[NSRCA-discussion] triangulation trimming
shinden1 at cox.net
shinden1 at cox.net
Tue Mar 11 19:06:20 AKDT 2008
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 <G> 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 <see my reply to Chad>
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 <G>
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 <donramsey at gmail.com> 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, <shinden1 at cox.net> <shinden1 at cox.net>
> 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 <G>
> >
> > ---- Nat Penton <natpenton at centurytel.net> 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" <chadnortheast at shaw.ca>
> >> To: "NSRCA Mailing List" <nsrca-discussion at lists.f3a.us>
> >> 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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