Learning to fly R/C
I though the fist thing to do was to learn to fly radio controlled planes as I don’t want to put a huge amount of time into building a pterosaur model, only to crash it on the first flight. So I bought a Radian, which I managed to lose after a few days. I now know that somehow it lost communications, because it was up high and then just spiralled down into some tress, maybe a river, never to be seen again (by me at least). Lesson to self – get a bearing as the model comes down so that you know the line to follow when looking for it.
I replaced the lost plane and the next one lasted longer and survived a few crashes and contact with tress, but one day I managed to pile it in at full power. But I was actually getting the hang of things when gliding and under moderate power, so thought it was time to move up to a more complex model with more controls – the Radian Pro. It has flaps and ailerons, so more control in the sky and the ability to slow right down for landing. That model is still in one piece.
I also bought a more sophisticated control set – a FrSky Taranis, which can be programmed to do all sorts of different things. That will come in handy for an unconventional thing like a pterosaur.
I have become a bit hooked on the R/C flying for its own sake – not a proper substitute for the paragliding I used to do, but much safer! The Taranis system has telemetry so I can measure sink rate, speed etc and work out the flight characteristics. The best sink rate seems to be between 0.5 and 0.6 m/s, which makes it similar to many birds. The wing loading (around 25N/sq m) is a bit lower than the local gulls and corvids of similar weight, which are around 40N/sq m, but similar to our ever present buzzards. So I am flying something with a performance comparable to the local birds, but the buzzards can out thermal me every time!
But enough of my toys, what about the pterosaur?
The plan
My ultimate goal is to make a 6m span model and fly it over the cretaceous cliffs of the Island. But one step at a time. First I will build a 3m span model and get the hang of things at that size. First I will build a single wing and test it on my zip wire system and it that appears to be reasonable flap free and capable of generating a good amount of lift, I then make another to have pair and attach them to a simple body. I will start with a tail and rudder, so a conventional aeroplane set up, but with membrane wings and measure the sink rate and flight speeds.
Then will come the scary bit – flight without a tail! There is going to be a lot of trial and error here, most likely keeping the tail at first, but also having control from moving the legs. But this is where it gets interesting – how did pterosaurs control their flight path? Indeed, how do birds do it? One things that pterosaurs could do that birds cannot do is to control their wings to some extent with their legs. By raising and lowering the legs, they could change the local angle of attack of the wing membrane, and by moving the legs laterally they could change the tension in the membrane and thus the camber/drag. My plan is to have these controls available but to get the model up high with conventional controls before trying to control with the legs…..
The Body
The body is now done. A simple carbon fibre/foam structure with no attempt at this stage to make it very lifelike. The profile is taken from remonstrations, but at the end of the rostrum there is a bulkhead for fitting an engine. Wishing the body there is a level surface to which are attached the servos for controlling eh rudder, elevator and the legs.
