[NSRCA-discussion] YS Questions+more - Rolls
Lance Van Nostrand
patterndude at tx.rr.com
Sat Mar 8 15:51:29 AKST 2008
Chris,
The "standard" you speak of doesn't exist. There are probably many ways to have a plane in trim but you need to start down a path that has a theoretical ideal and try to achieve it. Start with 0-0, .5-0, .5-.5 and know what an ideal plane with these setups is supposed to do in up, down, KE, upright, level flight. this also helps you select thrustline, CG starting points. Once you have a target and a contxt to interpret your fight test results then you can make proper trim corrections. This is a game of tradeoffs and tuning, but it's not random.
I've observed really good pilots in my area put down another really good pilot's trim theories, but as I said before, I would never do that. If good results are achieved then we have to respect that there is a whole trimming philosophy known to that pilot on how to trim a plane and there are at least 10 philosophies that all get the right result. I also should point out that I totally agree with Bryan's comment that everyone has their own threshold of what is "good enough". This is NOT a slam against a pilot that may not be able to feel a certain problem because he's not good enough, as some might interpret. The truth is, we all have certain trim problems that we seem to naturally overcome or are not sensitive too and others that drive us crazy. your trimming philosophy needs to address the most problematic trim issues for your personal style, sensitivity and ability.
--Lance
----- Original Message -----
From: krishlan fitzsimmons
To: NSRCA Mailing List
Sent: Saturday, March 08, 2008 2:59 PM
Subject: Re: [NSRCA-discussion] YS Questions+more - Rolls
I completely agree with this Lance.
This is what baffles me with every setup.. Wondering if I have it as good as I can. Or if maybe I should change my cg, and my incidences..
So in setup, should I just go with the standard 1/2 degree positive in the wing, then adjust cg till the ele is centered? No, that doesn't give me the best cg for my style of flying. Or do I adjust the wing incidence till it's centered? No, cuz then I will still have undesirable results in lines and knife..
This is something I have tried to say in my district. It's always pushed to practice, practice, practice. But I feel alot of us are "setup" challenged. I know I am.. We are starting to have one day practice contests here in D7 this year.. I think there are 3.. All the practice in the world doesn't make a person fly much better if he or she is fighting their setup.. It seems those that really know how to setup a plane don't want to tell their secrets.. Can't blame them. Maybe that's why they are world champions..
Chris
Lance Van Nostrand <patterndude at tx.rr.com> wrote:
Matt,
I can't disagree with anyone's final results but there has to be more going
on with other trim/alignments than just CG and incidence. All things being
in balance, i.e. the plane flies straight and level with no inputs, let's
then add 3oz as a spinner weight. Now the plane drops and requires uptrim
or increased incidence to return us to hands off level flight. Now roll the
plane inverted. That up trim or up inc is now down trim/inc. The weight on
the spinner is still there and the CG hasn't moved. The plane will not fly
hands off and its pull to the ground has to be more than before we started.
I understand the cosmetic interest in eliminating visible elv trim but at
the small deflections we are talking about, elv trim is simply changing the
angle of attack of the stab. We could eliminate the visible trim by
adjusting the stab incidence instead of the wing with no side effects.
--Lance
----- Original Message -----
From: "Matthew Frederick"
To: "NSRCA Mailing List"
Sent: Saturday, March 08, 2008 9:29 AM
Subject: Re: [NSRCA-discussion] YS Questions+more - Rolls
> Lance, George is correct that the change in incidence is so that the
> weight
> shift does not affect elevator trim. I have to disagree with his thought
> that you'll have to hold 15% down elevator when inverted. I fly airplanes
> that Bryan has trimmed all the time, and there is a moment when you roll
> inverted with his airplanes that you don't even need elevator at first.
> First time I flew his Shinden I did a slow roll and I only had to "think"
> about the elevator and rudder inputs. Makes it a lot easier to concentrate
> on the roll rate.
>
> Matt
> ----- Original Message -----
> From: "george w. kennie"
> To: "NSRCA Mailing List"
> Sent: Friday, March 07, 2008 8:01 PM
> Subject: Re: [NSRCA-discussion] YS Questions+more - Rolls
>
>
>> I'm with you Lance. You move that C.G. forward and increase the incidence
>> to
>> support the weight shift and you'd better be prepared to hold 15% down
>> elev
>> when inverted, but then what do I know?
>>
>>
>>
>>
>> ----- Original Message -----
>> From: "Lance Van Nostrand"
>> To: ; "NSRCA Mailing List"
>>
>> Sent: Friday, March 07, 2008 8:34 PM
>> Subject: Re: [NSRCA-discussion] YS Questions+more - Rolls
>>
>>
>>> Thanks Bryan. I will definitely move the cg forward a bit. Let me ask
>>> where you are going with the positive incidence suggestion.
>>> Misalignment
>>> from wing to stab sets up a situation where the positive incidence when
>>> upright is negative incidence when inverted. Of course the elevator
>>> trim
>>> is
>>> adjusted to compensate. Does this misalignment alter the roll axis in
>>> flight?
>>> --Lance
>>>
>>> ----- Original Message -----
>>> From:
>>> To: "NSRCA Mailing List"
>>> Cc: "Lance Van Nostrand"
>>> Sent: Thursday, March 06, 2008 10:07 PM
>>> Subject: Re: [NSRCA-discussion] YS Questions+more - Rolls
>>>
>>>
>>>> Lance
>>>> your airplane is tail heavy
>>>> increase your wing inc. and move the c/g forward and your problem will
>>>> go
>>>> away.
>>>> this goes for IMAC airplanes also.
>>>> we are over thinking the problem.
>>>>
>>>> design, verticle c/g has no effect on this problem
>>>> Bryan
>>>>
>>>> ---- Lance Van Nostrand 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
>>>>> >> > NSRCA-discussion at lists.nsrca.org
>>>>> >> > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>>> >> > _______________________________________________
>>>>> >> > NSRCA-discussion mailing list
>>>>> >> > NSRCA-discussion at lists.nsrca.org
>>>>> >> > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>>> >> >
>>>>> >
>>>>> > _______________________________________________
>>>>> > NSRCA-discussion mailing list
>>>>> > NSRCA-discussion at lists.nsrca.org
>>>>> > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>>> > _______________________________________________
>>>>> > NSRCA-discussion mailing list
>>>>> > NSRCA-discussion at lists.nsrca.org
>>>>> > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>>>
>>>>> _______________________________________________
>>>>> NSRCA-discussion mailing list
>>>>> NSRCA-discussion at lists.nsrca.org
>>>>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>>
>>>
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>>
>>
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