[NSRCA-discussion] Elevator setup with anhedral stabs

[Stuart Chale]

With a flat stab and 2 servos and the 14MZ I was able to add a point mix
between the two elevator channels.  I little added or reduced throw (.5%)
could be added at any point along the stick travel to even out
inconsistencies of the two servos.  Any mismatch of the two halves is
accentuated by the length of the carbon rods.  It wasn't much, but there was
a difference.  
With the rods meeting in the center it was easy to adjust along the entire
servo travel.  I may try the same thing measuring off the table as you
suggested with a square if I can stop both servos in the same place with the
servo test or hold function.

Thanks,
Stuart

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Woodward, Jim
Sent: Friday, September 21, 2007 9:45 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Elevator setup with anhedral stabs

HI Stuart,

I saw your RCU post.  I use 12" long triangle stock pointers clamped
onto the elevators to see if they are tracking or not.  I like your idea
of using the 1/8" CF rods though too.  

The anhedral stab is not as easy to line up.  You might be left to
positioning the fuselage on a table with the tail in the air and solidly
hold down the plane (maybe some masking tape to make sure the fuse isn't
going to move once you put it in place on some hard resting points, off
the foam tires too).  

Position your pointers on the elevators and move them to full stop, then
take a straight down measurement to the table.  Between a measurement
and the "eye-ball" I bet you will be VERY close - certainly within the
1/2 turn of adjustability on a clevis for up/down adjustment.  You can
more than likely get within the 1/2 turn precision just with your
eyeball if the plane is solidly position on the table.  

Speaking of the 1/2 turn of precision a clevis offers, sometimes I
really just want to see the tracking perfect within the normal flying
rate of 10'ish degrees of throw.  If it is good through the 10 degrees
up and down, I'm not so critical of what happens at 18 degrees of throw.
If the geometry of the servos and pushrod, control surface horn, or any
other little gremlin is not equal to the other side, you can't really
get perfectly matched up and down throw through the whole travel.  What
really sucks is if you have DEPS system in stalled, and say the up
travel is equal, but the down travel is not equal on one 1/2.  It can
happen.

What would be interesting to see is a blown-up diagram of this.
Supposing the surface is hinged perfectly, the control horn moves in an
arc equal to its length.  What if you bend the control horn aft thus
moving the clevis attach point slightly aft, lengthen the clevis to keep
the neutral point the same, then see if it "changes" how much the
surface moves up and down in one direction.  Since the control horn
moves in an arc, this would (could??) mean that more of the motion is
going vertical relative to the other side.

Thanks,
Jim W.





 
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-----Original Message-----

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Stuart
Chale
Sent: Friday, September 21, 2007 9:24 AM
To: 'NSRCA Mailing List'
Subject: Re: [NSRCA-discussion] Elevator setup with anhedral stabs

I tried this question on RCU and didn't get any great answers so I
thought I
would try here.

Does anyone have a good method for comparing the throw of both elevator
halves on anhedral stabs?  With a regular stab I use a 15 inch piece of
1/8
carbon fiber rod on each elevator meeting behind the rudder and compare
their track with movement of the elevator stick.  This is much more
accurate
to me, than clip on throw meters or ruler measurements.  With anhedral
stabs
the two rods will separate as you give up elevator and come together and
cross with down elevator.  I guess you can measure the height of the end
of
the rod from the table at different positions but does anyone have a
better
method?

Thanks,
Stuart


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