🚀 go-pugleaf

David Svoboda (svoboda@rtsg.mot.com) wrote:
:| a multibladed prop (or fan) inside a shroud.  There are also stationary
:| blades which serve to "unscrew" the air, resulting in a more laminar airflow

: Laminar?  I think not.

  I was careful to use the precisely vague "more laminar" since it's not
  nearly as efficient as contra-rotating fans.  If you have a right hand
  prop spinning opposite to a left hand prop, near enough to be tightly
  coupled, the result is three times thrust, instead of the intuitively
  expected two times thrust. 
  
  It's the translation of the air motion spinning around the axis of travel
  into air that is moving in a column parallel to the axis that gives the
  "gain".  At any rate, the static blades are there to translate rotational
  force to linear force, but there isn't an equal amount of opposite force
  at opposite rotational frequency, so there's not as much "gain" realized
  by using static blades.

  If somebody wanted to advance the state of RC modeling, they could develop
  an affordable contra-rotating transmission for the RC airplane engine.  It 
  would pay for itself by fixing tail heavy planes and giving a .40 size
  engine .60 sized performance.  Not to mention calming the "take off, roll
  left" effects for beginners.  You could also break two props at once...

-----------------------------
Bill Chidester     Fan Engineer 1969
		      (Retired) 1970