Noel Guy

Hi Guys, I need a little help. I am trying to set up the flap system on my F18F. The problem im having is with the flaps and the flap servos. Ill try and paint the picture. I have put the servos in the wings using a push rod ect. when the flaps are fully up, there is that much strain on the servos that they grind really bad. When the flap is in its fully up position the servo has to hold the flap there which is loading the servo and they are getting bloddy hot. when I deploy flap....say to takeoff position, there is no load on the servo and the grinding goes away. same with landing position. But when I retract flaps to the upright position grind, grind, grind.....Its bad. I have tried everything, including changing servos 3 times. The flaps seen to be placing to much resistance on the servos in the up position. I need help guys...its doing my head in. What have you guys done.

marc s

I'm no expert but how is the servo set-up. Do you have the flap set so when the flap not deployed the servo is at 'centre point' or is it at one end of the throw?

I have been told that its best to run the servo so when no flap is NOT deployed it is as close to 100% ATV in one direction as possible, half flap is roughly center position and full flap is as close to 100% ATV in the other. I guess there will always be some loading in a static test but this I would imagine is also reduced substantially during flight when the loading is reduced by the action of the airflow over the wing.

As I said I'm no expert but these are my thoughts.

Noel Guy

Hi Marc, I have actually tried all configurations, but what you just described is the way I thought it should be. Either way I do it there seems to be excessive binding. I am also thinking that maybe I have the control horn (the one in the flap itself) to close to the front of the flap (hinge point). Maybe if I move it out towards the centre of the flap more, it might ease some of the pressure.

Rob B.

My Feedback: (7)

I had the same problem, for me it turned out that what I thought was a full up flap was actually a couple of degrees too far up. The bottom of the flap should be a straight line with the bottom of the wing. The last couple of degrees of too much up flap really put a load on the servo (it was not binding, it just had less mechanical adavantage, I guess).

Rob B.

frothingslosh

My Feedback: (6)

Marc -

Put your flaps in "full up" position, then adjust the ATV till the grinding stops. If the flaps are still full up, problem solved. If not, you have excessive resistance in the flap itself which will have to be corrected.

Noel Guy

Thats exactly whats happening, excessive resistance in the flap itself. so how do you correct it. As I mentioned previously, If I move the control horn further to the middle of the flap will it help.

frothingslosh

My Feedback: (6)

I don't think moving the horn is going to help you much if any . . . it's still going to exert an excessive load on the servo which is a no-no. I recommend you direct your attention to reducing or eliminating the resistance in the flap system itself.

Craig B.

Can you post some photos of your flap and servo arms in the up position? Sounds like you have a mechanical binding issue in the flap itself. If you disconnect the flap pushrod, are you able to move the flap freely to the full up position or do you feel some resistance?

Is your servo arm contacting on the cutout in the wing?
Is the clevis contacting the wing skin in the full up position?
Is the flap itself contacting the upper wing skin in the full up position?

I would be interested to see some photos to see if we can help.

Craig.

grbaker

My Feedback: (29)

I use servos with 180 degree rotation for all of my flap installations. I program a Hitec servo to accomplish this but any 180 deg servo would work. At full up and full down, there is no load on the servo. The attached pics show an installation inside the fuse of a JMP T-33, but I have a similar installation on my YA F-18 and my Facet 2300 (servos in the wing).

JetsRC

You might want to check out the top lip of the wing where the round part of the flap goes inside. Sometimes you need to sand a bit of this surface to release the tension.
Also check the round surface that goes in the wing. Check it is not applying too much preassure to the upper lip of the wing or you will have a permanent force against the servo. If you have this problem you may use a hot gun or iron and slowlly bend the surface a bit more.

I am sure you checked this but have you noticed that the flap has a point where it can't move upwards anymore? Please make sure that this is not the problem.

Michel

Noel Guy

Hi Michel, mate spot on...I have spent today working on the flap itself and all seems better, although there is still the normal digital growl...I think the binding has gone....Im assuming that a bit of noise isnt too bad. Craig & frothingslosh, you were also spot on. I will post some pics as I did re-position the horns anyway. I dont think my initial position was right.

Noel Guy

How do you achieve the 180deg travel inside the wing when you are restricted by the wing itself....I love the pics by the way, its a simple idea.

bcovish

My Feedback: (8)

Using one of the Hangar 9 volt/amp meter will detect any binding issues or over driving of the servo during setup.

grbaker

My Feedback: (29)

It depends on how the flap is hinged. Here are pics of my YA F-18 and my Facet 2300.

The F-18 is hinged at the center of the flap with Robart hinges and it has external flap linkage. You have to have a larger opening in your servo cover to clear the linkage. One of these days I will refinish the F-18 and fabricate some sort of linkage covers over the flap linkage to hide the large hole in the servo cover.

The Facet linkage is all inside the wing. This is possible because the flap is hinged 9/16" below the wing and the flap horn is glued into the flap leading edge just below the top edge of the flap. I really like this setup and will try to use it on any future projects.

tp777fo

My Feedback: (28)

Gary,
That facet wing looks familiar..did you build it or buy it already built?

junglejet

Has anyone found where the structure is inside the flap that would be a good place to attach the horns?

grbaker

My Feedback: (29)

Tom, I built the wing. I got the cores from Kerry Sterner and built the swept wing for the Facet. I sold the original straight wings that I built for it to a guy in Canada.

Hope to see ya at GSW! It's been a long time since we've done any flyin' together.

tp777fo

My Feedback: (28)

I plan on being there come hell or high water. Should have plenty of jets for the weekend if I can get my Hawk finished. Seeya there!