[NSRCA-discussion] the joy of trim

Sat Mar 8 19:44:03 AKST 2008

Wow, that's pretty interesting. I'm going to try some of the things you mention here Bryan. 
  I thought we were all shooting for 1.5 degrees or so of down thrust, .5 degrees of wing incidence. I do agree, I feel like my Abbra has too much down thrust.. A little more up would help with a few things that I can now see. 
  Back to the garage.. 

  Thanks, 

Chris

shinden1 at cox.net wrote:
  thanks Lance 
we all know I`m a terrible writer and thats part of my reasoning here
I have great respect for Matt and his abilities he is a great modeler and designer. 
I am trying to use past experience when helping with these issues as a guide to how far out of line these things can get because of a misunderstanding that leads into a poor fix 
or a modeler who is not up to the task and trys to take the shortcut ,,,there are no shortcuts
I would be willing to bet 98% of pattern fliers don`t even know what their down thust is and have never measured it. 1deg down is a lot.
and most could not find a baseline to start with as a watermark for later measurements
I was trying to point out that it should be a method of fine tuning rather than using it to steer a wayward airplane into submission.
The wing is the most important ,powerful and effective way to adjust flight path ,,, airfoil ,stab placement , engine thrust ,,are way down the list in importance as seen with a foamy,,

First things first ,,get the wing inc right THEN,, the ac/g ..you would be surprised at how for off you can fly c/g and get away with it ,,,
What Matt and I call pulling to the Canopy and what Joe Blow calles it i`m sure ,, are two different things.{BTW I would bet most of the fliers out there with differential fix problems ,,are there becuase of an up line pull,
usually because your flying a tail heavy airplane } if ou use tail weight to create a pos angle of attack lots of little problems arise you have to use inc to creat the lift and C/g to adjust the feel
earlier I was trying to make the bigger picture nothing against what Matt was offering ,,,,

I disagree there is more than one way to trim there is only one way 
our accepted outcome is the difference 
I would like to say I`m probably more hard headed than the Next guy , so I stick to my guns till proven wrong but accept it when I can be proven wrong,, ,, after designing over 15 pattern airplanes and keeping notes ,,, my outcome notes all say the same thing in the end ,it never changes ,,even when I get a bright idea to change or tweak the setup it leads me back to where I started. 
After watching Arch fly his Black magic in the bumpy 25mph winds in Crowly La. A smoking performance ,,,I might add 
the BM appeared to be on rails then,,watching my own airplane dance around I realized something I knew But had ignored ,,,it made me go back to the notes where I found the answer ,,, it never changed!! 
the BM was a great design Properly trimmed BUT,
I,, had been trying to adjust upline canopy pull with engine thrust and tail weight ,,,,I don`t have the Luxury of calling the designer and asking where to put the C/G and wing Inc ,,,I have to find it 
when I realized it needed more wing inc less tail weight and less down thrust it reaffirmed my notes and when the next time I flew in those conditions it proved me right you have to balance all these things 
The airplane flys around the wing ,,,,let the airplane talk to you ,,be honest in you evaluations accept nothing but absolute perfection it is attainable 

would anyone like to try an onlist diagnosis of their airplane?
you tell me the Set up ,,they must be very Accurate give me the Symptoms ,,and I`ll provide the cure
you tell us what is happening with the input ,,,BEWARE it can be tedious and it might include using a saw!!
any takers ??
Bryan
sorry to be so longwinded 
---- Lance Van Nostrand 
wrote: 
> Bryan,
I have been anticipating your response but now it seems it won't be coming 
soon. Maybe we can take this offline. There's no way anyone could 
interpret my response as being argumentative and I know your are tough 
enough to take a few pin pricks without flinching. Certainly I have my own 
experiences and opinions but those are completely set aside. I believe 
there are always at least 10 correct answers to any modeling question but 
each answer is right within its own context.

In other words, I start from 0-0 and have my trim process advance from there 
and usually get very good results. I think, if I remember correctly your 
old KF article and our live discussions, you start from 1/2 degree positive 
inc in wing and stab and advance from there. Since I know your path is 
different from mine I am trying to learn from you. this is why I question 
and ask for deeper explanation. Maybe it's just not there. The answer 
might be "I never tested in a wind tunnel, can't explain why it works, but 
it does so just try it and enjoy." But I hate to see you bow out when 
someone asks for more details. that makes Krishlan's comment seem relevant 
when, knowing how much you help others and contribute to this sport, it 
shouldn't be.

