Main blades on my 700N DFC

[chris427]

After i set up my 700n DFC with a AR7200BX on spool up something went wrong and it nose dived in to the grass and wrecked the align blades it had on it.
I've reset the 7200 and done another set up from scratch and found some cheap new Funtech 710mm carbon 3d mains so bought a set at £30 far cheaper than £100 if it kills them again.
My question is, i know these are for flybar heli's so not really a problem but the align root is 8mm give or take and these are 7mm so i have shimmed them, with proper shims like i used to on the old Freya 90 i had many moons ago. I have set it all up with them shimmed, got it levelled and 0 degrees on menu G, 6 degrees and blue light on the other menu, set the pitch max and neg range and set a pitch curve ready so as far as the system knows they are all good to go.
There's always a slight what if in my head but just really wanted to ask if there's any problem using shims on a DFC head?

[trillian]

You're talking about just some shims to fill the gap between the blade root and the grips (if I understand correctly) in which case it won't make any difference to the DFC head.

But regarding the nose-diving on spool up. There are two possibilities that come to mind. The first would be making sure that the orientation is set correctly so that it is correcting in right direction. usually you can see this by tilting the heli with the FBL unit initialised and if you tilt it forward the swash should tilt back, if you tilt right the swash will tilt left etc.

The second thing would be if it's getting some kind of vibration that is freaking it out. I had this happen on the Trex 500, but it would only do it when it reached higher rpm and then it would pull hard left and I'd have to wrestle it back with right stick and then it would settle down. The cause of that was due to the tape being too soft and it allowed the BX unit to vibrate at some kind of resonance.

The bottom line being that I'd figure out what caused that and get it sorted before spooling up again with blades on it.

[chris427]

Yes exactly that, just a shim in the bottom of the blade root. Worth doing as the blades were only £30 a pair and we all like a bargain.
On the set up, yes i have checked and double checked the swash direction, all is as it should be, i double checked the orientation too so it should be right.
On the other idea of the tape being too soft, i have to agree there as it was fine as it went light on the skids, no input from me and it was level and all i did was slightly increase the revs to set a head speed at hover point as it was it's first flight then as it left the floor and the head speed increased it just head butted the dirt and tore the blades to bits and a few linkages so sounds like what you described. I have the settings for the unit on really docile so i can at least get it in the air and check things over but the way it went was like full forward but no pitch increase otherwise i would have been waving it goodbye! Luckily it spat the battery off and went to fail safe to saved it doing the funky chicken, never even damaged the boom so very lucky.
The tape i'm using is 3m thinnish stuff the same as the 600N is using without issues but i also have some other 3m tape that i will swap over and try, without the blades first so i can see if it goes mental as the revs increase, thank you for your input.