Add flaps,how difficult???
 

I want to add wing flaps to my Great Planes Cessna182 ARF. It has dual ailerons already. Can any one tell me where to start, what would I need to buy, and and what reinforcements are necessary? Thanks for any info on this idea.

Add flaps,how difficult???
 

You'll need to get some 3/16" to 1/4" balsa stock that is wide enough to cover the back of the wing and the front of the flap that you will be cutting out. You'll also need some 1/16" balsa to seal the ends of the flap and wing when you cut them out.

Mark the size of flap area you want to cut out. That will be the full cut out. Then make marks 3/16" to 1/4" from that mark to indicate the amount of material to trim so it will still match the wing after attaching the flap facing material.

You'll have to figure out how you want to hinge the flap before you decide on the front shape of the flap. If you want scale flaps you have to round the leading edge of the flap piece and make a matching concave fit on the back of the wing.

Easiest way is to leave the flap leading edge/wing trailing edge flat and then use monokote hinges on the bottom of the wing and flap. When the flaps are up the ends are flush, when you put the flaps down there is a big gap on the top but it doesn't affect performance.

You'll also need to buy two more servos and a "Y" harness and mount the servos like the aileron servos.

I'll post a picture later...I'm at work. I did a flap mod to the Goldberg Cub and to a Goldberg Senior Falcon.

The hardest part is deciding to cut into the structure...after that it's cake.

Don

Add flaps,how difficult???
 

Thanks for the info. I will keep an eye out for those pictures.

Add flaps,how difficult???
 

Here's a real quick pic I drew up. Hope it helps for now.

Add flaps,how difficult???
 

Nice diagram....it helps alot. What about the servo? Could I use one servo right in the middle of the wing and connect both flaps with some kind of torque rod? Just an idea I thought might work. :confused:

Add flaps,how difficult???
 

You could rig up a torque rod but it's a whole lot easier to just cut two more servo slots like the ailerons and throw 2 servos in there. Trust me. :-)

The torque rod means you'll have to do a lot more surgery on the root of the wing. Separate servos just means framing a hole for the servo mount.

Don

Add flaps,how difficult???
 

This shows the flaps up. The gap shown is because the Goldberg pieces in the wing were rounded. If the pieces you glue in are flat edged the gap will not be as noticable.

Add flaps,how difficult???
 

This shows the flaps down. Monokote hinges makes this easy.

Add flaps,how difficult???
 

This shows the bottom of the wing. Monokote hinge makes it slick.

Add flaps,how difficult???
 

Same set-up on my friend's Cub

Add flaps,how difficult???
 

Cub flying away at half flaps

Add flaps,how difficult???
 

Those are great pictures of your setup. I have decided to use Robart hinges for my Cessna. I have a GMS 47 2 stroke and the plane hauls butt. I dont think that Monokote would hold up wih this setup. Your tips did help decide where do my cut and so forth.

Add flaps,how difficult???
 

:( I finally finished adapting wing flaps on my Cessna 182 ARF and happy to report that they worked better than I thought. After takeoff I went around the field feel out the flying characteristics and everything felt the same as before. The first time I deployed the flaps to about 50% the plane just balloned straight up. No panic there but took me a while to get used to if. After about 4 minutes of flying the engine quits when I am downwind from the field. So I yell deadstick and deploy the flaps 100% , the plane slowed down and gradually lost altitude, I brought the Cessna around like I usually do on a power landing.

Add flaps,how difficult???
 

Well, yeah, trim changes are to be expected. No need to be unhappy. If you have a computer radio you can use the flap-elevator mix to compensate.

Enjoy! post a picture.

Don

Add flaps,how difficult???
 

Its too late for pics now............... After that beautiful deadstick landing I managed to tune the engine right and went for the second flight, slowed down and flew some slow fly-bys over the runway with the flaps fully deployed. What happened next I cant explain. As I attempt to bring the plane around for the approach the plane went into a nose high attitude at about 25 feet of altitude, I managed to recover from this position but I simply lost it before I attained more airspeed. My opinion is that I slowed the plane way too much on the approach and I could not recover once the wings stalled. I'm working on fixing the damage on the nose and wing.

