[NSRCA-discussion] triangulation trimming

[krishlan fitzsimmons]

I'm fine with that also.
   
  Thanks, 
   
  C

Matthew Frederick <mjfrederick at cox.net> wrote:
  Chris and Bryan,

I'd be happy to help edit this for a K-Factor issue. Since I fly with Bryan 
I have a good insight to his thought process, and it would be easy for me to 
clean this up.

Matt
----- Original Message ----- 
From: 
To: "NSRCA Mailing List" 
Sent: Tuesday, March 11, 2008 10:05 PM
Subject: [NSRCA-discussion] triangulation trimming


> triangulation trimming,
> this is going to be long winded,
> I want to preface this discussion by saying I have learned a great deal 
> from Dean Pappas one of my hero`s in the sport,,Jim Oddino I read these 
> guys all the time ,,Nat Penton ,,I learned a great deal about painting 
> from Mike Harrison who is always willing to tell you what he knows and
> I have looked up to Earl Haury as an all around Teacher and appreciate 
> those guys for their hard work in the sport ahead of me and willingness 
> to share what they know.
> Now let me say I am no flight engineer or aerodynamic Guru , I`ll leave 
> that title to Nat Penton as he deserves it, But the two guys that started 
> this flying madness were,, by cycle mechanics,as we all know .
> so I`m in good company
> After trimming over 15 of my own designs and trimming and building two 
> or three airplanes a year for about 20 years I have a lot of practical 
> knowledge on this subject matter and have kept notes. to verify my 
> observations I hope this will help.
> A better Flyer with more experience will be a better trimmer because he 
> demands more from his airplane ,,but being a better trimmer will earn you 
> better flying skills .
> so here we go
> Mike ,Keith, Jim and Don, thank you for your patience
>
> For the purpose of this discussion tail heavy nose heavy is relative to 
> the recommended C/G and not always an extreme position just a way to 
> example it.
>
> If you are using a 0-0 setup things may- be alittle different as to what I 
> say and what you see on your airplanes as you fly them
> my set up and your set up are not to be equated with each other.
> and I think that's where some of the confusion comes in you having only 
> experienced your set ups.
> However ,,left rudder tuck is a symptom of the airplane being tail heavy 
> on all pattern models no matter the set up, as long as the stab and 
> elevators are accurately adjusted , Extreme tail heavy will mean both 
> knifes will tuck to the belly. it is just a symptom that tells me the cure 
> and allows me to diagnose trim problems 
> Jim O,
> Any wing has to produce lift, to fly and there are two ways to do it, add 
> pos inc to the wing according to the datum line on the fuse My Method 
> or,, add pos inc to the fuse, the 0-0 method ,,,by this I mean , flying 
> the airplane a little tail heavy to achieve pos inc ,, there is no way 
> around it ,the wing has to have a pos angle of attack to produce lift and 
> fly level and lift 11 pounds of balsa and Glass.
> vertical c/g has no factor on this discussion I don`t understand enough 
> about it to discuss it,{G}
> The stab does not induce the lift ,,it controls the lift of the wing and 
> steers the wing and fuse. {no arguments here please I`m trying to make 
> the bigger picture I know it does contribute lift and share the lift 
> load,}
>
> A ,0-0 or sub 1/2pos set up will cause some or all of these problems 
> ,,for you guys set up 0-0 ,, check um off ,,,
> A tuck to the belly on left rudder {or both depending on how tail heavy} 
> more tail heavy more tuck ,,pull in both up and down lines ,,,So now we 
> add down thrust to fix one problem upline pull { as as Jim and others 
> observed and suggested } and it magnifies the others. like Nat explained 
> to Chad ,,,and now it may give a differential problem . so we address 
> that with the radio.by mixing
> and this occurs,,
> stalls may be hard to do because,, "mix dont go away ", Snaps and spins 
> are hard to perform correctly start,,stop consistently ,and they wander 
> off line in the uplines,and 4/5`s so you see flyers using opposite rudder 
> to lead before, and after to keep them on line , and even more apparently 
> worse in a upline ,,, you can`t convince these guys that it`s possible 
> to do a snap without displacing or tucking ect, because they have never 
> experienced it. and it supports their lack of trimming skills
> or a poor design ,Sorry Guys!!
>
>
> ,,BTW contrary to popular belief nose heavy airplanes {weight forward } 
> snap better, lands the snap cleaner, and is perfectly consistently ,stays 
> on line way better , { do you have an airplane you have to lead to 
> stop ,,its because it does not recover from the stalled condition its 
> probably tail heavy } a nose heavy { weight forward} set up stops 
> instantly . providing you have the right inputs.
>
> In windy weather the 0-0 or sub 1/2 Pos. airplane moves all over the 
> place and is not solid at all. its not directionally stable , because of 
> the tail weight needed to induce the pos inc in the wing.
> a positive set up will actually weather vein into the wind by itself and 
