Thread: Cool Let's see the S.P.A.Ds
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Old Jun 29, 2012, 07:53 AM
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South Africa, GP, Johannesburg
Joined May 2012
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SPAD park fly trainer

About a year ago I started flying RC after about a 25 year absence, primarily under duress from my young nephews, one of whom had spent his hard earned savings on a flashy foam plane that was anything but easy to fly. I was immediately attracted to the SPAD concept – tough but cheap and simple to build and repair. However, I wanted to keep to the park fly category, both for its convenience and accessibility for youngsters. However, SPADS generally suited .25 and up size motors – the only really proven park fly design I could find was the Mugi, and that’s a bit of a handful for a 12 year old.

Consequently, I had them build and do their initial flying on foam Nutballs, but kept the aspiration to develop parkfly SPAD trainer, with the following characteristics:
1) As near to indestructible as possible, and field repairable with epoxy and duct tape, even after a major mishap. Electronic components (esp motor) must be protected in a crash.
2) Built from non-specialist materials, where possible available from the local hardware store.
3) Very cheap, quick and simple to build – lets face it, the modern youth’s attention span seldom matches the time required to construct a conventional balsa and film plane!
4) Extremely simple and quick to repair/ rebuild.
5) Flight characteristics similar to, or better than the 1/2A trainers of my youth.

I started with a common 1/2 A basic trainer from my youth – the Airtronics Q-Tee, but converted it to a pusher design (hence the name “P-Tee”). It’s taken quite a bit of experimentation, but prototype number 3, built this week, seems to have resolved the overweight and thrust angle issues that prevented the first two versions having the flight characteristics of a true trainer. Using a standard Q-Tee wing, version 3 now weighs only 10-30g more than my conventional Q-Tee (depending on LiPo and motor choice; version 2 was about 150g heavier) and its flying characteristics are so similar that it’s hard to distinguish between the two. If anything the P-Tee feels slightly more ‘solid’. Stalls are benign and spin recovery is instantaneous. Flight testing this week has settled the motor choice – a 2200Kv Suppo 2212/06 swinging a 6” prop enabled the thrust line to be lowered to below the wing, which has totally eliminated the pitching moment on throttle changes that plagued the first prototype. The Suppo provides way more power than needed (read near vertical climb on ¾ throttle), but as it’s the only high KV motor I have, it will have to do. The E-Max 2812 works, but its best matched with a 7” prop....which raises the thrust line.

In addition, I have done one test flight with a correx wing – but given that a correx wing is at least 50% heavier than a balsa one, I extended the wing by about 25% to compensate. Flight remains docile, but AUW increased by ~100g,so the plane now does need the extra power of the Suppo to haul the excess weight!

Apart from an extended nose, all dimensions are identical to the Q-Tee. Fuselage consists of a 20mm aluminium U section ‘spine’, 2mm ply formers, a 2mm correx skin and a foam nose. The tail feathers are 3mm foam board that are simply taped onto the fuselage (more than strong enough for flight and will hopefully ‘unstick’ if the plane should cartwheel on landing). Wing is a light correx design – the underside behind the spar is kept open.
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Last edited by Extreme Sports; Jun 29, 2012 at 09:58 AM.
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