Thread: Some Vbar funnies ( will a trim flight fix this? )

OK so I've got my 500efl running a mini vbar running express SW. Align ESC and motor ungoverned, MKS servos and standard blades.

I've noticed three things today and wondered if any of them are likely to be solved with a trim flight.

First thing is if I punch the collective up hard the tail kicks out a small amount but is brought back. I'm guessing the only way to fix this is pre-comp using Vbar Pro.

The second is if I go hard +ve, -ve, +ve etc to make the heli climb then fall rapidly then the heli drifts left a bit through it. During a piro I think it drifts right but I haven't tried a piro the other way.

The third thing is that sometimes during forward flight the heli kind of nods a bit, it's tiny but noticeable when it does it, but most of the time it doesn't do it.

It flies beautifully really, and these are picky things. This being my first venture into vbar or FBL I'm not sure what to expect a lot of the time.

First thing is if I punch the collective up hard the tail kicks out a small amount but is brought back. I'm guessing the only way to fix this is pre-comp using Vbar Pro.

If the tail kicks to the right (with the tail pointing at you), lower the pitch precomp by 2 points and try again. if it kicks left, increase if by 2 points and try again.

The second is if I go hard +ve, -ve, +ve etc to make the heli climb then fall rapidly then the heli drifts left a bit through it. During a piro I think it drifts right but I haven't tried a piro the other way.

This is likely to be CofG balance. Alternatively, it could be that your swashplate is not perfectly level?

The third thing is that sometimes during forward flight the heli kind of nods a bit, it's tiny but noticeable when it does it, but most of the time it doesn't do it.

As long as nothing is bent on the model, this could simply be that your swashplate gain is a little low. Take the swashplate gain up until you see an oscillation on the swash when hovering, then drop it down a few percent and fly it. If it still oscillates in harder manoeuvres, just drop it a little more. You should run the swash gain as high as you can for the best feel in flight.

It's good to be picky - all of these things can be resolved on the VBar, it's awesome
Cheers,
Rob

Thanks Rob.

CoG is pretty much spot on, If I pick up the heli by the grips the skids stay perfectly flat with my 2700 Optis in there so I don't think that's a cause.

I do only eyeball the swash being level, so it's possible it's not perfect, but with my FB helis I've got them spot on as far as I know up until now.

On the other things, forgive my ignorance, but can any of them be tweeked in the Express vbar SW or do you have to be running pro?

The tail kick is to the right on full +ve pitch.

CoG is pretty much spot on, If I pick up the heli by the grips the skids stay perfectly flat with my 2700 Optis in there so I don't think that's a cause.

I find the same with this pack. But do you lift the model up by the grips so the main shaft is then parallel to the floor? When you do point the nose to the left which will show if it is nose heavy and then point the tail to the left and it will show if it is tail heavy, unless you disengage the pinion it will hold against the one way bearing.

Mine also has that kick to the right, so thanks Rob I will give that a go. Mine also starts to wag if I allow the model to continue to climb.

Originally Posted by Andy from Sandy

I find the same with this pack. But do you lift the model up by the grips so the main shaft is then parallel to the floor? When you do point the nose to the left which will show if it is nose heavy and then point the tail to the left and it will show if it is tail heavy, unless you disengage the pinion it will hold against the one way bearing.

Mine also has that kick to the right, so thanks Rob I will give that a go. Mine also starts to wag if I allow the model to continue to climb.

No I have the grips at 90 deg to the heli then just pick up the heli by the grips only. If the skids stay level I would think that's a good indication of CoG surely?

Pete take a look at page 34 of the manual. This is the preferred way to be totally sure of how the balance of the model is.

Originally Posted by Andy from Sandy

Pete take a look at page 34 of the manual. This is the preferred way to be totally sure of how the balance of the model is.

Yeah I've tried that, but I dont get it. If I hold the heli like that it just spins all the way around until the tail points the other way :S

If you have the motor pinion meshed then the model will hold against the one way bearing as the motor will not turn. You might find it easier if you pull the motor back so the pinion is not meshed. When you held the model up did it turn nose down or tail down? Which ever way it went then that was the heavy end.

Originally Posted by robgt

If the tail kicks to the right (with the tail pointing at you), lower the pitch precomp by 2 points and try again. if it kicks left, increase if by 2 points and try again.



This is likely to be CofG balance. Alternatively, it could be that your swashplate is not perfectly level?



As long as nothing is bent on the model, this could simply be that your swashplate gain is a little low. Take the swashplate gain up until you see an oscillation on the swash when hovering, then drop it down a few percent and fly it. If it still oscillates in harder manoeuvres, just drop it a little more. You should run the swash gain as high as you can for the best feel in flight.

It's good to be picky - all of these things can be resolved on the VBar, it's awesome
Cheers,
Rob

I'm no Vbar expert so please correct me if I'm wrong.

1. if the tail moves to the right on pitch pumps then surely you need to increase the pitch precompensation? Also make sure your gain is set properly first.

3. Dont you want to lower the gain if this is happening as it implies the gain is too high resulting in the nodding just like a tail can sometimes Wag in FF if the gain is too high.

Once again I may be wrong as I have no experience with Vbar only BeastX

Hope this helps

Brett

Originally Posted by Andy from Sandy

If you have the motor pinion meshed then the model will hold against the one way bearing as the motor will not turn. You might find it easier if you pull the motor back so the pinion is not meshed. When you held the model up did it turn nose down or tail down? Which ever way it went then that was the heavy end.

If I do the test that way the heli would apear to be nose heavy I think, but then if it was nose heavy and I held it with the nose straight down I'd expect it to stay that way, but it doesn't. But if I pick the heli up by the grips with them at 90deg to the heli, it balances spot on confused...