RC India

Hi!

Recently started flying a SkySurfer and am throughly enjoying the same. However I realise that despite the rudder working well - the plane does not respond and I need to use the ailerons to turn the plane.

Can anything be done to improve on the performance of my plane?


Looking forward to your comments on this

ATK

Please do not bad mouth a good design.
Design fault, eh? Whoever told you this, how many successful models has he designed?
I’m not posting the full answer here, as it may offend you.

If really interested, PM me.
I’ll answer privately or publicly, as you wish.
Regards

@adel,
To avoid being sued by the owner of RCBazaar, I suggest you remove the word ‘unsatisfactory’ from the title bar.
Regards

Tried increasing the throws?

Good to hear from you!

I am using TowerPro MG 90 servos. I have also increased the throw of my rudder servo to the maximum on my transmitter. Besides this I have also made the foam hinge flexible. Can upload a video of this if that helps.

Try checking the rates and expo on your Tx. Reduce Expo on Rudder to 0

Thanks for your advise. Done as you suggested.

I am keen to know how the response of the rudder could be increased?  

Looking forward to your hear from you!

The expo is 0 on my transmitter for the rudder and the dual rate is 100.

Then I can't help unless I actually see the model. I've flown a Sky Surfer - the rudder response was fine. Not a design issue - something else is wrong

Would a video of the the servo and the the rudder moving help in identifying the problem?

I have a skysurfer for a long time now... i don't see any problem with the Rudder it responds perfectly.
Guess it can be a servo throw issue.
 

Which servo do you use?

Post the video. You might be using the wrong holes in the servo arm and getting less throw. Or your pushrod may be flexing under load

@adel

After all the servo, linkage, throw etc, let’s look at the basics.

I wondered if you were flying without ailerons, depending on rudder alone. But a look atyour first post clarified that you have ailerons.

Rudder alone can only initiate a YAW, not a turn.

A TURN requires the wings to be banked. Then the lift vector has a horizontal component that causes the change of direction of the flight path. The easiest way to bank is by using ailerons.

If ailerons are not there, dihedral is needed. The rudder yaws the model, so the outer wing gets an upward lift, leading to roll, and then to the turn.

Usually an aileron equipped model will have less dihedral than required for initiating a strong turn with rudder alone.

In such models, the rudder is usually used for steering during takeoff, And in crosswind landing.
Turns are done with ailerons (with a touch of up elevator or throttle)

My 64” Sunbird doesn’t have ailerons, though designed to have them.
It turns just fine with rudder, because I increased the dihedral

So my suggestion is to use the ailerons to turn, and forget the rudder except for crosswind landing.

There are of course more issues involved, like coordinated turns, adverse yaw etc, which can be gone into if required...

Hope this is of some help.

Regards

Many thanks for your detailed reply.

I have read it carefully and do understand the point that you are making. Have been using ailerons to turn. Whenever I attempted to use only the rudder I did not manage to turn the airplane. Now I understand why this was not happening. However I still feel that the throw could be an issue. But I do not know how to increase the same. Would be uploading a video of the same asap.

@adel,

I don’t understand why the preference for rudder when you have ailerons.

An easy way to increase the rudder power is to increase it’s area by adding some plastic sheet or depron.
But this will only increase the yaw, an inefficient way to turn.

A powerful rudder may be needed only for knife edge flight, or super quick snap rolls, neither of which is part of the Skysurfer’s intended flight envelope.

But then, to each his own...

Thanks for your reply.

I wonder why I am unable to post a video in this thread. When I click on add file it does not respond.

As I could not post the videos here have sent them to you on email.

Would be grateful if you could have a look and see

thanks

Adel

Hope you don't mind; I took the liberty of uploading to YouTube and posting here for a wider reach

https://youtu.be/l10qxstQXU4

https://youtu.be/z5D_WjPQnJs

My comments:
1. Rudder movement is more on one side (right). Correct this
2. The throws are too low
3. Move the Z bend on the Rudder end more inboard - i.e. closer to the rudder. This will increase the throw

The throw should be more than 30 mm in each direction

To post a video on RCI, you have to convert to  YouTube

I can't make out clearly, but the rudder pushrod seems to be bending

Firstly correct the pushrod bending. Use a stiffer rod

After that if the rudder movement is unequal, check the servo

Which mm pushrod should I use?

More than 2 mm won't fit in the linkage stopper. What's important is the stiffness

Use spring steel if you can

Yes, Also it needs to pass through the silicon tube that came with the airplane.

Any ideas from where one could get spring steel that would work?

I maybe a bit inexperienced when it comes to sky surfers but I think another reason why the pushrod is bending so much is because of the linkage stopper. Consider using a z bend if possible.

Regards

Why would a linkage stopper make a pushrod bend?  :D

Try from a manufacturer of springs. He'll probably give you a small length free. Worst case use a 2 mm cycle spoke - but that's not very hard

The rudder performance dramatically increased after I put the pushrod through the hole nearest to the rudder. I did the same to the elevator too. Tomorrow I shall check the difference when I fly the same.

Further I checked and found that Robu was selling pushrods: https://robu.in/product/d1-2x840mm-z-type-push-pull-steel-rod-for-rc-aircraft-aero-modelling-2pcs/

Wonder if this is what you are talking about.

Further how different this would be from the rod that came with the airplane?

Be careful about increasing the elevator throws! If the plane is flying OK, leave them. Otherwise you might go out of control

The Robu pushrods "read" good. Haven't used, so can't really comment. They are 1.2 mm diameter. But if hardened spring steel, should be OK. Can't comment on the original pushrods - may be 1 mm SS

This may be a better choice - if the length is acceptable, and will fit in the Linkage Stopper

https://robu.in/product/d1-5x120mm-z-type-push-pull-steel-rod-for-rc-aircraft-aero-modelling-2pcs/

@adel,

A few suggestions:

1. Check if the linkage stopper is free to rotate on the servo arm. In your case it doesn’t seem to be. Enlarge the hole in the servo arm very slightly, so that the linkage stopper can rotate a bit. If necessary, unscrew the bottom nut a few degrees. This will prevent the flexing of the pushrod near the servo.

2. Make sure the sleeve through which the pushrod passes is anchored at 2-3 points. That will prevent flex along the length of the pushrod.

3. Remember that (except in 3d) very little control deflection is reqd for smooth flying.

@Mr Iyer

1: My linkage stopper is fixed to the servo arm. In fact I used epoxy to fix it 'proper and tight'! I did this as the nut below kept falling off. If the linkage stopper needs to be free to rotate (that means a bigger hole) I wonder how would it stay connected to the servo arm without the nut below not being full tightened?

2: I fixed the sleeve well and proper to the carbon fibre rod passing through the fuselage. Now that it is fully sealed I many a times wonder what if I ever need to have access to the inside for some job the kinds that you mention above.

Many thanks once again for your inputs. I have learnt a lot from the same!

Or a drop of cyano (super glue)

The linkage stopper MUST be free to rotate! Look at the geometry when the servo arm rotates

Thanks. I understand your point. Shall order some linkage stoppers and connect them as you suggest.

Why do you need new linkage stoppers?