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The EPP Revolution      Next ]


Silent Flight Vol. 7 Issue 2

by Stan Yeo


Everyone is no doubt aware of the sudden proliferation of (EPP (Expanded Polypropolene) models on their local slopes. Some no doubt loathe them but many more love them. For me the jury has been out for several months and whilst I view them positively I recognise there are a number of drawbacks i.e. they have led to some reckless flying which has annoyed a number of people and they do little to enhance our building skills. The good news however is that EPP models have drawn large numbers of people into or back to the hobby and encouraged many other flyers to have a go at slope soaring. I have always regarded slope soaring as the fun side of the hobby, on a par with the control line flying of my youth, where investment in time and money was `justifiable` and a much more happy go lucky attitude prevailed. This to some degree has been lost in the high performance, high tech, high value machines a lot of modellers operate today. EPP for me has recaptured this nostalgic view of model flying and judging by the correspondence I get I am not alone in this view. For years would be modellers have been looking for a low risk, low cost entry into the hobby. EPP has met these requirements.

Out hobby/sport is suffering like so many similar pastimes where the initial investment in time and money is fairly substantial and the risk of failure relatively high. Add to this the pressures of modern life and it is easier to find an `excuse` not to do it than to take the plunge. Fortunately for us the desire does not go away as these people (what an ugly phrase) continue to cherish the dream and to buy the magazines. Along comes EPP and suddenly the dream becomes realisable. The price of radio equipment is at an all time low, (my first proportional set, a DIY kit, cost 107 whilst my take home pay at the time was 96 per month), the skills required to build the model are minimal and when you do make a mistake (notice - not if !!) the results are not disastrous. Yes these models are being used for combat flying, they do annoy some modellers and it is a problem we must address but they have given the sport a real shot in the arm in the form of new blood and the rekindling of enthusiasm in established flyers. Our problem now is how do we nurture this `new blood` and capitalise on the enthusiasm generated by EPP so that in years to come we have a new pool of vibrant modellers to take over from us that are growing long in the tooth. This can be done a number of ways via publicity, competitions and achievement schemes.


Magazine editors are universal in their cry for new material i.e. new ideas, new techniques and appraisals of current practises etc. I hear they are not adverse to the odd bit of club gossip from time to time either. From a slope soaring point of view there needs to be more effort to encourage the lone operators (clubs and individuals) that there is a benefit in belonging to a club or forming a collective. For me there are three elements to the hobby, building, flying and socialising. If one element i.e. the socialising is missing my modelling pleasure is not complete. Most modellers are very reserved and tend not to offer assistance for fear of fluffing it or making a fool of themselves. Yes we all know of instances where assistance has been given and the model wrecked, I have to admit I have done it on more than one occasion much to my embarrassment. I felt terrible but it is worth remembering that if, after carrying out all the necessary pre-flight checks, the model still crashed then what chance would the inexperienced modeller have stood.

Achievement Schemes

When I flew full size (I had a 1/2 share in a K6 for a number of years) and was undergoing `ab initio` training, I was issued with a flight check card, This contained a list of basic flying skills and after each period of tuition the instructor would initial and grade the skills covered, This acted as a record of progress both for the student and the instructor. If we had a similar scheme operating at club level for the various flying disciplines it would encourage flyers to develop these skills if only to get them ticked off on their card, No doubt schemes like this do exist but they are not the norm and I have not encountered one in slope flying circles. The word `publicise` immediately springs to mind, I keep threatening to design a slope soaring `skills` checklist for my local club in an effort to `widen` the flying envelope of the flying members but as yet have not got around to doing it!! This would include such things as trimming and determining the correct centre of gravity position, basic manoeuvres like diving and turning as well as more advanced aerobatics. I recently visited a `foreign` slope and met a number of modellers, One was flying a Wingbat + and whilst it was flying well and the flyer was more than happy with the model it was not flying as well as mine. Naturally the owner asked me why and after a minor C of G adjustment it did. Unfortunately his pleasure was short lived as we had a mid-air a few minutes later. Another modeller was having difficulty rolling - 10 minutes tuition cured this. Please do not interpret this the wrong way, I am just trying to illustrate that with a little help from each other we can all improve our flying.


