Fix for sloppy control horns?

[Flying Dutchman]

I just finished my Prelude and plan to maiden it tomorrow. However, I have a bit more slop in the control horns on the flaps and ailerons than I like (potential flutter problem).

I used the supplied MP Jet clevises (with brass pins) and FG horns, but probably drilled out the holes in the horns a bit too much. The servo end is a Z bend, and seems OK. Are there any tricks for fixing this problem, other than cutting out the horns and replacing them?

@Wayne in his Knief Racer build report mentioned putting some thin CA on a Z bend link to tighten things up, but I wonder whether that would also work on the MPJ clevis and FG horn? I don't want to risk turning a hinge point into a fixed solid joint.

Thanks in advance,
Steven

 

[Flying Dutchman]

Isn’t 0.02mm = 2 microns ? Pretty small.

No, 2 microns would be 0.002mm.

 

[Konrad]

Nope. It is 0.0008 inches. Or in practial terms 0.001 still a large number. Most human fingers can feel 0.0002"

 

[Flying Dutchman]

Nope. It is 0.0008 inches. Or in practial terms 0.001 still a large number. Most human fingers can feel 0.0002"

Glenn asked about mm to microns, not to inches.

 

[Konrad]

True. You answered the decimal issue.

I was giving a size reference, as 0.02mm is rather large being 1/2 to 1/3 the size of a human hair.
I was trying to give a viseral reference as to size.

Them there is the use of the term microns as in surface finish which generaly is a Root Mean Square Measurment (RMS).

 

[gnichola]

@FlyingDutchman can you tell me about your setup? Did you set CG and throws per manual? Did they work out ok?

 

[Flying Dutchman]

@FlyingDutchman can you tell me about your setup? Did you set CG and throws per manual? Did they work out ok?

I used the mid-range for CG (~70mm) and that worked well; I'll experiment with aft CG later. Konrad and others reported that their TopModel planes were way nose heavy per the manual, but the few reports on the Prelude and Avia on RCG suggested that the recommended CG was OK.

I have a bit more throws on all surfaces than per the manual, on purpose to start with. Flaps have much more: I have ~80 deg down for crow.
My motor is the recommended Emax 2826GT, which really is way overpowered, but I had it laying around. That and a 3300mAh 3s Lipo gives a lot of weight up front, which I wanted for fear of being tail heavy. Dropped it all in and -perfect! No further balancing weights needed.

The only thing to note is the elevator horn installation, which per the manual will give a significant down elevator. The actuator bar should end up in the middle of the slot in the fin, not lower. Keep in mind when you cut the push rod to size.
I'll let you know if anything else comes to mind.

 

[gnichola]

@Flying Dutchman, may I ask how you secured your servos in the wing? I have them sitting in the wing and I used the yellow plastic(?) half circle things to hold them in there, which I thought were cool when I first checked them out. But now I am trying to decide how to hold the servos down in there with. Did you use them and if so, how did you hold the servos down? I don't know if I can use screws in there, the material seemed a bit soft when I went to remove material for the servo wires, so I was sort of leaning to just putting a bit of epoxy over the top of each arm which would allow me to remove the servos when necessary.

 

[Wayne]

Yeah, I think the idea is a bit of glue to hold the servo in place.

 

[Flying Dutchman]

@gnichola I did use those hard foam servo mounts to locate the servo's securely, and then used double sided tape to hold them down. Specifically, Scotch Mount clear 15 lb tape, which is about 1.5mm (1/16") thick. The servo's I used (Corona DS-843MG) are 9mm, thin enough to use that tape and still stay below the wing surface. The tape is wide enough to cover the whole side of the servo for a solid attachment to the base plate. Solid connection and virtually no play.

I assume you plan to just put a drop of epoxy in the slot of the servo mounts? I'm sure that will work, but I really don't like gluing down servo's, especially with epoxy. Lots of people do though. Removing a taped servo is not easy, but it seems less destructive than anything involving epoxy.

BTW, this is one great flying plane. I had some concerns about that sharp LE (CF rod), and didn't like the looks of the sagging cover between the ribs, but it's as docile as can be. Good floater, no sharp stall breaks or tip stalls, but good penetration and speed when you need it. The only downside to that beautiful transparent wing is poor visibility at higher altitudes. If/when I tear up the wing covering, I'll redo it in something opaque and/or dark.