Re: F1D longitudinal trim

From: <RLBailey_at_care4free.net>
Date: Sun, 5 Nov 2006 12:14:48 -0000

Tapio

CG is much too far back; suggest you move CG forward by up to 10 mm and retry. You need to eliminate the deep stall first.

Bob

  ----- Original Message -----
  From: Tapio Linkosalo
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Saturday, November 04, 2006 12:53 PM
  Subject: [Indoor_Construction] F1D longitudinal trim



  I built my first attempt of F1D this autumn, but have not so far managed
  to get it trimmed. The pmain dimensions are as per Big Square, but I also
  too good look at Kagans model drawings when drawing my model. It came out
  heavy though, 1.8 grams. My first attempt...

  The thing is, I do not seem to get level flight out of the model. It
  climbs some on the initial power burst (have flown with 1/3 motors, and
  use back-off) then starts coming down pretty fast. Tried thicker rubber,
  but it did not seem to make difference, also have reduced prop pitch
  (which seems awfully low anyway, and this does not seem to have any effect
  either. So I suspect there is something else going on. The decalage also
  seems quite large (at least compared to F1M, but then D also has smaller
  tailplane, so I guess more forward CG and more decalage is the way to go).
  The model also seems to be very sensitive to decalage setting. At one end
  it stalls, at with just a tiny bit of reduced decalage, it seems to dive.
  And finally, when the stall accurs, it seems deep and model barely
  recovers. I tried one flight with full motor, climbed six meters, then the
  model stalled and made a "waterfall" all the way to the ground level, only
  started flying again at 1 meter.

  So the question is, what might cause all this? One thing that came to my
  mind is that the fuselage/tailboom is too flexible. The weight of these
  components is about 30 to 50% more than with "competitive" models, but the
  balsa is not super (but rather Stiffness Coefficient a bit less than
  100%), and I did not put boron to either tube or boom. The motor tube has
  a rigging to take some load, though.

  What kind of decalage should the model have, and what size of rubber is
  used in F1D?

  -Tapio-



   

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Received on Sun Nov 05 2006 - 04:20:26 CET