T8 wrote:

He then mentioned that way back in the early days of flying they would
simply tape a string hanging from the ceiling to act as an artificial
horizon.

It's not April 1 already is it?

Just put a mark on your canopy and spit at it. If spit flies left of
target, you are turning right and vice versa.

-T8

NOW you're talking.
There was a D-I_Y autopilot design which used a blower tube streaming
air onto four thermistors arranged pairwise-differentially. This gave
pitch rate and yaw rate, or if mounted skew, inputs on all three axes.
These days, a three axis acceleraometer goes for $25 and rate sensors
for a little more... One well known Arduino project ["ArduPilot"]
offers the guts of an autopilot suitable for driving R/C servoes, which
will easily fit in a medium size model plane. I expect this could easliy
fit in a homebuilt...

Brian W