Author Topic: Gaudius screwing out of loops  (Read 1835 times)

Offline Lee Backrath

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Gaudius screwing out of loops
« on: 13, July 2016, 07:10:30 AM »
For the past month I have been having problems with plane wandering in any kind of loops.Everything on plane is square, no warps of wing, stab etc. Elevator is a one servo set up and both halves now move exactly together . All checks have been done with a digital gauge to 0.1 of a degree. When trimmed for straight and level at cruise speed then landed aileron trims are exactly neutral and a just noticeable bit of right rudder. If I do a right thrust test vertically the plane is suggesting it needs a tiny amount more right thrust, but if I fly away from myself into wind upright and pull into a loop the plane drifts badly right. Away from myself inverted and push into an outside loop and plane goes to my left.All static balancing is ok, have tried wing drop test and when rolled inverted neither wing drops. Cg is where I flew it Last year( slightly nose heavy) .Plane has recently been transferred to new radio but every setting was copied by degrees including an mixing effects.Plane initially flew well and after a dozen flights the issue showed up. The current right thrust is 3 degrees. Is it possible the slight lack of right thrust and subsequent right trim(app. 1 click) could cause this.Lots of adjustments have now been changed and changed back etc. But nothing seems to improve it.Have even tried a new rudder servo with no effect.Any help appreciated because I am fast running out of time and certainly out of ideas. May just have to try a throttle to rudder mix for now as comp is on Sunday. Thanks.
« Last Edit: 13, July 2016, 07:27:17 AM by Lee Backrath »

Offline Alan Wild

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Re: Gaudius screwing out of loops
« Reply #1 on: 13, July 2016, 08:42:44 AM »
Might be worth trying a bit of L wingtip weight?
Even though you say the static balance is OK----if you imagine a slightly heavy R wing, it will tend to wander right on an upright pull---and the R tip will be on the left if you push from inverted flying away from yourself(as you said)--and you will see a turn to the left (as you said).
Otherwise, such wanderings can usually be made at least less severe, if not cured, with an elevator to aileron mix---just pull multiple loops with some aileron mix in until you get the best compromise loop staying in the same lateral plane, and again whilst pushing multiple outside loops----usually the  most obvious flaw, I think.
Again though, a perfect vertical climb with no yaw, pitch , or roll, is a good place to start from----whether by thrust adjustment (my preference) or Rudder to whatever mix.


Offline Pittsartist

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Re: Gaudius screwing out of loops
« Reply #2 on: 13, July 2016, 08:53:20 AM »
Hello Lee.


That combination of Right roll on a "pull" and left on a "push" is well known in full size aeros. No matter how much you think you are pulling / pushing straight having an arm attached to one side (the Right) of your body makes it more probable that you pull slightly to the right and push slightly to the left - particularly if you are concentrating hard on something else at the time.


Get someone to look over your shoulder at the sticks next time you do the test


The second thing is that the gyroscopic forces of a anti clockwise (as seen from the front) prop cause right yaw when pitching up and left yaw when pitching down - particularly at low speeds / high throttle settings.


If "gyro" is giving you a problem it would be more evident in smaller, higher powered, slower speed test loops.

« Last Edit: 13, July 2016, 02:00:30 PM by Pittsartist »

Offline Mike Wood

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Re: Gaudius screwing out of loops
« Reply #3 on: 13, July 2016, 11:01:01 AM »
You may be doing this already but to further check that the right thrust is ok you could:

From level flight, pull to vertical and open up the motor, just after the model hits vertical, correct any deviance to the left or
right with the rudder, then watch the model continue up the vertical, where it should remain on track.

If you're already checking it like this then, super!

As Pittsartist mentioned, there is a possibility of leaning on the stick, so if you currently pinch the stick
with your fingers or have your thumb on top you could try pulling back and pushing forward on the stick
from level (inverted as needed :-)  ) by just using a finger out straight, in line with the top of the transmitter, to
try and avoid any slight leaning on the stick, one can try this out on the ground first.

One last thought is to use the servo display, on your transmitter (if it has one) to check for the possibility
of some mixing that is in there that shouldn't be, one can hold both sticks in various corners and then click all the
switches to all positions, with the sticks in the corner and see if anything unexpected shows up. It's unlikely this
is the issue but just another check to make sure nothing unexpected shows up.

