[NSRCA-discussion] Joy of Trim

Thu Apr 17 21:02:47 AKDT 2008

Thanks for the reply Bryan.. I do appreciate your time.. 

  I forgot I added even more positive incidence to try to get rid of the pull in downlines.. 1 1/2 turns right before the contest. I didn't really like it so I changed it back today.. Flew much better. My plane (and all Abbra's that I have known so far) pulls pretty good to the belly in knife. My mix compensates for it nicely. But I'm not willing to accept that. I have my snaps set up how you recommend, and they now stay on a pretty nice line. Nicer than they ever have.. Stopping better than they ever have.. I had no problem at the contest with snaps.. Actually, the inverted snap I can't seem to land 100% of the time because I'm used to it over snapping a little. Which it doesn't do now.  The 45 down snap is pretty fast, but it lands perfect, and stay's on line easily.. 
  My inverted lines looked better today after I move the batts back a little. Snaps stayed good, inverted still had more stick than I'm used to.. But I'm getting used to it. My landings came in alot slower and didn't bounce at all. (I do think I went to far into the nose heavy range). I'm very happy with my spin entry also at this cg.. 
  I am 100% in agreement with you after today that there is too much positive in the wings.. Using your method, which I now keep with me, I went through every scenario of changes that I have done. I now feel my cg is perfect, I'm willing to leave it where it is. Now I will play with less incidence in the wing.. 
  I'll report back with my findings.. 

  I don't know if anyone finds this as interesting as me.. And, well, I'm actually enjoying what I'm learning.. Once, I though I knew how to set up a pattern plane.. I know I was wrong then.. Honesty, rule 2.. lol 

BTW, I saw a Shinden fly at the contest.. I can say I'm very impressed with the lines it fly's.. Very impressed.. 

  Thanks, 

C

shinden1 at cox.net wrote:
  Hey Cris
Ok lets review 
if your airplane pulls to the belly on both knife edges you have Either too much pos inc. in the wing or too much tail weight 
lets use the snaps and spins to figure this out 
snaps should be set up to only need about 12 deg up 14 deg down elevator 
15- 18 deg ail. 
low rate rudder Aprox 60% of full rate 
the airplane should snap, stay on line and instantly recover with no winding up or guessing the exit 
if you can`t control snap/spin exit with low rudder rate, your tail heavy 
if you can`t fly a dead solid inverted line your tail heavy 
if the airplane has any directional problems out of a down line to a radius ,,,tail heavy 

Nose heavy takes a lot of down elevator inverted 
It`s hard to get a "nose high" clean stall, for spins 
after a 1.5 snap to inverted the airplane deviates off line falling off the 45 line forcing you to catch it with elevator , Nose Heavy 
these are good indicators for detecting tail
nose Heavy.

now ,, 
Like I told you before don`t confuse what other people have in there set up ,,verses your set up because the inc in the main wing will cause you to be different in the end 
!/2 deg pos. is just a starting point .,,,
it may need more or less depending on ,,aircraft weight ,, 
Design ,, or wing size.

Now it sound to me,,,
like your too positive on the wings ,, you over compensating the extreme position of the pos inc .with nose weight and thats giving you just enough trim to pull in the downlines but the Extreme pos wing inc is causing you to have too much down elevator trim and creating the belly pull.

On the down thrust ,,,don`t put too much stock in moving this around anywhere from 0-one deg down won`t make any difference in your downlines and knife edge trim settings ,,,so,,, disregaurd this for the moment 
Start back at getting your knives to track as good as possible and remember what I told you ,,,
you may not be able to make this airplane mix free and will have to live with some mix ,,,
But don`t give up ,,,remember rule #3 Patience 

"lessons learned hard, are lessons not soon forgotten"

Everything you need to know is in the trim article. re read it carefully
with an open mind and Honesty about what your airplane is doing in everything,," something "will be a lead indicator.

I suggest you go back from scatch ,,, 1/2 pos. on the wing !/4 pos on the stab 
make darn sure the entire wing is moving when you adjust the front adjusters ,,,,like I said in the trim article ,,,, remove the rear adjusters and put pins and donuts ,,,, this is very important ,,warping the root to get a inaccurate reading is very common and can drive you crazy!!!
use 0-1/2 down on the engine 
AND 
re read the article carfully ,,if anything does not line up with the set up technique make the change and like Tom said ,,, 
Make sure you have a dead level uprite trim line 
no fudging 
I know it`s frustrating ,,,been there myself .
keep us informed I`ll do my best to respond to you 
sorry for the late reply ,,, I want to help you through this ,,,but most of all I want you to learn and be able to teach others
Bryan