60" pylon racing started out as an attempt to redress the balance between the high performance / high cost multi-task machines and the sports models that were being flown in slope comps at that time. Unfortunately this low cost / low tech approach did not last long as a competitive 60in pylon racer now costs around 250 to 300 to put in the air and followers of this discipline are beginning to count the costs of flying these machines. In fact my latest 60in EPP pylon racer the Enigma was designed in response to requests from the 60in pylon racing fraternity for a more durable low cost 60in racer (incidentally they make excellent aerobatic sports models). Please do not get me wrong, in no way am I not knocking these machines or the people that fly them. Both make a considerable contribution to the sport and help to keep it alive by exploring/demanding new materials and equipment plus developing the necessary skills and techniques needed to get the best out of the models. We sports flyers have benefited greatly over the years from this development process. Two examples are engine performance (power output has doubled in the last 15 years) and `computer` radios. I personally am a fan of computer radios, with all the mixing facilities and the exponential control. They allow me to fine tune a model`s handling characteristics to my personal taste. Years ago when rates were first introduced I considered them dangerous as they reduced overall control authority and consequently never used them. I found in certain situations this could be hazardous. Now with exponential control movement you can `soften control response around the neutral without compromising overall control authority.

Competitions improve competency, as does performing aerobatics. Competitions are viewed by a lot of flyers as high risk pastimes and consequently are given a wide berth. Not anymore with EPP which is a good reason why we need to embrace EPP as soon as possible and design a number of EPP specific competitions. The rules must be constructed in such a way as to discourage the hi tech development of these models as this invariably will kill any popular appeal that it can generate. The rules must also insist that EPP models only fly against other EPP models otherwise no one will fly EPP in competitions because wood and foam veneer models are inherently more competitive. This would of course kill any embryonic EPP comps before they had a chance to mature. My suggestion is that the fuselage and wing must be primarily made of EPP and for safety reasons a maximum weight is placed on the model. This weight would of course evolve in the light of experience but for 60in pylon racing an initial max weight of 3lb or 1500 grams would be a good starting point.

Slope aerobatic competitions have had little support in recent years and I can understand why, they can be a high risk, particularly if the lift is poor and judging them is a bit of a chore. Problem one disappears with the use of EPP and problem two can be overcome if the schedule is against the clock with only a cursory regard to quality. I can hear aerobatic purist tut tutting but please remember the best pilots will still win without the disadvantage of discouraging the also rans who one day could go on to win honours themselves. Incidentally I regard aerobatics as an insurance policy for when things go wrong as they sharpen up your reactions and judgement. I used to use them to 'waken' me up after a long flight when I was flying full size, I like to be 'awake' when I am coming into land, it is when things are most likely to go wrong!

Suggested rules for discussion

The only general rule I envisage at this point in time is that the wings and fuselage must be primarily made of EPP. However hardwood wing spars and internal ply doublers would be allowed to give structural rigidity and strength.

Additional rules for:

60in Pylon Racing


1. Maximum weight of model 3lb or 1500 grams.

2. Course length is 80 metre to place more emphasis an pilot skill and make an allowance for the models flying slower.

3. Heats are run in slots with 4 to 6 models as per F3B to determine the flyers in a three heat fly-off.



1. A set schedule to be performed in set order.

2. The time would start from time of launch with a mandatory 30 second count to gain height before starting the schedule and ending with a low flypast in front of the timekeeper.

3. Manoeuvre must be recognisable by majority vote to count.

4. Time penalty for non completion of a manoeuvre. This would be based on the estimated average time to perform the manoeuvre plus a 50% penalty. This would encourage the inexperienced to have a go knowing that failing to perform a manoeuvre would not result in a no score.

The schedule could be made up of 10 manoeuvres that are performable in the prevailing conditions i.e. in light lift conditions height burning manoeuvres such as a three turn spin could be replaced by 3 off 360 degree turns etc.

The above is only a suggestion to start the ball rolling. As with all things it will no doubt be modified in the light of experience.

I hope you have found this article interesting and it has given you some food for thought and encouragement to widen your flying horizons. EPP is here to stay, it is doing a great job, the models are getting better, so lets use it to our maximum advantage to further the aims of our hobby/sport.

Stan Yeo