Throt/ Rud

[Bill Glaze]

I hesitate to get something started here, but here goes anyway<G>:
A long conversation I had with Dick Hanson ~1996 or so, was about right 
thrust.  Dick said that "it wasn't needed" on our pattern planes; in 
fact, he had a 0-0-0 airplane with his EMC.  His feeling was that you 
needed to be on the rudder all the time anyway, so zero things out so 
that you  knew where you stood all the time.  He felt that your fingers 
could do all the tricks needed.  Countering Dick's statement,  I will 
say that every full-size propellor driven airplane I ever flew had some 
right thrust.  (Well, except for the DC-6) so the full-size designers 
didn't share Dick's philosophy.  That's O.K. though, because of 
different functions/sizes of airframe.  However, the right thrust did 
lead to some funny things.  The P-51 Mustang had a little right thrust, 
(can't remember how much) and an offset fin that put in some right 
rudder.  Reading the -1 manual stated that "when all power is removed 
for landing, some input of LEFT rudder may be required."
Interestingly, I have been able to observe some of the top fliers at the 
Nats.  Their airplanes were visibly flying perfectly smoothly straight 
and level.  But, if you observed their transmitter at the same time, you 
would notice that their fingers were always busy inputting tiny amounts 
of control.  They didn't do like some of us (ahem) do, which is try to 
trim the airplane so it's hands off, then just let it fly itself.
Anyway, I'm just interested in the different schools of thought about 
this engine offset versus trimming.  I expect to learn something from 
this thread.
Bill Glaze

Dean Pappas wrote:

> Agreed with both of you.
> What's more, in the past, when it looked like a plane required too 
> much right thrust, and would developo the warts that have been 
> described, I would reduce the right thrust until pulls took the same 
> amount of right rudder as pushes required left. My guess is that that 
> is the ideal right thrust setting from which to start fiddling with 
> the radio.
> Regards All,
>         Dean
>  
>
> Dean Pappas
> Sr. Design Engineer
> Kodeos Communications
> 111 Corporate Blvd.
> South Plainfield, N.J. 07080
> (908) 222-7817 phone
> (908) 222-2392 fax
> d.pappas at kodeos.com
>
>     -----Original Message-----
>     From: discussion-request at nsrca.org
>     [mailto:discussion-request at nsrca.org]On Behalf Of Nat Penton
>     Sent: Thursday, January 27, 2005 12:14 PM
>     To: discussion at nsrca.org
>     Subject: Re: Throt/ Rud
>
>     Bravo Bob Richards !
>
>         ----- Original Message -----
>         From: Bob Richards <mailto:bob at toprudder.com>
>         To: discussion at nsrca.org <mailto:discussion at nsrca.org>
>         Sent: Thursday, January 27, 2005 7:15 AM
>         Subject: Re: Throt/ Rud
>
>         Ed,
>          
>         I am a very firm believer (no one will convince me otherwise)
>         of exactly what you describe. Slipstream effect is the whole
>         reason we put right thrust in our engines. It has NOTHING to
>         do with torque, P-factor
>         <http://home.earthlink.net/%7Ex-plane/FAQ-Theory-PFactor.html>,
>         or gyroscopic precession
>         <http://www.cybercom.net/%7Ecopters/aero/gyro.html>.
>          
>         The issue of transitioning from vertical to horizontal (either
>         to inverted or upright) is a gyroscopic precession issue. The
>         best way to counter that is to use lighter weight props
>         turning at lower rpm -- less spinning mass and less gyroscopic
>         effect.
>          
>         P-factor only exists at high angle of attacks, which does not
>         happen in a vertical climb.
>          
>         Torque tries to roll the plane, and some schools of thought
>         are that, to counter the torque-induced roll, the left wing
>         has to lift more than the right, causing more induced drag on
>         the left. While this may be true for a lot of planes while
>         taking off, this does not apply to pattern planes in a
>         vertical climb since both wing panels would be fighting the
>         torque equally.
>          
>         Gyroscopic precession only occurs when the airplane is moving
>         around its pitch axis, as when pulling or pushing a corner. It
>         is most noticeable when the airplane is slow, since there is
>         less aerodynamic stabilizing force available from the
>         rudder/fin.  IMHO, no throttle-rudder mix is going to correct
>         this. It might be possible to mix elevator to rudder, and
>         enable/disable the mix based on throttle position.
>          
>         When I flew a Cap21 in pattern, I had to use left rudder when
>         pulling an inside corner at the top of square loops. I had to
>         use a TON of right rudder when pushing a corner, and this was
>         with about 5 degrees of right thrust.
>          
>         IMHO, learn to do it with your thumbs. Practice enough and it
>         will become automatic. Just my 2CW.
>          
>         Bob R.
>
>
>         Edward Skorepa <edsko at xmission.com> wrote:
>
>             I'm confused too. I know, I know I shouldn't argue with
>             someone like chip but I believe the main reason we're
>             putting right thrust is an asymmetric vertical fin. On
>             most conventional airplanes the area above thrust line is
>             much greater then area below. So, the spiraling slip
>             stream  will hit the top portion of the vertical fin from
>             the left pushing tail to the right thus right thrust. When
>             inverted, the spiraling slip stream will hit vertical fin
>             from the right because fin is now on the opposite side
>             and  pushes tail to the left. To straighten the flight
>             path, we need now the left thrust which is already there.
>             During inverted push ups, why do we need to use left
>             rudder? The spiraling slip stream misses completely
>             vertical fin and the right (left when inverted) thrust is
>             causing airplane to yaw left. If you have a big gasser,
>             turn on smoke, do inverted push up and watch where the
>             smoke goes. However, Chip's approach of fixing ! the
>             inverted push ups problem is quite interesting and I'll
>             try it on my new bird I'm working on right now.
>             ed
>
>         ------------------------------------------------------------------------
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