[NSRCA-discussion] YS Questions+more - Rolls
george w. kennie
geobet at gis.net
Fri Mar 7 17:01:24 AKST 2008
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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