Regarding LukeD's quest for perhaps an idealised aileron design that incorporates an effective anti-adverse yaw device, I think what he may be describing was already designed by L.G. Frise in a later evolution of his patent, which was the Hartshorn Aileron (see attached diagram) described in David Luff's excellent book on the Bristol Bulldog fighter (Airlife 1987). This variation, in which the Frise section at the outer tip featured a rising leading edge inboard to the aileron root provided a progressive emergence of the aileron nose into the airflow when deflected TE upwards, instead of it emerging over the whole length of the aileron as on the standard Frise type. There were some negative aspects to the design under test, however, and as the standard Frise was less susceptible to rigging errors, it was not proceeded with.
The discussion here has gone into enormous detail on differential ailerons and their pros and cons: a Tiger Moth for example might just as well not have differentials given the amount of rudder necessary - a great training machine for all that and partly because of that.
Nowadays, starting with the newly introduced cantilever monoplanes from the late 1960's and '70's, initially thick-winged devices such as the Acrostar and Yak 55 and the later Sukhoi 26 and the later carbon fibre-reinforced designs with somewhat thinner sections, like the Extras, these all used symmetrical foils rigged at zero incidence and using ailerons, many of whose maximum thickness around fulcrum lifted the boundary layer and lightened the control. Blunt trailing edges were also introduced for better 'feel'. ' Bulged about fulcrum' ailerons were, I believe, pioneered by Schmued on the P-51 although one test pilot recently commented that the P-51's ailerons are heavy; at least compared with those of the Spitfire or the later Sea Fury with spring tab ailerons.
I utilised the above 'bulged' aileron design on my first biplane project, the Tigerfalk, and the 1/4 scale dynamic model of that had superb roll response according to the builder, the then World Champion R/C Scale modeller, Pete McDermott (Ca 1988), who coined the expression for it, "Stalls like a Pussycat: Snaps like a Pitts"! This featured a modified NACA 23012 airfoil with the upper and lower ordinates from 60% chord running as a straight lines to the TE. Thus the unmodified (original) aileron profile projected into the airflow. The wing chord itself was also reduced from the original profile by that mod.
The ultra-simple, by comparison, Flitzer uses two big, plain high-aspect ratio ailerons with low break-out forces and one test pilot claimed in the aviation press that its 'differential ailerons' were extremely effective - even though they are not differential and operate via 1:1 via pulley system using short runs with no measurable cable drag. Although aiming for simplicity, the later 4-aileron Stummelflitzers Z-1R and S are more complex, involving drag-compensating ailerons which combine mass-balances and spades. In this sense these have migrated towards the old Tigerfalk design, but unless one wants about 270 degrees of roll-rate, the basic sportsplane is ideal at 100+. The exception is the Z-2 Schwalbe which retains the 'square' wingtips of the early Flitzers, but because it has relatively broader chord wings and greater mass, it needed more aileron power to match the manoeuvrability of the original single-seaters.
There is no noticeable adverse yaw when flying the Z-1 or Z-21 and I agree with Billski that 1:2:3 perceived feedback in terms of aileron: elevator and rudder is perfect, although I was initially aiming for 1:2:4 as a recognised 'standard'. The lower profile, rounded fin and longer-chord rudder on some Flitzers was an attempt to achieve 1:2:4 but made little difference. It took all of 30 seconds on my first flight to appreciate the light rudder on the prototype in any case. The control harmony is favourably commented on by Bob Grimstead in his original Kitplanes article and later in PILOT when evaluating the Z-21's handling and aerobatic qualities.
In terms of muscle power and the ability to roll the a/c in either direction with ease, I am considering cranking the stick grip on the latest type, the Sz-1 (work name only) slightly to the left, so the back-handed roll to roll-stop (rolling right) is more comfortably achieved given the limitation of the human wrist (referencing BJC's comment).
I did design a 'hide-and-seek' mass-balance and spade for the SK26 biplane many years ago in which the balance arm was enclosed inside a 'wing pocket' when the aileron was neutral or TE down, but that's another story.
Also attached is a picture of Pete McDermott with the 1/4 Tigerfalk and the latest Flitzer evolution which may use the cranked stick grip.
