Flaperons

[Luked 71]

I happened to meet a guy at Oshkosh that owns a Kitfox (nobody at our get together), and he was saying that he rarely uses the flaperons. When he does it's more for trimming the plane for cruise. I've only flown planes with flaps. How useful are the flaperons on these planes?

[EDMO 1078]

The guys in Alaska, and others I guess, with short runways, sandbars, etc, use them regularly - I think they are about 1/2 as effective as flaps for lift - hardly any drag compared to a Cessna with 40 degree flaps.

EDMO - "Foxy Flapper"

[Av8r3400 1179]

As Ed says, they don't add much drag, but do add a ton of lift and slow the stall speed.  They are very effective for landing and taking off short.  (On my Model IV Kitfox I am rigged to 26º down at full deflection.)  If you think about their position and function, they make the wing an under cambered wing when deployed as flaps.  

 

With the advantage of  the flapperon still being in high pressure, high flow air even when the wing is fully stalled.  EG- you still have full aileron roll control through the stall.

 

There is a subtle genius to the Junkers style flapperon as a control surface.

[EDMO 1078]

Just one more added point - this is coming from a builder who is making flaps and ailerons - remember your student pilot days, when they told you to make crosswind landings with little or no flaps - the flaperons do inhibit the roll control somewhat, as compared to full-deflection ailerons - so you don't want to deflect the flaperons much in crosswind landings.

EDMO

[Luked 71]

Thanks guys. This Kitfox owner must have operated off a runway with plenty of room. Our conversation was so short I didn't think to ask.

[C5Engineer 1170]

Not using them for takeoff leaves a ton of performance on the table. I fly an approach 5-8 mph slower with the. On vs. off. I only have 15 degrees on mine.

[akflyer 1427]

What Joey said X2   If they are not using, then they are not trying to get everything out of the Kitfox or Avid.  On Skis it makes a huge difference as pulling on the flaperons will pick the tail up and out of the snow much faster.  Same on sand and loose gravel.  My normal take off is pop full flaperons at 35 indicated and get into low ground effect to get me off the grass, sand, snow , water etc. then hold it in low ground effect and bleed off the flaps as I accelerate then climb out.  If I am coming out of a really short strip, I will keep about 1/2 flaps in till I have cleared the obstacle.  Landing I use full flaperons unless I am on floats, then I use full flaps for the approach and at the flare I bleed off about 1/2 flaps so I have enough elevator to get the nose up and slow the plane down real nice before I touch down.  Depending on how I am loaded on floats, I may not have enough elevator to get the nose up where I want it with full flaps.

 

 

[Luked 71]

Good to know. Thanks guys for the information. The reason I thought this guy's comments were interesting, is because I had heard similar opinions somewhere else before. I'm guessing that people who don't use the flaperons very much basically fly their plane more like a regular GA spam-can.

 

One thing I really like about flaperons is the fact that there are no moving parts inside the wing. It reminds me of the old RC trainers I used to fly that used "torque tubes" (music wire) to run the ailerons.

[wolves200 31]

I take off from a very short grass strip, I used them alot, mine are set 15 deg. either full or none for take off and landing...

 

I start the take off roll with no flaps, lift the tail wheel as soon as possible, when I reach 35kt  pull full flap and back the stick a little. Rest is history!

 

for landing, I come with full until I´m about to touch the ground, then I retract them fully to reduce ground effect and I will stop very fast.

 

like Leny and Jeoy said, without flaps, is like having a muscle car on bicycle wheels!!

 

Regards

Dimi3

[cliff 45]

The early model Avid that  we are rebuilding doesn't have the flapperon mixer upgrade to stop the controls from reversing.  We were going to wire the flap handle in the up possistion to keep aileron throw at it's fullest and keep them from reversing. We have Kitfox 3 wings with droop tips and we don't plan to operate off of short strips. The Kitfox wings are a couple of feet longer than the original avid wing. We will basically be using the plane to fly local only for fun. no long cross countries. Our Kolb Twinstar doesn't have flaps and we seem to do just fine. Are the flaps really that important on an avid considering the way we are going to use the plane? Should we look into upgrading the mixing system?  If we should upgrade the mixing system, where can we get the parts now since Brent isn't answering his phone? Will wiring the flapperons in the up possistion eliminate the chance of aileron reversal? We are getting very close to being ready for taxi testing and we would like to hear your input. Thank You.

 

Ps, How do you use the spell check?

[marksires 484]

Unless I'm thinking wrong, you'd want to wire the flap handle down.  Pulling the handle up moves the flaperons down to act like flaps, and is when the control reversal might happen.  Down is the 'no flaps' position.

Mark

[cliff 45]

Mark.  I meant it to say that the flaps were in the up posistion not the handle.  The handle will be secured in the level flight posistion.

