x tail subs and the controls

Hi.
I am having trouble with the tail controls on my robbe 212 class u31 sub build
I am using an w tail servo mixer from mtroniks, an although I can get the lower fins to act as rudders, I can only get one of the two servos to act on the outlet channel.
I have swopped over the servos, to make sure that the mixer was working, also both the servos, and everything is ok.
but the other servo seems not to want to work.
I have also tried plugging the lost servo into a channel on the receiver,
but to no avail.
As I am not electronically minded. I am now lost.
Robbbe mentions a v tail mixer. would this be the answer ?
If so can anybody please recommend a good one that I can purchase in England, not the states. or china.
cheers john.w. p,s the build is going well
and I can recommend the 212 kit.

Cheers Richard.
Im on it.!!!!!!!!

Hi.
Having received my v tail gizmo from giant shark, and installed it
I find my self with an interesting problem, the u31, class 212 sub,
uses the bottom two fins as rudders, which seems ok.
So when I waggle the right hand stick to and thro I get the rudders moving in opposite directions, which seems ok.
But the odd thing is, when I move the same stick up and down, I get both bottom rudders moving up and down together. so it would seem that I can control the
whole sub on one stick. the left hand stick, I use for throttle, as normal.
does that mean I can lock off the two top fins to neutral ?.
and save two brand new servos ?.
If so I am a lucky guy am I not.
OR have I missed something along the way.
If anyone has experience of these tails, knows different, speak now or for ever
hold your peace !!
Where have I heard those words before ? !!!!!!!!!
Cheers John.W.

Hi John W,
I cannot speak about X-tailed submarines, but have built and flown many Vee tailed aircraft and flying wings with 4 control surfaces, mostly gliders, and your mixer is working exactly as it should by combining the two axis of control onto one transmitter stick and providing the appropriate output. I would think that if you wished to get movement of your upper pair of fins, then you would simply need to fit a Y lead from each of the two Rx sockets that you are using for pitch and roll and connect your additional servos. The upper fins would then duplicate the movements of the lower pair, maybe you would need this extra control authority maybe not, as I have no experience of this type of submarine or how they behave,

Regards,
Trevor

Hi There Trevor.
Thanks for your welcome reply.
It backs up what I believed, and is a help.
II will try your suggestion. it will save destroying a lot of work
already carried out.
Usually the top pair of fins would be used to dive, but the sub would need to be very low in the water in the first place.
many thanks again.
Cheers John .W.

Hi Trevor
The set up has now been joined to the four tail fins,
and works beautifully, I am awaiting on a couple of y leads.
and I will have a fully working sub.
cheers for your input, and many thanks for your help.
cannot wait to try
it in the bath, that's if the bath is big enough !!
Cheers John .W.