"Bill Daniels" wrote in message news:
Reducing bank angle from 45 deg to 30 degree will double your turn diameter.

Not a big deal and I did it wrong the first time, so won't vouch for
this one either, but think the diameter increases by 73%, not 100%.
The pertinent equations seem to be

Fh = m v^2/r

where Fh is the horizontal component of lift

and

Fh/mg = tan(theta)

where theta is the angle of bank, yielding

r = v^2 / [g * tan(theta)]

so

r(30) / r(45) = tan(45) / tan(30) = 1.73...

Any corrections are welcome.

Martin