--Lance

----- Original Message ----- 
From: 
To: "NSRCA Mailing List" 
Sent: Saturday, March 08, 2008 5:32 PM
Subject: Re: [NSRCA-discussion] the joy of trim

> Ok Matt
> I accept, your probably right ..
>
> I will now bow out of the discussion it`s not going anywhere and I`m 
> waiting my time trying to inform, it seems all the people I`ve helped 
> accomplish what I`m preaching have quit the sport or they are scared to 
> write !!
> I`ll leave you with this ,
> demand of perfection is different by each persons ability and goals,
> sometimes we deceive ourselves in thinking we kow it all or
> we get caught up in out wording every one and talking nonsense ,, then no 
> one gets anything out of the conversation
> and then, you die of a thousand pin pricks
> I can remember sharing pos inc setup with Nat on numerous occasions and 
> Nat out worded me and proved me wrong on paper and you know he can ,, in a 
> Popeye Fried chicken House of all places,
> However I find out years Later he now uses My setup I`m proud 
> ok ,I`ll stop beating a dead horse I know better than to start this
>
> carry on
> Bryan
>
> ---- rcmaster199 at aol.com wrote:
>> Bryan,
>>
>>
>>
>>
>>
>> I respectfully disagree on the upline, full power issue. The downline is 
>> a totally different trim situation because the vectors involved are 
>> different
>>
>>
>>
>>
>>
>> MattK
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>>
>> From: Nat Penton
>>
>> To: NSRCA Mailing List
>>
>> Sent: Fri, 7 Mar 2008 7:16 pm
>>
>> Subject: Re: [NSRCA-discussion] the joy of trim
>>
>>
>>
>>
>>
>> I'm thinking, I'm thinking ----- Original Message ----- From: 
>> shinden1 at cox.net> To: "NSRCA Mailing List" 
>> nsrca-discussion at lists.f3a.us> Sent: Friday, March 07, 2008 1:53 PM 
>> Subject: [NSRCA-discussion] the joy of trim > Matt, I refer back to 
>> my earlier post > thrust is not the issue. > wing inc. will always 
>> trump thrust,, in power and influence over vertical > lines. > thrust 
>> is a" very fine tune" issue it should not be used to adjust > tracking 
>> issues > > jump in Nat ,, why do you not need down thrust on your 
>> design?? > Bryan > ---- rcmaster199 at aol.com wrote: >> If the model 
>> pulls to canopy on aï¿½FULL POWERï¿½vertical upline and you >> reduce 
>> downthrust, the problem will worsen. You need to add downthrust >> 
>> (about 1 degree initially, and more if needed). I would not mess with CG, 
>> >> at least not yet. >> >> >> ï¿½ >> >> >> Horizontal flight places 
>> quite a load on the wing....the wing must lift >> the load accordingly. 
>> Vertical flight removes the load therefore whatever >> trim was found 
>> in horizontal flight will affect the vertical flight. The >> simplest 
>> fix is downthrust addition for the condition Mike references, >> but 
>> assumes that the model is close to begin with. >> >> >> ï¿½ >> >> >> 
>> Downline flight (NO POWER) is a totally different trim scenario and may 
>> >> indeed require wing/stab inc adjustment and CG adjustment. >> >> >> 
>> ï¿½ >> >> >> It should be understoodï¿½that it is an iterative process to 
>> get "perfect" >> trim. >> >> >> ï¿½ >> >> >> MattK >> >> >> >> 
>> >> >> >> >> >> >> >> -----Original Message----- >> >> From: J N 
>> Hiller >> >> To: NSRCA Mailing List >> >> Sent: Fri, 7 Mar 2008 11:33 
>> am >> >> Subject: Re: [NSRCA-discussion] YS Questions+more - Rolls >> 
>> >> >> >> >> >> >> >> >> >> >> >> The airplane may be flying 
>> with positive trim. Try reducing the down >> thrust or move the CG 
>> back. >> >> >> If it doesnt help put it back. >> >> >> Jim Hiller 
>> >> >> >> ï¿½ >> >> >> -----Original Message----- >> >> From: 
>> nsrca-discussion-bounces at lists.nsrca.org >> 
