Some of the sweetest model aeroplanes I have ever seen in my life have been indoor free-flight scale models. There is something intensely appealing about their cute size, their accurate but tiny proportions and, most of all, their cleverly judged level of detail.
I think the latter is what marks out a truly great F/F scale model from a merely excellent one. The builder’s artistry comes from knowing exactly which features should be prominent, which should be present but understated, and which should be left out altogether. It is this keen attention to scale perspective which builds up the illusion of miniature reality.
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Modern Materials
Light balsa construction, covered with tissue and dope, remains the staple of indoor scale models, although carbon tows for local strengthening and a certain amount of foam detailing are also popular. Some indoor experts, like John Valiant, have perfected stunning all-foam models, which have that comfortingly solid appearance of the real thing but weigh very little. John takes blue insulation foam – an unlikely medium when you think about it – and really makes it come alive. Look at his panel detailing and weathering, and then remember the tiny scale to which he is building. With not an airbrush to his name, he achieves a stunning finish with nowt more than his wits and a paint brush.
The Art of Indoor Trimming
When you think about it, spending hundreds of hours on tiny, fragile, wonderfully detailed models and then just winding them up and letting them go into the hands of Fate – or an intervening breeze block – is pure masochism. Not for nothing are these lads dubbed ‘The Hard Men of Scale’.
But, on closer inspection, there is method in their madness. Indoor F/F scale requires an advanced understanding of the art of trimming. After all, you will be launching your creation within four, hard, unyielding walls. Not to mention, in most flying halls, a surprisingly treacherous and cluttered ceiling.
Ideally, your model will fly tight enough circles to safely miss the walls. However, you also desire open enough circuits to fly without too much bank, and therefore display optimally under the searching gaze of ‘The Judges’. With prop driven rubber models this will require a thorough knowledge of torque transmission, which varies throughout the flight. On top of that, knowing just how much to tweak incidences, elevator and rudder will all have taken their part. It is a Blacke Arte and I have often overheard two top notch pilots completely disagreeing on which corrections to apply!
Then there are the electric classes, which these days, as a minimum, benefit from electronic flight controllers to meter the speed and duration of the prop run. Now, you would think that this technology would produce textbook flights, one after the other. Don’t you believe it! There is still much to tweak and perfect.
Finally, we have the doughty CO2 Brigade, who have even more variables to think about, including fill regimes, gas/liquid mixes, and even hall temperature.
All in all, if you adore seeing mixed propulsion systems in action, a day at the BMFA F/F Scale Indoor Nats is about as varied as one could desire.
Peanuts
Peanut scale is one of the most popular classes of indoor scale, mainly because the models are a handy and practical size, and the rules are sensible and easy to understand.
A Peanut size model is defined as having either a maximum wingspan of 13” inches or a maximum fuselage length of 9” inches. These sizes are recognised by the Federation International Aeronautique (FIA), which is the international governing body of model aeroplane competition.
To refresh your memory, here are the original US 1969 Peanut Scale Rules, but just note these were amended slightly for contests and the BMFA in the UK uses modified rules, which I will show below:
• Models must be built-up reproductions of actual man-carrying aircraft.
• The maximum permitted wingspan is 13 in.
• The minimum permitted wingspan is 10 in.
• Motive power must be furnished by rubber band(s).
• Models will be hand launched.
• Timing will commence upon release and will stop when the model lands.
• Any flight of six seconds or more will be counted as an ‘official’.
• Three official flights are allowed, and the total will be the contestant’s score.
The BMFA’s take on Peanut Rules is described by Lord of Indoor Scale, Mike Stuart, in the following way:
“This class is open to rubber powered scale models with a wingspan of maximum 13” or fuselage of not more than 9” (excluding propeller). Unlike the Open classes the flight score is based on duration and not realism. A successful take-off from the ground adds 10 seconds to the recorded flight score. You are allowed to make up to nine official flights, with the best two counting towards the flight score total.
For scale judging the minimum documentation required is either a three-view of minimum 2″ wingspan, plus a photo or printed reproduction of the subject aircraft, with proof of colour if you only have a black and white photo, or alternatively a coloured three-view of the subject aircraft to a minimum of 1:144 scale. Profile Publications are a useful source for these illustrations.
The Peanut scale class is one where you really have to balance the aim of building the most realistic model possible against obtaining a reasonable flight duration. Extra static marks can obtained for a painted finish, complex markings, scale rib spacing, separate control surfaces etc. but these will generally increase model weight, hence reduce flight performance. It is worth noting that there is a nine point scale bonus for a low winged model or biplane – a significant amount considering that 100 points is a decent scale score. Unlike in the Open classes, final placings are not calculated by simply adding static and flight scores together. Instead, static scores and flying scores are ranked separately, with the best placed models getting one point, second two points etc. Competitors’ scores for flying and static are then added together, with the lowest total placing first, second lowest total second and so on.”
Stop Press: These Peanut rules are currently under review by the BMFA. Check out scale.bmfa.org/heads-up-on-revisions-to-2020-peanut-rules on the BMFA website.
Pistachio
This is the smaller scale class to Peanut and has its own keen band of followers. On the BMFA website, Mike Stuart tells us that this class is broadly similar to Peanut scale, but with a maximum wingspan of just 8” or a maximum fuselage length of 6”, excluding prop. Flight scoring is the same, but there is no 10 second bonus for a take-off.
Documentation for scale judging is the same as Peanut scale. Scale judging is along the same lines as Peanut but somewhat simplified. Again, there is a bonus for biplanes and low wing types.
One interesting aspect is that in Pistachio scale there is no penalty for using wings covered on the upper surface only; wings like this can work very efficiently at this small size.
Kit Scale
The growth of this class, dedicated to commercial kits of yesteryear, has been the big hit of recent years. It is easy to see why: nostalgia, ease of build, compact size and the general attractiveness of commercial model products all conspire to make this a runaway success. The Judging and Comps have been cleverly tuned by the BMFA Tech Committee to attract the widest entry, and it has worked. Here are the BMFA’s main rules:
“Maximum weight is 200 grams, maximum wing loading 15 g/sq.dm, and power can be rubber, electric or CO2. The Kit Scale class differs from the Open classes chiefly in that scale documentation requirements are much more relaxed, and more emphasis given to how the model flies. The event is open to any scale design that has been available as a model kit, though you don’t have to build the model from a kit – you can use a kit plan and your own wood.
Static judging is against the kit plan, which has to be produced as documentation. Significant deviations from the plan are penalised. Some evidence should be supplied to support the chosen colour scheme; this can be a photo, drawing or painting (e.g., box art from the kit). To encourage models with a coloured tissue finish, a painted model will incur a penalty.
Flights are judged on realism, similar to the open classes, but equal marks are applied to each phase of the flight. A 10 second flight must be made to qualify. The best two flights out of four count towards the final score, meaning the flying scores make up approximately 2/3 of the total marks”.
Again, pretty transparent and encouraging rules for any prospective locked down winter builder!
I have to say that I have a soft spot for Kit Scale models. Walking the hall at the BMFA Indoor Nats and admiring the long tables full of such models is always one of the highlights of my own modelling year. Also, note that CNC-cutting and kitting companies, like Belair, are now bringing out many more old favourites, so the gene pool is growing.
