Blade 400 tail end problem

[tourerjim]

My son has vibration problems with tail end of his Blade 400 its like a bobbing vibration. He hard landed it and damage the boom and trail end.
This vibration has only happened since he completly rebuilt it (new parts)
Ive had a look and cant see anything wrong Ive even run it up without the blades but cant feel or see anything i even fitted new main blades checked belt tension just cant work it out.
Has anyone experienced this problem.

[Boggy]

sounds like he may have bent the tail shaft

[tourerjim]

Boggy
Boom and everything tail end has been replaced.

[Boggy]

is it a high frequency vibration or bobbing slowly? the later is usually low head speed.
if its high frequency ..well new blades? are they balanced. are they tracking correctly. is the feathering shaft and main shaft straight.(its possible to bend the main in flight!!)
if the boom and tail is all new i would look towards these two shafts!

[tourerjim]

Boggy
its as you say high frequency, i think you could be right i will need to look further forward.

[Boggy]

take the blades and flybar paddles off and run it up. if they are eliminated and its still there use a pencil tip on a rest as a dial gauge.to check the main shaft. mind that flybar though it becomes nigh on invisible

[tourerjim]

Ill give ago Cheers