Page Two.

The Black Rainbow, Black surfer.
The flying clog.

24'th July 2006.
Page one
ended with a fairly successful series of test flights. The fly in the ointment was some minor damage after a crash. Closer examination of the damage showed it to be trivial and that it was easy to secure everything better. Closer examination of the crash site make me think the model either flew into a wooden fence/wall or a brick retaining wall.
The heavy servo was being replaced anyway so I removed it along with it's mounting blocks and lashed the servo mounting bracket down with cotton instead of the kevlar I used in other places. Cotton isn't as strong but it is easier to work with.
The bluebird 380 servo is easier to mount because it is smaller and can mount horizontally.

The new servo was mounted on a bridge made from scrap CF board and scrap CF sandwich left over from the main fin. The CF is glued and well as screwed so it will be a little difficult if I have to pull it apart.
The spline on the new servo is slightly fatter than the hi-tech servo wheel I was mating it with. The spline has the same number of teeth and I managed to force it into place by using the M3 thread on the spline and a modified screw to pull them together.

All in all I saved about 35 grams is weight. The servo travel seems to be a bit less but I think it is enough.

With the lighter weight is it totally unflyable!
It glides fine but with power the chute will stall or the gondola will become unstable and begin to rotate from side to side. I think the former problem has as much to do with the hang point being high relative to the thrust line and the C of G not being low enough – as it does with the weigh being too low. I think a lot of models suffer from this and pitch up excessively. The thrust should be pulling the chute forwards not (excessively) upwards.
The second problem may be due to the prop being behind both the hang point and the C of G. Adding weight will almost certainly fix the problem and as the real payload will at least 150 grams the problem should vanish.

We had another trip over the fence and another landing in a tree. It crashed hard many times and nothing bad happened. The photo (above) was taken after the crashes and everything is fine. One problem I have is the throttle on the transmitter easily gets knocked. So I got the chute lines wrapped around the prop again when the model was on the ground and the throttle got accidentally bumped- I'd really like some sort of safety catch on this.

I don't think a plastic chute would have survived today's mishaps.
The next test will be with an extra 55 grams of battery fitted.
The extra weight fixed the control problems..

Camera payload module.

A carbon fibre payload module was fabricated and more info can be found in my vacuum infusion pages.

I made a wax replica of the camera top so I could make a carbon cover for it which I mounted a micro servo on. This can hit either the “on” or “shutter” button. I would like more clearance between the servo arm and the buttons but there wasn't enough servo travel to use the servo arms which were at 180 degrees and there wasn't time to make a custom servo wheel. This arrangement did work on the ground.

I went to Nimbin and attempted to test fly the new payload module. It was a little windy but I gave it a try. I had 1800mah battery because my 2200mah one died so it was a little lighter. The empty payload module weighs about the same as the original one so all up it was a little bit lighter. At this weigh control was very poor during launch but not to bad on descent. I had some bad takeoffs and crashes.

On my last flight the chute inflated well and it staggered up to maybe 20 meters. I progressively reduced power till I had more or less level flight and reasonable steering. Then the motor seemed to glitch and then stopped.

The solder on the esc had melted and 3 wire had come off. I later discovered a chip was missing – the solder had obviously melted and it had come off. The winding on the motor looked cooked.
Spinning the prop by hand felt very different. Normally if I spin it with my fingers it will spin for a few seconds but now it stopped much faster. It wasn't the bearings – it was braking due the dynamo effect in the short circuited winding. So that was the end of the flying.

Here is the burnt out stator. The insulation under the wire was also fried so I didn't reuse this stator core.

Fortunately I had a spare stator core lying around at home which I wound to match the original. I used coloured “newbie” wire. Not wound as neatly as the original but it is my first attempt. The colours make the three phases obvious. This is wound with 16 turns on each pole.

Clearly I have to be more careful with airflow to the motor for cooling. I've put a lot more holes in the motor tube and I may have to move the ESC to stop it shielding the motor from the breeze. I also ordered a double stator motor kit today from gobrushless in case I need to upgrade the motor. I had already made the motor tube with enough room for the larger motor.

A kit built double stator motor.
GBx™ Brushless Outrunner Kit (double) 18 turn delta wound.

Motor fitted with Phoenix-25 ESC.

Murphy strikes again.

Easter 2007.
Things never seem to be as easy as I expect.

After upgrading the motor, the black rainbow suffered a series of bad crashes on or shortly after take-off. This is I believe closely related to problems experienced by myself and others with sky-surfers (clones). The symptoms are different using the kite versus the plastic chute.

The kite will inflate and fly only using low power – just enough the climb slowly. Even a small increase will cause the gondola to spin and wind the lines up (if it doesn't hit the ground first). You can see I've used lots of plastic packing tape to make it more crash worthy and I've taped a soup spoon to the front to increase the weight.

The surfer chute doesn't have the problem of the gondola spinning. Instead the whole thing rolls on it's side. Out of the box my surfer clone launched ok but it had very little power and could not climb. As soon as I changed the battery to Li-Po, I had more power but also a serious roll problem. Even when the chute is flown on my home made gondola, the tendency to roll is still there.
Ted Robinson (UK) is reporting good results by changing the motor/prop mount so the thrust is off-centre.

Black surfer (BS).

The only successful flights for the carbon creation lately have been using the plastic chute from the surfer clone. It has survived far more crashes than I'd ever expected but is now in need of repair/replacement. I hate the waste of buying a complete model just for the chute but this seems to be the only option.

The surfer uses a 4 line rig – most models use two lines. Two line is usually referred to as “weight shift” steering but I'm not sure this is accurate. Anyway in order to fly a surfer style chute on my contrivance I had to figure out how to convert it to two lines. After some guessing and test flying the rig shown here works. It may still need some tweaking but it flies.

If the rear line extender (the plastic bit) is folded in half it is still a little but too long. So it is shortened more by clipping the clip a little higher on the pink lines and zip tied in place.

The Easter Saturday black surfer flights went moderately well. There is a little instability and the steering is very touchy compared to the surfer. I'm not sure if this is due to the two line rig or because the servos are much faster. I don't have as much servo travel here as on the surfer but it still seems to be too much.

I had a very brief flight+crash on Monday. The wind was gusty and I'm not quite sure exactly what happened. I flew with some ballast in the middle (instead of front) and I had the impression it flew better till the wind and most likely pilot error (I panicked as it neared a tree) terminated the flight.

Thanks to Mike Van Emmerik for pointing the cameras for me.

Cheers Eddie.M.

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