---- krishlan fitzsimmons wrote: 
> Ok, back to this again.. 
> 
> Here's what I don't understand with the Triangulation theory.. The theory itself makes sense.. My plane doesn't unless my cg is way back still. It fly's very nose heavy now BTW.. 
> My plane still has the up ele trim in knifes, and still pulls to the canopy in downlines. I went a turn and a half more of positive in the wings and changed the thrust to zero (The thrust I am going to put back to 0.5) the day before the contest.. The mix remained the same, and it didn't help my downlines. But it did neutralize my ele trims from the up it had in it. 
> Now here's my problem, I am already more nose heavy than where everyone else has it, matter of fact, it's hard to slow it down to land, and it bounces on the gear which it never has before.. Now if I'm correct, my problems show me I need more positive in my wings and a more forward cg according to the triangulation. But if I do that, it will make my stabs go more negative (or down ele trim), which yes, will help my downlines, but won't it make it pull worse to the gear in knife? I already have 1/8 up ele mixed in it in knife. Granted, with an even more forward cg, that should help with the pull to the gear. Am I thinking correct here? 
> 
> It fly's right now like it's nose heavy and the differential in the roll is horrible.. 
> 
> Thanks 
> 
> Chris
> 
> 
> vicenterc at comcast.net wrote:
> Congratulation, you did very good. I don't think you are flying bad after getting that result. California lovely weather. I am tropical guy so I love 90 degrees. 
> 
> I flew yeserday but it was cold and windy. I could not do any detail trimming in that conditions. I am planing get the incidence at 0.8. Now is 0.6 and it was 0.4. Clearly, the effect of all this was to reduce the mixing. I am around 6% all around which is less than 0.5 degree movement of control surfaces. That is not that bad. The best cg position I have seen is between 0.6 to 1" in front of the front edge of the wing tube. The Abbra tail heavy tracks really bad. I did that test yesterday moving the batteries. 
> 
> It looks like the negative TL could be the problem. We need to get the TL and the incidence as close as possible. I think within 0.5 degree. I will do this next time and I will let you know. I am traveling this week so hopefully weather permitting I will try to fly next weekend. I think you need to measure were are you in incidence and TL relative to the belly pan floor. In this way we can get equivalent reference.
> 
> Thanks, 
> --
> Vicente "Vince" Bortone
> 
> -------------- Original message -------------- 
> From: krishlan fitzsimmons 
> Vicente, SNOW?????????
> Holy crap man.. At the Riverside contest today it was over 90.. I am pretty burned.. lol
> Did pretty good though, got a 3952 to Rusty Fried's 4000 out of 5 rounds... I'm pretty happy with that for how bad I seem to be fighting the plane..
> 
> As for the whole trim thing, well, where we left it last, the Abbra got a little more up thrust (1 washer) and a turn and a half more postive incidence for now as a test. It feels a little nose heavy now. Very bouncy on the gear on landing which it has never been before moving the cg. But the uplines and 45's looked good and felt good. Still has almost the same mixes in knife though. Downlines still pull to canopy. The ele now has neutral trim though.. 
> Just FYI.. 
> 
> Chris
> 
> vicenterc at comcast.net wrote:
> I wish that were breezy here. Weather has been really bad in Kansas this year. Well, mother nature always wins. We just to need patient, good weather is coming next week or so. Probably, I will have a chance to fly tomorrow afternoon. Today is cold and we are expecting snow.
> 
> Have a nice flying weekend,
> 
> --
> Vicente "Vince" Bortone
> 
> -------------- Original message -------------- 
> From: "Derek Koopowitz" 
> That is great news, Chad. I'm glad to hear that the issues got resolved.
> 
> I'm also very close on my setup... my stab is at 0 and the wings are almost +.5. The plane comes standard without downthrust and I have since added some to help with the pull to the canopy in the upline - its almost 100% but not quite. I think I may still be a little tail heavy and will add some nose weight when I get a day that is calm - it has been a little breezy here. Overall my plane is flying much better now as well.
> 
> 
> On Thu, Apr 10, 2008 at 8:56 AM, Chad Northeast wrote:
> 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 ! ! resul ts !
> 
> 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 pr! evi! ou s set up
> - 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 cl ose
> - 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 re! sult :) 
> C had
> 
> 
> > > > From: "Chad Northeast" 
> > > > To: "NSRCA Mailing List" 
> > > > 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 ! = facto ry cl! aims 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
> ! > fo rced 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
> > >! > & gt; it a go! and le t 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
> > > > > h ttp://lists.n! srca.or g/mailman/listinfo/nsrca-discussion
> > > >
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> 
> From: "Derek Koopowitz" 
> To: chad at f3acanada.org, "NSRCA Mailing List" 
> Subject: Re: [NSRCA-discussion] Joy of Trim
> Date: Fri, 11 Apr 2008 23:16:33 +0000
> 
> _______________________________________________
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> 
> From: krishlan fitzsimmons 
> To: NSRCA Mailing List 
> Subject: Re: [NSRCA-discussion] Joy of Trim
> Date: Mon, 14 Apr 2008 07:32:52 +0000
> 
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