Trim Question

[Lance Van Nostrand]

Dan,
Interesting posts on this today.  I have a suggestion at the opposite end of theplane from Troy's post.  You may have too much downthrust.  The elevator trim to compensate for this is one of the reasons planes have pull to the canopy.  There are others, like the profile of the fuse when it is the lifting surface in KE, but let's put that aside because if it is the fuse shape, you may need some Nat Penton ventral fins and he's the best to describe them.
  Anyways, at 45 degrees (as in the 4/8 example) you are flying with an odd combination of partial wing lift, partial fuse lift and these may upset the balance of the downthrust and elevator trim.  
  I didn't catch the plane you were flying or how it is setup.  but there are some kits out there now that fly with lots of downthrust, positive incidence in the wing and negative in the stab.  A real complex combination of speed dependent and attitude dependent forces.
--Lance

  ----- Original Message ----- 
  From: Dan Curtis 
  To: NSRCA Discussion 
  Sent: Sunday, April 18, 2004 12:57 AM
  Subject: Trim Question


  Well I have run into a trim problem with a plane that I have not seen before.  Time to tap into the wealth of knowledge on the list.

  The plane generally is flying pretty nice.  Uplines/Downlines are good, minor mixing for knifeedge stuff, good feel while inverted...etc.

  Problem rears its ugly head in rolling to knifeedge.  When using small aileron movement to slowly roll into a 4/8 or 4 pt for example the plane will pitch to canopy.  Not drastically but I would say moderately, more than enough to cause a concern.  However, if you do a full 4 pt or slow roll with rudder coming in the pitch to canopy does not happen.  With good top rudder the plane is trimmed to fly very nice straight knifeedge flight right or left.

  I got to playing with is some today and when I would roll from upright to knife edge with no other input other than the aileron deflection the plane would have a predictable drop of the nose and would begin going to the canopy.

  What am I overlooking here.  Any ideas or has anyone run into this before?

  Thanks

  Dan Curtis
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