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Thread: Pober Junior Ace Heavy Ailerons

  1. #11

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    Intentional Aileron Mis-Rigging

    "... rerigging them [ailerons] to be streamlined in flight is not going to change how they perform in flight."

    It is a common OEM procedure to intentionally "mis-rig" ailerons to account for "float" in cruise (normally with newer, more aftly loaded airfoils, though). It is also common procedure to mis-rig both ailerons up to unload the outboard wing (increase twist) or both down to load the outboard wing (decrease twist). It is more common to mis-rig ailerons up to produce better stall characteristics (inboard wing will stall before outboard wing). Rigging of ailerons should be independent of control system forces and cable tension (it's a "balanced" system). All flight controls (in this category of airplane) should move lightly and freely on the ground. As others have suggested, check the entire cable routing, you might find that a cable is rubbing or has come off a pulley. I'm looking forward to hearing what you found out at the airport :o)

  2. #12
    rwanttaja's Avatar
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    Quote Originally Posted by pacerpilot View Post
    I bought a Pober Junior Ace a while back and have found the ailerons to be very heavy in flight.
    Hmmm. To clarify, can you confirm the ailerons are heavy in flight, but not while stationary on the ground?

    If that's the case, I doubt it's a tension issue. It sounds like the leverage isn't right, or there's supposed to be balance area and there isn't. Or there is something flexing in flight, and adding a ton of friction. There was a fairly popular homebuilt ~30 years ago where the wings would flex in flight and clamp down on the aileron torque tube.

    Can you compare as-built vs. the plans to make sure all the control horns, bellcranks, etc. are correct?

    If the heavy ailerons only occur in flight, you need to simulate flight conditions on the ground while looking at it. Might be able to just lift the wingtip a bit and look close inside and see if anything is getting fouled.

    If worst comes to worst, I'd suggest adding some spades to the ailerons.

    Ron Wanttaja

  3. #13

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    Thanks for all the good suggestions and info. I've checked the cable tension, looked for interference, flexed the structure and looked for interference and, verified all the cables are on the pulleys etc. The airplane is built exactly to plan. I've been reluctant to intentionally "mis-rig" the ailerons because, as noted, that just chases the problem somewhere else. I'd still not have proper response. Just to confirm, the ailerons are only heavy in flight. The controls move freely on the ground. It takes considerable pressure to force the ailerons into their flight position on the ground. It seems to be an aerodynamice force causing the problem-and powerful one. That's why I mentioned wing wash. Are there any Pober drivers in the East Texas or Louisiana area? Maybe a comparison would shed some light.

  4. #14

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    Quote Originally Posted by pacerpilot View Post
    It seems to be an aerodynamice force causing the problem-and powerful one.
    Yes, that is true of most airfoils and you're probably losing a noticable amount of performance. But the problem is too much elasticity in your control linkage and/or not enough leverage to maintain/move the aerodynamic surface.
    Years ago I used to fly a friends Baby Ace and the ailerons were streamlined on the ground and in flight. I also don't recall them being all that heavy in flight.

    Perhaps you can email Mr. Paul for more suggestions?

  5. #15

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    Flying another Pober Jr. Ace is a good idea (or at least calling another owner and talking to him/her). Are the control horns at the stick and the ailerons the proper lengths per the plans? ... and are the throws of both the control surfaces and the control stick proper? Improper lengths will change the gearing ratio (and hence force feel). The Jr. Ace has a big, long wing, and roll inertia is high. Adding a different wingtip will also change the aileron forces. Personally, I find the cub ailerons to be heavy and slow ... including the clipped wing version.

    If you can wait until OSH, the person that works in the builders' workshop is an Ace owner/builder extrodinare. He may also be able to shed some light on the situation, too. I am very curious as I did the drawings of the original plans ... updated and converted from original Corben parts and drawings. I need to see if I can find a copy of the drawings laying around the house.

  6. #16

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    Thanks for all the replies and information guys, I really appreciate it. I've got lots of stuff to ponder on this now. The nice thing is the plane is built perfectly to plan-and I have them as well. I'll keep after it and get it as good as it can be. Again, thanks for the info!

  7. #17

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    pacerpilot, were you able to resolve this issue? I was reading one of Tony Bingelis's books and he stated that high tension on cables will make the controls feel stiff. I recall, though, that you had checked the tension on the cables.

  8. #18

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    I still holding my breath on the final outcome! I want to learn what caused the issue ... or if the forces are just high compared to say an RV (which the forces SHOULD be a lot higher than an RV). And the roll rates should be A LOT lower, too :o)

    If at Oshkosh 2016, please let me know. I enjoy looking at what wonderful works people have handcrafted that I had a small part in. 316.295.7812

    Thanks! (a different) Ron

  9. #19

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    Quote Originally Posted by Ron Blum View Post
    I still holding my breath on the final outcome! I want to learn what caused the issue ... or if the forces are just high compared to say an RV (which the forces SHOULD be a lot higher than an RV). And the roll rates should be A LOT lower, too :o)

    If at Oshkosh 2016, please let me know. I enjoy looking at what wonderful works people have handcrafted that I had a small part in. 316.295.7812

    Thanks! (a different) Ron
    I appreciate the continued interest guys! As for the aileron issue..., well, I've sort of learned to live with it. From what I/we can determine, the "ratio" of aileron movement to stick movement is kind of high-with standard ailerons. So really what is happening is a "feeling" of heaviness. They're actually moving a lot relative to stick movement and since they don't have the "differential" affect a Friese type ailerons they just feel heavy. The roll rate is typically slow as you'd expect for a slow, heavy, huge winged airplane. I've checked and rechecked the rig, made small adjustments, and now just fly it. I don't think I'll make Osh this hear, maybe next year. It would be fun to run the big green machine to WI and back! I just need to figure out the wind noise issue on my radio. Someday???

  10. #20

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    Quote Originally Posted by pacerpilot View Post
    the "ratio" of aileron movement to stick movement is kind of high-with standard ailerons ... they don't have the "differential" affect a Friese type ailerons
    You can easily make a couple changes that will change the feel of the controls.

    1) I am not sure, but I believe that there are enough "junctions" in the aileron control system that you can make the controls both differential (the "up" aileron goes up more than the "down" aileron goes down) and exponential (the movement of the control stick moves the ailerons less initially then more as the pilot gets toward the stop.

    A) Differential - This will also assist with adverse yaw as the "up-going" aileron creates less total delta drag as it goes up, and moving the "down-going" aileron less will create less increased delta drag on the "up" or "outside" wing.

    B) Exponential - This will make the ailerons feel lighter when small inputs are made around neutral ... and heavier when OMG (large) inputs are needed. Pilots typically don't guess well on how much force they are putting in during those situations :o)

    C) Both differential and exponential movements can be accomplished through using different portions of the control system arcs.

    2) The aileron leading edge is also very critical to the "feel" of the flight control. You mentioned Frise ailerons. Depending on how the aileron is hinged, the forces will get lighter as the leading edge changes from: elliptical to circular to bread loaf to squared, as the leading edge shape changes what shape gets exposed (or hidden) to the airstream when the surface is deflected. This is a little more advanced, but Experimental airplanes can make changes with balsa wood (Hobby Lobby 40% off), double stick tape and aluminum tape (both at Dollar Tree).

    Bottom Line: You're flying a fun airplane and enjoying it. Why make changes :o)

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