RE: engine thrust angle
 

1) I realise that there is no such diffrece between 2.9 to 3.8 degree since i was needed the same right rudder trim on uplines.
2) The plan dosen't fly straight and level without right rudder trim. it pulls to the left.

any ideas ?

RE: engine thrust angle
 

So the problem here is not right thrust IMHO. As I said previously, I would FIRST trim it in straight and level flight. Trim in this condition, don't worry about rudder trim left or right - just make sure the plane flies straight in this condition. You may end up with a little bit of trim to fly straight, but if you have to put a large amount of trim this means that the plane is crooked.

Trim the plane with at least half throttle, if you are too slow the trim effect will decrease and the thrust effect will increase.

RE: engine thrust angle
 

with 3 degree of right thrust i will need additional of ~ 5-7 degree of right rudder trim in order to fly straight above half throttle , but i want to eliminate it so the airplane will fly staright on low rpm.

RE: engine thrust angle
 

i am not sure if it's 5-7 degree i need to measure it.. but let's say that it's at least 3-4 degrees.

RE: engine thrust angle
 

Ok, first up that doesn't sound like the correct prop for that engine.
Presuming you're using a decent amount of nitro as normal with YS, I'd guess you'd be needing a 14x10-12.

Next, if you're not trimmed to fly straight and level, it's pointless trimming vertical.
You must find out whats needed to maintain level flight.
On a nice still evening, start observing the plane and see how much rudder trim is needed to keep a straight line.
Fly over your head and straight away from you and just leave the plane to fly, hands off.
Don't touch it for several seconds. Keep doing this... adding a little rudder trim until you can fly from horizon to horizon... in a straight line without any input.
Just because you a have an ARTF doesn't mean it's built straight, in fact quite the opposite.
Use rudder trim, not a mix, to sort this out.
Then, trim for vertical using right thrust.
You won't be needing any rudder throttle mix.

RE: engine thrust angle
 

Hello,
right thrust plays a minor role in this case, it's not your problem.

First you have to trim your plane for hand-off flight. Follow the suggestions that David gave you. Forget right thrust now, if you have your rudder off to keep the plane straight, the plane is crooked - right thrust will not help here.

Do what David suggested you and only after go to the uplines & right thrust.

RE: engine thrust angle
 

Hi,
I am not sure i understand that.

since i need ~4 right rudder trim in order to fly straight is that mean that my airplane crooked ? if so is there way to fix it ?

as i said before i am able to fly straight hands off ( above half throttle ) with about 3-4 degrees of right rudder trim, and also the up lines are straight with the exact rudder trim.

my concern is that i still need ~4 degrees of right rudder trim for the up lines although i already have 3.8 degrees of right thrust !

i thought about the rudder throttle mix for the low throttle position.

about the prop issue i can't get the 9500 rpm with 14x10 that's the reason i am using 14x8 ( we have very hot and high humidity climate here )



thanks,

RE: engine thrust angle
 

Hello,
yes you are understanding correctly.

Ideally the rudder should be centered to perform a straight flight, but no plane is perfect - plus there are many disturbing effects of the propeller and so on.

So a little bit off is normal IMHO, I would not be concerned about that - at least if it is a small amount. I don't think you can fix this, perhaps the fuselage is not 100% straight - but again it can have a minor effect.

So if you have straight lines and uplines you are trimmed your plane IMHO - at least regarding the yaw axis.

Check if the plane flies straight even with low throttle: if so your ok, of not you can fix it with a little of mix as you thought.

Let us know how it goes!

But the po

RE: engine thrust angle
 

Thanks this is very helpful.
I will check that and let you know.

RE: engine thrust angle
 

OK, I understand the prop situation.
Yeap, the plane may not be build quite straight, it's as simple as that.
And believe me it doesn't take much to screw things up.

You've got 3degs(ish) on the engine so that a good start.
Now, Just trim (not mix) the rudder for straight flight, what ever it takes and just leave it there.
Then trim/fine tune the vertical with +&- right thrust.
You should be able to solve the problem.

Starting adding a throttle-rudder mix into the equation is going to confuse the issue even more at this point.
Leave that for a different day.
Just stick to the plain simple/obvious fixes first.

RE: engine thrust angle
 

Have you checked lateral balance? Is the left wing heavy? OR, Is there a warp in the wings?

RE: engine thrust angle
 

Hi,
The wings are balanced, about "warp in the wings" i quiet sure it's ok and if there was some then i guess there was other affect then except of rudder trim issue is that so ?

RE: engine thrust angle
 

Yes, a wing warp and balancing would affect roll axis, not yaw one IMHO.

RE: engine thrust angle
 

Unless the warp was causing significantly more drag on one side.