Relative position of flaperons to wing

[LSaupe 123]

Starting to sound like a broken record with all these posts.

 

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.

 

Do you guys see anything obvious?

 

Flap hitting fuselage:

 

 

Relation of bell crank in neutral flying position:

 

 

Relation of hardware to trailing edge.

 

Edited 3 Aug 2015 by LSaupe

[EDMO 1078]

There was one pre-drilled hole in the rib ends - builder puts the front hole in after aligning flaperons.

My rods disconnected for folding - the flaperon should be level, not leading edge down, when folding and crossing fuselage tubes.  It should turn vertical when almost folded.

I have no clue about rod binding, unless flaperon tubes were cut too short before belcrank levers were added.

There should be some dimensions of tube length inside of turtledeck?

EdMO

Your book should also give angle of belcrank lever to angle of flaperon - your belcrank lever looks high...Looks like it will hit turtledeck if you put flaps down, or down aileron.

Don't ever worry about asking too many questions - always glad to try to help fellow builders.

I hope someone has better advice for you.

 

There is a YouTube video of "How to fold Kitfox wings", but the guy who posted it disconnected rods first. (Crazed Pilot) also may be listed as Wildirishtime?

I don't know anything about how to find stuff on Youtube, or how to post it here.

If you cant find it, maybe someone can help you get it.

Edited 3 Aug 2015 by Ed In Missouri

[dholly 718]

Flaperon control rods must be disconnected on the Kitfox III before folding the wings. If you place a straight edge along the flat bottom of the flaperon chord, the hole in the control horn should be 1-11/16" above the bottom surface of the flaperon. If you place a straight edge along the top of the ribs, the angle relative to the back side of the flaperon hinge should be 50°.

[EDMO 1078]

Thanks again to the Doug Holly Technical Information Library! 

You nailed it Doug!  

EdMO

Edited 3 Aug 2015 by Ed In Missouri

[LSaupe 123]

Flaperon control rods must be disconnected on the Kitfox III before folding the wings. If you place a straight edge along the flat bottom of the flaperon chord, the hole in the control horn should be 1-11/16" above the bottom surface of the flaperon. If you place a straight edge along the top of the ribs, the angle relative to the back side of the flaperon hinge should be 50°.

Thanks Doug.  All those dimensions check out.  I did check those prior to avoid cycling you guys.

 

Yep, I did disconnect prior to folding and only started the vertical motion until just prior to the final position.

 

I gotta think the two issues are related somehow.

[Dusty 126]

What model have you got? It looks to be a 3

Kf3 wings fold without disconnect,due to different geometry and the swivels that you have.

The flapperons pop vertical soon after the wings begin to move but are very close.

Flap lever neutral

Kf4 has to be disconnected,(some kf3 have been retrofitted)due to the simpler better mixer.

Unrelated to your problem but worth mentioning is a bearing that goes under the flapperon and a corisponding bearing on the turtledeck

I would strongly recommend fitting one,as a flutter may develop!

Photo two should this bearing,but the clearance looks about right! or possibly a little big

[LSaupe 123]

Dusty:

 

Yep it is a III.  My impression was that they should auto fold as a III but anticipated needing to disconnect if need be.

 

Clearance isnt even close.  Need about another 1/4" or so to make the swing.  What is more concerning is the control rod interference with the fuselage.  Definetly cannot fly that way.

 

Any chance one of you could check your position relative to my third image?

[EDMO 1078]

Can you show and describe exactly where control rod hits fuselage, and which direction? 

I haven't understood that part yet.

EdMO

Edited 3 Aug 2015 by Ed In Missouri

[akflyer 1427]

Are your wings swept forwards when fully opened and pinned in place? 

[LSaupe 123]

Ed:

 

Image #2 shows the interference.  Gray push-pull tube hitting the bright green fuselage tube.  Same on both sides.  Happens when the flapersons go to a higher angle of attack such as during a turn and/or pulling on some flaps (basically when the bell crank is raised).  The aft-double tube portion hits the green tube.  Almost like the angle is too great on the flaperon bell crank (though it measures out fine) or maybe the flaperon bell crank arm is too short (though I have no dimensions to check againts).  Neither of which have bearing on the folding issue, which I can live with if I need to.

 

Leonard:

 

No wing forward sweep that I can see from the naked eye, and I sight right down the total leading and trailing edges the best I can.  Looks straight to me.

Edited 3 Aug 2015 by LSaupe

[LSaupe 123]

What model have you got? It looks to be a 3

Kf3 wings fold without disconnect,due to different geometry and the swivels that you have.

