[NSRCA-discussion] Trimming question.

[Dean Pappas]

Hi Colin,
By any chance, is your plane relatively heavy, have a particularly high wing loading, propped to fly very slowly, or set up relatively nose-heavy?
The reason I ask is that back in the late eighties, I clipped the wings of one of my early Turnaround designs in order to fly faster.
This was back when we were in the middle of a wild overcorrection from flying slow and small in this country to flying fast, fast, fast! Then things started to settle down.
Actually, I clipped it twice, once from 68" span to 64" and then to 60.  I should have left the plane at 64" span. When I made the second clip, the plane developed 
almost the same symptom you described. It pulled to the canopy in the vertical down line when the elevator was trimmed for a hot day.
It also looked like it flew droopy-drawered (tail low) on hot days. I moved the CG back until the elevators looked like they were in exactly the same spot, and lived with what little was left.
There was no suitable electronic fix back then, with either a Futaba PCM 512 or a JR PCM9.
My hypothesis is that the sensitivity to air density happens when the plane requires lots of "up" trim to fly. What do the elevators look like when trimmed on a hot day?
 
later,

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: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of colin chariandy
Sent: Monday, September 11, 2006 9:53 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Trimming question.


No, I'm using the MK bellcrank.
 
If the problem was only related to the length of the pushrods, then when I re-trim the knife edge performance should return to normal. Thats not the case. The plane pushes to the bottom in the cold and is dead straight on hot days.
 
Colin.

Lance Van Nostrand <patterndude at comcast.net> wrote:

My guess is you have the deps system.  carbon fiber does not have as much shrinkage as the rest of your plane.
--Lance

----- Original Message ----- 
From: colin  <mailto:cchariandy at yahoo.ca> chariandy 
To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>  
Sent: Sunday, September 10, 2006 11:09 PM
Subject: [NSRCA-discussion] Trimming question.

I noticed recently that I need to add a bit of down trim as the air temperature drops....maybe as much as 4 beebs going from 30+ days to 15C. That upsets the knife edge trim on the aircraft. 
 
Is that normal, or do I have something set a bit marginally, like CG or wing incidence?
 
Do you guys typically have a "cold weather set-up" ?
 
Colin.
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