Mike
« Last Edit: 13, July 2016, 11:10:35 AM by Mike Wood »

Offline Lee Backrath

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Re: Gaudius screwing out of loops
« Reply #4 on: 13, July 2016, 12:57:47 PM »
Thanks for the quick reply's gents.I have tried very large expos to rule out my thumbs wandering so don't think its that. I have checked for any inadvertent mixes and all seems ok.The gyro effect has always been noticeable at the end of a vertical especially when you push to upright so have got used to feeding in a bit of rudder. Also it veers of in big smooth loops where the effect should be less.The strange thing is how it flew ok one day then terrible the next. If I can get out after work tonight I'll try getting the right thrust spot on and try adding weight to left wing. If no improvement will try the mixing to improve it for Sunday and start scratching my head again next week.As you know every change needs test flying which can be time consuming and very frustrating with the British weather.Thanks again for the advice. Lee

Offline Mike Wood

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Re: Gaudius screwing out of loops
« Reply #5 on: 13, July 2016, 03:05:51 PM »
I know it's been said before but just change one thing at a time  8)

Another thing to try is just hold it in continuous loops, inside and then outside.

Force it into tracking correctly by holding in any corrections but keep elevator and if possible throttle constant,
try not to move the sticks.

Once it is in the loops and corrected, see what you are holding on aileron, release the aileron and see what happens and
repeat a lot  ;D and try the same with outside loops.

Then try the loops at different throttle setting, 1/2, 3/4, full and note the results.

Also double check both elevator halves are moving with identical movement and throw.

If you need say right aileron to hold it in the loops when upright and left aileron when inverted, try adding weight to the starboard (right)
wing and vice versa.

If you need to hold the same aileron for both upright and inverted, say you're holding right aileron, try lowering the left aileron a turn
and vice versa.

Good luck!!!!!

Mike
« Last Edit: 13, July 2016, 03:07:52 PM by Mike Wood »

Offline Alan Wild

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Re: Gaudius screwing out of loops
« Reply #6 on: 13, July 2016, 03:22:07 PM »
(Yet) another check:
The Gaudius has integral top hinged ailerons and elevators doesn't it?
Check if there any little splits anywhere---and if you have sealed the bottom gaps in any way (to stop that whistle)---check that the seal isn't coming away at any point---I had trim issues when my gap sealing wasn't 100% secure along the length of an aileron, from memory.

Offline Lee Backrath

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Re: Gaudius screwing out of loops
« Reply #7 on: 13, July 2016, 10:14:16 PM »
Managed to get out tonight and try a few things. The sidethrust test definitely indicates more needed even though I've got 3°. When I increased it before I set it at 4° and that was too much so will have to try and get it set right when I've got the time. Tonight at the field I set the rudder to fly straight power off and added a mix of just 1% right rudder at high throttle. I also upped all expos . The verticals were pretty good. The wind was a bit too turbulent for any proper trimmng so decided to just have a go at the schedule and focus on flying the plane adding corrections when and were needed instead of analysing what it was doing. Later on the wind smoothed out a bit and the plane flew well. I had tried both of those things before but I don't think I had flown it with both changes together. Possibly a case of not seeing the wood for the trees. Anyway hopefully get out tomorrow with better winds forecast and see if the improvement remains. Thanks again everyone for the help.

Offline Peter Jenkins

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Re: Gaudius screwing out of loops
« Reply #8 on: 14, July 2016, 10:11:02 AM »
Hi Lee, do you fly holding the Tx and using thumbs?  As has been said earlier it's always possible to introduce a touch of aileron when pulling or pushing.  I went from a neckstrap to tray (it took me 3 months to get used to flying with thumb and forefinger!) but that improved my flying significantly.  It's definitely worth trying if you are not already using a tray.


Peter

Offline Mike Wood

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Re: Gaudius screwing out of loops
« Reply #9 on: 14, July 2016, 11:51:29 AM »
I agree with Peter, but each to their own.

I started with just thumbs, then thumb and finger with a neck strap and then on to a tray.

I found I didn't get on with a tray that meant I couldn't get to the sides of the transmitter, where the tray
is level with the top of the transmitter. You can get "flat plate" type trays or modify an existing design.

Last time I looked CPLR pinches the sticks, while Chip Hyde just uses thumbs and I don't think he uses a tray, it's
whatever works for you, but definitely worth giving it a go, perhaps you could borrow something to try?

It used to be said the Mode 1 had an advantage over mode 2 with several top flyers using it, but I think that has long
been put to bed ( or has it  ??? ).

