this is how i check the cg for a fully aerobatic model. trim the elevator for level flight at cruising speed (say 1/2 - 2/3 throttle). Roll inverted and see if it climbs or dives. If it dives then it has too much up elevator (longitudinal dihedral) which was balanced out by a forward cg when upright.  move the cg back a bit and try again with the elevator re-trimmed for level flight as before - it will need less up elevator when upright due to the more rearward cg and when inverted the tendancy to dive will be reduced - rinse and repeat until the cg position is established that requires an elevator trim (i.e. incidence) which allows hands off level fight when upright and inverted, or close to it.

During the testing, checking for pitch stability is advisable - this means putting the model into a steepish dive (30 degrees or so) with no elevator input held in.  If the plane gradually pulls out, back to level flight, you can move that cg back even more, it the plane steepens its dive or 'tucks' into the dive, then the cg is a little too far back - any further back and the plane could become divergently unstable - which means it goes home in a plastic sack.

A nose heavy plane that requires excessive longitudinal dihedral to fly level will also exhibit the characteristic of climbing steeply under high power, whilst often diving steeply when power off - the steep climbing due to over-elevation can be countered by adding loads of downthrust but its not ideal and won't help the power off diving condition. This is true for all planes. In the caet of a fully aerobatic plane it will make it a bit of a pig to fly, rolls became barrelly and she'll dig hard into tight turns like chronic understeer on a car.  So, getting the cg right is vital for a sweetly flying plane of any type.


<span class="info"> </span>