[NSRCA-discussion] YS Questions+more - Rolls
Matthew Frederick
mjfrederick at cox.net
Sat Mar 8 06:29:58 AKST 2008
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" <geobet at gis.net>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
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" <patterndude at tx.rr.com>
> To: <shinden1 at cox.net>; "NSRCA Mailing List"
> <nsrca-discussion at lists.nsrca.org>
> 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: <shinden1 at cox.net>
>> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
>> Cc: "Lance Van Nostrand" <patterndude at tx.rr.com>
>> 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 <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" <Tom.Koenig at actewagl.com.au>
>>>> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
>>>> 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 <drykert2 at rochester.rr.com> 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: <glmiller3 at suddenlink.net>
>>>> >> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
>>>> >> 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 <natpenton at centurytel.net> 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" <natpenton at centurytel.net>
>>>> >> >
>>>> >> > Tom
>>>> >> > It's just something that is peculiar to the Southern
>>>> > Hemisphere.
>>>> >> >
>>>> >> > Changing wing incidence will not help. Unless things are
>>>> >> > really
>>>> > screwed up <G>, 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
>>>> >> >
>>>> >> >
>>>> >> > --------------------------------------------------------------------
>>>> >> > ----------
>>>> >> >
>>>> >> >
>>>> >> > _______________________________________________
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>>>> >> >
>>>> >
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