Composite-ARF Impact question Asymmetric Fin

[ronlock at comcast.net]

Also used in control line to offset line drag.
Ron Lockhart
-------------- Original message -------------- 

"I've not seen this before in the modeling world"

The asymmetric airfoiled vertical fin is pretty common in free flight world. ed  
----- Original Message ----- 
From: Bill Glaze 
To: discussion at nsrca.org 
Sent: Monday, January 31, 2005 8:10 AM
Subject: Re: Composite-ARF Impact question


We agree that any airplane is in trim for a given set of conditions existing at that time.  As my primary instructor said: " the rudder is a trimming device."  (Perhaps a little too simplistic, but a good starting point.)
We are constantly looking for the perfect combination that requires the least work from the pilot, to achieve the most precision of results.  Probably a matter of taste, largely.
As I recall, this thread started because of one flyer noticing the asymmetrical airfoil on his new fuselage. While certainly not original in aviation, I must admit that I've not seen this before in the modeling world.  Or, probably, it's just that I've not noticed it before.  I sure hope he keeps us updated as to how it works in the real world of modeling.

Bill Glaze

Bob Richards wrote: 
Bill,

I don't think it is uncommon for full-scale planes to have offset or asymmetrical fins. However, they are designed with the right amount *for cruise*. Any other speed/power setting will change things. Since they are after the most efficiency in cruise conditions (better range), they will probably want the least amount of offset thrust as possible, and will trim the rudder/fin accordingly. If they expect the fin to be providing a constant yaw force, it would make sense to give it an asymmetrical airfoil for the most efficiency. Let the pilots deal with the other situations.

I personally think the right-thrust is the correct way to go. I can't argue with what others have said about throttle mix working for them, but I don't see how it would work. I think you will have less slipstream effect happening at full throttle in level flight than you would at full throttle in a climb. As the prop unloads with increasing airspeed, the slipstream effect should decrease.

Of course, I remember the very detailed trim instructions that came with my Great Planes Cap21. Something like: "Pull the nose up until pefectly vertical. If the plane yaws off to the left, add weight to the right wingtip". There was no mention ANYWHERE about engine thrust. Tossed that in the trash. :-)

Bob R.

Bill Glaze <billglaze at triad.rr.com> wrote:
Adam:
This may be a little bit off the mark, but just a little bit. During 
WW2, the Italian firm Fiat produced a very good series of fighters with 
exactly the characteristics you mention, that is, an asymmetrical 
fin/rudder airfoil. Seemed to work well for them; other nations handled 
the problem differently.
Bill Glaze




Bob Richards
bob at toprudder.com
http://www.toprudder.com 
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