Sitting at a bar with another pilot and he says "my instructor taught me the fastest way to find the best lift flap setting is to put your ailerons hard over, if it is rigged properly it will be where the engineers found best-lift/least-drag" in other words anymore camber would cause more adverse yaw for no additional lift. At first bounce off the wall this makes sense to me, but given a longer cord for the wing towards the root, or some aircrafts built in smaller angle of attack towards the root, there could be discrencies. What think ye?

Headoutdaplane wrote:Sitting at a bar with another pilot and he says "my instructor taught me the fastest way to find the best lift flap setting is to put your ailerons hard over, if it is rigged properly it will be where the engineers found best-lift/least-drag" in other words anymore camber would cause more adverse yaw for no additional lift. At first bounce off the wall this makes sense to me, but given a longer cord for the wing towards the root, or some aircrafts built in smaller angle of attack towards the root, there could be discrencies. What think ye?

That's it ------ on 180/182 it's 14 degrees for max lift over drag.The "jonson Bar is 10-20-30-40 degrees.
I've got a cam for Cessna johnson bar modified with 14 degree-28 degree-40 degree . Because of the Cessna Fowler flap air OVER the top of the flap gives you 20 percent better take off perfomance , If you DON"T have flap gap SEALS . Piper and others are drag flaps that don't work the same.

It totally depends on the airfoils involved and the configuration of the flap. Like was said just above, for a typical Cessna, that's pretty close. A different airfoil on the wing or flap will change everything.
JH

Bill,

I'm still waiting to meet up so you can demonstrate how the wings on my '56 182 with flap gap seals have 20% less lift than the wings on your '56 182 without them. I'll be at Garden Valley July 9-11, so if you're in the area.........

Dave

dprathe wrote:Bill,

I'm still waiting to meet up so you can demonstrate how the wings on my '56 182 with flap gap seals have 20% less lift than the wings on your '56 182 without them. I'll be at Garden Valley July 9-11, so if you're in the area.........

Dave

Dave:
I'll be there -did you ever get your 182 rigged ?

Bill,
Where is Garden Valley? What kind of event is going on July 9th?

Garden Valley is about 50 nautical miles mostly south and slightly east of McCall Idaho.
Pretty much on a straight line from McCall through Cascade on down to Garden Valley.

So far it has been a wet spring, BUT:
If if a good sized fire gets going in the area then Garden Valley often gets closed for use by the fire fighting crews. It has been known to be TFRed to the public.

Chris C

Bill,

My airplane has not been rigged since we spoke about it last year. Still interested? Thanks and see you at GV (weather permitting).

Dave

Matching the flap position to the aileron position (14 degrees as 182STOL said) is probably a good starting point. But there may have been several other reasons that Cessna set the aileron to 14 degrees, that have nothing to do with max lift. Short of previously researched wind tunnel data, only actual flight testing will prove that out for sure.

The big idea would be to just try 14 degrees and see if you get anything better than the stock 10 or 20. If 14 gives you measurably better performance, then it might be justified to see if 13 degrees or 15 degrees does any better yet.

But remember, if you are trying to get max climb, you are looking for max lift with some ACCEPTABLE amount of drag, not the best Lift/Drag ratio overall. Best L/D is what you are seeking in glide. With engine power as part of the equation, that skews the curves and graphs a little or a lot. Some extra drag might be totally acceptable if it makes a big improvement in lift. All this is dependent on engine power (probably torque) available too. So a J-3 Cub's best rate of climb speed may be very close to Max L/D speed because there is not much "surplus" power available. But an empty 300HP C-185 has enough extra power that flying at a higher drag/AOA point is easily overcome by the power... and so you get to enjoy all that extra lift (turned into climb rate).

182STOL and I have been discussing a method to try this 14 degree flap question out and see whether it is worth pursuing further. Since he has quite a bit of experience in that particular airplane, it should be pretty obvious to him by the seat of his pants whether 14 is noticeably better than 10 or 20.

I'd go with Hardtailjohn on this one. To add to that, remember that climb performance is a quite different question than takeoff performance. And in climb, the configuration for best RATE will almost always be different from the one for best ANGLE, at least in flap equipped aircraft.

MTV

JWTFTT

Wouldn't work to well in my airplane my aileron down deflection is down 9 degrees best take off flap setting is 20 degrees.

mr scout wrote:Wouldn't work to well in my airplane my aileron down deflection is down 9 degrees best take off flap setting is 20 degrees.

Is that standard for Champ-lineage (GCBC, KCAB) wings? Why so little deflection compared to a Cessna wing? Is the aileron-width a greater percentage of total wing span?

There is no one best flap setting. Variables include altitude, cg, weight, runway surface. Most of us just use one setting but it is not always the best. Just to give 2 examples with the 170....at higher density altitudes flaps actually increase takeoff distance. When I take off from very rough surfaces i use two notches of flaps because it gets me light on the gear quicker and allows mw to accelerate over the bumps better. There is a lot more drag and the initial climb angle is less, but it is offset by the initial faster acceleration and liftoff. If I takeoff from a smooth surface I use just one notch because the rolling resistance is less. My best angle of climb at sea level actually come with a half notch of flaps ( modification or holding bar halfway)

For some of us with electrically actuated flaps, the aileron (sp??) deflection is a good huristic (rule of thumb) to use because we all know that the wing behaves efficiantly at this angle of deflection. However, if you are going to make a practice out of short field work, it behooves any pilot to experiment a little to optimize performance.

Recently I have been practicing a technique I learned in a trainig course. I was flying a PA22/20 (Pacer) with manual flaps. The best shortfield performance was achived by pulling the flap handle just before the plane was anticipated to begin flying. Once airborn, the nose is pushed down to level flight, as speed increases the flaps are retracted in climb-out. Having the flap handle in your hand and jockying to whatever flap setting gets the job done in a series of orchestrated movements of the flight controls and flaps.

I tried this recently on my plane (172 STOLtaildragger) which has electrically actuated fleps. I set the flaps to the aileron deflection angle and begin rolling. as the plane picks up speed I lower the flaps a little more which lifts the plane just off the ground and then I hold the nose down and begin to retract the flaps on climb-out similarly to the technique with the manual flap handle on the Pacer.

Bottom line though, if you have a flap handle put as much flap in to make her fly right. If you do it the way I was taught, you will need several subtle adjustments at various stages of rotation and climb-out.

1SeventyZ wrote:

mr scout wrote:Wouldn't work to well in my airplane my aileron down deflection is down 9 degrees best take off flap setting is 20 degrees.

Is that standard for Champ-lineage (GCBC, KCAB) wings? Why so little deflection compared to a Cessna wing? Is the aileron-width a greater percentage of total wing span?

You get less adverse yaw when your up on one side is several degrees more than the down on the other my up is 25 degrees. Don't try rigging this way at home.....

mr scout wrote:You get less adverse yaw when your up on one side is several degrees more than the down on the other my up is 25 degrees. Don't try rigging this way at home.....

Is that different from standard differential aileron rigging? I think any old Cessna wing (modernish tapered chord hybrid from 170B, 172, 182) is also differential (more up than down) but I just wondered why the 9 deg on a GCBC vs 14 deg on a Cessna, if it's a % of wing span thing, or perhaps the tapered end-chord? GCBC has a straight chord profile if I remember.