Flaperon install - Binding push-pull tubes and interference when folding. Model III

[LSaupe]

Installed the flaperons today only to find that I have interference issues when trying to add flaps or when trying to fold the wings.

It almost behaves like the flaperons are too far back and down. Leading edge will hit the fuselage tubing when trying to fold and; the main push-pull rods that connect to the bell crank of the flaperons hit the fuselage tubing at any reasonable deflection or when pulling in flaps.

I cant find anything specific on this dimension. Anyone else run across this issue? If I try to use flaps the rods will bind against the fuselage, forget any aileron movement at that point for sure. Locks up solid. Same on both side of the plane.

I did not do the initial install so unfortunately only have the old manual to go by. Seems like there was a pre-placed pilot hole that must have been used.

Angle of hinge mount (50 degrees) and positin of flaperon bell crank (1+11/16 from bottom flap edge)have been verified.

Do you guys see anything obvious?

Flap hitting fuselage:

http://i733.photobucket.com/albums/ww339/LSaupe/Kitfox/DSCN3754_zpsichqri5s.jpg

Relation of bell crank in neutral flying position:

http://i733.photobucket.com/albums/ww339/LSaupe/Kitfox/DSCN3753_zpseioklku8.jpg

Relation of hardware to trailing edge.

http://i733.photobucket.com/albums/ww339/LSaupe/Kitfox/DSCN3757_zpsnzpauvrq.jpg

Larry S.

[cgruby]

Hey Larry,

I just went through an extensive rebuild on my type III, which entailed installing a new cabin top and splicing in new tubing from the lower part of the fuselage. I too had a little interference with the fuselage-to-flapperon bearing mount. I chose to remove those bearings and fabricate a new design, which works for me.

It looks like your problem is much more acute than mine which begs the question, Was there extensive fuselage repair work done to your airplane?

My airplane is 20 miles away, but I'll be glad to get measurements if they'll help. Just let me know what you need.

Good Luck,

[t j]

I wonder if it would help to add a little more wing dihedral?

[DesertFox4]

Don't know if this will help but when I bought my Model 3, the flap handle had a mark on the tubing next to the handle about 3/4 of the way to full flap deployment. The flap handle had to line up with that mark in order to fold the wings and not bind or hit something with the flapperons. I was never sure if all model 3s had to do this to fold the wings or just mine.

[LSaupe]

Thanks for the feedback on this.

Actually it is a new kit construction (started by someone else). All tubing looks straight and both side are identical. Not sure if dihedral would effect much in the root area, however did double check it was at 1 degree.

I can live with the folding issue if I need to, but the rod binding (both sides) is a real concern (upper fuselage green tube to gray push pull rod) shown in the pic. Obviously I can mod the rods, but very hesitant to do so until I investigate more.

What is a typical clearance, however, between the vertical flaps and fuselage tubing when folded? I have been disconnecting the flaps to fold, so even if they could rotate them, it woudn't be successful (though it did initially try it).

[t j]

A fellow here finished a Model II a few years ago and had the same problem with the aileron control rods hitting the fuselage tubing. He isn't in town any longer but his kitfox is still sitting at the airport. I took a look today to see what I could see. You probably should talk with someone that actually has built an early model Kitfox to get confirmation that this is truly a good fix.

ON the left side it looks like he shortened the solid block that connects the control tube to the flaperon horn and drilled a new hole for the top bolt. You can see the notch in the top of the block where he cut it at the bolt hole.

It appears this allows the control rod to move up further as the stick is deflected so that it just clears the fuselage tube as it moves back.

I couldn't tell if the right side block has been shortened. The distance between the bolts center to center on the left universal block is 3/8 in. The right side universal block bolts are 3/4 in. center to center.

Left side, note the notch in the top of the block where it appears to have been cut and new hole drilled further down.
9524

Full right stick, flap handle full down.
9525

Full right stick, flap handle full up.
9526

[LSaupe]

Great stuff there Tom. Thanks for taking the time to check and posting the pics. Glad to see (I think) that I am not the only one.

[t j]

Thinking about this some more. I wouldn't make any modification to the control parts just yet and wait a bit to see if someone knowledgeable of the early kitfox control system knows why this happens. It could be some simple thing with how the parts are installed.

This control system is quite different than the later models most of us are familiar with.

