Trim Question--Long

[Del K. Rykert]

Dan..
    Reason I asked about left & right, back in the Dirty Birdy hay days it
was felt that a little reflex in aileron often would cause one aileron to
have more effect than the otherin flight with small inputs. Taking reflex
out or reducing it often eliminated that condition.

                         del
               NSRCA - 473

----- Original Message ----- 
From: "Dan Curtis" <warrior523 at mchsi.com>
To: <discussion at nsrca.org>
Sent: Sunday, April 18, 2004 7:39 PM
Subject: Re: Trim Question--Long


> Thanks for your theory Troy and I will keep it in mind.  I am using the
> 8411SA on the rudder and the geometry is good.  Rudder trim is very good
> (especially for me).  I actually started to leave the counter balance off
of
> this plane and am not real sure why I went ahead and put it on.  It could
> very well be gone by this weekend.  The C/G is forward of the design
> recomendations.
>
> It was asked if the plane did this when rolling easily to the left as well
> as the right.  I am sure I tried it, surely I tried it, I think I tried
it,
> well I should have tried it but alas I can't remember doing the hands off
> test to the left.  I will do that Tuesday, next time out with the critter.
>
> Keep any ideas coming fellows, I think we are getting somewhere.
>
> Thanks
>
> Dan<------one in a thousand :)
> ----- Original Message ----- 
> From: "Troy Newman" <troy_newman at msn.com>
> To: <discussion at nsrca.org>
> Sent: April 18, 2004 5:40 PM
> Subject: Re: Trim Question--Long
>
>
> > Dan,
> >  since the plane has a counter balance.......I would say I have seen
some
> > funny things happen with the counter balanced rudders that so many
planes
> > have today.
> >
> > Not totally sure why its happening but probably do in some part to
control
> > Snatch. This happens when the control surface tab grabs the air and
> reaches
> > a point where it overrides the flight forces normal on the surface. What
> > happens is when you reach a certain point in rudder deflection the tab
> gabs
> > and all of a sudden the load on the servo reverses from pulling the left
> > cable to hold left rudder...to the result of the tab...trying to get
more
> > left rudder than commanded. The servo is then driving right to hold the
> > commanded position left rudder. Not sure if I'm explaining it correctly
or
> > not....
> >
> > Where I have seen this happen most is rolling from inverted to a knife
or
> an
> > 8th point position.  The coupling in the model is mixed perfectly for
> knife
> > edge flight even to the point of extreme rudder throws and knife edge
> > loops....but when the model is rolling in certain orientations the
> coupling
> > changes. I have seen this tendency with almost all counter balanced
rudder
> > models I have flown. The counter balance works very well at making the
> > rudder servo work less....However in these certain conditions its
putting
> > bigger loads on the servo in the snatch condition...
> >
> >
> > My theory on this as rolling from inverted the rudder and specifically
the
> > tab is in clean air below the model....it digs in and has some more
> > effective responses than we are used to. Since you are flying in a
normal
> > almost no rudder or no rudder situation perhaps the tab is catching in
the
> > clean air....How is your rudder trim? Is the rudder straight to the
> > fuse....not the tab but the rudder...Look from the belly of the model
> while
> > inverted back at the rudder and see if its tracking straight...If it is
> here
> > How is the tab centered on the fin....Basically is the rudder straight,
> and
> > tab sanded correctly to track straight... Next rudder cable tension?
> Tighter
> > cables may help.....Next geometry on your pull pull system? Can you get
> more
> > leverage for the servo.....Sometimes crossing the cables can do this.
> > Sometimes not.
> >
> > Solutions I have found work.....Better rudder servo. If you are not
using
> an
> > 8411SA this is what you need...I even know of some very loyal Futaba
> flyers
> > that found the 8411SA to be a solution to their rudder problems. Not
> bashing
> > any servos here just stating the facts I have experienced. I minimized
> this
> > on my Smaragd with a rudder tab using the 8411SA....then I tested an
8611
> on
> > the rudder and the issue went away...This proved to me it was servo
power
> > and precision related.
> >
> > Better geometry on the linkage. Final thing is the knife and put the
> rudder
> > tab on top of the fin with some clear tape and see if it solves it. We
> have
> > found that it can be minimized using better servo setups...and
eliminated
> > with the removal of the tab. This is one really good reason to have a
> > removable rudder...You can just take the rudder off...remove the tab and
> > then attach it temp style with tape to the fin and fly it....
> >
> > Another solution to minimize the problem is CG....Change the way the
model
> > is flying....Maybe add some nose weight and see if the problem minimizes
> And
> > I don't mean a 1/2 oz....Like 4-6-8ozs and see what happens. As the guys
> on
> > this list gasp for air....I'll say that big CG changes can tell you a
ton
> > about the way the model is flying. If you make a huge shift forward like
> > 4ozs on the nose. Most models will tend to chage the little settle down
> > things like you are dealing with. If the 4ozs helps a littl...then go
> > another 4ozs. I hate to say move the CG back as I feel many pilots fly
> their
> > CG too far aft as it is......
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