Add flaps,how difficult???
 

I had too much fun with these flaps and will not make that same mistake the next time I take it up. I will take out the GMS47 and drop in the Saito 72 for scale flying. Should look nice on landing approaches. I will post photos as soon as I fix it.

Add flaps,how difficult???
 

Inboard flaps -> big pitch changes with power.


Having flaps like this creates a pitch trim change both in the difference between a clean wing and flaps down - and between flaps down at idle, and flaps down at full throttle.


First, putting the flaps down at the same speed you cruise around at creates extra lift off the flaps. A secondary effect is that the flaps create extra downwash, which pushes down on the elevator - further pitching the aircraft up. THis what folks call balloning. Once the speed bleeds off, the lift increase & downwash effects fall away - and the pitch down effects of the flap on the wing itself take over, and the plane will settle into a rock solid and groovy, if slow, nose down glide path.

Airplanes are different of course- on some, the pitch down effect overwhelms the pitch up effect and the plane tucks immediately. Sometimes, the plane balloons and the nose never comes down. It all depends on the relative strengths of the downwash on the tail vs the direct pitching moment change the flaps put on the wing.


Here's what happened on Southbay's plane, I think. It happens on my TF Gold Cessna 182 as well.

With full flaps and idle engine, it will glide nicely, but steep. However, when throttle is applied, the slipstream acts directly on the flaps to create instant lift plus downwash on the tail - with little airspeed to otherwise counteract the resulting pitch-up. I've done 3d loops with planes this way. So, you end up low, slow and dangerously nose high, even though you just added full power.

What I do on the Cessna is:

I use a little bit of elevator mix down with application of flaps. Maintains better airspeed for control response on approach.

I have 2 flap settings, about 20 deg and about 50 deg. The 20 deg setting creates a lot of lift, not so much drag, does not create strong downwash, and does not react heavily to throttle changes. It does react, but not enough to kill the plane. It is a great setting for takeoff.

So, when I am on approach I have the flaps way out for that extra drag. If I should want to go around, I apply partial power just to fly level, then I pull the flaps up to takeoff setting. Then I can apply full throttle and get out of there. The takeoff setting allows me to get rid of the drag and poor reaction to power of full flaps , without suddenly dropping a bunch of lift and sinking in to the runway.

Did I write that clear enough to follow?

Add flaps,how difficult???
 

John,

Sounds like the set-up on my Cub and Sr Falcon. Clear enough.

Don

Yep
 

Agreed...

On a real Cessna, the first thing you reach for after deploying flaps for landing is the pitch trim wheel, and give it some down trim. You could do that with your radio's trim switch, but it's true that using a mix instead will give you more consistent results.

One more thing
 

I wouldn't try this on the cessna, but ifyou have another plane and an extra radio mix, you might try mixing in down elevator proportional to throttle, when the flaps are full out.

I have a trainer 60 that I modified with slotted flaps that I also used throttle->elevator mix. It was a very strange thing to fly in low & slow and add throttle. It wouldn't speed up, nor would it nose up. It would just levitate upwards with more throttle. Sort of like a reverse elevator. Of course, it was still going forward, but not very fast.

Add flaps,how difficult???
 

I will dig out my JR 8103 manual and try the mixing that you guys are recommending. I should have my Cessna ready by this weekend and will give it another try. All your responses have been really helpful in understanding how flaps work.

Add flaps,how difficult???
 

It's probably obvious but I'll say it anyway. When you start out with your flap to elevator mix, start out with small percentages and test fly between every change in the mix.

It'll save you some wild unexpected pitch changes.

Don

Add flaps,how difficult???
 

Will I mix up elevator as the flap lowers?

Add flaps,how difficult???
 

It depends on which way your plane pitches as you deploy flaps.

You said your plane ballooned up so I would start with a down elevator mix. Again, start small and fly between every change so you can see what it's doing.

Don

Add flaps,how difficult???
 

Using enough down trim to avoid balloning may cause the approach to be too steep once it settles down. You may have to accept a little ballooning, or remember to slow down before putting flaps out.

Just take Don's advice, a little change at a time.