Trimming Question

[Lance Van Nostrand]

MessageEd,
Paul Villarrubia told me once he trims for a slight sink in upright level flight.  Now I understand why.  Not sure I agree, but I now understand the theory behind it.  Thanks.  I'll have to think on this.
--Lance

  ----- Original Message ----- 
  From: Edward Skorepa 
  To: discussion at nsrca.org 
  Sent: Sunday, August 17, 2003 8:35 PM
  Subject: Re: Trimming Question


  "Model trimmed for hands off level flight"

  This is where your problem started. I can't understand why somebody would want  pattern airplane to fly hands off in level flight. This is how I trim my Piper Cub !

  During hands off level flight the airplane must have some declage to overcome gravity. That declage is what's causing pulls to canopy in vertical dives,  climbs and also in knife edge.

  Personally, I'm still trimming my airplanes the same way like I did in seventieth. Wing - stab  0 - 0. To maintain level flight either right side up or up side down will require light pull -push on elevator stick. I like to have that pull - push to be the same. No more problems with verticals and knife edge. If so, then there is something  else wrong most likely with engine's down thrust.

  Decreasing wing incident will not help in your case. If you still will want your plane  fly hands off in level flight, then you have to put in some up trim and you're back where you started.

  My recommendation - learn to fly with light pull-push or mix it out.

  Ed Skorepa

    ----- Original Message ----- 
    From: Peter Pennisi 
    To: discussion at nsrca.org 
    Sent: Sunday, August 17, 2003 4:33 PM
    Subject: Trimming Question


    I would like some suggestions to overcome a trimming problem I have with my current F3A model.

    Problem:

    The model pulls to canopy on vertical dives as well as vertical climbs

    Currently I have an electronic mix to overcome this problem but this is starting to get in the way on some manoeuvres.

    Setup:

    Model trimmed for hands off level flight.

      a.. CG is about correct. Any more further back model becomes nervous in wind and harder to snap - difficult to control exit. 
      b.. Model fly's with "NO" elevator trim. 
      c.. Model feel's about right inverted. A small amount of down elevator required to maintain level. 
      d.. 1-2 degrees of down thrust.
    Can this be overcome by changing wing incidence or will screw up something else.
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