OK Charlie, let's start with the Aeronca 7 series ailerons since that is the airplane which Gary mentioned.
Any control surface requires clean airflow over it in order for it to efficiently do it's job.
An up aileron dumps wing lift by creating a deflection of the upper surface airflow destroying some lift (acting like a spoiler) in order to make a wing drop and a down aileron increases lift in order to raise the wing. Due to the Aeronca/American Champion design when at low speed/high angle of attack the boundary layer on top of the trailing edge of the wing is separating leaving some dead air space above the ailerons. When the up moving aileron is deflected into that dead air space there is nothing for it to react against. The other down aileron is the only one doing any work. Since the down aileron will then be at an even higher angle of attack it will stall causing the down aileron wing to drop. Remember practicing stalls over the top from turns?
The up 7 series aileron has a section which acts like a drag producing fence which protrudes below the wing. This is for the purpose of counteracting the adverse yaw drag generated by the down aileron.
When this airplane is flying at low speeds above stall the ailerons can be moved from stop to stop with only a very little amount of rolling action of the airplane. Very sloppy.
American Champion's fix is to add an optional set of spades to the ailerons which fly well below the wing in clean air. Thus they are effective at high angles of attack of the wing. They are Just a band-aid!
IF the ailerons were redesigned so that the clean air below the wing was redirected through a slot between the wing and the aileron leading edge there would be clean air for the up aileron to push against. This would make both ailerons share their responsibilities rather than having just one doing the roll control.
Ha! You beat me to the punch while I was typing.
Vic, At the high speeds of our airplanes the ailerons move very little in order to perform their function. At high speeds there is a slight amount of boundary layer separation and very little pressure differential top to bottom at the aft portion of the wing. Thus any gap will not generate a differential airflow and it's accompanying drag.
Isn't this basically the same thing?Logical but in this plane it was for a more important reason than preventing an unwanted wing drop, it was because the wing was not going to respond.
Gary, that nasa pdf link comes back: "The page you tried to access does not exist on this server."
I'd love to see that.
Vic
This one? Page 27 is a list of references.Gary, that nasa pdf link comes back: "The page you tried to access does not exist on this server."
I'd love to see that.
Vic
This one? Page 27 is a list of references.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930083935.pdf
or this one?
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091708.pdf
I never gave that much thought but yes it should since it would be operating in undisturbed air.Which brings up another question regarding ailerons (I'm exposing my naivete each time I post anyway): would a balanced aileron extending beyond the wing tip be an useful thing in slow flight?
I'm talking about, instead of spades, having the aileron extend past the wingtip with a forward-of-the-hinge airfoil like we see on the empennage of super cubs.
Curtis's put the aileron between the wings in 1911 and Fokker extended them past the end of the wing in the late teens, nothing new
Glenn
no adverse effects. That is one of criterion that the FAA looks at for issuing approvals for modifications.I've mentioned before extending the Cub's upper flap farings over the ailerons. I liked that change and had no adverse effects. Same for rubber elevator and rudder seals.
Gary
no adverse effects. That is one of criterion that the FAA looks at for issuing approvals for modifications.
Accepting that, What positive effects did you notice?
I get the elevator and rudder seals which would reduce leakage through the gap at high angles of deflection. What degree of improvement is something I'm not certain of.
Can you address the improvement to the ailerons other than you liked it?
We've discussed this previously. My goal was stable slow flight, maximizing lift, and minimizing aileron induced wing tip stall.
I will say one thing. Every little bit helps and obviously one incremental change can later surpass or incorporate the performance of earlier mods.
It was quite impressive compared to other planes I have flown. Others that flew it noted it was "tuned in".
Gary
Gary,
You mentioned the wing wash being set to 1.5°, Had you flown with other twist settings as well during your development?
Gary, my goal was as yours ,to better the low-speed capabilities of my mount that was not originally built with that in mind. The single biggest improvement to the slow speed characteristics were the addition of the slats. Not only did they make they wing hang on at higher angles of attack , but improved the low-speed handling even at lower angles of attack. As was discussed in a previous thread, they make the wing lift more efficient at all angles.
Before the slats, I could aggravate the wing and get some severe breaks into Spin entries. Now you cannot get it to break, it must be flown into the spin.
Did you make any changes to the tail...like seals or increased surface area as a companion to the slats at very slow
Gary
Sealed the gap which did not make any difference ,do have VG’s on the bottom. I run out of back stick at slow speed’s and due to the high thrust line ,can’t ride the power at high angles of attack because it will push the nose over well Before stall. Have a J3 tail now, I understand the super cub tail is a drop in replacement with no mods, that is the next thing on the list.