[NSRCA-discussion] YS Questions+more - Rolls
shinden1 at cox.net
shinden1 at cox.net
Thu Mar 6 19:08:17 AKST 2008
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
> >> >
> >> >
> >> > --------------------------------------------------------------------
> >> > ----------
> >> >
> >> >
> >> > _______________________________________________
> >> > 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
More information about the NSRCA-discussion
mailing list