A Control Line project

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slowmotion During the time I was beginning to compete in competitions and regularly flying at the local town site. I had realised the limitations of the Veron Cobra I had used as a test bed originally, so I came up with idea of designing a development platform based around a 35-40 sized engine. It also had to be cheap, quick, and easy to build

The other important piece of philosophy was, 'there are no rules.' This model was meant to be just a starting point, I envisaged different people building it in different ways and literally chopping it about to try things out, or just to make it look different; hence my twin fin version. As it turned out people tended to just stick to the plan, because it worked. This was slightly disappointing, but not overly so.

Everything was based on stock sizes of balsa wood, for example the fuselage comprise of one stock length of 913 x 75 x 12.5mm balsa sheet. The engine bearers where standard 12.5mm square boxwood, which was very cheap when bought from a carpentry store.

The wing section adopted an old trick the combat guys used in the pre foam and mylar days. The ribs aft of the mainspar are strait in profile back to the trailing edge. If the wing has a constant cord, and as long as the building board is flat, it is very easy to build the wing accurately with no warps.

I also needed the control system and the fuel tank arrangement accessible to try out different ideas and layouts, this was made easy by the profile fuselage design. For example, try as I might, I just could not get an RC type clunk tank arrangement to work reliably, although I had seen others use it successfully, and needed to try out different metal tank and vent arrangements. Also having the lines externally on top of the wing may not be elegant, but it makes things very easy to adjust, and also simplifies the wing construction a great deal.

The unusual forward position of the sheet cockpit was deliberate. It served the dual purpose of protecting the engine needle valve assembly in the event of an inverted landing (something that is a distinct possibility when experimenting or trying out something new), and looking different from the average model

in flight

[ RECENT NOTE 2006: Even after writing all of the above, people still seem to get the wrong idea about what the SlowMotion was/is all about. It was first and foremost a DEVELOPMENT PLATFORM. It was never intended to be a finished fully competitive stunt model. Everthing was exposed and sitting in the breeze to allow easy access and quick changes to be made to every thing from engine and fueltank, to bellcrank throws and gearing, and even changes in tailplane area, fin shape, undercarriage position, fin offset, and anything else you can think of. That no one ever did, must be some sort of testament to the fact that I got it about right the first time.

The model was deliberately built light and almost fragile to cope with the almost inevitable sick engine run when experimenting with fuel tanks. It was full aerobatic (on a calm day) with a Fox .35 slobbering away on an extremely over rich setting with a very restrictive silencer attached. A heavy model will not cope with that sort of thing.

Another common mistake made by people is to move the cockpit back to a conventional position because, 'it doesn't look right'. There is no law that says you cannot do this, but if you intend to use it to get some practice at flying the stunt schedule, you WILL! at some point end up doing a deadstick inverted landing, and unless you have a modern rear mounted needle assembly there is a very good chance of breaking the needle assembly. Inconvenient and annoying to say the least. The alternative is to make some sort of needle protector; not difficult, but it's much easier to stick a cockpit shaped piece of wood at the front of the fuselage.

Another comment I heard from an experienced stunt pilot was, "That's a bad place to have the bellcrank." referring to to the bellcrank screwed onto the top of the fuselage. Of course it is, if you are an experienced F2b pilot; but if you are learning and still finding you feet, low cost, ease of building, and easy access to everything, is of much more importance. When you get round to building the second model is the time to think about doing things like putting the bellcrank in the wing, wing mounted undercarriage, etc.

It all comes down to a simple choice. Do you want to build (or buy these days) and attempt to fly a pretty ornament. Or spend as little time as possible building a not very pretty model, and getting some actual flying practice in; which is what stunt flying is all about. You can see from the picture below what lessons learned with the SlowMotion led to... '57570 (my old SMAE number)', and that model was competitive. ]


Because it was so easy to build and adapt to any layout desired, the model proved remarkable popular. Also the fact that it was capable of flying the full aerobatic schedule in a reasonably docile manner made it an ideal introduction to pattern flying, especially the novice schedule.

the gang

Above is an illustration of some of the variants (Albeit very similar ones) that were built by different people, and all flew well. This simple concept did indeed help me to develop reliability into my full stunter for competition work, which I am holding second from the left. The model extreme left, is also a variant on the original design.

To download the sketch drawings, if anyone is interested in building one:
right click on each link and choose 'Save Image Target' in Mozilla or Netscape, or 'Save Target As' in Internet Explorer.
They are not good but should print at A4 size and be understandable.
To view left click on link.
Conversion tables are provided for anyone that can't, or won't, use the metric system.

slowmotion1 (18K)gif print size A4
slowmotion2 (24K)gif print size A4
size conversion tables

If anyone should be mad enough to build one build one, please send me an email and let me know how you get on. I will even put a picture of it on this site.

In case anyone should wonder why the plan is named 'SlowCoach' and I call it 'SlowMotion', the original model with the twin fins pictured above, was called 'SlowMotion', and was the only version I ever built. The single fin version on the plan, was a suggestion by me to make things easier to build: this is the version everyone else built and kept mispronouncing 'SlowCoach'. You can call your own anything you want. When I finaly get round to producing the CAD version of the plans it will be the twin fin version, as I (originally) intened it to be, and called 'SlowMotion'.

The plans below are of a scaled down SlowMotion and should print at A4 size For photographs of the model C/L project spinoffs
The CAD's link to dxf files, which should be readable in other CAD applications, but no guarantees.

Herbert Garritsen's Small Coach 1/3 41KB    CAD1-3
Herbert Garritsen's Small Coach 2/3 38KB    CAD2-3
Herbert Garritsen's Small Coach 3/3 47KB    CAD3-3

Here's some pictures to start the ball rolling

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