A Question on V tail Mixing?

I've been trying to set up a V tail model, a Ripmax Blaze. On both my Futaba and Spectrum equipment, the rudder control on the Tx produces an elevator response on the model and an elevator input on the Tx produces a rudder response on the model. The model has four functions, rudder, elevator, ailerons and motor.

I've tried swapping the servo leads, but the response is the same.

I've also read both manuals to find they were of no help.

Aside from putting a servo reverser in the circuit to one of the servos, what can I do to solve the problem?

Thanks in advance for any help offered.....

Hi Andy You say you've swapped servo leads but do you mean you swapped them round on the each servo or from servo to servo?

Andy

Not sure which Spektrum tx you have but have you selected the' V Tail' configuration in the airplane set up menu? This is the menu where you select the wing config with one, two servos, elevons etc. There is a tail choice.

Ralpharr2001 wrote: Andy

Not sure which Spektrum tx you have but have you selected the' V Tail' configuration in the airplane set up menu? This is the menu where you select the wing config with one, two servos, elevons etc. There is a tail choice.

Thanks for the suggestion Ralph, but I'd selected V tail mode. However, the problem is now solved by reversing the direction on one of the servos in the Tx.

Thanks for your patience,

Signed,
A free flight modeller!!!

Andy
It always amazes me just how many combinations there seem to be on which servo in which channel and which have to be reversed and how rarely it is right first time.

Quorneng wrote: Andy
It always amazes me just how many combinations there seem to be on which servo in which channel and which have to be reversed and how rarely it is right first time.

Agreed Q. In many ways it was a lot simpler in the 'good old days' where differential was achieved by mechanically setting the servo arm off-centre and reverse by changing to a different servo!

Rather academic now, really, but I'd have said don't bother with the rudder. On my Excal, it is pretty ineffective, and I never use it anyway!
Just set the elevators throw to 50%, as it would be with rudder (also set to 50%) to prevent the servo trying to turn 465' when both sticks happen to be in one corner!
Put plenty of EXPO on ails and ele, and your bike clips on before you launch it on it's maiden fright! :evil:
(p.s. - that's not a typo!)

Andy Sephton wrote:

Ralpharr2001 wrote: Andy

Not sure which Spektrum tx you have but have you selected the' V Tail' configuration in the airplane set up menu? This is the menu where you select the wing config with one, two servos, elevons etc. There is a tail choice.

Thanks for the suggestion Ralph, but I'd selected V tail mode. However, the problem is now solved by reversing the direction on one of the servos in the Tx.
That was to be my next thought Andy.. Anyway well done John O/T

Thanks for your patience,

Signed,
A free flight modeller!!!

Thanks for the suggestions Eric. I hear what you say on the rudder, but I do tend to use it when I fly, so I'd like to get it working. I'll take on board the suggestion on expo, though

A colleague has also suggested that V tails should have differential as they produce adverse yaw in the same way as ailerons. I can see how that would work, but given the small size of the empennage on this one, I'm not sure the effect would be noticeable. On the practical side, when flying a Fouga CM170 Magister in France, I do remember that application of yaw produced a significant pitch down couple. I'll be investigating that characteristic on this one and will report back

In the meantime, I've set up the surfaces with equal movement and I'll see how that works.

Re the rudder on the Excal - I meant I don't use it on this particular model as it is ineffective! I was a bit vague with my comment. :oops: It is fitted with, but merely causes the model to crab about five degrees, then nothing much else happens. I suspect the small area is insufficient to overcome the natural directional stability, due to the airspeed, although the elevator is quite powerful (due to the fairly shallow V?)
Also, rudder on a V-tail - if you think about it - it exerts a rolling force in the 'wrong' direction - ie left rudder, both surfaces move left, but twist the fuz to the right.
I've not noticed any down-pitch with rudder, either on this model, or a sorta-Fouga I made, years ago.

That all sounds pretty good to me Eric. I’m not surprised that the rudder has no roll effect, you’d need dihedral, anhedral, sweep forward or back to get roll from yaw and The Blaze has straight flat wings.

As far as the Fouga was concerned, it near put my head through the roof when I pushed full rudder! It was a characteristic that lost the French Air Force several aircraft and pilots as the yaw and pitch down was pro-inverted spin.

Your comment on the negative roll moment from V tail rudder is also interesting. If you think about it, all rudders that are not symmetrical about the aircraft roll axis will produce some rolling moment due to their deflection and distance from the fulcrum.

The Excal has about 5' forward sweep - stall-turns are a non-event, it ALWAYS flips out, either neg or pos pitch, into a vertical dive, with a bit of fish-tail waggling on the dive.
I don't imagine you were allowed to try that in a real Fouga! :evil:

Eric wrote: The Excal has about 5' forward sweep - stall-turns are a non-event, it ALWAYS flips out, either neg or pos pitch, into a vertical dive, with a bit of fish-tail waggling on the dive.
I don't imagine you were allowed to try that in a real Fouga! :evil:

Ha ha...I can't physically remember stall turning the Fouga, but I don't see why it couldn't be done. The manoeuvre wasn't very practical in a jet, though, as there's no prop wash to help it round the corner. The technique was to yaw early, then hope that the jet would fall out of the vertical in the required direction. There was always a bit of luck as to which way it would go in the end

I only got about 10 hours in the French Fouga and most of that was research into spin recovery. Notwithstanding and given the pitch down with yaw, I found it to be an aircraft with superb handling qualities and control harmonisation. In that respect, it was very similar to the Chipmunk.

it was very similar to the Chipmunk -
IIRC, it WAS designed as a jet trainer, before the Alfa-jet came along. I DO recall seeing the Patrouille Acrobatique de France at a show, once, a long time back, flying the Fougas. They were a bit like turbine assisted gliders - energy conservation was the name of the game!