The flapperons pop vertical soon after the wings begin to move but are very close.

Flap lever neutral

Kf4 has to be disconnected,(some kf3 have been retrofitted)due to the simpler better mixer.

Unrelated to your problem but worth mentioning is a bearing that goes under the flapperon and a corisponding bearing on the turtledeck

I would strongly recommend fitting one,as a flutter may develop!

Photo two should this bearing,but the clearance looks about right! or possibly a little big

Thanks Dusty.  Bearing will be next, but wanted to see where things fell out first amd make sure there were no issues (which there seems to be).

[EDMO 1078]

Somewhere I have seen a dimension for either the distance the flaperon tube sticks out of the flaperon, or how far it sticks out past the inside of the turtledeck - I will be looking for that for you.

My one thought, not considering the above, is that you could take the bellcrank off and make a longer tube for it, and that would give you clearance from the fuselage...?

EdMO

2nd thought - Would it be possible to just bend the belcrank arm toward the center of the fuselage a little to give you more clearance?

Edited 3 Aug 2015 by Ed In Missouri

[dholly 718]

Thanks Dusty, I stand corrected. I had to disconnect the flaperon control rods when I folded my KF3  because I installed my baggage sack with a hard floor. Absent this, it would not be necessary.

 

Larry -

• is the measure between the inboard end of the flaperon and outside tab of flaperon control horn belcrank correct (approx. 5-3/16")?
• have you leveled aircraft fore and aft, secured control sticks perfectly vertical and confirmed that the FBK-7 control mixer belcrank is level?
• have you then centered the control stick side-to-side, and with the flap handle all the way forward, confirmed the flaperon neutral position?
• have you confirmed that the tops of the FBK-9 individual flaperon belcranks are approximately parallel to the FBK-7 control mixer belcrank?
• have you properly set your flap limit stop (instructions below)?
  
  How to find the proper degree of flap for your "stop":
   
• first find the neutral flap position as shown on page CF-18 Fig. CF-12, of your Construction Manual and mark that position for the "zero flap" setting.
• move the control stick all the way to the left (or right) until it stops.
• while holding the stick in this position, slowly pull the flap handle up until it starts moving the control stick toward the center.
• when the top of the stick has moved toward the center 1-1/2 inch, that is Max Flap. This step can be completed after you have finished the rigging process on pages CF-17 through CF-19 of the Builders Construction Manual.

[EDMO 1078]

Larry,

    I have an idea of how to move the rod / belcrank attach point one diameter toward center of fuselage if you cant bend belcrank -

I would have to draw it to post it - Still think bending is best - But Wait - I just saw something that don't look right.

EdMO

 

     Something in that #2 photo just don't look right - the belcrank elbow should be well INSIDE of fuselage tube if wings are pinned in place - the round part that is riveted to the flaperon tube HAS to sit inside the nylon bearings, and it looks like the elbow is outside of that area and would keep it from rotating.....   It's hard to tell from the angle of the photo.

Larry,

     Can you take a photo with wings pinned, and looking straight down at the belcrank?

And, check that 5 3/16" measurement that Doug listed?  You may need more than that for some reason?

Edited 4 Aug 2015 by Ed In Missouri

[LSaupe 123]

 

Thanks Dusty, I stand corrected. I had to disconnect the flaperon control rods when I folded my KF3  because I installed my baggage sack with a hard floor. Absent this, it would not be necessary.

 

Larry -

• is the measure between the inboard end of the flaperon and outside tab of flaperon control horn belcrank correct (approx. 5-3/16")?
• have you leveled aircraft fore and aft, secured control sticks perfectly vertical and confirmed that the FBK-7 control mixer belcrank is level?
• have you then centered the control stick side-to-side, and with the flap handle all the way forward, confirmed the flaperon neutral position?
• have you confirmed that the tops of the FBK-9 individual flaperon belcranks are approximately parallel to the FBK-7 control mixer belcrank?
• have you properly set your flap limit stop (instructions below)?

  How to find the proper degree of flap for your "stop":

   

• first find the neutral flap position as shown on page CF-18 Fig. CF-12, of your Construction Manual and mark that position for the "zero flap" setting.
• move the control stick all the way to the left (or right) until it stops.
• while holding the stick in this position, slowly pull the flap handle up until it starts moving the control stick toward the center.
• when the top of the stick has moved toward the center 1-1/2 inch, that is Max Flap. This step can be completed after you have finished the rigging process on pages CF-17 through CF-19 of the Builders Construction Manual.

