Good day!
I asked this question way down in another thread but it goes here.

A gentleman at the field was listening to my complaints on an viscious snap w/an edge on landing. He said make sure the ailerons are slightly up on landing. ?????

He claimed that because the ailerons were pointing up (on landing), when you make adjustments, one aileron will drop thus increasing the lift to that side of the wing.

When the ailerons are down (on landing) when you make adjustments one aileron will raise from it's lift creating position. In effect taking away lift, encouraging the dreaded stall/snap, or could.

I say theory, but it makes sense. Does this sound right?

Spanky

I'm sure there are guys here with more knowledge on this one, but I can say a couple of things:

From my own experience, reflexing the ailerons a tad can sometimes help delay a tip stall, so it's worth trying.

However, I personally think the reason "why" given to you is wrong. I think the help is because the raised ailerons reduce the AOA of the wing slightly, and the effect is more pronounced at the tip, since the ailerons are usually a greater % of wing chord at the tip than the root. So you basically are adding washout when you raise the ailerons.

Thanks Montague
Ok, that makes sense. I'm not familiar with washout but I think it is put in for landing, right?

If thats the case couldn't you say that by reflexing the ailerons up, you can then add more up elevator throw and not snap during regular flight? Or are we talking only landings here?

Nice Free State Aeromodelers website by the way.

Spanky

Washout is basically twisting the wing so that the wing tip is at a lower angle of attack (AOA) than the root of the wing. This causes the root to stall first. It helps during landings, but it also helps any time you starting messing around near the "critical AOA", which is the AOA where the wing stalls. Washing is frequently used to tame a plane that has a bad snapping tendancy.

In practice, you can SOMETIMES add more up elevator once you reflex the ailerons. However, you don't necessarily get a tighter turn or loop. After all, the elevator is basically increaseing the wing's AOA, while reflexing the ailerons lowers it. And a lot depends on the particulars of the plane of course. Some airfoils really don't like reflexed ailerons, others seem to fly better with a little reflex. Also, the more tapered the wing (again, assuming non-tapered ailerons), the more washout effect you get with you reflex.

Basically, I'd say fly the plane, then add a little bit of reflex and fly it again and see if you like the performace better. If you don't, take the reflex out. It's easy to adjust, after all.

Another thing you can try if you want to tame a bad snapping tendancy is stall strips on the wing root area.

Oh, and if you haven't already, check your lateral balance. An unbalanced plane will snap more than one in balance. Does your plane always snap in the same direction, or does it snap both ways roughly the same? And if you haven't sealed the aileron hinge gaps, that can help as well.

Hi All,

Similar questions are being asked at my field...mainly by me! I am thinking of trying flaperons with strip ailerons, however there is some debate about whether to have the flaperons move up or down in the deployed position. Down seems the logical position to me, but some are saying this will increase the tendency to tipstall on landing. However if the flaperons go up the same effect of slower stall speed but less tendecy to tip stall. Any thoughts as to which way to go (up or down) and an expanation of the areodynamics would be great.

I played with flaperons on a 2 meter glider a few years back. For small amounts of movement up to about 7 degrees they added lift with little or no bad side effects. The next little bit up to about 15 degrees started to show some tendency for adverse yaw dispite the fact I had a fair amount of differential in place. Beyond that they really started to have some bad side effects. I continued to use them as an airfoil camber changing tool but never used them at large movements for landings at all.

Later on an ARF with strip ailerons I tried flaperons again. I was sadly dissapointed at the amount of effect they had on the landing speed. Guess they just were not wide enough. But the adverse yaw showed up again and the problem you describe with a nasty stall showed up as well for any travel beyond about 10 degrees down. I never did try it with up reflexing.

The effect they have on models in general will depend a lot on the model layout. Conventional ailerons will benifit from some up reflex as only the outer portion of the wing will have the lift reducing reflex so it will appear that the wing now has some twist in it. However it may also depend on the airfoil as well. With the ailerons up a little you're now flying with a tip airfoil that is basically cambered upside down. Some airfoils may not take kindly to that and tip stall easier. Only an experimant will tell for sure. Do it at least 3 mistakes high at first.

On models with strip ailerons adding reflex probably won't help at all since you've added the reflex over the whole wing rather than just the tips.