>> [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Michael 
>> >> Wickizer >> >> Sent: Friday, March 07, 2008 8:19 AM >> >> To: 
>> NSRCA Mailing List >> >> Subject: Re: [NSRCA-discussion] YS 
>> Questions+more - Rolls >> >> >> ï¿½ >> >> >> Bryan: >> >> ï¿½ >> >> 
>> I agree that the plane doesn't know which direction it's flying, but then 
>> >> why will a plane fly straight and level then pull to the canopy in 
>> >> uplines?ï¿½ This has been driving Brett and me crazy for over a year.ï¿½ 
>> >> Admittedly, it a much shorter drive for me:) >> >> ï¿½ >> >> Mike 
>> >> >> >> >> >> >> >> >> >> >> >> >> >> >> > Date: Thu, 6 Mar 
>> 2008 23:13:48 -0500 >> >> > From: shinden1 at cox.net >> >> > To: 
>> nsrca-discussion at lists.nsrca.org >> >> > Subject: Re: 
>> [NSRCA-discussion] YS Questions+more - Rolls >> >> > >> >> > Chris ,, 
>> the airplane does not know it`s flying horizontal or vertical >> >> > 
>> the wings are still lifting whether up or down that s why we can use >> 
>> > the vertical up or down to test this problem , >> >> > Bryan >> >> 
>> > ---- krishlan fitzsimmons homeremodeling2003 at yahoo.com> wrote: >> >> 
>> > > Lance, >> >> > > >> >> > > Just a thought though, if going 
>> straight up, up straight down, aren't >> > > the up and down ailerons 
>> both inducing equal drag, no lift? I've >> > > often wondered if our 
>> straight up test is actually a perfect test for >> > > this. It is for 
>> our up and down lines, but what about our 45's or >> > > horizontals 
>> where we do indeed have lift on the low aileron and drag >> > > on the 
>> other? This would create a different condition I'm guessing.. >> > > 
>> Probably small, but still a little different because as I mention, >> > 
>> > both create drag on the up or downline.. Still, it's the best test we 
>> >> > > have I guess.. >> >> > > >> >> > > Chris >> >> > > >> >> > 
>> > Lance Van Nostrand patterndude at tx.rr.com> wrote: >> >> > > This 
>> thread is timely because I've been experimenting with >> > > 
>> differential >> >> > > recently on a new design that seems to need it. 
>> Never needed it >> > > before on a >> >> > > pattern plane but now I 
>> might. My test is to fly very high, point the >> > > nose >> >> > > 
>> directly at the ground and roll pure aileron. Plane should be axial, >> 
>> > > but >> >> > > remember that axial is along the vertical CG, which 
>> may not be a line >> > > that >> >> > > pierces the wing LE/TE. You 
>> need to do it a few times to be sure that >> > > their >> >> > > is 
>> an axis that everything rotates around and that line is straight. >> > 
>> > If it >> >> > > wobbles, then we have an issue. Another way to 
>> determine this is to >> > > do >> >> > > unlimited rolls while flying 
>> straight up. If the airplane >> > > consistently arcs >> >> > > off 
>> its vertical line, you have a problem. >> >> > > >> >> > > 
>> Aerodynamics suggests two contributors. One is that the lowered >> > > 
>> aileron >> >> > > increases the lift of the airfoil and lift creates 
>> drag so this wing >> > > may >> >> > > pull the plane off axis. the 
>> other is that the spiral slipstream of >> > > the prop >> >> > > is 
>> pushing down on the right wing and up on the left so up/right >> > > 
>> aileron is >> >> > > more effective than up/left and down/left is more 
>> effective than >> > > down/right. >> >> > > >> >> > > The overall 
>> effect for most pattern planes is minimal and usually >> > > ignorable, 
>> >> >> > > but on IMAC style planes these factors can be significant and 
>> the >> > > resulting >> >> > > differential corrections may need to 
>> be adjusted with something as >> > > simple as >> >> > > a prop 
