Looking for some feedback on an issue I am experiencing with a new plan.

The plane is a custom designed .60 size which is a variation of a goldberg Tiger 2. The kit was designed by a friend in Texas and he had Sig cut a few hundred kits.

The structure is well hardend for the .60 size engine and is heavier than what you would expect froma .40 size model. The ws is approximately 15% larger than than of a .40 size plane.

I am essentially ready to maiden the plane, but have noticed a vibration / flutter in the tip of the left aileron (some also in the tip of the right as well).

The root and middle portion of the ailerons do not move at all. The vibration occurs a 1/2 throttle and above.

All of the linkages are tight and the servos are new and have no slop in them.

I ntoice the issue most when the plane is on a elvated starting stand that restrains the wings and holds the plane from moving forward.

The issue is reduced (but still present when the wings are not restrained.
Looking for ideas / suggestions.

the engine is new and has only been broken in on the bench and has a total of 1.5 - 2 tanks through it (OS .61 FS ring), prop is an APC 11 x 7 (well balanced). Will the problem subside when the engine has had a few flights?

Wondering if I need to put a hardwood strip on the aileron to stiffen it or maybe carbon fiber?

Will this be an issue in the air as it seems to calm down when it is not reatrained by the wings.

Is this commen in a really stiff structure?

Radio is not the problem.

Thanks,

GB

How many hinges are in the ailerons? You possibly need to add one or more in your area of concern. Also the prop for the .61 is to small. 11x7 is recommended for breakin only by O.S. You should use one of the following: 12x6, 12x7, 12x8, 13x6, 13x7..

Could it be vibration v.s. flutter?

'GB' I would like to see a picture of your model if you have one... It sound pretty cool.

Is there a particular engine RPM at which it gets noticably worse?

It could be that the aileron (or entire wing?) has a natural frequency (of vibration) that happens to fall within the normal range the engine is running.

Inserting an extra hinge would help, or relocating the existing hinges.

Stiffening it would, of course, help also. But an extra hinge might be simplest.

Hi guys,

Thanks for the quick responses.

I have attached a few pictures of the plane here.

Here are the responses to the questions y'all raised in the thread:

1. I haven't checked the engine RPM that the vibration starts (you are correct, vibration is the most correct term). I do know it is about half throttle.

2. Hadn't thought about adding an extra hinge but that sounds like a great idea. I am using Robart pin hinges and have already 4 in each airleron but one additional on each alieron near the tip my solve this issue.

I have never added more hinges (Robart) with the aileron still attached. Has anyone done this before? Can you get the hinge to fit while the aileron is still attached?

3. Good idea on the prop, larger diamter and less RPM may fix the problem and or change any possible harmonics involved

4. Do anyone of the props mentioned seemed better suited (besides exchanging pulling power for speed) speed does not seem to be an issue in this case since the plane is significantly overpowered, even with the increased weight.

Seems like the larger diameter prop = less RPM = less vibration????

The OS is a ringed .61, does this add to any additional vibration in the engine?

Thanks

GB

Try just adding a covering hinge to the tip.

Also, a few words about vibration:

Everything will vibrate at it's given frequency. It so happens your ailreon is "Tuned" to the engines RPM at 1/2 throttle and above. Adding the extra hinge may help, but if it doesn't try adding weight to the aileron tips. This should "De-Tune" them or, more acurately, tune them to a different frequency.

Thanks for the advice.

Seen a few planes in the past with some type of weight on an aileron surface but thought that it was to make the movement of the surface require less torque than in a normal environment.

Any thoughts on placement, attachment method and amount of weight?

Thanks,

GB

For experimental purposes, I'd tape a penny or nickle to the underside of the tip. If it works, you could add it internally.

GB - If there's any significant distance between the last hinge and the aileron tip, the additional hinge might be your best bet. The simplest way would be to make a Monokote hinge. (Mike's suggestion)

Very nice looking plane! Looks like it'll be a pleasure to land. I'd like to hear about the maiden flight. Best of Luck!

If it vibrates that easily, it may also flutter. For flutter, the best weight location is ahead of the hinge line, so that ~ 80% of the weight of the aileron is balanced. You can do this by putting a small weight on something like a control horn, so that the weight is ahead of the hinge line. For plain old vibration, you may be better off stiffening the structure, rather than adding weight to damp it out. It sounds like the aileron is already a bit too flexible, or inadequately supported, & extra weight may strain the structure.