Trim

[Bill Glaze]

I can't really recall.  But, it seems to me that it's a very fine line 
between a slight pre-load, and actually putting enough pressure on the 
servo to try to continually pull it off center.  It would require some 
experimentation.  And, getting it right in a static condition wouldn't 
necessarily mean it was correct under air loads.  But, bottom line, for 
these folks it seemed to work.
Bill Glaze

Brian Young wrote:

>What do they do put this on the opposite side of the
>surface as the control horn?
>
>--- Bill Glaze <billglaze at triad.rr.com> wrote:
>  
>
>>To prevent this very thing, and to forestall any
>>flutter, I have heard 
>>of some folks who actually pre-load the surfaces
>>with a rubber band, and 
>>then are able to completely neutralize the surface,
>>while preventing 
>>flutter.  Kind of like a snubber, which is used with
>>great success in 
>>the Boeing 727 and 757/67, with which I have some
>>experience.  Although 
>>Boeing does not use a rubber band, (not even a very
>>large, strong one) 
>>to my knowledge! :-D
>>
>>Bill Glaze
>>
>>george kennie wrote:
>>
>>    
>>
>>>I agree!
>>>
>>>"Karl G. Mueller" wrote:
>>>
>>>      
>>>
>>>>Georgie, One thing you don't want is a
>>>>        
>>>>
>>"completely neutral" set up. 
>>    
>>
>>>>Itwill be very hard on the servo gears,
>>>>        
>>>>
>>especially when it is 
>>    
>>
>>>>tooneutral in pitch.My last years Star had an
>>>>        
>>>>
>>almost neutral set up 
>>    
>>
>>>>in pitchand it started stripping the gears in the
>>>>        
>>>>
>>elevator servos.It 
>>    
>>
>>>>took me a little while to arrive at this
>>>>        
>>>>
>>conclusion since therewasn't 
>>    
>>
>>>>too much left of the plane when this happened the
>>>>        
>>>>
>>secondtime. My 
>>    
>>
>>>>suspicions were confirmed after talking to some 
>>>>"AerodynamicsExperts". Every moveable surface
>>>>        
>>>>
>>wants to hunt for a 
>>    
>>
>>>>neutral positionand if there is no opposite force
>>>>        
>>>>
>>( Trim ) to stop it 
>>    
>>
>>>>from doing thisyou will get a certain amount of
>>>>        
>>>>
>>oscillation ( flutter 
>>    
>>
>>>>). Having a minuteamount of trim offset puts a
>>>>        
>>>>
>>slight force from the 
>>    
>>
>>>>airflow over it in onedirection and will put a
>>>>        
>>>>
>>stop to any 
>>    
>>
>>>>oscillation. "Completely Neutral"is not the ideal
>>>>        
>>>>
>>condition. Karl G. 
>>    
>>
>>>>Mueller
>>>>kgamueller at rogers.com
>>>>        
>>>>
>><mailto:kgamueller at rogers.com>
>>    
>>
>>>>    ----- Original Message -----
>>>>    From: george kennie <mailto:geobet at gis.net>
>>>>    To: discussion at nsrca.org
>>>>        
>>>>
>><mailto:discussion at nsrca.org>
>>    
>>
>>>>    Sent: Friday, February 13, 2004 12:50 PM
>>>>    Subject: Re: Trim
>>>>     "Completely Neutral" is the most complex
>>>>        
>>>>
>>descriptive condition
>>    
>>
>>>>    that one can conceptualize. There are so many
>>>>        
>>>>
>>variables, that
>>    
>>
>>>>    there is only one specific set that will
>>>>        
>>>>
>>approximate the required
>>    
>>
>>>>    parameters to achieve the "voila"
>>>>        
>>>>
>>condition.Change one thing and
>>    
>>
>>>>    you no longer have "completely neutral".
>>>>    Not trying to be corrective here, just
>>>>        
>>>>
>>stating that in my
>>    
>>
>>>>    experience completely neutral is more than
>>>>        
>>>>
>>elusive, but somewhat
>>    
>>
>>>>    attainable under certain conditions.
>>>>    What I'm currently searching for is the
>>>>        
>>>>
>>correct force arrangement
>>    
>>
>>>>    that will give me a neutral airplane at the
>>>>        
>>>>
>>C.G. that I like to
>>    
>>
>>>>    fly at. I would like to fly an airplane that
>>>>        
>>>>
>>adapts to me not the
>>    
>>
>>>>    other way around. Elusive? Yeah! But
>>>>        
>>>>
>>attainable? At this point, I
>>    
>>
>>>>    think maybe!
>>>>    Georgie
>>>>     
>>>>     
>>>>
>>>>    Patternrules at aol.com wrote:
>>>>
>>>>        
>>>>
>>>>>     In a message dated 2/12/2004 11:26:21 AM US
>>>>>          
>>>>>
>>Eastern Standard
>>    
>>
>>>>>    Time, natpenton at centurytel.net writes:
>>>>>
>>>>>        For an airplane that goes to the canopy
>>>>>          
>>>>>
>>in knife-edge most
>>    
>>
>>>>>        trim charts say , after adjusting cg ,
>>>>>          
>>>>>
>>to increase the wing
>>    
>>
>>>>>        incidence . My " theory " says to
>>>>>          
>>>>>
>>decrease the wing
>>    
>>
>>>>>        incidence. What is your
>>>>>          
>>>>>
>>theory/experience ?
>>    
>>
>>>>>     What does the plane do in the down lines,
>>>>>          
>>>>>
>>if they are good you
>>    
>>
>>>>>    could just mix in a little down elevator
>>>>>          
>>>>>
>>with rudder, for the
>>    
>>
>>>>>    knife edge.  Nat, I would have thought that
>>>>>          
>>>>>
>>a guy that designed
>>    
>>
>>>>>    the Voo Doo Express that was completely
>>>>>          
>>>>>
>>neutral, would have all
>>    
>>
>>>>>    the answers LOL.  Steve Maxwell
>>>>>          
>>>>>
>
>
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