rigging flaps

[efil 01 74]

manual says  -3 ° for better crus speed ...so it is up or down? personally i would go for 3° down, so when you push for speed, the AoA decrease and flap finally is 0° in relative wind so less draggy.....or... -3 is up cause the flap airfoil chord is not the bottom flat line, so flap is 0° when bottom is -3

i'm lost and don't feel very confortable with the idea of flying with up reflexing flaps

[1avidflyer 1983]

I for one had a plane that was very squirlly when the flaperons were in the reflex position.  That is with the front of the flaperon  down, and the back up.  I've heard others say the same.....  YMMV  JImChuk

[akflyer 1427]

reflexing the flaps will give you nose up trim.  Something most of these planes benefit from.  The Maule uses reflexed flaps to improve cruise as well.  Having 3° of flaps down will give you nose down trim and increased pressure on the elevator causing even more drag and slower flight.  I have had the plane loaded tail heavy to the point that I had to pull in a bit of flaps to get the nose down and tail up.  The flaperons really do allow you to play with them a bit and trim the plane out.

 

[NorthIdahoAvidflyer 374]

After completing my plane I had a very heavy stick and heavier roll rate. After checking the flaperon rigging I found one was reflexed to 4.3 and the other was 1.6. I had accidentally reversed the adjusting rods.  After resetting them both reflexed to 2 degrees it flies like a dream and the roll rate is fast and responsive. The only reason I have not tried one more degree is because it flies so good now I dont want to mess with it. Don't be afraid to reflex the flaperons. The Zenith 701 was also found to benefit from reflexed flaperons. 

[Guest]

I for two have had less than desirable experience with reflexing flapperons.

My fat Avid had me fooled for some time that something was fundamentally wrong with the rigging. I had measured everything over and over again and nothing made sense until I took the reflex out (pulled in a tiny amount of flaps) and it cured everything.

It was much more pronounced on the Fat Avid than other Avids I have experience with because of the push pull cables used rather than solid linkage. When I sit on the ground and measure it appears that I have some flap dialed in. However in flight the flapperons flatten out as all the play is taken out of the system by aerodynamic force.

So now I have what looks like a bit of flaps engaged with the plane on the ground with flaps "off" but in flight the flaps look just about the same as the wing visually as far as AOA.

 

[akflyer 1427]

I play with  my flap handle in the air.  I don't have any set positions on it and they will reflex just a bit when pushed all the way down.  I just move the flap handle and wiggle the stick a bit till I feel the least resistance in roll.  I have played with the reflex and GPS as well watching ground speed.  I can pick up an extra couple miles and hour if I really play with it but then again, it is all dependent on load as to where they trim out the best and give the best cruise.  No one single setting that fits all situations.

 

[TJay 1041]

I set my Kitfox at 3 degrees trailing edge down. flew hands off right out of the gate. Cant comment on what they fly like trailing edge up. But alot of people do it with good results.

[Turbo 162]

Per aerodynamics convention, positive flap deflections are trailing-edge-down.  I conjecture that Dean used an asymmetrical airfoil shape for the flaperons,  consistent with their use as flaps, but with the side benefit that the flaperons' aerodynamic moment would eliminate play in the linkages. 

I believe that these birds are overendowed in the wing-camber department, so fast-cruising with 3 deg trailing-edge-up flaperons makes sense as a way to undo some of that excess nose-down wing aerodynamic moment due to all that camber.  It is apparently better to do this with the large-span flaperons, despite their short lever arm, than carrying the additional downforce on the H-tail.

Edited 20 Nov 2018 by Turbo

[efil 01 74]

 

so to resume : -3 ° is up flap, everyone got is own rigging in range of -3/+3

 i will go for about a gently 0° first ;°)

 

[Turbo 162]

I've got to admit that I don't know where my flaperons are rigged with flaps "zero" in the cruise configuration.  My flap friction disc is unreliable, and the flap setting can change if I sit in the wrong spot on the seat.  My solution to this was to use cable ties to fix the flap handle relative to the control tube.  It flies fine, with crisp roll authority.  I have not experienced any of the sensitivity others claim to have felt at or near the cruise setting.  I have not used the flaperons as flaps so far.

Manu, I wouldn't get too worried about the exact cruise flaperon angle, especially with your unique wing section shape.  Your optimal value could be different, and you will likely need to explore its contribution to pitch trim in flight test.  In addition, your CG position will play a role.

Edited 22 Nov 2018 by Turbo