[NSRCA-discussion] the joy of trim

[Nat Penton]

I'm thinking, I'm thinking <G>

----- 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 a�FULL POWER�vertical 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.
>>
>>
>> �
>>
>>
>> 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.
>>
>>
>> �
>>
>>
>> Downline flight (NO POWER) is a totally different trim scenario and may 
>> indeed require wing/stab inc adjustment and CG adjustment.
>>
>>
>> �
>>
>>
>> It should be understood�that it is an iterative process to get "perfect" 
>> trim.
>>
>>
>> �
>>
>>
>> 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
>>
>>
>> �
>>
>>
>> -----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
>>
>>
>> �
>>
>>
>> Bryan:
>>
>> �
>>
>> 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?� This has been driving Brett and me crazy for over a year.� 
>> Admittedly, it a much shorter drive for me:)
>>
>> �
>>
>> 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 seems to work is to get the wing back to 
>> > > > 0-0 (
>>
>> > > > which can be achieved by a few ways, design, mix or thumbs) 
>> > > > Differential
>>
>> > > > itself does not seem to work if the wing is POA ( well...it works 
>> > > > for
>>
>> > > > half the roll !)
>>
>> > > >> > Another black magic fix appears to be to run parallel
>>
>> > > > ailerons-but this only 'sorta' seems to fix it. I like the feel of
>>
>> > > > equal% chord ailerons however.
>>
>> > > >> >
>>
>> > > >> > I am frustrated with it-I like my planes to roll as if they
>>
>> > > > had a string up its ...........well you know!
>>
>> > > >> >
>>
>> > > >> > OK-any 'secrets' I need to know??? Very good elevator work
>>
>> > > >> > fixes it ( hence my 0-0 comment)
>>
>> > > >> >
>>
>> > > >> > Tom
>>
>> > > >> >
>>
>> > > >> >
>>
>> > > >> > --------------------------------------------------------------------
>>
>> > > >> > ----
>>
>> > > >> >
>>
>> > > >> >
>>
>> > > >> > _______________________________________________
>>
>> > > >> > NSRCA-discussion mailing list
>>
>> > > >> > NSRCA-discussion at lists.nsrca.org
>>
>> > > >> > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>
>> > > >> >
>>
>> > > >> >
>>
>> > > >> > --------------------------------------------------------------------
>>
>> > > >> > ----------
>>
>> > > >> >
>>
>> > > >> >
>>
>> > > >> > _______________________________________________
>>
>> > > >> > NSRCA-discussion mailing list
>>
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>>
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>>
>> > > >> > _______________________________________________
>>
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>>
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>>
>> > > >> >
>>
>> > > >
>>
>> > > > _______________________________________________
>>
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>>
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>>
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>>
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>> > >
>>
>> > > _______________________________________________
>>
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>> > >
>>
>> > >
>>
>> > >
>>
>> > > Chris
>>
>> > >
>>
>> > >
>>
>> > >
>>
>> > >
>>
>> > >
>>
>> > > ---------------------------------
>>
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