Vettster

As the tittle says...

My jet tends to waggle a lot at the top end of the throttle. By waggle I mean the tail end tends to move left to right constantly till I back off the power. Wind is not an issue as it does it on windy days as well as calm days

Its an Xcalibur Sport jet with a K100G

Dave Wilshere

The swirling eflux attaches and detaches from the booms and that makes the tail wag.
There are things you can do, but fitting an iGyro 1e is the simplest.

Dave

Vettster

Thanks Dave.. I do have an Igyro and intend to use it in the X... but wanted it for another plane first. Guess I will be ordering another

Len Todd

My friend's Excal does NOT waggle at all and there is no gyro in it. Something mechanical is not right. Flutter will tear a plane apart. Assuming these are new servos, I would start out by checking:

Servo Deadband too high? (Programmable Digital Servos?)
Inadequate servo torque?
Linkage slop?
Air gap between rudder and vert stabbs?
Inadequate servo supply voltage?
Too light of wiring harnesses causing voltage drops at servos.
High resistance harness connection(s) causing voltage drop at a servo.

For linkage, I typically use Dubro control horns and trash the OEM stuff. I use 4 x 40 linkage with CF tubing over the rods, ball links at the servo arm with 5/32 Dubro Control Horns/Links. As planes get bigger, I go up in size.

For servos I use high voltage, high torque (200 in oz+), metal geared servos run at regulated 6 VDC. 2S LiPo power source. Lower voltage = lower torque.

Good luck finding your issue. Please let us know what you find.

tp777fo

My Feedback: (28)

Wag is "dutch roll" caused by the swept wing. The faster you go the more pronounced it is. Big jets use a yaw damper to correct it and little ones can use a gyro on the rudder. I have a X+ and have not noticed any waggle. My X small did have a little but only at warp speed.

Dave Wilshere

Nothing to do with Dutch Roll. The Xcalibur plus does not do it so much as there is more distance between the booms! The Mini less so because of the much smaller high speed efflux and ratio between the boom spacing.

olnico

Dave, all the planes in the World exhibit some degree of Dutch roll if not artificially stabilized. Unless they have a very specific combination of negative swept wing/ anhedral.

"The most common mechanism of Dutch roll occurrence is a moment of yawing motion which can be caused by any number of factors. As a swept-wing aircraft yaws (to the right, for instance), the left wing becomes less-swept than the right wing in reference to the relative wind. Because of this, the left wing develops more lift than the right wing causing the aircraft to roll to the right. This motion continues until the yaw angle of the aircraft reaches the point where the vertical stabilizer effectively becomes a wind vane and reverses the yawing motion. As the aircraft yaws back to the left, the right wing then becomes less swept than the left resulting in the right wing developing more lift than the left. The aircraft then rolls to the left as the yaw angle again reaches the point where the aircraft wind-vanes back the other direction and the whole process repeats itself."

Dave Wilshere

Ok, but that is not what we are talking about here.

David Gladwin

[QUOTE=olnico;12251763]Dave, all the planes in the World exhibit some degree of Dutch roll if not artificially stabilized. Unless they have a very specific combination of negative swept wing/ anhedral

NOT true !!!

gunradd

My Feedback: (9)

I know what dutch roll is and its not what this plane does so all the dutch roll talk in this particular thread does not matter.

I have allot of time on my friend x and have not really noticed the waggle much at least not enough to be concerned about.

TimD.

My Feedback: (207)

I had this happen with a plane I designed years ago. (Weather Vanning) at high speeds. It has to do with a large vertical surface area. It only occurred at high speeds. As most have said a stabilization gyro will reduce it, or reduce the area.

Eddie P

My Feedback: (4)

The waggle might have to do with static and dynamic stability combinations. I am a little rusty on some of this so please forgive me if I'm not so eloquent. Hopefully someone with more recent knowledge on this can shed light. When an airplane is very stable in one mode and neutrally stable in another you can get oscillations that are dampened to some extent but also noticeable in some speed ranges. They may indeed be related to dutch roll but not necessarily always dutch roll per se. What they are more often referred to is a phugoid oscillation mode and they can occur in all sorts of amplitudes and frequencies. I am not saying this is exactly what is going on in this case, but often this can be seen as an issue in some regions of the flight envelope where other areas are issue free all together. Absolutely, checking flight control linkages and setups per the way Olicno recommends is always smart. But it's also possible to solve the issue with a properly tuned 3 axis gyro if all else fails.

TTRotary

Deleted - never argue with idiots, especially RCU idiots

TTRotary

Never let monkeys play with firecrackers

highhorse

My Feedback: (2)

yeah...except that it does NOT happen on most model jets or even, apparently, on the larger version of this jet. Or lower altitudes at all for the worst jet in the world for this issue (727), even with the yaw dampers turned off. And I have occasionally seen this waggle on non-swept proppies at a specific power setting for a given speed but not other power settings or at higher speeds.

So for my 2c I'd advise the OP to avoid getting too wrapped around the Dutch roll axle and go with Mr Wishire's advice.

AnthonyW

Why is everyone hate'n on the Dutch?

SECRET AGENT

My Feedback: (18)

"There's only two things I hate in this world. People who are intolerant of other people's cultures and the Dutch."

Nigel Powers

Len Todd

Now that we have all that "Dutch Roll" B.S. out of the way, one HUGE point to remember. My friend has the same plane and it does not tail waggel even at very high speeds. Time to accept the desgin and find the mechanical problem(s)!

Jetset

My Feedback: (2)

Is it possible to install some "sub fins" near the end of each boom, on the bottoms pointing down?

junglejet

My Rookie used to do it until I gave the rudders 1 degree of "toe in", problem solved.

Vettster

And this is most likely going to fix it with out a gyro I was thinking the same thing. Thanks Jinglejet

Thanks for the input guys.. To answer some of your questions.. ALL the hardware with exception of the control horns came from my Boomrang Sprint that had well over 700 flights,(never waggled) so no problem there. (the control horns are plenty strong). 180 oz servos in each aileron. 380 in the elevator. The rudder servos are only 84oz each.. the strongest I could get as a mini servo that is suggested to use.

Gaps between the control surface and wings? Hell Yeah! It was necessary to get enough movement of the surface or the plane would not roll(respond) quick enough.

I really dont feel that throwing a gyro at every problem you encounter is the way to fix things. There used to be a time when we had to investigate, learn and correct things. Im not against gyro's.. Im just sayin..

I will try JingleJet's suggestion first. Failing that..I'll add a gyro to each surface including my trailer, cause it tends to waggle at bit at high speeds on the dirt road. LOL

Thanks guys!

Len Todd

A little more weight in the front of the trailer may fix that waggle. ;-)

Vettster

Well a Big Thanks To JungleJet!! Problem is solved via moving the rudders inward. Didnt need much.. may 3mm each side from the center plane. Its not entirely gone.. but you might aswell say it is, cause she lost about 90% of the waggle.

gooseF22

encountered same issue in Elan and kingcat.. 1mm toe in worked on élan.. kingcat liked having a rudder gyro, but flew ok without. however with it, it was rock solid even with a slow old JR500.