>> change (from 3 blade to 2 for example). >> >> > > >> >> > > the 
>> correction of course is to start playing with aileron >> > > 
>> differential. >> >> > > Given the contributors I've suggested, its not 
>> a given which way you >> > > go with >> >> > > the differential to 
>> correct the problem and the answer might not even >> > > be >> >> > > 
>> symmetrical. >> >> > > >> >> > > Note that contributor #1 above will 
>> change if you are flying upright >> > > or >> >> > > inverted, so it 
>> would seem that a correction for upright flight would >> > > simply >> 
>> >> > > exacerbate inverted flight, but contributor #2 is the same for any 
>> >> > > flight >> >> > > mode but is throttle dependent. >> >> > > >> 
>> >> > > --Lance >> >> > > >> >> > > ----- Original Message ----- >> 
>> >> > > From: "Koenig, Tom" >> >> > > To: "NSRCA Mailing List" >> >> > 
>> > Sent: Thursday, March 06, 2008 4:45 PM >> >> > > Subject: Re: 
>> [NSRCA-discussion] YS Questions+more - Rolls >> >> > > >> >> > > >> 
>> >> > > > My head is spinning!!! The more I think about this, the more 
>> >> > > > questions I >> >> > > > have.........rather than answers! >> 
>> >> > > > >> >> > > > Maybe the contra rotating prop set up on a Voodoo 
>> X( Nat??) maybe >> > > > the >> >> > > > answer?? >> >> > > > >> 
>> >> > > > I still 'feel', that the best rolls I get are with a 0 
>> differential >> > > > set >> >> > > > up-BUT- somehow I 'drive' that 
>> wing to 0 ( or should that be some >> > > > sort >> >> > > > of 
>> equilibrium??) during the rolls. Certainly in my case, it seems >> > > 
>> > to be >> >> > > > Pilot dependant!!! >> >> > > > I'm starting to 
>> think that my rudder control has turned to the >> >> > > > proverbial 
>> trying to micro analyse what's happening! >> >> > > > >> >> > > > Tom 
>> >> >> > > > >> >> > > > -----Original Message----- >> >> > > > From: 
>> nsrca-discussion-bounces at lists.nsrca.org >> >> > > > 
>> [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of >> >> > 
>> > > shinden1 at cox.net >> >> > > > Sent: Friday, 7 March 2008 9:15 AM >> 
>> >> > > > To: NSRCA Mailing List >> >> > > > Subject: Re: 
>> [NSRCA-discussion] YS Questions+more - Rolls >> >> > > > >> >> > > > 
>> what happens on a 4piont? >> >> > > > Bryan >> >> > > > ---- Del 
>> Rykert wrote: >> >> > > >> The general consensus has been that the 
>> faster moving molecules >> > > >> over >> >> > > > the top surface 
>> don't require as big as a deflection as the aileron >> > > > that >> 
>> >> > > > deflects towards the bottom of the plane. What one tries to 
>> achieve >> > > > is >> >> > > > the plane tracks as purely straight 
>> on a string as possible while >> > > > one >> >> > > > rolls both 
>> directions without introducing any yaw. >> >> > > >> >> >> > > >> Del 
>> >> >> > > >> >> >> > > >> ----- Original Message ----- >> >> > > >> 
>> From: >> >> > > >> To: "NSRCA Mailing List" >> >> > > >> Sent: 
>> Thursday, March 06, 2008 2:49 PM >> >> > > >> Subject: Re: 
>> [NSRCA-discussion] YS Questions+more - Rolls >> >> > > >> >> >> > > 
>> >> >> >> > > >> > Nat and all you other aerodynamicists, >> >> > > >> 
>> > >> >> > > >> > I thought that the rational for "aileron differential" 
>> was that >> >> > > > upward deflection causes more drag than downward 
>> deflection so to >> >> > > > equalize drag and prevent yaw with aileron 
>> deflection, aileron >> >> > > > differential is needed. It seems that 
>> you guys are now saying that >> >> > > > ain't so. Please elaborate. 
>> >> >> > > >> > >> >> > > >> > George >> >> > > >> > >> >> > > >> 
>> > ---- Nat Penton wrote: >> >> > > >> > >> >> > > >> > ============= 
>> >> >> > > >> > IMO center hinged or top hinged is OK. With top hinge, to 
