700 problems

[t-rex pedro]

OK gang, I need your help. My 700 is giving me problems. Specs are:

YS91SR / Hatori SB19
Spartan / BLS 251
JR 8717's
Radix 690 mains / Align tails
30% Optifuel

The problem is the tail (or manifesting on the tail). During normal hovering and flight the tail wanders (indicating low gain). Go into fast backwards or a pie dish then the tail wags to the point it can physically be seen and heard (indicating a high gain figure). The fuel tank foams and there is a mini storm going on in there. I have tried tuning the engine but it makes no difference. At idle the whole airframe vibrates turning the skids into a bit of a blur but this could be normal with a 90? Also, the tail assembly sounds and feels 'ratchety' and rough when controlled by the servo but nice and smooth by hand.

The list of changes I have made to try get the tail locked in are:

New boom (last one was a little bent, dont ask!)
New torque tube
New tail output shaft and TT gear
New engine bearings
Cleaned and regreased tail assembly
Fitted spare tail hub and grips as last resort
Tried a 9256 tail servo in place of BLS251 - no difference
Tuning engine for optimum power - no difference
Complete new plumbing

Its really wierd. The tail isnt locked in and wags in any kind of sideways/backwards flight (regardless of gain value).

Any ideas guys? Could it be the motor? Do I need to balance the fan/clutch? Could it be the tail blades? Could it be the Spartan?

A few clubmates had a look over it today.

Thanks for any ideas.

[haha101]

if it is manifesting in the tail it could be the TT i see that you replaced it but did you get the bearing spaced correctly i dont have a 700 yet and i would not take this advice to serious hope someone agrees with me :lol:

[caseyjholmes]

It might be the tail blades..
I had a funny vibe from my tail which I suspect could have come down to the tail blades or plastic tail grips, but others run them with no troubles.
Replacing the tail blades and upgrading to aluminum tail grips with a new tail shaft for the heck of it fixed my problem. The way I noticed all this was happening is I was breaking rudder control rod guides in flight.
Helicopters are crazy! :lol:

I don't think your skids should be vibrating. I was looking at mine in hover idle up very close today just before I crashed it and the skids were dead still. The whole airframe was..

[rcer04]

I had the same thing happening to my 700 tried every thing then found the ball on the tail pitch slider had come lose must have fogoten to lock tight it.

[deesee]

You should not be able to see any vibrating when you are at idle. I would check your fan is not way out of balance for some reason and that it is straight on the fan hub. I would also change the tail blades and upgrade the tail blade grips to aluminum if you havn't already done so.

[heliwill]

You might try changing the foam tape under the gyro. The tape that came with my spartan made my tail act similar to yours. I use futaba foam tape that come already cut in squares. Its the only tape that I have found that keeps my tail locked in.

[t-rex pedro]

Thanks for the replies guys. I have torn the heli down and giving it a complete once-over. Only thing I found was notchy clutch stack bearings. I need to DTI the fan/clutch and try new tail blades/metal grips and new gyro pads.

Thanks again guys.