[NSRCA-discussion] YS Questions+more - Rolls
Lance Van Nostrand
patterndude at tx.rr.com
Fri Mar 7 16:36:31 AKST 2008
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
>> >> >
>> >> >
>> >> > --------------------------------------------------------------------
>> >> > ----
>> >> >
>> >> >
>> >> > _______________________________________________
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>> >> >
>> >> >
>> >> > --------------------------------------------------------------------
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>> >> >
>> >> >
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