Gremlin Castle

My Feedback: (14)

Just checked the link and it seems to be fine.
Try full aileron deflection at about 90 kts and get back to me.

CrateCruncher

My Feedback: (1)

Tod0001,
Can you tell us more about these two planes? You say they were EXACTLY the same? Was there ANYTHING different?
How about the engine? Same?
Did you build both? From a Sig kit?
Is there a possibilty someone modified the ailerons or span on the earlier plane?
You say one revolution takes 5 seconds flying your current plane. How fast was a revolution in the old plane?

tod0001

Both are the bult from the Sig kits, both powered by a Saito .65.
I flew the first one for about 5 years.
It would roll as fast as I ever wanted. Maybe 1 revolution per 1-2 seconds, enough for me to have both high and low rates.

CrateCruncher

My Feedback: (1)

When someone earlier mentioned sealing the ailerons you said you couldn't get to the gap. Most barn-door style hinges have a hinge point near the upper surface of the wing so if you disconnect the linkage at the horn you can rotate the aileron up 90-180 degrees. If so you should be able to iron a strip of monokote across the gap (Even using a strip of masking tape will suffice for a quick test flight). If you can see any visible space at all in your aileron gap currently, sealing that gap will grant a noticeable improvement in roll performance. Its a 10 minute fix if you can rotate the ailerons forward as I described.

I agree BTW, a 5 second revolution is pretty sluggish. You aught to be able to do better.

da Rock

tod001,
Keep in mind that none of us "advisers" actually know why your model rolls so slowly. Lots of things mentioned that might be the cause. And none of them really stand out as the probable cause.
Good thing about model airplanes is most things can be tried without risking a test pilot's life.

Let's see if we can list what's been suggested:

Failing servo
too weak servo
too tight pushrod system
too loose pushrod system
pushrod system flexing (gives under load)
(hey one of the tests mentioned earlier will test all of the above quickly and simply........ hold an aileron while moving your TX stick)
and adverse yaw

Anybody got any more ideas?

tod0001

Have not sealed hingeline yet.
Normally only seal the gaps on my fast airplanes, bad practice I know...

CrateCruncher

My Feedback: (1)

Tod0001,
The slower planes are even more sensitive to gap leaks than the fast ones. Slow planes deflect less air mass/time so they generate less torque. Da Rocks right. None of us know whats wrong with your airplane. But there's some low hanging fruit to pick before doing major surgery. That aileron test he suggested will eliminate a lot of possibilities. With the aileron at full deflection try to push it back to neutral with about 5 pounds of force. You should hear the servo strain but the aileron should remain firm and not relent to the force of your hand.

PacificNWSkyPilot

My Feedback: (19)

I wrote this in an earlier post:

Here is how I was taught to make the differential many years ago. Now, this is for a high-wing setup where the servo is UNDER the wing. The linkage arms are in the center and behind the servo, but you'll be able to make it work for your setup once you understand it.

We used a CIRCLE servo arm on a single servo. Consider the FRONT of the wing to be 12 O'Clock, the bottom to be 6 O'Clock. With the ailerons centered with the wing, bring the linkages off of the 2 O'Clock and the 10 O'Clock positions on the circle arm.

When the ailerons are run they will automatically have differential in them, the UP will be more than the DOWN due to the fact that the linkage goes mostly sideways going around the clock from 2 to 10:30 when pulling the aileron DOWN, giving less travel. Going from 2 to 5:30 you get a straight push UP and substantially more travel to the aileron. Thus, you have differential.

If you were running a low wing with the servo on TOP, then you'd use the 4 and 8 O'Clock positions. (That's not your setup, though.)

I just read Da Rock's post, mised it the first time. His is the formula to make your setup work right. I'd go 2 and 8, but 1:30 and 7:30 is certainly close enough to the same thing, you get the idea. Just make sure that the aileron goes DOWN less than it goes UP. Work out that motion before you cut it up.

Hope this helps.

CrateCruncher

My Feedback: (1)

Double post. Sorry. Plz delete.

tod0001

Excellent, excellent help guys...
Bellcranks are known for less than very rigid setup.
This is an "old-school" design with these bellcranks and no reinforcement is present to it's music-wire to bell-crank setup.
Having flown this same setup alot in the old airframe, it feels firm enough, holds 5lbs of finger pressure and the servo has only maybe 2hrs on it( This plane it's self has only had maybe 10 flights thus far.).

I have not, in flight testing, pulled vertical and checked roll-rate with diminishing speed/air-resistance.
I have not sealed hinge-line and flight tested.

I will flight-test those on Sunday( I gotta first finish at least one hatch that I started on top of a bellcrank.).

I do have experience about lightcraft/ general aviation types and flutter.
Years ago while coming out of a Hammerhead, facing pretty much down( already back on the upswing) over trees in my ole' GB Cub, elevator flutter struck! Load, hard buzzing sound, no elevator, pointing down, runnning out of time/space and I mentioned no elevator control...
Luckily, at first instant of noise, I cut throttle. The old 12-5W prop(Saito 50 here) at idle acted like a nice air-brake, slowing me down fast and happy ending of story, flutter stopped, elevator control was regained just in the nick of time and I landed to reinforce said linkage....

PacificNWSkyPilot

My Feedback: (19)

You can do everything you listed above, but if you don't go with some differential it'll all be pretty much for nothing. Those things will help a little, but not if the basics are not in place, and the differential is what I'm referring to as the basics.

I can't even believe I've been arguing with a guy here who actually believes that differential isn't important, when it's the MOST important thing of all.

Just goes to show why we need insurance for this with self-made geniuses rewriting the book on aeronautical engineering.

Jim

bogbeagle

Lack of torsional rigidity in the wings?

PacificNWSkyPilot

My Feedback: (19)

If you do the things you listed above WITH the addition of differential to your ailerons, they are all helpful and can even slightly improve things.

If you do the things above WITHOUT the addition of differential to your ailerons, you'll be doing very little.

I know that there is somebody here who is advocating that the differential won't help. He is WRONG.

I'm not allowed to say anything else about him or voice my opinion that he is not helping your chances to improve your plane, instead he is hurting your chances. If I make any statements to warn you of that my post will be deleted.

Just let me say that for 30 years I've been trimming planes and my planes are ALWAYS the best-trimmed, best-flying planes at any field I fly at, and I fly at many, many fields. When folks cannot get their planes to fly right, they come to me. When another flyer is having control issues, he comes to me. I'm an engineer, and physics are physics. I took courses on flight physics in school as my electives, because I've always loved planes. I ALWAYS get the model straightened out.

A Citabria or Decathlon and their related airfoils and controls are among the most basic basic types, they are aeronautical engineering 101. They are the next step in aerobatic capability beyond the Cub. I can only ask you to please believe me that with the wing you have on this model, equal throws up and down on the ailerons will adversely affect the model's ability to perform axial rolls.

RCU is a wealth of information. It's also a source of less-than-desirable information by folks who are going to have their say at any cost. Then there are those of us who ATTEMPT to mitigate such misinformation, often at the cost of having the very posts removed that are designed to save a member some grief and frustration. If we call somebody a pushy, loudmouthed idiot our posts get removed, and the guy we're trying to warn a member about goes on with impunity. This is the rule rather than the exception here. But don't give up, and use your common sense. Just because somebody is louder or more persistent than the other folks doesn't mean he's right.

I'm leaving this thread and unsubscribing because I'm VERY tempted to say exactly what I think here. In the end, I'm hoping you will have great success with your Citabria. A strong servo, good linkages and differential and it'll roll for you.

Take care!

Jim

da Rock

All right............

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