I have started to gather some information on the little Bagalini Colombo parasol-wing microlight (more on that later) and I am impressed by its thoughtful and straightforward design. One interesting feature is the use of tapered full-span Junkers-style external ailerons on an otherwise dead-straight, constant chord, zero-twist wing. I say ailerons and not flaperons because the details I have are in Italian and I am still trying to figure out whether or not they can be lowered as flaps.
The ailerons are constant-chord for their inboard half and then taper to about 50% of their original chord over the outboard half. The aileron spar is a tube and the taper is taken out of the lower surface only, as if you placed a ruler on the bottom of the spar tube and drew lines to the upper surface, progressively slicing off bits of the aileron profile. The result is substantial twist and increased relative thickness of the aileron profile for the outer half of the span, both of which would keep the outer portion flying better at higher angles of attack then the inboard portion. That should essentially provide a little effective aerodynamic twist to the main wing as well. Presumably, Signor Bagalini's reasoning for doing this was to ensure very docile low-speed handling and stall behavior, already usually pretty good with an untwisted, constant-chord wing.
This now has me thinking about the effect of tapered ailerons/flaperons/flaps, whether plain or slotted or split or what have you, on constant chord wings in general. I could also see using not tapered control surfaces but constant chord ones that are reduced in chord in distinct steps as you move outboard, especially for flaps or flaperons. Especially with flaps or flaperons down, that would provide significant aerodynamic twist to untwisted main wing due to impact on the effective angle of attack of each flaperon section and might be a neat way to ensure docile low-speed handling.
This quick sketch and a shot of the Colombo in flight should help illustrate the point. I’d love to hear your feedback on this idea.
Cheers,
Matthew
The ailerons are constant-chord for their inboard half and then taper to about 50% of their original chord over the outboard half. The aileron spar is a tube and the taper is taken out of the lower surface only, as if you placed a ruler on the bottom of the spar tube and drew lines to the upper surface, progressively slicing off bits of the aileron profile. The result is substantial twist and increased relative thickness of the aileron profile for the outer half of the span, both of which would keep the outer portion flying better at higher angles of attack then the inboard portion. That should essentially provide a little effective aerodynamic twist to the main wing as well. Presumably, Signor Bagalini's reasoning for doing this was to ensure very docile low-speed handling and stall behavior, already usually pretty good with an untwisted, constant-chord wing.
This now has me thinking about the effect of tapered ailerons/flaperons/flaps, whether plain or slotted or split or what have you, on constant chord wings in general. I could also see using not tapered control surfaces but constant chord ones that are reduced in chord in distinct steps as you move outboard, especially for flaps or flaperons. Especially with flaps or flaperons down, that would provide significant aerodynamic twist to untwisted main wing due to impact on the effective angle of attack of each flaperon section and might be a neat way to ensure docile low-speed handling.
This quick sketch and a shot of the Colombo in flight should help illustrate the point. I’d love to hear your feedback on this idea.
Cheers,
Matthew