 

 

 

Doug:

 

Thanks for the complete and detailed info.  Much more provided there than the Kitfox III manual,  It really covers only about 1/3 of what you have there.  It includes the first 4 bullets you have there, and yes all were complied with.  The 5th bullet (flap stops), I see no reference for in the manual (or am I missing it)?  I have been contemplating how to make one (for both up and down limits).  Any ideas on what might work well?

 

With the flaps set for CF-12, putting the stick to either the full left or right will allow no movement of the flap handle (I.e. no deployment allowed) before my FCT-25 part impacts the fuselage crossing tubes.  So, as long as I dont deploy flaps at all I can just get the motion I need.

 

I will try again in a week and a half (Guard duty this weekend) to ensure I havent missed anything. 

 

Thanks again for all the info on this.  I hear talk of flap setting of "neutral".  Is this the same as flaps up (control rod forward and down)?

[LSaupe 123]

Larry,

    I have an idea of how to move the rod / belcrank attach point one diameter toward center of fuselage if you cant bend belcrank -

I would have to draw it to post it - Still think bending is best - But Wait - I just saw something that don't look right.

EdMO

 

     Something in that #2 photo just don't look right - the belcrank elbow should be well INSIDE of fuselage tube if wings are pinned in place - the round part that is riveted to the flaperon tube HAS to sit inside the nylon bearings, and it looks like the elbow is outside of that area and would keep it from rotating.....   It's hard to tell from the angle of the photo.

Larry,

     Can you take a photo with wings pinned, and looking straight down at the belcrank?

And, check that 5 3/16" measurement that Doug listed?  You may need more than that for some reason?

Hi Ed:

 

Actually moving to the center would make things worse and the green crossing tube (~ 45 degrees in the pic, lower right to upper left) is the issue.  Here is another shot which also shows the maximum amount of deflection at impact (which in this case is full left stick). Flaps at full up/rod down in this pic.  Or.. would you exepect to see any more deflection at full turn with flaps?  Probably tough to see in the image.

 

Cant get the bird back out for about a week (lives in the garage right now, takes two to unfold plus would have to put the flaps back on).   Will shoot more when I can if a re-riiging check shows no improvement.

 

Edited 4 Aug 2015 by LSaupe

[EDMO 1078]

Larry,

    I see now that the elbow is inside of the turtledeck, as it should be.

Just a real wild idea - I know the book says it should go as you have it - BUT, what if you could turn the control rod upside-down, so the small end would be sticking up? - Crazy ideas sometimes work! 

    I think the max degrees for the flaperons has been posted before - some say you can get reversal of controls beyond a certain degrees - others have exceded that and did not have the problem.

    I would bet that Doug has the numbers, and Suberavid has exceded them!

EdMO

    I cut 2.5 inches off of my rib tails, but mine is not regular Kitfox....

Edited 4 Aug 2015 by Ed In Missouri

[1avidflyer 1983]

I don't know if this was mentioned already, but how was it determined where to drill the holes in the rib tails for the flaperon hangers? If the holes were 1/4" closer to the back of the wing the control rod would probably clear. Looks like you have 1 7/8" from the back of the wing to center of first hole. Maybe others can measure theirs and see if they have less. Just got back from the garage, I measured my Avid Flyer MK IV and the first hole is 1 1/4" from the back of the wing. That doesn't prove that this is your problem. By the time the Kitfox 3s came about, the design wasn't quite as close of a copy of the original Avid. But that being said, my control rods didn't hit the tubing like yours does. Jim Chuk

PS just looking at it some more, and one possible fix might be to cut off and re weld the bottom tangs on the control rod 90 degrees from where they are now. That would rotate the top 90 degrees and give you an additional 1/2" of clearance. Maybe that would cause another problem, I'm not sure, but it might be worth looking at.

Edited 4 Aug 2015 by Jim Chuk

[EDMO 1078]

Jim,

    I was also thinking he might be able to move the flaperon hangers forward one hole - but might have to rework slot in turtledeck and relocate nylon bearings if he did that.

    Sooner or later, this Redbird will be flying!

EdMO

Edited 4 Aug 2015 by Ed In Missouri

[dholly 718]

Well, next I would confirm the location of the strut attach brackets. I know you're not gonna like this but in the manual it says when test folding the wings with temporarily mounted and rigged flaperons:

If the flaperon does not clear the tabs and crosstube by at least I/8", it wil-I be necessary to raise the wing by rnoving the strut attach brackets inboard.

