After reading all the "flutter" threads, and being the proud owner of a NEW ARC (uncovered) DP Extra, I had a great chance to take a look at all the suggested trouble areas. A couple of things seemed obvious, so I built them in....I'll have photos later.

Basically, I installed additional ribs in all the aileron bays at angles from the LE of one aileron rib, to the TE of the adjacent one. On adjacent bays, I reversed where they started from, so there are ribs going in both 45 angles from LE to TE (hard to picture, I know). Anyway - twisting the uncovered ailerons by hand seemed to reflect that these ribs made it a lot more rigid. And added .1 oz per aileron.

In the wing, it seemed the ply plate that the aileron servo bolts to in the wing had a lot of flex, so I put a 1/8" x 1/4" spruce longeron on edge from the spar to the trailing edge, gluing it to the ply plate in the wing. THAT made the ply plate MUCH stronger, and I doubt they'll oscillate under load now.

Here's the spruce piece..

Just what I had in mind after looking at my ailerons too!! Great work... thanks for the pictures.

Well Bob, every time I think I'm ready to fly this plane, something stops me out of worry that I'm going to blow up this "now controversial" airplane. Today was to be the maiden flight and it is windy in AZ. Pulled out the razor blade and took off my bottom aileron covering like you. I found from another thread (dual aileron servo mod) that there are two versions of the ailerons out there. One has the diagonal ribs and the other doesn't. Mine doesn't so maybe my version is the problem child. I found that a lot of glue holds the trailing edge sheeting together possibly pushing the aileron CG back to extremes. I noticed that there are upper and lower spars along the front sheeting and a nice place to glue vertical grain shear webbing to make a nice spar box in the LE (helps CG too). That webbing surface makes a nice face for the addition diagonal ribs. I think I will also add a corner gusset (like the cap strips)over the diag. ribs and see if that helps. The aileron sure becomes flexible when the covering is removed. One day I'm gonna fly the hell out of this thing.
Jack

Humor, Jack...have to smile or we'll cry, no?? I have to say that after covering the ailerons, the diag ribs I added seemed to add a great deal of stiffness. Mounted up, with radio on, there is very little twist, and CERTAINLY no more than my pattern airplanes and the GP Pitts, so I'm feeling okay with what I have.

Putting the final colors on the cowl, then the motor will arrive next week, (Taurus T-52), and she'll be ready. I have all the radio stuff complete; used CF rods with 4-40 ball links EVERYWHERE, and the controls are sure solid. JR 8231's on Elevators, the high-torque GMS servos (2 bb, metal-geared, 110 in/oz coreless) on the ailerons, and a JR 8411 on the rudder.

The all up weight - 15.2 lbs on digital scales. Should be interesting.

Hope SOMEBODY gets to fly one of these with the aileron mods soon....I DON'T "believe" in the dual-aileron configuration.

Bob, as I modified the ailerons and flexed them before/after and I finally came to the realization that the right aileron was whimpier than the left one to begin with. I felt/squeezed around some (on the aileron) and finally saw the difference. The top and bottom LE sheeting up to the cap strips on the weak aileron was 1/16" soft stock. The rigid aileron had 3/32" hard stock. As a matter of fact the soft stock was cracked near the hard-point section. So ailerons are done, the good aileron feels like it did to start with. I cut away the lightning hole in the ply servo mount to add a stiffener like you and as I'm sealing down the edges before cut-away I notice that the rear area near the trailing edge is not only loose as we've all noticed but it's missing glue at the rear butt joint to the trailing edge sheet which is the same 1/16" X 3/8" stock found on the aileron. All that thin ply is merely butt glued to the light balsa edge sheet stock. Better add some overlapping stock there too. 2 Oz of high torque servo at hi-G's and a 1/16" butt joint? Guess the ribs are the only support. Now I can say we have 2 different stock aileron rib configurations and 2 different sheeting configurations on top that.

jelaird - it sounds like the longer we look, the more we find. Sorta like why a lot of pilots just ask the crew chief "Is it ready?" then go....

Sometimes too much information can be a bad thing......

There must be two assembly lines - one for the left panels, one for the right...who knows?

Aerobob, you are right. The longer I looked, the more I found that "could be done". That's why I installed the second servo and was finished with it. If one doesn't have the extra servos, go ahead and try to beat the problem with stiffeners. I don't have a lot of time and decided to attack the problem with the additional servos. I initially beefed up the factory servo rib bays and that didn't help a bit.

Good luck to all !

JW

I should be finished converting my second wing for dual servos tomorrow evening. Then I move on to doing something about the extremely screwy canopy deal.

Has anyone received the instrument panels? I ordered them along with the airplane a month ago and I still haven't received them. Of course any "illusion" from the instrument panels is going to be totally ruined with no cockpit floor, and not even something to cover the giant gaping opening at the front of the turtledeck.....

Many ARFS have horrible aileron design.
The lightest/quickest /most effective fix -for me --has been to strip the ailerons -then make sure they are straight - then add diagonals along the surface - that is - even with the covering.
1/8" sq spruce will work - or make ribs -in each diagonal and cap and sand flush- How it's done is of little import.
The covering will grab each one and make tiny torque boxes along the surface - You will see this when you try to twist them.
Finally lighten the AFT portion of the aileron as much as possible -that is from center to trailing edge.

The object is to make the aileron CG move forward--
Insure the control linkage is stiff.
I fly big ailerons on 33% models with one servo - no problems using this technique.
On this size model a servo such as JR's new 811 digital should work fine.
I put them on my new 1230"sq in model.

RCU: Did you cut into the ailerons to add some reinforcement where you installed the additional control horns? There didn't seem to be too much "meat" in there for the screws when I installed the additional control horns. The aftmost screws appear to only be going through some balsa sheeting....

I did add a strip of ply that reached from the leading edge of the aileron to the trailing edge in that area. That's what the control horn was attached to.

JW

Dick, you make a lot of sense there. An improvement to structural integrity that also shifts the CG forward....Hmmmm..... The CG removes flutter completely, the added structure lets me throw more control surface at higher airpeeds without failure......
Jack