We’ve been trying to run competitions for both rubber kit scale and larger rubber scale models together for a few years and to be honest it’s always felt as though we were trying to force a square peg into a round hole – it didn’t really work.

However, it has recently come to the attention of the Events sub-committee that:

1. Several larger free-flight rubber scale models are likely to be under construction over the winter, and
2. Many regular competitors like seeing larger rubber scale models in the air or would like to have a go at building one.

So to take advantage of this set of events (Carpe Diem and all that) we’ve come up with a set of rules for larger rubber scale models.

The existing Kit Scale rules have been simplified and converted to a Winter Postal, with one Kit Scale competition on Port Meadow during Spring 2025; the rest of the rubber scale competitions will be to the new rules.

Dumas DHC Beaver 

Why the Rules Look the Way They Do

The fact of the matter is that there are now so few of us that we should really be trying to be as inclusive as possible and encouraging people to try something that they wouldn’t necessarily fly – in this case, we’d like to encourage people who normally fly duration-based sport or competition models to try something that looks scale and is relatively quick to build, with a traditional structure and a tissued finish whilst capturing the essence of the subject without carrying loads of detail.

We also didn’t want to insist that people should generally have to produce documentation, so we borrowed the phrase from the UK kit scale rules which specifies that “The colour scheme is to be in keeping with the subject aircraft but need not represent a specific full-size aeroplane” – as long as people have made some sort of an effort, we should give them credit for it.

However, all entries are subject to a Go/No Go decision by the CD to weed out duration models masquerading as scale models.

Competition Format

We thought carefully about the general format of the competition; a duration competition is the norm for free-flight and the classic way of doing it is to have three flights to a set maximum time, if more than one person gets three maxes we have a fly-off.

However, whilst this is easy for the skilled flyer and/or for those whose model will usually fly long enough to get a max, it tends to disadvantage the novice or the less-skilled flyer whose lift-finding skills might not be as good.

So, what we’ve done is to specify that everyone gets three flights, but only the best flight is used for scoring purposes – this gives the less experienced a better chance, but the best flyer with the best model will probably still win. We will still have a fly-off if necessary.

Size Matters

So, what size models should we allow? This whole area is a bit of a minefield so for the moment we have borrowed the model definitions from the Flying Aces Club (FAC); the standard FAC Rubber Scale competition will be open to models in the following size range:

1. Multi-wing: Greater than 13 inches, up to a maximum of 30 inches.
2. Monoplane: Greater than 13 inches, up to a maximum of 36 inches.

This is quite a wide range but with the addition of a set of small bonuses that are based on what the FAC uses, we expect that there will be a reasonably level playing field and we can always adjust it if it’s obviously wrong:

 

Bonus/Penalty	Feature
0	High-Wing Cabin and Shoulder-Wing Monoplanes.
5	Mid-Wing.
10	Low Wing.
10	Multi-Wing (biplane, triplane, etc.) or Sesquiplane.
10	Seaplane with multiple floats of proportional scale dimensions.
10	Flying boat or Amphibian.
15	Multi-Engine with propellers mounted each side of the centreline (e.g. D.H. Mosquito, etc).
-15	Model does not have representative markings (e.g. national military or civil markings). This penalty will be waived on production of published documentation that validates the chosen colour scheme that has no markings (e.g. Bleriot, etc.)

A PDF of the Rules can be downloaded here

What should the maximum flight time be?

This is a tricky one; take a look at this:

The graph uses known data and shows that the primary influences of how long a model will fly appear to be wingspan and weight – nothing else. A lightly-built Dime Scale model (16” span) weighing 11 or 12 grams can easily fly for 60 seconds, twice as long as a very robust Keil Kraft or Veron Kit Scale model that weighs two or three times as much.

However, if you enlarge the same KK/Veron Kit Scale design by 50% (an easy thing to do at a print/copy shop) then it should fly for at least 60-75 seconds.

So, if we’re talking about models with a wingspan of 30” to 36” it looks as though a maximum flight time of 60 seconds is too small. Most/many of the FAC classes use a 120-second max which in the right conditions with the right model and calm (Continental) weather is easily achievable, but many of these models are very light indeed and are more like indoor models in terms of construction, so they wouldn’t last long in the UK. On balance, then, it looks as though a maximum flight time in the region of about 90 seconds (one and a half minutes) is probably about right.

We’re hoping that people will be inspired to build a larger rubber scale model over the winter, done properly they are extremely rewarding to fly.

What Sort of Model Should I Consider?

One that you like. Seriously, this is the most important factor – even simple scale models take a little longer to build than conventional models so keeping the enthusiasm going is vital.

Having said that, there are some general recommendations that can be made. Obviously, a bigger model will fly for longer but many FAC competitors in the U.S. tend to focus on models of around 24”-27” span; this is a handy size and if built very lightly (as many are) will regularly exceed a 2-minute max. Our max is only 90 seconds, some people will be able to pick the air and will be able to produce 3 maxes, but as you only need to get a max once in three attempts you probably don’t need to build a really large model to do well.

A couple of other things to consider; firstly, it might be quite difficult to spot a camouflaged model in the long grass on Port Meadow – an area of a contrasting colour is a good thing. Secondly, a dangling undercarriage adds drag and weight and is easy to damage; it’s usually best, therefore, to model the undercarriage retracted. Finally, experience demonstrates that a reliable adjustable node plug makes life so much easier – start off with ~3 degrees right and down thrust and you probably won’t go too far wrong.

Plans

Earl Stahl 24″ span P-51B Mustang actually represents a P-51A. Flies really well but leave off the undercarriage because it’ll only get damaged.

Anything by Earl Stahl will fly well. Outerzone has a lot of plans for Flyline kits, these are usually very good indeed – David Lovegrove has arranged for some laser-cut parts to be produced for the Stahl Mustang P-51B (which is actually a P-51A), a number of these are expected to be built over the winter, contact David for details.

Or you could just enlarge a Veron or Keil Kraft design (many available from Outerzone) by 50% at a print shop – a 20” design will enlarge to 30”, which is a good size and should fly for over a minute, more if you can build it light.

Kits

Volare products in the U.S. are nice people to deal with and have several suitable kits as well as lots of accessories. Easy Built Models (also in the U.S.) have a wide range of kits of varying accuracy and performance, some are very good fliers, but some are designed as display models – read the small print! If you can find a Herr kit (usually 30” span) on eBay or similar they seem to have suitably light construction.

Dumas kits are available in the UK and the larger ones (30”) are fine, but you might have to replace some of the wood; on the other hand, they are quite comprehensive kits and come with Decals. Mike Midkiff short kits and plans are available from Ozark Model Aviation, you’ll need to pay via Western Union which can be done at some Post Offices or online.

Members Models

Ivan Taylor’s KK Auster enlarged to 36″ span. It weighs 65g minus motor, which will probably be around 15g. It is equipped it with a Tomy timer for DT.