[dholly 718]

Why make flaperons totally ineffective when you can easily limit travel to prevent reversal?

[cliff 45]

Because I didn't know you could do that. What is the proper procedure to do so? How much travel can you safely have? 

[dholly 718]

Just add a simple stop to limit deflection to 15* degrees max. Pic shows one option, more good info on control rigging and reversal in this thread: http://www.avidfoxflyers.com/index.php?/topic/595-kf-iii-rigging/

[akflyer 1427]

It's 15 degrees max if you don't have the f7a. And this came from across the pond as a possible issue, not from this side of the ocean. If I remember correctly, one of our members in the recent past made a bunch of the f7a kits and was selling them. I have as much flap as I can get now and my limit is the control horns hitting the turtle deck, and I have never felt a hint of reversal. I darn sure wouldn't be so scared of it that I disabled the flaps. Not only will they get you off the ground quicker, but they will help for minor trim in flight and if you watch the gps you would be amazed at how small of a deflection up or down will make you loose 5+ MPH. I like to set them in the air where I have the least resistance to roll input. You can get a heavy stick feeling real quick with only a couple degrees either side of the optimum position.

[cliff 45]

Thanks for the info. I always use flaps for take off in my Cessna 180. Our kolb does just fine without them and many other light planes that I have flown such as Champs, Luscombes, and T-craft don't have flaps. I just figured that It wouldn't much matter if they were dissabled but, your reasoning makes very good sense. I will limit them to 15% which is better than 0%. I have a know it all at the airport that tells me we will die if we fly this thing without the mixer modification, It always helps to look for a second opinion. Thanks again.

[EDMO 1078]

Cliff,

     The later model Kitfoxes have differential ailerons - The early models take lots more pedal work to counteract the yaw - these planes had lots of hours flown before any improvements.

Good Flying,

EdMO

[Av8r3400 1179]

What Ed said!  There are literally thousands of Avids and Kitfoxes flying using the flaps in the original mixer setup.

 

Fly the airplane.  Try it out at altitude to see what you have.  Set up an adjustable stop like in Doug's photo (if needed!) and you are all set.

[1avidflyer 1983]

All the Avids I've been around had a nut welded onto the top of the seat truss that you could screw a bolt into that would act as a stop for the flap lever.  I believe Doug's picture is of a Kitfox, but the Avid is built very similar in that area.  Here is a shot of a MK IV Avid getting the seat truss strengthened.  See the 1/4" nut and bolt on the top center of the seat truss.  Jim Chuk

[cliff 45]

Thank you all for your advice. We put the wings and flapperons on yesterday. The plane was originally a speed wing and we had a pair of Kitfox 3 wings that we were going to use on our other Mark 4. So now we have an Early Avid speedwing with Kitfox 3 wings, struts, and flapperons. How should we rig the ailerons? We only have a Mark 4 manual.

[cliff 45]

Sorry I made a mistake in my previous thread. The kitfox 3 wings are held up by Avid struts. We went through a bunch of work to fabricate wing attachment brackets so we could use the Avid struts.

[dholly 718]

Cliff - a search for "rigging flaperons" will return the "Kitfox III rigging" thread I linked in post #15 earlier, plus a dozen more threads with some very good info and tips. I don't think you should have much trouble getting your flaperons to KF3 rigging specs since the Avid mixer and flaperon control rod setup is so very similar to the corresponding KF3 equipment, both in physical makeup and adjusting methodology. Only potential issue I can foresee would come if the Avid vs. KF had dissimilar flaperon control rod lengths or flaperon horn attach angles. That might require fabricating new rods but not a terribly big deal.

[dholly 718]

All the Avids I've been around had a nut welded onto the top of the seat truss that you could screw a bolt into that would act as a stop for the flap lever.  I believe Doug's picture is of a Kitfox, but the Avid is built very similar in that area.  Here is a shot of a MK IV Avid getting the seat truss strengthened.  See the 1/4" nut and bolt on the top center of the seat truss.  Jim Chuk

Jim- you are correct, my pic showed a Kitfox but I did the same thing on my Mk-IV. Quick and easy, nothing permanent. On your pic, I can't help but notice the seat truss strengthening but no bungee gear. If using the aluminum gear, don't forget to strengthen the side sill trusses ahead of and behind the spring gear mounting clamps. That is the 'new' weak spot, trust me. (

[1avidflyer 1983]

Hi Doug,  that pic was of the seat truss strengthening before the plane was completely reassembled.  Bungees were put on later.  I guess things are like a chain, the weakest link breaks first.  If you strengthen that link, then the next weakest one goes next.  I suppose the ideal thing is not to pull so hard, but that is easier said than done some times.  ) Jim Chuk

 

PS I like you stop just fine, I was just pointing out that he might have what he needs already if he puts a bolt into the nut.... ;-)