Throt/ Rud

[Dean Pappas]

Aha!
And I was thinking that your Vivat was one of those designs where the right thrust versus rudder trim compromise was particularly liveable.
The Excelleron has a big chin, and the shows the syndrome we have been speaking of. I'll try it on that plane. I have to go find a side-road in an industrial district to fly off.
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 David Lockhart
Sent: Thursday, January 27, 2005 10:45 PM
To: discussion at nsrca.org
Subject: Re: Throt/ Rud


Dean,
 
Surprise!!!  You do have a bit more to go on than guesses - When you flew my Vivat at BDS this past summer, it had a bit of thr/rud mix.  Still does, along with about 3 degrees of right thrust.

Dave

----- Original Message ----- 
From: Dean  <mailto:d.pappas at kodeos.com> Pappas 
To: discussion at nsrca.org 
Sent: Thursday, January 27, 2005 3:08 PM
Subject: RE: Throt/ Rud

All I have is guesses, I will go out and try this with the plane I'm fiddling with, now.
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 Bill Glaze
Sent: Thursday, January 27, 2005 1:48 PM
To: discussion at nsrca.org
Subject: Re: Throt/ Rud


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  <mailto:bob at toprudder.com> Richards 
To: 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  <http://www.cybercom.net/%7Ecopters/aero/gyro.html> precession.
 
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  <mailto:edsko at xmission.com> <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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