autoreply
Well-Known Member
(Top and sideview, Boermans)
Intersection drag is a bit more complex as the name suggests. On laminar aircraft (basically only composite pushers and sailplanes), early transition to turbulent airflow causes the majority of the extra drag, especially since the influenced area extends quite far in front of the junction and over the wing.
So if we have such an airframe (composite pusher or sailplane), why not move the wing out of the way? On a pylon, a chordlength or so on top of the fuselage?
Basically that's just a small step further than the Mü31 or the Streifeneder Albatros. The wing upper surface is totally undisturbed (laminar), and by placing the pylon a bit more aft, the disturbance on the lower wing is minimal, since the pressure field on the pylon itself it orders of magnitude smaller as the fuselage. We still have the pylon/fuselage intersection, but there too, the pressure field and affected area are much smaller.
Looking at transition now, it seems that (based on transition on a body of revolution) you can absolutely massively increase laminar flow and thus spectacularly reduce total drag, both on the wing and on the fuselage. In honesty though much more so in a sailplane, since they have a much wider range of speeds.
So, is this a feasible idea and would it really reduce drag considerably? Apart from the Cirrus SH converted (but where I can't find anything else about) and the Streifeneder Albatros that does something similar, I can't find any precedents.
Structurally I don't see any red flags. A bit more complexity and the torsional loads (groundloop) for sailplanes are massive, but not too much so. It's probably also lighter (one-piece middle wing)
Am I missing something, or is it a feasible idea?