Pray that is not the case! If you can eliminate that, the old Kitfox Owners Newsletter (KON) often contain important nuggets of info. Well worth the time to go thru them. For example, these might be worth following up on with your issue (there may be more, I didn't look further):

From September 1989 KON

FLAPERON RIGGING: The flaperons neutral position, as shown in Fig. CF-12, Page CF-18 of the construction manual, can be safely set at 1-3/4" below the front spar (vs. 1"). This may greatly facilitate the rest of the rigging procedure.

From January 1990 KON

MIXED UP BELLCRANK: About (25) FBK- 7 Mixer Bellcranks were inadvertantly built incorrectly as a mirror image. Most of these incorrect bellcranks were shipped in November 1989. Please check to see if your Mixer Bellcrank looks like the one in diagram F-5 page F-6 of the builders manual. lf your bellcrank is not correct, please let us know and return it for the correct bellcrank.

RIGGING DETAIL: on page CF-18 of your builders manual, step 69, it tells you to have the tops of the FBK-9 Individual Flaperon Bellcranks approximately parallel to the Mixer Bellcrank. Actually, on the Model 2 the inward ends of the FBK-9's when properly rigged will point down, possibly 15* degrees or more, with the flaperons leveled according to instruction.

As for making a cheap, simple but effective flap handle stop, just use an adel clamp on the tubing next to the flap handle (see pic of Tom Jones' Kitfox).

Edited 4 Aug 2015 by dholly

[EDMO 1078]

Doug,

    What about an alternative to the OMG "moving wing strut attach fittings inboard" - Like splicing in a short section to the struts to make them longer, and increasing dihedral?  Should be same results?

    AND DONT FORGET - His spar / fuselage attach holes are already drilled...He should not attempt to change dihedral now.

    I would rather move the flaperon hangers forward one hole and rework the turtledeck and nylon bearings rather than screw with strut fittings on spars, or struts!   ALSO - His wings are covered and painted.

 

    Maybe he will get lucky and find out his control rods are wrong!

EdMO

Edited 4 Aug 2015 by Ed In Missouri

[LSaupe 123]

Fabulous stuff there Doug!  Thanks!  Time to do some more digging.

 

Turtle deck slots and nylon bushings have not yet been cut/fit (which may turn out to be a positive in this case).  If need be, I can live without the folding clearance issue.  Seems like a dihedral change would be needed then might stress the root pins (maybe not).  Opening up the flap neutral position to 1 3/4" would definetly help.  Time to start verifying parts.

 

Thanks again for taking the time out of your schedule.

 

Larry

[LSaupe 123]

I don't know if this was mentioned already, but how was it determined where to drill the holes in the rib tails for the flaperon hangers? If the holes were 1/4" closer to the back of the wing the control rod would probably clear. Looks like you have 1 7/8" from the back of the wing to center of first hole. Maybe others can measure theirs and see if they have less. Just got back from the garage, I measured my Avid Flyer MK IV and the first hole is 1 1/4" from the back of the wing. That doesn't prove that this is your problem. By the time the Kitfox 3s came about, the design wasn't quite as close of a copy of the original Avid. But that being said, my control rods didn't hit the tubing like yours does. Jim Chuk

PS just looking at it some more, and one possible fix might be to cut off and re weld the bottom tangs on the control rod 90 degrees from where they are now. That would rotate the top 90 degrees and give you an additional 1/2" of clearance. Maybe that would cause another problem, I'm not sure, but it might be worth looking at.

Thanks Jim.  Actually, the aft holes are preset at the factory.  The flap hinge is then installed, the bracket rotated to 50 degrees, then the forward hole located/drilled.  A 90 degree rotation (or similar) on the control rod might help a great deal.  

[LSaupe 123]

Is there any chance the Model I, II and III had different flap geometries?  Maybe in cord and/or bellcrank length?  Reaching at straws; in case I may have the wrong set of flaps here.

[1avidflyer 1983]

I believe the 1, 2 , and 3 are all the same.  The model 4 and later are bigger and not flat on the bottom.   I'm referring to the flaperons in my statement.  Not sure on the bellcranks.   Does it show in the manual that one hole is drilled in the rib tail from the factory?  I'm sure the Avid ribs didn't have a hole predrilled in them.   Is it possible that the guy who had the kit before you drilled the holes and they are to far back because of it?  Jim Chuk

Edited 4 Aug 2015 by Jim Chuk