Mike
« Last Edit: 14, July 2016, 11:53:05 AM by Mike Wood »

Offline Stuart Mellor

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Re: Gaudius screwing out of loops
« Reply #10 on: 15, August 2016, 04:54:41 PM »
Hi Lee,

Saw your Gaudius at Ashborne yesterday. Must say it flew well - once you tamed the throttle! I found the Gaudius to be a very slippy model, in spite of an apparently big fuz. (Only realised yesterday  - your Gaudius was the one I built a few years ago!). Nice to see it surviving.

Read most of your comments above. One major thing to try is to slow down the 'natural' flying speed of the model - to give you more time to think & react. Speed won't cost you points as such - but the model will quickly accelerate into big trouble at the slightest trimming problem or mistake on your part.

The Axi 5324 & 20x13 is a good combination for the Gaudius -but it likes to rev -so I would consider perhaps reducing pitch/increasing diameter to slow the model. This would also improve the downlegs & may have an effect on accuracy of up lines. Worth a try.

Also I think I used a single Y elevator pushrod. (An old fashioned approach but superior, I think to separate ele servos, where much time is spent trying to achieve what a single pushrod achieves as standard) (which is why CPLR used it for years) BUT - have you tried bending an elevator? & see if the other moves in unison. It should -if no sideways slop has developed in the pushrod.

Offline Bob Wasson

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Re: Gaudius screwing out of loops
« Reply #11 on: 15, August 2016, 07:01:17 PM »
Hello Lee,

The Gaudius is an excellent aeroplane.  The mouldings that it is produced from are highly accurate and set up correctly it will not screw out of loops!


On mine, I have 2 mini servos on elevator duty and they work extremely well.  As Stuart says, it is very important to check that both elevator halves have identical throws.  With 2 mini servos, unequal throws are a very common cause of the problem you describe.  It is vital to check for identical travel with a throw meter.  A good clinometer app on a mobile phone will also work well.  It’s worth paying £1.50 or so for the version that you can calibrate rather than the free version.


My Gaudius is powered by an Axi 5325/24 fed from Zippy Compact 10S 5000 mAh batteries and a Jeti 99 Speed Controller.  Although a 20x13 is the propeller most commonly recommended for the motor, it is entirely the wrong choice for the Gaudius.  As Stuart observes, it makes the model far too fast and slippery.  A wide bladed Mejzlik 20.5x12WE will transform the model, slowing it down on the downlines and making overall speed control much easier.  Don’t worry about the loading on the motor.  With good throttle control, 5000 mAh batteries will have more than enough capacity to fly any of the current F3A Schedules.  The Mejzlik is not a cheap propeller, but it is more than worth it for the difference it makes in the models performance.  Best place to buy one is from Mejzlik’s on line store.


If you want to get good control of speed on downlines, the right brake settings on the Jeti 99 are also very important.  I set mine up for manual brake, 0.2 secs dead time, 16% initial brake, 34% end brake and 0.5 secs brake time.


The correct motor side and down thrust setting are also important for a true flying model.  As luck (or a fastidious approach by the designer) would have it, the amounts moulded in to the front of the fuselage seem to work perfectly with the Mejzlick 20.5 x 12WE!


Hope this helps


Bob Wasson
« Last Edit: 15, August 2016, 07:05:07 PM by Bob Wasson »

Offline Lee Backrath

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Re: Gaudius screwing out of loops
« Reply #12 on: 15, August 2016, 09:19:05 PM »
Hi Stuart and Bob. Thanks for comments and advice. When I first got the gaudius I did use the brake but turned it off apart from the landing mode for some reason I can't even remember now! I have actually been out tonight and reinstated the brake and it improved everything. For example without the brake at the start of the second loop of the eyecatcher the plane wood accelerate around the bottom half making control harder. Tried it with the brake back on and the improvement was very noticeable , although still needs more braking so will definitely look at your suggested settings and prop recommendation Bob. Les also suggested to try a lesser pitch prop yesterday at ashbourne. Regards the elevator servo, it is still on one servo and they were a little bit out but have now  got both moving completely in unison. I think I will try to get the speed better with different prop and break settings and then recheck thrust lnes with the new prop. The excessive speed definitely makes it harder to control out of the bottom of loops so hopefully if I can get the speed more constant it should help in many ways. Again thanks to both of you for taking the time to help. Lee.

Offline Mike Wood

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Re: Gaudius screwing out of loops
« Reply #13 on: 16, August 2016, 01:29:32 PM »
Bob

Thanks for sharing your settings and set up.

Mike