[NSRCA-discussion] triangulation trimming

[J N Hiller]

I am not familiar with the design and CG references would be more meaningful
to some of us as a percentage of MAC.
Please, just once.
Jim Hiller

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Budd
Engineering
Sent: Saturday, March 22, 2008 8:57 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] triangulation trimming

Vicente,

When you say your CG is 3/4" ahead of the wing tube, are you referencing
from the center of the tube, or from the front edge of the wing tube?
There's quite a difference between the two reference points on the Abbra due
to the size of the tube.

Thx, Jerry



Budd Engineering
jerry at buddengineering.com <mailto:jerry at buddengineering.com>
http://www.buddengineering.com

On Mar 22, 2008, at 6:00 AM, vicenterc at comcast.net
<mailto:vicenterc at comcast.net>  wrote:



Chris,

What is your new CG position?  I am close to 3/4" in front of the wing tube.
In my first Abbra I was around 0.6 positive and elevator position was at 0.
In my new newer Abbras, I procrastinated and didn't install the wing
adjusters.  The planes were ordered to 0.5 but they are really a little
below 0.5.  I am installing wing adjusters now to increase incidence to
around 0.6 and see what happen.  I expect that elevator position is going to
get closer to zero as I increase the incidence.  That should reduce the
amount of mixing in knife edge.

I am not sure if you are going to be able to fix the elevator mixing.  In my
old Abbra I was around 6% up both ways.  The engine was at 0.5 degree down
so probably that helped.  You need to make 100% sure that the engine is NOT
any amount up.  That could be a problem.  I prefer to put it small amount
down to cover my error.

I agree with you in regard tracking improvement moving the CG forward.  I
got the same experience.  Another point, the Abbra rudder is very powerful.
When you check the mixing in knife just use the amount that is required to
keep level fly including power setting.

Snaps. Increasing the down elevator throw probably is going to help.  I am
around 10 degrees up and 12 degrees down to get balanced feeling.

Keep telling what is your experience in the next few flights.  I still
grounded this season but I expect to start flying next weekend.  I will
report on the new conditions after increasing the incidence.

Happy holiday season to all.

--
Vicente "Vince" Bortone

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