The Flying Black Thing.
April 2007 – The Son of Black Rainbow.
I wasn't planning on building another flying machine so soon. I was thinking about making a tube I could cut several propeller shrouds from but I got carried away. Sometimes I just can't help myself. Sometimes an idea grabs you and demands to be given flesh.
rainbow started with a shopping trip to buy wax. I still had
enough wax (just). This project started with a shopping trip to
buy a 26 cm cooking pot. Inside this pot was placed a cut-off
plastic bucket full of water and the remaining gap was filled with
molten wax. This formed a tube for moulding the propeller
This model was intended just to be tough – camera carrying is a bonus.
resin infusion is my standard way to make composites these
days. To make things interesting I infused the shroud and battery
tube in one operation so the bounding between the two is as good
as possible. The carbon was laid up dry and held in place with
sewing cotton and dressmakers pins. The resin diffusion medium is
cheap thin shade cloth. The resin was infused through the port in
the lower left of the photo and vacuum applied to the inner part
of the wax tube (port visible upper right). The infusion port was
pointing up during infusion.
were also some wrinkles where the carbon was too loose. With care
I might have been able to massage them out but I was under time
pressure and missed it. I ground these off later and patched them.
These photos are after the initial trim. The holes along the
inside are where wooden pins held the two wax plugs in alignment
during infusion and curing.
it is ready for it's test flight. It has been trimmed some more. I
expect it will be trimmed more after I get the bugs out. The
battery tube has holes added for lightness, ventilation and
access. The large hole it for the camera to see out when mounted
for side view.
steering is above deck this time. The rainbow's steering works
fine but gets in the way when trying to position things to adjust
COG. This one uses a bluebird metal geared mini servo with a
servo arm. The cyberchute servo arm
extenders are too short so I made my own. They are made from some
clips I found in the tackle section of a cheap shop (crazy
clarke), some antenna tubes and golden cable. Golden cable is
brass plated steel wire. The cable is passed through the tube –
the ends looped back and soldered. Two layers of heat-shrink
stiffen the clip attachment.
Up and away!
I'd also like to report it successfully flew the rainbow kite but again I can't. It did fly a little better than on “the black rainbow” but ultimately the gondola would become unstable the twist the lines.
This aerobatic manoeuvre was unintended.
Just adding the camera weigh may be
propeller causes several problems. It causes a roll in the
opposite direction to the direction in which the prop rotates. It
also has gyroscopic effects so when the model wants the pitch nose
up the forces cause a sideways twist (ie yaw). The same it true
when turning – the nose will want to pitch up or down
depending on the direction of the turn.
I'm not ready to build another one but unless I can get this one working easily a co-axial design might be appear here one day.
I'm experimenting with fixed rudder like fins stay tuned.
Thanks go to Len Martin for taking the action photos for me.