First printed in the SAA magazine "Airtime", Autumn issue, 2002
When I started aerobatic flying in the early eighties,
a full-blown competition model wasn't very different from a 0.40 powered
low wing sports model. My first real aerobat was
built from a Dave Smith semi kit and powered
by a WebraSpeed
40. All the accessories to finish it were bought from Dunn's Models
including the ED tuned pipe. The next one Was a Gangster 60 and apart from the engine, an old OPS60
which my dad had bought for a boat. It too was completed totally with
bits bought in the local model shop. At the time, the top flyer was
Steve Burgess with his Challenger. This model was conceived after Steve
came back from the World Champs in Pensecola
It is instructive to compare my model with the model that arguably was the best model of its day. The Gangster looked primitive with its fixed undercarriage and flat plate tail surfaces but the similarities were there in that they both had built up wooden fuselages, veneered foam wings and side mounted exposed engines. Steve's model had also been completed from the local model shop although with a paint rather than film finish. The Challenger was powered by an easily obtained Supertigre S61 tWo stroke coupled to an ED tuned pipe by a home made manifold. My Gangster was fitted with an OPS rear exhaust, rear induction motor and an OPS tuned pipe. As I mentioned my dad had bought it watercooled for a boat but he donated it to me and I bought a new aircooled head for it. The marine racing carb wouldn't throttle and John Walter gave me an old ED carb from a redundant motor that worked reasonably well. The radio equipment in these two models was also similar. Steve used Sanwa radio with a mixture of Sanwa and JR servos, mostly ballraced and coreless. I had a JR pre-computer set with standard servos which were more than good enough for my ability but could have been up-rated for a few pounds. Fuel being burnt at that time contained anywhere between 0-10% nitro and again was bought in the local model shop. The point is that the jump in money and manufacturing effort between my intro model and the top model of the day was not all that large.
Compare this to the situation today. Most sports models still have wooden fuselages and foam wings although a significant proportion will have been taken out of a box ready to fly. Not long ago these would have been mail order purchases but they now form the majority of stock in most model shops. Most of them will be powered with two strokes and may or may not have computer radios but the availability of cheap aftermarket servos will make guessing the make difficult. The whole package could easily cost less than £300 excluding the transmitter.
To resist the high nitro fuel the engine will be burning, the fuselage will be sprayed with two pack automotive finish containing large amounts of isocyanates.
The flying surfaces will be film covered but might be one of the polyester derivatives that cost three times the usual stuff. The Russian version will have been painted in its moulds and pops out ready to go. The engine will be a YS 140 four stroke (although a few people are using even larger two strokes) mounted on a flexible mount and connected to a silencer possibly made from carbon fibre by a flexible manifold and coupler. It will be fitted with an alloy spinner with the backplate milled out to save a few grams and the prop will be a special size.
The current trend in landing gear is away from retracts but
if they are used they will be either top quality mechanical units or
electric units produced in
Apart from the covering film and that is by no means certain, NOT ONE ITEM COULD BE BOUGHT IN THE AVERAGE MODEL SHOP AND WOULD NEED TO COME FROM A SPECIALIST SUPPLIER. The cost would be around £2,500 for the airborne bits if you built it yourself and you could nearly double that if you bought a fully moulded, a.r.t.f. version. If you add the fact that to operate this model would require 30% nitromethane fuel is it surprising that the numbers at competitions are dwindling?
Now money is not the only issue. If you take into account that these models normally last a long time and are often sold on, the overall costs can be surprisingly reasonable but making the initial commitment usually means you aren't going to do much other modelling for a while. In addition once you have acquired your new toy, the aerobatic schedules flown at the highest level require determination to learn and constant practice to keep the skill.
Standard, the entry level class, still represents a high level of skill to fly perfectly but I guarantee anybody who is competent with a low wing sports model can tackle it. Have a look at the standard schedule. Just as important as the skill required, the schedule can be flown very adequately without the unlimited vertical performance of the F3A models and so a basic low wing sports model correctly set up and trimmed is all that is required. Obviously as ones skills improve the machinery can be improved too. When I used to write this column regularly I tried to set down various recipes for aerobatic models and motors that would work to try to give people a guaranteed setup that would work. I am going to go one better, here is the recipe for a Standard class model which is so simple you could almost say it is a "Takeaway"!
Obtain ANY low wing sports aerobatic model. Fit the largest size of two or four stroke motor recommended but add a couple of cc's. Fit an APC propeller of the correct size (if you don't know what this is ask me at one of the contact points below. Install any radio and servo combination as long as it has exponential function available on the primary channels. That's all there is to it.
Over the next couple of articles I will cover the basic trimming to make such a model easy to fly through the schedule but if you can't wait for that email or phone me with your trimming questions or better still come to one of the SAA comps and we will sort you out. Please remember that even the best flyers started off as beginners and everyone who takes a crack at aerobatics improves both their flying skills and also their field discipline, which can't be bad.
Above all when you crack that first really good 4 point roll the satisfaction is fantastic!