> you will need opposite rudder to maintain the line sometimes ,,in other 
> words it will self correct in the wind ,,this makes it much easier to fly 
> in windy weather.
> now ,,,
> every year designers go back to the drawing boards and play with 
> airfoils, tail moments ,,tail size ,,,hocus pocus ,,ect all in an attempt 
> to fix a trim problem.,, not a design problem.
>
> Now to this,,, to correctly trim a model you need three tools,
>
> #1 an incidence meter no matter what kind dig. may be better,,
> #2 honesty without it you will deceive yourself into believing it`s 
> trimmed
> #3 patience ,,,,I know I just lost some of you But ,
> there is only one of these three you can do without ,,, it`s the inc. 
> meter,, the other two will guide you if you stay at it till it`s right.
>
> Now the Hebert triangulation Method
> assuming everything else is perfectly straight and aligned correctly ,,, 
> this is a big assumption , but,set your c/g according to the design spec 
> on the drawings for your design as a starting point ,,,if you don`t have 
> a C/G spec contact Nat Penton, he will give you a great formula he has 
> worked up.
> # 1 set motor at 1/2 deg down ..neg inc.
> wings at 1/2 pos to start ,,,this is not a hard deck
> stabs at 1/4 pos because this is about where you will end up.
> Line up all your control surfaces get them even, because we are going to 
> let the airplane tell us what to do to fix it later
>
> #2 fly the airplane trim hands off level flight,, don`t cheat ,,{I know a 
> lot of guys use a little down trim in upright flight to help with upline 
> pulls} it has to be hands off perfect then fly inverted to see if you 
> like the inverted elevator and the airplane feels solid and easy to hold 
> on a line . and then take notes.
> #3 pull a vertical line see what it does
> #4 put it straight down see how long it takes to pull out to the canopy
> #5 do a left rudder knife edge ,see if it`s straight no pull the entire 
> length of the field don`t cheat,,
> #6do a right rudder knife edge see if it`s straight same as above.
> This is the triangulation method I use to diagnose all trim problems with 
> any airplane I-MAC to pattern ,,wings are wings.
>
> #7 now land and see where the elevator wound up ,,,never mind the stabs 
> right now, we will adjust them later.
> take notes of what the airplane did in all these three maneuvers, you 
> will see you can triangulate a common input fix, I find it help full to 
> have a buddy to help remember whats happening in the air.
> Look at the elevator trim and see what it has in it, if we are lucky and 
> your airplane is 10 pounds you are "all over it" and it just may take a 
> little c/g to give a click or two one way or the other.
> #1 But, if it pulls in the up lines and downline you need more pos inc 
> one turn at a time on the adjuster ,,
> As an aside ,,,,if you have rear adjusters take them out and put pins and 
> donuts make sure they do not move at all as this will mess with the trim 
> process ,,I find the rear adjusters being a different distance for the 
> wing tube take different amounts of turns to be equal and the wings have 
> to adjust perfectly and lock exactly. no warp in the root., yes it 
> happens and gives you a false reading.
>
> #2 if it goes to the belly in left rudder move the c/g forward{ your tail 
> heavy} untill it stops pulling to the belly regardless of the inc.
> if it goes to the canopy in both knifes #1 will probably fix it 
> but
> refer to the inverted flight part of you notes and see if you
> think the elevator was mushy ,hold able but mushy and you might
> require tail weight. and pos inc. to fix both problems canopy pull 
> downlines and knife edge flight.
>
> Because we are on the edge of trim perfection now in all wing loaded, and 
> unloaded ,positions now we can adjust c/g by using the earlier mentioned 
> bullet points for fine tune feeling
> Remember most of the time one fix will fix 3other things and bring it all 
> together because they are all related, thats why a well trimmed airplane 
> rolls with ease and 4 points with ease. because we are not fighting any 
> adverse trim issues in any axis. or wing load
>
> Now do the adjustments and leave the trims on the airplane like they are
> make another flight your adjustments should Jive with the reverse of what 
> you trimmed on the first flight and make your trims work ,,, if you have 
> to increase the trim you already have in there from the first flight LAND 
> you went the wrong way with the adjustments and make your corrections 
> again
>
> < on another side note > for my designs since I know where they should be 
> set ,a quick method is to do the triangulation method this way ,, trim 
> the airplane to fly the down lines,,, leave this trim in and land ,,
> then adjust the wings to get the trim out and all three Maneuvers are now 
> happy,,,
>
> The closer you get to the end, the finer the tuning will need to be, and 
> it can try your patience
> make sure the tank is centered on the c/g or you will have trim changes 
> during the flight as the tank drains
>
> don`t get mad at me if you cannot fix your favorite airplane Just buy a 