>> >> > > >> > achieve >> >> > > > equal vertical travel of the trailing 
>> edge requires different >> > > > angular >> >> > > > travel, up vs 
>> down. The objective is zero aerodynamic differential. >> >> > > >> > 
>> >> >> > > >> > Ron I don't think a fairing would prevent separation but, 
>> how >> > > >> > are >> >> > > > you able to fair the gap using the 
>> top hinge ? Nat >> >> > > >> > ----- Original Message ----- >> >> > > 
>> >> > From: ronlock at comcast.net >> >> > > >> > To: NSRCA Mailing List 
>> >> >> > > >> > Sent: Thursday, March 06, 2008 7:20 AM >> >> > > >> > 
>> Subject: Re: [NSRCA-discussion] YS Questions+more - Rolls >> >> > > >> 
>> > >> >> > > >> > >> >> > > >> > And while your at it, I'd appreciate 
>> some discussion of the >> > > >> > impact >> >> > > > of the top 
>> hinge system as seen on Viavat, and Prestige birds - >> > > > (top >> 
>> >> > > > hinged, with fairing that eliminates the gap at deflection) >> 
>> >> > > >> > >> >> > > >> > Thanks, Ron Lockhart >> >> > > >> > >> 
>> >> > > >> > -------------- Original message -------------- >> >> > > 
>> >> > From: vicenterc at comcast.net >> >> > > >> > >> >> > > >> > Nat, 
>> >> >> > > >> > >> >> > > >> > Could you explain why the differential 
>> should be different for >> >> > > > non-center hinged? I understand 
>> that the mechanical configuration >> > > > of >> >> > > > non-center 
>> hinged requires differential to obtain same travel in >> > > > both >> 
>> >> > > > directions. However, the travel up and down should be close to 
>> >> > > > equal. >> >> > > >> > >> >> > > >> > Thanks, >> >> > > >> 
>> > >> >> > > >> > -- >> >> > > >> > Vicente "Vince" Bortone >> >> > 
>> > >> > >> >> > > >> > -------------- Original message -------------- 
>> >> >> > > >> > From: "Nat Penton" >> >> > > >> > >> >> > > >> > Tom 
>> >> >> > > >> > It's just something that is peculiar to the Southern >> 
>> >> > > > Hemisphere. >> >> > > >> > >> >> > > >> > Changing wing 
>> incidence will not help. Unless things are really >> >> > > > screwed 
>> up , at our roll rates, centrifugal forces are too low to >> >> > > > 
>> cause a problem. You want zero differential, aero speaking ( same >> >> 
>> > > > up/down if center hinged ). >> >> > > >> > >> >> > > >> > I 
>> find the best check is the fast half-roll in the vertical up. >> >> > > 
>> > Regards Nat >> >> > > >> > ----- Original Message ----- >> >> > > 
>> >> > From: Koenig, Tom >> >> > > >> > To: NSRCA Mailing List >> >> > 
>> > >> > Sent: Wednesday, March 05, 2008 7:24 PM >> >> > > >> > Subject: 
>> Re: [NSRCA-discussion] YS Questions+more >> >> > > >> > >> >> > > >> 
>> > >> >> > > >> > Hi Troy! >> >> > > >> > >> >> > > >> > Thanks for 
>> the info. I thought you would be toiling away on >> >> > > > the next 
>> developmental stage of these engines!! >> >> > > >> > >> >> > > >> > 
>> Hopefully soon, I can find the time to get flying again. I am >> >> > > 
>> > looking forward to running this little beast. I am still a little >> 
>> >> > > > concerned in keeping it quiet though. >> >> > > >> > >> >> > 
>> > >> > Four blade props? I have some of the 18.1 x 12 two bladers >> >> 
>> > > > but I just cant see how I'll shut the thing up with these paint >> 
>> >> > > > stirrers?? >> >> > > >> > >> >> > > >> > Also-one more 
>> question to any of you out there in pattern >> >> > > > land. >> >> > 
>> > >> > >> >> > > >> > I have struggled with aileron differential for 
>> years. I am >> >> > > > just not happy with the rolls. I have tried 
>> various design >> > > > fixes-but >> >> > > > about the only one that 

=== message truncated ===

Chris 

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