[NSRCA-discussion] Joy of Trim

[Chad Northeast]

Guys

A while back I posted this, and have recently got around to the suggestions.  Both Bryan and Nat said that the TL was far too much negative as the Twister has -2.5 deg molded into the fuse.  So away I went, here is a copy of the email (just below) I sent to them after my flights to resolve it.

Before last week you could have never convinced me that you could get a plane neutral in knife edge without giving up something....well I officially stand corrected :-)  They know their stuff, were right on the money and the Twister goes pretty much anywhere you point it now without mixing (except a bit on downline but I think I can get rid of that).

I gotta say thanks to Bryan and Nat for their help, they were bang on, and I would suggest to anyone that you give their suggestions and honest try, I bet you are more than happy with the results!

Chad

Hey guys,

Well finally got out flying, good thing too since I am off to NY state
again on Monday :-(

So, here is where I was, I broke down and bought an inclinometer so I
could actually measure the plane directly....since I am too lazy to do
trig.

Engine, as molded is -2.5 but I was at -3.5, wing +0.8, stab +0.1.

So I got as much of the down out of it as possible which leaves me at -1,
I can't do any more without shimming the motor further out for more
clearance spinner to nose ring.  I put the wing back to +0.5 and left the
stab alone.

First flight today, removed the left rudder KE mix I had (had none on
right rudder), and downline mix.
- Plane needed a bit of down trim for level, but was pretty close
- Uplines went to the canopy
- 45 ups inverted pulled over the top fairly hard
- 45 downs upright were pretty decent but still dove a bit - recall this
was my major beef with previous setup
- knife was pulling to canopy both ways

Second flight - moved CG back as I have felt that it was too far forward
in general, and I think you would agree if you saw where it was.
- more down trim
- Uplines became very close
- knife both ways was pretty good, really solid with right rudder, and
very very close on left (slight belly pitch)...probably not worth mixing
out
- 45 downs upright were getting better
- downline mix reduced 2% from start
- 45 ups inverted better

Third flight - took out 1/2 turn of incidence, which by trig should put me
at 0.41+ on the wings
- uplines became perfect, or really close...would need more flights in
various conditions to nail
- everything else was really close

Fourth flight - decided to adjust stab since I was carrying a little up
elevator, so I took 1/2 turn out of adjuster which should being it close
to 0
- this pretty much sealed it
- uplines are as before, very very close
- no KE mix - even in the KE loop at high deflections its really, really
good
- took another 1% out of my downline mix (I am at 2%, started at 5%)
- 45 ups inverted are really good, just a slight arc over the top
- 45 down upright is finally straight.

I need to spend some more time on it to really get a good feel, but I
think the downthrust was causing a lot of problems to this plane.  I have
never had it in all aspects of flight this close yet.  I am anxious to get
more time on it and see if the changes really stick.  Unfortunately on
Sunday this plane is going to a buddy but I plan on incorporating all
these changes on the new Twister which is why I wanted to get it figured
out now :)

Any further comments?  CG is probably around 33% of MAC, but to be exact I
would have to calculate.

Upline snaps are as you say Bryan, on axis with no need to lead....I was
pretty happy to see that result :)

Chad


> > > From: "Chad Northeast" <chadnortheast at shaw.ca>
> > > To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> > > Sent: Monday, March 10, 2008 4:57 PM
> > > Subject: Re: [NSRCA-discussion] the joy of trim
> > >
> > >
> > > > Ok you trim masters, here is a tricky one for you.
> > > >
> > > > Bryan and I have been through this a bit last year but I
> ran out of
> > time
> > > > before the Worlds to fix it and just flew with what I had.
> > > >
> > > > On my Twister I have this pesky problem, the setup is like so,
> > > >
> > > > wing = 1/2+ Bryans suggestion and I like it
> > > > stab = 0
> > > > motor = factory claims 2.5 down, have not measured but
> could if asked,
> > I
> > > > have added more to cure a problem see below
> > > > CG = has been anywhere from 275 to 300mm from TE mostly
> with the same
> > > > result.  Currently its around 285-290 and it feels
> good at that point.
> >  45
> > > > ups inverted track almost hands off if under enough power.
> > > >
> > > > Symptoms,
> > > >
> > > > Plane flies well, at this setup I need 0 mix right rudder
> to ele in
> > knife,
> > > > and about 2% up ele with left rudder in knife,
> > > > about 1/32" down elevator with idle to fix a downline
> > > > Added downthrust as the increase in wing inc. and more
> forward CG
> > really
> > > > helped the mix in knife and made rollers easier, but
> forced an
> > increase in
> > > > downthrust as the plane started pulling to the canopy on
> uplines.> > > Downline mix remained the same.
> > > >
> > > > The big problem I cannot resolve is this, a 45 deg down
> upright (motor
> > at
> > > > idle) the plane pitches to the belly and will not track on
> its own for
> > any
> > > > length of time.  If I switch the idle-down mix off
> its rock solid on
> > that
> > > > line.
> > > >
> > > > I am open to all suggestions now that I have a bit of time
> to play
> > with
> > > > this, I hope Bryan chimes in some more as I would like to
> continue> where
> > > > we left off last fall.  If you suggest something I
> will do my best to
> > give
> > > > it a go and let you know how it works (provided it doesn't
> snow!)> > >
> > > > The plane is basically super locked in with this setup,
> except for the
> > > > silly 45 down upright, which is a problem in cubans and such.
> > > >
> > > > Comments and thoughts from the masters are most
> appreciated :)  I
> > consider
> > > > myself one of the, cant really trim that well but can fly
> through it
> > just
> > > > fine types :)
> > > >
> > > > Chad
> > > >
> > > > _______________________________________________
> > > > NSRCA-discussion mailing list
> > > > NSRCA-discussion at lists.nsrca.org
> > > > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
> > >