Monday, July 13, 2009

Polishing a turd

As my experience with the RC crack habit has increased I've become a bit more cocky, and lately I decided to convert my old Aerobird Xtreme to stock electrics with a Spektrum AR500 receiver.

The basic process of conversion from those older style custom Hobbyzone electrics was pretty simple.

I went from this:

To this:

The new electrics allow me to use my main DX6i transmitter, which is a nice change from the stock Mode-1 thing that came with the 'bird. The flight characteristics are the same - that is to say that it handles like a pig and wants to crash a lot! Compared to my Radian, it really is a bucket of trash.

Anyway, I decided to continue the modding theme and use some of my spare servos to add ailerons to the wing. Top stuff, I thought. I immediately set to work, marking my aileron positions and servo positions on the wings with a permanent marker and a ruler, followed by cutting the ailerons from the wing and hinging them using tape. I hot glued the servos down to the underside of the wing after cutting a void in which they could sit, and carefully fitted the control horns and servo arms. All good, and nicely trimmed.

There is only one problem with the ailerons on the Aerobird. Quite simply, they do NOTHING!

First, I managed to launch off-axis from the wind and crashed, which caused the wing to snap since I had weakened the skin from where the ailerons were cut out. After glueing the wing back together and taping the weak points, I headed back out but only to find that after getting in the air I had no roll response from the ailerons. Getting back on the ground when I only had my rudders and elevators but now on different sticks was a challenge in itself, but as always altitude was my friend and I was able to spend the needed time focus and line up for a clean landing.

Obviously, things weren't working as planned. It turns out I made a range of classic mistakes:
  • The ailerons are WAY too small (5 inches each on a 55 inch wingspan)
  • It's an overhead wing aircraft with a very heavy low-slung center of mass
  • The wings have a huge dihedral to stabilise the flight characteristics
Is it any surprise that these points are going to make it hard to turn? I'm going to have to accept that performing rolls is out of the question, but if I can at least get her to turn using ailerons and elevator I'll be happy.

I will double the length of the ailerons and fit carbon rods to them for stiffness, but in the meantime I have mixed the aileron inputs to the rudder 100%, so that I can still control her using the right stick. Certainly before I did that today, my first attempt was very difficult as I was airborne with zero response from the ailerons, and I am not used to using separate hands for pitch and yaw.

I have most definitely put too much money into this little plastic plane. Even stock, the Aerobird had twitchy handling - it's designed to be stable but the wind causes it to roll even in slight breezes, and it tip-stalls easily. Spiral dives are an easy thing to happen and the small elevator throws make it difficult to get out of trouble.

Ultimately I really am polishing a turd. However, it's my first experience with 4-channel controls and I suppose that it's better for me to experiment and learn here with a plane I will be less devastated over if I bin it. I have soft-mounted the AR500 receiver, so if I can retrieve that at the least, I will happily put money into a Parkzone Corsair Plug N Play.

No comments:

Post a Comment