapped in half completely. The post mortem revealed fuel soaked balsa and ply doublers - my own fault on both counts!
Various scale projects have kept me from building another Extra-Vert, but I do intend to scale it up for the Quadra 40 or a 1.20 four stroke. As a postscript, a few years ago, I was flying next to an unknown modeller who happened to be flying a scale Extra. He started making enquiries about the model and so we decided to swop transmitters during the 'slot'. He made some very flattering remarks about the flying characteristics. Shortly after that, the model went 'deadstick' and he quite happily landed it with no problem.
General Construction Guide: Before commencing construction, study the plan carefully. As much information as possible has been included in the plan. Also observe grain direction and careful grading of wood will enable the model to be built well within the target weight.
Stage One: Trace all farmers and wing ribs, then cut out as many parts as possible to make a 'kit' of parts.
Stage Two: Fuselage Construction. Cut out the basic sheet sides from 1/8 medium to soft balsa, the 0.8mm ply doublers and soft balsa wing seat. Fix the 0.8mm doublers to the fuselage side with Copydex - the 1/8 in balsa wing seat can be glued in the same way. Remember to make a left and right-hand side.
Mark all former positions in the inside of the fuselage and glue formers 1, 2 and 3 into position. Leave to set. When dry, add formers 4 and 5 and the 3/8 stern post. Draw the tail ends together at the stern post, ensuring that everything is true. You may need to facilitate bending by lightly cutting the fuselage sides just behind F3..."
Extravert, R/C Model World, September 1993.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
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