I should point out that the kitfox in my photos above also had the problem with flaperon clearance over the fuselage when folding the wings. It seems he had to lift the wing as if to flex it a little to get the wings folded if I remember correctly.

[LSaupe]

Thanks for the feedback. Yep, will be in a holding pattern as I try to learn more on this.

[Av8r_Sed]

Hi Larry,
I was at the hangar today and took a few pictures of my flaperon control arms for a comparison point. For some reason, the left one has much less clearance, but does not hit anything through the full range of motion. It gets closest to the seat belt attachment point.

I did have clearance issues with the original lower bearing supports when folding the wings, so I cut them off and went with a hinged type closer to the Model IV standard. I do not have clearance issues with the tube at the back of the turtle deck.

Let me know if any further measurements or pictures would be helpful.

[LSaupe]

Thats perfect. Thanks for posting these!

[LSaupe]

I actually have a boat load of clearance to my seat belt bolt.

Still working on this. Hopefully success soon!

[avidflyer]

If you have lots of clearance from the seat belt bolt, and his is real close but works, it seems maybe your flaperon arms were installed to far in towards the center of the airplane. Please take a picture from the same angle as Av8r Sed's first picture. It that is the problem, I would think you could drill out the rivets the hold the arm to the flaperon tube, slide the arm in further and drill and rivet in the right place. Jim Chuk

[Av8r_Sed]

I believe my arms were both riveted and glued with structural adhesive. So if Larry's were done the same way that would mean drilling out the rivets and applying some heat?

[LSaupe]

Tried a suggestion to invert the push-pull rod. This puts the large weldment down near the mixer vice up near the seat belt bracket.

Appears to be a solution on the surface (also looks a lot cleaner). Any reason to not go that direction?

[LSaupe]

My dimensions are the same as what AV8RSED shows. Still looking for the smoking gun here. Some success with inverted rods though.

[LSaupe]

Paul:

Any chance you could post a pic of how your hinged lower rud support is put together. I need to make something similar and could use some ideas.

[LSaupe]

Quick update. Ended up going with the upside down rods and those would just touch a full deflection. Added a bit of curvature to the rod (each side) and the world is a happy place. Will forgo the folding problem for now.

Thanks to everyone for providing feedback on this problem. Thanks to Tim T for making the trip up today to help in the final resolution and rigging!

Larry

http://i733.photobucket.com/albums/ww339/LSaupe/Kitfox/DSCN3785_zpsbnpo4jiy.jpg

[LSaupe]

Hey TJ:

In the pics you posted. By chance does that guy have issues with folding clearance as well? Mine looks almost identical to that one. Is it also a Model III?

Larry

[t j]

Hey TJ:

In the pics you posted. By chance does that guy have issues with folding clearance as well? Mine looks almost identical to that one. Is it also a Model III?

Larry

It is a Model 2. What I remember is he did have some difficulty with clearance between the flaperon and fuselage. It is sitting in an hangar with the wings folded now. If I see that hangar open when I'm at the airport I'll take another look and see what I can see.

[cgruby]

A couple of flapperon measurements you asked for:

Chord = 7 7/8"
Leading edge to centerline of spar = 2"

I didn't measure the distance from flapperons to the turtle back because I had the wings deployed, but generally around 1/8".

Good luck,

[LSaupe]

Thanks Chuck. Very much appreciated

[t j]

It is a Model 2. What I remember is he did have some difficulty with clearance between the flaperon and fuselage. It is sitting in an hangar with the wings folded now. If I see that hangar open when I'm at the airport I'll take another look and see what I can see.

Today I looked at the Model 2 kitfox. What I can see with the wings foldled is:

The left wing tip is about 2 inches lower than the right wing tip.

The right wing flaperon leading edge has about 1/2 in. clearance to the fuselage tube at the back of the turtle deck opening and the cross tube just ahead of that where the seat belts attach. The left wing flaperon leading edge is resting on/touching both those tubes.

The lower half flaperon horn bearing material is attached with camlocks on the rear tab on both sides. The camlocks are removed and that end of the bearings swings down out of the way for wing folding.

The aileron control rods are disconnected to fold the wings. They hit the tube at the top of the seat back about 1/4 inch short of being able to connect to the flaperon horns with wings folded.