> better design ,,,,Mine preferably 
> there is so much more that I could add But I`ll leave it alone for another 
> post.
> However I would like to add this ,,
> I agree with Nat that add on T wings are smoke and mirrors However who is 
> going to argue with the word Champion ,,
> yes it does work ,,somewhat, it reduces the required rudder angle needed 
> to hold knife edges which will in fact reduce mix ,,less rudder less mix 
> ,, A POS setup needs none of this.
> Hope this helped ,,you may need to read it twice to absorb it all
> thanks for your interest ,However Brian Clemons is mad at me because I was 
> supposed to be painting his airplane tonight LOL
> Bryan
>
> Chris F. if you Like you can clean this up and include it for a k-factor 
> issue
>
>
>
>
>
>
>
>
> ---- Don Ramsey wrote:
>> I'm with Jim in not understand the reason some of the incidence changes
>> work. Consider increasing the incidence for adjusting the push to the 
>> belly
>> in knife edge. My reasoning would be; increase the incidence, put in 
>> some
>> down elevator to fly straight and level. Roll to knife edge and the 
>> model
>> would then push to the belly more severely. What am I missing?
>>
>> Don
>>
>> -----Original Message-----
>> From: nsrca-discussion-bounces at lists.nsrca.org
>> [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of James 
>> Oddino
>> Sent: Tuesday, March 11, 2008 10:59 AM
>> To: NSRCA Mailing List
>> Subject: Re: [NSRCA-discussion] the joy of trimming , left rudder tuck
>> downline pulls
>>
>> Bryan,
>>
>> I'm trying to figure out how increasing the wing incidence, I assume
>> with respect to the fuselage, will get rid of a pull to the canopy on
>> a vertical downline. Is it because you need to crank in some down
>> trim to make it fly level? Or is it because the tail flies higher in
>> level flight and the higher vertical cg creates a couple pushing the
>> nose down during the vertical downline?
>>
>> I assume that if one could achieve a good vertical downline with power
>> off, he could then adjust the thrust to get a good vertical upline?
>> It would seem that the thrust is part of what made it fly level and
>> you would get into an endless loop chasing things around. What is the
>> sequence for getting what you want?
>>
>> I adjust the relation between the downthrust and wing to get a good
>> vertical upline and trim out the pull in the downline like Chad. Tell
>> us how we can get a combination of vertical up with power, level with
>> power (less power?) and vertical down without power that are all good
>> without throttle to elevator trim.
>>
>> Jim O
>>
>>
>> On Mar 10, 2008, at 5:31 PM, 
>> wrote:
>>
>> > Chad having a small tuck to the belly on left rudder only,,
>> > is always a result in a little too much tail weight ,,providing
>> > the stab halves and elevator halves are correct.
>> > thats whats happening in your wandering 4/5`s
>> > the tail weight as is ,,is making you add a little down elevator
>> > trim because the wing is flying a little more positive.
>> > You want to create the pos angle of attack with the wing only use
>> > the tail weight only to adjust the feel for rolls and inverted flight.
>> > engine thrust is contributory But ,not doing anything in the left
>> > knife edge.
>> > it would be happening in the right rudder too.
>> > sorry Nat..
>> > approach it like this, before you reset the down thrust ,,,because
>> > we want to know what really fixed it
>> > increase the wing inc 1/32 " more positive or till it stopps
>> > pulling in the downline , some airplane require the wing more than
>> > 1/2 deg depending on weight and airfoils 1/2 pos. is not a hard
>> > deck and you will have to move the cg forward to remove the left
>> > rudder knife mix ,,move it till you find a sweet spot , between
>> > downlines and both knife edges.
>> > , Always remember tail heavy makes the elevator and rudder
>> > sensitive and nose wweightmakes them a little numb but much more
>> > effective
>> > your spins,snaps entry and exits ,, up and downline,45`s will be
>> > corrected
>> > you will also see improvement in the wind due to the forward c/g and
>> > pos inc. add pos wing inc till it stops pulling to the canopy in the
>> > downs
>> > and let us know what happens
>> > Bryan
>> > darn now I have given away the family secrets ,And
>> > I have just made it harder to beat Chad 
>> >
>> > ---- Nat Penton wrote:
>> >> Chad
>> >> Your problem is caused by the large difference between T/L and
>> >> wing. Reduce
>> >> the downthrust by 1 deg and reduce the wing incidence by 1 deg ,
>> >> and test.
>> >>
>> >> We will go from there.
>> >>
>> >> Your excess downthrust requires up elev trim when under power. You
>> >> need to
>> >> adjust wing and T/L to avoid other problems. If you just lower the
>> >> wing inc
>> >> it will go to the belly in knife. If you just reduce the D/T it
>> >> will go to
>> >> the canopy in
>> >> knife. Nat
>> >>
>> >> ----- Original Message -----
>> >> 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 = 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
>> >>>
>> >>
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