As you know, a ducted fan/propeller (Figure C) has a strong tendency to pitch the nose-up during "tilted " forward flight due to the front part of ductlip itself generating more lift. Thus any ductedfan tilt attempt for forward flight is counteracted by this tendency of the lip airflow interaction. typical ductedfan pitching moment My Concern

My wondering thus is if the same behavior, (i.e.: undesired "auto selfrightening" nose-up pitching moment at tilted forward flight) exists for a similar annular wing configuration around a lower discloading multirotor (figures A,B):

Proposed annularwing multirotor (numbers below are in figures A,B)

1- Thick annular wingring body around a low discloading multirotor to function as a simple wing and as a prop guard. (lip curvature of wingprofile is reduced as much as possible to hopefully reduce pitching moment of ductlip lift. (FIG B)

2-an ordinary multirotor with a lower discloading (about 20kg/square meter) than a typical ductedfan*(to further reduce any strong wing-prop interference)*.

3-Big gap between propellertips and annular wing unlike ductedfans (to hopefully reduce any propeller-duct interference)

(NOTES: yes I know the ringwing body looks heavy, but my wondering is related to the pitching moment with that shape/thickness in mind and not construction-wise as I will be testing with very light inflatables and other special ultralight construction methods)

3d view, parts shown topview, propeller-sidewall gap visible Wing profile: tiny curvature marked in red rear view

I would really like to hear from experts who have a deeper knowledge than me about pitching up moment related to such configurations. Would an annular shape wing body - with a minimal lipcurvature and a big gap distance to the propellers- have a strong pitching up moment like ducted fans during tilted forward flight or not?

My thoughts, I am not sure but :

  • if there is indeed a pitching moment, is it affected by the discloading of the multirotor props?
  • if there is a pitching moment, is it affected by propeller-wing gap?
  • if there is indeed a pitching moment, is it ONLY due to the inherent shape of an annular wing alone? regardless of discloading & propeller tip gap, even if the lipcurvature radius is reduced to a minimum?

I suspect that if the lipcurvature radius is greatly reduced, the pitching moment will also get greatly reduced?


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