[NSRCA-discussion] triangulation trimming
James Oddino
joddino at socal.rr.com
Thu Mar 13 12:41:26 AKDT 2008
Bryan,
Thanks for your effort. I agree with you almost completely on fix
#1. I'm not sure you can fix the down line. My Impact was pulling to
the canopy in both up line and down line. I kept adjusting the wing
positive until I fixed the up line. I had some remaining pull in the
down line and put in a small amount of down trim with low throttle to
take care of that. I'm not sure if I had gone further it would have
fixed the down line without screwing up the up line. I analyzed this
as increasing the down thrust. I didn't want to change the motor
angle so I changed the wing. Make sense. The wing was going to fly
at the same incidence with respect to horizontal but the motor would
be more negative in level flight, Right? The Impact didn't need any
serious mix for knife edge and I'm not sure one could prove anything
with it because the wings were like a propeller. Anyway that plane is
now a test bed.
My Abbra seems to fly great with the factory settings in up lines and
again I use a small amount of down trim with low throttle to fix the
downlines. I have the cg ahead of the factory recommendation but not
near as forward as Jerry Budd. I'm guessing that he has more positive
in his wing from the factory. I do fly with a little down trim at
neutral. The bad news is it takes lots of up mix to fix the knife
edges. I guess your solution would be to move the cg forward which in
turn would require more positive incidence? I hesitate to modify the
airplane to make the wing adjustable until I'm pretty sure I can
improve it.
Thanks again for making us think about this stuff, Jim
On Mar 11, 2008, at 8:05 PM, <shinden1 at cox.net> <shinden1 at cox.net>
wrote:
> 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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