The BE-Shape is no-more. It suffered from an
"aero-dynamic problem" that caused it to pitch up and down if the
airspeed was too high. Eventually this happened going into a turn
and it went out of control and crashed badly breaking many parts.
I've not tried to rebuild it.
After I had got reasonably proficient at flying my Rotorshape, I
decided to to try something a bit more challenging. I had been
reading the Autogyro
Forum on RC Groups where I had read about the BEGi (Backwards
I ordered the kit initially without the pre-rotation drive.
I added the extra nose wheel in an
attempt to stop it nosing over on the grass, but the high thrust line
and high CofG meant it was never 100% successful. The later
addition of the pre-rotation drive helped but I still had great
difficulty in actually getting the thing to fly.
To cut a long story short I only ever got it to fly a couple of times
before it was destroyed.
However, it wasn't totally destroyed,
and I had an idea.....
Due to a "building mistake" with my Rotorshape, I now had a spare head
assembly and set of blades, so I set about working how to attach these
to the remains of the BEGi. This picture is of the first
"mock-up". As you can see the main undercarriage and tail
wheel, the main boom, the vertical fin and rudder all survived
and now became the basis of the BE-Shape. "BE" from the BEGi and
"Shape" from the Rotorshape.
I showed my idea to JochenK
who had produced the Micromum
and the Minimum
designs. He was very helpful and encouraged me to continue with
my idea. We exchanged several e-mails where he helped me to
determine the correct the rotor angle and motor position/thrust
line, based on his experiences.
After a few weeks of work the BE-Shape emerged ready for it's maiden
Here's a close up of the motor mount I
built. The slotted plate is angled to the mast with washers, such
that the thrust line is level relative to the horizontal
stabiliser. The slots allowed me to offset the motor to produce
the same result as "side thrust" on a conventional model. The model's
CofG came out just above the arms on the servos, and I set the motor's
vertical position so that the thrust line passed 25mm above the CofG
(Jochen's suggested starting point). The rotor support mast is
clamped between two pieces of ply wood so it's position could be
adjusted by loosening off the bolts. The initial position wasn't
far from correct, but on the first few flights it did tend to pitch up
and down as it flew along. Dropping the motor by 5mm cured that
After a few flights (see below)
the epoxy holding the plywood triangles to the boom and mast came
unglued, luckily not while it was airborne ! I took it all apart,
cleared off the old epoxy and added some binding threads. These
have helped to produce a much stronger joint as they helped to keep the
epoxy in the right place while it was setting, and the epoxy flowed
along them to produce a much greater glued area onto the main boom.
Although I rudder servo is much further back on the BE-Shape I had
retained the pull-pull control via thin thread. However
this proved to be hard to keep tensioned correctly, and eventually one
side of the horn broke so I replaced it with a simple push rod.
To start with I had fitted a GWS motor that I had lying about.
While it performed well for the first few flights it seemed to develop
a fault that made it fail to spin when the throttle was opened.
It may have been that I damaged the bearings when I reversed the shaft
to use it in a pusher configuration, but eventually it stopped while in
mid-air! I can't claim that I controlled it's decent but the only
damage was the epoxy joints between the plywood and carbon fiber tubes
I had used the GWS motor rather than the Hacker I had used in the BEGi
as it had a higher Kv rating and because I was using a 9" prop (rather
than the 10" on the BEGi) I wanted to spin it a bit faster.
However when the GWS motor failed I replaced it with the Hacker as it
hadn't needed full throttle at any point with the GWS.
Since I had got used to hand launching my Rotorshape I started off
using the same technique with the BE-Shape. Until one evening I
was faced with trying to launch with no head wind to spin up the
rotor. As you can see below I ended up running across the field
before tossing it into the air. Not very dignified!
When I was next faced with the prospect of having to run with the
BE-Shape because there was no wind I decided to try and take off from
the grass. Luckily the grass had been cut and compared to
the BEGi the BE-Shape has a lower CofG and more rearward
position for the prop which meant it didn't suffer from the same
nose-over tenancies. The first takeoff from the grass went so
well I've not done a hand launch since then.
Here's another video
which starts with a takeoff where if you look closely you can just
see that I'm holding the elevator stick back at the start of the run to
get maximum air flowing through the rotors. Once they start to
accelerate I released the stick and let it take off when it was
I've set up my transmitter (Futaba FF7) with a switch selected mix
which allows me to adjust the rotor angle via means of the "channel 6
knob". I've found this useful on the Rotorshape to reduce the
rotor angle when flying in stronger winds. This increases the
airspeed required to spin the rotor at the rate needed for level flight
and means it can be flown into wind with a reasonable ground speed
without it gaining altitude. I've also used it (as shown in
the video above) to increase the rotor angle to allow for slower ground
speed on approach to a zero roll out "spot" landing.
The same results can be archived by holding the elevator stick
up or down, but I find using the switched mix easier
as it doesn't feel like the model is out of trim.