[RCSE] Seledkin Sloper Trimming Question

["Eric Weder" <eaweder@xxxxxxxxxxxxxxx>]

A question for anybody who's flown the Seledkin. Have you experienced
incidence or CG problems?

For those unfamiliar with this plane, the Seledkin is an eastern European
moulded 2m hotliner/sloper (it has interchangeable nose cones for glider or
electric), with a 10:1 aspect ratio RG-15 wing. Controls are aileron &
elevator. The horizontal stab appears to have a symmetric airfoil, and is
moulded with a skin hinge elevator. The wing is 3 pieces, the centre panel
is straight, 805mm long with a chord of 193mm, the tips are 605mm long with
tapered LE and TE. The LE taper is somewhat greater than the TE taper, with
curved tips.

I've posted on this before, but have only recently had enough flight time to
start getting the plane trimmed out. The Seledkin used to like to climb
whenever the speed went up. I took out a bunch of nose weight, re-trimmed
for level flight at average speed, and found I had a lot of down elevator in
it. Shimmed up the LE of the horizontal stabilizer by about 0.5mm and
re-centred it. Still climbing at high speed. Took out more nose weight, had
to shim the stab LE to 1mm. The plane flew considerably better but still not
right. Today I put a piece of 1/8" ply under the rear wing at the hold-down
bolt and flew it like that. Much better, it seems to be a lot more pitch
stable going from slow flight to fast.

I've changed the incidence by 3 degrees, which seems kind of wacky for a
moulded plane. Right now my incidence gauge shows the stabilizer at about
1/2 degree positive (lifting) compared to the wing, previously it was 2 1/2
degrees negative. I don't know how the zero lift angle of the RG15 compares
to the line through the LE and TE.

 It needs a bit of down elevator to hold it in inverted flight. I didn't
consciously try a dive test today however it doesn't seem to pull out nearly
as much as it used to. I'm concerned that the CG is getting way behind the
manufacturer's directions, but it handles fine. CG is currently at 122mm
from rear edge of the wing, which is roughly 37%.

Any suggestions? I'd prefer not to leave the wing shimmed up, it has the top
curve of the fuselage moulded into it and it looks bad because it's not
flush.

Thanks
________________________________________________________________________
Eric Weder, P. Eng.					Calgary, Alberta, Canada
Kenonic Controls Ltd.	Eric.Weder@xxxxxxxxxxx		Work: (403)258-6237
Cell: (403)607-9617	eric.weder@xxxxxxxxxxxxxxx	Home: (403)289-8844


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